Humoral response to HspX and GlcB to previous and recent infection by Mycobacterium tuberculosis

Prevalence of latent tuberculosis infection (LTBI) in healthcare workers in Latin America and the Caribbean: systematic review and meta-analysis

Background

Tuberculosis remains a significant global health concern, and healthcare workers (HCWs) face a high risk of acquiring latent tuberculosis infection (LTBI) through occupational exposure. In the Latin American and Caribbean (LAC) region, where the burden of tuberculosis is substantial, understanding the prevalence of LTBI among HCWs is crucial for effective infection control measures. Therefore, we conducted a systematic review and meta-analysis to estimate the prevalence of LTBI among HCWs in LAC countries.

Methods

Our search included MEDLINE, Scopus, EMBASE, Web of Science, and Google Scholar databases, focusing on relevant English-language records. We looked for observational studies from inception until December 2023.

Results

Our analysis included 38 studies representing 15,236 HCWs and 6,728 LTBI cases. These studies spanned the period from 1994 to 2023 and were conducted in Brazil, Peru, Cuba, Colombia, Trinidad and Tobago, Mexico, and Chile. The mean prevalence of LTBI among HCWs was 35.32% (range 17.86-56.00%) for interferon-gamma release assay (IGRA) and 43.67% (range 6.68-70.29%) for tuberculin skin test (TST). The pooled prevalence of LTBI among HCWs was 34.5% (95% CI 25.4-44.1%) for IGRA and 43.0% (95% CI 35.5-50.7%) for TST. When considering both IGRA and TST tests, the overall prevalence of LTBI among HCWs was 40.98% (95% CI 34.77-47.33%). LTBI was associated with longer lengths of employment and exposure to patients, family members, or any person with TB. Additionally, older HCWs faced a higher risk of LTBI. Specific professional roles (such as nurses, nurse technicians, or physicians), smoking, and deficient TB infection control measures increased the likelihood of LTBI. However, information regarding gender and BCG vaccination status showed discordance among studies.

Conclusion

Our findings underscore a substantial burden of LTBI among HCWs in LAC countries. Implementing adequate infection control measures is essential to prevent and control transmission within healthcare settings.

Evaluating the Performance of PPE44, HSPX, ESAT-6 and CFP-10 Factors in Tuberculosis Subunit Vaccines

Mycobacterium tuberculosis (M. tuberculosis) is an intracellular pathogen causing long-term infection in humans that mainly attacks macrophages and can escape from the immune system with the various mechanisms. The only FDA-approved vaccine against M. tuberculosis (MTB) is Mycobacterium bovis bacillus Calmette-Guérin (BCG). The protection of this vaccine typically lasts 10–15 years. Due to the increasing number of people becoming ill with MTB each year worldwide, the need to develop a new effective treatment against the disease has been increased. During the past two decades, the research budget for TB vaccine has quadrupled to over half a billion dollars. Most of these research projects were based on amplifying and stimulating the response of T-cells and developing the subunit vaccines. Additionally, these studies have demonstrated that secretory and immunogenic proteins of MTB play a key role in the pathogenesis of the bacteria. Therefore, these proteins were used to develop the new subunit vaccines. In this review, based on the use of these proteins in the successful new subunit vaccines, the PPE44, HSPX, CFP-10 and ESAT-6 antigens were selected and the role of these antigens in designing and developing new subunit vaccines against TB and for the prevention of TB were investigated.

