The viruses HIV-1, Epstein-Barr virus (EBV), cytomegalovirus (CMV) and hepatitis C virus (HCV) are characterized by the establishment of lifelong infection in the human host, where their replication is thought to be tightly controlled by virus-specific CD8+ T cells. Here we present detailed studies of the differentiation phenotype of these cells, which can be separated into three distinct subsets based on expression of the costimulatory receptors CD28 and CD27. Whereas CD8+ T cells specific for HIV, EBV and HCV exhibit similar characteristics during primary infection, there are significant enrichments at different stages of cellular differentiation in the chronic phase of persistent infection according to the viral specificity, which suggests that distinct memory T-cell populations are established in different virus infections. These findings challenge the current definitions of memory and effector subsets in humans, and suggest that ascribing effector and memory functions to subsets with different differentiation phenotypes is no longer appropriate.

The use of peptide–human histocompatibility leukocyte antigen (HLA) class I tetrameric complexes to identify antigen-specific CD8+ T cells has provided a major development in our understanding of their role in controlling viral infections. However, questions remain about the exact function of these cells, particularly in HIV infection. Virus-specific cytotoxic T lymphocytes exert much of their activity by secreting soluble factors such as cytokines and chemokines. We describe here a method that combines the use of tetramers and intracellular staining to examine the functional heterogeneity of antigen-specific CD8+ T cells ex vivo. After stimulation by specific peptide antigen, secretion of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, macrophage inflammatory protein (MIP)-1β, and perforin is analyzed by FACS® within the tetramer-positive population in peripheral blood. Using this method, we have assessed the functional phenotype of HIV-specific CD8+ T cells compared with cytomegalovirus (CMV)-specific CD8+ T cells in HIV chronic infection. We show that the majority of circulating CD8+ T cells specific for CMV and HIV antigens are functionally active with regards to the secretion of antiviral cytokines in response to antigen, although a subset of tetramer-staining cells was identified that secretes IFN-γ and MIP-1β but not TNF-α. However, a striking finding is that HIV-specific CD8+ T cells express significantly lower levels of perforin than CMV-specific CD8+ T cells. This lack of perforin is linked with persistent CD27 expression on HIV-specific cells, suggesting impaired maturation, and specific lysis ex vivo is lower for HIV-specific compared with CMV-specific cells from the same donor. Thus, HIV-specific CD8+ T cells are impaired in cytolytic activity.

The cytotoxic potential of CD8+ T cells and NK cells plays a crucial role in the immune response to pathogens. Although in vitro studies have reported that CD4+ T cells are also able to mediate perforin-mediated killing, the in vivo existence and relevance of cytotoxic CD4+ T cells have been the subject of debate. Here we show that a population of CD4+ perforin+ T cells is present in the circulation at low numbers in healthy donors and is markedly expanded in donors with chronic viral infections, in particular HIV infection, at all stages of the disease, including early primary infection. Ex vivo analysis shows that these cells have cytotoxic potential mediated through the release of perforin. In comparison with more classical CD4+ T cells, this subset displays a distinct surface phenotype and functional profile most consistent with end-stage differentiated T cells and include Ag experienced CD4+ T cells. The existence of CD4+ cytotoxic T cells in vivo at relatively high levels in chronic viral infection suggests a role in the immune response.

Progress in the fight against the HIV/AIDS epidemic is hindered by our failure to elucidate the precise reasons for the onset of immunodeficiency in HIV-1 infection. Increasing evidence suggests that elevated immune activation is associated with poor outcome in HIV-1 pathogenesis. However, the basis of this association remains unclear. Through ex vivo analysis of virus-specific CD8+ T-cells and the use of an in vitro model of naïve CD8+ T-cell priming, we show that the activation level and the differentiation state of T-cells are closely related. Acute HIV-1 infection induces massive activation of CD8+ T-cells, affecting many cell populations, not only those specific for HIV-1, which results in further differentiation of these cells. HIV disease progression correlates with increased proportions of highly differentiated CD8+ T-cells, which exhibit characteristics of replicative senescence and probably indicate a decline in T-cell competence of the infected person. The differentiation of CD8+ and CD4+ T-cells towards a state of replicative senescence is a natural process. It can be driven by excessive levels of immune stimulation. This may be part of the mechanism through which HIV-1-mediated immune activation exhausts the capacity of the immune system.

