Immune response induced by a Streptococcus suis multi-serotype autogenous vaccine used in sows to protect post-weaned piglets

Streptococcus suis is a bacterial pathogen that causes important economic losses to the swine industry worldwide. Since there are no current commercial vaccines, the use of autogenous vaccines applied to gilts/sows to enhance transfer of passive immunity is an attractive alternative to protect weaned piglets. However, there is no universal standardization in the production of autogenous vaccines and the vaccine formulation may be highly different among licenced manufacturing laboratories. In the present study, an autogenous vaccine that included S. suis serotypes 2, 1/2, 5, 7 and 14 was prepared by a licensed laboratory and administrated to gilts using a three-dose program prior to farrowing. The antibody response in gilts as well as the passive transfer of antibodies to piglets was then evaluated. In divergence with previously published data with an autogenous vaccine produced by a different company, the increased response seen in gilts was sufficient to improve maternal antibody transfer to piglets up to 5 weeks of age. However, piglets would still remain susceptible to S. suis disease which often appears during the second part of the nursery period. Vaccination did not affect the shedding of S. suis (as well as that of the specific S. suis serotypes included in the vaccine) by either gilts or piglets. Although all antibiotic treatments were absent during the trial, the clinical protective effect of the vaccination program with the autogenous vaccine could not be evaluated, since limited S. suis cases were present during the trial, confirming the need for a complete evaluation of the clinical protection that must include laboratory confirmation of the aetiological agent involved in the presence of S. suis-associated clinical signs. Further studies to evaluate the usefulness of gilt/sow vaccination with autogenous vaccines to protect nursery piglets should be done.

Lipoteichoic acids influence cell shape and bacterial division of Streptococcus suis serotype 2, but play a limited role in the pathogenesis of the infection

Streptococcus suis serotype 2 is a major swine pathogen and a zoonotic agent, causing meningitis in both swine and humans, responsible for substantial economic losses to the swine industry worldwide. The pathogenesis of infection and the role of bacterial cell wall components in virulence have not been fully elucidated. Lipoproteins, peptidoglycan, as well as lipoteichoic acids (LTA) have all been proposed to contribute to virulence. In the present study, the role of the LTA in the pathogenesis of the infection was evaluated through the characterisation of a mutant of the S. suis serotype 2 strain P1/7 lacking the LtaS enzyme, which mediates the polymerization of the LTA poly-glycerolphosphate chain. The ltaS mutant was confirmed to completely lack LTA and displayed significant morphological defects. Although the bacterial growth of this mutant was not affected, further results showed that LTA is involved in maintaining S. suis bacterial fitness. However, its role in the pathogenesis of the infection appears limited. Indeed, LTA presence reduces self-agglutination, biofilm formation and even dendritic cell activation, which are important aspects of the pathogenesis of the infection caused by S. suis. In addition, it does not seem to play a critical role in virulence using a systemic mouse model of infection.

Encapsulated Streptococcus suis impairs optimal neutrophil functions which are not rescued by priming with colony-stimulating factors

The porcine pathogen and zoonotic agent Streptococcus suis induces an exacerbated inflammation in the infected hosts that leads to sepsis, meningitis, and sudden death. Several virulence factors were described for S. suis of which the capsular polysaccharide (CPS) conceals it from the immune system, and the suilysin exhibits cytotoxic activity. Although neutrophils are recruited rapidly upon S. suis infection, their microbicidal functions appear to be poorly activated against the bacteria. However, during disease, the inflammatory environment could promote neutrophil activation as mediators such as the granulocyte colony-stimulating factor granulocyte (G-CSF) and the granulocyte-macrophages colony-stimulating factor (GM-CSF) prime neutrophils and enhance their responsiveness to bacterial detection. Thus, we hypothesized that CPS and suilysin prevent an efficient activation of neutrophils by S. suis, but that G-CSF and GM-CSF rescue neutrophil activation, leading to S. suis elimination. We evaluated the functions of porcine neutrophils in vitro in response to S. suis and investigated the role of the CPS and suilysin on cell activation using isogenic mutants of the bacteria. We also studied the influence of G-CSF and GM-CSF on neutrophil response to S. suis by priming the cells with recombinant proteins. Our study confirmed that CPS prevents S. suis-induced activation of most neutrophil functions but participates in the release of neutrophil-extracellular traps (NETs). Priming with G-CSF did not influence cell activation, but GM-CSF strongly promote IL-8 release, indicating its involvement in immunomodulation. However, priming did not enhance microbicidal functions. Studying the interaction between S. suis and neutrophils-first responders in host defense-remains fundamental to understand the immunopathogenesis of the infection and to develop therapeutical strategies related to neutrophils' defense against this bacterium.

Unmutated but T cell dependent IgM antibodies targeting Streptococcus suis play an essential role in bacterial clearance

Streptococcus suis serotype 2 is an important encapsulated bacterial swine pathogen and zoonotic agent for which no effective vaccine exists. The interaction with B cells and the humoral response against S. suis are poorly understood despite their likely relevance for a potential vaccine. We evaluated germinal center (GC) B cell kinetics, as well as the production and role of S. suis-specific antibodies following infections in a mouse model. We found that mice infected with S. suis developed GC that peaked 13-21 days post-infection. GC further increased and persisted upon periodic reinfection that mimics real life conditions in swine farms. Anti-S. suis IgM and several IgG subclasses were produced, but antibodies against the S. suis capsular polysaccharide (CPS) were largely IgM. Interestingly, depletion of total IgG from the wild-type mice sera had no effect on bacterial killing by opsonophagocytosis in vitro. Somatic hypermutation and isotype switching were dispensable for controlling the infection or anti-CPS IgM production. However, T cell-deficient (Tcrb-/-) mice were unable to control bacteremia, produce optimal anti-CPS IgM titers, or elicit antibodies with opsonophagocytic activity. SAP deficiency, which prevents GC formation but not extrafollicular B cell responses, ablated anti S. suis-IgG production but maintained IgM production and eliminated the infection. In contrast, B cell deficient mice were unable to control bacteremia. Collectively, our results indicate that the antibody response plays a large role in immunity against S. suis, with GC-independent but T cell-dependent germline IgM being the major effective antibody specificities. Our results further highlight the importance IgM, and potentially anti-CPS antibodies, in clearing S. suis infections and provide insight for future development of S. suis vaccines.

Study of the Role of Lipoprotein Maturation Enzymes in the Pathogenesis of the Infection Caused by the Streptococcus suis Serotype 2 Sequence Type 25 North American Prototype Strain

Streptococcus suis serotype 2 is an important swine bacterial pathogen causing sudden death, septic shock, and meningitis. However, serotype 2 strains are phenotypically and genotypically heterogeneous and composed of a multitude of sequence types (STs) whose distributions greatly vary worldwide. It has been previously shown that the lipoprotein (LPP) maturation enzymes diacylglyceryl transferase (Lgt) and signal peptidase (Lsp) significantly modulate the inflammatory host response and play a differential role in virulence depending on the genetic background of the strain. Differently from Eurasian ST1/ST7 strains, the capsular polysaccharide of a North American S. suis serotype 2 ST25 representative strain only partially masks sub-capsular domains and bacterial wall components. Thus, our hypothesis is that since LPPs would be more surface exposed in ST25 strains than in their ST1 or ST7 counterparts, the maturation enzymes would play a more important role in the pathogenesis of the infection caused by the North American strain. Using isogenic Δlgt and Δlsp mutants derived from the wild-type ST25 strain, our studies suggest that these enzymes do not seem to play a role in the interaction between S. suis and epithelial and endothelial cells, regardless of the genetics background of the strain used. However, a role in the formation of biofilms (also independently of the STs) has been demonstrated. Moreover, the involvement of LPP dendritic cell activation in vitro seems to be somehow more pronounced with the ST25 strain. Finally, the Lgt enzyme seems to play a more important role in the virulence of the ST25 strain. Although some differences between STs could be observed, our original hypothesis that LPPs would be significantly more important in ST25 strains due to a better bacterial surface exposition could not be confirmed.

Metabolic insights and background from naturally affected pigs during Streptococcus suis outbreaks

Streptococcus suis (S. suis) is an endemic zoonotic pathogen still lacking adequate prevention in pigs. The present case study looked back to the occurrence and consequences of S. suis outbreaks in our swine research facilities in search of new metabolic and physiological insight. From a series of outbreaks, a dataset was created including 56 pigs sampled during disease detection based on clinical signs. Pigs suspected with S. suis infection were defined as diseased (n = 28) and included pigs defined as neurologically diseased (n = 20) when severe neurological signs (central nervous system dysfunctions, i.e., opisthotonos, ataxia, and generalized tremor) were observed. Another set of 28 pigs included respective pen mates from each case and were defined as control. Representative deaths were confirmed to be caused by S. suis. Tonsillar swabs were collected and analyzed by quantitative polymerase chain reaction (qPCR) for total bacteria, total S. suis, and S. suis serotypes (SS) 2 (and/or 1/2) and 9. Blood and sera were analyzed to quantify blood gases, minerals, and S. suis reactive immunoglobulins against current isolates. Data collected included litter sibling associations, birth and weaning body weight (BW), and average daily gain (ADG) 7 d after the disease detection. In general, the disease increased pH, sO2 and the incidence of alkalosis, but reduced pCO2, glucose, Ca, P, Mg, K, and Na in blood/serum compared to control. The SS2 (and/or SS1/2) prevalence was significantly (P < 0.05) increased in neurologically diseased pigs and its relative abundance tended (P < 0.10) to increase in tonsils. In contrast, the relative abundance of total S. suis was lower (P > 0.05) in diseased pigs than control pigs. Levels of S. suis reactive IgG2 were lower, but IgM were higher (P < 0.03) in neurologically affected pigs compared to control. Furthermore, there was an increased proportion of sibling pigs that were diseased compared to control. In conclusion, our results evidence that naturally affected pigs were associated to average performing pigs without any predisease trait to highlight but a sow/litter effect. Besides, neurologically affected pigs had increased S. suis (SS2 and/or 1/2) prevalence and relative abundance, a respiratory alkalosis profile, and mineral loss.