Detection and Quantification of HspX Antigen in Sputum Samples Using Plasmonic Biosensing: Toward a Real Point-of-Care (POC) for Tuberculosis Diagnosis

Advancements that occurred during the last years in the diagnosis of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis infection, have prompted increased survival rates of patients. However, limitations related to the inefficiency of an early detection still remain; some techniques and laboratory methods do not have enough specificity and most instruments are expensive and require handling by trained staff. In order to contribute to a prompt and effective diagnosis of tuberculosis, we report the development of a portable, user-friendly, and low-cost biosensor device for its early detection. By using a label-free surface plasmon resonance (SPR) biosensor, we have established a direct immunoassay for the direct detection and quantification of the heat shock protein X (HspX) of Mtb, a well-established biomarker of this pathogen, directly in pretreated sputum samples. The method relies on highly specific monoclonal antibodies that are previously immobilized on the plasmonic sensor surface. This technology allows for the direct detection of the biomarker without amplification steps, showing a limit of detection (LOD) of 0.63 ng mL^-1 and a limit of quantification (LOQ) of 2.12 ng mL^-1. The direct analysis in pretreated sputum shows significant differences in the HspX concentration in patients with tuberculosis (with concentration levels in the order of 116-175 ng mL^-1) compared with non-tuberculosis infected patients (values below the LOQ of the assay).

Immune responses to Mycobacterium tuberculosis membrane-associated antigens including alpha crystallin can potentially discriminate between latent infection and active tuberculosis disease

Changes in expression of membrane antigens may accompany the transition of Mycobacterium tuberculosis (Mtb) from ‘dormant’ to ‘active’ states. We have determined whether antibody and T cell responses to Mtb membrane (MtM)-associated antigens, especially the latency-induced protein alpha crystallin (Acr), can discriminate between latent tuberculosis infection (LTBI) and active TB (ATB) disease. Study subjects comprised a previously described cohort of healthcare workers (HCWs, n = 43) and smear-positive ATB patients (n = 10). HCWs were further categorized as occupational contacts (OC, n = 30), household contacts of TB (HC, n = 8) and cured TB (CTB, n = 5). Levels (ΔOD) of serum antibody isotypes (IgG, IgA and IgM) were determined by ELISA and blood T cell proliferative responses were determined by flow cytometry using Ki67 protein as marker for DNA synthesis. Antibodies to MtM and Acr were predominantly IgG and their levels in HCWs and ATB did not differ significantly. However, HCWs showed a significantly higher level of anti-MtM IgM and a significantly lower level of anti-Acr IgA antibodies than the ATB patients. Also, a larger proportion of HCWs showed a high (>1) ΔOD_Acr/ΔOD_MtM ratio for IgG. HCWs also showed a higher, though not significantly different from ATB, avidity of anti-MtM (IgG) antibodies. A higher proportion of HCWs (35% of OC, 62.5% of HC and 20% of CTB), compared with ATB (10%) showed a positive T cell response to Acr along with significant difference (P <0.05) between HC and ATB. A significant correlation (r = 0.60, P <0.0001) was noted between T cell responses of HCWs towards Acr and MtM (reported earlier by us) and both responses tended to decline with rising exposure to the infection. Even so, positive responses to Acr (38.5%) were significantly lower than to MtM (92%). Neither antibody nor T cell responses to either antigen appeared affected by BCG vaccination or reactivity to tuberculin. Results of the study suggest that the levels of IgM antibodies to MtM, IgA antibodies to Acr and proliferative T cell responses to both the antigens can potentially discriminate between LTBI and active TB disease. They also underscore the necessity of SOPs for antibody assays.

Latent tuberculosis infection in healthcare workers in low- and middle-income countries: an updated systematic review

Healthcare workers (HCWs) are at increased risk of latent tuberculosis (TB) infection (LTBI) and TB disease.We conducted an updated systematic review of the prevalence and incidence of LTBI in HCWs in low- and middle-income countries (LMICs), associated factors, and infection control practices. We searched MEDLINE, Embase and Web of Science (January 1, 2005-June 20, 2017) for studies published in any language. We obtained pooled estimates using random effects methods and investigated heterogeneity using meta-regression.85 studies (32 630 subjects) were included from 26 LMICs. Prevalence of a positive tuberculin skin test (TST) was 14-98% (mean 49%); prevalence of a positive interferon-γ release assay (IGRA) was 9-86% (mean 39%). Countries with TB incidence ≥300 per 100 000 had the highest prevalence (TST: pooled estimate 55%, 95% CI 41-69%; IGRA: pooled estimate 56%, 95% CI 39-73%). Annual incidence estimated from the TST was 1-38% (mean 17%); annual incidence estimated from the IGRA was 10-30% (mean 18%). The prevalence and incidence of a positive test was associated with years of work, work location, TB contact and job category. Only 15 studies reported on infection control measures in healthcare facilities, with limited implementation.HCWs in LMICs in high TB incidence settings remain at increased risk of acquiring LTBI. There is an urgent need for robust implementation of infection control measures.

