Laboratory automation, informatics, and artificial intelligence: current and future perspectives in clinical microbiology

Clinical diagnostic laboratories produce one product-information-and for this to be valuable, the information must be clinically relevant, accurate, and timely. Although diagnostic information can clearly improve patient outcomes and decrease healthcare costs, technological challenges and laboratory workflow practices affect the timeliness and clinical value of diagnostics. This article will examine how prioritizing laboratory practices in a patient-oriented approach can be used to optimize technology advances for improved patient care.

Role of Nucleocapsid Protein Antigen Detection for Safe End of Isolation of SARS-CoV-2 Infected Patients with Long Persistence of Viral RNA in Respiratory Samples

Background. In SARS-CoV-2 infection, viral RNA may persist in respiratory samples for several weeks after the resolution of symptoms. Criteria to assess the end of infectivity are not unequivocally defined. In some countries, time from diagnosis is the unique criterion used, in addition to symptom cessation. This study evaluates the role of the Lumipulse^® Antigen Assay (LAA) for the safe end of isolation of patients ≥21 days after the diagnosis of infection. Methods. A total of 671 nasopharyngeal swabs from patients diagnosed with infection at least 21 days before were assessed by RT-PCR and LAA, and the role of LAA in predicting the absence of infectivity was evaluated by virus cell culture. Results. Viable virus was present in 10/138 cultured samples. Eight out of ten infective patients suffered from a concomitant disease, predisposing them to long-term shedding of infective virus. In particular, infectious virus was isolated from 10/20 RT-PCR+/LAA+ cultured samples, whereas no viable virus was found in all 118 RT-PCR+/LAA– cultured swabs. LLA and RT-PCR agreed in 484/671 (72.1%) samples, with 100% and 26.7% concordance in RT-PCR negative and positive samples, respectively. Conclusions. Viable virus can be found ≥21 days after diagnosis in immunocompromised or severely ill patients. LAA better than RT-PCR predicts non-infectivity of patients and can be safely used to end isolation in cases with long persistence of viral RNA in the respiratory tract.

Accuracy and Impact on Patient Management of New Tools for Diagnosis of Sepsis: Experience with the T2 Magnetic Resonance Bacteria Panel

The rapid and accurate identification of pathogens responsible for sepsis is essential for prompt and effective antimicrobial therapy. Molecular technologies have been developed to detect the most common causative agents, with high sensitivity and short time to result (TTR). T2 Bacteria Panel (T2), based on a combination of PCR and T2 magnetic resonance, can identify directly in blood samples Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecium, and Acinetobacter baumannii pathogens. This study evaluates the role of T2 in the diagnosis of sepsis and its impact on patient management, specifically in terms of TTR and the switch from empirical to directed therapy, comparing results of blood culture (BC) and T2 assay in 82 patients with sepsis. T2 significantly improved the detection of the causative agents of sepsis. For pathogens included in the panel, T2 sensitivity was 100% (95% CI 86.3–100.0), significantly higher than that of BC (54.8%, 95% CI 36.0–72.7). The TTR (median, IQR) of positive T2 (3.66 h, 3.59–4.31) was significantly shorter than that of the positive BC (37.58 h, 20.10–47.32). A significant reduction in the duration of empiric therapy and an increase in the percentage of patients with switched therapy was observed in patients with a positive T2 result. In conclusion, T2 can shorten and improve the etiological diagnosis of sepsis with a positive impact on patient management.

QuantiFERON-TB and tuberculin skin test in patients with active tuberculosis: the experience of a single medium-sized Italian University Hospital

Interferon-γ releasing assays (IGRAs) are currently widely employed in the initial work up of Mycobacterium tuberculosis infection, as well as in suspected tuberculosis (TB). These assays are commonly utilized over the Tuberculin Skin Test (TST) in high resource and low TB burden settings, despite the unclear benefits shown in such contexts. The debate on the use of TST and IGRAs is of current interest also in Italy due to the increasing presence of immigrants from countries with a high incidence of TB and the rising attention of health care institutions to economic costs. The aim of this study was to compare QuantiFERON-TB (QFT) and TST results in active TB. We evaluated QFT results and TST reactions from 245 consecutive patients having both tests, registered among 411 patients admitted for TB at the Infectious Disease Clinic, Department of Medicine of the University of Perugia (Italy). We compared the rates of positive QFT and TST tests and noted no statistically significant differences overall or in relation to age, gender, HIV status and TB localization. Among foreign-born patients with confirmed TB, we observed a lower rate of positive TST results. The results of our study indicated that both QFT and TST can be used in the work up of TB having special attention when evaluating foreign-born patients.

Evaluation of Lumipulse® G SARS-CoV-2 antigen assay automated test for detecting SARS-CoV-2 nucleocapsid protein (NP) in nasopharyngeal swabs for community and population screening

Objectives

To compare the Lumipulse® SARS-CoV-2 antigen test with the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) for diagnosis of SARS-CoV-2 infection and to evaluate its role in screening programs.

Methods

Lumipulse® SARS-CoV-2 antigen assay was compared with the gold standard RT-PCR test in a selected cohort of 226 subjects with suspected SARS-CoV-2 infection, and its accuracy was evaluated. Subsequently, the test was administered to a real-life screening cohort of 1738 cases. ROC analysis was performed to explore test features and cutoffs. All tests were performed in the regional reference laboratory in Umbria, Italy.

Results

A 42.0% positive result at RT-PCR was observed in the selected cohort. The Lumipulse® system showed 92.6% sensitivity (95% CI 85.4–97.0%) and 90.8% specificity (95% CI 84.5–95.2%) at 1.24 pg/mL optimal cutoff. In the screening cohort, characterized by 5.2% prevalence of infection, Lumipulse® assay showed 100% sensitivity (95% CI 96.0–100.0%) and 94.8% specificity (95% CI 93.6–95.8%) at 1.645 pg/mL optimal cutoff; the AUC was 97.4%, NPV was 100% (95% CI 99.8–100.0%) and PPV was 51.1% (95% CI 43.5–58.7%).

Conclusions

The Lumipulse® SARS-CoV-2 antigen assay can be safely employed in the screening strategies in small and large communities and in the general population.

Accelerate Pheno™ blood culture detection system: a literature review

Accelerate Pheno™ (ACC) is a fully automated system providing rapid identification of a panel of bacteria and yeasts, and antimicrobial susceptibility testing of common bacterial pathogens responsible for bloodstream infections and sepsis. Diagnostic accuracy for identification ranges from 87.9 to 100%, and antimicrobial susceptibility testing categorical agreement is higher than 91%. The present review includes peer-reviewed studies on ACC published to date. Both interventional and hypothetical studies evidenced the potential positive clinical role of ACC in the management and therapy of patients with bloodstream infections and sepsis, due to the important reduction in time to report, suggesting a crucial impact on the therapeutic management of these patients, provided the presence of a hospital antimicrobial stewardship program, a 24/7 laboratory operating time and a strict collaboration between clinical microbiologist and clinician. Further prospective multicenter studies are necessary to explore the impact of this system on mortality, length of stay and spread of multidrug-resistant organisms.