Evaluation of the Immunoprotective Capacity of Five Vaccine Candidate Proteins against Avian Necrotic Enteritis and Impact on the Caecal Microbiota of Vaccinated Birds

Avian necrotic enteritis is an enteric disease of broiler chickens caused by certain pathogenic strains of Clostridium perfringens in combination with predisposing factors. A vaccine offering complete protection against the disease has not yet been commercialized. In a previous study, we produced five recombinant proteins predicted to be surface-exposed and unique to necrotic enteritis-causing C. perfringens and the immunogenicity of these potential vaccine candidates was assessed in broiler chickens. In the current work, the relative contribution of the antibodies raised by these putative antigens to protect broiler chickens was evaluated using an experimental necrotic enteritis induction model. Additionally, the link between the immune response elicited and the gut microbiota profiles in immunized birds subjected to infection with virulent C. perfringens was studied. The ELISA results showed that the IgY antibody titers in vaccinated birds on days 21 and 33 were significantly higher than those on days 7 and 14 and those in birds receiving the adjuvant alone, while the relative contribution of the specific immunity attributed to these antibodies could not be precisely determined using this experimental necrotic enteritis induction model. In addition, 16S rRNA gene amplicon sequencing showed that immunization of birds with recombinant proteins had a low impact on the chicken caecal microbiota.

Postnatal genetic and neurodevelopmental assessment in infants born at term with severely low birth weight of non-placental origin

OBJECTIVE

To determine the frequency of genetic syndromes and childhood neurodevelopmental impairment in non-malformed infants born at term with severely low birth weight and no evidence of placental insufficiency.

METHODS

This case series was constructed from the data of infants delivered at term between 2013 and 2018 with severely low birth weight, defined as birth weight more than 2.5 SD below the mean, with normal maternal and fetal Doppler (umbilical artery, fetal middle cerebral artery, cerebroplacental ratio and uterine artery) and no maternal hypertensive disorder during pregnancy or fetal structural anomaly on prenatal ultrasound examination. Clinical exome sequencing and copy number variation (CNV) analysis were performed using DNA extracted from the children's saliva. Cognitive and psychomotor development was evaluated using the Bayley Scales of Infant and Toddler Development, 3rd edition or the Wechsler Intelligence Scale for Children, 5th edition tests, according to the child's age at testing.

RESULTS

Among the 36 405 infants born within the study period, 274 (0.75%) had a birth weight below -2.5 SD, of whom 98 met the inclusion criteria. Among the 63 families contacted, seven (11%) reported a postnatal diagnosis of a genetic syndrome and a further 18 consented to participate in the study. Median gestational age at delivery was 38.0 (interquartile range (IQR), 37.3-38.5) weeks and median birth weight was 2020 (IQR, 1908-2248) g. All 18 children showed a normal result on clinical exome sequencing and CNV analysis, but six (33%) obtained a low score on neurodevelopmental testing.

CONCLUSION

Non-malformed severely small term infants with no clinical or Doppler signs of placental insufficiency present a high rate of genetic syndromes and neurodevelopmental impairment during childhood. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Genomic characterization and virulence of Streptococcus suis serotype 4 clonal complex 94 recovered from human and swine samples

Streptococcus suis is a zoonotic pathogen that causes invasive infections in humans and pigs. Herein, we performed genomic analysis of seven S. suis serotype 4 strains belonging to clonal complex (CC) 94 that were recovered from a human patient or from diseased and clinically healthy pigs. Genomic exploration and comparisons, as well as in vitro cytotoxicity tests, indicated that S. suis CC94 serotype 4 strains are potentially virulent. Genomic analysis revealed that all seven strains clustered within minimum core genome group 3 (MCG-3) and had a high number of virulence-associated genes similar to those of virulent serotype 2 strains. Cytotoxicity assays showed that both the human lung adenocarcinoma cell line and HeLa cells rapidly lost viability following incubation for 4 h with the strains at a concentration of 106 bacterial cells. The human serotype 4 strain (ID36054) decreased cell viability profoundly and similarly to the control serotype 2 strain P1/7. In addition, strain ST1689 (ID34572), isolated from a clinically healthy pig, presented similar behaviour in an adenocarcinoma cell line and HeLa cells. The antimicrobial resistance genes tet(O) and ermB that confer resistance to tetracyclines, macrolides, and lincosamides were commonly found in the strains. However, aminoglycoside and streptothricin resistance genes were found only in certain strains in this study. Our results indicate that S. suis CC94 serotype 4 strains are potentially pathogenic and virulent and should be monitored.

Streptococcus suis surface-antigen recognition by antibodies and bacterial elimination is influenced by capsular polysaccharide structure

Streptococcus suis is an encapsulated bacterium causing severe diseases in swine. Here, we compared the protective properties of the capsular polysaccharide (CPS) of different S. suis serotypes by using serotype-switched mutants in a mouse model of infection. CPS structure influenced bacterial survival in mice, antibody binding, and antibody-mediated bacterial killing. The CPS of serotypes 3, 4 and 14 allowed more antibody binding and bacterial elimination than the CPS of serotypes 2, 7 and 9. Results suggest that the different CPS structures of S. suis provide varying levels of protection by influencing antigen availability and elimination by the host immune system.

Interactions of Mycoplasma hyopneumoniae and/or Mycoplasma hyorhinis with Streptococcus suis Serotype 2 Using In Vitro Co-Infection Models with Swine Cells

Bacterial and/or viral co-infections are very common in swine production and cause severe economic losses. Mycoplasma hyopneumoniae, Mycoplasma hyorhinis and Streptococcus suis are pathogenic bacteria that may be found simultaneously in the respiratory tracts of pigs. In the present study, the interactions of S. suis with epithelial and phagocytic cells in the presence or absence of a pre-infection with M. hyopneumoniae and/or M. hyorhinis were studied. Results showed relatively limited interactions between these pathogens. A previous infection with one or both mycoplasmas did not influence the adhesion or invasion properties of S. suis in epithelial cells or its resistance to phagocytosis (including intracellular survival) by macrophages and dendritic cells. The most important effect observed during the co-infection was a clear increment in toxicity for the cells. An increase in the relative expression of the pro-inflammatory cytokines IL-6 and CXCL8 was also observed; however, this was the consequence of an additive effect due to the presence of different pathogens rather than a synergic effect. It may be hypothesized that if one or both mycoplasmas are present along with S. suis in the lower respiratory tract at the same time, then increased damage to epithelial cells and phagocytes, as well as an increased release of pro-inflammatory cytokines, may eventually enhance the invasive properties of S. suis. However, more studies should be carried out to confirm this hypothesis.

Immunization of broiler chickens with five newly identified surface-exposed proteins unique to Clostridium perfringens causing necrotic enteritis

Since the ban or reduction on the use of antibiotic growth promoters (AGPs) in commercial broiler chickens in many countries, avian necrotic enteritis (NE) caused by Clostridium perfringens has re-emerged as one of the biggest threats for the poultry industry worldwide. While the toolbox for controlling NE in the absence of antibiotics consists of a limited number of alternatives for which the overall effectiveness has yet proven to be suboptimal, an effective vaccine would represent the best control strategy for this often-deadly disease. Using a comparative and subtractive reverse vaccinology approach, we previously identified 14 putative antigenic proteins unique to NE-causing strains of C. perfringens. In the current work, the in silico findings were confirmed by PCR and sequencing, and five vaccine candidate proteins were produced and purified subsequently. Among them, two candidates were hypothetical proteins, two candidates were prepilin proteins which are predicted to form the subunits of a pilus structure, and one candidate was a non-heme iron protein. Western blotting and ELISA results showed that immunization of broiler chickens with five of these proteins raised antibodies which can specifically recognize both the recombinant and native forms of the protein in pathogenic C. perfringens.

Laminin-binding protein of Streptococcus suis serotype 2 influences zinc acquisition and cytokine responses

Streptococcus suis serotype 2 is an important bacterial pathogen of swine, responsible for substantial economic losses to the swine industry worldwide. The knowledge on the pathogenesis of the infection caused by S. suis is still poorly known. It has been previously described that S. suis possesses at least one lipoprotein with double laminin and zinc (Zn)-binding properties, which was described in the literature as either laminin-binding protein (Lmb, as in the current study), lipoprotein 103, CDS 0330 or AdcAII. In the present study, the role of the Lmb in the pathogenesis of the infection caused by S. suis serotype 2 was dissected. Using isogenic mutants, results showed that Lmb does not play an important role in the laminin-binding activity of S. suis, even when clearly exposed at the bacterial surface. In addition, the presence of this lipoprotein does not influence bacterial adhesion to and invasion of porcine respiratory epithelial and brain endothelial cells and it does not increase the susceptibility of S. suis to phagocytosis. On the other hand, the Lmb was shown to play an important role as cytokine activator when tested in vitro with dendritic cells. Finally, this lipoprotein plays a critical role in Zn acquisition from the host environment allowing bacteria to grow in vivo. The significant lower virulence of the Lmb defective mutant may be related to a combination of a lower bacterial survival due to the incapacity to acquire Zn from their surrounding milieu and a reduced cytokine activation.

Sociocultural Factors Influencing Human Streptococcus suis Disease in Southeast Asia

The public health systems of Southeast Asian countries are financially challenged by a comparatively higher incidence of human S. suis infections than other geographical areas. Efforts to improve practices in production settings, including improved meat inspection regulations, prevention of the slaughtering of non-healthy pigs, and enhanced hygiene practices at processing facilities, along with improvements in the pork supply chain, all appear promising for reducing food cross-contamination with S. suis. However, opportunities for intervention at the societal level are also needed to effect changes, as population behaviors such as the consumption of raw pork, blood, and offal products are important contributors to the increased incidence of human S. suis disease in Southeast Asia. A plethora of factors are associated with the consumption of these high-risk dishes, including traditional culture and knowledge, shared beliefs, socio-economic level, and personal attitudes associated with gender and/or marital status. Education and intervention in behavioral attitudes that are sensible to cultural practices and traditions may provide additional means to reduce the burden of S. suis human disease in Southeast Asia.

