Joy Baseke

Response to M. tuberculosis selected RD1 peptides in Ugandan HIV-infected patients with smear positive pulmonary tuberculosis: a pilot study

BackgroundTuberculosis (TB) is the most frequent co-infection in HIV-infected individuals still presenting diagnostic difficulties particularly in developing countries. Recently an assay based on IFN-gamma response to M. tuberculosis RD1 peptides selected by computational analysis was developed whose presence is detected during active TB disease. Objective of this study was to investigate the response to selected RD1 peptides in HIV-1-infected subjects with or without active TB in a country endemic for TB and to evaluate the change of this response over time.Methods30 HIV-infected individuals were prospectively enrolled, 20 with active TB and 10 without. Among those with TB, 12 were followed over time. IFN-gamma response to selected RD1 peptides was evaluated by enzyme-linked immunospot (ELISPOT) assay. As control, response to RD1 proteins was included. Results were correlated with immune, microbiological and virological data.ResultsAmong patients with active TB, 2/20 were excluded from the analysis, one due to cell artifacts and the other to unresponsiveness to M. tuberculosis antigens. Among those analyzable, response to selected RD1 peptides evaluated as spot-forming cells was significantly higher in subjects with active TB compared to those without (p = 0.02). Among the 12 TB patients studied over time a significant decrease (p =< 0.007) of IFN-gamma response was found at completion of therapy when all the sputum cultures for M. tuberculosis were negative. A ratio of RD1 peptides ELISPOT counts over CD4+ T-cell counts greater than 0.21 yielded 100% sensitivity and 80% specificity for active TB. Conversely, response to RD1 intact proteins was not statistically different between subjects with or without TB at the time of recruitment; however a ratio of RD1 proteins ELISPOT counts over CD4+ T-cell counts greater than 0.22 yielded 89% sensitivity and 70% specificity for active TB.ConclusionIn this pilot study the response to selected RD1 peptides is associated with TB disease in HIV-infected individuals in a high TB endemic country. This response decreases after successful therapy. The potential of the novel approach of relating ELISPOT spot-forming cell number and CD4+ T-cell count may improve the possibility of diagnosing active TB and deserves further evaluation.

CD8 + T cells provide an immunologic signature of tuberculosis in young children

RATIONALE The immunologic events surrounding primary Mycobacterium tuberculosis infection and development of tuberculosis remain controversial. Young children who develop tuberculosis do so quickly after first exposure, thus permitting study of immune response to primary infection and disease. We hypothesized that M. tuberculosis-specific CD8(+) T cells are generated in response to high bacillary loads occurring during tuberculosis. OBJECTIVES To determine if M. tuberculosis-specific T cells are generated among healthy children exposed to M. tuberculosis and children with tuberculosis. METHODS Enzyme-linked immunosorbent spot assays were used to measure IFN-γ production in response to M. tuberculosis-specific proteins ESAT-6/CFP-10 by peripheral blood mononuclear cells and CD8(+) T cells isolated from Ugandan children hospitalized with tuberculosis (n = 96) or healthy tuberculosis contacts (n = 62). MEASUREMENTS AND MAIN RESULTS The proportion of positive CD8(+) T-cell assays and magnitude of CD8(+) T-cell responses were significantly greater among young (<5 yr) tuberculosis cases compared with young contacts (P = 0.02, Fisher exact test, P = 0.01, Wilcoxon rank-sum, respectively). M. tuberculosis-specific T-cell responses measured in peripheral blood mononuclear cells were equivalent between groups. CONCLUSIONS Among young children, M. tuberculosis-specific CD8(+) T cells develop in response to high bacillary loads, as occurs during tuberculosis, and are unlikely to be found after M. tuberculosis exposure. T-cell responses measured in peripheral blood mononuclear cells are generated after M. tuberculosis exposure alone, and thus cannot distinguish exposure from disease. In young children, IFN-γ-producing M. tuberculosis-specific CD8(+) T cells provide an immunologic signature of primary M. tuberculosis infection resulting in disease.

