Host genetics and parasitic infections

Parasites still impose a high death and disability burden on human populations, and are therefore likely to act as selective factors for genetic adaptations. Genetic epidemiological investigation of parasitic diseases is aimed at disentangling the mechanisms underlying immunity and pathogenesis by looking for associations or linkages between loci and susceptibility phenotypes. Until recently, most studies used a candidate gene approach and were relatively underpowered, with few attempts at replicating findings in different populations. However, in the last 5 years, genome-wide and/or multicentre studies have been conducted for severe malaria, visceral leishmaniasis, and cardiac Chagas disease, providing some novel important insights. Furthermore, studies of helminth infections have repeatedly shown the involvement of common loci in regulating susceptibility to distinct diseases such as schistosomiasis, ascariasis, trichuriasis, and onchocherciasis. As more studies are conducted, evidence is increasing that at least some of the identified susceptibility loci are shared not only among parasitic diseases but also with immunological disorders such as allergy or autoimmune disease, suggesting that parasites may have played a role in driving the evolution of the immune system.     

Clinical usefulness of serological measurements obtained by antigen 60 in mycobacterial infections: Development of a new concept

Summary The humoral immune response occuring during mycobacterial infections was analysed with an ELISA test based on antigen 60. With tuberculosis, IgM antibodies indicate a primo-infection or a process of reactivation while IgG determinations allow an evaluation of the intensity of the infectious process. The test is also applicable to extrapulmonary tuberculosis, provided its sensitivity be adapted to these particular cases. This is particularly clear for tuberculous meningitis.The test is not species-specific and allows the detection of antibodies in atypical mycobacterioses and in leprosy patients. The final differentiation must be done by clinical examinations and cultures. In leprosy patients, IgM antibodies are detected nearly as frequently as IgG antibodies. In HIV-seropositive patients, the A60 seropositivity is correlated with a reactivation of former tuberculous infections and with primary tuberculous infections. At the AIDS stage, the A-60 seropositivity is due to atypical mycobacteria, with a better IgM than IgG response.Healthy people are negative in serology:the positive cases observed are due to inapparent infections gained by contact with an infectious focus. The seropositive cases observed in non-tuberculous hospitalized patients are restricted to some disease types, essentially lung infections (cystic fibrosis, cancer pneumopathies, sarcoidosis).Some patients have low levels of antibodies. This anergy may be traced to the formation of immune complexes or else to a weak avidity of the specific antibodies produced.This test should not be considered to be a diagnostic tool by itself. It should be used in conjunction with other diagnostic means that, together, allow the determination of a diagnosis.List of abbreviations IgG Immunoglobulin G - IgM Immunoglobulin M - A60 Mycobacterial antigen 60 - HIV Human Immunodeficiency Virus - AIDS Acquired Immunodeficiency Syndrome - ELISA Enzyme Linked Immunosorbent Assay - CSL Cerebro-spinal Liquid     

A common human TLR1 polymorphism regulates the innate immune response to lipopeptides

Toll-like receptors (TLR) are critical mediators of the immune response to pathogens and human polymorphisms in this gene family regulate inflammatory pathways and are associated with susceptibility to infection. Lipopeptides are present in a wide variety of microbes and stimulate immune responses through TLR1/2 or TLR2/6 heterodimers. It is not currently known whether polymorphisms in TLR1 regulate the innate immune response. We stimulated human whole blood with triacylated lipopeptide, a ligand for TLR1/2 heterodimers, and found substantial inter-individual variation in the immune response. We sequenced the coding region of TLR1 and found a non-synonymous polymorphism, I602S (base pair T1805G), that regulated signalling. In comparison to TLR1_602S, the 602I variant mediated substantially greater basal and lipopeptide-induced NF-kappaB signalling in transfected HEK293 cells. These signalling differences among TLR1 variants were also found with stimulation by extracts of Mycobacterium tuberculosis. Furthermore, individuals with the 602II genotype produced substantially more IL-6 than those with the 602SS variant in a lipopeptide-stimulated whole-blood cytokine assay. Together, these observations demonstrate that variation in the inflammatory response to bacterial lipopeptides is regulated by a common TLR1 transmembrane domain polymorphism that could potentially impact the innate immune response and clinical susceptibility to a wide spectrum of pathogens.     

