HIV-1 preferentially infects M. tuberculosis-specific CD4+ T cells due to their increased production of IL-2.

Programmed death-1 (PD-1) is a critical mediator of virus-specific CD8 ؉ T-cell exhaustion. Here, we examined the expression of PD-1 on simian immunodeficiency virus (SIV)-specific CD8 ؉ T cells and its possible involvement in regulation of cytokine production, proliferation, and survival of these cells. The majority of SIV-specific CD8 ؉ T cells expressed a PD-1 high phenotype, independent of their differentiation status, in all tissues tested. PD-1 expression gradually declined on CD8 ؉ T cells specific for SIV-derived epitopes that had undergone mutational escape, indicating that antigen-specific TCR stimulation is the primary determinant of PD-1 expression. SIV-specific PD-1 high CD8 ؉ T cells produced IFN-␥, TNF-␣, and IL-2 under cognate peptide stimulation. While CD8 ؉ T cells that proliferated in response to antigen had a PD-1 high phenotype, it was determined that there was a reduced proliferative capacity of PD-1 high compared with PD-1 low SIVspecific CD8 ؉ T cells. PD-1 high SIV-specific CD8 ؉ T cells were highly susceptible to IntroductionVirus-specific CD8 ϩ T cells are the predominant effectors through which the immune system controls viral infections. 1,2 While several lines of evidence indicate that human immunodeficiency virus (HIV)-specific CD8 ϩ T cells are involved in the control of HIV replication, 3-10 several reports have focused on intrinsic defects in these cells to explain their failure to clear the virus, thereby leading to progression to acquired immunodeficiency syndrome (AIDS) in all infected individuals. [11][12][13][14] Similarly, simian immunodeficiency virus (SIV)-specific CD8 ϩ T cells contribute substantially to the partial control of viremia in rhesus macaques; depletion of CD8 ϩ T cells results in increased viremia in SIV-infected animals, 15,16 while viral escape at targeted epitopes accelerates disease progression and death in vaccinated animals. 4 Furthermore, in acute SIV infection, cytotoxic SIV-specific CD8 ϩ T cells appear concurrently with the waning of early viremia. 17 As in human infection with HIV, functional defects in SIV-specific CD8 ϩ T cells have been reported, potentially explaining why virtually all SIV-infected rhesus macaques progress to simian AIDS and death despite a readily measurable CD8 ϩ T-cell response. [17][18][19][20] Therefore, understanding factors that regulate the function(s) of SIV-and HIV-specific CD8 ϩ T cells is critical in the fight against AIDS.Chronic viral infection with ongoing antigenic stimulation often results in exhaustion of virus-specific CD8 ϩ T cells. 21,22 Chronically stimulated virus-specific CD8 ϩ T cells express only low levels of receptors for IL-7 and IL-15 23 and lose the ability to maintain homeostatic proliferation. In addition, they lose the ability to produce key cytokines that are critical for the maintenance of CD8 ϩ T-cell memory. 24 In humans, the function and phenotype of chronically stimulated CD8 ϩ T cells differ among viral infections. HIV-specific CD8 ϩ T cells are less polyfunctional and more sensitive ...

The importance of HLA class I-restricted CD8 T-cell responses in the control of human immunodeficiency virus (HIV) infection is generally accepted. While several studies have shown an association of certain HLA class I alleles with slower disease progression, it is not fully established whether this effect is mediated by HIV-specific CD8 T-cell responses restricted by these alleles. In order to study the influence of the HLA class I alleles on the HIV-specific CD8 T-cell response and on viral control, we have assessed HIV-specific epitope recognition, plasma viral load, and expression of HLA class I alleles in a cohort of HIV-seropositive bar workers. Possession of the HLA class I alleles B5801, B8101, and B0702 was associated with a low median viral load and simultaneously with a broader median recognition of Gag epitopes compared to all other HLA alleles (twofold increase) (P ‫؍‬ 0.0035). We further found an inverse linear relationship between the number of Gag epitopes recognized and the plasma viral load (R ‫؍‬ ؊0.36; P ‫؍‬ 0.0016). Particularly, recognition of multiple epitopes within two regions of Gag (amino acids [aa] 1 to 75 and aa 248 to 500) was associated with the maintenance of a low steady-state viremia, even years after acute infection.

Background The acid-fast bacillus Mycobacterium tuberculosis (MTB) is often the first manifestation of AIDS in HIV infected patients. This study was conducted to better understand the mechanism underlying MTB-specific pathogenicity early in HIV infection. Methods MTB-specific T Helper 1 (TH1) cells were studied in HIV negative (n=114) and chronically HIV infected (n=68) Tanzanian subjects usinEarly Secreted Antigenic Target 6 (ESAT6) protein or Tuberculin (PPD) by Interferon gamma (IFNγ) ELISPOT and intracellular cytokine staining. In a longitudinal study the effect of acute HIV infection on MTB-specific TH1 cells was determined by polychromatic flow cytometric analysis in 5 subjects with latent MTB infection, who became infected with HIV. Results In Tuberculosis (TB) asymptomatic subjects, chronic HIV infection was associated with a decreased frequency of responders with detectable MTB-specific TH1 cells (p-value = 0.0003) that was not observed in subjects with active TB. Acute HIV infection induced a rapid depletion of MTB-specific TH1 cells in 4 subjects who remained TB asymptomatic, but were stable in subjects who remained HIV negative (p<0.01). Conclusions Together these data suggest a mechanism of rapid MTB-specific TH1 cell depletion that may contribute to the early onset of TB in latently MTB infected individuals who become HIV infected.