Measles immunity in healthcare workers of an Italian hospital

BACKGROUND

In Italy, 4991 cases of measles were reported in 2017 and 322 involved healthcare workers (HCWs). These professionals are at high risk of infection and transmission of virus both to other hospital staff and importantly, to patients, some of whom may be at risk of severe illness and complications. According to the Italian National Immunization and Prevention Plan, all HCWs should have demonstrable evidence of immunity to measles and specific hospital surveillance is recommended. Given a recent measles outbreak recorded in Italy, which also involved HCWs, the aim of this study has been to assess the measles immunization status of the Perugia General Hospital's HCWs.

METHODS

A survey on all hospital staff was carried out, using a questionnaire to obtain information on demographic characteristics, personal history of measles and self-reported vaccination status, and offering the serological testing to HCWs who did not know their immune status.

RESULTS

Among the 1714 HCWs included in the study, 1207 (70%) were protected against measles (due to vaccination or natural infection), and 507 (30%) did not know their immune status. Of these, 461 subjects accepted a serological control, while 46 refused. Protective measles-specific IgG antibody titres were documented in 410/461 (89%) HCWs, and the percentage of immune subjects decreased with the age.

CONCLUSIONS

Our study shows that in Perugia General Hospital, 26% of HCWs under the age of 30 were not protected against measles. In Italy, campaigns promoting vaccination of HCWs are needed to prevent transmission of this infection in hospital setting.

Accelerate Pheno™ system in sepsis by Gram-negative pathogens: four months of hospital experience

This study reports our experience with the Accelerate PhenoTM system (ACC) to guide management of patients with sepsis by Gram-negative pathogens. A diagnostic workflow, based on pathogen and resistance genes detection or ACC testing, was applied to 33 patients. Clinical and microbiological data were recorded, and analysis of broad-spectrum agents sparing was performed. Antimicrobial susceptibility results by ACC were available for 28 of 33 patients (84.85%). Among 434 microorganism-antimicrobial combinations, categorical agreement was 97.93%, very major errors 0.23%, major errors 1.15%, and minor errors 0.69%. Time to report (mean ± SD) of ACC results was 27.14±6.90 h from sample collection, significantly shorter (p<0.001, Δ = 19.96 h, 95% CI: 24.71-15.22) than that of the standard method (47.10±11.92 h). A switch from empiric to targeted therapy was observed in 14 of 28 patients (50.0%), duration of empiric therapy was 37.73±19.87 h, with a saving of 5.45 piperacillin/tazobactam and 5.28 carbapenems prescribed daily doses. Considering patients in which de-escalation would have been theoretically feasible, 27.69 prescribed daily doses of piperacillin/tazobactam and 19.08 of carbapenems could had been spared, compared to standard methods. In conclusion, ACC could impact positively on the management of septic patients by Gram-negative pathogens.

Multiplex Platforms for the Identification of Respiratory Pathogens: Are They Useful in Pediatric Clinical Practice?

Respiratory tract infections (RTIs) are extremely common especially in the first year of life. Knowledge of the etiology of a RTI is essential to facilitate the appropriate management and the implementation of the most effective control measures. This perspective explains why laboratory methods that can identify pathogens in respiratory secretions have been developed over the course of many years. High-complexity multiplex panel assays that can simultaneously detect up to 20 viruses and up to four bacteria within a few hours have been marketed. However, are these platforms actually useful in pediatric clinical practice? In this manuscript, we showed that these platforms appear to be particularly important for epidemiological studies and clinical research. On the contrary, their routine use in pediatric clinical practice remains debatable. They can be used only in the hospital as they require specific equipment and laboratory technicians with considerable knowledge, training, and experience. Moreover, despite more sensitive and specific than other tests routinely used for respiratory pathogen identification, they do not offer significantly advantage for detection of the true etiology of a respiratory disease. Furthermore, knowledge of which virus is the cause of a respiratory disease is not useful from a therapeutic point of view unless influenza virus or respiratory syncytial virus are the infecting agents as effective drugs are available only for these pathogens. On the other hand, multiplex platforms can be justified in the presence of severe clinical manifestations, and in immunocompromised patients for whom specific treatment option can be available, particularly when they can be used simultaneously with platforms that allow identification of antimicrobial resistance to commonly used drugs. It is highly likely that these platforms, particularly those with high sensitivity and specificity and with low turnaround time, will become essential when new drugs effective and safe against most of the respiratory viruses will be available. Further studies on how to differentiate carriers from patients with true disease, as well as studies on the implications of coinfections and identification of antimicrobial resistance, are warranted.

Measurement and prediction of antimicrobial resistance in bloodstream infections by ESKAPE pathogens and Escherichia coli

OBJECTIVES

This study aimed to evaluate a cumulative antimicrobial resistance index (ARI) as a possible key outcome measure of antimicrobial stewardship programmes (ASPs) and a tool to predict the antimicrobial resistance (AMR) trend.

METHODS

Antimicrobial susceptibility for Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli (ESKAPEEc) pathogens recovered from blood cultures during a 5-year period (2014-2018) was analysed to obtain a cumulative ARI. For each antibiotic tested, a score of 0, 0.5 or 1 was assigned for susceptibility, intermediate resistance or resistance, respectively, and the ARI was calculated by dividing the sum of these scores by the number of antibiotics tested. Cumulative ARIs of ESKAPEEc micro-organisms were compared and a mathematical prediction model for AMR trend was obtained.

RESULTS

In total, 1858 ESKAPEEc isolates were included in the study. The cumulative ESKAPEEc mean ARI increased significantly from 0.200 ± 0.01 in 2014 to 0.276 ± 0.02 in 2018 (P < 0.001). In multivariable regression analysis, factors significantly associated with ARI ≥ 0.5 were E. faecium, K. pneumoniae, P. aeruginosa and A. baumannii infection (P < 0.001) and infection occurring after 2014 (P < 0.05). Based on the prediction model obtained, in the absence of any interventional measure, a tendency to pandrug resistance of the ESKAPEEc group could be expected in the next 8-15 years.

CONCLUSION

The ARI could be a useful tool to measure the impact of ASPs on AMR. The increasing incidence of AMR among ESKAPEEc organisms underscores the needing for ASPs.

Splenic tuberculosis in a patient with newly diagnosed advanced HIV infection

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Splenic tuberculosis (TB) is a rare clinical condition usually seen as a part of miliary TB.