Pathology of pulmonary tuberculosis and non-tuberculous mycobacterial lung disease: Facts,misconceptions, and practical tips for pathologists

Most pathologists are familiar with the microscopic features of tuberculosis and the need to examine special stains for acid-fast bacteria (AFB) in cases of granulomatous lung disease. However, misconceptions do exist, including the concept that finding AFB in “caseating granulomas” confirms the diagnosis of tuberculosis. This dogma is attributable to the high prevalence of tuberculosis in many countries, as well as unfamiliarity with the microscopic spectrum of non-tuberculous mycobacterial lung disease. This review aims to provide surgical pathologists with practical tips to identify AFB, illustrate the histologic overlap between pulmonary tuberculosis and non-tuberculous mycobacterial lung disease, and highlight the importance of cultures in this setting. M. tuberculosis and non-tuberculous mycobacteria cannot be reliably differentiated either on the basis of the tissue reaction or by bacterial morphology on acid-fast stains. Although a presumptive clinical diagnosis of tuberculosis can be made without culture-confirmation, the only definitive means to determine the true identity of AFB is by cultures or molecular methods. Making this distinction is most critical when AFB are found in incidentally detected lung nodules in geographic locations where the incidence of tuberculosis is low, because in such settings AFB in necrotizing granulomas of the lung are more likely to be non-tuberculous mycobacteria than M. tuberculosis.     

Etiology of acute viral respiratory infections common in Pakistan: A review

Respiratory infections, especially those of the lower respiratory tract, remain a foremost cause of mortality and morbidity of children greater than 5 years in developing countries including Pakistan. Ignoring these acute‐level infections may lead to complications. Particularly in Pakistan, respiratory infections account for 20% to 30% of all deaths of children. Even though these infections are common, insufficiency of accessible data hinders development of a comprehensive summary of the problem. The purpose of this study was to determine the prevalence rate in various regions of Pakistan and also to recognize the existing viral strains responsible for viral respiratory infections through published data. Respiratory viruses are detected more frequently among rural dwellers in Pakistan. Lower tract infections are found to be more lethal. The associated pathogens comprise respiratory syncytial virus (RSV), human metapneumovirus (HMPV), coronavirus, enterovirus/rhinovirus, influenza virus, parainfluenza virus, adenovirus, and human bocavirus. RSV is more dominant and can be subtyped as RSV‐A and RSV‐B (BA‐9, BA‐10, and BA‐13). Influenza A (H1N1, H5N1, H3N2, and H1N1pdm09) and Influenza B are common among the Pakistani population. Generally, these strains are detected in a seasonal pattern with a high incidence during spring and winter time. The data presented include pneumonia, bronchiolitis, and influenza. This paper aims to emphasise the need for standard methods to record the incidence and etiology of associated pathogens in order to provide effective treatment against viral infections of the respiratory tract and to reduce death rates.     

Inborn errors of immunity underlying a susceptibility to pyogenic infections: from innate immune system deficiency to complex phenotypes

