Immunization routes in cattle impact the levels and neutralizing capacity of antibodies induced against S. aureus immune evasion proteins

Influenza A virus in dairy cattle: infection biology and potential mammary gland-targeted vaccines

Influenza, a major "One Health" threat, has gained heightened attention following recent reports of highly pathogenic avian influenza in dairy cattle and cow-to-human transmission in the USA. This review explores general aspects of influenza A virus (IAV) biology, its interactions with mammalian hosts, and discusses the key considerations for developing vaccines to prevent or curtail IAV infection in the bovine mammary gland and its spread through milk.

Investigating the Immunomodulatory Effects of Antigenic PLGA Nanoparticles and Nutritional Synergy in Caenorhabditis elegans

This study explores the significance of antigenic nanoformulation in immunomodulation and in the interplay between immune response and nutrition. The work involves the development of a polylactic-co-glycolic acid (PLGA) biopolymer-based nanoparticle with immunogenic inclusions derived from Staphylococcus aureus cell wall and membrane (CWM) through a double emulsion method followed by their physio-chemical characterization and in vivo assessment in Caenorhabditis elegans (C. elegans). The prepared nanoparticles were monodispersed in nature and exhibited a diameter of ~ 25 nm with stable colloidal nature and a zeta potential of - 25 ± 2 mV. The inclusion release and carrier degradation profiling revealed controlled and steady kinetics supporting the sustained availability of the encapsulated payload. The immunomodulatory studies conducted in C. elegans revealed that the expression of the stress indicator gene viz., sodh-1 was significantly upregulated in the CWM-treated worms and was notably reduced in the worms treated with the nanoformulation indicative of the slow release of the antigen which does not trigger untoward stress responses. In contrast, the expression of host defense genes viz., clec-7, ilys-3, igg-1, and cyp-37B1 in response to the CWM treatment was found to be downregulated, while for the nanoformulation treatment, the extent of downregulation was relatively lesser. A notable observation emerged as these genes, previously downregulated, exhibited a significant upsurge when the nutritional supplementation was amplified. This highlighted the profound influence of nutrition in fine-tuning the immune responses. Our data offers insights that could pave the way for further research in designing nutritional strategies to augment immunomodulatory interventions, as well as advocate for nanoparticle-based immunomodulatory approaches to prevent immune stress.

Presence of antibodies against Mycobacterium avium subspecies paratuberculosis in Brazilian high-producing dairy herds

This study aimed to determine the presence of antibodies against Mycobacterium avium subspecies paratuberculosis (MAP) in high-producing dairy cows, the presence of the pathogen in the feces, and the risk factors associated with the disease. Blood and fecal samples were collected from 708 dairy cows over 2 years from 54 herds located in five municipalities of Paraná, Brazil. The serum samples were evaluated for the presence of antibodies against MAP using enzyme-linked immunosorbent assay (ELISA). Fecal samples from 100 cows (69 seropositive and 31 seronegative) were assessed using real-time PCR (qPCR) for IS900 of MAP. The herd prevalence of antibodies against MAP was 61.1% (33/54; 95% CI 46.88-74.08), ranging from 12.5 to 80% across the municipalities, and the prevalence in the animals was 9.8% (69/708; 95% CI 7.77-12.15); it ranged from 0 to 87.5% per herd. Only one of the 69 (1.45%) fecal samples from the seropositive cows was positive for the qPCR. The factors associated with the occurrence of paratuberculosis in herds were the use of compost barn system and the type of bed, whereas only the type of bed was associated with the infection of cows. The only risk factor (OR = 2.45; 95% CI 1.03-5.85) associated with the occurrence of paratuberculosis was the introduction of animals purchased from other dairy farms. The prevalence of active infection was low; however, our results demonstrate the presence of MAP in high-producing dairy herds in Paraná state, Brazil.

