Expression of granzyme B by cytotoxic T lymphocytes in the lymph nodes of HIV-infected patients

Autophagy-enhancing ATG16L1 polymorphism is associated with improved clinical outcome and T-cell immunity in chronic HIV-1 infection

Chronic HIV-1 infection is characterized by T-cell dysregulation that is partly restored by antiretroviral therapy. Autophagy is a critical regulator of T-cell function. Here, we demonstrate a protective role for autophagy in HIV-1 disease pathogenesis. Targeted analysis of genetic variation in core autophagy gene ATG16L1 reveals the previously unidentified rs6861 polymorphism, which correlates functionally with enhanced autophagy and clinically with improved survival of untreated HIV-1-infected individuals. T-cells carrying ATG16L1 rs6861(TT) genotype display improved antiviral immunity, evidenced by increased proliferation, revamped immune responsiveness, and suppressed exhaustion/immunosenescence features. In-depth flow-cytometric and transcriptional profiling reveal T-helper-cell-signatures unique to rs6861(TT) individuals with enriched regulation of pro-inflammatory networks and skewing towards immunoregulatory phenotype. Therapeutic enhancement of autophagy recapitulates the rs6861(TT)-associated T-cell traits in non-carriers. These data underscore the in vivo relevance of autophagy for longer-lasting T-cell-mediated HIV-1 control, with implications towards development of host-directed antivirals targeting autophagy to restore immune function in chronic HIV-1 infection.

Lesion-Specific Immune Response in Granulomas of Patients with Pulmonary Tuberculosis: A Pilot Study

The formation and maintenance of granulomas is central to the host response to Mycobacterium tuberculosis (Mtb) infection. It is widely accepted that the lungs of patients with tuberculosis (TB) usually contain multiple infection foci, and that the granulomas evolve and differentiate independently, resulting in considerable heterogeneity. Although gene expression profiles of human blood cells have been proposed as biomarkers of Mtb infection and/or active disease, the immune profiles of discrete lesion types has not been studied extensively. Using histology, immunopathology and genome-wide transcriptome analysis, we explored the immunological profile of human lung TB granulomas. We show that although the different granulomas share core similarities in their immunological/inflammatory characteristics, they also exhibit significant divergence. Despite similar numbers of CD68⁺ macrophages in the different lesions, the extent of immune reactivity, as determined by the density of CD3⁺ T cells in the macrophage rich areas, and the extent of fibrosis, shows considerable variation. Both quantitative and qualitative differences among significantly differentially expressed genes (SDEG) were noted in each of the lesion types studied. Further, network/pathway analysis of SDEG revealed differential regulation of inflammatory response, immune cell trafficking, and cell mediated immune response in the different lesions. Our data highlight the formidable challenges facing ongoing efforts to identify peripheral blood biomarkers due to the diversity of lesion types and complexity of local immune responses in the lung.

Impaired expression of perforin and granulysin in CD8+ T cells at the site of infection in human chronic pulmonary tuberculosis

Protective immunity in tuberculosis is dependent on the coordinated release of cytolytic effector molecules from effector T cells and the subsequent granule-associated killing of infected target cells. In this study, we investigated the expression of cytolytic (perforin and granzyme A) and antimicrobial (granulysin) molecules at the single-cell level in cryopreserved lung tissue from patients with chronic, progressive tuberculosis disease. Quantification of protein-expressing cells was performed by in situ imaging, while mRNA levels in the infected tissue were analyzed by real-time PCR. Persistent inflammation, including excessive expression of inducible nitric oxide synthase in CD68+ macrophages and significant infiltration of CD3+, CD8+ and CD4+ T cells, was evident in tuberculosis lesions in all patients. However, despite the accumulation of CD3+ T cells, perforin- and granulysin-expressing CD3+ T cells were detected at two- to threefold-lower ratios in the tuberculosis lesions than in distal lung parenchyma and uninfected control lungs, respectively. This was evident at both the protein and mRNA levels. Moreover, perforin- and granulysin-expressing CD8+ T cells were scarce in individual granulomas within the tuberculosis lesions. In contrast, significant up-regulation of granzyme A-expressing CD3+ T cells was evident in the lesions from all patients. Confocal microscopy revealed coexpression of perforin and granulysin, primarily in CD8+ T cells; however, this expression was lower in the tuberculosis lesions. These findings suggest that symptomatic, chronic tuberculosis disease is associated with insufficient up-regulation of perforin and granulysin coexpression in CD8+ T cells at the local site of infection.