Protective Effects of Interleukin-1 Blockade on Group B Streptococcus-Induced Chorioamnionitis and Subsequent Neurobehavioral Impairments of the Offspring

Group B Streptococcus (GBS) is one of the most common bacteria isolated in human chorioamnionitis. Placental infection due to GBS is a major risk factor for fetal organ injuries, preterm birth, perinatal morbidity and mortality, and life-long multiorgan morbidities. Preclinical and clinical studies have shown that GBS-induced infection drives polymorphonuclear (PMN) cell infiltration within the placenta, the hallmark of human chorioamnionitis. In preclinical and clinical studies, the upregulation of interleukin(IL)-1β in the placenta and maternal/fetal blood was associated with a high risk of neurodevelopmental impairments in the progeny. We hypothesized that targeted IL-1 blockade administered to the dam alleviates GBS-induced chorioamnionitis and the downstream fetal inflammatory response syndrome (FIRS). IL-1 receptor antagonist (IL-1Ra) improved the gestational weight gain of GBS-infected dams and did not worsen the infectious manifestations. IL-1Ra reduced the IL-1β titer in the maternal sera of GBS-infected dams. IL-1Ra decreased the levels of IL-1β, IL-6, chemokine (C-X-C motif) ligand 1 (CXCL1), and polymorphonuclear (PMN) infiltration in GBS-infected placenta. IL-1Ra treatment reduced the IL-1β titer in the fetal sera of GBS-exposed fetuses. IL-1 blockade also alleviated GBS-induced FIRS and subsequent neurobehavioral impairments of the offspring without worsening the outcome of GBS infection. Altogether, these results showed that IL-1 plays a key role in the physiopathology of live GBS-induced chorioamnionitis and consequent neurobehavioral impairments.

Piglet innate immune response to Streptococcus suis colonization is modulated by the virulence of the strain

Streptococcus suis is a zoonotic pathogen of swine involved in arthritis, polyserositis, and meningitis. Colonization of piglets by S. suis is very common and occurs early in life. The clinical outcome of infection is influenced by the virulence of the S. suis strains and the immunity of the animals. Here, the role of innate immunity was studied in cesarean-derived colostrum-deprived piglets inoculated intranasally with either virulent S. suis strain 10 (S10) or non-virulent S. suis strain T15. Colonization of the inoculated piglets was confirmed at the end of the study by PCR and immunohistochemistry. Fever (≥40.5 °C) was more prevalent in piglets inoculated with S10 compared to T15 at 4 h after inoculation. During the 3 days of monitoring, no other major clinical signs were detected. Accordingly, only small changes in transcription of genes associated with the antibacterial innate immune response were observed at systemic sites, with S10 inducing an earlier response than T15 in blood. Local inflammatory response to the inoculation, evaluated by transcriptional analysis of selected genes in nasal swabs, was more sustained in piglets inoculated with the virulent S10, as demonstrated by transcription of inflammation-related genes, such as IL1B, IL1A, and IRF7. In contrast, most of the gene expression changes in trachea, lungs, and associated lymph nodes were observed in response to the non-virulent T15 strain. Thus, S. suis colonization in the absence of systemic infection induces an innate immune response in piglets that appears to be related to the virulence potential of the colonizing strain.

Engineering Antigens to Assemble into Polymer Particle Vaccines for Prevention of Streptococcus suis Infection

Streptococcus suis is a zoonotic pathogen affecting pigs and humans. This bacterium causes severe economic losses in the swine industry and poses a serious threat to public health and food safety. There is no effective commercial vaccine available for pigs or humans. In this study, we applied the biopolymer particle (BP) vaccine technology to incorporate seven conserved S. suis antigens (38 kDa protein (38), enolase (Enol), SSU1915, SSU1355, SSU0185, SSU1215, and SSU1773 (SSU1 and SSU2)). Two combinations of these antigens (38 and Enol; all SSU antigens designated as SSU1 and SSU2) were engineered to mediate production of BPs coated with either antigens 38 and Enol or SSU1 and SSU2 inside recombinant Escherichia coli. The isolated and purified empty BPs, 38-BP-Enol and SSU1-BP-SSU2, showed size ranges of 312-428 nm and 292-344 nm with and without the QuilA® adjuvant, respectively, and all showed a negative surface charge. Further characterization of purified BPs confirmed the presence of the expected antigen-comprising fusion proteins as assessed by tryptic peptide fingerprinting analysis using quadrupole time-of-flight mass spectrometry and immunoblotting. Vaccination with 38-BP-Enol and SSU1-BP-SSU2 formulated with and without QuilA® adjuvant induced significant antigen-specific humoral immune responses in mice. Antigen-coated BPs induced significant and specific Ig (IgM + IgG) and IgG immune responses (1.0 × 106-1.0 × 107) when compared with mice vaccinated with empty BPs. Functionality of the immune response was confirmed in challenge experiments using an acute murine S. suis infection model, which showed 100% survival of the 38-BP-Enol and SSU1-BP-SSU2 vaccinated mice compared to 70% survival when vaccinated with empty BPs. Overall, our data suggest that S. suis antigen-coated BPs could be developed into particulate vaccines that induce protective immunity against S. suis infections.

Role of Maturation of Lipoproteins in the Pathogenesis of the Infection Caused by Streptococcus suis Serotype 2

Streptococcus suis serotype 2 is an important porcine bacterial pathogen associated with multiple pathologies in piglets. Bacterial lipoproteins (LPPs) have been described as playing important roles in the pathogenesis of the infection of other Gram-positive bacteria as adhesins, pro-inflammatory cell activators and/or virulence factors. In the current study, we aimed to evaluate the role of the prolipoprotein diacylglyceryl transferase (Lgt) and lipoprotein signal peptidase (Lsp) enzymes, which are responsible for LPP maturation, on the pathogenesis of the infection caused by two different sequence types (STs) of S. suis serotype 2 strains (virulent ST1 and highly virulent ST7). Through the use of isogenic Δlgt, Δlsp and double Δlgt/Δlsp mutants, it was shown that lack of these enzymes did not influence S. suis adhesion/invasion to porcine respiratory epithelial cells. However, in the absence of the Lsp and/or Lgt, a significant reduction in the capacity of S. suis to activate phagocytic cells and induce pro-inflammatory mediators (in vitro and in vivo) was observed. In general, results obtained with the double mutant did not differ in comparison to single mutants, indicating lack of an additive effect. Finally, our data suggest that these enzymes play a differential role in virulence, depending on the genetic background of the strain and being more important for the highly virulent ST7 strain.

Intraoperative irradiation in breast cancer: preliminary results in 80 patients as partial breast irradiation or anticipated boost prior to hypo-fractionated whole breast irradiation

Purpose

To present the first results of intraoperative irradiation (IORT) in breast cancer with a low-energy photon system used as partial breast irradiation (PBI) or as an anticipated boost before whole breast hypo-fractionated irradiation (IORT + WBI), concerning tolerance, side effects, quality of life, and patient-reported outcomes.

Materials and methods

Eighty patients treated with an Intrabeam^® system of 50 kV X-rays received a 20 Gy dose intraoperatively were included. Moderate daily hypofractionation of 2.7 Gy in 15 fractions up to 40.5 Gy was administered if high-risk factors were present. Acute post-operative toxicity, surgery complications, chronic toxicity, patient-reported cosmesis and Breast-Q questionnaire were performed at follow-up visits.

Results

Thirty-one patients were treated as PBI and the remaining 49 as IORT + WBI. Only the IORT + WBI group presented acute toxicity, mainly mild acute dermatitis (11 patients) and one subacute mastitis. A total of 20 patients presented fibrosis (18 patients grade I, 2 patients grade II), 15 (30.5%) patients in the IORT + WBI group and 3 (9.6%) patients in the group of PBI. The cosmesis evaluation in 73 patients resulted poor, fair, good or excellent in 2, 7, 38 and 26 patients, respectively. In PBI group Breast-Q scored higher, especially in terms of their psychosocial well-being (78 vs 65) and satisfaction with radiation-induced toxicity (77 vs 72, respectively) compared to IORT + WBI group.

Conclusion

IORT is a well-tolerated procedure with low toxicity, good cosmesis and favorable patient-reported outcomes mainly when administered as PBI.

Experimental evaluation of protection and immunogenicity of Streptococcus suis bacterin-based vaccines formulated with different commercial adjuvants in weaned piglets

Streptococcus suis is an important swine pathogen responsible for economic losses to the swine industry worldwide. There is no effective commercial vaccine against S. suis. The use of autogenous (“bacterin”) vaccines to control S. suis outbreaks is a frequent preventive measure in the field, although scientific data on immunogenicity and reduction in mortality and morbidity are scarce. The goal of our study is to experimentally evaluate the immunogenicity and protective efficacy against homologous challenge in weaned piglets of a S. suis serotype 2 bacterin-based vaccine formulated with six different commercial adjuvants (Alhydrogel®, Emulsigen®-D, Quil-A®, Montanide™ ISA 206 VG, Montanide™ ISA 61 VG, and Montanide™ ISA 201 VG). The vaccine formulated with Montanide™ ISA 61 VG induced a significant increase in anti-S. suis antibodies, including both IgG1 and IgG2 subclasses, protected against mortality and significantly reduced morbidity and severity of clinical signs. Vaccines formulated with Montanide ISA 206 VG or Montanide ISA 201 VG also induced a significant increase in anti-S. suis antibodies and showed partial protection and reduction of clinical signs severity. Vaccines formulated with Alhydrogel®, Emulsigen®-D, or Quil-A® induced a low and IgG1-shifted antibody response and failed to protect vaccinated piglets against a homologous challenge. In conclusion, the type of adjuvant used in the vaccine formulation significantly influenced the immune response and efficacy of the vaccine against a homologous challenge.

P–543 Inhibition of cell proliferation and extracellular matrix formation in human uterine leiomyomas by 5-aza–2’-deoxycitidine via Wnt/ β-catenin pathway

Study question

Is DNA methylation reversion through DNA methyltransferases (DNMT) inhibitors, such as 5-aza–2’-deoxycitidine, a potential therapeutic option for treatment of patients with uterine leiomyomas (UL)?

Summary answer

5-aza–2’-deoxycitidine reduces proliferation and extracellular matrix (ECM) formation by inhibition of Wnt/ β-catenin pathway on UL cells, suggesting DNMT inhibitors as an option to treat UL. What is known already: UL is a multifactorial disease with an unclear pathogenesis and inaccurate treatment. Aberrant DNA methylation have been found in UL compared to myometrium (MM) tissue, showing hypermethylation of tumor suppressor genes, which contributes to the development of this tumor. The use of DNMT inhibitors, such as 5-aza–2’-deoxycytidine (5-aza-CdR), has been suggested to treat tumors in which altered methylation pattern is related to tumor progression, as occurs in UL. Based on this, we aimed to evaluate whether DNA methylation reversion through 5-aza-CdR reduces cell proliferation and ECM formation in UL cells, being a potential option for UL medical treatment.