Innate and Adaptive Immune Responses during Acute M. tuberculosis Infection in Adult Household Contacts in Kampala, Uganda

Contacts of active pulmonary tuberculosis (TB) patients are at risk for Mycobacterium tuberculosis (MTB) infection. Because most infections are controlled, studies during MTB infection provide insight into protective immunity. We compared immune responses of adult household contacts that did and did not convert the tuberculin skin test (TST). Innate and adaptive immune responses were measured by whole blood assay. Responses of TST converters (TSTC) were compared with persistently TST negative contacts (PTST-) and contacts who were TST+ at baseline (TST+). TLR-2, TLR-4, and IFN-γR responses to IFN-γ did not differ between the groups, nor did γδ T cell responses. T cell responses to MTB antigens differed markedly among TSTC, PTST-, and TST+ contacts. Thus, no differences in innate responses were found among the three household contact groups. However, adaptive T cell responses to MTB antigens did differ before and during MTB infection among PTST-, TSTC, and TST+ contacts.

Persistent Replication of Human Immunodeficiency Virus Type 1 despite Treatment of Pulmonary Tuberculosis in Dually Infected Subjects

ABSTRACT Tuberculosis (TB) is the most common life-threatening infection in human immunodeficiency virus (HIV)-infected persons and frequently occurs before the onset of severe immunodeficiency. Development of TB is associated with increased HIV type 1 (HIV-1) viral load, a fall in CD4 lymphocyte counts, and increased mortality. The aim of this study was to examine how treatment of pulmonary TB affected HIV-1 activity in HIV-1/TB-coinfected subjects with CD4 cell counts of >100 cells/μl. HIV-1/TB-coinfected subjects were recruited in Kampala, Uganda, and were monitored over time. Based upon a significant (0.5 log10 copies/ml) decrease in viral load by the end of treatment, two patient groups could be distinguished. Responders (n = 17) had more rapid resolution of anemia and pulmonary lesions on chest radiography during TB treatment. This group had a significant increase in viral load to levels not different from those at baseline 6 months after completion of TB treatment. HIV-1 viral load in nonresponders (n = 10) with TB treatment increased and at the 6 month follow-up was significantly higher than that at the time of diagnosis of TB. Compared to baseline levels, serum markers of macrophage activation including soluble CD14 decreased significantly by the end of TB treatment in responders but not in nonresponders. These data further define the impact of pulmonary TB on HIV-1 disease. HIV-1 replication during dual HIV-1/TB infection is not amenable to virologic control by treatment of TB alone. Concurrent institution of highly active antiretroviral treatment needs to be evaluated in patients dually infected with pulmonary TB and HIV-1.

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.

Comprehensive definition of human immunodominant CD8 antigens in tuberculosis

Despite widespread use of the Bacillus Calmette-Guerin vaccine, tuberculosis, caused by infection with Mycobacterium tuberculosis, remains a leading cause of morbidity and mortality worldwide. As CD8+ T cells are critical to tuberculosis host defense and a phase 2b vaccine trial of modified vaccinia Ankara expressing Ag85a that failed to demonstrate efficacy, also failed to induce a CD8+ T cell response, an effective tuberculosis vaccine may need to induce CD8+ T cells. However, little is known about CD8, as compared to CD4, antigens in tuberculosis. Herein, we report the results of the first ever HLA allele independent genome-wide CD8 antigen discovery program. Using CD8+ T cells derived from humans with latent tuberculosis infection or tuberculosis and an interferon-γ ELISPOT assay, we screened a synthetic peptide library representing 10% of the Mycobacterium tuberculosis proteome, selected to be enriched for Mycobacterium tuberculosis antigens. We defined a set of immunodominant CD8 antigens including part or all of 74 Mycobacterium tuberculosis proteins, only 16 of which are previously known CD8 antigens. Immunogenicity was associated with the degree of expression of mRNA and protein. Immunodominant antigens were enriched in cell wall proteins with preferential recognition of Esx protein family members, and within proteins comprising the Mycobacterium tuberculosis secretome. A validation study of immunodominant antigens demonstrated that these antigens were strongly recognized in Mycobacterium tuberculosis-infected individuals from a tuberculosis endemic region in Africa. The tuberculosis vaccine field will likely benefit from this greatly increased known repertoire of CD8 immunodominant antigens and definition of properties of Mycobacterium tuberculosis proteins important for CD8 antigenicity.Tuberculosis: Defining the proteins that drive immune responsesSpecific bacterial proteins have been found that drive effective immune responses to tuberculosis, with use in making more effective vaccines. Immunity to tuberculosis (TB) is facilitated by two types of white blood cell; however, most research has focused on one: the CD4+ T cell. Deborah A. Lewinsohn and David Lewinsohn, of the Oregon Health & Science University, USA, and collaborators lay out the essential functions of the oft-neglected CD8+ T cell, and undertook a broad approach to catalogue and define the bacterial proteins that activate the CD8+ T cell response. The team found that TB-infected humans reacted strongly to their protein library, and described several characteristics of CD8+ T cell ‘antigens’ (activators of immune cells) that will likely prove highly useful in the design of more protective TB vaccines.

