Exploring nasopharyngeal microbiota profile in children affected by SARS-CoV-2 infection

The relationship between COVID-19 and nasopharyngeal (NP) microbiota has been investigated mainly in the adult population. We explored the NP profile of children affected by COVID-19, compared to healthy controls (CTRLs). NP swabs of children with COVID-19, collected between March and September 2020, were investigated at the admission (T0), 72 h to 7 days (T1), and at the discharge (T2) of the patients. NP microbiota was analyzed by 16S rRNA targeted-metagenomics. Data from sequencing were investigated by QIIME 2.0 and PICRUSt 2. Multiple machine learning (ML) models were exploited to classify patients compared to CTRLs. The NP microbiota of COVID-19 patients (N = 71) was characterized by reduction of α-diversity compared to CTRLs (N = 59). The NP microbiota of COVID-19 cohort appeared significantly enriched in Streptococcus, Haemophilus, Staphylococcus, Veillonella, Enterococcus, Neisseria, Moraxella, Enterobacteriaceae, Gemella, Bacillus, and reduced in Faecalibacterium, Akkermansia, Blautia, Bifidobacterium, Ruminococcus, and Bacteroides, compared to CTRLs (FDR < 0.001). Exploiting ML models, Enterococcus, Pseudomonas, Streptococcus, Capnocytopagha, Tepidiphilus, Porphyromonas, Staphylococcus, and Veillonella resulted as NP microbiota biomarkers, in COVID-19 patients. No statistically significant differences were found comparing the NP microbiota profile of COVID-19 patients during the time-points or grouping patients on the basis of high, medium, and low viral load (VL). This evidence provides specific pathobiont signatures of the NP microbiota in pediatric COVID-19 patients, and the reduction of anaerobic protective commensals. Our data suggest that the NP microbiota may have a specific disease-related signature since infection onset without changes during disease progression, regardless of the SARS-CoV-2 VL.

IMPORTANCE

Since the beginning of pandemic, we know that children are less susceptible to severe COVID-19 disease. A potential role of the nasopharyngeal (NP) microbiota has been hypothesized but to date, most of the studies have been focused on adults. We studied the NP microbiota modifications in children affected by SARS-CoV-2 infection showing a specific NP microbiome profile, mainly composed by pathobionts and almost missing protective anaerobic commensals. Moreover, in our study, specific microbial signatures appear since the first days of infection independently from SARS-CoV-2 viral load.

Imposter syndrome and its associated factors in medical students in six Peruvian faculties

OBJECTIVE

To determine the factors associated with impostor syndrome in medical students from six regions of Peru.

MATERIAL AND METHODS

A multicentre, cross-sectional study was conduced on students from first to the sixth year in six Peruvian regions. Sociodemographic, academic, and psychological characteristics were included through the Depression, Anxiety, and Stress Scale-21, the Rosenberg Self-Esteem Scale and the Clance Imposter Phenomenon Scale. Generalised linear models were performed using crude and adjusted estimated prevalence ratios.

RESULTS

Of 2,231 medical students, 54.3% were female and 30.6% had the impostor phenomenon. An association was found between the PI and those who suffered from depression (aPR=1.51; 95%CI, 1.27-1.79), anxiety (aPR=2.25; 95%CI, 1.75-2.90), stress (aPR=1.37; 95%CI, 1.19-1.57), and being female (aPR=1.12; 95%CI, 1.01-1.26).

CONCLUSIONS

Three out of 10 medical students suffer from PI; having some level of depression, anxiety, stress, being a woman, and/or attending the fourth academic year were predisposing factors for their development.

Factors associated with mortality in patients hospitalized for COVID-19 admitted to a tertiary hospital in Lambayeque, Peru, during the first wave of the pandemic

INTRODUCTION

COVID-19 caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has spread worldwide, becoming a long-term pandemic.

OBJECTIVES

To analyze the factors associated with mortality in patients hospitalized for COVID-19 in a tertiary hospital in the Lambayeque region of Peru.

METHODS

A retrospective cohort study of patients with a diagnosis of COVID-19, hospitalized in a hospital in northern Peru, was conducted from March to September 2020.