Invited review: A critical appraisal of mastitis vaccines for dairy cows

Infections of the mammary gland remain a frequent disease of dairy ruminants that negatively affect animal welfare, milk quality, farmer serenity, and farming profitability and cause an increase in use of antimicrobials. There is a need for efficacious vaccines to alleviate the burden of mastitis in dairy farming, but this need has not been satisfactorily fulfilled despite decades of research. A careful appraisal of past and current research on mastitis vaccines reveals the peculiarities but also the commonalities among mammary gland infections associated with the major mastitis pathogens Escherichia coli, Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae, or Streptococcus dysgalactiae. A major pitfall is that the immune mechanisms of effective protection have not been fully identified. Until now, vaccine development has been directed toward the generation of antibodies. In this review, we drew up an inventory of the main approaches used to design vaccines that aim at the major pathogens for the mammary gland, and we critically appraised the current and tentative vaccines. In particular, we sought to relate efficacy to vaccine-induced defense mechanisms to shed light on some possible reasons for current vaccine shortcomings. Based on the lessons learned from past attempts and the recent results of current research, the design of effective vaccines may take a new turn in the years to come.

Maintaining Optimal Mammary Gland Health and Prevention of Mastitis

In dairy industry, quality of produced milk must be more important than quantity without a high somatic cells count (SCC) or pathogens causing mastitis of dairy cows and consumer diseases. Preserving the good health of dairy cows is a daily challenge for all involved in primary milk production. Despite the increasing level of technological support and veterinary measures, inflammation of the mammary gland-mastitis, is still one of the main health problems and reasons for economic losses faced by cow farmers. The mammary gland of high-yielding dairy cows requires making the right decisions and enforcing the proper measures aimed at minimizing external and internal factors that increase the risk of intramammary infection. Due to the polyfactorial nature of mastitis related to its reduction, the effectiveness of commonly used antimastitis methods tends to be limited and therefore it is necessary to find the areas of risk in udder health programs and monitoring systems. Only by implementing of complete udder health programs should be accompanied by research efforts to further development these complete udder health control. The present review analyses the current knowledge dealing with damping and prevention of mastitis include SCC control, proper nutrition, housing and management, milking and drying as practiced in dairy farming conditions. This information may help to improve the health of the mammary gland and the welfare of the dairy cows as well as the production of safe milk for consumers.

Staphylococcus aureus-specific IgA antibody in milk suppresses the multiplication of S. aureus in infected bovine udder

Background

Bovine mastitis caused by Staphylococcus aureus (S. aureus) is extremely difficult to control and new methods for its prevention and management are required. Nasal vaccines may prevent initial bovine mastitis infection caused by S. aureus. However, limited information is available regarding induction of mucosal immune response through nasal immunization with antigen and its suppression of S. aureus multiplication during bovine mastitis. This study sought to investigate whether induction of immunoglobulin A (IgA) in milk by nasal immunization could suppress multiplication of S. aureus in the bovine udder.

Results

Nasal immunization with formalin-killed S. aureus conjugated with a cationic cholesteryl-group-bearing pullulan-nanogel was performed. Anti-S. aureus-specific IgA antibodies were significantly more abundant in the milk of immunized cows than in non-immunized animals (P < 0.05). S. aureus counts in the quarter were negative in both non-immunized and nasal-immunized cows 1 week after mock infusion. In S. aureus-infused quarters, S. aureus multiplication was significantly suppressed in immunized compared with non-immunized cows (P < 0.05). Furthermore, a significant negative correlation was found between S. aureus-specific IgA antibodies and S. aureus counts in infused quarters of both non-immunized and nasal-immunized cows (r = − 0.811, P < 0.01).

Conclusion

In conclusion, the present study demonstrates that S. aureus-specific IgA antibodies in milk successfully suppressed the multiplication of S. aureus in infected bovine udders. Although the exact mechanism explaining such suppressive effect remains to be elucidated, nasal vaccines that can induce humoral immunity may help prevent initial infection with S. aureus and the onset of bovine mastitis.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2025-3) contains supplementary material, which is available to authorized users.

