Increased frequencies of CD8+CD57+ T cells are associated with antibody neutralization breadth against HIV in viraemic controllers

Differing natural killer cell, T cell and antibody profiles in antiretroviral-naive HIV-1 viraemic controllers with and without protective HLA alleles

Previous work suggests that HIV controllers with protective human leukocyte antigen class I alleles (VC+) possess a high breadth of Gag-specific CD8+ T cell responses, while controllers without protective alleles (VC-) have a different unknown mechanism of control. We aimed to gain further insight into potential mechanisms of control in VC+ and VC-. We studied 15 VC+, 12 VC- and 4 healthy uninfected individuals (UI). CD8+ T cell responses were measured by ELISpot. Flow cytometry was performed to analyse surface markers for activation, maturation, and exhaustion on natural killer (NK) cell and T cells, as well as cytokine secretion from stimulated NK cells. We measured plasma neutralization activity against a panel of 18 Env-pseudotyped viruses using the TZM-bl neutralization assay. We found no significant differences in the magnitude and breadth of CD8+ T cell responses between VC+ and VC-. However, NK cells from VC- had higher levels of activation markers (HLA-DR and CD38) (p = 0.03), and lower cytokine expression (MIP-1β and TNF-α) (p = 0.05 and p = 0.04, respectively) than NK cells from VC+. T cells from VC- had higher levels of activation (CD38 and HLA-DR co-expression) (p = 0.05), as well as a trend towards higher expression of the terminal differentiation marker CD57 (p = 0.09) when compared to VC+. There was no difference in overall neutralization breadth between VC+ and VC- groups, although there was a trend for higher neutralization potency in the VC- group (p = 0.09). Altogether, these results suggest that VC- have a more activated NK cell profile with lower cytokine expression, and a more terminally differentiated and activated T cell profile than VC+. VC- also showed a trend of more potent neutralizing antibody responses that may enhance viral clearance. Further studies are required to understand how these NK, T cell and antibody profiles may contribute to differing mechanisms of control in VC+ and VC-.

The proportion of CD57+ cells among effector CD8+ T cells is lower in HIV controllers compared with antiretroviral therapy-treated patients

BACKGROUND

HIV infection has often been linked to faster immune ageing. We sought to determine whether or not treatment-naive spontaneous HIV-1 controllers (HICs) and ART-exposed patients differ with regard to the expression of cell senescence markers.

METHODS

Eighty-eight chronically infected HICs and ART-exposed patients (median time since infection: 15 years) with an undetectable plasma HIV RNA load (at least for the previous 2 years) were included. We used flow cytometry to measure immunosenescence markers (KLRG-1 and CD57) expression in fresh blood samples collected from patients and healthy donors.

RESULTS

For the CD8 T-cell population as a whole, the ART-exposed but not the HIC patients exhibited a much higher proportion of KLRG-1 and CD57 CD8 T cells than healthy blood donors. For the CD8 T-cell subsets, HICs had a lower proportion of CD57 effector CD8 T cells than ART patients or healthy blood donors, whereas the proportions of KLRG-1 effector were similar. A similar trend was observed for terminal effectors. No impact of age, sex or standard parameters of infection (CD4 percentage, protective HLA allele, viral blips) was observed. The difference in the proportion of CD57 cells between HICs and ART was observed more specifically in long-term infected patients (>20 years). However, whenever considering the CD57 effector memory and effector subsets, the cytotoxic granule content was greater in HICs than in ART.

CONCLUSION

The proportion of CD57 effector CD8 T cells is lower in HICs than in ART-exposed patients. This profile may be beneficial by ensuring limited senescence associated with consistent cytotoxic potential.

Deep Profiling of the CD8+ T-cell Compartment Identifies Activated Cell Subsets and Multifunctional Responses Associated With Control of Cytomegalovirus Viremia

BACKGROUND

Human cytomegalovirus (HCMV) is a common opportunistic pathogen in transplant recipients. Patterns of viremia and reactivation are influenced by the host immune response, including CD8 T cells. However, the cellular deficits or phenotypic differences that account for differential outcomes during HCMV viremia are incompletely understood.

METHODS

Peripheral blood mononuclear cells were collected from 20 transplant recipients (10 viremia controllers and 10 noncontrollers) at onset of HCMV viremia and 4 weeks postonset. We used mass cytometry to perform in-depth characterization of cell surface and intracellular CD8 T cell markers and to compare frequencies of these cells between groups.

