Alteration of CD8+ T cell effector diversity during HIV-1 infection with discordant normalization in effective antiretroviral therapy

An altered cytotoxic program of CD8+ T-cells in HIV-infected patients despite HAART-induced viral suppression

Despite the suppression of viral replication induced by the highly active anti-retroviral therapy (HAART), an increased immune activation and inflammatory state persists in HIV-infected patients, contributing to lower treatment response and immune reconstitution, and development of non-AIDS conditions. The chronic activation and inflammation affect the functionality and differentiation of CD8+ T-cells, particularly reducing their cytotoxic capacity, which is critical in the control of HIV replication. Although previous studies have shown that HAART induce a partial immune reconstitution, its effect on CD8+ T-cells cytotoxic function, as well as its relationship with the inflammatory state, is yet to be defined. Here, we characterized the functional profile of polyclonal and HIV-specific CD8+ T cells, based on the expression of cell activation and differentiation markers, in individuals chronically infected with HIV, under HAART. Compared with seronegative controls, CD8+ T-cells from patients on HAART exhibited a low degranulation capacity (surface expression of CD107a), with consequent low secreted levels and high intracellular expression of granzyme B and perforin. This degranulation defect was particularly observed in those cells expressing the activation marker HLA-DR, which were further characterized as effector memory cells with high expression of CD57. The expression of CD107a, but not of granzyme B and perforin, in CD8+ T-cells from HIV-infected patients on HAART reached levels similar to those in seronegative controls when the treatment duration was higher than 25 months. In addition, the expression of CD107a was negatively correlated with the expression of exhaustion markers on CD8+ T-cells and the plasma inflammatory molecule sCD14. Thus, despite HAART-induced viral suppression, CD8+ T-cells from HIV-infected patients have an alteration in their cytotoxic program. This defect is associated with the cellular activation, differentiation and exhaustion state, as well as with the inflammation levels, and can be partially recovered with a long and continuous treatment.

Alteration of T Cell Phenotypes in HIV-Neurotuberculosis Coinfection

BACKGROUND

Neurotuberculosis is one of the commonest HIV associated opportunistic infections of the central nervous system in India. HIV-TB coinfection may lead to altered frequencies of T cells, thereby influencing the course and progression of the disease.

METHODS

We examined the frequencies of T cell subsets in HIV infected individuals with neurotuberculosis (HIV+nTB+) as compared to individuals with HIV associated systemic TB (HIV+sTB+), asymptomatic HIV (HIV+TB-), non-HIV neuro TB (HIV-nTB+), non-HIV systemic TB (HIV-sTB+), and healthy controls (HIV-TB-). Activation and senescence profiles of CD4 and CD8 T cells and memory subsets in peripheral blood mononuclear cells were studied by flow cytometry.

RESULTS

The significant observations among the T cell subsets in HIV+nTB+ were: (1) Naïve T cells: decreased CD4 T cells compared to HIV-sTB+ (P = 0.005); decreased CD8 T cells compared to HIV-nTB+ and HIV-TB- (P ≤ 0.007), (2) Memory T cells: expanded CD4 TEMRA cells compared to HIV-nTB+, HIV-sTB+, and HIV-TB- (P ≤ 0.003); expanded CD8 TEMRA cells compared to HIV-nTB+ and HIV-TB- (P ≤ 0.005), (3) Activated T cells: higher CD4 T cells compared to HIV-nTB+, HIV-sTB+, and HIV-TB- (P ≤ 0.004); higher CD8 T cells compared to HIV + TB-, HIV-nTB+, HIV-sTB+, and HIV-TB- (P ≤ 0.001), and (4) Senescent T cells: increased CD8 T cells compared to HIV-nTB+ and HIV-TB- groups (P = 0.000).

CONCLUSIONS

Increased activation compared to HIV+TB-, HIV-nTB+, HIV-sTB+, and HIV-TB- groups and increased senescence compared to HIV-nTB+ and HIV-TB- groups were observed in CD8 T cells in HIV+nTB+, suggesting that the frequencies of these T cell subsets are altered to a greater extent in these individuals. © 2018 International Clinical Cytometry Society.

Differential expression of CD96 surface molecule represents CD8⁺ T cells with dissimilar effector function during HIV-1 infection

During HIV-1 infection, immune dysregulation and aberrant lymphocyte functions are well-established characteristics. Cell surface molecules are important for immunological functions and changes in expression can affect lymphocyte effector functions, thereby contributing to pathogenesis and disease progression. In this study we have focused on CD96, a member of the IgG superfamily receptors that have generated increasing recent interest due to their adhesive and co-stimulatory functions in addition to immunoregulatory capacity. CD96 is expressed by both T and NK cells. Although the function of CD96 is not completely elucidated, it has been shown to have adhesive functions and enhance cytotoxicity. Interestingly, CD96 may also have inhibitory functions due to its immunoreceptor tyrosine-based inhibitory motif (ITIM). The clinical significance of CD96 is still comparatively limited although it has been associated with chronic Hepatitis B infection and disease progression. CD96 has not previously been studied in the context of HIV-1 infection, but due to its potential importance in immune regulation and relevance to chronic disease, we examined CD96 expression in relation to HIV-1 pathogenesis. In a cross-sectional analysis, we investigated the CD8⁺ T cell expression of CD96 in cohorts of untreated HIV-1 infected adults with high viral loads (non-controllers) and low viral loads (“elite” controllers). We demonstrated that elite controllers have significantly higher CD96 mean fluorescence intensity on CD8⁺ T cells compared to HIV-1 non-controllers and CD96 expression was positively associated with CD4⁺ T cell counts. Functional assessment showed that CD8⁺ T cells lacking CD96 expression represented a population that produced both perforin and IFN-γ following stimulation. Furthermore, CD96 expression on CD8⁺ T cells was decreased in presence of lipopolysaccharide in vitro. Overall, these findings indicate that down-regulation of CD96 is an important aspect of HIV-1 pathogenesis and differential expression is related to cell effector functions and HIV-1 disease course.