Impact of antiretroviral and tuberculosis therapies on CD4 + and CD8 + HIV/M. tuberculosis-specific T-cell in co-infected subjects

Background: Human Immunodeficiency Virus (HIV) infection is a risk factor for tuberculosis (TB). Antiretroviral therapy (ART) changed HIV clinical management but it is still unclear how pre-existing HIV/Mycobacterium tuberculosis (Mtb)-specific CD4 + and CD8 + T-cells are restored. Aim: to evaluate the impact of ART and TB therapies on the functional and phenotypic profile of Mtb-specific antigen-response of CD4 + and CD8 + T-cells in prospectively enrolled HIV-TB co-infected patients. Methods: ART-naïve HIV-infected patients, with or without active TB or latent TB infection (LTBI), were enrolled before and after starting ART and TB therapies. Peripheral blood mononuclear cells (PBMC) were stimulated overnight with Mtb and HIV antigens (GAG). Cytokine expression and phenotype profile were evaluated by flow cytometry. Cytomegalovirus (CMV) and staphylococcal enterotoxin B (SEB) were also used. Results: The median of absolute number of CD4 + T-cells increased after ART and TB therapies in all groups analyzed, while the median of absolute number of CD8 + T-cells decreases in HIV and HIV-LTBI groups. Treatments significantly increased the frequency of Mtb-specific CD4 + T-cells in the HIV-LTBI (p = 0.015) with a rise of the central memory compartment. The magnitude of the CD4 + T-cell response to HIV-GAG significantly increased in active TB (p = 0.03), whereas the magnitude of CMV-specific CD4 + T-cell response decreased in all the groups. Similarly, the treatments increased the number of Mtb-specific CD8 + responders in both HIV-LTBI and HIV-TB groups, whereas the phenotype distribution was dependent on the antigens used and on the stage of infection/disease. Conclusions: After therapies the median of absolute number and the proportion of CD4 + T-cells increased in all groups whereas the median of absolute count and proportion of CD8 + T-cells decreased in the HIV and HIV-LTBI subjects. Interestingly, an increased frequency of CD4 + T-cell response to RD1 proteins in HIV-LTBI subjects was found. These results contribute to a better understanding of the effect of ART and TB therapies on the modulation of Mtb-specific CD4 + and CD8 + T-cells subsets

Genetic Epidemiology of Tuberculosis Susceptibility: Impact of Study Design

Several candidate gene studies have provided evidence for a role of host genetics in susceptibility to tuberculosis (TB). However, the results of these studies have been very inconsistent, even within a study population. Here, we review the design of these studies from a genetic epidemiological perspective, illustrating important differences in phenotype definition in both cases and controls, consideration of latent M. tuberculosis infection versus active TB disease, population genetic factors such as population substructure and linkage disequilibrium, polymorphism selection, and potential global differences in M. tuberculosis strain. These considerable differences between studies should be accounted for when examining the current literature. Recommendations are made for future studies to further clarify the host genetics of TB

Interferon-γ Release Assays for Diagnosing Mycobacterium tuberculosis Infection in Renal Dialysis Patients

Background and objectives: End-stage renal disease (ESRD) patients are at high risk for tuberculosis (TB). IFN-γ release assays that assess immune responses to specific TB antigens offer potential advantages over tuberculin skin testing (TST) in screening such patients for Mycobacterium tuberculosis infection. This study sought to determine whether IFN-γ release assay results are more closely associated with recent TB exposure than TST results

Implementation of point-of-care testing and prevalence of cryptococcal antigenaemia among patients with advanced HIV disease in Mumbai, India

Objectives To describe the implementation of screening for cryptococcal antigenaemia by point-of-care (POC) serum cryptococcal antigen (CrAg) lateral flow assay, measure the prevalence and factors associated with serum cryptococcal antigenaemia in the routine programmatic setting.Design Cross-sectional study.Setting Seventeen publicly funded antiretroviral therapy (ART) centres in Mumbai, India.Participants Serum CrAg screening was offered to all adolescents (>10 years of age) and adults with advanced HIV disease (AHD) (CD4 <200 cells/mm3 or with WHO clinical stage III/IV) regardless of symptoms of cryptococcal meningitis.Primary and secondary outcome measures The primary outcome was to describe the implementation of serum CrAg screening and secondary outcome was to measure the prevalence of serum cryptococcal antigenaemia and its risk factors.Results A total of 2715 patients with AHD were tested for serum CrAg by POC assay. Of these, 25 (0.9%) had a CrAg positive result. Among CrAg-positive patients, only one had symptoms. Serum CrAg positivity was 3.6% (6/169) and 1.6% (6/520) among those presenting with CD4 <100 cells/mm3 in the treatment naïve and treatment experienced group, respectively. On multivariable analysis, CD4 count <100 cells/mm3 (OR: 2.3, 95% CI 1.01 to 5.3; p=0.05) and people living with HIV who were treatment naïve (OR: 2.5, 95% CI 1.04 to 6.0; p=0.04) were significantly associated with a positive serum CrAg result. Lumbar puncture was obtained in 20/25 patients within 4 days (range: 1–4 days) of positive serum CrAg result and one person was confirmed to have meningitis. All serum CrAg-positive patients who had a negative cerebrospinal fluid CrAg were offered pre-emptive therapy.Conclusions Implementation of a POC CrAg assay was possible with existing ART centre staff. Initiation of pre-emptive therapy and management of cryptococcal antigenaemia are operationally feasible at ART centres. The Indian National AIDS Control Programme may consider reflexive CrAg screening of all AHD patients with CD4 <100 cells/mm3