RESULTS

Deep profiling identified 2 central memory T cell subsets at onset and 5 terminally differentiated memory T (TEMRA) cell subsets at 4 weeks that were associated with control of HCMV viremia, in addition to 6 TEMRA subsets at onset and 4 weeks associated with relapsing or remitting HCMV viremia. In general, CD8 T-cell clusters associated with poorly controlled HCMV viremia lacked markers of activation or terminal differentiation including CD38, CD69, CD25, CD57, and HLA-DR. We also measured the production of 8 HCMV-specific effector molecules (TNFα, IFNγ, interleukin 2, granzyme B, perforin, macrophage inflammatory protein 1β, interleukin 10, and CD107a) in CD8 T cells. Viremia controllers had greater diversity of HCMV-specific multifunctional responses at both time points, including significantly higher frequencies of HCMV-specific TNFαIFNγ CD8 T cells at onset. These multifunctional cells had a phenotype consistent with activated TEM/TEMRA cells.

CONCLUSIONS

Uncontrolled CMV viremia is associated with specific clusters of memory T-cell subsets and lower frequencies of HCMV-specific multifunctional CD8 T cells.

Plasma IL-5 but Not CXCL13 Correlates With Neutralization Breadth in HIV-Infected Children

Children may be the optimal target for HIV vaccine development as they generate substantially more frequent and more potent broadly HIV neutralizing antibodies (bnAbs) than adults. Development of a biomarker that correlates with neutralization breadth in this group could function as a powerful tool to facilitate the development of an HIV vaccine. Previously, we observed that this preferential ability in HIV-infected children over adults to generate bnAbs is associated with an enrichment of circulating follicular helper T-cells (TFH) with an effector phenotype, and the presence of IL-21 secreting HIV-specific TFH within lymphoid tissue germinal centers (GC). In adults, bnAbs development has been linked with high plasma levels of CXCL13, a chemoattractant for CXCR5-expressing TFH cells to the lymph node GC. We sought to test this relationship in HIV-infected children, but found no association between neutralization breadth and plasma levels of CXCL13, or with the Th2 cytokines IL-4 and IL-13, or the TFH associated factor Activin A. However, we did find an unexpected association between plasma IL-5 levels and bnAb development in these children. Importantly, although CXCL13 correlated with total circulating TFH cells, it was not associated with effector TFH. Additionally, raised CXCL13 expression was associated with a lower CD4 percentage, higher viral load and a loss of immune function, implying it is associated with progressive disease rather than HIV-specific GC activity in these subjects. Taken together, our data suggests that IL-5 should be evaluated further as a candidate plasma biomarker for HIV neutralization breadth and for monitoring vaccine responses in the pediatric age group.

HIV-Specific B Cell Frequency Correlates with Neutralization Breadth in Patients Naturally Controlling HIV-Infection

HIV-specific broadly neutralizing antibodies (bnAbs) have been isolated from patients with high viremia but also from HIV controllers that repress HIV-1 replication. In these elite controllers (ECs), multiple parameters contribute to viral suppression, including genetic factors and immune responses. Defining the immune correlates associated with the generation of bnAbs may help in designing efficient immunotherapies. In this study, in ECs either positive or negative for the HLA-B*57 protective allele, in treated HIV-infected and HIV-negative individuals, we characterized memory B cell compartments and HIV-specific memory B cells responses using flow cytometry and ELISPOT. ECs preserved their memory B cell compartments and in contrast to treated patients, maintained detectable HIV-specific memory B cell responses. All ECs presented IgG1 + HIV-specific memory B cells but some individuals also preserved IgG2 + or IgG3 + responses. Importantly, we also analyzed the capacity of sera from ECs to neutralize a panel of HIV strains including transmitted/founder virus. 29% and 21% of HLA-B*57 + and HLA-B*57 − ECs, respectively, neutralized at least 40% of the viral strains tested. Remarkably, in HLA-B*57 + ECs the frequency of HIV-Env-specific memory B cells correlated positively with the neutralization breadth suggesting that preservation of HIV-specific memory B cells might contribute to the neutralizing responses in these patients.

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In contrast to treated HIV-infected patients, elite controllers (ECs) maintain HIV-specific memory B cell responses.

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In HLA-B*57 + ECs, HIV-specific B cell frequency correlates positively with the neutralization breadth of tier-2 HIV strains.

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In HLA-B*57 + and HLA-B*57 − ECs different antibody functions are probably involved in suppressing HIV replication.

A fraction of HIV-1-infected individuals (so-called elite controllers, ECs) naturally control HIV-1 replication maintaining undetectable viral loads. Understanding the mechanisms implicated in natural control of HIV-1 infection will help in developing efficient HIV vaccines. In ECs, we analyzed the influence of B cell antibody responses. We show that in contrast to successfully treated HIV-1-infected patients, ECs preserve memory B cell compartments and maintain HIV-specific B cell responses. In ECs positive for the protective HLA-B*57 allele, HIV-specific memory B cell responses are positively associated with the breadth of HIV neutralization. These findings will help develop novel immunotherapies to fight HIV.