T lymphocyte inhibitory/exhaustion marker expression in chronic HIV-1 infection and the impact of TB co-infection

[摘要] ENGLISH ABSTRACT: IntroductionChronic HIV-1 infection is driven by inflammation and immune activation which ultimately induces T lymphocyte exhaustion. Co-infection with TB is problematic as the HIV-impaired immune system is unable to effectively contain the TB, and in turn the TB disease promotes further immune activation and exhaustion through additional antigenic burden.In the current two component study, a total of 101 HIV-1 infected, 25 HIV-1-TB co-infected and 52 uninfected control individuals were included from the Cape Town peri-urban region. A cross sectional investigation of expression of markers of immune activation (CD38 and HLA-DR), exhaustion/inhibition (PD-1, Tim-3, LAG-3, 2B4) and apoptosis (CD95) was investigated on both CD4+ and CD8+ T cells. Functional proliferative responsiveness of T cells was also assessed.Materials and MethodsFlow cytometry (both 4–colour and 10-colour) was used to determine expression of phenotypic markers using both fresh whole blood (pilot study) and PBMC (main study). CD4+ and CD8+ T lymphocyte populations of all study groups were stained for all the markers and evaluated for positive expression or co-expression.A functional proliferation assay (αCD3 and αCD28 stimulation) was conducted using CFSE-staining on the HIV-1+ samples. Impact of blocking Tim-3 and PD-1 pathways was evaluated.ResultsChronic HIV-1 infection was accompanied by a significant increase in CD38 (p<0.0001), CD95 (p<0.01), PD-1 (p<0.01) and Tim-3 (p<0.01) expression on CD8+ T cells (pilot study). TB co-infection led to significantly elevated expression of CD38, CD95 and Tim-3, but not PD-1 (all p<0.05). CD4+ T cells displayed decreased expression of all of these markers in the infected groups, except for Tim-3, which was consistently <5%.In the main study CD8+ T cell-associated CD38, CD95, and PD-1 displayed a similar trend, with significant higher expression in the infected groups (p<0.0001, p<0.05, and p<0.0001, respectively), In contrast to the pilot study, Tim-3 expression was consistently <10%, with no difference between the groups. The novel marker 2B4 showed high level baseline expression (median 59.2%) which was significantly increased in the HIV and HIV/TB groups (69.6% and 75.1% respectively, p=0.025). LAG-3 was poorly expressed. Co-expression ofPD-1 and 2B4 as well as CD95 and CD38 was also significantly increased (p<0.0001 for both).DiscussionIncreased immune activation and exhaustion was evident in the infected groups in both studies. PD-1 and 2B4 were both strongly expressed on CD8+ T cells and were significantly up-regulated in infected groups. PD-1 correlated positively with Tim-3 and LAG-3, and 2B4 with LAG-3, (both p<0.01) indicating that they are useful as biomarkers of exhaustion.Although significantly elevated exhaustion markers were observed in the TB co-infected setting in the pilot study, this did not reflect in the main study (except for CD95, 2B4). This suggests that immune dysfunction is mainly driven by HIV-1 infection alone. Short-term anti-TB therapy may also have had a restorative impact on the exhaustive marker expression. Differences in expression patterns using fresh whole blood vs. PBMC (especially Tim-3) warrant further investigation. Blocking Tim-3 and PD-1 expression on CD4+ and CD8+ T cells did not appear to have beneficial effects on T cell proliferation.

[发布机构] Stellenbosch University