Mycobacterium tuberculosis Reporter Strains as Tools for Drug Discovery and Development

Reporter strains have proven to be powerful tools to study Mycobacterium tuberculosis (Mtb) physiology. Transcriptional and translational reporter strains are engineered by fusing a readout gene, encoding a fluorescent, luminescent or enzymatic protein, downstream of a promoter or in-frame with a gene of interest. When the reporter is expressed, it generates a signal that acts as a synthetic phenotype, enabling the study of physiologies that might have otherwise been hidden. This review will discuss approaches for generating reporter strains in Mtb and how they can be used as tools for high-throughput genetic and small molecule screening and as biomarkers for examining Mtb responses to drug or immune stresses during animal infections. Fluorescent reporter strains have an added benefit in that they can be used for single-cell studies both in vitro and in vivo, thus enabling the study of mechanisms underlying phenotypic heterogeneity. Recent examples of the use of Mtb reporter strains will be presented with a focus on how they can be used as tools for drug discovery and development. © 2018 IUBMB Life, 70(9):818-825, 2018.

ORFeome-based identification of biomarkers for serodiagnosis of Mycobacterium tuberculosis latent infection

BACKGROUND

The challenges posed by Mycobacterium tuberculosis infection require the gradual removal of the pool of latent tuberculosis infection (LTBI). The current cell-immune-based diagnostic tests used to identify LTBI individuals have several irreversible drawbacks. In the present study, we attempted to identify novel diagnostic antigens for LTBI.

METHODS

A high-throughput glutathione S-transferase (GST)-fusion technology was used to express over 409 TB proteins and sera from LTBI and healthy individuals was used to interrogate these GST-TB fusion proteins.

RESULTS

Of 409 TB proteins, sixty-three reacted seropositive and defined the immuno-ORFeome of latent M. tuberculosis. Within the immuno-ORFeome, the rare targets were predominantly latency-associated proteins and secreted proteins, while the preferentially recognized antigens tended to be transmembrane proteins. Six of novel highly-reactive antigens had the potential to distinguish LTBI from active TB and healthy individuals. A multiple-antigen combination set was selected through analysis of various combinations. A panel of 94 archived serum samples was used to validate the diagnostic performance of the multiple-antigen combination set, which had sensitivity of 66.1% (95% CI 52.9, 77.4) and specificity of 87.5% (95% CI 70.1, 95.1).

CONCLUSION

These results provide experimental evidence of the immunogenicity of novel TB proteins that are suitable for the development of serodiagnostic tools for LTBI.

Detection of anti-HspX antibodies and HspX protein in patient sera for the identification of recent latent infection by Mycobacterium tuberculosis

Mycobacterium tuberculosis is a pathogen causing tuberculosis (TB) a spectrum of disease including acute and asymptomatic latent stages. Identifying and treating latently-infected patients constitutes one of the most important impediments to TB control efforts. Those individuals can remain undiagnosed for decades serving as potential reservoirs for disease reactivation. Tests for the accurate diagnosis of latent infection currently are unavailable. HspX protein (α-crystallin), encoded by Rv2031c gene, is produced in vitro by M. tuberculosis during stationary growth phase and hypoxic or acidic culture conditions. In this study, using standard, and Luminex xMAP® bead capture ELISA, respectively, we report on detection of anti-HspX IgG and IgM antibodies and HspX protein in sera from acute and latent TB patients. For the antibody screen, levels of IgG and IgM antibodies were similar between non-infected and active TB patients; however, individuals classified into the group with latent TB showed higher values of anti-HspX IgM (p = 0.003) compared to active TB patients. Using the bead capture antigen detection assay, HspX protein was detected in sera from 56.5% of putative latent cases (p< 0.050) compared to the background median with an average of 9,900 pg/ml and a range of 1,000 to 36,000 pg/ml. Thus, presence of anti-HspX IgM antibodies and HspX protein in sera may be markers of latent TB.