Rapid Identification of the Mycobacterium tuberculosis Complex by Combining the ESAT-6/CFP-10 Immunochromatographic Assay and Smear Morphology▿

Early secretory antigen 6 (ESAT-6) and cell filtrate protein 10 (CFP-10) are two antigens secreted as a complex by the replicating Mycobacterium tuberculosis complex (MTC). Recently, an immunochromatographic assay (ICA) using a monoclonal antibody against the ESAT-6/CFP-10 complex was developed for the purpose of MTC detection. In this study, the efficacy of the assay was tested with 603 BACTEC cultures that were incubated for 3 additional days after positive signals appeared in the BACTEC MGIT 960 system. Bacterial isolates were recovered from these 603 BACTEC cultures, and 332 MTC isolates, 270 nontuberculosis mycobacterial isolates, and 1 Nocardia isolate were identified by using standard biochemical assays. The ESAT-6/CFP-10 assay detected 322 MTC cultures, resulting in a sensitivity of 97% and a specificity of 97.4%. To reduce the false-negative rate and improve the sensitivity, either serpentine cording in an acid-fast bacillus stain of the cultural smear, the ESAT-6/CFP-10 assay, or a combination of both was used for MTC detection. The sensitivity was then increased to 99.1%, and the negative predictive value increased to 98.9%, but the specificity decreased to 94.8% and the positive predictive value decreased to 95.9%. However, a combination of serpentine cording in cultural smears and the positivity of the ICA resulted in the specificity and positive predictive values of 100%. Therefore, BACTEC cultures with both serpentine cording and positivity of the ESAT-6/CFP-10 assay could be reported to contain MTC directly. The ESAT-6/CFP-10 assay may be an alternative of the Capilia assay (MPB64-ICA) as a convenient and cost-effective method for identification of MTC in culture

Mycobacterium tuberculosis specific CD8(+) T cells rapidly decline with antituberculosis treatment.

RATIONALE:Biomarkers associated with response to therapy in tuberculosis could have broad clinical utility. We postulated that the frequency of Mycobacterium tuberculosis (Mtb) specific CD8(+) T cells, by virtue of detecting intracellular infection, could be a surrogate marker of response to therapy and would decrease during effective antituberculosis treatment. OBJECTIVES:We sought to determine the relationship of Mtb specific CD4(+) T cells and CD8(+) T cells with duration of antituberculosis treatment. MATERIALS AND METHODS:We performed a prospective cohort study, enrolling between June 2008 and August 2010, of HIV-uninfected Ugandan adults (n = 50) with acid-fast bacillus smear-positive, culture confirmed pulmonary TB at the onset of antituberculosis treatment and the Mtb specific CD4(+) and CD8(+) T cell responses to ESAT-6 and CFP-10 were measured by IFN-γ ELISPOT at enrollment, week 8 and 24. RESULTS:There was a significant difference in the Mtb specific CD8(+) T response, but not the CD4(+) T cell response, over 24 weeks of antituberculosis treatment (p<0.0001), with an early difference observed at 8 weeks of therapy (p = 0.023). At 24 weeks, the estimated Mtb specific CD8(+) T cell response decreased by 58%. In contrast, there was no significant difference in the Mtb specific CD4(+) T cell during the treatment. The Mtb specific CD4(+) T cell response, but not the CD8(+) response, was negatively impacted by the body mass index. CONCLUSIONS:Our data provide evidence that the Mtb specific CD8(+) T cell response declines with antituberculosis treatment and could be a surrogate marker of response to therapy. Additional research is needed to determine if the Mtb specific CD8(+) T cell response can detect early treatment failure, relapse, or to predict disease progression