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The presence of a splenic abscess without an active TB of the lung in an Italian HIV positive patient is very uncommon.

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Case reports of isolated splenic TB in which microbiological and molecular examinations have been carried out to confirm the diagnosis are rare especially in low TB prevalence areas as Italy.

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This case report may be useful when physicians are faced with differential diagnosis of splenic mass or abscess.

The extra-pulmonary tuberculosis (TB) constitutes to about 20% of all TB cases. Among extra-pulmonary form, splenic TB is very rare clinical condition especially as initial manifestation in a developed country. Diagnosis of splenic TB is challenging because it presents no specific symptoms or typical imaging findings and microbiological confirmation is not straight forward.

We describe the case of a 55 year old Italian female with advanced HIV infection whose first AIDS clinical manifestation was a TB splenic abscess.On CT, the lesion was multilocular, hypovascular, 34 mm large, and presented contrast enhancement and a spoke wheel pattern; it was initially considered a cystic formation of parasitic nature. In this patient clinical manifestations were nonspecific (nightly fever, weight loss, and fatigue); as diagnostic imaging could not pinpoint the underlying etiology, microbiological and molecular examinations of spleen abscess drainage proved pivotal for the diagnosis. The patient improved clinically with antitubercular therapy.

The rarityof splenic tuberculosis in an European patient coupled with the involvement of the spleen in isolation and outside the “miliary” setting prompted us to report this case.

Diagnostic accuracy of presepsin (sCD14-ST) and procalcitonin for prediction of bacteraemia and bacterial DNAaemia in patients with suspected sepsis

Early diagnosis and prompt targeted therapy are essential for septic patients' outcome. Procalcitonin (PCT) has been shown to predict bacteraemia and bacterial DNAaemia. Presepsin, the circulating soluble form of CD14 subtype, increases in response to bacterial infections, and is considered a new, emerging, early marker for sepsis. We evaluated the diagnostic accuracy of presepsin in predicting bacteraemia and bacterial DNAaemia in 92 patients with suspected sepsis, and we compared it with that of PCT and C-reactive protein (CRP). Presepsin median values were significantly higher in bacteraemic vs non-bacteraemic patients [1290 pg ml-1, interquartile range (IQR) 1005-2041 vs 659 pg ml-1, IQR 381-979; P<0.001] and in patients with vs patients without bacterial DNAaemia (1297 pg ml-1, IQR 1001-2046 vs 665 pg ml-1, IQR 381-940; P<0.001). Receiver operating characteristics analysis showed an area under the curve (AUC) for presepsin of 0.788 [95 % confidence interval (CI): 0.687-0.889; P<0.001] in predicting bacteraemia and of 0.777 (95 % CI: 0.676-0.878; P<0.001) in predicting bacterial DNAaemia, lower, but not significantly different, than those of PCT (0.876, P=0.12 and 0.880, P=0.07, respectively). Both biomarkers performed significantly better than CRP, which had an AUC for bacteraemia of 0.602 and for DNAaemia of 0.632 (all P values <0.05). In conclusion, in patients with suspected sepsis, presepsin and PCT showed a good diagnostic accuracy in predicting both bacteraemia and bacterial DNAaemia, superior to CRP.

Functional improvement of regulatory T cells from rheumatoid arthritis subjects induced by capsular polysaccharide glucuronoxylomannogalactan

OBJECTIVE

Regulatory T cells (Treg) play a critical role in the prevention of autoimmunity, and the suppressive activity of these cells is impaired in rheumatoid arthritis (RA). The aim of the present study was to investigate function and properties of Treg of RA patients in response to purified polysaccharide glucuronoxylomannogalactan (GXMGal).

METHODS

Flow cytometry and western blot analysis were used to investigate the frequency, function and properties of Treg cells.

RESULTS

GXMGal was able to: i) induce strong increase of FOXP3 on CD4+ T cells without affecting the number of CD4+CD25+FOXP3+ Treg cells with parallel increase in the percentage of non-conventional CD4+CD25-FOXP3+ Treg cells; ii) increase intracellular levels of TGF-β1 in CD4+CD25-FOXP3+ Treg cells and of IL-10 in both CD4+CD25+FOXP3+ and CD4+CD25-FOXP3+ Treg cells; iii) enhance the suppressive activity of CD4+CD25+FOXP3+ and CD4+CD25-FOXP3+ Treg cells in terms of inhibition of effector T cell activity and increased secretion of IL-10; iv) decrease Th1 response as demonstrated by inhibition of T-bet activation and down-regulation of IFN-γ and IL-12p70 production; v) decrease Th17 differentiation by down-regulating pSTAT3 activation and IL-17A, IL-23, IL-21, IL-22 and IL-6 production.

CONCLUSION

These data show that GXMGal improves Treg functions and increases the number and function of CD4+CD25-FOXP3+ Treg cells of RA patients. It is suggested that GXMGal may be potentially useful for restoring impaired Treg functions in autoimmune disorders and for developing Treg cell-based strategies for the treatment of these diseases.

Procalcitonin better than C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in predicting DNAemia in patients with sepsis

BACKGROUND

Procalcitonin (PCT) levels can be used to predict bacteremia and DNAemia in patients with sepsis. In this study, the diagnostic accuracy of PCT in predicting blood culture (BC) results and DNAemia, as detected by real-time PCR (RT-PCR), was compared with that of other markers of inflammation commonly evaluated in patients with suspected sepsis, such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell (WBC) count.

METHODS

A total of 571 patients for whom BC, blood RT-PCR, PCT, CRP, ESR, and WBC count were requested for laboratory diagnosis of sepsis were included in the study. Receiver operating characteristic curve analysis was performed to compare the ability of the above biomarkers to predict BC and blood RT-PCR results.

RESULTS

A total of 108 pathogens were identified by BC (79 pathogens, 14.5% positive rate) and/or RT-PCR (90 pathogens, 16.5% positive rate), after exclusion of 26 contaminated samples. The PCT areas under the curve (AUCs) in predicting BC (0.843; 95% CI 0.796-0.890; p < 0.0001) and RT-PCR (0.916; 95% CI 0.888-0.945; p < 0.0001) results were significantly greater than AUCs found for CRP, ESR, and WBC count.

CONCLUSIONS

PCT showed a better diagnostic accuracy than CRP, ESR, and WBC count in predicting DNAemia and bacteremia in patients with suspected sepsis.

Elucidating the immunological function of the Cryptococcus neoformans capsule

The encapsulated fungal pathogen Cryptococcus neoformans represents a significant agent of life-threatening infections in immunocompromised subjects. A unique characteristic of Cryptococcus species is the presence of a polysaccharide capsule, which is essential for virulence and endows Cryptococcus with potent immunoregulatory properties. This review provides an overview of the immunological properties of the principal components of C. neoformans capsule.