Identification of specific antibodies against the Ag85C-MPT51-HspX fusion protein (CMX) for serological screening of tuberculosis in endemic area

OBJECTIVES

Development of new tools for rapid and accurate diagnosis of tuberculosis (TB) is considered a strategy for controlling the disease. The recombinant CMX fusion protein is composed of immunodominant epitopes of the Ag85C (Rv0129c), MPT51 (Rv3803c) and the entire HspX (Rv2031c) proteins from Mycobacterium tuberculosis H37Rv (Mtb). The aim of this study was to evaluate the applicability of a test using the CMX protein in individuals suspected of TB.

METHODS

Indirect ELISA was used to measure serum anti-CMX IgM and IgG in individuals with pulmonary TB.

RESULTS

Patients with pulmonary TB had higher titers of IgM (OD = 0.502 ± 0.281) than healthy controls (OD = 0.200 ± 0.125). The cutoff for IgM-ELISA was determined using ROC curve analyzes (AUC = 0.868) with a sensitivity of 80.1% and a specificity of 78.2%. Patients with pulmonary TB also had higher titers of IgG (OD = 0.525 ± 0.391) than healthy controls (OD = 0.215 ± 0.077). The cutoff for IgG-ELISA was determined using ROC curve analyzes (AUC = 0.864) with a sensitivity of 81.7% and a specificity of 74.7%.

CONCLUSION

The results suggest that the recombinant protein CMX can be used in a serological test to complement the screening of individuals suspected of having active pulmonary TB.

Prevalence of Latent Tuberculosis among Health Care Workers in High Burden Countries: A Systematic Review and Meta-Analysis

Background

Tuberculosis is one of the leading causes of death worldwide. Twenty-two high burden countries contributed to the majority of worldwide tuberculosis cases in 2015. Health care workers are at high risk of acquiring tuberculosis through occupational exposure.

Objective

To estimate the prevalence of latent tuberculosis infection (LTBI) among health care workers in high burden countries.

Methods

Databases including MEDLINE (Ovid), EMBASE (Ovid), CINAHL (Ovid) and ISI Web of Science (Thompson-Reuters), and grey literature were searched for English language records on relevant medical subject headings (MeSH) terms of LTBI and health care providers. Literature was systematically reviewed using EPPI-Reviewer4 software. Prevalence and incidence of LTBI and 95% confidence intervals (CI) were reported. Pooled prevalence of LTBI and 95% CI were calculated using random-effects meta-analysis models and heterogeneity was assessed using I² statistics. Sub-group analysis was conducted to assess the cause of heterogeneity.

Results

A total of 990 records were identified. Of those, 18 studies from only 7 high burden countries representing 10,078 subjects were included. Tuberculin skin test results were available for 9,545 participants. The pooled prevalence of LTBI was 47% (95% CI 34% to 60%, I² = 99.6%). In subgroup analyses according to the country of the study, the pooled prevalence of LTBI was lowest in Brazil (37%) and highest in South Africa (64%). The pooled prevalence of LTBI among medical and nursing students was 26% (95% CI 6% to 46%, I² = 99.3%) while the prevalence among all types of health care workers was 57% (95% CI 44% to 70%, I² = 99.1%). Incidence of LTBI was available for health care workers in four countries. The cumulative incidence ranged from 2.8% in Brazilian medical students to 38% among all types of health care workers in South Africa.

Conclusion

The findings of this study suggest that there is a high burden of LTBI among health care workers in high burden countries. Adequate infection control measures are warranted to prevent and control transmission in health care settings.

