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Human cytomegalovirus (HCMV) has been closely associated with the human race across evolutionary time. HCMV co-infection is nearly universal in human immunodeficiency virus-1 (HIV-1)-infected individuals and remains an important cofactor in HIV-1 disease progression even in the era of effective antiretroviral treatment. HCMV infection has been shown to have a broad and potent influence on the human immune system and has been linked with the discovery and characterization of adaptive natural killer (NK) cells. Distinct NK-cell subsets, predominately expressing the activating receptor NKG2C and the marker of terminal differentiation CD57, expand in response to HCMV. These NK-cell populations engaged in the long-lasting interaction with HCMV, in addition to characteristic but variable expression of surface receptors, exhibit reduced expression of signaling proteins and transcription factors expressed by canonical NK cells. Broad epigenetic modifications drive the emergence and persistence of HCMV-adapted NK cells that have distinct functional characteristics. NKG2C NK-cell expansions have been observed in HIV-1 infected patients and other acute and chronic viral infections being systematically associated with HCMV seropositivity. The latter is potentially an important confounding variable in studies focused on the cellular NK-cell receptor repertoire and functional capacity. Here, focusing on HIV-1 infection we review the evidence in favor of \"adaptive\" changes likely induced by HCMV co-infection in NK-cell subsets. We highlight a number of key questions and how insights into the adaptive behavior of NK cells will inform new strategies exploiting their unique properties in the fight against HIV-1.

There is an urgent need to understand the nature of immune responses against SARS-CoV-2, to inform risk-mitigation strategies for people living with HIV (PLWH). Here we show that the majority of PLWH with ART suppressed HIV viral load, mount a detectable adaptive immune response to SARS-CoV-2. Humoral and SARS-CoV-2-specific T cell responses are comparable between HIV-positive and negative subjects and persist 5-7 months following predominately mild COVID-19 disease. T cell responses against Spike, Membrane and Nucleoprotein are the most prominent, with SARS-CoV-2-specific CD4 T cells outnumbering CD8 T cells. We further show that the overall magnitude of SARS-CoV-2-specific T cell responses relates to the size of the naive CD4 T cell pool and the CD4:CD8 ratio in PLWH. These findings suggest that inadequate immune reconstitution on ART, could hinder immune responses to SARS-CoV-2 with implications for the individual management and vaccine effectiveness in PLWH. Understanding the pathology and immunological response to SARS CoV2 infection in specific patient groups is essential for informing the scientific and clinical handling of infections within these patient populations. Here the authors characterise the adaptive immune response to SARS-CoV2 infection in people living with HIV.

A preprint by Tarke et al. suggests a neglible impact of SARS-CoV-2 variant mutations on T cell reactivity in convalescent individuals and mRNA vaccine recipients.

A cure for HIV-1 remains unattainable as only one case has been reported, a decade ago 1 , 2 . The individual—who is known as the ‘Berlin patient’—underwent two allogeneic haematopoietic stem-cell transplantation (HSCT) procedures using a donor with a homozygous mutation in the HIV coreceptor CCR5 (CCR5Δ32/Δ32) to treat his acute myeloid leukaemia. Total body irradiation was given with each HSCT. Notably, it is unclear which treatment or patient parameters contributed to this case of long-term HIV remission. Here we show that HIV-1 remission may be possible with a less aggressive and toxic approach. An adult infected with HIV-1 underwent allogeneic HSCT for Hodgkin’s lymphoma using cells from a CCR5Δ32/Δ32 donor. He experienced mild gut graft-versus-host disease. Antiretroviral therapy was interrupted 16 months after transplantation. HIV-1 remission has been maintained over a further 18 months. Plasma HIV-1 RNA has been undetectable at less than one copy per millilitre along with undetectable HIV-1 DNA in peripheral CD4 T lymphocytes. Quantitative viral outgrowth assays from peripheral CD4 T lymphocytes show no reactivatable virus using a total of 24 million resting CD4 T cells. CCR5-tropic, but not CXCR4-tropic, viruses were identified in HIV-1 DNA from CD4 T cells of the patient before the transplant. CD4 T cells isolated from peripheral blood after transplantation did not express CCR5 and were susceptible only to CXCR4-tropic virus ex vivo. HIV-1 Gag-specific CD4 and CD8 T cell responses were lost after transplantation, whereas cytomegalovirus-specific responses were detectable. Similarly, HIV-1-specific antibodies and avidities fell to levels comparable to those in the Berlin patient following transplantation. Although at 18 months after the interruption of treatment it is premature to conclude that this patient has been cured, these data suggest that a single allogeneic HSCT with homozygous CCR5Δ32 donor cells may be sufficient to achieve HIV-1 remission with reduced intensity conditioning and no irradiation, and the findings provide further support for the development of HIV-1 remission strategies based on preventing CCR5 expression. An adult infected with HIV-1 who underwent allogeneic haematopoietic stem-cell transplantation for Hodgkin’s lymphoma using cells from a CCR5Δ32/Δ32 donor achieved full remission of HIV-1 for 18 months after transplantation and 16 months after cessation of antiretroviral therapy.