Immunization of young heifers with staphylococcal immune evasion proteins before natural exposure to Staphylococcus aureus induces a humoral immune response in serum and milk

Background

Staphylococcus aureus, a leading cause of mastitis in dairy cattle, causes severe mastitis and/or chronic persistent infections with detrimental effects on the cows’ wellbeing, lifespan and milk production. Despite years of research there is no effective vaccine against S. aureus mastitis. Boosting of non-protective pre-existing immunity to S. aureus, induced by natural exposure to S. aureus, by vaccination may interfere with vaccine efficacy. The aim was to assess whether experimental immunization of S. aureus naïve animals results in an immune response that differs from immunity following natural exposure to S. aureus.

Results

First, to define the period during which calves are immunologically naïve for S. aureus, Efb, LukM, and whole-cell S. aureus specific serum antibodies were measured in a cohort of newborn calves by ELISA. Rising S. aureus specific antibodies indicated that from week 12 onward calves mounted an immune response to S. aureus due to natural exposure. Next, an experimental immunization trial was set up using 8-week-old heifer calves (n = 16), half of which were immunized with the immune evasion molecules Efb and LukM. Immunization was repeated after one year and before parturition and humoral and cellular immunity specific for Efb and LukM was determined throughout the study. Post-partum, antibody levels against LukM and EfB were significantly higher in serum, colostrum and milk in the experimentally immunized animals compared to animals naturally exposed to S. aureus. LukM specific IL17a responses were also significantly higher in the immunized cows post-partum.

Conclusions

Experimental immunization with staphylococcal immune evasion molecules starting before natural exposure resulted in significantly higher antibody levels against Efb and LukM around parturition in serum as well as the site of infection, i.e. in colostrum and milk, compared to natural exposure to S. aureus. This study showed that it is practically feasible to vaccinate S. aureus naïve cattle and that experimental immunization induced a humoral immune response that differed from that after natural exposure only.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1765-9) contains supplementary material, which is available to authorized users.

Symposium review: Features of Staphylococcus aureus mastitis pathogenesis that guide vaccine development strategies

Bovine mastitis affects animal health and welfare and milk production and quality, and it challenges the economic success of dairy farms. Staphylococcus aureus is one of the most commonly found pathogens in clinical mastitis but it also causes subclinical, persistent, and difficult-to-treat intramammary infections. Because of the failure of conventional antibiotic treatments and increasing pressure and concern from experts and consumers over the use of antibiotics in the dairy industry, many attempts have been made over the years to develop a vaccine for the prevention and control of Staph. aureus intramammary infections. Still, no commercially available vaccine formulation demonstrates sufficient protection and cost-effective potential. Multiple factors account for the lack of protection, including inadequate vaccine targets, high diversity among mastitis-provoking strains, cow-to-cow variation in immune response, and a failure to elicit an immune response that is appropriate for protection against a highly complex pathogen. The purpose of this review is to summarize key concepts related to the pathogenesis of Staph. aureus, and its interaction with the host, as well as to describe recent vaccine development strategies for prevention and control of Staph. aureus mastitis.

Periodic vicissitudes of different concentrations of a developed prototype killed S. aureus mastitis vaccine on immune modulators, mediators and immunoglobulins in cows

Mastitis is the inflammation of the mammary gland due to microbial infiltration causing a reduced mammary function. This study aims at developing a vaccine using Malaysian local isolate of Staphylococcus aureus and evaluating serum amyloid A, Interleukin-10, IgM and IgG responses periodically. Four bacterin concentrations (10⁶, 10⁷, 10⁸ and 10⁹ cfu/ml of the local isolate of S. aureus) were adjuvanted with aluminium potassium sulphate. Thirty cows grouped into 4 treatment groups (G-) were vaccinated (2 ml) intramuscularly, with a fifth G-A as control. The mean concentration (MC) of serum amyloid A (SAA) was significantly different (sig-d) (p ˂ 0.05) in G-D at 0 h post vaccination (PV), 3 h PV, 24 h PV, weeks 1, 2, 3 and 4 PV (6-, 15-, 5-, 12-, 11-, 4- and 11-fold increased (FI) respectively). The MC of serum amyloid A was also sig-d in G-E at 0 h PV, weeks 1, 2 and 4 PV (3, 8, 5 and 8 FI respectively). The MC of IL-10 was sig-d in G-D and C at 3 h PV and week 2 PV (5 and 2 FI respectively). The IgM MC was sig-d in G-B and C at 3 h PV (5 and 6 FI respectively), at 24 h PV (5 and 9 FI respectively), at week 3 PV(2 and 2 FI respectively) and week 4 PV (3 and 4 FI respectively). The MC of IgG was sig-d in G-E at 0 h, 3 h and week 3 PV(5, 6 and 2 FI respectively) and in G-D at weeks 1-4 (3, 3, 3 and 5 FI respectively). In conclusion, elevated levels of SAA, IgG and IL-10 in G-D(10⁸) informed our choice of best dosage which can be used to evoke immunity in cows.