Challenging Mycobacterium tuberculosis dormancy mechanisms and their immunodiagnostic potential

Mycobacterium tuberculosis is the etiologic agent of tuberculosis, one of the world's greatest cause of morbidity and mortality due to infectious disease. Many evolutionary mechanisms have contributed to its high level of adaptation as a host pathogen. Prior to become dormant, a group of about 50 genes related to metabolic changes are transcribed by the DosR regulon, one of the most complex and important systems of host-pathogen interaction. This genetic mechanism allows the mycobacteria to persist during long time periods, establishing the so-called latent infection. Even in the presence of a competent immune response, the host cannot eliminate the pathogen, only managing to keep it surrounded by an unfavorable microenvironment for its growth. However, conditions such as immunosuppression may reestablish optimal conditions for bacterial growth, culminating in the onset of active disease. The interactions between the pathogen and its host are still not completely elucidated. Nonetheless, many studies are being carried out in order to clarify this complex relationship, thus creating new possibilities for patient approach and laboratory screening.

The use of Mycobacterium tuberculosis HspX and GlcB proteins to identify latent tuberculosis in rheumatoid arthritis patients

Understanding the social conditions and immunological characteristics that allow some human immunodeficiency virus (HIV)-exposed patients to remain uninfected represents an on-going challenge. In this study, the socio-demographic and sexual behaviour characteristics and immune activation profiles of uninfected individuals exposed to HIV-infected partners were investigated. A confidential and detailed questionnaire was administered and venous blood was tested using HIV-1/enzyme immunoassays, plasma HIV-1 RNA levels/bDNA and immunophenotyping/flow cytometry to determine the frequencies of CD4 and CD8 T cells expressing activation markers. The data analysis showed significant differences (p < 0.05) for immune parameters in individuals who were uninfected, albeit exposed to HIV-infected partners, compared with unexposed individuals. In particular, the exposed, uninfected individuals had a higher frequency (median, minimum-maximum) of CD4⁺HLA-DR⁺ (4.2, 1.8-6.1), CD8⁺HLA-DR⁺ (4.6, 0.9-13.7), CD4⁺CD45RO⁺ (27.5, 14.2-46.6), CD4⁺CD45RO⁺CD62L⁺ (46.7, 33.9-67.1), CD8⁺CD45RA⁺HLA-DR⁺ (12.1, 3.4-35.8) and CD8⁺CD45RO⁺HLA-DR⁺ (9.0, 3.2-14.8) cells, a decreased percentage of CD8⁺CD28⁺ cells (11.7, 4.5-24.0) and a lower cell-surface expression of Fcγ-R/CD16 on monocytes (56.5, 22.0-130.0). The plasma HIV-1 RNA levels demonstrated detectable RNA virus loads in 57% of the HIV-1⁺ female partners. These findings demonstrate an activation profile in both CD4 and CD8 peripheral T cells from HIV-1 exposed seronegative individuals of serodiscordant couples from a referral centre in Belo Horizonte, state of Minas Gerais.

The use of Mycobacterium tuberculosis HspX and GlcB proteins to identify latent tuberculosis in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is an autoimmune disease characterised by the destruction of articular cartilage and bone damage. The chronic treatment of RA patients causes a higher susceptibility to infectious diseases such as tuberculosis (TB); one-third of the world’s population is latently infected (LTBI) with Mycobacterium tuberculosis (Mtb). The tuberculin skin test is used to identify individuals LTBI, but many studies have shown that this test is not suitable for RA patients. The goal of this work was to test the specific cellular immune responses to the Mtb malate synthase (GlcB) and heat shock protein X (HspX) antigens of RA patients and to correlate those responses with LTBI status. The T-helper (Th)1, Th17 and Treg-specific immune responses to the GlcB and HspX Mtb antigens were analysed in RA patients candidates for tumour necrosis factor-α blocker treatment. Our results demonstrated that LTBI RA patients had Th1-specific immune responses to GlcB and HspX. Patients were followed up over two years and 14.3% developed active TB. After the development of active TB, RA patients had increased numbers of Th17 and Treg cells, similar to TB patients. These results demonstrate that a GlcB and HspX antigen assay can be used as a diagnostic test to identify LTBI RA patients.