Acute appendicitis due to Cytomegalovirus in an apparently immunocompetent patient: a case report

Introduction

In healthy subjects, Cytomegalovirus infection can be asymptomatic or manifest as mononucleosis syndrome, but organ disease has also been reported. However, in immunocompromised patients this infection can lead to its most significant and severe disease and even mortality. When Cytomegalovirus causes a gastrointestinal tract infection, it more commonly manifests with luminal tract disease and is usually characterized by ulcerative lesions. Appendicitis is a rare manifestation, and has been reported mainly in human immunodeficiency virus-infected patients or patients with other causes of immunocompromise.

Case presentation

The authors report on a case of acute primary Cytomegalovirus infection complicated with acute appendicitis due to Cytomegalovirus in an apparently immunocompetent 24-year-old Caucasian man also suffering from primary sclerosing cholangitis and ulcerative colitis. Diagnosis was based on clinical manifestations, serology results, as well as microbiological and histological findings. Treatment consisted of surgery and anti-Cytomegalovirus therapy.

Conclusions

Cytomegalovirus should be included among the etiologic agents of acute appendicitis in patients with primary sclerosing cholangitis and ulcerative colitis. Currently, there are no definitive data regarding the frequency of Cytomegalovirus appendicitis and the role of anti-Cytomegalovirus treatment in human immunodeficiency virus-negative and apparently immunocompetent subjects.

Rapid identification of bacterial and fungal pathogens from positive blood cultures by MALDI-TOF MS

Sepsis is a syndrome characterized by a systemic inflammatory response due to severe infection. Early detection of causal agents and appropriate antimicrobial treatment reduce mortality. Conventional microbiological methods often do not provide time critical results for an optimal early management. We used an in-house protocol based on Tween 80 to process 109 positive blood cultures for bacteria and yeast identification by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS), and results were compared to standard reference or automated methods. MALDI-TOF MS correctly identified 91.7% of the isolates. Correct identification was obtained for 57/62 (91.9%) aerobic/facultative anaerobic Gram-positive isolates, 53 (85.5%) at species level, and 4 (6.4%) at the genus level; 32/32 (100%) aerobic/facultative anaerobic Gram-negative isolates, 31 (96.9%) at species level, and 1 (3.1%) at the genus level; 7/7 (100%) obligate anaerobes, all at the genus level; 3/7 (42.8%) fungi, all at genus level. Overall, the median identification time of MALDI-TOF MS vs reference standard methods was significantly shorter: median (interquartile range) 7.1h (4.7-10.2) vs 48.1h (32.5-50.0), p<0.0001. MALDI-TOF MS is a valuable tool for rapid identification of pathogens in septic patients. An in-house protocol based on Tween 80 can be used to process positive blood cultures.

The microbial capsular polysaccharide galactoxylomannan inhibits IL-17A production in circulating T cells from rheumatoid arthritis patients

The persistence of activated T cells in rheumatoid arthritis (RA) synovium may be attributable to increased homing, increased retention or a possible imbalance between cell proliferation and programmed cell death. Induction of apoptosis may represent a potential therapeutic approach. Galactoxylomannan (GalXM) from the opportunistic fungus Cryptococcus neoformans can interact with T cells and induce T-cell apoptosis through the inhibition of CD45 phosphatase activity. The aim of this study was to determine the effect of GalXM on circulating T cells from patients with RA and the underlying mechanisms. GalXM immunomodulating effect on apoptosis and signal transduction pathway involved in IL-17A production was evaluated on T cells. RA T-cell apoptosis, higher than that of control T cells, was further increased by GalXM through induction of caspase-3 activation. Activated T cells expressing the CD45RO molecule and producing IL-17A were the main target of GalXM-induced apoptosis. GalXM induced consistent impairment of IL-17A production and inhibition of STAT3, which was hyperactivated in RA. In conclusion, GalXM triggered apoptosis of activated memory T cells and interfered with IL-17A production in RA. These data suggest therapeutic targeting of deleterious Th17 cells in RA and other autoimmune diseases.

Antibody constant region peptides can display immunomodulatory activity through activation of the Dectin-1 signalling pathway

We previously reported that a synthetic peptide with sequence identical to a CDR of a mouse monoclonal antibody specific for difucosyl human blood group A exerted an immunomodulatory activity on murine macrophages. It was therapeutic against systemic candidiasis without possessing direct candidacidal properties. Here we demonstrate that a selected peptide, N10K, putatively deriving from the enzymatic cleavage of the constant region (Fc) of human IgG₁, is able to induce IL-6 secretion and pIkB-α activation. More importantly, it causes an up-regulation of Dectin-1 expression. This leads to an increased activation of β-glucan-induced pSyk, CARD9 and pIkB-α, and an increase in the production of pro-inflammatory cytokines such as IL-6, IL-12, IL-1β and TNF-α. The increased activation of this pathway coincides with an augmented phagocytosis of non opsonized Candida albicans cells by monocytes. The findings suggest that some Fc-peptides, potentially deriving from the proteolysis of immunoglobulins, may cause an unexpected immunoregulation in a way reminiscent of innate immunity molecules.

Antiviral furanosesquiterpenes from Commiphora erythraea

The crude methanolic extract obtained from C. erythraea resin was chromatographed on silica gel with solvent of increasing polarity. The extract and fractions were evaluated for cytotoxicity and antiviral activity [parainfluenza type 3 virus (PIV3)] by plaque forming units (PFU) reduction assay using HEp-2 cells (human larynx epidermoid carcinoma cell line). From the active fraction, five compounds were isolated and tested. Only two of these showed anti-PIV3 activity with a selectivity index (SI) of 66.6 and 17.5, respectively. Both the compounds are furanosesquiterpenoids.

Antiviral Furanosesquiterpenes from Commiphora erythraea

The crude methanolic extract obtained from C. erythraea resin was chromatographed on silica gel with solvent of increasing polarity. The extract and fractions were evaluated for cytotoxicity and antiviral activity [parainfluenza type 3 virus (PIV3)] by plaque forming units (PFU) reduction assay using HEp-2 cells (human larynx epidermoid carcinoma cell line). From the active fraction, five compounds were isolated and tested. Only two of these showed anti-PIV3 activity with a selectivity index (SI) of 66.6 and 17.5, respectively. Both the compounds are furanosesquiterpenoids.