Study design, size, duration

Prospective study comparing UL versus MM tissue and human uterine leiomyoma primary (HULP) cells treated with/without 5-aza-CdR at 0 µM (control), 2 µM, 5 µM and 10 µM for 72 hours. UL and MM tissue were collected from women without any hormonal treatment for the last 3 months (n = 16) undergoing myomectomy or hysterectomy due to symptomatic leiomyoma pathology. Participants were recruited between January 2019 and February 2020 at Hospital Universitario y Politecnico La Fe (Spain).

Participants/materials, setting, methods

Samples were collected from Caucasian premenopausal women aged 31–48 years, with a body mass index of &lt; 30 and without hormonal treatment. DNMT1 gene expression was analysed in UL vs MM tissue by qRT-PCR and activity of DNMT was measured in UL and MM tissue and cells by ELISA. 5-aza-CdR effect on proliferation was assessed by CellTiter test and Western blot (WB), apoptosis and ECM analyzed by WB and Wnt/ β-catenin pathway by qRT-PCR and WB. Main results and the role of chance: DNMT1 gene expression was increased in UL compared to MM tissue (fold change [FC]=2.49, p-value [p]=0.0295). Similarly, DNMT activity was increased in both UL compared to MM tissue and HULP cells versus MM cells (6.50 vs 3.76 OD/h/mg, p = 0.026; 211.30 vs 63.67 OD/h/mg, p = 0.284, respectively). After 5-aza-CdR treatment, cell viability of HULP cells was reduced in a dose dependent manner, being statistically significant at 10 µM (85.25%, p = 0.0001). Accordantly, PCNA protein expression was significantly decreased at 10 µM in HULP cells (FC = 0.695, p = 0.034), demonstrating cell proliferation inhibition. Additionally, 5-aza-CdR inhibited ECM protein expression in HULP cells in a dose-dependent manner being statistically significant at 10 µM for COLLAGEN I (FC = 0.654, p = 0.023) and PAI–1 (FC = 0.654, p = 0.023), and at 2 µM and 10 µM for FIBRONECTIN (FC = 0.812, p = 0.020; FC = 0.733, p = 0.035; respectively). Final targets of Wnt/ β-catenin pathway were decreased after 5-aza-CdR treatment, protein expression of WISP1 was significantly inhibited at 10 µM (FC = 0.699, p = 0.026), while expression levels of Wnt/ β-catenin target genes C-MYC (FC = 0.745, p = 0.028 at 2 µM; FC = 0.728, p = 0.019 at 10 µM) and MMP7 (FC = 0.520, p = 0.003 at 5 µM, FC = 0.577, p = 0.007 at 10 µM) were also significantly downregulated in HULP-treated cells vs untreated cells. Limitations, reasons for caution: This study has strict inclusion criteria to diminish epigenetic variability, thereby we should be cautious extrapolating our results to general population. Besides, this is a proof of concept with the inherent cell culture limitations. Further studies are necessary to determine 5-aza-CdR dose and adverse effects on UL in vivo.

Wider implications of the findings: 5-aza-CdR treatment reduces cell proliferation and ECM formation through Wnt/ β-catenin pathway inhibition, suggesting that inhibition of DNA methylation could be a promising new therapeutic approach to treat UL.

Trial registration number

Not applicable

Review of the speculative role of co-infections in Streptococcus suis-associated diseases in pigs

Streptococcus suis is one of the most important bacterial swine pathogens affecting post-weaned piglets, causing mainly meningitis, arthritis and sudden death. It not only results in severe economic losses but also raises concerns over animal welfare and antimicrobial resistance and remains an important zoonotic agent in some countries. The definition and diagnosis of S. suis-associated diseases can be complex. Should S. suis be considered a primary or secondary pathogen? The situation is further complicated when referring to respiratory disease, since the pathogen has historically been considered as a secondary pathogen within the porcine respiratory disease complex (PRDC). Is S. suis a respiratory or strictly systemic pathogen? S. suis is a normal inhabitant of the upper respiratory tract, and the presence of potentially virulent strains alone does not guarantee the appearance of clinical signs. Within this unclear context, it has been largely proposed that co-infection with some viral and bacterial pathogens can significantly influence the severity of S. suis-associated diseases and may be the key to understanding how the infection behaves in the field. In this review, we critically addressed studies reporting an epidemiological link (mixed infections or presence of more than one pathogen at the same time), as well as in vitro and in vivo studies of co-infection of S. suis with other pathogens and discussed their limitations and possibilities for improvement and proposed recommendations for future studies.

Immunogenicity study of a Streptococcus suis autogenous vaccine in preparturient sows and evaluation of passive maternal immunity in piglets

Background

Streptococcus suis is an important pathogen that causes severe diseases mostly in weaned piglets. Only available vaccines in the field are those composed of killed bacteria (bacterins) but data about their effectiveness are missing. We report here a field study on the immunological response induced by an autogenous vaccine applied in pre-parturient sows. Using a farm with recurrent S. suis serotype 7 problems, the study was divided in three experiments: (I) Sows received the vaccine at 7 and 3 weeks pre-farrowing. (II) Replacement gilts introduced to the herd received the vaccine at 4 and 7 weeks after their entry in quarantine and a boost 3 weeks pre-farrowing. (III) Gilts from experiment II received another boost 3 weeks pre-farrowing at their 3rd/4th parity. Levels, isotype profile and opsonophagocytosis capacity of the serum antibodies induced by vaccination were evaluated in sows and maternal immunity in piglets.

Results

In sows (I), the vaccine induced a slight, albeit significant, increase in anti-S. suis total antibodies after 2 doses when compare to basal levels already present in the animals. These antibodies showed a high opsonic capacity in vitro, highlighting their potential protective capacity. A gilt vaccination program of 3 doses (II) resulted in a significant increase in anti-S. suis total antibodies. Levels of maternal immunity transferred to piglets were high at 7 days of age, but rapidly decreased by 18 days of age. A gilt vaccination program ensued a higher transfer of maternal immunity in piglets compared to control animals; nevertheless duration was not improved at 18 day-old piglets. The vaccine response in both gilts and sows was mainly composed of IgG1 subclass, which was also the main Ig transferred to piglets. IgG2 subclass was also found in piglets, but its level was not increased by vaccination. Finally, a recall IgG1 response was induced by another boost vaccination at 3rd/4th parity (III), indicating that the vaccine induced the establishment of a lasting memory response in the herd.

Conclusions

Overall, an optimal gilt/sow vaccination program might result in increased antibody responses; nevertheless duration of maternal immunity would not last long enough to protect post-weaned piglets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02774-4.

Pre- and Post-partum Concentrations of Interleukin 1α, Interleukin 8, and α1-Acid Glycoprotein in Vaginal Fornix and Endometrium of Dairy Cows With Clinical Cervicitis

Innate immunity is the principal sensor responsible of the local immune response to control mucosal bacterial contamination of the reproductive tract after parturition, triggering a pro-inflammatory process in the mucosa of the uterus, the vaginal and the cervix. However, knowledge about the inflammation process and outcome of the cervix in dairy cows is scarce even though it plays an important anatomic and functional role between the vagina and the uterus. The objective of the present study was to describe the cellular and humoral local innate immune response during clinical cervicitis (CC) in the uterus and vaginal fornix in pre- and post-partum periods of dairy cows. A retrospective descriptive study was performed involving 26 animals, characterized as clinical cervicitis cows (n = 19) and healthy cows (n = 7). Blood and mucus of the different compartments of the genital tract were sampled and records of the cows' genital exam were performed four times: −1 w (day −7 ± 2, prepartum), +1 w (day +7 ± 4), +3 w (day +21 ± 4) and +5 w (day +35 ± 4) postpartum. Clinical cervicitis was defined as cows exhibiting a cervix grade−2 and healthy cows were defined as a cow clinically normal with a grade-0 cervix at time +5 w. Blood white cell count, vaginal fornix and endometrial neutrophils percentage, and the concentrations of interleukin 1α (IL1), interleukin 8 (IL8), and α1-acid glycoprotein (AGP) in mucus were determined. The results showed that 23% of the cows were categorized as CC at time +5 w. Cases of CC with purulent vaginal discharge or subclinical endometritis shown the highest cytokine production. At +3 w, IL1, IL8, and AGP concentrations in the uterus and the fornix were significantly higher in CC than healthy cows (CH). In conclusion, the 3-week postpartum is a critical point to evaluate cytokines and acute phase proteins; where IL1 and IL8 variation kept a direct relation with neutrophils numbers and function. The presence of AGP in the endometrium infer a homeostatic proinflammatory protective balance effect, modulating the local uterine innate immune response during peripartum.

Pain burden, sensory profile and inflammatory cytokines of dogs with naturally-occurring neuropathic pain treated with gabapentin alone or with meloxicam

Canine neuropathic pain (NeuP) has been poorly investigated. This study aimed to evaluate the pain burden, sensory profile and inflammatory cytokines in dogs with naturally-occurring NeuP. Twenty-nine client-owned dogs with NeuP were included in a prospective, partially masked, randomized crossover clinical trial, and treated with gabapentin/placebo/gabapentin-meloxicam or gabapentin-meloxicam/placebo/gabapentin (each treatment block of 7 days; total 21 days). Pain scores, mechanical (MNT) and electrical (ENT) nociceptive thresholds and descending noxious inhibitory controls (DNIC) were assessed at baseline, days 7, 14, and 21. DNIC was evaluated using ΔMNT (after-before conditioning stimulus). Positive or negative ΔMNT corresponded to inhibitory or facilitatory pain profiles, respectively. Pain scores were recorded using the Client Specific Outcome Measures (CSOM), Canine Brief Pain Inventory (CBPI), and short-form Glasgow Composite Measure Pain Scale (CMPS-SF). Data from baseline were compared to those of sixteen healthy controls. ΔMNT, but not MNT and ENT, was significantly larger in controls (2.3 ± 0.9 N) than in NeuP (-0.2 ± 0.7 N). The percentage of dogs with facilitatory sensory profile was similar at baseline and after placebo (61.5–63%), and between controls and after gabapentin (33.3–34.6%). The CBPI scores were significantly different between gabapentin (CBPI _pain and CBPI _{overall impression}) and/or gabapentin-meloxicam (CBPI _pain and _interference) when compared with baseline, but not placebo. The CBPI scores were not significantly different between placebo and baseline. The concentration of cytokines was not different between groups or treatments. Dogs with NeuP have deficient inhibitory pain mechanisms. Pain burden was reduced after gabapentin and/or gabapentin-meloxicam when compared with baseline using CBPI and CMPS-SF scores. However, these scores were not superior than placebo, nor placebo was superior to baseline evaluations. A caregiver placebo effect may have biased the results.