Immunological characteristics of Mycobacterium tuberculosis subunit vaccines immunized through different routes

Tuberculosis is chronic infectious disease caused by Mycobacterium tuberculosis (M.tb) that is prevalent worldwide. Several specific antigens, such as Antigen 85B (Ag85B) and 6 kDa early secretory antigenic target (ESAT-6) protein of M.tb, are listed as some of the candidate subunit vaccines against M.tb. ESAT-6, as a virulent factor and differential gene in M.tb, shows insufficient immunogenicity in animal model. In order to investigate the ways to improve the immunogenicity of ESAT-6, we immunized ESAT-6 by subcutaneous and intramuscular routes with different adjuvants. We found that ESAT-6 immunized alone did not induce significant humoral immunity in both immunization routes. However, subcutaneous immunization of ESAT-6 plus incomplete Freund's adjuvant can induce a significant humoral immune response, enhanced proliferation and elevated secretion of IFN-γ from splenocytes. Intramuscular immunization of ESAT-6 plus adjuvant aluminum salt or poly(I:C) did not enhance humoral and cellular immune responses. Therefore, it is concluded that immunization of ESAT-6 subcutaneously plus incomplete Freund's adjuvant induces stronger humoral and cellular immune responses, which can be considered of ESAT-6 as a subunit vaccine in further research against tuberculosis.

Immunogenicity of a Staphylococcus aureus-cholera toxin A2/B vaccine for bovine mastitis

Staphylococcus aureus causes a chronic, contagious disease of the udder, or mastitis, in dairy cows. This infection is often refractory to antibiotic treatment, and has a significant economic impact on milk production worldwide. An effective vaccine to prevent S. aureus mastitis would improve animal health, reduce antibiotic dependence and inform human vaccine approaches. The iron-regulated surface determinant A (IsdA) and clumping factor A (ClfA) are conserved S. aureus extracellular-matrix adhesins and target vaccine antigens. Here we report the results of two bovine immunogenicity trials using purified IsdA and ClfA-cholera toxin A₂/B chimeras (IsdA-CTA₂/B and ClfA-CTA₂/B). Cows were intranasally inoculated with IsdA-CTA₂/B + ClfA-CTA₂/B at dry off and followed for 70 days. Trial 1 utilized three groups with one or two booster doses at a total concentration of 600 or 900 μg. Trial 2 utilized two groups with one booster at a total concentration of 1200 μg. Humoral immune responses in serum and milk were examined by ELISA. Responses in serum were significant between groups and provide evidence of antigen-specific IgG induction after vaccination in both trials. Cellular proliferation was detected by flow cytometry using antigen-stimulated PBMCs from day 60 of Trial 2 and revealed an increase in CD4+ T cells from vaccinated cows. IsdA and ClfA stimulation induced IL-4 expression, but not IFN-γ or IL-17, in PBMCs from day 60 as determined by cytokine expression analysis. Opsonophagocytosis of S. aureus confirmed the functional in vitro activity of anti-IsdA antibodies from Trial 2 serum and milk. The vaccine was well tolerated and safe, and results support the potential of mucosally-delivered CTA₂/B chimeras to protect cows from mastitis caused by S. aureus.