The S-type lectin galectin-9 binds to the negative regulatory molecule Tim-3 on T cells and induces their apoptotic deletion or functional inactivation. We investigated whether galectin-9/Tim-3 interactions contribute to the deletion and exhaustion of the antiviral T cell response in chronic hepatitis B virus infection (CHB). We found Tim-3 to be expressed on a higher percentage of CD4 and CD8 T cells from patients with CHB than healthy controls (p<0.0001) and to be enriched on activated T cells and those infiltrating the HBV-infected liver. Direct ex vivo examination of virus-specific CD8 T cells binding HLA-A2/peptide multimers revealed that Tim-3 was more highly upregulated on HBV-specific CD8 T cells than CMV-specific CD8 T cells or the global CD8 T cell population in patients with CHB (p<0.001) or than on HBV-specific CD8 after resolution of infection. T cells expressing Tim-3 had an impaired ability to produce IFN-γ and TNF-α upon recognition of HBV-peptides and were susceptible to galectin-9-triggered cell death in vitro. Galectin-9 was detectable at increased concentrations in the sera of patients with active CHB-related liver inflammation (p = 0.02) and was strongly expressed by Kupffer cells within the liver sinusoidal network. Tim-3 blockade resulted in enhanced expansion of HBV-specific CD8 T cells able to produce cytokines and mediate cytotoxicity in vitro. Blocking PD-1 in combination with Tim-3 enhanced the number of patients from whom functional antiviral responses could be recovered and/or the strength of responses, indicating that these co-inhibitory molecules play a non-redundant role in driving T cell exhaustion in CHB. Patients taking antivirals able to potently suppress HBV viraemia continued to express Tim-3 on their T cells and respond to Tim-3 blockade. In summary, both Tim-3 and galectin-9 are increased in CHB and may contribute to the inhibition and deletion of T cells as they infiltrate the HBV-infected liver.

Dimitra Peppa,1–3 Aljawharah Alrubayyi,1,4 Sanjay Bhagani1,5 1Division of Infection and Immunity, University College London, London, UK; 2Mortimer Market Centre, Department of HIV, CNWL NHS Trust, London, UK; 3The Ian Charleson Day Centre, Royal Free London NHS Foundation Trust, London, UK; 4Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; 5Department of HIV Medicine, Royal Free Hospital NHS Foundation Trust, London, UKCorrespondence: Dimitra Peppa, Division of Infection and Immunity, University College London, London, UK, Email d.peppa@ucl.ac.uk

CD8 T cell exhaustion is a hallmark of HIV-1 infection, characterized by phenotypic and functional CD8 T cell abnormalities that persist despite years of effective antiretroviral treatment (ART). More recently, the importance of cellular metabolism in shaping T cell antiviral function has emerged as a crucial aspect of immunotherapeutics aimed at re-invigorating exhausted CD8 T cells but remains under-investigated in HIV-1 infection. To gain a better insight into this process and identify new targets for effective CD8 T cell restoration we examined the metabolic profile of exhausted CD8 T cells in HIV-1 infection. We show that relative to HIV-1 elite controllers (EC) and HIV-1 seronegative donors, CD8 T cells from HIV-1 viraemic individuals are skewed toward a PD-1 hi EOMES hi T-bet low TIGIT + phenotype that is maintained during ART. This exhausted signature is enriched in HIV-specific CD8 T cells, compared to CMV-specific CD8 T cell populations, and further delineated by higher expression of the glucose transporter, Glut-1, impaired mitochondrial function and biogenesis, reflecting underlying metabolic defects. A notable improvement in antiviral HIV-specific CD8 T cell function was elicited via mitochondrial antioxidant treatment in combination with pharmacological modulation of mitochondrial dynamics and IL-15 treatment. These findings identify mitochondria as promising targets for combined reconstitution therapies in HIV-1 infection.