BackgroundPyogenic bacteria are associated with a wide range of clinical manifestations, ranging from common and relatively mild respiratory and cutaneous infections to life-threatening localized or systemic infections, such as sepsis and profound abscesses. Despite vaccination and the widespread use of effective antibiotic treatment, severe infection is still observed in a subset of affected patients.ObjectivesWe aim to summarize the available data regarding inborn errors of immunity that result in a high risk of severe pyogenic infections.SourcesCase series, as well as review and original articles on human genetic susceptibility to pyogenic infections were examined.ContentWe review host-associated factors resulting in inborn errors of immunity and leading to a susceptibility to pyogenic infections, including deficiency in major components of the immune system (e.g., neutrophils, complement, immunoglobulin, and spleen function) and novel monogenic disorders resulting in specific susceptibility to pyogenic infection. Specifically, innate immune system deficiency involving toll-like receptors and associated signaling typically predispose to a narrow spectrum of bacterial diseases in otherwise healthy people, making a diagnosis more difficult to suspect and confirm. More complex syndromes, such as hyper IgE syndrome, are associated with a high risk of pyogenic infections due to an impairment of the interleukin-6 or -17 signaling, demonstrating the pivotal role of these pathways in controlling bacterial infections.ImplicationsIn clinical practice, awareness of such conditions is essential, especially in the pediatric setting, to avoid a potentially fatal diagnostic delay, set the most proper and prompt treatment, and ensure prevention of severe complications.     

Comparison of reporting phase III randomized controlled trials of antibiotic treatment for common bacterial infections in ClinicalTrials.gov and matched publications

ObjectivesDiscrepancies between ClinicalTrials.gov entries and matching publications were previously described in general medicine. We aimed to evaluate the consistency of reporting in trials addressing systemic antibiotic therapy.MethodsWe searched ClinicalTrials.gov for completed phase III trials comparing antibiotic regimens until May 2017. Matched publications were identified in PubMed. Two independent reviewers extracted data and identified inconsistencies. Reporting was assessed among studies started before and after 1 July 2005, when the International Committee of Medical Journal Editors (ICMJE) required mandatory registration as a prerequisite for considering a trial for publication.ResultsMatching publications were identified for 75 (70%) of 107 ClinicalTrials.gov entries. Median time from study completion to publication was 26 months (interquartile range 19–42). Primary outcome definition was inconsistent between ClinicalTrials.gov and publications in seven trials (7/72, 10%) and reporting of the primary outcome timeframe was inconsistent in 14 (14/71, 20%). Secondary outcomes definitions were inconsistent in 36 trials (36/66, 55%). Reporting of inclusion criteria and study timeline were inconsistent in 17% (13/65) and 3% (2/65), respectively. Trials started after July 2005 were significantly less likely to have reporting inconsistencies and were published in higher impact factor journals.ConclusionsWe found a lower inconsistency rate of outcome reporting compared with other medical disciplines. Reporting completeness and consistency were significantly better after July 2005. The ICMJE requirement for mandatory registration was associated with significant improvement in reporting quality in infectious diseases trials. Prolonged time lag to publication and missing data from unpublished trials should raise a discussion on current reporting and publishing procedures.     

Epidemiology of Clostridium difficile-associated infections

Clostridium difficile is responsible for 15–25% of cases of antibiotic-associated diarrhea (AAD) and for virtually all cases of antibiotic-associated pseudomembranous colitis (PMC). This anaerobic bacterium has been identified as the leading cause of nosocomial infectious diarrhea in adults and can be responsible for large outbreaks. Nosocomial C. difficile infection results in an increased length of stay in hospital ranging from 8 to 21 days. Risk factors for C. difficile -associated diarrhea include antimicrobial therapy, older age (>65 years), antineoplastic chemotherapy and length of hospital stay. Other interventions with high risk associations are enemas, nasogastric tubes, gastrointestinal surgery and antiperistaltic drugs. Prospective studies have shown that nosocomial transmission of C. difficile is frequent but often remains asymptomatic. Patients can be contaminated from environnemental surfaces, shared instrumentation, hospital personnel hands and infected roommates. Once an outbreak starts, C. difficile may be spread rapidly throughout the hospital environment where spores may persist for months. Measures that are effective in reducing incidence of C. difficile infections and cross-infection include: (i) an accurate and rapid diagnosis, (ii) appropriate treatment, (iii) implementation of enteric precautions for symptomatic patients, (iv) reinforcement of hand-washing, (v) daily environmental disinfection, and (vi) a restrictive antibiotic policy. C. difficile is a common cause of infectious diarrhea and should be therefore systematically investigated in patients with nosocomial diarrhea.     

