Dipendra K. Mitra

Miliary tuberculosis: new insights into an old disease

Miliary tuberculosis is a potentially lethal form of tuberculosis resulting from massive lymphohaematogeneous dissemination of Mycobacterium tuberculosis bacilli. The emergence of the HIV/AIDS pandemic and widespread use of immunosuppressive drugs has changed the epidemiology of miliary tuberculosis. Impaired cell-mediated immunity underlies the diseases development. Clinical manifestations are non-specific and typical chest radiographic findings may not be seen until late in the course of the disease. Atypical presentations--eg, cryptic miliary tuberculosis and acute respiratory distress syndrome--often delay the diagnosis. Several laboratory abnormalities with prognostic and therapeutic implications have been described, including pulmonary function and gas exchange impairment. Isolation of M tuberculosis from sputum, body fluids, or biopsy specimens, application of molecular methods such as PCR, and histopathological examination of tissue biopsy specimens are useful for the confirmation of diagnosis. Although response to first-line antituberculosis drugs is good, evidence regarding optimum duration of treatment is lacking and the role of adjunctive corticosteroid treatment is unclear.

N-acetylcysteine replenishes glutathione in HIV infection.

Glutathione (GSH) deficiency is common in HIV‐infected individuals and is associated with impaired T cell function and impaired survival. N‐acetylcysteine (NAC) is used to replenish GSH that has been depleted by acetaminophen overdose. Studies here test oral administration of NAC for safe and effective GSH replenishment in HIV infection.

HIV does not replicate in naive CD4 T cells stimulated with CD3/CD28.

In this report, we demonstrate that the T cell tropic strain of HIV, LAI, does not replicate in naive CD4 T cells stimulated by cross-linking CD3 and CD28. In contrast, LAI replicates well in memory CD4 T cells stimulated in the same way. Unlike this physiologically relevant stimulation, PHA stimulates productive LAI replication in both naive and memory T cells. These studies were conducted with highly purified (FACS-isolated) subsets of CD4 T cells identified by expression of both CD45RA and CD62L. Remixing of purified T cells showed that naive T cells do not suppress LAI replication in memory T cells and that memory T cells do not restore LAI expression in naive T cells. The suppression of productive LAI replication in naive T cells is not due to differential expression of viral coreceptors, nor is it due to inhibition of activation of the important HIV transcription factors, nuclear factor-kappaB and activator protein-1. The inherent resistance of naive T cells to productive HIV infection, coupled with their proliferative advantage as demonstrated here, provides a sound basis for proposed clinical therapies using ex vivo expansion and reinfusion of CD4 T cells from HIV-infected adults.

FoxP3+ Regulatory T Cells Suppress Effector T-Cell Function at Pathologic Site in Miliary Tuberculosis

RATIONALE The inadequacy of effector T-cell response in containment of tubercle bacilli is believed to result in the development of disseminated forms of tuberculosis (TB), such as miliary tuberculosis (MTB). Regulatory T cells (Treg) plausibly play a critical role in the immunopathogenesis of disseminated TB by suppression of effector immune response against Mycobacterium tuberculosis at the pathologic site(s). To understand the role of Treg cells in disseminated tuberculosis, we studied the frequency and function of Treg cells derived from the local disease site specimens (LDSS) of patients with TB pleural effusion and MTB as clinical models of contained and disseminated forms of disease, respectively. OBJECTIVES To (1) enumerate the frequency of Treg cells in bronchoalveolar lavage (BAL) fluid of patients with MTB and compare with that of peripheral blood, (2) study the role of Treg cells in suppression of local T-cell response, and (3) study the selective recruitment of Treg cells at the local disease site(s). METHODS Flow cytometry, reverse transcriptase polymerase chain reaction, and 3-(4,5-dimethylthythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)-based cell proliferation assay. MEASUREMENTS AND MAIN RESULTS Frequency of Treg cells (CD4(+)CD25(+)FoxP3(+)) was significantly higher in LDSS in MTB along with higher levels of FoxP3 mRNA. Importantly, FoxP3(+) Treg cells obtained from the BAL of patients with MTB predominantly produced IL-10 and could suppress the autologous T-cell proliferation in response to M. tuberculosis antigen. CONCLUSIONS Our results highlight the importance of Treg cells in suppression of effector immune response and their influence on bacillary dissemination, disease manifestation, and severity.