In vitro characterization of granulocyte-colony stimulating factor (G-CSF) production by dendritic cells and macrophages during Streptococcus suis infection

Streptococcus suis serotype 2 is an important porcine bacterial pathogen and emerging zoonotic agent. Infections induce an exacerbated inflammation that can result in sudden death (septic shock) and meningitis. Though neutrophilic leukocytosis characterizes S. suis infection, the mediators involved are poorly understood. Among them, granulocyte-colony stimulating factor (G-CSF), a pro-inflammatory cytokine, triggers proliferation of neutrophil progenitors and neutrophil mobilization. However, the systemic production of G-CSF induced during S. suis infection, the cell types involved, and the underlying mechanisms remain unknown. In a S. suis serotype 2 mouse model of systemic infection, plasma levels of G-CSF rapidly increased after infection. S. suis activation of DCs and macrophages resulted in high (> 1000 pg/mL) and comparable production levels of G-CSF, as measured by ELISA. By using mutant strains deficient in capsular polysaccharide (CPS) or lipoprotein maturation in combination with purified lipoteichoic acid (LTA) from the latter mutant strain, it was showed that G-CSF production is mainly mediated by S. suis lipoproteins. The Toll-like receptor (TLR) pathway via myeloid differentiation primary response 88 (MyD88) is required for G-CSF production by DCs and macrophages following S. suis activation, with a partial involvement of TLR2. On the other hand, TLR2-independant G-CSF production induced by S. suis requires internalization and bacterial DNA might play a role in this pathway. Finally, these signals activated nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways leading to G-CSF production. In conclusion, this study demonstrated for the first time that S. suis induces G-CSF production in vivo and DCs and macrophages are key cellular sources of this cytokine mediator, mainly via the binding of lipoproteins to TLR2. The CPS significantly reduced this activation, confirming the powerful role of this component in S. suis virulence. As such, this study contributes to better understand how DCs and macrophages produce G-CSF in response to S. suis, and potentially to other streptococci.

Identification of a novel TLR5 agonist derived from the P97 protein of Mycoplasma hyopneumoniae

By modulating specific immune responses against antigens, adjuvants are used in many vaccine preparations to enhance protective immunity. The C-terminal domain of the protein P97 (P97c) of Mycoplasma hyopneumoniae, which is the etiologic agent of porcine enzootic pneumonia, has been shown to increase the specific humoral response against an antigen when this antigen is merged with P97c and delivered by adenovectors. However, the immunostimulating mechanism of this protein remains unknown. In the present study, recombinantly expressed P97c triggered a concentration-dependent TLR5 activation and stimulates the production of interleukin-8 from HEK-Blue mTLR5 cells. Circular dichroism spectroscopy and prediction of 3-dimensional conformation exposed a relevant secondary and tertiary structural homology between P97c and flagellin, the known potent TLR5 agonist. P97c adjuvanticity was evaluated by fusing the conserved epitope of the ectodomain matrix 2 protein (M2e) of the influenza A virus to the protein. Mice immunized with P97c-3M2e revealed a high antibody titer against the M2e epitope associated with a mixed Th1/Th2 immune response. Overall, this study identifies a novel agonist of the pattern recognition receptor TLR5 and reveals that P97c is a potential adjuvant through the activation of the innate immune system.

Update on Streptococcus suis Research and Prevention in the Era of Antimicrobial Restriction: 4th International Workshop on S. suis

Streptococcus suis is a swine pathogen and a zoonotic agent afflicting people in close contact with infected pigs or pork meat. Sporadic cases of human infections have been reported worldwide. In addition, S. suis outbreaks emerged in Asia, making this bacterium a primary health concern in this part of the globe. In pigs, S. suis disease results in decreased performance and increased mortality, which have a significant economic impact on swine production worldwide. Facing the new regulations in preventive use of antimicrobials in livestock and lack of effective vaccines, control of S. suis infections is worrisome. Increasing and sharing of knowledge on this pathogen is of utmost importance. As such, the pathogenesis and epidemiology of the infection, antimicrobial resistance, progress on diagnosis, prevention, and control were among the topics discussed during the 4th International Workshop on Streptococcus suis (held in Montreal, Canada, June 2019). This review gathers together recent findings on this important pathogen from lectures performed by lead researchers from several countries including Australia, Canada, France, Germany, Japan, Spain, Thailand, The Netherlands, UK, and USA. Finally, policies and recommendations for the manufacture, quality control, and use of inactivated autogenous vaccines are addressed to advance this important field in veterinary medicine.

Differential role of MyD88 signaling in Streptococcus suis serotype 2-induced systemic and central nervous system diseases

Streptococcus suis serotype 2 is an important porcine bacterial pathogen and a zoonotic agent responsible for sudden death, septic shock and meningitis, with exacerbated inflammation being a hallmark of the systemic and central nervous system (CNS) infections. However, S. suis serotype 2 strains are genetically and phenotypically heterogeneous, being composed of a multitude of sequence types (STs) whose virulence greatly varies. Yet, most studies have used 'classical' virulent Eurasian ST1 or ST7 strains, even though ST25 and ST28 strains account for most isolates in North America. While recognition of S. suis by innate immune cells has been associated with the myeloid differentiation primary response 88 (MyD88)-dependent Toll-like receptor (TLR) pathway in vitro, particularly surface-associated TLR2, little information is available regarding its role in vivo. This study demonstrates for the first time a differential role of MyD88 signaling in S. suis-induced systemic and CNS diseases, regardless of strain background diversity. The MyD88-dependent pathway is critical for the development of systemic disease via its role in inflammation, which subsequently controls bacterial burden. However, and differently from what has been described in vitro, TLR2 and TLR4 individually do not contribute to systemic disease, suggesting possible compensation in their absence and/or a collaborative role with other MyD88-dependent TLRs. On the other hand, CNS disease does not necessarily require MyD88 signaling and, consequently, neither TLR2 nor TLR4, suggesting a partial implication of other pathways. Finally, regardless of its notable heterogeneity, recognition of S. suis serotype 2 appears to be similar, indicating that recognized components are conserved motifs.

Cannabinoid hyperemesis syndrome, a treatment discussion

Introduction

Cannabinoid hyperemesis syndrome (CHS), is characterized by recurrent episodes of severe nausea and intractable vomiting, preceded by chronic use of cannabis. A pathognomonic characteristic is compulsive bathing in hot water. The resolution of the problem occurs when cannabis use is stopped. However, patients are often reluctant to discontinue cannabis. Treatment with anti-emetic medication is ineffective. Case series suggested haloperidol as a potential treatment. Other antipsychotics as olanzapine has been used as anti-emetic treatment in chemotherapy.

Objectives

To describe three cases of patients with CHS whom showed a successful response to olanzapine, even when, haloperidol had failed.

Aims

To present an alternative treatment for CHS which can offer benefits over haloperidol.

Methods

We present three cases of patients who suffered from CHS and were admitted to emergency department. All patients were treated with olanzapine after conventional anti-hemetic treatment failure. One patient was also unsuccessfully treated with haloperidol.

Results

All three patients showed a good response to olanzapine treatment. Different presentations were effective: velotab and intramuscular. Their nausea, vomits and agitation were ameliorated. They could be discharge after maintained remission of symptoms.

Conclusions

Olanzapine should be considered as an adequate treatment for CHS. Its suitable receptorial profile, its availability in different routes of administration and its side effects profile could offer some benefits over haloperidol.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Ampicillin Treatment Increases Placental Interleukin-1 Beta Concentration and Polymorphonuclear Infiltration in Group B Streptococcus-Induced Chorioamnionitis: A Preclinical Study

BACKGROUND

Antibiotic therapy during preterm labor with intact membranes has been associated with an increased risk of neonatal death.

OBJECTIVES

Using an established rat model of group B Streptococcus (GBS)-induced chorioamnionitis, we hypothesized that ampicillin treatment increases placental inflammation, as shown in other bacterial infections.

METHODS

At gestational day 19, 19 Lewis dams were intraperitoneally (i.p.) inoculated by 108 CFU of β-hemolytic serotype Ia GBS (strain #16955 susceptible to ampicillin). Dams were treated i.p. with either 200 mg/kg of ampicillin (n = 9) or 0.9% saline (n = 10) at 48 and 60 h post-GBS inoculation. Cesarean sections were performed 72 h post-GBS inoculation.

RESULTS

Ampicillin treatment was associated with an increased number of polymorphonuclear cells (PMN) infiltrating the decidua (mean 1,536 vs. 532 PMN/mm2; p < 0.001) and a higher placental concentration of IL-1β (mean 26.4 vs. 7.9 pg/mg; p < 0.01) compared to saline-treated dams. These effects were observed in dams without GBS bacteremia. Conversely, ampicillin treatment was associated with a decreased placental concentration of proinflammatory cytokines in dams with GBS bacteremia.

CONCLUSIONS

Ampicillin increases placental inflammation in a rat model of GBS-induced chorioamnionitis without bacteremia. This proinflammatory effect of ampicillin could be due to bacterial lysis. Our findings do not query the intrapartum antibiotic prophylaxis against GBS disease. They pave the way for future preclinical studies combining anti-inflammatory treatments and antibiotic therapy for GBS-induced chorioamnionitis.

Interactions of Streptococcus suis serotype 9 with host cells and role of the capsular polysaccharide: Comparison with serotypes 2 and 14

Streptococcus suis is an important porcine bacterial pathogen and a zoonotic agent responsible for sudden death, septic shock and meningitis, of which serotype 2 is the most widespread, with serotype 14 also causing infections in humans in South-East Asia. Knowledge of its pathogenesis and virulence are almost exclusively based on these two serotypes. Though serotype 9 is responsible for the greatest number of porcine cases in Spain, the Netherlands and Germany, very little information is currently available regarding this serotype. Of the different virulence factors, the capsular polysaccharide (CPS) is required for S. suis virulence as it promotes resistance to phagocytosis and killing and masks surface components responsible for host cell activation. However, these roles have been described for serotypes 2 and 14, whose CPSs are structurally and compositionally similar, both containing sialic acid. Consequently, we evaluated herein the interactions of serotype 9 with host cells and the role of its CPS, which greatly differs from those of serotypes 2 and 14. Results demonstrated that serotype 9 adhesion to but not invasion of respiratory epithelial cells was greater than that of serotypes 2 and 14. Furthermore serotype 9 was more internalized by macrophages but equally resistant to whole blood killing. Though recognition of serotypes 2, 9 and 14 by DCs required MyD88-dependent signaling, in vitro pro-inflammatory mediator production induced by serotype 9 was much lower. In vivo, however, serotype 9 causes an exacerbated inflammatory response, which combined with persistent bacterial presence, is probably responsible for host death during the systemic infection. Though presence of the serotype 9 CPS masks surface components less efficiently than those of serotypes 2 and 14, the serotype 9 CPS remains critical for virulence as it is required for survival in blood and development of clinical disease, and this regardless of its unique composition and structure.