Cryptococcus neoformans galactoxylomannan is a potent negative immunomodulator, inspiring new approaches in anti-inflammatory immunotherapy

Cryptococcus neoformans is an opportunistic fungal pathogen responsible for life-threatening infections in immunocompromised individuals and occasionally in those with no known immune impairment. The fungus is endowed with several virulence factors, including capsular polysaccharides that play a key role in virulence. The capsule is composed of 90–95% glucuronoxylomannan (GXM), 5–8% galactoxylomannan (GalXM) and <1% mannoproteins. Capsular polysaccharides are shed into tissue where they produce many deleterious effects. Since GalXM has a smaller molecular mass, the molar concentration of GalXM in polysaccharide that is shed could exceed that of GXM in C. neoformans exopolysaccharides. Moreover, GalXM exhibits a number of unusual biologic properties both in vitro and in vivo. Here, we summarize the principal immunomodulatory effects of GalXM described during the last 20 years, particularly the mechanisms leading to induction of apoptosis in T lymphocytes, B lymphocytes and macrophages. Since the capacity of GalXM to induce widespread immune suppression is believed to contribute to the virulence of C. neoformans, this property might be exploited therapeutically to dampen the aberrant activation of immune cells during autoimmune disorders.

Breastfeeding and transmission of cytomegalovirus to preterm infants. Case report and kinetic of CMV-DNA in breast milk

Background

Breastfeeding has a major impact on CMV epidemiology. Postnatal CMV reactivation's incidence during lactation is nearby the maternal seroprevalence. Although perinatal CMV infection has practically no consequences in term newborn, it may cause, in some cases, a severe symptomatic disease in preterm newborns.

The aims of the present study are to evaluate the rate and clinical expression of CMV infection breast milk transmitted in preterm infants and to check the safety of the freezing treated breast milk.

Methods

The study included fifty-seven preterm infants and their CMV seropositive mothers. Fresh breast milk samples have been collected from 1^st to 9^th postpartum week. Both fresh breast milk and 72, 96, 120 hours frozen samples have been examined, checking the presence of CMV; urine samples have been tested too.

Results

70.2% of tested mothers showed reactivation of the infection, and CMV-positive breast milk during the six weeks postpartum has been found. However, only one infant was infected by CMV, developing hepatic affection concomitantly with a multi-system involvement, as shown CMV DNA detection in urine, saliva, blood, gastric aspirate, and stools.

Conclusion

Freezing breast milk at -20°C and pasteurization may respectively reduce or eliminate the viral load.

Role of CD45 signaling pathway in galactoxylomannan-induced T cell damage

Previously, we reported that Galactoxylomannan (GalXM) activates the extrinsic and intrinsic apoptotic pathways through an interaction with the glycoreceptors on T cells. In this study we establish the role of the glycoreceptor CD45 in GalXM-induced T cell apoptosis, using CD45(+/+) and CD45(-/-) cell lines, derived from BW5147 murine T cell lymphoma. Our results show that whereas CD45 expression is not required for GalXM association by the cells, it is essential for apoptosis induction. In CD45(+/+) cells, CD45 triggering by GalXM reduces the activation of Lck, ZAP70 and Erk1/2. Conversely, in CD45(-/-) cells, Lck was hyperphosphorylated and did not show any modulation after GalXM stimulation. On the whole, our findings provide evidence that the negative regulation of Lck activation occurs via CD45 engagement. This appears to be related to the capacity of GalXM to antagonize T cell activation and induce T cell death. Overall this mechanism may be responsible for the immune paralysis that follows GalXM administration and could explain the powerful immunosuppression that accompanies cryptococcosis.

Antibody complementarity-determining regions (CDRs): a bridge between adaptive and innate immunity

BACKGROUND

It has been documented that, independently from the specificity of the native antibody (Ab) for a given antigen (Ag), complementarity determining regions (CDR)-related peptides may display differential antimicrobial, antiviral and antitumor activities.

METHODOLOGY/PRINCIPAL FINDINGS

In this study we demonstrate that a synthetic peptide with sequence identical to V(H)CDR3 of a mouse monoclonal Ab (mAb) specific for difucosyl human blood group A is easily taken up by macrophages with subsequent stimulation of: i) proinflammatory cytokine production; ii) PI3K-Akt pathway and iii) TLR-4 expression. Significantly, V(H)CDR3 exerts therapeutic effect against systemic candidiasis without possessing direct candidacidal properties.

CONCLUSIONS/SIGNIFICANCE

These results open a new scenario about the possibility that, beyond the half life of immunoglobulins, Ab fragments may effectively influence the antiinfective cellular immune response in a way reminiscent of regulatory peptides of innate immunity.

Involvement of glycoreceptors in galactoxylomannan-induced T cell death

The major virulence factor of Cryptococcus neoformans is its capsular polysaccharide, which is also released into tissues. The shed polysaccharide is composed of glucuronoxylomannan, galactoxylomannan (GalXM), and mannoproteins. In a previous study, we demonstrated a direct interaction of purified soluble GalXM with T cells that induced their apoptosis. In this study, we focus on the mechanisms involved in the apoptotic effect of GalXM. In our experimental system, we analyzed the effect of GalXM on purified human T cells and Jurkat cells, a T cell line routinely used for apoptotic studies. Our results reveal that GalXM activates the extrinsic and intrinsic apoptotic pathways through the cleavage and recruitment of caspase-8. Caspase-8 elicits the downstream executioner caspase-3, caspase-6, and caspase-7 both directly and indirectly, via Bid cleavage and caspase-9 activation. These effects appeared to be primarily mediated by the interaction of GalXM with the glycoreceptors, which differed in human T and Jurkat cells. CD45 was primarily involved in Jurkat cells apoptosis while CD7 and CD43 mediated human T cell apoptosis. Our results highlight a new mechanism by which a microbial product can contribute to virulence through direct interaction with T cell glycoreceptors, thereby triggering lymphocyte apoptosis.

Bulky 1,4-benzoxazine derivatives with antifungal activity

For many years the development of new azole antifungals has been quite empirically based. More recently, the publication of the crystal structure of CYP51 of Mycobacterium tuberculosis (MT-CYP51) provided new opportunities to rationalize the knowledge about antifungal action of this class of compounds. Recent studies reported that a 'channel 2 opened' conformation of the enzyme could better explain the interaction with ketoconazole (KTZ)-like drugs. Conformational changes were made on our model of Candida albicans CYP51 (CA-CYP51) previously reported and docking experiments were performed. The results allowed new KTZ analogues to be designed, by predicting that the 1,4-benzoxazine moiety could replace the KTZ aryl-piperazinyl chain. The synthesis of derivatives 12 and 13 was planned. The in vitro antifungal activity was evaluated against different Candida species and low and high capsulated strains of Cryptococcus neoformans. Since the in vitro activity do not necessarily correlate with the in vivo antifungal activity the newly synthesized compounds were also tested in a murine model of systemic C. albicans infection. The therapeutic effect was evaluated in terms of animal survival and of fungal growth in the kidneys, the target organ in systemic candidiasis.