Inhibiting the Programmed Death 1 Pathway Rescues Mycobacterium tuberculosis–Specific Interferon γ–Producing T Cells From Apoptosis in Patients With Pulmonary Tuberculosis

BACKGROUND Overexpression of programmed death 1 (PD-1) receptor is thought to inhibit the effector T-cell response in human tuberculosis. However, the precise mechanism of such inhibition remains unclear. The present study addresses the role of PD-1 in dampening host T-cell function among patients with pulmonary tuberculosis. METHODS Expression of PD-1 and its ligands (PD-L1/L2) on T cells, B cells, and monocytes was evaluated by flow cytometry (FACS). In vitro stimulation of peripheral blood mononuclear cells in the presence of Mycobacterium tuberculosis antigens was performed with and without blocking PD-1, and intracellular cytokine production was measured by FACS. RESULTS We showed higher frequencies of T cells, monocytes, and B cells expressing PD-1 and its ligand(s) among patients with pulmonary tuberculosis. Infections with live M. tuberculosis upregulated PD-L1 expression on monocytes. In vitro PD-1 blocking rescued M. tuberculosis-specific interferon γ (IFN-γ)-producing T cells from undergoing apoptosis. The number of PD-1-expressing T cells decreased significantly during therapy and inversely correlated with IFN-γ-dominant T-cell response against M. tuberculosis. CONCLUSIONS Manipulation of PD-1 signaling may restore the host T-cell response and thus may have therapeutic potential. PD-1 also may serve as a biomarker to monitor host immunity among patients with tuberculosis during therapy and vaccine studies.

Foxp3+ regulatory T cells among tuberculosis patients: impact on prognosis and restoration of antigen specific IFN-γ producing T cells.

CD4+CD25+Foxp3+ Regulatory T cells (Treg) and programmed death-1 (PD-1) molecules have emerged as pivotal players in immune suppression of chronic diseases. However, their impact on the disease severity, therapeutic response and restoration of immune response in human tuberculosis remains unclear. Here, we describe the possible role of Treg cells, their M. tuberculosis driven expansion and contribution of PD-1 pathway to the suppressive function of Treg cells among pulmonary tuberculosis (PTB) patients. Multicolor flow cytometry, cell culture, cells sorting and ELISA were employed to execute the study. Our results showed significant increase in frequency of antigen-reactive Treg cells, which gradually declined during successful therapy and paralleled with decline of M. tuberculosis–specific IL-10 along with elevation of IFN-γ production, and raising the IFN-γ/IL-4 ratio. Interestingly, persistence of Treg cells tightly correlated with MDR tuberculosis. Also, we show that blocking PD-1/PD-L1 pathway abrogates Treg-mediated suppression, suggesting that the PD-1/PD-L1 pathway is required for Treg-mediated suppression of the antigen-specific T cells. Treg cells possibly play a role in dampening the effector immune response and abrogating PD-1 pathway on Treg cells significantly rescued protective T cell response, suggesting its importance in immune restoration among tuberculosis patients.

Clinical significance of sperm DNA damage threshold value in the assessment of male infertility