RESULTS

Of the 297 patients studied, 69% were women, the mean age was 63.99 years (SD = ±15.33 years). Hypertension was the most frequent comorbidity (36.67%), followed by diabetes mellitus (24.67%) and obesity (8.33%). The probability of survival at 3 days of ICU stay was 65.3%, at 7 days 24.2%, and 0% on day 14. Risk factors associated with mortality in patients hospitalized for COVID-19 are age, male sex, tachypnea, low systolic blood pressure, low peripheral oxygen saturation, impaired renal function, elevated IL-6 and elevated D-dimer.

CONCLUSIONS

Mortality in hospitalized patients with COVID-19 was 51.18 per 100 persons, Mortality was found to be associated with hypertension, type of infiltrating, and sepsis.

Réplica: Revisión metodológica sobre el artículo “Factores asociados a la no utilización de servicios de salud en personas LGBTI de Perú”

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Factors associated with the non-use of health services in LGBTI people from Peru

OBJECTIVE

To determine the factors associated with the non-use of health services in a sample of the lesbian, gay, bisexual, transgender, and intersex population of Peru.

MATERIALS AND METHODS

Analytical cross-sectional study, analysis of secondary data from the First LGBTI Survey of Peru. Those who suffered from a medical condition during the last twelve months and had to receive medical attention were considered a variable of interest. Crude prevalence ratios (PRc) and adjusted (PRa), with 95% confidence intervals (95% CI) were calculated using Poisson regressions with robust variance. Three models were developed, adjusted to variables grouped according to sexual orientation, gender identity, and intersexuality.

RESULTS

55.4% were male at birth, the median age was 25 years (IR: 21-30). 16% stated that they had not sought medical attention. The three models presented a negative association in having suffered a chronic disease, infectious, contagious diseases, and mental illness and those who expressed their orientation openly. Not being respected for the gender they identified with was related to not using the services in model 3. Models 1 and 3 included a positive association with not being respected with the gender identified.

CONCLUSION

Suffering from a mental illness, an infectious contagious disease, a chronic disease, and not being treated with respect according to their gender identity are factors associated with the non-use of health services.

Imposter Syndrome and its Associated Factors in Medical Students in Six Peruvian Faculties

OBJECTIVE

To determine the factors associated with impostor syndrome in medical students from six regions of Peru.

MATERIAL AND METHODS

A multicentre, cross-sectional study was conduced on students from first to the sixth year in six Peruvian regions. Sociodemographic, academic, and psychological characteristics were included through the Depression, Anxiety, and Stress Scale-21, the Rosenberg Self-Esteem Scale and the Clance Imposter Phenomenon Scale. Generalised linear models were performed using crude and adjusted estimated prevalence ratios.

RESULTS

Of 2,231 medical students, 54.3% were female and 30.6% had the impostor phenomenon. An association was found between the PI and those who suffered from depression (aPR=1.51; 95%CI, 1.27-1.79), anxiety (aPR=2.25; 95%CI, 1.75-2.90), stress (aPR=1.37; 95%CI, 1.19-1.57), and being female (aPR=1.12; 95%CI, 1.01-1.26).

CONCLUSIONS

Three out of 10 medical students suffer from PI; having some level of depression, anxiety, stress, being a woman, and/or attending the fourth academic year were predisposing factors for their development.

The 2020 International Alliance for the Control of Scabies Consensus Criteria for the Diagnosis of Scabies

BACKGROUND

Scabies is a common parasitic skin condition that causes considerable morbidity globally. Clinical and epidemiological research for scabies has been limited by a lack of standardization of diagnostic methods.

OBJECTIVES

To develop consensus criteria for the diagnosis of common scabies that could be implemented in a variety of settings.

METHODS

Consensus diagnostic criteria were developed through a Delphi study with international experts. Detailed recommendations were collected from the expert panel to define the criteria features and guide their implementation. These comments were then combined with a comprehensive review of the available literature and the opinion of an expanded group of international experts to develop detailed, evidence-based definitions and diagnostic methods.