Prevalence of hepatitis B and C and relationship to liver damage in HIV infected patients attending Joint Clinical Research Centre Clinic (JCRC), Kampala, Uganda.

BACKGROUND Hepatitis B and C viruses cause death due to liver disease worldwide among Human Immunodeficiency Virus (HIV) positive individuals. Hepatitis B (HBV) and HIV have similar routes of transmission primarily; sexual, intravenous injections and prenatal while hepatitis C (HCV) is transmitted mainly through blood transfusion. Human immunodeficiency virus increases the pathological effect of hepatitis viruses and potentiates re-activation of latent hepatitis infections as a result of reduced immunity. The increase in use of antiretroviral (ARVs) drugs has led to longer period for patient survival and apparent increase in liver disease among HIV positive individuals. OBJECTIVE This study aimed at determining the prevalence of HBV, HCV, their co-infection with HIV and their effect on liver cell function. METHOD This was a cross sectional study conducted at the Joint Clinical Research Centre (JCRC) among HIV positive individuals attending the clinic. Patients were enrolled after obtaining a signed informed consent or assent for children below 17 years. Serum samples were collected for detection of Hepatitis B surface antigen (HBsAg), HCV specific antibodies and alanine aminotransferase (ALT) liver enzyme. RESULTS Of the 89 patients enrolled, 20 (22.5%) had at least one hepatitis virus, 15 tested positive for HBsAg (16.9%) and 5 for HCV (5.6%), one had both viruses. Hepatitis B was more prevalent among women (13 out of 57, 22.8%) than men, (2 out of 32, 6.2%), while HCV was higher among men (4 out of 32, 12.5%) than women (1 out of 57, 1.8%). Seven of 89 patients (7.9%) had elevated ALT, indicative of liver cell injury. Of these with liver cell injury, one individual tested positive for HBsAg and another one individual tested positive for HCV specific antibodies. CONCLUSION The prevalence of HBV is high in HIV positive individuals with more women commonly infected. The Prevalence of HCV is lower than that of HBV with more men commonly infected. Co-infection of Hepatitis B and C viruses was uncommon. This study reveals a high prevalence of liver cell injury among HIV positive individuals although the injury due to HBV or HCV infection was lower than that which has been documented. From this study, the high prevalence of HBV and HCV among HIV positive individuals point to a need for screening of HIV positive individuals for the hepatitis viruses.

Immune activation at sites of HIV/TB Co-Infection contributes to the pathogenesis of HIV-1 Disease