Sperm DNA integrity is a prerequisite for normal spermatozoal function. The aim of the study was to evaluate the role of sperm chromatin damage, its cut-off level and its effect on sperm parameters in men with idiopathic infertility by analyzing 100 idiopathic infertile men and 50 fertile controls. Semen samples were analyzed as per WHO 1999 guidelines and sperm chromatin structure assay (SCSA) was applied to measure DNA fragmentation index (DFI) in sperm. The mean DFI of infertile men (35.75) was significantly (P < .0001) higher as compared to controls (26.22). The threshold level of 30.28% was obtained as cut-off value to discriminate infertile men from fertile controls. Sperm count, forward motility, and normal morphology found to be negatively associated with DFI in overall study subjects. Infertile men with severe oligozoospermia had higher mean DFI (40.01 ± 11.31) than infertile men with oligozoospermia (35.11 ± 10.05) and normal sperm count (33.99 ± 9.96). Moreover 64% of infertile men have DFI > 30 against 6% of fertile controls (P < .0001). Higher sperm DNA fragmentation may be the underlying cause for poor semen quality in idiopathic infertile men and the threshold value of 30.28% is a clear discriminator to distinguish infertile men from fertile men of Indian population. Thus, DFI is a good prognostic marker as cases with higher sperm DFI may have poor success rate even after assisted conception and may experience recurrent pregnancy loss (RPL) and should be counseled accordingly.

Regulatory T cells suppress T cell activation at the pathologic site of human visceral leishmaniasis.

Suppression of T cell response is thought to be involved in the pathogenesis of visceral leishmaniasis (VL). Regulatory T cell (Treg) mediated immune-suppression is reported in animal models of Leishmania infection. However, their precise role among human patients still requires pathologic validation. The present study is aimed at understanding the frequency dynamics and function of Treg cells in the blood and bone marrow (BM) of VL patients. The study included 42 parasitologically confirmed patients, 17 healthy contact and 9 normal bone marrow specimens (NBM). We show i) the selective accumulation of Treg cells at one of the disease inflicted site(s), the BM, ii) their in vitro expansion in response to LD antigen and iii) persistence after successful chemotherapy. Results indicate that the Treg cells isolated from BM produces IL-10 and may inhibit T cell activation in IL-10 dependent manner. Moreover, we observed significantly higher levels of IL-10 among drug unresponsive patients, suggesting their critical role in suppression of immunity among VL patients. Our results suggest that IL-10 plays an important role in suppression of host immunity in human VL and possibly determines the efficacy of chemotherapy.

Polarized helper T cells in tubercular pleural effusion: phenotypic identity and selective recruitment.

Containment of Mycobacterium tuberculosis critically depends on orchestrated generation of Th1 cells and their selective recruitment at the pathologic sites. Understanding the mechanism involved in this process is important for defining better intervention strategies. We investigated the surface phenotype of Th1 cells and the role of chemotactic factors in their selective recruitment in tuberculosis pleural effusion and tuberculin site. Memory T cells obtained from the pleural fluid expressed a battery of homing receptors such as CD11a, CCR5 and CXCR3. Similar expression profile was noted on T cells infiltrating the tuberculin site. Expression of their respective ligands such as ICAM‐1, RANTES, MIP1‐α, Mig and IP‐10 were detected at pathologic sites. In vitro assay of T cell adherence to activated human umbilical vein endothelial cells (HUVEC) expressing chemotactic ligands suggests an important role of these homing molecules in their selective trafficking. Here, we demonstrate a hierarchy of CXCR3 in effector cell adhesion to HUVEC in vitro, although CD11a and CCR5 were also observed to mediate cell adhesion in an additive fashion. Findings of the present study provide mechanistic insights into the critical events of T cell trafficking in tuberculosis and may help designing better therapeutic modalities.

Effect of cyclosporine on fertility in male rats

Abstract The effect of cyclosporine (CsA) on fertility has assumed greater importance with the increasing numbers of pediatric transplantations being performed all over the world. Conflicting reports on the effects of CsA on sex hormones are available. This experimental animal study was designed to examine the effect of CsA on testicular weight, sperm counts, seminiferous tubular diameter (STD), testicular morphology, DNA flowcytometry, sex hormone levels, and fertility in male rats. Those rats who received CsA (20 mg/kg per day) showed significant reductions in testicular weight (P < 0.05), sperm count (P < 0.01), Johnsen score (P < 0.05), STD (P < 0.01), serum testosterone levels (P < 0.05), haploid cell population (P < 0.001) in the testis, and fertility (P < 0.001) compared to those receiving CsA 10 mg/kg per day and control rats. These findings will have an important bearing for children receiving cyclosporine for long periods to guide the physician in optimally adjusting long-term treatment.