A new recombinant BCG vaccine induces specific Th17 and Th1 effector cells with higher protective efficacy against tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) that is a major public health problem. The vaccine used for TB prevention is Mycobacterium bovis bacillus Calmette-Guérin (BCG), which provides variable efficacy in protecting against pulmonary TB among adults. Consequently, several groups have pursued the development of a new vaccine with a superior protective capacity to that of BCG. Here we constructed a new recombinant BCG (rBCG) vaccine expressing a fusion protein (CMX) composed of immune dominant epitopes from Ag85C, MPT51, and HspX and evaluated its immunogenicity and protection in a murine model of infection. The stability of the vaccine in vivo was maintained for up to 20 days post-vaccination. rBCG-CMX was efficiently phagocytized by peritoneal macrophages and induced nitric oxide (NO) production. Following mouse immunization, this vaccine induced a specific immune response in cells from lungs and spleen to the fusion protein and to each of the component recombinant proteins by themselves. Vaccinated mice presented higher amounts of Th1, Th17, and polyfunctional specific T cells. rBCG-CMX vaccination reduced the extension of lung lesions caused by challenge with Mtb as well as the lung bacterial load. In addition, when this vaccine was used in a prime-boost strategy together with rCMX, the lung bacterial load was lower than the result observed by BCG vaccination. This study describes the creation of a new promising vaccine for TB that we hope will be used in further studies to address its safety before proceeding to clinical trials.

IgG, IgM and IgA antibodies against the novel polyprotein in active tuberculosis

BACKGROUND

The present study was aimed to evaluate whether IgG, IgM and IgA antibodies levels detected against a novel Mycobacterium tuberculosis polyprotein 38 F-64 F (with 38 F being the abbreviation for 38kD-ESAT6-CFP10 and 64 F for Mtb8.4-MPT64-TB16.3-Mtb8) are suitable for diagnosing active tuberculosis, and for monitoring the efficacy of chemotherapy on TB patients.

METHODS

In this study, a total of 371 active TB patients without treatment were selected and categorized into S+/C+group (n=143), S-/C+group (n=106) or S-/C- group (n=122). A series of serum samples were collected from 82 active TB patients who had undergone anti-TB chemotherapy for 0-6 months at one month interval. Humoral responses (IgG, IgM and IgA) were determined for the novel Mycobacterium tuberculosis polyprotein using indirect ELISA methods in all of serum samples.

RESULTS

For S+/C+, S-/C+and S-/C- active tuberculosis patients before anti-TB chemotherapy, the sensitivities of tests based on IgG were 65.7%, 46.2% and 52.5% respectively; the sensitivities based on IgM were 21.7%, 24.5% and 18.9%; and the sensitivities based on IgA were 25.2%, 17.9% and 23.8%. By combination of three isotypes, for all active tuberculosis patients, the test sensitivity increased to 70.4% with the specificity being 91.5%. After anti-TB chemotherapy, there were no significant differences between groups with different courses of anti-TB chemotherapy.

CONCLUSIONS

The novel Mycobacterium tuberculosis polyprotein 38 F-64 F represents potential antigen suitable for measuring IgG, IgM and IgA antibodies. However, the serodiagnostic test based on the 38 F-64 F polyprotein appears unsuitable for monitoring the efficacy of chemotherapy.

IgG, IgM and IgA antibodies against the novel polyprotein in active tuberculosis

BACKGROUND

The present study was aimed to evaluate whether IgG, IgM and IgA antibodies levels detected against a novel Mycobacterium tuberculosis polyprotein 38 F-64 F (with 38 F being the abbreviation for 38kD-ESAT6-CFP10 and 64 F for Mtb8.4-MPT64-TB16.3-Mtb8) are suitable for diagnosing active tuberculosis, and for monitoring the efficacy of chemotherapy on TB patients.