The price of the CD27-CD70 costimulatory axis: you can't have it all

T cells require costimulatory signals for optimal proliferation, differentiation, and survival and thus to induce protective immune responses. Recent data, however, show that during chronic lymphocyte choriomeningitis virus (LCMV) infection, triggering of the costimulatory receptor CD27 by its ligand CD70 impedes neutralizing antibody production and leads to viral persistence. Thus, while being crucial for the induction of some adaptive effector pathways, costimulation may block the development of others. Pathogens may exploit this Achilles' heal to achieve persistence.

High levels of CD8-positive lymphocytes expressing CD45R0, granzyme B, and Ki-67 in lymph nodes of HIV-infected individuals are not associated with increased mortality

Lymph nodes constitute the major site of HIV replication and of immunological response to HIV. To study the role of cytotoxic and mitotic active CD8(+) lymphocytes in lymph nodes during HIV infection we examined 28 formalin-fixed, paraffin-embedded lymph nodes sampled from 1984 to 1986 from 21 HIV-seropositive patients and seven HIV-negative patients. Eleven of the HIV-positive patients died within 78 months of biopsy time and 10 patients were alive on July 1, 1998. Double immunohistochemical staining procedures were developed to identify CD8(+) cells expressing CD45R0, granzyme B, and Ki-67. A stereological method was used to count the different cell types in the lymph nodes. There were no significant differences in the total cell (nucleated) and CD3(+) cell concentrations between the three groups. However, there were significantly higher concentrations of CD3(+)CD8(+), CD8(+)CD45R0(+), and CD8(+)Ki-67(+) lymphocytes in the HIV patients compared with the control group. Furthermore, there was a tendency for the HIV-deceased group to have lower levels of CD8(+)granzyme B(+) and CD8(+)Ki-67(+) lymphocyte concentrations compared with the HIV-alive group. Three HIV patients, who progressed to death within 49 months of biopsy time, were among the patients with the lowest concentrations of CD8(+)granzyme B(+) and CD8(+)Ki-67(+) lymphocytes. This finding allowed us to conclude that CD8(+) lymphocytes expressing high levels of CD45R0, granzyme B, and Ki-67 in lymph nodes of HIV patients are not related to increased mortality, whereas low concentrations of CD8(+) granzyme B(+) and CD8(+)Ki-67(+) lymphocytes may be associated with poor prognosis.

HIV virions and HIV infection in vitro are unaffected by human granzymes A and B

Granzymes are a family of serine proteinases commonly found in the granules of CD8+ T cells. In HIV infection, CD8+ cells show cytotoxic and noncytotoxic antiviral activities. The latter is mediated, at least in part, by a secreted CD8+ cell antiviral factor, CAF. Because of the antiviral nature of CD8+ cells, we examined the potential anti-HIV activity of free granzymes that can be found in CD8+ cell culture fluids. Pretreatment of CD4+ T cells with granzyme A or granzyme B had no effect on their susceptibility to infection with HIV, nor did incubation of the granzymes with HIV virions alter their infectivity. Continuous culture of acutely infected CD4+ T cells with granzyme A or B showed no effect on cell viability or the replication of HIV. The findings of this study suggest that free granzymes do not control HIV infection and spread in CD4+ T cells.

The relative resistance of HIV type 1-infected chimpanzees to AIDS correlates with the maintenance of follicular architecture and the absence of infiltration by CD8+ cytotoxic T lymphocytes

Lymphoid tissues are the focus of critical events in HIV pathogenesis. Persistent and high levels of virus production, extensive trapping of virus particles in germinal centers, and progressive degenerative changes in lymph node architecture are characteristics of progressive HIV-1 infection. Infiltrates of granzyme B- and TIA-expressing CD8+ "cytotoxic" T lymphocytes (CTLs) precede involution of germinal centers in humans who develop AIDS. Similar to humans, HIV-1 infection in chimpanzees is active and persistent. However, in contrast to humans, they remain relatively resistant to AIDS. Lymph node biopsies from chimpanzees infected with HIV-1 or a related chimpanzee lentivirus were studied for the level and pattern of virus expression, changes in lymphoid architecture, CD8+ T cell infiltrates and the presence or absence of CTL markers. In stark contrast to HIV-1-infected humans, lymph nodes from infected chimpanzees had little virus deposition in germinal centers and a paucity of virus-expressing cells. Although some of the lymph nodes examined from infected animals had moderate follicular hyperplasia with infiltrating CD8+ T cells, none had evidence of follicular fragmentation. Most importantly, in marked contrast to infected humans, CD8+ T cells infiltrating the germinal center were negative for the CTL marker granzyme B. This evidence suggests that the infiltration of CD8+ CTLs into the germinal centers of lymph nodes may be a key determinant in AIDS pathogenesis.