How to: Diagnose inborn errors of intrinsic and innate immunity to viral,bacterial, mycobacterial,and fungal infections

BackgroundInborn errors of intrinsic and innate immunity constitute the focus of a growing research field that investigates the molecular mechanisms underlying susceptibility to infections previously not considered part of the spectrum of inborn errors of immunity. These so-called nonconventional inborn errors of immunity often occur as infections caused by a narrow spectrum of microorganisms in otherwise healthy subjects.ObjectivesThis review aimed to provide a framework for identifying and evaluating patients with viral, bacterial, mycobacterial, and fungal infection needing further assessment for inborn errors of intrinsic and innate immunity.SourcesA literature search was performed using PubMed, from inception until 1 May 2022. The search included the following keywords: “inborn errors of immunity”; “inborn errors of innate immunity”; “primary immune deficiency”; “primary immunodeficiency”; “infections”; “infectious susceptibility”; “virus”; “pyogenic bacteria”; “mycobacteria”; “fungi”. All article types were considered.ContentWe review the definition of what can be considered an inborn error of immunity and how the definition changed over the last ～25 years. We further provide criteria to rule out secondary immunodeficiencies, identify patients needing further clinical and laboratory immunological assessment, and suspect and diagnose an inborn error of intrinsic and innate immunity. These steps are proposed as part of an algorithm.ImplicationsPatients with unexplained life-threatening infections, including otherwise healthy subjects, should be systematically screened for known inborn errors of immunity. The early diagnosis can prevent recurrence of life-threatening infections in the patients and reduce the total burden of infectious diseases.     

Risk of hepatitis B and C infections in Tehranian wrestlers

Context:

Although bloodborne infections are among the most important global health issues, limited data are available on bloodborne infections in athletes.

Objective:

To determine and compare the prevalence of markers of hepatitis B (HBV) and hepatitis C (HCV) viruses and the risk factors for these infections among wrestlers in Tehran and among a control group of athletes in the same geographic area who took part in low- to moderate-contact sports (ie, volleyball and soccer).

Design:

Case-control study.

Setting:

Laboratory.

Patients or Other Participants:

A total of 420 male wrestlers were randomly selected from 28 wrestling clubs in Tehran using a cluster-sample–setting method. The control group (205 volleyball players from 21 clubs and 205 soccer players from 16 clubs) was selected from the same geographic area.

Main Outcome Measure(s):

The risk factors for HBV and HCV and serum levels of anti-HBcAg (antibodies to the HBV core antigen), HBsAg (HBV surface antigen), and anti-HCV (antibodies to HCV) in both groups.

Results:

The prevalence of anti-HBcAg was 13.4% (95% confidence interval [CI] = 10.2%, 16.7%) in wrestlers and 10.9% (95% CI = 7.9%, 14.0%) in the control group. The prevalence of HBsAg was 1.2% (95% CI = 0.2%, 2.2%) in wrestlers and 0.5% (95% CI = −0.2%, 1.2%) in the control group. The prevalence of anti-HCV was 0.5% (95% CI = −0.2%, 1.1%) in wrestlers and 0 in the control group. Some risk factors for bloodborne infections were more common in the wrestlers than in the control group.

Conclusions:

Within the limits of our study, we found no evidence that participation in Tehranian wrestling increased HBV or HCV transmission when compared with transmission in athletes participating in low- to moderate-contact sports. Prevention of bloodborne infections in Tehranian wrestlers should be focused not only on appropriate care for bleeding injuries but also on general risk factors for these conditions.     