METHODS

In this study, a total of 371 active TB patients without treatment were selected and categorized into S+/C+group (n=143), S-/C+group (n=106) or S-/C- group (n=122). A series of serum samples were collected from 82 active TB patients who had undergone anti-TB chemotherapy for 0-6 months at one month interval. Humoral responses (IgG, IgM and IgA) were determined for the novel Mycobacterium tuberculosis polyprotein using indirect ELISA methods in all of serum samples.

RESULTS

For S+/C+, S-/C+and S-/C- active tuberculosis patients before anti-TB chemotherapy, the sensitivities of tests based on IgG were 65.7%, 46.2% and 52.5% respectively; the sensitivities based on IgM were 21.7%, 24.5% and 18.9%; and the sensitivities based on IgA were 25.2%, 17.9% and 23.8%. By combination of three isotypes, for all active tuberculosis patients, the test sensitivity increased to 70.4% with the specificity being 91.5%. After anti-TB chemotherapy, there were no significant differences between groups with different courses of anti-TB chemotherapy.

CONCLUSIONS

The novel Mycobacterium tuberculosis polyprotein 38 F-64 F represents potential antigen suitable for measuring IgG, IgM and IgA antibodies. However, the serodiagnostic test based on the 38 F-64 F polyprotein appears unsuitable for monitoring the efficacy of chemotherapy.

Prime-boost with Mycobacterium smegmatis recombinant vaccine improves protection in mice infected with Mycobacterium tuberculosis

The development of a new vaccine as a substitute for Bacillus Calmette-Guerin or to improve its efficacy is one of the many World Health Organization goals to control tuberculosis. Mycobacterial vectors have been used successfully in the development of vaccines against tuberculosis. To enhance the potential utility of Mycobacterium smegmatis as a vaccine, it was transformed with a recombinant plasmid containing the partial sequences of the genes Ag85c, MPT51, and HspX (CMX) from M. tuberculosis. The newly generated recombinant strain mc(2)-CMX was tested in a murine model of infection. The recombinant vaccine induced specific IgG1 or IgG2a responses to CMX. CD4(+) and CD8(+) T cells from the lungs and spleen responded ex vivo to CMX, producing IFN-γ, IL17, TNF-α, and IL2. The vaccine thus induced a significant immune response in mice. Mice vaccinated with mc(2)-CMX and challenged with M. tuberculosis showed better protection than mice immunized with wild-type M. smegmatis or BCG. To increase the safety and immunogenicity of the CMX antigens, we used a recombinant strain of M. smegmatis, IKE (immune killing evasion), to express CMX. The recombinant vaccine IKE-CMX induced a better protective response than mc(2)-CMX. The data presented here suggest that the expression of CMX antigens improves the immune response and the protection induced in mice when M. smegmatis is used as vaccine against tuberculosis.

Sex bias in infectious disease epidemiology: patterns and processes

BACKGROUND

Infectious disease incidence is often male-biased. Two main hypotheses have been proposed to explain this observation. The physiological hypothesis (PH) emphasizes differences in sex hormones and genetic architecture, while the behavioral hypothesis (BH) stresses gender-related differences in exposure. Surprisingly, the population-level predictions of these hypotheses are yet to be thoroughly tested in humans.

METHODS AND FINDINGS

For ten major pathogens, we tested PH and BH predictions about incidence and exposure-prevalence patterns. Compulsory-notification records (Brazil, 2006-2009) were used to estimate age-stratified ♂:♀ incidence rate ratios for the general population and across selected sociological contrasts. Exposure-prevalence odds ratios were derived from 82 published surveys. We estimated summary effect-size measures using random-effects models; our analyses encompass ∼0.5 million cases of disease or exposure. We found that, after puberty, disease incidence is male-biased in cutaneous and visceral leishmaniasis, schistosomiasis, pulmonary tuberculosis, leptospirosis, meningococcal meningitis, and hepatitis A. Severe dengue is female-biased, and no clear pattern is evident for typhoid fever. In leprosy, milder tuberculoid forms are female-biased, whereas more severe lepromatous forms are male-biased. For most diseases, male bias emerges also during infancy, when behavior is unbiased but sex steroid levels transiently rise. Behavioral factors likely modulate male-female differences in some diseases (the leishmaniases, tuberculosis, leptospirosis, or schistosomiasis) and age classes; however, average exposure-prevalence is significantly sex-biased only for Schistosoma and Leptospira.