RESULTS

The 2020 International Alliance for the Control of Scabies (IACS) Consensus Criteria for the Diagnosis of Scabies include three levels of diagnostic certainty and eight subcategories. Confirmed scabies (level A) requires direct visualization of the mite or its products. Clinical scabies (level B) and suspected scabies (level C) rely on clinical assessment of signs and symptoms. Evidence-based, consensus methods for microscopy, visualization and clinical symptoms and signs were developed, along with a media library.

CONCLUSIONS

The 2020 IACS Criteria represent a pragmatic yet robust set of diagnostic features and methods. The criteria may be implemented in a range of research, public health and clinical settings by selecting the appropriate diagnostic levels and subcategories. These criteria may provide greater consistency and standardization for scabies diagnosis. Validation studies, development of training materials and development of survey methods are now required. What is already known about this topic? The diagnosis of scabies is limited by the lack of accurate, objective tests. Microscopy of skin scrapings can confirm the diagnosis, but it is insensitive, invasive and often impractical. Diagnosis usually relies on clinical assessment, although visualization using dermoscopy is becoming increasingly common. These diagnostic methods have not been standardized, hampering the interpretation of findings from clinical research and epidemiological surveys, and the development of scabies control strategies. What does this study add? International consensus diagnostic criteria for common scabies were developed through a Delphi study with global experts. The 2020 International Alliance for the Control of Scabies (IACS) Criteria categorize diagnosis at three levels of diagnostic certainty (confirmed, clinical and suspected scabies) and eight subcategories, and can be adapted to a range of research and public health settings. Detailed definitions and figures are included to aid training and implementation. The 2020 IACS Criteria may facilitate the standardization of scabies diagnosis.

A systems genomics approach identifies SIGLEC15 as a susceptibility factor in recurrent vulvovaginal candidiasis

Candida vaginitis is a frequent clinical diagnosis with up to 8% of women experiencing recurrent vulvovaginal candidiasis (RVVC) globally. RVVC is characterized by at least three episodes per year. Most patients with RVVC lack known risk factors, suggesting a role for genetic risk factors in this condition. Through integration of genomic approaches and immunological studies in two independent cohorts of patients with RVVC and healthy individuals, we identified genes and cellular processes that contribute to the pathogenesis of RVVC, including cellular morphogenesis and metabolism, and cellular adhesion. We further identified SIGLEC15, a lectin expressed by various immune cells that binds sialic acid-containing structures, as a candidate gene involved in RVVC susceptibility. Candida stimulation induced SIGLEC15 expression in human peripheral blood mononuclear cells (PBMCs) and a polymorphism in the SIGLEC15 gene that was associated with RVVC in the patient cohorts led to an altered cytokine profile after PBMC stimulation. The same polymorphism led to an increase in IL1B and NLRP3 expression after Candida stimulation in HeLa cells in vitro. Last, Siglec15 expression was induced by Candida at the vaginal surface of mice, where in vivo silencing of Siglec15 led to an increase in the fungal burden. Siglec15 silencing was additionally accompanied by an increase in polymorphonuclear leukocytes during the course of infection. Identification of these pathways and cellular processes contributes to a better understanding of RVVC and may open new therapeutic avenues.

FRI0182 RISK FACTORS ASSOCIATED WITH RENAL INVOLVEMENT IN PRIMARY SJÖGREN’S SYNDROME: DATA FROM THE SPANISH SJÖGRENSER COHORT

Objectives:

To investigate the prevalence, risk factors, and effects of primary renal disease on morbidity and mortality in patients with primary Sjögren’s syndrome (pSS).

Methods:

All patients in the SJÖGRENSER (registry of adult SSp patients of the Spanish Society of Rheumatology, cross-sectional phase) cohort were retrospectively investigated for the presence of clinically significant renal involvement directly related to pSS activity.

Results:

Of the 437 patients investigated, 39 (9%) presented overt renal involvement during follow-up. Severe renal disease necessitating kidney biopsy was relatively rare (23%).

Renal involvement may complicate pSS at any time during the disease course and is associated with severe disease (indicated by higher scores of involvement, activity, and damage), systemic multiorgan involvement, and a higher frequency of lymphoma. Multivariate analysis showed that older age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.00–1.07), higher European League Against Rheumatism Sjogren’s Syndrome Disease Activity Index scores (OR 1.1, CI 1.03–1.18), serum anti-La/SSB positivity (OR 6.44, CI 1.36–30.37), and non-vasculitic cutaneous involvement (OR 8.64, 1.33–55.90) were independently associated with this complication.