Indinavir influences biological function of dendritic cells and stimulates antifungal immunity

In this study, we analyzed the possibility that Indinavir (IDV), a well-known protease inhibitor (PI) used in highly active antiretroviral therapy, could affect immune response against the opportunistic fungus Cryptococcus neoformans. In particular, the quality of dendritic cell (DC) response was analyzed. The results reported here show that IDV treatment induces an expansion of DC with CD8alpha phenotype in spleens of infected hosts. Splenic CD11c+ DC expressed elevated costimulatory molecules such as CD40 and CD80, showed an increased expression of mRNA for proinflammatory cytokines, and secreted abundant IL-12. Integration of all aforementioned regulatory effects results in development of an efficient, T cell-protective response that reflects a consistent reduction in fungus colonization at a cerebral level. These results could help to elucidate the immunoregulatory activity of PI and point out the beneficial effects of IDV in regulating DC functions and antifungal activity. Therefore, although new PI are being introduced in the clinical setting, nevertheless, given its low cost and proven efficacy, IDV could still be considered a potential key compound in the treatment of HIV in resource-limited settings.

Tipranavir exhibits different effects on opportunistic pathogenic fungi

OBJECTIVES

Tipranavir (TPV) is a non-peptidic protease inhibitor (PI) that represents one of the latest options approved in the salvage setting for HIV-infected multi-drug resistant patients. In this study, we explored whether TPV affects virulence of opportunistic fungi such as Cryptococcus neoformans and Candida albicans.

METHODS

C. neoformans and C. albicans were cocultured in the presence or absence of TPV for various time periods. Subsequently, growth inhibition, phospholipases, proteases and capsule size were examined. In selected in vivo experiments, TPV was administered in immunocompetent and immunosuppressed mice. Survival rate and colony forming units from organs were evaluated in mice systemically challenged with C. neoformans or C. albicans.

RESULTS

Indeed, when cultured in the presence of TPV, both fungi showed significant reduction in protease and phospholipase production, but TPV showed an opposite effect on the major virulence factors of C. neoformans and C. albicans by inhibiting capsule while promoting mycelial transition, respectively. TPV impaired in vitro growth of C. neoformans, but not of C. albicans. Moreover, TPV-treated C. neoformans, but not C. albicans, resulted more susceptible to killing by human neutrophils. Finally, TPV showed a therapeutic effect in experimental systemic cryptococcosis, as evaluated by reduced fungal burden in brain and liver of immunocompetent and immunodepressed mice.

CONCLUSIONS

These new data indicate that TPV could act in multiple ways by diversifying its effects on various opportunistic pathogenic fungi.

Immune response toCandida albicansis preserved despite defect inO-mannosylation of secretory proteins

The PMT gene family in Candida albicans encodes five isoforms of the protein mannosyltransferases that initiate O-mannosylation of secretory proteins. Mutations at the Pmt level have been associated with differences in pathogenicity, e.g. in contrast to pmt5/pmt5, pmt2/PMT2 mutants showed poor virulence. Our objective was to determine whether these differences were related to the capacity of pmt2/PMT2 and pmt5/pmt5 to (i) express differences in selected virulence factors, and (ii) stimulate the natural immune system. The results show that pmt mutants (i) form hyphae in serum, (ii) show defective production of proteases but not of phospholipases with respect to the parental strain, (iii) undergo mycelial transition in the kidneys of hematogenously infected animals, (iv) are phagocytosed and killed by macrophages similar to the parental strain, although neutrophils are unable to destroy pmt5/pmt5, (v) engage TLR4 and stimulate MyD88 leading to NF-kappaB activation, and (vi) stimulate cytokine production by macrophages. Collectively our findings suggest that the defect in protein O-mannosylation in C. albicans cause attenuation of the virulence although the antigenic factors that retain the capacity to stimulate an efficient immune response are preserved.

Functional defect of natural immune system in an apparent immunocompetent patient with pulmonary cryptococcosis

We report a case of pulmonary cryptococcosis in a 21-year-old Italian female smoker with no apparent immune disorder. In this study we demonstrated that: (i) patient's neutrophils and monocytes manifested a significant reduction of killing activity against Cryptococcus neoformans as well as Candida albicans; (ii) the suppression was more pronounced in monocytes than in neutrophils; (iii) neutrophils and monocytes showed a significant impairment of TNF-alpha, IL-1beta, and nitric oxide production. These results suggest that the apparent immunocompetent host with pulmonary cryptococcosis could have specific defects in natural immune system mechanisms.

A multidrug-resistant Pseudomonas aeruginosa isolate from a lethal case of sepsis induces necrosis of human neutrophils

A multidrug-resistant Pseudomonas aeruginosa (r-Pa) was isolated from a lethal case of sepsis in a bone marrow transplant recipient. Genotypic analysis of P. aeruginosa isolates demonstrated that sepsis was secondary to gut colonization. The interactions between r-Pa and patient's neutrophils were studied. The results indicate that: (1) the patient's neutrophil killing activity and nitric oxide production against r-Pa or drug sensitive P. aeruginosa (s-Pa) were profoundly impaired; (2) r-Pa cells, but not s-Pa cells or their filtered culture supernatants, induced necrosis of healthy donor neutrophils. Neutrophil necrosis emerges as a remarkable event in the pathogenesis of P. aeruginosa sepsis.

Cryptococcus neoformans capsular polysaccharide component galactoxylomannan induces apoptosis of human T-cells through activation of caspase-8

The major virulence factor of Cryptococcus neoformans is its polysaccharide capsule composed of glucuronoxylomannan (GXM), galactoxylomannan (GalXM) and mannoproteins. A variety of immunomodulating activities have been described for GXM and mannoproteins but little is known about possible interactions of GalXM with the immune system. In the present article, we investigate the effect of purified soluble GalXM on human T lymphocytes. The results indicate that, GalXM (i) can affect selected immune responses; (ii) causes significant impairment of T cell proliferation and increases interferon-gamma and interleukin-10 production; and (iii) induces apoptosis of T lymphocytes through activation of caspase-8 that terminates with fragmentation of DNA. These results are the first to suggest a role for GalXM in C. neoformans virulence by demonstrating that it can target human T cells, and that it may impair the development of an effective specific T cell response.