Interleukin-1 signaling induced by Streptococcus suis serotype 2 is strain-dependent and contributes to bacterial clearance and inflammation during systemic disease in a mouse model of infection

Streptococcus suis serotype 2 is an important porcine pathogen and zoonotic agent causing sudden death, septic shock and meningitis, with exacerbated inflammation being a hallmark of the infection. A rapid, effective and balanced innate immune response against S. suis is critical to control bacterial growth without causing excessive inflammation. Even though interleukin (IL)-1 is one of the most potent and earliest pro-inflammatory mediators produced, its role in the S. suis pathogenesis has not been studied. We demonstrated that a classical virulent European sequence type (ST) 1 strain and the highly virulent ST7 strain induce important levels of IL-1 in systemic organs. Moreover, bone marrow-derived dendritic cells and macrophages contribute to its production, with the ST7 strain inducing higher levels. To better understand the underlying mechanisms involved, different cellular pathways were studied. Independently of the strain, IL-1β production required MyD88 and involved recognition via TLR2 and possibly TLR7 and TLR9. This suggests that the recognized bacterial components are similar and conserved between strains. However, very high levels of the pore-forming toxin suilysin, produced only by the ST7 strain, are required for efficient maturation of pro-IL-1β via activation of different inflammasomes resulting from pore formation and ion efflux. Using IL-1R^−/− mice, we demonstrated that IL-1 signaling plays a beneficial role during S. suis systemic infection by modulating the inflammation required to control and clear bacterial burden, thus promoting host survival. Beyond a certain threshold, however, S. suis-induced inflammation cannot be counterbalanced by this signaling, making it difficult to discriminate its role.

Antigen I/II Participates in the Interactions of Streptococcus suis Serotype 9 With Phagocytes and the Development of Systemic Disease

Streptococcus suis is an important porcine bacterial pathogen and a zoonotic agent causing a variety of pathologies including sudden death, septic shock, and meningitis. Though serotype 2 is the most studied serotype due to its presence worldwide, serotype 9 is responsible for the greatest number of porcine cases in Spain, the Netherlands, and Germany. Regardless of its increasing importance, very few studies have investigated S. suis serotype 9 virulence factors and pathogenesis. Antigens I/II (AgI/II) are multimodal adhesion proteins implicated in host respiratory tract and oral cavity persistence of various pathogenic human streptococci. It was recently demonstrated that AgI/II is involved in various bacterial functions for serotype 9, participating in the initial steps of the pathogenesis of the infection. However, its contribution to the systemic infection remains unknown. As such, we evaluated herein the role of the S. suis serotype 9 AgI/II in the interactions with phagocytes and the development of systemic disease in a mouse model of infection. Results demonstrated that the presence of AgI/II is important for the development of clinical systemic disease by promoting bacterial survival in blood possibly due to its effect on S. suis phagocytosis, as shown with macrophages and dendritic cells. Furthermore, AgI/II directly participates in dendritic cell activation and pro-inflammatory mediator production following recognition by the Toll-like receptor pathway, which may contribute to the exacerbated systemic inflammation responsible for host death. Taken together, this study demonstrates that the S. suis serotype 9 AgI/II is important for virulence during systemic infection and development of disease. In fact, this is the first study to describe a role of an AgI/II family member in systemic bacterial disease.

Intra-Species and Inter-Species Differences in Cytokine Production by Porcine Antigen-Presenting Cells Stimulated by Mycoplasma hyopneumoniae, M. hyorhinis, and M. flocculare

Mycoplasma hyorhinis and M. flocculare are commonly co-isolated with M. hyopneumoniae (primary agent of swine enzootic pneumonia) in gross pneumonia-like lesions, but their involvement in the disease process remains unknown. T cells play an immuno-pathological role during mycoplasmal infections. Dendritic cells (DCs) are major antigen-presenting cells involved in T cell activation and differentiation. In this study, we investigated cytokine (IL-6, IL-8, IL-10, IL-12, and TNF-α) production by porcine bone-marrow-derived DCs (BM-DCs) stimulated by M. hyopneumoniae, M. hyorhinis, and/or M. flocculare. Results showed that cytokine production levels were relatively homogenous for all evaluated M. hyopneumoniae strains in contrast to M. hyorhinis and M. flocculare strains. The most noteworthy inter-species differences were the overall (i) lower IL-12 production capacity of M. hyopneumoniae, and (ii) higher TNF-α production capacity of M. flocculare. Co-stimulation of BM-DCs showed that M. hyorhinis dominated the IL-12 production independently of its association with M. hyopneumoniae or M. flocculare. In addition, a decreased BM-DC production of TNF-α was generally observed in the presence of mycoplasma associations. Lastly, M. flocculare association with M. hyopneumoniae increased BM-DC ability to secrete IL-10. A higher cytotoxicity level in BM-DCs stimulated by M. hyorhinis was also observed. Overall, this study demonstrated that the combination of M. hyorhinis or M. flocculare with M. hyopneumoniae may participate to the modulation of the immune response that might affect the final disease outcome.

Maps of Tethys' Thermophysical Properties

On 11^th April 2015 Cassini's Composite Infrared Spectrometer (CIRS) made a series of observations of Tethys' daytime anti-Saturn hemisphere over a nine-hour time period. During this time the sub-spacecraft position was remarkably stable (0.3° S to 3.9° S; 153.2° W to 221.8° W), and so these observations provide unprecedented coverage of diurnal temperature variations on Tethys' anti-Saturn hemisphere. In 2012 a thermal anomaly was discovered at low latitudes on Tethys' leading hemisphere; it appears cooler during the day and warmer at night than its surroundings (Howett et al., 2012) and is spatially correlated with a decrease in the IR3/UV3 visible color ratio (Schenk et al., 2011). The cause of this anomaly is believed to be surface alteration by high-energy electrons, which preferentially bombard low-latitudes of Tethys' leading hemisphere (Schenk et al., 2011; Howett et al., 2012; Paranicas et al. 2014; Schaible et al., 2017). The thermal anomaly was quickly dubbed "Pac-Man" due to its resemblance to the 1980s video game icon. We use these daytime 2015 CIRS data, along with two sets of nighttime CIRS observations of Tethys (from 27 June 2007 and 17 August 2015) to make maps of bolometric Bond albedo and thermal inertia variations across the anti-Saturn hemisphere of Tethys (including the edge of its Pac-Man region). These maps confirm the presence of the Pac-Man thermal anomaly and show that while Tethys' bolometric Bond albedo varies negligibly outside and inside the anomaly (0.69±0.02 inside, compared to 0.71±0.04 outside) the thermal inertia varies dramatically (29±10 J m^-2 K^-1 s^-1/2 inside, compared to 9±4 J m^-2 K^-1 s^-1/2 outside). These thermal inertias are in keeping with previously published values: 25±3 J m^-2 K^-1 s^-1/2 inside, and 5±1 J m^-2 K^-1 s^-1/2 outside the anomaly (Howett et al., 2012). A detailed analysis shows that on smaller spatial-scales the bolometric Bond albedo does vary: increasing to a peak value at 180° W. For longitudes between ~100° W and ~160° W the thermal inertia increases from northern to southern latitudes, while the reverse is true for bolometric Bond albedo. The thermal inertia on Tethys generally increases towards the center of its leading hemisphere but also displays other notable small-scale variations. These thermal inertia and bolometric Bond albedo variations are perhaps due to differences in competing surface modification by E ring grains and high-energy electrons which both bombard Tethys' leading hemisphere (but in different ways). A comparison between the observed temperatures and our best thermal model fits shows notable discrepancies in the morning warming curve, which may provide evidence of regional variations in surface roughness effects, perhaps again due to variations in surface alteration mechanisms.

A platform for glycoengineering a polyvalent pneumococcal bioconjugate vaccine using E. coli as a host

Chemical synthesis of conjugate vaccines, consisting of a polysaccharide linked to a protein, can be technically challenging, and in vivo bacterial conjugations (bioconjugations) have emerged as manufacturing alternatives. Bioconjugation relies upon an oligosaccharyltransferase to attach polysaccharides to proteins, but currently employed enzymes are not suitable for the generation of conjugate vaccines when the polysaccharides contain glucose at the reducing end, which is the case for ~75% of Streptococcus pneumoniae capsules. Here, we use an O-linking oligosaccharyltransferase to generate a polyvalent pneumococcal bioconjugate vaccine with polysaccharides containing glucose at their reducing end. In addition, we show that different vaccine carrier proteins can be glycosylated using this system. Pneumococcal bioconjugates are immunogenic, protective and rapidly produced within E. coli using recombinant techniques. These proof-of-principle experiments establish a platform to overcome limitations of other conjugating enzymes enabling the development of bioconjugate vaccines for many important human and animal pathogens.

Bioconjugation is a promising process to manufacture conjugate vaccines, but currently employed enzymes cannot generate the full spectrum of bacterial glycoproteins. Here, the authors use an O-linking oligosaccharyltransferase to generate a polyvalent pneumococcal bioconjugate vaccine with polysaccharides containing glucose at their reducing end.