Natural killer (NK) cells are innate lymphocytes that can rapidly mount a response to their targets by employing diverse mechanisms. Due to their functional attributes, NK cells have been implicated in anti-viral and anti-tumour immune responses. Although traditionally known to mount non-specific, rapid immune responses, in recent years, the notion of memory NK cells with adaptive features has gained more recognition. Memory NK cells emerge in response to different stimuli, such as viral antigens and specific cytokine combinations. They form distinct populations, accompanied by transcriptional, epigenetic and metabolic reprogramming, resulting in unique phenotypic and functional attributes. Several clinical trials are testing the efficacy of memory NK cells due to their enhanced functionality, bioenergetic profile and persistence in vivo. The therapeutic potential of NK cells is being harnessed in viral infections, with wider applications in the cancer field. In this review, we summarise the current state of research on the generation of memory NK cells, along with their clinical applications in viral infection and cancer.

BackgroundChronic hepatitis B virus (HBV) infection disproportionately affects people living with HIV, who are often excluded from functional cure studies.ObjectiveThis study investigates CD8+ T cell profiles in HBV mono-infection versus HBV/HIV co-infection, examining the impact of long-term therapy on virus-specific responses to inform therapeutic strategies for immune restoration.DesignWe analysed CD8+ T cell responses in 61 participants (HBV n=20, HBV/HIV n=20, HIV n=21), on suppressive antiviral therapy, assessing transcriptomic and proteomic profiles, focusing on exhaustion markers alongside virus-specific functional capabilities.ResultsTranscriptomic analysis revealed distinct signatures in co-infection, with upregulation of TCR signalling genes, inhibitory pathways and progenitor-exhausted markers (XCL2, TCF7, PDCD1, IL7R). This profile scored highly for a precursor exhausted (Tpex) CD8+ T cell signature, reflecting stemness that maintains plasticity despite chronic antigen exposure. Proteomic analysis confirmed higher frequencies of Tpex (TCF-1+CD127+PD-1+) CD8+ T cells in co-infection, while HBV mono-infection showed predominance of terminally exhausted ToxhighTCF-1-CD127- cells. Tpex enrichment extended to HBV-specific populations corresponding with more robust, polyfunctional HBV-specific responses in co-infection against surface and core antigens. HBV-specific CD8 T cells maintained enhanced proliferative capacity and checkpoint responsiveness to anti-PDL1 blockade compared with HBV mono-infection. While co-infection was characterised by lower HBsAg levels and longer treatment duration, these factors alone did not account for the distinct immunological profiles.ConclusionsPeople with well-controlled HBV/HIV co-infection maintain robust CD8+ T cell responses with preserved stem-like properties supporting antiviral function. These results challenge assumptions about additive immune dysfunction in dual chronic infections and highlight the need for tailored immune-modulatory therapies.

Human cytomegalovirus (HCMV) co-infection is highly prevalent within HIV-1 cohorts and is an important cofactor in driving ongoing immune activation, even during effective antiretroviral treatment. HCMV infection has recently been associated with expansion of adaptive-like natural killer (NK) cells, which harbor epigenetic alterations that impact on their cellular function and phenotype. The influence of HCMV co-infection on the considerable heterogeneity among NK cells and their functional responses to different stimuli was assessed in a cohort of HIV-1-infected individuals sampled during different stages of infection, compared with healthy subjects stratified according to HCMV serostatus. Our data demonstrate a reshaping of the NK cell pool in HIV-1 infection of HCMV-seropositive individuals, with an accentuated peripheral transition of CD56dim NK cells toward a mature CD57+ CD85j+ NKG2C+ NKG2A- phenotype. Lack of PLZF further distinguishes adaptive NK cells from other NK cells expressing CD57 or NKG2C. PLZF- NK cells from HIV-infected individuals had high expression of CD2, were Siglec-7 negative and exhibited downregulation of key signaling molecules, SYK and FcεRI-γ, overwhelmingly displaying features of adaptive NK cells that correlated with HCMV serum Ab levels. Notably this adaptive-like signature was detected during early HIV-1 infection and persisted during treatment. Adaptive-like NK cell subsets in HIV-1-infected individuals displayed enhanced IFN-γ production following Fc receptor triggering compared with their conventional NK cell counterparts, and their ability to produce TNF-α and degranulate was preserved. Together, these data suggest that HMCV infection/reactivation, a hallmark of HIV-1 infection, plays a role in driving a relative expansion of NK cells with adaptive features during HIV-1 infection. The identification of selective NK subsets with retained effector activity in HIV-1-infected subjects raises the possibility of developing therapeutic strategies that exploit specific NK subpopulations to achieve better HIV-1 control.