Chronic renal failure developed in 23 of 39 patients (59%); only 1 of them progressed to end-stage renal disease necessitating renal replacement therapy. Patients with renal disease showed higher Sjögren’s syndrome disease damage index scores (SSDDI), higher rates of hospitalization due to disease activity and higher rates of clinically relevant comorbidities.

Conclusion:

Renal involvement is an uncommon complication in pSS that was observed in 9% of patients. Although categorized as a non-negligible comorbidity, this condition shows a favorable prognosis.

Disclosure of Interests:

None declared

A biological model of scabies infection dynamics and treatment informs mass drug administration strategies to increase the likelihood of elimination

Infections with Sarcoptes scabiei, or scabies, remain common in many disadvantaged populations. Mass drug administration (MDA) has been used in such settings to achieve a rapid reduction in infection and transmission, with the goal of eliminating the public health burden of scabies. While prevalence has been observed to fall substantially following such an intervention, in some instances resurgence of infection to baseline levels has occurred over several years. To explore the biology underpinning this phenomenon, we have developed a theoretical model of scabies life-cycle and transmission dynamics in a homogeneously mixing population, and simulate the impact of mass drug treatment strategies acting on egg and mite life cycle stages (ovicidal) or mites alone (non-ovicidal). In order to investigate the dynamics of the system, we first define and calculate the optimal interval between treatment doses. We calculate the probability of eradication as a function of the number of optimally-timed successive treatment doses and the number of years over which a program is run. For the non-ovicidal intervention, we first show that at least two optimally-timed doses are required to achieve eradication. We then demonstrate that while more doses over a small number of years provides the highest chance of eradication, a similar outcome can be achieved with fewer doses delivered annually over a longer period of time. For the ovicidal intervention, we find that doses should be delivered as close together as possible. This work provides a platform for further research into optimal treatment strategies which may incorporate heterogeneity of transmission, and the interplay between MDA and enhancement of continuing scabies surveillance and treatment strategies.

Association of a variable number tandem repeat in the NLRP3 gene in women with susceptibility to RVVC

Vaginal infections with Candida spp. frequently occur in women of childbearing age. A small proportion of these women experience recurrent vulvovaginal candidosis (RVVC), which is characterized by at least three episodes of infection in one year. In addition to known risk factors such as antibiotics, diabetes, or pregnancy, host genetic variation and inflammatory pathways such as the IL-1/Th17 axis have been reported to play a substantial role in the pathogenesis of RVVC. In this study, we assessed a variable number tandem repeat (VNTR) polymorphism in the NLRP3 gene that encodes a component of the inflammasome, processing the proinflammatory cytokines IL-1β and IL-18. A total of 270 RVVC patients and 583 healthy controls were analyzed, and increased diseases susceptibility was associated with the presence of the 12/9 genotype. Furthermore, functional studies demonstrate that IL-1β production at the vaginal surface is higher in RVVC patients bearing the 12/9 genotype compared to controls, whereas IL-1Ra levels were decreased and IL-18 levels remained unchanged. These findings suggest that IL-1β-mediated hyperinflammation conveyed by the NLRP3 gene plays a causal role in the pathogenesis of RVVC and may identify this pathway as a potential therapeutic target in the disease.

Electroporation Enhances Bleomycin Efficacy in Cats with Periocular Carcinoma and Advanced Squamous Cell Carcinoma of the Head

Background

Advanced carcinoma of the head represents a substantial health problem in cats for local control and overall survival.

Objectives

Evaluate the capability of electrochemotherapy (ECT) to improve bleomycin efficacy in cats with periocular carcinoma and advanced carcinoma of the head.

Animals

Twenty‐one cats with periocular carcinoma (17 squamous cell carcinoma [SCC] and 4 anaplastic carcinoma) and 26 cats with advanced SCC of the head.