The antibody response in the bovine mammary gland is influenced by the adjuvant and the site of subcutaneous vaccination

Intramammary infections in cattle resulting in mastitis have detrimental effects on cows' well-being, lifespan and milk production. In the host defense against S. aureus mastitis antibodies are thought to play an important role. To explore potential ways to increase antibody titers in the bovine mammary gland the effects of various adjuvants on the magnitude, isotype, and neutralizing capacity of antibodies produced following subcutaneous vaccine administration at different immunization sites were analyzed. In this study, α-toxoid was used as a model antigen and formulated in three different alum-based adjuvants: Alum-Saponin, Alum-Oil, and Alum-Saponin-Oil. Vaccines were administered near the suspensory ligament of the udder or in the lateral triangular area of the neck. At both immunization sites, immunization with α-toxoid in Alum-Saponin-Oil resulted in higher specific antibody titers in milk and serum as compared with Alum-Oil and Alum-Saponin, without favoring an IgG1, IgG2, or IgA response. Furthermore, the neutralizing capacity of milk serum and serum following immunization near the udder and in the neck was higher when Alum-Saponin-Oil was used as adjuvant compared with Alum-Oil and Alum-Saponin. Prime immunizations near the udder effectively increased both antibody isotype titers and neutralization titers, while prime plus boost immunizations were required to induce similar effects following immunization in the neck. Results indicate that subcutaneous administration of an Alum-Saponin-Oil based vaccine near the udder could be further explored for the development of a one-shot vaccination strategy to efficiently increase intramammary antibody responses.

Identification of a novel mechanism of action of bovine IgG antibodies specific for Staphylococcus aureus

Staphylococcus aureus is a major pathogen that causes subclinical mastitis associated with huge economic losses to the dairy industry. A few vaccines for bovine mastitis are available, and they are expected to induce the production of S. aureus-specific antibodies that prevent bacterial adherence to host cells or promote opsonization by phagocytes. However, the efficacy of such vaccines are still under debate; therefore, further research focusing on improving the current vaccines by seeking additional mechanisms of action is required to reduce economic losses due to mastitis in the dairy industry. Here, we generated S. aureus-specific bovine IgG antibodies (anti-S. aureus) that directly inhibited bacterial growth in vitro. Inhibition depended on specificity for anti-S. aureus, not the interaction between Protein A and the fragment crystallizable region of the IgG antibodies or bacterial agglutination. An in vitro culture study using S. aureus strain JE2 and its deletion mutant JE2ΔSrtA, which lacks the gene encoding sortase A, revealed that the effect of anti-S. aureus was sortase-A-independent. Sortase A is involved in the synthesis of cell-wall-associated proteins. Thus, other surface molecules, such as membrane proteins, cell surface polysaccharides, or both, may trigger the inhibition of bacterial growth by anti-S. aureus. Together, our findings contribute insights into developing new strategies to further improve the available mastitis vaccine by designing a novel antigen on the surface of S. aureus to induce inhibitory signals that prevent bacterial growth.

LukMF' is the major secreted leukocidin of bovine Staphylococcus aureus and is produced in vivo during bovine mastitis

Staphylococcus aureus is a major human and animal pathogen and a common cause of mastitis in cattle. S. aureus secretes several leukocidins that target bovine neutrophils, crucial effector cells in the defence against bacterial pathogens. In this study, we investigated the role of staphylococcal leukocidins in the pathogenesis of bovine S. aureus disease. We show that LukAB, in contrast to the γ-hemolysins, LukED, and LukMF′, was unable to kill bovine neutrophils, and identified CXCR2 as a bovine receptor for HlgAB and LukED. Furthermore, we assessed functional leukocidin secretion by bovine mastitis isolates and observed that, although leukocidin production was strain dependent, LukMF′ was most abundantly secreted and the major toxin killing bovine neutrophils. To determine the role of LukMF′ in bovine mastitis, cattle were challenged with high (S1444) or intermediate (S1449, S1463) LukMF′-producing isolates. Only animals infected with S1444 developed severe clinical symptoms. Importantly, LukM was produced in vivo during the course of infection and levels in milk were associated with the severity of mastitis. Altogether, these findings underline the importance of LukMF′ as a virulence factor and support the development of therapeutic approaches targeting LukMF′ to control S. aureus mastitis in cattle.