Milk digestion in the young rabbit: methodology and first results

This study aims to determine the digestibility of milk by the young rabbit (21-25 d old), taking into account the increment of digesta content and urine excretion. Nineteen litters of 9 young rabbits 21 to 25 d old were used: 12 litters (S group) fed exclusively with milk using controlled suckling, and 7 litters (Control group) with free suckling and access to the pelleted feed of the doe. The faecal digestibility of milk dry matter (DM) was measured between 21 and 25 d of age, for S litters housed from 15 d of age in a metabolism cage separately from their mother. Between 21 and 25 d, the milk intake, faeces and urine excretion were controlled daily, and the mean increment in digesta content was measured by comparing digesta weight of the whole tract at 21 and 25 d of age (one kit per litter). The increment in digesta content from 21 to 25 d averaged 77% (+8.5 g), sourcing mainly from stomach and caecum contents increase (+57 and +120% respectively). The mean increase for the dry content of the gut (from 21 to 25 d) was 1.75 g DM/kit, and was considered as non-digested to calculate the digestibility coefficient of the milk. The milk intake averaged 30 g/d/kit (7.9 g DM/d kit). No faecal excretion was recorded between 21 and 25 d. From the milk intake and increment in digesta content, the corrected digestibility of the milk dry matter reached 94% (minimum=92.9%, maximum=95.6%). The daily urine excretion averaged 5.1 mL/kit, corresponding to 1.2 g DM/kit. Therefore, the corrected DM retention coefficient of the milk was 79.5%. The quantity of nitrogen excreted in urine was low (0.06 g/d kits), thus the corrected nitrogen retention coefficient for milk reached 82% and the nitrogen retained (corrected) reached 0.44 g/d kit. Accordingly, the amount in metabolisable protein for the milk was 90 g/kg (fresh). The corrected energy retention coefficient was estimated to 95.8%, for a crude energy concentration estimated at 28.14 MJ/kg DM for the milk. Thus, the energy retained (corrected) reached 223 kJ/d kit and the content in metabolisable energy for the milk was 26.94 MJ/kg DM.

Structure determination of Streptococcus suis serotypes 7 and 8 capsular polysaccharides and assignment of functions of the cps locus genes involved in their biosynthesis

Streptococcus suis serotypes 7 and 8 are counted among the top six S. suis serotypes causing clinical disease in pigs. Yet, limited information is available on these serotypes. Since S. suis serotyping system is based upon capsular polysaccharide (CPS) antigenicity and the CPS is considered a major virulence factor for encapsulated pathogens, here we determined for the first time the chemical compositions and structures of serotypes 7 and 8 CPSs. Chemical and spectroscopic data gave the following repeating unit sequences: [3)L-Rha(α1-P-2)D-Gal(α1-4)D-GlcA(β1-3)D-FucNAc4N(α1-]_n for serotype 7 and [2)L-Rha(α1-P-4)D-ManNAc(β1-4)D-Glc(α1-]_n for serotype 8. As serotype 8 CPS is identical to Streptococcus pneumoniae type 19F CPS, dot-blot analyses showed a strong reaction of the 19F polysaccharide with reference anti-S. suis serotype 8 rabbit serum. A correlation between S. suis serotypes 7 and 8 sequences and genes of those serotypes' loci encoding putative glycosyltransferases and polymerases responsible for the biosynthesis of the repeating units was tentatively established. Knowledge of CPS structure and composition will contribute to better dissect the role of this bacterial component in the pathogenesis of the disease caused by S. suis serotypes 7 and 8.

Eye-Hand Coordination Assessment Metrics Using a Multi-Platform Haptic System with Eye-Tracking and Motion Capture Feedback

In this paper, we discuss the possibility to determine assessment metrics for eye-hand coordination, using a mapping between a robotic haptic device to a virtual environment, and correlating it with the eye-gaze and upper arm movements. Our goal is to develop, implement and refine a system that will assess and improve eye-hand coordination in individuals with disabilities. A detailed analysis of patterns was conducted by therapists in order to select various levels of difficulty that could be included in the system, and which would yield the greatest benefit in terms of assessment of coordination as well as in training. Participants were instructed to use a haptic device (Omni) to follow the trajectories. This was completed while video data were collected using a Vicon motion capture system. Readings of traced trajectories, time, and upper limb motions were recorded for further analysis. One of the patterns was chosen to develop a multi-platform haptic system to be virtually rendered with any haptic device and a Graphic User Interface (GUI) with options to guide the user along the chosen pattern using a haptic tunnel calculated by using B-splines. Two types of haptic tunnels are presented and evaluated: one that follows the mid path of the pattern, and one that takes the smoothest path through the pattern. Finally, the Pearson coefficient was chosen as a metric to correlate the haptic device and the eye-gaze coordinates recorded simultaneously while the user traces a path.

A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex

Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon-which was previously expected to be trapped in the troposphere-can influence the stratospheric temperatures some 300 km above Saturn's clouds.

Role of the Streptococcus suis serotype 2 capsular polysaccharide in the interactions with dendritic cells is strain-dependent but remains critical for virulence

Streptococcus suis serotype 2 is an important porcine bacterial pathogen and zoonotic agent responsible for sudden death, septic shock, and meningitis. However, serotype 2 strains are heterogeneous, composed of a multitude of sequence types (STs) whose distribution greatly varies worldwide. Of the virulence factors presently described for S. suis, the capsular polysaccharide (CPS) is a critical factor implicated in a multitude of functions, including in impairment of phagocytosis and innate immune cell activation by masking underlying bacterial components. However, these roles have been described using Eurasian ST1 and ST7 strains, which greatly differ from North American ST25 strains. Consequently, the capacity of the CPS to mask surface antigens and putative virulence factors in non-Eurasian strains remains unknown. Herein, the role of the S. suis serotype 2 CPS of a prototype intermediate virulent North American ST25 strain, in comparison with that of a virulent European ST1 strain, with regards to interactions with dendritic cells, as well as virulence during the systemic phase of infection, was evaluated. Results demonstrated that the CPS remains critical for virulence and development of clinical disease regardless of strain background, due to its requirement for survival in blood. However, its role in the interactions with dendritic cells is strain-dependent. Consequently, certain key characteristics associated with the CPS are not necessarily applicable to all S. suis serotype 2 strains. This indicates that though certain factors may be important for S. suis serotype 2 virulence, strain background could be as determining, reiterating the need in using strains from varying backgrounds in order to better characterize the S. suis pathogenesis.

Streptococcus suis serotype 3 and serotype 18 capsular polysaccharides contain di-N-acetyl-bacillosamine

Streptococcus suis serotype 3 is counted among the S. suis serotypes causing clinical disease in pigs. Yet, limited information is available on this serotype. Here we determined for the first time the chemical composition and structure of serotype 3 capsular polysaccharide (CPS), a major bacterial virulence factor and the antigen at the origin of S. suis classification into serotypes. Chemical and spectroscopic data gave the repeating unit sequence for serotype 3: [4)D-GlcA (β1-3)d-QuiNAc4NAc(β1-]_n. To the best of our knowledge, this is the first report of di-N-acetyl-d-bacillosamine (QuiNAc4NAc) containing polysaccharides in Streptococci and the second time this rare diamino sugar has been observed in a Gram-positive bacterial species since its initial report. This led to the identification of homologues of UDP-QuiNAc4NAc synthesis genes in S. suis serotype 18. Thus, the repeating unit sequence for serotype 18 is: [3)d-GalNAc(α1-3)[d-Glc (β1-2)]d-GalA4OAc(β1-3)d-GalNAc(α1-3)d-QuiNAc4NAc(α1-]_n. A correlation between S. suis serotypes 3 and 18 CPS sequences and genes of these serotypes' cps loci encoding putative glycosyltransferases and polymerase responsible for the biosynthesis of the repeating unit was tentatively established. Knowledge of CPS structure and composition will contribute to better dissect the role of this bacterial component in the pathogenesis of S. suis serotypes 3 and 18.

Phagocytosis, bacterial killing, and cytokine activation of circulating blood neutrophils in horses with severe equine asthma and control horses

OBJECTIVE To evaluate in vitro phagocytosis and bactericidal activity of circulating blood neutrophils in horses with severe equine asthma and control horses and to determine whether circulating blood neutrophils in horses with severe equine asthma have an increase in expression of the proinflammatory cytokine tumor necrosis factor (TNF)-α and the chemokine interleukin (IL)-8 and a decrease in expression of the anti-inflammatory cytokine IL-10 in response to bacteria. ANIMALS 6 horses with severe equine asthma and 6 control horses. PROCEDURES Circulating blood neutrophils were isolated from horses with severe equine asthma and control horses. Phagocytosis was evaluated by use of flow cytometry. Bactericidal activity of circulating blood neutrophils was assessed by use of Streptococcus equi and Streptococcus zooepidemicus as targets, whereas the cytokine mRNA response was assessed by use of a quantitative PCR assay. RESULTS Circulating blood neutrophils from horses with severe equine asthma had significantly lower bactericidal activity toward S zooepidemicus but not toward S equi, compared with results for control horses. Phagocytosis and mRNA expression of TNF-α, IL-8, and IL-10 were not different between groups. CONCLUSIONS AND CLINCAL RELEVANCE Impairment of bactericidal activity of circulating blood neutrophils in horses with severe equine asthma could contribute to an increased susceptibility to infections.

Streptococcus suis Serotype 2 Infection Impairs Interleukin-12 Production and the MHC-II-Restricted Antigen Presentation Capacity of Dendritic Cells

Streptococcus suis is an important swine pathogen and emerging zoonotic agent. Encapsulated strains of S. suis modulate dendritic cell (DC) functions, leading to poorly activated CD4⁺ T cells. However, the antigen presentation ability of S. suis-stimulated DCs has not been investigated yet. In this work, we aimed to characterize the antigen presentation profiles of S. suis-stimulated DCs, both in vitro and in vivo. Upon direct activation in vitro, S. suis-stimulated murine bone marrow-derived DCs (bmDCs) preserved their antigen capture/processing capacities. However, they showed delayed kinetics of MHC-II expression compared to lipopolysaccharide-stimulated bmDCs. Meanwhile, splenic DCs from infected mice exhibited a compromised MHC-II expression, despite an appropriate expression of maturation markers. To identify potential interfering mechanisms, Class II Major Histocompatibility Complex Transactivator (CIITA) and membrane-associated RING-CH (MARCH)1/8 transcription were studied. S. suis-stimulated DCs maintained low levels of CIITA at early time points, both in vitro and in vivo, which could limit their ability to increase MHC-II synthesis. S. suis-stimulated DCs also displayed sustained/upregulated levels of MARCH1/8, thus possibly leading to MHC-II lysosomal degradation. The bacterial capsular polysaccharide played a partial role in this modulation. Finally, interleukin (IL)-12p70 production was inhibited in splenic DCs from infected mice, a profile compatible with DC indirect activation by pro-inflammatory compounds. Consequently, these cells induced lower levels of IL-2 and TNF-α in an antigen-specific CD4⁺ T cell presentation assay and blunted T cell CD25 expression. It remains unclear at this stage whether these phenotypical and transcriptional modulations observed in response to S. suis in in vivo infections are part of a bacterial immune evasion strategy or rather a feature common to systemic inflammatory response-inducing agents. However, it appears that the MHC-II-restricted antigen presentation and Th1-polarizing cytokine production capacities of DCs are impaired during S. suis infection. This study highlights the potential consequences of inflammation on the type and magnitude of the immune response elicited by a pathogen.