Background Data on vaccine immunogenicity against SARS-CoV-2 are needed for the 40 million people globally living with HIV who might have less functional immunity and more associated comorbidities than the general population. We aimed to explore safety and immunogenicity of the ChAdOx1 nCoV-19 (AZD1222) vaccine in people with HIV. Methods In this single-arm open-label vaccination substudy within the protocol of the larger phase 2/3 trial COV002, adults aged 18–55 years with HIV were enrolled at two HIV clinics in London, UK. Eligible participants were required to be on antiretroviral therapy (ART), with undetectable plasma HIV viral loads (<50 copies per mL), and CD4 counts of more than 350 cells per μL. A prime-boost regimen of ChAdOx1 nCoV-19, with two doses was given 4–6 weeks apart. The primary outcomes for this substudy were safety and reactogenicity of the vaccine, as determined by serious adverse events and solicited local and systemic reactions. Humoral responses were measured by anti-spike IgG ELISA and antibody-mediated live virus neutralisation. Cell-mediated immune responses were measured by ex-vivo IFN-γ enzyme-linked immunospot assay (ELISpot) and T-cell proliferation. All outcomes were compared with an HIV-uninfected group from the main COV002 study within the same age group and dosing strategy and are reported until day 56 after prime vaccination. Outcomes were analysed in all participants who received both doses and with available samples. The COV002 study is registered with ClinicalTrials.gov , NCT04400838 , and is ongoing. Findings Between Nov 5 and Nov 24, 2020, 54 participants with HIV (all male, median age 42·5 years [IQR 37·2–49·8]) were enrolled and received two doses of ChAdOx1 nCoV-19. Median CD4 count at enrolment was 694·0 cells per μL (IQR 573·5–859·5). No serious adverse events occurred. Local and systemic reactions occurring during the first 7 days after prime vaccination included pain at the injection site (26 [49%] of 53 participants with available data), fatigue (25 [47%]), headache (25 [47%]), malaise (18 [34%]), chills (12 [23%]), muscle ache (19 [36%]), joint pain (five [9%]), and nausea (four [8%]), the frequencies of which were similar to the HIV-negative participants. Anti-spike IgG responses by ELISA peaked at day 42 (median 1440 ELISA units [EUs; IQR 704–2728]; n=50) and were sustained until day 56 (median 941 EUs [531–1445]; n=49). We found no correlation between the magnitude of the anti-spike IgG response at day 56 and CD4 cell count (p=0·93) or age (p=0·48). ELISpot and T-cell proliferative responses peaked at day 14 and 28 after prime dose and were sustained to day 56. Compared with participants without HIV, we found no difference in magnitude or persistence of SARS-CoV-2 spike-specific humoral or cellular responses (p>0·05 for all analyses). Interpretation In this study of people with HIV, ChAdOx1 nCoV-19 was ...

HIV immunity is likely CD4 T cell dependent. HIV-specific CD4 T cell proliferative responses are reported to correlate inversely with virus load and directly with specific CD8 responses. However, the phenotype and cytokine profile of specific CD4 T cells that correlate with disease is unknown. We compared the number/function of Gag p24-specific CD4 T cells in 17 HIV-infected long-term nonprogressors (LTNPs) infected for a median of 14.6 years with those of 16 slow progressors (SPs), also HIV infected for a median of 14 years but whose CD4 count had declined to &lt;500 cells/μl. Compared with SPs, LTNPs had higher numbers of specific CD4s that were double positive for IFN-γ and IL-2 as well as CD28 and IL-2. However, CD4 T cells that produced IL-2 alone (IL-2+IFN-γ−) or IFN-γ alone (IFN-γ+IL-2−) did not differ between LTNPs and SPs. The decrease in p24-specific CD28+IL-2+ cells with a concomitant increase of p24-specific CD28−IL-2+ cells occurred before those specific for a non-HIV Ag, CMV. p24-specific CD28−IL-2+ cells were evident in LTNPs and SPs, whereas the CMV-specific CD28−IL-2+ response was confined to SPs. The difference between LTNPs and SPs in the Gag p24 IFN-γ+IL-2+ response was maintained when responses to total Gag (p17 plus p24) were measured. The percentage and absolute number of Gag-specific IFN-γ+IL-2+ but not of IFN-γ+IL-2− CD4s correlated inversely with virus load. The Gag-specific IFN-γ+IL-2+ CD4 response also correlated positively with the percentage of Gag-specific IFN-γ+ CD8 T cells in these subjects. Accumulation of specific CD28−IL-2+ helpers and loss of IFN-γ+IL-2+ CD4 T cells may compromise specific CD8 responses and, in turn, immunity to HIV.

Patients with IV > 400 copies/ml are three times more likely to experience sustained viral rebound and to have an impaired CD4 cell rise relative to those who maintain undetectable VL. This supports the adoption of a more pro-active approach to treatment intensification and the need for caution with structured treatment interruptions.

The outcome of human immunodeficiency virus type 1 (HIV-1) infection is related to the set-point plasma virus load (pVL) that emerges after primary HIV-1 infection (PHI). This set-point pVL generally remains stable but eventually increases with progression to disease. However, the events leading to loss of viremic control are poorly understood. Here, we describe an individual who presented with symptomatic PHI and subsequently progressed rapidly, after an initial period of 1 year during which viral replication was well controlled. Escalation of viral replication in this atypical case was preceded by the emergence of escape variants in many epitopes targeted by dominant CD8 + T cell responses and a marked decrease in HIV-1-specific CD4 + and CD8 + T cell frequencies. There were no changes in viral tropism, replication kinetics, or neutralizing antibody titers. These findings demonstrate the temporal relationship between viral escape from CD8 + T cell activity, decrease in HIV-1-specific T cell frequencies, and loss of control of viral replication.Substantial evidence indicates that the adaptive immune system plays a major role in containing viral replication during HIV-1 infection [1,2]. In particular, HIV-1-specific CD8 + T cell responses are thought to mediate the decrease in the initial viremia during primary HIV-1 infection (PHI) [3,4]. After PHI, a setpoint plasma virus load (pVL) emerges that, in general, remains relatively stable throughout the chronic asymptomatic phase of infection. The magnitude of this setpoint pVL, which is likely determined by early interactions between the virus and the immune system, is inversely related to the rate of progression to AIDS [5]. However, the factors that are responsible for the maintenance of the established set-point pVL are less well defined, and it is not clear which events eventually lead to loss of control of viremia. Identification of such events requires longitudinal and comprehensive analysis of adaptive immune responses and viral evolution in patients with untreated HIV-1 infection.Here, we studied the natural course of HIV-1 infection over a period of 2 years in an individual who presented with symptomatic PHI. Initially, viral replication