CONCLUSIONS

Our results closely match some key PH predictions and contradict some crucial BH predictions, suggesting that gender-specific behavior plays an overall secondary role in generating sex bias. Physiological differences, including the crosstalk between sex hormones and immune effectors, thus emerge as the main candidate drivers of gender differences in infectious disease susceptibility.

Diagnostic potential of 16 kDa (HspX, α-crystalline) antigen for serodiagnosis of tuberculosis

BACKGROUND & OBJECTIVES

Tuberculosis (TB) is a public health problem worldwide. Rapid and accurate diagnosis of tuberculosis is crucial to facilitate early treatment of infectious cases and to reduce its spread. The present study was aimed to evaluation of 16 kDa antigen as a serodiagnostic tool in pulmonary and extra-pulmonary tuberculosis patients in an effort to improve diagnostic algorithm for tuberculosis.

METHODS

In this study, 200 serum samples were collected from smear positive and culture confirmed pulmonary tuberculosis patients, 30 tubercular pleural effusions and 21 tubercular meningitis (TBM) patients. Serum samples from 36 healthy, age matched controls (hospital staff), along with 60 patients with non-tubercular respiratory diseases were also collected and evaluated. Humoral response (both IgG and IgA) was looked for 16 kDa antigen using indirect ELISA.

RESULTS

Sensitivity of detection in various categories of pulmonary TB patients ranged between 73.8 and 81.2 per cent. While in the extra-pulmonary TB samples the sensitivity was 42.8 per cent (TBM) and 63.3 per cent (tubercular pleural effusion). The test specificity in both the groups was high (94.7%). All of the non-disease controls were negative. Among non-tubercular disease controls, five patients gave a positive humoral response against 16 kDa.

INTERPRETATION & CONCLUSIONS

Serodiagnostic tests for TB have always had drawbacks of suboptimal sensitivity and specificity. The antigen used in this study gave encouraging results in pulmonary TB only, while in extra-pulmonary TB (tubercular meningitis and tubercular pleural effusion), this has shown a limited role in terms of sensitivity. Further work is required to validate its role in serodiagnosis of TB especially extra-pulmonary TB.

Pesquisa de IgA contra o antígeno recombinante HspX de Mycobacterium tuberculosis no diagnóstico de tuberculose pleural

OBJETIVO: Avaliar a acurácia da dosagem de IgA contra o antígeno recombinante HspX no líquido pleural e no soro de pacientes com derrame pleural para o diagnóstico de tuberculose pleural. MÉTODOS: Estudo transversal de teste diagnóstico. Amostras de líquido pleural e de soro de pacientes com derrame pleural e suspeita de tuberculose pleural foram avaliadas para a determinação da densidade óptica de IgA contra HspX utilizando ELISA indireto. RESULTADOS: Foram avaliadas amostras de líquido pleural e de soro de 132 pacientes: 97 com tuberculose pleural (grupo de estudo) e 35 com derrame pleural por outras causas (grupo controle). A dosagem de IgA em líquido pleural foi capaz de discriminar os pacientes com tuberculose pleural dos controles. A sensibilidade do teste em líquido pleural e em soro foi, respectivamente, de 69% e 30%, enquanto a especificidade foi de 83% e 84%, respectivamente. CONCLUSÕES: Os dados sugerem o potencial da utilização deste teste no diagnóstico de tuberculose pleural. Estudos com amostras maiores e em diferentes cenários epidemiológicos são necessários