Capsular Sialyltransferase Specificity Mediates Different Phenotypes in Streptococcus suis and Group B Streptococcus

The capsular polysaccharide (CPS) represents a key virulence factor for most encapsulated streptococci. Streptococcus suis and Group B Streptococcus (GBS) are both well-encapsulated pathogens of clinical importance in veterinary and/or human medicine and responsible for invasive systemic diseases. S. suis and GBS are the only Gram-positive bacteria which express a sialylated CPS at their surface. An important difference between these two sialylated CPSs is the linkage between the side-chain terminal galactose and sialic acid, being α-2,6 for S. suis but α-2,3 for GBS. It is still unclear how sialic acid may affect CPS production and, consequently, the pathogenesis of the disease caused by these two bacterial pathogens. Here, we investigated the role of sialic acid and the putative effect of sialic acid linkage modification in CPS synthesis using inter-species allelic exchange mutagenesis. To this aim, a new molecular biogenetic approach to express CPS with modified sialic acid linkage was developed. We showed that sialic acid (and its α-2,6 linkage) is crucial for S. suis CPS synthesis, whereas for GBS, CPS synthesis may occur in presence of an α-2,6 sialyltransferase or in absence of sialic acid moiety. To evaluate the effect of the CPS composition/structure on sialyltransferase activity, two distinct capsular serotypes within each bacterial species were compared (S. suis serotypes 2 and 14 and GBS serotypes III and V). It was demonstrated that the observed differences in sialyltransferase activity and specificity between S. suis and GBS were serotype unrestricted. This is the first time that a study investigates the interspecies exchange of capsular sialyltransferase genes in Gram-positive bacteria. The obtained mutants represent novel tools that could be used to further investigate the immunomodulatory properties of sialylated CPSs. Finally, in spite of common CPS structural characteristics and similarities in the cps loci, sialic acid exerts differential control of CPS expression by S. suis and GBS.

IRF-8 regulates expansion of myeloid-derived suppressor cells and Foxp3+ regulatory T cells and modulates Th2 immune responses to gastrointestinal nematode infection

Interferon regulatory factor-8 (IRF-8) is critical for Th1 cell differentiation and negatively regulates myeloid cell development including myeloid-derived suppressor cells (MDSC). MDSC expand during infection with various pathogens including the gastrointestinal (GI) nematode Heligmosomoides polygyrus bakeri (Hpb). We investigated if IRF-8 contributes to Th2 immunity to Hpb infection. Irf8 expression was down-regulated in MDSC from Hpb-infected C57BL/6 (B6) mice. IRF-8 deficient Irf8^-/- and BXH-2 mice had significantly higher adult worm burdens than B6 mice after primary or challenge Hpb infection. During primary infection, MDSC expanded to a significantly greater extent in mesenteric lymph nodes (MLN) and spleens of Irf8^-/- and BXH-2 than B6 mice. CD4⁺GATA3⁺ T cells numbers were comparable in MLN of infected B6 and IRF-8 deficient mice, but MLN cells from infected IRF-8 deficient mice secreted significantly less parasite-specific IL-4 ex vivo. The numbers of alternatively activated macrophages in MLN and serum levels of Hpb-specific IgG1 and IgE were also significantly less in infected Irf8^-/- than B6 mice. The frequencies of antigen-experienced CD4⁺CD11a^hiCD49d^hi cells that were CD44^hiCD62L^- were similar in MLN of infected Irf8^-/- and B6 mice, but the proportions of CD4⁺GATA3⁺ and CD4⁺IL-4⁺ T cells were lower in infected Irf8^-/- mice. CD11b⁺Gr1⁺ cells from naïve or infected Irf8^-/- mice suppressed CD4⁺ T cell proliferation and parasite-specific IL-4 secretion in vitro albeit less efficiently than B6 mice. Surprisingly, there were significantly more CD4⁺ T cells in infected Irf8^-/- mice, with a higher frequency of CD4⁺CD25⁺Foxp3⁺ T (Tregs) cells and significantly higher numbers of Tregs than B6 mice. In vivo depletion of MDSC and/or Tregs in Irf8^-/- mice did not affect adult worm burdens, but Treg depletion resulted in higher egg production and enhanced parasite-specific IL-5, IL-13, and IL-6 secretion ex vivo. Our data thus provide a previously unrecognized role for IRF-8 in Th2 immunity to a GI nematode.

We investigated if IRF-8, which is critical for Th1 immunity and negatively regulates myeloid cell development including MDSC, contributes to Th2 immunity to the gastrointestinal nematode Heligmosomoides polygyrus bakeri (Hpb). Irf8 expression was down-regulated in MDSC from infected C57BL/6 (B6) mice. Hpb-infected IRF-8 deficient mice had significantly higher adult worm burdens than B6 mice. There were significantly more MDSC, fewer alternatively activated macrophages, lower serum levels of Hpb-specific antibodies in infected IRF-8 deficient than B6 mice, and MLN cells from infected IRF-8 deficient mice secreted less parasite-specific IL-4 ex vivo. There were similar frequencies of antigen-experienced CD4⁺CD11a^hiCD49d^hi T cells in MLN that were CD44^hiCD62L^- in infected Irf8^-/- and B6 mice, but lower proportions of CD4⁺GATA3⁺ and CD4⁺IL-4⁺ T cells in Irf8^-/- mice. Infected Irf8^-/- mice had a higher frequency of CD4⁺Foxp3⁺ T (Tregs) cells and significantly higher numbers of Tregs compared to infected B6 mice. MDSC from infected Irf8^-/- mice suppressed CD4⁺ T cell effector functions in vitro albeit less efficiently than B6 mice. Treg and/or MDSC depletion did not affect adult worm burdens in infected Irf8^-/- mice, but Treg depletion partially restored Th2 cytokine responses. These data highlight the importance of IRF-8 in Th2 immunity to Hpb infection.

Type I Interferon Induced by Streptococcus suis Serotype 2 is Strain-Dependent and May Be Beneficial for Host Survival

Streptococcus suis serotype 2 is an important porcine bacterial pathogen and emerging zoonotic agent mainly responsible for sudden death, septic shock, and meningitis, with exacerbated inflammation being a hallmark of the infection. However, serotype 2 strains are genotypically and phenotypically heterogeneous, being composed of a multitude of sequence types (STs) whose virulence greatly varies: the virulent ST1 (Eurasia), highly virulent ST7 (responsible for the human outbreaks in China), and intermediate virulent ST25 (North America) are the most important worldwide. Even though type I interferons (IFNs) are traditionally associated with important antiviral functions, recent studies have demonstrated that they may also play an important role during infections with extracellular bacteria. Upregulation of IFN-β levels was previously observed in mice following infection with this pathogen. Consequently, the implication of IFN-β in the S. suis serotype 2 pathogenesis, which has always been considered a strict extracellular bacterium, was evaluated using strains of varying virulence. This study demonstrates that intermediate virulent strains are significantly more susceptible to phagocytosis than virulent strains. Hence, subsequent localization of these strains within the phagosome results in recognition of bacterial nucleic acids by Toll-like receptors 7 and 9, leading to activation of the interferon regulatory factors 1, 3, and 7 and production of IFN-β. Type I IFN, whose implication depends on the virulence level of the S. suis strain, is involved in host defense by participating in the modulation of systemic inflammation, which is responsible for the clearance of blood bacterial burden. As such, when induced by intermediate, and to a lesser extent, virulent S. suis strains, type I IFN plays a beneficial role in host survival. The highly virulent ST7 strain, however, hastily induces a septic shock that cannot be controlled by type I IFN, leading to rapid death of the host. A better understanding of the underlying mechanisms involved in the control of inflammation and subsequent bacterial burden could help to develop control measures for this important porcine and zoonotic agent.

Direct and correlated responses to selection in two lines of rabbits selected for feed efficiency under ad libitum and restricted feeding: III. Digestion and excretion of nitrogen and minerals

Two rabbit lines have been created to result in better feed efficiency: the ConsoResidual line was selected for a lower residual feed intake under ad libitum feeding, and the ADGrestrict line was selected for higher ADG under restricted feeding (-20% of ad libitum). The present study aimed to analyze the digestion and excretion of N and minerals from 29 to 63 d of age of these 2 lines compared with an unselected control line (G0) under 2 feeding levels (ad libitum or restricted). The ADGrestrict line had greater digestibility compared with G0 (+1.3% for OM and N; < 0.05), and the ConsoResidual line had intermediate values. There was no genetic line effect on the digestibility of N and P and on minerals concentrations (P, Zn, and Cu) in the feces and in the urine. The N balance was improved for the 2 selected lines (+5%; < 0.05), leading to a reduced N output through the feces (0.06 g/d compared with G0; < 0.001) and the urine (-0.07 g/d; < 0.05) and to an improved N retention ratio (+3% compared with G0). Over the whole fattening period (d 29-63), significant differences were observed among lines only when fed ad libitum, with 13% greater DM fecal output and 5% greater N fecal output for G0. The N excretion in urine was 2 g less in the 2 selected lines, leading to a reduction of total N release of 4.4 g (compared with G0). The P excretion in feces (12 g) or urine (0.1 g) did not differ among the 3 lines. Over the whole fattening period and for ad libitum-fed rabbits, the 5% improvement in feed efficiency ( < 0.01) for the 2 selected lines corresponded to 400 g less feed intake (-8%) and to 20 g less N intake. The fecal excretion of the ADGrestrict and ConsoResidual lines were reduced by 200 g DM ( < 0.01), corresponding to 417 g fresh matter and 5 g of N. The excretion in minerals (P, Zn, and Cu) was not affected by the line. The feeding level strongly reduced the fecal and urine outputs (-50 and -60%, respectively; < 0.001). Higher digestibility coefficients ( < 0.001) were found in restricted-fed rabbits for OM (+6%), N (+8%), and P (+11%). The N balance was substantially improved by the restriction, with 40% less total (feces + urine) N excretion ( < 0.001). The P balance was improved by the restriction (0.469 vs. 0.360). Over the fattening period, the P fecal output was 37% less (-6 g) with 24% less feed intake and the Zn and Cu outputs were reduced by 27 (-130 mg) and 29% (-30 mg), respectively.