Mendelian and complex genetics of susceptibility and resistance to parasitic infections

Uncovering the complex genetic basis of susceptibility and resistance to parasitic infectious diseases is an enormous challenge. It probably involves many different host genes, interacting with multiple parasite genetic and environmental factors. Several genes of interest have been identified by family and association studies in humans and by using mouse models, but more robust epidemiological studies and functional data are needed to authenticate these findings. With new technologies and statistical tools for whole-genome association analysis, the next few years are likely to see acceleration in the rate of gene discovery, which has the potential to greatly assist drug and vaccine development.     

Immune regulation of gammadelta T cell responses in mycobacterial infections

Antigen-specific gammadelta T cells may play a role in anti-mycobacterial immunity. Studies done in humans and animal models have demonstrated complex patterns of gammadelta T cell immune responses during early mycobacterial infections and chronic tuberculosis. Recent studies have also shown a clinical correlation between major recall expansion of antigen-specific gammadelta T cells and immunity against fatal early mycobacterial diseases. Multiple host and microbial factors can regulate diverse immune responses of phosphoantigen-specific gammadelta T cells during mycobacterial infections.     

MF59 adjuvant enhances the immunogenicity and protective immunity of the OmpK/Omp22 fusion protein from Acineterbacter baumannii through intratracheal inoculation in mice

Acinetobacter baumannii (A baumannii) is an emerging nosocomial pathogenic bacterium which leads to hospital infections. The increase in drug‐resistant A baumannii strains makes it difficult to control by using common antibiotics. The development of effective vaccines is an alternative means to avoid A baumannii infections. In the present study, Balb/c mice were inoculated intratracheally with 30 μg of OmpK/Omp22 fusion protein alone or OmpK/Omp22 formulated with MF59 adjuvant. After two times of boosting at day 14 and 21, the antigen‐specific antibody levels and the protective immunity against A baumannii challenge were evaluated. The results showed that the OmpK/Omp22 formulated with MF59 immunized mice produced much higher level of antigen‐specific antibodies compared to mice immunized with OmpK/Omp22 alone (P < 0.01). Mice immunized with 30 μg of OmpK/Omp22 formulated with MF59 also provided more potent protection post‐challenge, which showed lower bacterial loads in the blood and lung tissue, lower level of blood inflammatory cytokines and higher survival rate (83.3%) than mice immunized with OmpK/Omp22 alone (P < 0.001). In conclusion, this study demonstrated that OmpK/Omp22 fusion protein adjuvanted with MF59 induced superior immune response and better protection than OmpK/Omp22 alone through intratracheal inoculation in mice .     

Restoration of innate immune activation accelerates Th1‐cell priming and protection following pulmonary mycobacterial infection

The immune mechanisms underlying delayed induction of Th1‐type immunity in the lungs following pulmonary mycobacterial infection remain poorly understood. We have herein investigated the underlying immune mechanisms for such delayed responses and whether a selected innate immune‐modulating strategy can accelerate Th1‐type responses. We have found that, in the early stage of pulmonary infection with attenuated Mycobacterium tuberculosis (M.tb H37Ra), the levels of infection in the lung continue to increase logarithmically until days 14 and 21 postinfection in C57BL/6 mice. The activation of innate immune responses, particularly DCs, in the lung is delayed. This results in a delay in the subsequent downstream immune responses including the migration of antigen‐bearing DCs to the draining lymph node (dLN), the Th1‐cell priming in dLN, and the recruitment of Th1 cells to the lung. However, single lung mucosal exposure to the TLR agonist FimH postinfection is able to accelerate protective Th1‐type immunity via facilitating DC migration to the lung and draining lymph nodes, enhancing DC antigen presentation and Th1‐cell priming. These findings hold implications for the development of immunotherapeutic and vaccination strategies and suggest that enhancement of early innate immune activation is a viable option for improving Th1‐type immunity against pulmonary mycobacterial diseases.     