Indinavir-treated Cryptococcus neoformans promotes an efficient antifungal immune response in immunosuppressed hosts

A previous paper demonstrated that indinavir affects the virulence of Cryptococcus neoformans, thereby rendering the fungus more susceptible to killing by natural effector cells. This study demonstrates that inoculation of immunosuppressed mice with C. neoformans previously exposed to indinavir, in comparison to untreated C. neoformans, results in: (i) a more pronounced secretion of interleukin-12 by splenic dendritic cells; (ii) reduction of CD14 and Fc gammaRs expression on splenic dendritic cells, and upregulation of CD86 and CD40 molecules; (iii) enhancement of interferon-y and interleukin-2 production by splenic T cells and increase of their proliferation in response to fungal antigens; and (iv) survival from an otherwise lethal challenge, correlated with a drastic decrease in colony forming units from brain and liver. In conclusion, these data indicate that indinavir interaction with C. neoformans could be beneficial because of its direct influence on fungal virulence and blunting of the deleterious effects exerted by C. neoformans on host immune response. Thus, indinavir could be crucial in addressing the outcome of cryptococcosis in immunocompromised hosts.

The glucocorticoid-induced tumor necrosis factor receptor-related gene modulates the response to Candida albicans infection

The glucocorticoid-induced tumor necrosis factor (TNF) receptor-related gene (GITR; TNFRSF18) modulates immune response activating coaccessory signals in T cells and is expressed at high levels in CD4+CD25+ cells. Its ligand (GITRL) is expressed in antigen-presenting cells, where it is capable of promoting signaling. We investigated the role of GITR/GITRL interaction during disseminated candidiasis in GITR knockout (GITR-/-) mice. GITR-/- mice survived longer and had a significantly decreased yeast load in kidneys and brain compared to GITR+/+ mice. Since protective immunity to the fungus is mediated by antigen-specific T helper (Th) 1 cells, we studied in vitro cytokine production following infection. CD4+ T cells of GITR-/- mice demonstrated a more efficient Th1 polarization as suggested by a two- to threefold decreased production of interleukin- (IL-)4 and IL-10 and a four- to fivefold increased production of gamma interferon compared to GITR+/+ mice. This effect was not due to differences in lymphocyte and dendritic cell (DC) subpopulations in infected mice as demonstrated by flow cytometric studies. To verify whether DC activity was differently modulated, DCs were cocultured with CD4+ T cells in the presence of heat-inactivated Candida albicans. DCs, cocultured with GITR+/+ CD4+CD25+ cells produced a lower amount of IL-12 than DCs cocultured with GITR-/- CD4+CD25+ T cells. These results suggest that GITR regulates susceptibility to systemic candidiasis by negatively modulating IL-12 production and promoting polarization of CD4+ T cells towards Th2 by analogy with OX40, another TNF receptor superfamily member.

Modulation of phenotype and function of dendritic cells by a therapeutic synthetic killer peptide

The strong microbicidal effects of an engineered synthetic killer peptide (KP), which functionally mimics a fungal killer toxin, have been demonstrated extensively. Beta-glucan has been identified as a receptor for KP on fungal cell walls. Although the direct microbicidal and related therapeutic effects have been studied in depth, no information currently exists about the interaction of KP with immune cells. In this study, we exploited the possibility of KP binding to different murine immune cell populations. The results demonstrate that KP binds selectively to dendritic cells (DC) and to a lesser extent, to macrophages but not to lymphocytes and neutrophils; KP binding possibly occurs through major histocompatibility complex (MHC) class II, CD16/32, and cellular molecules recognized by anti-specific intercellular adhesion molecule-grabbing nonintegrin R1 antibodies; and KP modulates the expression of costimulatory and MHC molecules on DC and improves their capacity to induce lymphocyte proliferation. These findings provide evidence that this synthetic KP interacts selectively with DC and modulating their multiple functions, might also serve to improve the immune antimicrobial response.

Influence of Indinavir on Virulence and Growth ofCryptococcus neoformans

Indinavir selectively inhibited production of some virulence factors of Cryptococcus neoformans, such as urease and protease, but not melanin and phospholipase; moreover, it interfered with capsule formation. These effects led to increased susceptibility of C. neoformans to intracellular killing by natural effector cells. Prolonged incubation with indinavir resulted in inhibition of fungal growth. Indinavir can attenuate the virulence of the fungus, thus augmenting its susceptibility to the antimicrobial activity of natural effector cells. The reduction in cryptococcal infections in human immunodeficiency virus-positive patients might also be related to the antifungal activity of highly active antiretroviral therapy.

A synthetic peptide as a novel anticryptococcal agent

An engineered, killer decapeptide (KP) has been synthesized based on the sequence of a recombinant, single-chain anti-idiotypic antibody (KT-scFv) acting as a functional internal image of a yeast killer toxin. Killer decapeptide exerted a strong fungicidal activity against Candida albicans, which was attributed to peptide interaction with beta-glucan. As this polysaccharide is also a critical component of the cryptococcal cell wall, we wondered whether KP was also active against Cryptococcus neoformans, a human pathogen of increasing medical importance. We found that KP was able to kill both capsular and acapsular C. neoformans cells in vitro. Furthermore, KP impaired the production of specific C. neoformans virulence factors including protease and urease activity and capsule formation, rendering the fungus more susceptible to natural effector cells. In vivo treatment with KP significantly reduced fungal burden in mice with cryptococcosis and, importantly, protected the majority of immunosuppressed animals from an otherwise lethal infection. Given the relevance of cryptococcosis in immunocompromised individuals and the inability of conventional drugs to completely resolve the infection, the results of the present study indicate KP as an ideal candidate for further studies on novel anticryptococcal agents.

Aeromonas veronii biovar veronii septicaemia and acute suppurative cholangitis in a patient with hepatitis B

Gram-negative bacilli of the genus Aeromonas are widespread in aquatic environments and can be responsible for human infections. Although Aeromonas extraintestinal and systemic infections have been reported with growing frequency in recent years, Aeromonas septicaemia remains an uncommon finding, often associated with serious underlying disease and predominantly related to the species Aeromonas hydrophila, Aeromonas veronii biovar sobria and Aeromonas caviae. Here, a case of A. veronii biovar veronii septicaemia and acute suppurative cholangitis is reported in a patient with chronic hepatitis B.

CD80+Gr-1+ myeloid cells inhibit development of antifungal Th1 immunity in mice with candidiasis

To find out whether polymorphonuclear neutrophils (PMN), abundantly recruited in disseminated Candida albicans infection, could directly affect the activation of Th cells we addressed the issues as to whether murine PMN, like their human counterparts, express costimulatory molecules and the functional consequence of this expression in terms of antifungal immune resistance. To this purpose, we assessed 1) the expression of CD80 (B7-1) and CD86 (B7-2) molecules on peripheral, splenic, and inflammatory murine Gr-1+ PMN; 2) its modulation upon interaction with C. albicans in vitro, in vivo, and in human PMN; 3) the effect of Candida exposure on the ability of murine PMN to affect CD4+ Th1 cell proliferation and cytokine production; and 4) the mechanism responsible for this effect. Murine PMN constitutively expressed CD80 molecules on both the surface and intracellularly; however, in both murine and human PMN, CD80 expression was differentially modulated upon interaction with Candida yeasts or hyphae in vitro as well as in infected mice. The expression of the CD86 molecule was neither constitutive nor inducible upon exposure to the fungus. In vitro, Gr-1+ PMN were found to inhibit the activation of IFN-gamma-producing CD4+ T cells and to induce apoptosis through a CD80/CD28-dependent mechanism. A population of CD80+Gr-1+ myeloid cells was found to be expanded in conventional as well as in bone marrow-transplanted mice with disseminated candidiasis, but its depletion increased the IFN-gamma-mediated antifungal resistance. These data indicate that alternatively activated PMN expressing CD80 may adversely affect Th1-dependent resistance in fungal infections.