Methods

Nonrandomized prospective controlled study. Periocular carcinoma cohorts: 12 cats were treated with bleomycin (15 mg/m²IV) coupled with ECT under anesthesia; 9 cats were treated with bleomycin alone. Advanced head SCC cohorts: 14 cats were treated with bleomycin (15 mg/m²IV) coupled with ECT administered under sedation; 12 control cats were treated with bleomycin alone. ECT treatments (2–8) were performed every other week until complete remission (CR) or tumor progression occurred.

Results

Toxicities were minimal and mostly treated symptomatically. Overall response rate in the ECT treated animals was 89% (21 Complete Response [CR] and 2 Partial Response [PR]) whereas controls had response rate of 33% (4 CR and 3 PR). Median time to progression in ECT group was 30.5 months, whereas in controls it was 3.9 months (P < .0001). Median time to progression for ECT cohorts was 24.2 months for periocular cohort and 20.6 in advanced head SCC cohort, respectively.

Conclusions

Electrochemotherapy is well tolerated for advanced SCC of the head in cats; its use may be considered among loco‐regional strategies for cancer therapy in sensitive body regions such as periocular region.

Fine-tuning of Th17 Cytokines in Periodontal Disease by IL-10

Periodontitis (PD) is a chronic disease caused by the host inflammatory response to bacteria colonizing the oral cavity. In addition to tolerance to oral microbiome, a fine-tuned balance of IL-10 levels is critical to efficiently mount antimicrobial resistance without causing immunopathology. Clinical and animal studies support that adaptive T-helper (Th) cytokines are involved in the pathogenesis of alveolar bone destruction in PD. However, it remains unclear what type of Th response is related to human PD progression and what role IL-10 has on this process. We addressed the contribution of IL-10 in limiting Th1 and Th17 inflammatory response in murine and human PD. Through a combination of basic and translational approaches involving selected cytokine-deficient mice as well as human genetic epidemiology, our results demonstrate the requirement for IL-10 in fine-tuning the levels of Th17 (IL-17A and IL-17F) cytokines in experimental and human PD. Of novelty, we found that IL-17F correlated with protection in murine and human PD and was positively regulated by IL-10. To our knowledge, this is the first demonstration of the protective role for IL-17F in PD, its positive regulation by IL-10, and the potential differential role for IL-17A and IL-17F in periodontal disease.

Immune resistance and tolerance to fungi

Fungal diseases represent an important paradigm in immunology, since they can result from either the lack of recognition or over-activation of the inflammatory response. Current understanding of the pathophysiology underlying fungal infections and diseases highlights the multiple cell populations and cell-signaling pathways involved in these complex conditions beyond the dysregulated chaos in which fungal infection and disease are perceived. A systems biology approach that integrates investigations of immunity at the systems-level is required to generate novel insights into this complexity and to decipher the dynamics of the host-fungus interaction. Recent advances in the immune response to fungi have highlighted the cellular and molecular mechanisms of immune adaptations that maintain homeostasis with the fungal biota and its possible rupture in fungal infections and diseases. Functionally distinct modules of immunity, i.e., resistance and tolerance, evolved for the achievement of the best-fitted host-fungus interaction in mammals, are now essential components of the host-fungus interaction in the vertebrate host.

Five years of experience in nocturnal enuresis and urinary incontinence in children: where we are and where we are going

BACKGROUND

Nocturnal enuresis (NE) is a very common pediatric disorder. The aim of this study was to evaluate the characteristics of patients with NE or urinary incontinence (UI) during a period of 5 years to increase the knowledge on these conditions and optimize their diagnosis and treatment.

METHODS

We enrolled 278 children with NE or UI referred to the pediatric nephrology ambulatory, 'A. Gemelli' University Hospital of Rome, from December 2006 to December 2011.

RESULTS

We observed that heredity, parasomnias, left-handedness, polythelia and constipation are correlated to NE and UI.

CONCLUSIONS

We wanted to clarify the definition of NE and UI and describe our experience on the main characteristics of these conditions by referring to the latest knowledge reported in the literature.