Immunohistochemical analysis of local immunity in salmonella and shigella infections

Laboratory of Pathomorphology and Immunology, Research Institute of Epidemiology, Microbiology, and Infectious Diseases, Ministry of Health of the Uzbek SSR, Tashkent. Laboratory for the Study of Intercellular Interactions, I. M. Sechenov Moscow Medical Academy. (Presented by Academician of the Academy of Medical Sciences of the USSR N. P. Bochkov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 11, pp. 509–511, November, 1991.     

Human genetics of adiponectin in the metabolic syndrome

Adiponectin, an adipose-derived plasma protein, has been well established to be an important biomarker for metabolic syndrome and its complications after exhausted studies in humans. Animal and cell culture experiments also support most claims from human observations of its roles in the metabolic syndrome. Reproducible results of human genetic studies of diverse ethnic origin and by different investigators may provide the evidence for its causative roles in the pathogenesis of the metabolic syndrome and further insight into the genetic constitutions of the metabolic syndrome. Some of the common polymorphisms in the promoter region, exon and intron 2, and the rare nonsynonymous mutations in exon 3 of the human adiponectin gene were repeatedly shown in many studies from many different ethnic populations to associate with the phenotypes related to body weight, glucose metabolism, insulin sensitivity, and risk of type 2 diabetes mellitus and coronary artery disease. The association of adiponectin genetic variations with dyslipidemia and blood pressure was less explored. The common polymorphisms and rare mutations of the human adiponectin gene itself were demonstrated to associate with differential expression of adiponectin at the plasma protein level and mRNA level in adipose tissue. The PPARγ2 Pro12Ala variants were also shown to influence insulin sensitivity in interaction with adiponectin genotype or to influence plasma adiponectin levels. However, the results were not consistent. Three genome-wide scans for the loci that regulate plasma adiponectin concentration suggest further exploration on chromosomes 5, 9, 14, 15, and 18 is required. These human genetic studies on adiponectin and the metabolic syndrome strongly suggest that adiponectin is one of the causative factors in its pathogenesis and provide significant insights into the genetic makeup of the metabolic syndrome. Extension from these studies may accelerate the discovery of new molecular targets for future therapeutic interventions.     

Mycobacterial infections in adult recipients of allogeneic hematopoietic stem cell transplantation: A cohort study in a high endemic area

BackgroundMycobacterial infections are important and potentially life-threatening complications after organ transplantations. Notably, for the recipients of allogeneic hematopoietic stem cell transplantation (HSCT), there are a few supporting results to explore post-transplant mycobacterial infections. Taiwan is a high endemic area of the infection. We aim to investigate the incidence, risk factors, and survival of post-transplant mycobacterial infections, including mycobacterium tuberculosis (MTB) and non-tuberculous mycobacterium (NTM).MethodsWe included 422 adult patients undergoing allogeneic HSCT at an Asian tertiary medical center between January 2003 and December 2014. A total 26 subjects developed post-transplant mycobacterial infections. Risk factors, clinical features, and survival for post-transplant mycobacterial infections were collected and analyzed.ResultsPost-transplant mycobacterial infections occurred in 26 (6.2%) of 422 HSCT patients. Two-year cumulative incidences in MTB and NTM were 1.4% and 5.4%. In the multivariate analysis, being age >45 years (adjusted HR 2.21, 95% CI 1.01–4.83) and extensive chronic graft-versus-host disease (cGVHD) (adjusted HR 4.95, 95% CI 2.14–11.46) were identified as independent risk factors of infections. There was a trend as a risk factors in relapsed patients (P = 0.088). For patients with cGVHD, there was a significant difference of post-transplant survival between mycobacterial infections and none (P = 0.036). Pneumonia contributed most to mortality (n = 11, 42.3%).ConclusionMycobacterial infections are worth to note in a high endemic area. Once a high-risk group is identified, much effort is required to target new approaches for prevention, early detection and treatment of infections.