Protection of killer antiidiotypic antibodies against early invasive aspergillosis in a murine model of allogeneic T-cell-depleted bone marrow transplantation

Antiidiotypic monoclonal antibodies (MAbs) representing the internal image of a yeast killer toxin (KT) have therapeutic potential against several fungal infections. The efficacy of KT MAbs against Aspergillus fumigatus was investigated in a mouse model of T-cell-depleted allogeneic bone marrow transplantation (BMT) with invasive pulmonary aspergillosis. Mice were highly susceptible to infection at 3 days post-BMT, when profound neutropenia was observed both in the periphery and in the lungs. Treatment with KT MAbs protected the mice from infection, as judged by the long-term survival and decreased pathology associated with inhibition of fungal growth and hyphal development in the lungs. In vitro, similar to polymorphonuclear neutrophils, KT MAbs significantly inhibited the hyphal development and metabolic activity of germinated Aspergillus conidia. These results indicate that mimicking the action of neutrophils could be a strategy through which KT MAbs exert therapeutic efficacy in A. fumigatus infections.

Impaired antifungal effector activity but not inflammatory cell recruitment in interleukin-6-deficient mice with invasive pulmonary aspergillosis

A murine model of infection, in which immunocompetent or immunosuppressed interleukin-6-deficient (IL-6(-/-)) mice were infected intranasally with Aspergillus fumigatus conidia and were monitored for parameters of fungal colonization and innate and adaptive immunity, was used to assess the role of IL-6 in invasive pulmonary aspergillosis (IPA). The results indicate that IL-6(-/-) mice were more susceptible than wild-type mice to IPA. Susceptibility was associated with increased inflammatory pathology, decreased antifungal effector functions of phagocytes, and impaired development of protective type 1 responses. Exposure to exogenous IL-6 restored antifungal effector activity.

Defective antifungal T-helper 1 (TH1) immunity in a murine model of allogeneic T-cell-depleted bone marrow transplantation and its restoration by treatment with TH2 cytokine antagonists

Patients undergoing full haplotype-mismatched hematopoietic transplantations may experience severe intractable invasive fungal infections. To verify whether an imbalanced production of T-helper 1 (TH1) and TH2 cytokines may be responsible for susceptibility to fungal infections, C3H/HeJ (H-2(k)) recipient mice were lethally irradiated, received transplantations with T-cell-depleted allogeneic bone marrow (BM) cells from mice of H-2(d) haplotype, and were infected with Candida albicans. At different time-points after transplantation, mice were assessed for pattern of TH cytokine production and susceptibility to infection. The results show that a long-term, donor-type chimerism was achieved as early as 2 weeks after BM transplantation (BMT), at the time when high-level production of TH2 cytokines (interleukin-4 [IL-4] and IL-10) and impaired production of TH1 cytokines (interferon-gamma [IFN-gamma] and IL-12] were observed. At this time, mice were highly susceptible to both disseminated and mucosal infections, as indicated by decreased survival, uncontrolled fungal growth, and failure to develop protective TH1 immunity. However, a predominant production of TH1 cytokines was observed by week 5 after BMT, at the time when mice developed donor-type protective TH1 responses and were resistant to infections. Therapeutic ablation of IL-4 or IL-10 greatly increased resistance to candidiasis. These results indicate that a dysregulated production of TH cytokines occurs in mice undergoing T-cell-depleted allogeneic BMT. The transient predominant production of TH2 cytokines over that of IL-12 impaired the ability of mice to develop antifungal TH1 resistance, an activity that could be efficiently restored upon treatment with TH2 cytokine antagonists.

Cytokines in candidiasis and aspergillosis

Both innate and T helper (Th) immunity play a central role in fungal infections. A bi-directional influence exists between the two compartments of the immune system, mainly occurring through cytokine production. On the one hand, protective Th1 or nonprotective Th2 cells mediate resistance or susceptibility to disseminated and localized fungal infections by secreting cytokines with activating or deactivating signals for effector phagocytic cells. On the other hand, cells of the innate immune system regulate the development of antifungal T helper responses by producing directive cytokines, such as interleukin (IL)-12 and IL-10. In experimental models of Candida albicans and Aspergillus fumigatus infections, the administration or neutralization of selective cytokines and the use of cytokine-deficient mice have revealed the existence of a hierarchical pattern of cytokine mediated regulation of antifungal Th cell development and effector function. A finely regulated balance of directive cytokines, rather than the relative absence of opposing cytokines, appears to be required for optimal development and maintenance of protective Th1 reactivity to fungi. Thus, it is conceivable that some cytokines may have beneficial or deleterious effects on infection, depending on the dose and timing of endogenous production or exogenous administration. A better understanding of the different, sometimes unexpected, roles of cytokines is required for their use in prophylaxis and therapy of fungal infections, either alone or in combination with antifungal agents.

Interleukin 18 restores defective Th1 immunity to Candida albicans in caspase 1-deficient mice

Caspase 1, formerly designated interleukin 1beta (IL-1beta)-converting enzyme, processes pro-IL-1beta and pro-IL-18 to yield active cytokines that play a pivotal role in inflammation and cell activation. We show here the effect of caspase 1 deficiency on the inflammatory and adaptive immune responses to the fungus Candida albicans. Caspase 1 deficiency did not affect susceptibility to primary systemic infection with the fungus, as revealed by survival and fungal growth. However, Th1-mediated resistance to reinfection was greatly impaired in caspase 1-deficient mice, and this correlated with low-level production of IL-12 and gamma interferon. Early in infection, production of these cytokines and that of tumor necrosis factor alpha, IL-6, and, interestingly, IL-1beta occurred normally in caspase 1-deficient mice, while that of IL-18 was severely impaired. Exogenous administration of IL-18, more than IL-12, restored the Th1-mediated resistance to the infection. We conclude that, while caspase 1 is not indispensable for release of mature IL-1beta in candidiasis, the caspase 1-dependent production of IL-18 may represent an important and novel pathway for the expression of sustained Th1 reactivity to the fungus.