Immunotherapy of aspergillosis

Management of invasive aspergillosis in high-risk patients remains challenging. There is an increasing demand for novel therapeutic strategies aimed at enhancing or restoring antifungal immunity in immunocompromised patients. In this regard, modulation of specific innate immune functions and vaccination are promising immunotherapeutic strategies. Recent findings have also provided a compelling rationale for assessment of the contribution of the individual genetic profile to the immunotherapy outcome. Altogether, integration of immunological and genetic data may contribute to the optimization of therapeutic strategies exerting control over immune pathways, ultimately improving the management of fungal infections in high-risk settings.

IL-22 defines a novel immune pathway of antifungal resistance

The role of IL-17 and Th17 cells in immunity vs. pathology associated with the human commensal Candida albicans remains controversial. Both positive and negative effects on immune resistance have been attributed to IL-17/Th17 in experimental candidiasis. In this study, we provide evidence that IL-22, which is also produced by Th17 cells, has a critical, first-line defense in candidiasis by controlling the growth of infecting yeasts as well as by contributing to the host's epithelial integrity in the absence of acquired Th1-type immunity. The two pathways are reciprocally regulated, and IL-22 is upregulated under Th1 deficiency conditions and vice versa. Whereas both IL-17A and F are dispensable for antifungal resistance, IL-22 mediates protection in IL-17RA-deficient mice, in which IL-17A contributes to disease susceptibility. Thus, our findings suggest that protective immunity to candidiasis is made up of a staged response involving an early, IL-22-dominated response followed by Th1/Treg reactivity that will prevent fungal dissemination and supply memory.

Dynamics of extracellular release of Aspergillus fumigatus DNAand galactomannan during growth in blood and serum

Aspergillus fumigatus is the major cause of invasive aspergillosis (IA),a disease associated with high rates of morbidity and mortality in patientsundergoing treatment for haematological malignancies. This study investigated A. fumigatus growth in vitro and in a murine model of IA inorder to provide insights into the dynamics of extracellular DNA and galactomannan (GM)release and their relevance to early diagnosis of IA. Following inoculationof whole blood with 20 A. fumigatus conidia ml−1,DNA that corresponded to the inoculum could be detected by PCR but GM wasnot detected in plasma separated from the blood sample, indicating that thefungus did not grow in whole blood. The quantities of DNA detected by PCR,and GM, were proportional to the amount of fungal biomass present in vitro. Fungal DNA could be detected in the sera of mice experimentally infectedwith A. fumigatus with maximum detection in cyclophosphamide-treatedmice.

Chronic granulomatous disease

Chronic granulomatous disease is an inherited disorder of the NADPH oxidase characterized by severe bacterial and fungal infections and disordered inflammation. We propose that NADPH oxidase has a key role in regulating acute neutrophilic and T cell responses, which in turn restrains fungal growth and calibrates the inflammatory response to minimize injury and allergy. In this model, superoxide-induced activation of indoleamine 2,3-dioxygenase (IDO) is a central mechanism by which the optimal balance of antifungal host defense and immune tolerance occurs. This model is based on studies in mice and requires correlation in humans.

Polymorphisms in toll-like receptor genes and susceptibility to pulmonary aspergillosis

Toll-like receptors (TLRs) are important components of innate immunity. We investigated the association between polymorphisms in the TLR2, TLR4, and TLR9 genes and susceptibility to noninvasive forms of pulmonary aspergillosis. A significant association was observed between allele G on Asp299Gly (TLR4) and chronic cavitary pulmonary aspergillosis (odds ratio [OR], 3.46; P =.003). Susceptibility to allergic bronchopulmonary aspergillosis was associated with allele C on T-1237C (TLR9) (OR, 2.49; P =. 043). No particular polymorphism was associated with severe asthma with fungal sensitization. These findings reinforce the importance of innate immunity in the pathogenesis of different forms of aspergillosis.

The contribution of PARs to inflammation and immunity to fungi

During inflammation, host- and microbial-derived proteases trigger the activation of protease-activated receptors (PARs), a family of G-protein-coupled receptors. We report here that activation of Toll-like receptors (TLRs) by fungi unmasks an essential and divergent role for PAR(1) and PAR(2) in downstream signaling and inflammation. TLRs activated PARs and triggered distinct signal transduction pathways involved in inflammation and immunity to Candida albicans and Aspergillus fumigatus. Inflammation was promoted by PAR(1) and PAR(2) activation in response to Candida and by PAR(2) inhibition in response to Aspergillus. This occurred by TLR regulation of PAR signaling, with TLR2 promoting PAR(1) activity, and TLR4 suppressing PAR(2) activity. Thus, tissue injury and pathogens induce signals that are integrated at the level of distinct TLR/PAR-dependent pathways, the exploitation or subversion of which contributes to divergence in microbial promotion of inflammatory response.