Systemic immune activation is critical to the pathogenesis of HIV-1 disease, and is accentuated in HIV/TB co-infected patients. The contribution of immune activation at sites of HIV/TB co-infection to viral activity, CD4 T cell count, and productive HIV-1 infection remain unclear. In this study, we measured markers of immune activation both in pleural fluid and plasma, and in T cells in pleural fluid mononuclear cell (PFMC) and peripheral blood mononuclear cell (PBMC) in HIV/TB co-infected subjects. The relationship between soluble and T cell activation markers with viral load in pleural fluid and blood CD4 T cell count were assessed. The T cell phenotype and activation status of HIV-1 p24 + T cells in PFMC and PBMC from HIV/TB patients were determined. We found that T cell and macrophage-specific and non-specific soluble markers of immune activation, sCD27, sCD163, IL1Ra, and sCD14, were higher in pleural fluid as compared to plasma from HIV/TB co-infected subjects, and higher as compared to pleural fluid from TB mono-infected subjects. Intestinal fatty acid-binding protein, a marker of intestinal tract damage, in plasma from HIV/TB co-infected patients was not different than that in HIV+ subjects. Expression of HLADR and CD38 double positive (HLADR/CD38) on CD4 T cells, and CD69+ on CD8 T cells correlated with pleural fluid viral load, and inversely with blood CD4 T cell count. Higher expression of HLADR/CD38 and CCR5 on CD4 T cells, and HLADR/CD38 and CD69 on CD8 T cells in PFMC were limited to effector memory populations. HIV-1 p24+ CD8 negative (includes CD4 + and double negative T cells) effector memory T cells in PFMC had higher expression of HLADR/CD38, Ki67, and CCR5 compared to HIV-1 p24- CD8 negative PFMC. Cumulatively, these data indicate that sites of HIV/TB co-infection are the source of intense immune activation.

Productive HIV-1 infection is enriched in CD4(-)CD8(-) double negative (DN) T cells at pleural sites of dual infection with HIV and Mycobacterium tuberculosis.

A higher human immunodeficiency virus 1 (HIV-1) viral load at pleural sites infected with Mycobacterium tuberculosis (MTB) than in peripheral blood has been documented. However, the cellular source of productive HIV infection in HIV-1/MTB-coinfected pleural fluid mononuclear cells (PFMCs) remains unclear. In this study, we observed significant quantities of HIV-1 p24+ lymphocytes in PFMCs, but not in peripheral blood mononuclear cells (PBMCs). HIV-1 p24+ lymphocytes were mostly enriched in DN T cells. Intracellular CD4 expression was detectable in HIV-1 p24+ DN T cells. HIV-1 p24+ DN T cells showed lower surface expression of human leukocyte antigen (HLA)-ABC and tetherin than did HIV-1 p24+ CD4 T cells. Upon in vitro infection of PFMC CD4 T cells from TB mono-infected subjects, Nef- and/or Vpu-deleted HIV mutants showed lower generation of HIV-1 p24+ DN T cells than the wild-type virus. These data indicate that productively HIV-1-infected DN T cells, generated through down-modulation of surface CD4, likely by HIV-1 Nef and Vpu, are the predominant source of HIV-1 at pleural sites of HIV/MTB coinfection.

T-reg are the Predominant CD4 + T-Cell Subset Productively Infected with HIV-1 at Sites of Dual HIV/TB Infection

Background: Regulatory T-cells (T-reg) are expanded during active tuberculosis (TB) regardless of HIV-1-infection, particularly at sites of M. tuberculosis infection. In HIV-1 disease, T-reg are targeted by HIV-1 infection. However, whether they contribute to promotion of HIV-1 infection at sites of HIV/TB is unknown. Methods: Pleural fluid mononuclear cells (PFMC) from HIV/TB patients with pleural TB were characterized by immunostaining and FACS analysis for surface markers CD4, CD127, CCR5, CXCR4 and intracellular expression of Foxp3, HIVp24, IFN-g and Bcl-2. T-reg purified by immunomagnetic bead separation were assessed for HIV-1 strong stop (SS) DNA expression by real-time PCR. Results: High numbers of T-reg (defined as CD4 + Foxp3 + or CD4 + Foxp3 + CD127 - ), that were HIV-1-infected were found in PFMC. T-reg displayed higher expression of the cellular activation marker, HLA-DR (p<0.001), and HIV-1 co-receptors (CCR5 and CXCR4) (p<0.05 for both) as compared to non-T-reg. Purified T-reg exhibited higher HIV-1 infection, as measured by HIV-1 SS DNA, when compared to whole PFMC, and as compared to PFMC T-reg from an HIV-infected subject with mesothelioma. HIV- infected CD4 + Foxp3 + T-reg were significantly higher in Bcl-2 expression as compared to CD4 + Foxp3 - cells (p<0.001). Further, HIV-1-infected T-reg showed significantly higher Bcl-2 reactivity than un-infected T-reg (p<0.001). A small fraction of HIV-1-infected T-reg were also IFN-g+ .