Serum and colostral antibody production in cows immunized with recombinant human tumor necrosis factor

The use of hyper-immune bovine colostrum as a human therapeutic platform is an emerging technology with potential to deliver the efficacy of antibody therapeutics with the convenience and safety of oral or topical application. It is necessary to understand how the bovine immune system responds to immunization with foreign proteins, both in terms of the serum antibody response and the transfer of antigen-specific antibodies into the colostrum to enable efficient large-scale production of therapeutic antibodies. We have immunized 25 cows with recombinant human tumor necrosis factor (rhTNF) and measured the levels of rhTNF-specific antibodies in the serum and colostrum of these animals. We observed a decline of 84±9% in serum IgG1 concentrations in the final weeks of pregnancy that presumably reflects rapid transport of IgG1 into colostrum. The serum IgG2 levels remained constant, such that the serum IgG1 to IgG2 ratio was 1:20 at parturition. We observed substantial animal-to-animal variability in the levels of anti-rhTNF antibodies in both serum and colostrum samples. In particular, a subset of 4 cows had extraordinarily high colostral anti-rhTNF antibody production. Only a weak correlation was found between the peak serum anti-rhTNF activity and the colostral anti-rhTNF activity in these animals. The 4 cows with high colostral anti-rhTNF activities trended toward higher serum IgG1 loss relative to average colostral anti-rhTNF producers, but this difference was not statistically significant in this small sample. The high-anti-rhTNF-producing cows also exhibited a greater proportion of rhTNF-specific antibodies that bound to bovine IgG1- and IgG2-specific detection antibodies relative to the total anti-rhTNF immunoglobulin population. This finding suggests that the isotype distribution of the anti-rhTNF response is varied between individuals and genetic or environmental factors may increase the yield of antigen-specific colostral antibodies.

Reisolation of Staphylococcus aureus from bovine milk following experimental inoculation is influenced by fat percentage and specific immunoglobulin G1 titer in milk

The associations of management parameters, herd characteristics, and individual cow factors with bovine mastitis have been subject of many studies. The present study aimed to evaluate the association between milk composition parameters, including fat, protein, lactose, urea, and specific immunoglobulin levels, at the time of experimental bacterial inoculation of the mammary gland and subsequent shedding dynamics of Staphylococcus aureus. Sixty-eight cows were experimentally infected with S. aureus and closely monitored for 3 wk. Mixed model analyses were used to determine the influence of management and herd characteristics (farm and experimental group), individual cow factors (days in milk, milk yield, and quarter position), and a challenge-related parameter (inoculation dose) in combination with either the milk components fat, protein, lactose and urea, or the S. aureus-specific antibody isotype titers at the time of bacterial inoculation, on the number of S. aureus reisolated from milk after inoculation. A positive association was observed between the milk fat percentage and the number of S. aureus reisolated from quarter milk, and a negative relationship between the S. aureus-specific IgG1 titer in milk and the number of S. aureus. These findings should be considered in the development of a vaccine against S. aureus-induced bovine mastitis.

Staphylococcal Immune Evasion Proteins: Structure, Function, and Host Adaptation

Staphylococcus aureus is a successful human and animal pathogen. Its pathogenicity is linked to its ability to secrete a large amount of virulence factors. These secreted proteins interfere with many critical components of the immune system, both innate and adaptive, and hamper proper immune functioning. In recent years, numerous studies have been conducted in order to understand the molecular mechanism underlying the interaction of evasion molecules with the host immune system. Structural studies have fundamentally contributed to our understanding of the mechanisms of action of the individual factors. Furthermore, such studies revealed one of the most striking characteristics of the secreted immune evasion molecules: their conserved structure. Despite high-sequence variability, most immune evasion molecules belong to a small number of structural categories. Another remarkable characteristic is that S. aureus carries most of these virulence factors on mobile genetic elements (MGE) or ex-MGE in its accessory genome. Coevolution of pathogen and host has resulted in immune evasion molecules with a highly host-specific function and prevalence. In this review, we explore how these shared structures and genomic locations relate to function and host specificity. This is discussed in the context of therapeutic options for these immune evasion molecules in infectious as well as in inflammatory diseases.