Induction and protection of autoimmune rheumatic diseases. The role of infections

It is thought that in genetically predisposed individuals, autoimmune diseases can be promoted and/or exacerbated by viruses, bacteria, or parasitic infectious agents. Pathogens can activate innate immune response interacting with Toll-like receptors that recognize pathogen-associated molecules. As a consequence of infections, a prolonged inflammatory response may occur leading to chronic inflammation with activation of adaptive immune response. In addition, the defective clearance of apoptotic infected cells, which progress- es to secondary necrosis, can foster the autoimmune reactions. Although numerous data from humans and/or animal models support the hypothesis of a direct contribution of pathogens to the induction of the disease, some infectious agents are able to prevent autoimmune disorders. In this review, data on the innate and adaptive immune response induced by pathogens are summarized, focusing on the possible protective or non-protective role of infections in the development of autoimmune diseases.

Immune regulation and tolerance to fungi in the lungs and skin

The balance of pro- and anti-inflammatory signaling is a prerequisite for successful host/fungal interactions and requires the coordinate actions of both innate and adaptive immune systems. Although inflammation is an essential component of the protective response to fungi, its dysregulation may significantly worsen fungal diseases and limit protective antifungal immune responses. The newly described Th17 develop - mental pathway may play an inflammatory role previously attributed to uncontrolled Th1 responses and serve to accommodate the seemingly paradoxical association of chronic inflammatory responses with fungal persistence in the face of an ongoing inflammation. In this scenario, unrestricted fungal growth could result from the activation of not only pathogenic Th17 cells, but also Th2 cells whose activation is strictly dependent on fungal burden. The capacity of regulatory T cells (Tregs) to inhibit aspects of innate and adaptive antifungal immunity is required for protective tolerance to fungi. Indoleamine 2,3-dioxygenase (IDO) and tryptophan catabolites contribute to such a homeostatic condition by providing the host with immune defense mechanisms adequate for protection, without necessarily eliminating fungal pathogens - which would impair immune memory - or causing an unacceptable level of tissue damage. IDO and tryptophan metabolites may prove to be potent regulators capable of taming overzealous or heightened inflammatory host responses.

Immunity to Aspergillus fumigatus: the basis for immunotherapy and vaccination

Efficient responses to fungi require different mechanisms of immunity. Dendritic cells (DCs) are uniquely able to decode the fungus-associated information and translate it into qualitatively different T helper (Th) immune responses. Murine and human DCs phagocytose conidia and hyphae of Aspergillus fumigatus through distinct recognition receptors. The engagement of distinct receptors translates into disparate downstream signaling events, ultimately affecting cytokine production and co-stimulation. Adoptive transfer of different types of DCs activates protective and non-protective Th cells as well as regulatory T cells, ultimately affecting the outcome of the infection in mice with invasive aspergillosis. The infusion of fungus-pulsed or RNA-transfected DCs also accelerates recovery of functional antifungal Th 1 responses in mice with allogeneic hematopoietic stem cell transplantation. Patients receiving T cell-depleted allogeneic hematopoietic stem cell transplantation are unable to develop antigen-specific T cell responses soon after transplant due to defective DC functions. Our results suggest that the adoptive transfer of DCs may restore immunocompetence in hematopoietic stem cell transplantation by contributing to the educational program of T cells. Thus, the remarkable furictional plasticity of DCs can be exploited for the deliberate targeting of cells and pathways of cell-mediated immunity in response to the fungus.

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.