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Recent studies have revealed the critical role of programmed death-1 (PD-1) in exhaustion of HIV- and SIV-specific CD8+ T cells. In this study, we show that high expression of PD-1 correlates with increased ex vivo spontaneous and CD95/Fas-induced apoptosis, particularly in the “effector-memory” CD8+ T cell population from HIV+ donors. High expression of PD-1 was linked to a proapoptotic phenotype characterized by low expression of Bcl-2 and IL7-Rα, high expression of CD95/Fas and high mitochondrial mass. Expression of PD-1 and CD57 was differentially associated with the maturation status of CD8+ T cells in HIV infection. CD57 was linked to higher apoptosis resistance, with cells expressing a PD-1LCD57H phenotype exhibiting lower levels of cell death. The majority of HIV-specific CD8+ T cells were found to express a PD-1HCD57L or PD-1HCD57H phenotype. No correlation was found between PD-1 expression and ex vivo polyfunctionality of either HIV- or CMV-specific CD8+ T cells. Contrary to CD57, high expression of PD-1 was characterized by translocation of PD-1 into the area of CD95/Fas-capping, an early necessary step of CD95/Fas-induced apoptosis. Thus, our data further support the role of PD-1 as a preapoptotic factor for CD8+ T cells in HIV infection.

Background: The analysis of phenotypic characteristics on Mycobacterium tuberculosis (MTB)-specific T cells is a promising approach for the diagnosis of active tuberculosis (aTB) and for monitoring treatment success. We therefore studied phenotypic changes on MTB-specific CD4 T cells upon anti-tuberculosis treatment initiation in relation to the treatment response as determined by sputum culture.Methods: Peripheral blood mononuclear cells from subjects with latent MTB infection (n = 16) and aTB (n = 39) at baseline, weeks 9, 12, and 26 (end of treatment) were analyzed after intracellular interferon gamma staining and overnight stimulation with tuberculin. Liquid sputum cultures were performed weekly until week 12 and during 4 visits until week 26.Results: T cell activation marker expression on MTB-specific CD4 T cells differed significantly between subjects with aTB and latent MTB infection with no overlap for the frequencies of CD38pos and Ki67pos cells (both p < 0.0001). At 9 weeks after anti-TB treatment initiation the frequencies of activation marker (CD38, HLA-DR, Ki67) positive MTB-specific, but not total CD4 T cells, were significantly reduced (p < 0.0001). Treatment induced phenotypic changes from baseline until week 9 and until week 12 differed substantially between individual aTB patients and correlated with an individual's time to stable sputum culture conversion for expression of CD38 and HLA-DR (both p < 0.05). In contrast, the frequencies of maturation marker CD27 positive MTB-specific CD4 T cells remained largely unchanged until week 26 and significantly differed between subjects with treated TB disease and latent MTB infection (p = 0.0003).Discussion: Phenotypic changes of MTB-specific T cells are potential surrogate markers for tuberculosis treatment efficacy and can help to discriminate between aTB (profile: CD38pos, CD27low), treated TB (CD38neg, CD27low), and latent MTB infection (CD38neg, CD27high).

Summary Background We used the RNActive® technology platform (CureVac N.V., Tübingen, Germany) to prepare CVnCoV, a COVID-19 vaccine containing sequence-optimized mRNA coding for a stabilized form of SARS-CoV‑2 spike (S) protein encapsulated in lipid nanoparticles (LNP). Methods This is an interim analysis of a dosage escalation phase 1 study in healthy 18–60-year-old volunteers in Hannover, Munich and Tübingen, Germany, and Ghent, Belgium. After giving 2 intramuscular doses of CVnCoV or placebo 28 days apart we assessed solicited local and systemic adverse events (AE) for 7 days and unsolicited AEs for 28 days after each vaccination. Immunogenicity was measured as enzyme-linked immunosorbent assay (ELISA) IgG antibodies to SARS-CoV‑2 S‑protein and receptor binding domain (RBD), and SARS-CoV‑2 neutralizing titers (MN50). Results In 245 volunteers who received 2 CVnCoV vaccinations (2 μg, n = 47, 4 μg, n = 48, 6 μg, n = 46, 8 μg, n = 44, 12 μg, n = 28) or placebo (n = 32) there were no vaccine-related serious AEs. Dosage-dependent increases in frequency and severity of solicited systemic AEs, and to a lesser extent local AEs, were mainly mild or moderate and transient in duration. Dosage-dependent increases in IgG antibodies to S‑protein and RBD and MN50 were evident in all groups 2 weeks after the second dose when 100% (23/23) seroconverted to S‑protein or RBD, and 83% (19/23) seroconverted for MN50 in the 12 μg group. Responses to 12 μg were comparable to those observed in convalescent sera from known COVID-19 patients. Conclusion In this study 2 CVnCoV doses were safe, with acceptable reactogenicity and 12 μg dosages elicited levels of immune responses that overlapped those observed in convalescent sera.