Host immune reactivity and antifungal chemotherapy: the power of being together

Fungal infections, particularly those in immunocompromised hosts, have been a major therapeutic challenge over recent decades. The difficulty in diagnosing invasive infections, together with the emergence of unusual opportunistic pathogens and a pathogen shift in the spectrum of the causative organisms, have greatly hampered the effectiveness of antifungal therapy. Knowledge of the immunoregulation of fungal infections may provide new insights for therapeutic interventions. The appreciation of the importance of T helper cells and cytokines in the overall coordination of the effector immune response to fungi has offered novel opportunities to manipulate these processes and to alter the outcome of fungal infections while improving the therapeutic efficacy of antifungal drugs. Cytokine and cytokine antagonists, alone or in combination with antifungals, have the potential to overcome the specific defects of host immune reactivity predisposing to fungal infections. The current challenge lies in translating much of the information obtained in experimental and preclinical studies into therapeutic strategies providing prospects for the ultimate treatment of fungal infections.

Knockout mice as experimental models of virulence

Infection models with animals whose immune systems have been selectively altered by neutralization of endogenous cytokines or by deletion of a gene have provided a valuable means to study the function of cells or cytokines in the context of complex multidimensional interactions. In particular, knockout mice have allowed a deeper insight into the in vivo performance of antifungal innate and acquired immunity, whose interplay is considered fundamental in the general defense against infections. It is conceivable that such an integrated view of effector and regulatory immune mechanisms operating in opportunistic fungal infections would facilitate the search for cells, cytokines and molecular pathways that are essential to control fungal infectivity or oppose fungus-associated immunopathology.

Postgrafting administration of granulocyte colony-stimulating factor impairs functional immune recovery in recipients of human leukocyte antigen haplotype-mismatched hematopoietic transplants

In human leukocyte antigen haplotype-mismatched transplantation, extensive T-cell depletion prevents graft-versus-host disease (GVHD) but delays immune recovery. Granulocyte colony-stimulating factor (G-CSF) is given to donors to mobilize stem cells and to recipients to ensure engraftment. Studies have shown that G-CSF promotes T-helper (Th)-2 immune deviation which, unlike Th1 responses, does not protect against intracellular pathogens and fungi. The effect of administration of G-CSF to recipients of mismatched hematopoietic transplants with respect to transplantation outcome and functional immune recovery was investigated. In 43 patients with acute leukemia who received G-CSF after transplantation, the engraftment rate was 95%. However, the patients had a long-lasting type 2 immune reactivity, ie, Th2-inducing dendritic cells not producing interleukin 12 (IL-12) and high frequencies of IL-4- and IL-10-producing CD4(+) cells not expressing the IL-12 receptor beta(2) chain. Similar immune reactivity patterns were observed on exposure of donor cells to G-CSF. Elimination of postgrafting administration of G-CSF in a subsequent series of 36 patients with acute leukemia, while not adversely affecting engraftment rate (93%), resulted in the anticipated appearance of IL-12-producing dendritic cells (1-3 months after transplantation versus > 12 months in transplant recipients given G-CSF), of CD4(+) cells of a mixed Th0/Th1 phenotype, and of antifungal T-cell reactivity in vitro. Moreover, CD4(+) cell counts increased in significantly less time. Finally, elimination of G-CSF-mediated immune suppression did not significantly increase the incidence of GVHD (< 15%). Thus, this study found that administration of G-CSF to recipients of T-cell-depleted hematopoietic transplants was associated with abnormal antigen-presenting cell functions and T-cell reactivity. Elimination of postgrafting administration of G-CSF prevented immune dysregulation and accelerated functional immune recovery.

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.

Innate and adaptive immunity in Candida albicans infections and saprophytism

Underlying acquired immunity to the fungus Candida albicans is usually present in adult immunocompetent individuals and is presumed to prevent mucosal colonization progressing to symptomatic infection. Exploration of immunological events leading to Candida resistance or susceptibility has indicated the central role of the innate and adaptive immune systems, the relative contribution of which may vary depending on the site of the primary infection. Nevertheless, acquired resistance to infection results from the development of Th1 responses. Cytokines produced by Thl cells activate phagocytic cells to a candidacidal state. In contrast, cytokines produced by Th2 cells inhibit Th1 development and deactivate phagocytic effector cells. Because reciprocal influences have been recognized between innate and adaptive Th immunity, it appears that an integrated immune response determines the life-long commensalism of the fungus at the mucosal level, as well as the transition from mucosal saprophyte to pathogen.