Altered dendritic cell-natural killer interaction in Kenyan sex workers resistant to HIV-1 infection

Mucosal-homing natural killer cells are associated with aging in persons living with HIV

Natural killer (NK) cells are critical modulators of HIV transmission and disease. Recent evidence suggests a loss of NK cell cytotoxicity during aging, yet analysis of NK cell biology and aging in people with HIV (PWH) is lacking. Herein, we perform comprehensive analyses of people aging with and without HIV to determine age-related NK phenotypic changes. Utilizing high-dimensional flow cytometry, we analyze 30 immune-related proteins on peripheral NK cells from healthy donors, PWH with viral suppression, and viremic PWH. NK cell phenotypes are dynamic across aging but change significantly in HIV and on antiretroviral drug therapy (ART). NK cells in healthy aging show increasing ⍺4β7 and decreasing CCR7 expression and a reverse phenomenon in PWH. These HIV-associated trafficking patterns could be due to NK cell recruitment to HIV reservoir formation in lymphoid tissue or failed mucosal signaling in the HIV-infected gut but appear to be tight delineators of age-related NK cell changes.

Lymph node CXCR5+ NK cells associate with control of chronic SHIV infection

The persistence of virally infected cells as reservoirs despite effective antiretroviral therapy is a major barrier to an HIV/SIV cure. These reservoirs are predominately contained within cells present in the B cell follicles (BCFs) of secondary lymphoid tissues, a site that is characteristically difficult for most cytolytic antiviral effector cells to penetrate. Here, we identified a population of NK cells in macaque lymph nodes that expressed BCF-homing receptor CXCR5 and accumulated within BCFs during chronic SHIV infection. These CXCR5+ follicular NK cells exhibited an activated phenotype coupled with heightened effector functions and a unique transcriptome characterized by elevated expression of cytolytic mediators (e.g., perforin and granzymes, LAMP-1). CXCR5+ NK cells exhibited high expression of FcγRIIa and FcγRIIIa, suggesting a potential for elevated antibody-dependent effector functionality. Consistently, accumulation of CXCR5+ NK cells showed a strong inverse association with plasma viral load and the frequency of germinal center follicular Th cells that comprise a significant fraction of the viral reservoir. Moreover, CXCR5+ NK cells showed increased expression of transcripts associated with IL-12 and IL-15 signaling compared with the CXCR5- subset. Indeed, in vitro treatment with IL-12 and IL-15 enhanced the proliferation of CXCR5+ granzyme B+ NK cells. Our findings suggest that follicular homing NK cells might be important in immune control of chronic SHIV infection, and this may have important implications for HIV cure strategies.

Transient Increases in Inflammation and Proapoptotic Potential Are Associated with the HESN Phenotype Observed in a Subgroup of Kenyan Female Sex Workers

Interferon (IFN) -stimulated genes (ISGs) are critical effectors of IFN response to viral infection, but whether ISG expression is a correlate of protection against HIV infection remains elusive. A well-characterized subcohort of Kenyan female sex workers, who, despite being repeatedly exposed to HIV-1 remain seronegative (HESN), exhibit reduced baseline systemic and mucosal immune activation. This study tested the hypothesis that regulation of ISGs in the cells of HESN potentiates a robust antiviral response against HIV. Transcriptional profile of a panel of ISGs with antiviral function in PBMC and isolated CD4+ T cells from HESN and non-HESN sex worker controls were defined following exogenous IFN-stimulation using relative RT-qPCR. This study identified a unique profile of proinflammatory and proapoptotic ISGs with robust but transient responses to exogenous IFN-γ and IFN-α2 in HESN cells. In contrast, the non-HESN cells had a strong and prolonged proinflammatory ISG profile at baseline and following IFN challenge. Potential mechanisms may include augmented bystander apoptosis due to increased TRAIL expression (16-fold), in non-HESN cells. The study also identified two negative regulators of ISG induction associated with the HESN phenotype. Robust upregulation of SOCS-1 and IRF-1, in addition to HDM2, could contribute to the strict regulation of proinflammatory and proapoptotic ISGs in HESN cells. As reducing IRF-1 in the non-HESN cells resulted in the identified HESN ISG profile, and decreased HIV susceptibility, the unique HESN ISG profile could be a correlate of protection against HIV infection.

Defective expansion and function of memory like natural killer cells in HIV+ individuals with latent tuberculosis infection

Purpose

Tuberculosis (TB) is the leading cause of infectious disease related mortality, and only 10% of the infected individuals develop active disease. The likelihood of progression of latent tuberculosis infection (LTBI) to active TB disease is high in HIV infected individuals. Identification of HIV+ individuals at risk would allow treating targeted population, facilitating completion of therapy for LTBI and prevention of TB development. NK cells have an important role in T cell independent immunity against TB, but the exact role of NK cell subsets in LTBI and HIV is not well characterized.

Methods

In this study, we compared the expansion and function of memory like NK cells from HIV-LTBI+ individuals and treatment naïve HIV+LTBI+ patients in response to Mtb antigens ESAT-6 and CFP-10.

Results

In freshly isolated PBMCs, percentages of CD3^-CD56⁺ NK cells were similar in HIV+LTBI+ patients and healthy HIV-LTBI+ individuals. However, percentages of CD3^-CD56⁺CD16⁺ NK cells were higher in healthy HIV-LTBI+ individuals compared to HIV+LTBI+ patients. HIV infection also inhibited the expansion of memory like NK cells, production of IL-32α, IL-15 and IFN-γ in response to Mtb antigens in LTBI+ individuals.

Conclusion

We studied phenotypic, functional subsets and activation of memory like-NK cells during HIV infection and LTBI. We observed that HIV+LTBI+ patients demonstrated suboptimal NK cell and monocyte interactions in response to Mtb, leading to reduced IL-15, IFN-γ and granzyme B and increased CCL5 production. Our study highlights the effect of HIV and LTBI on modulation of NK cell activity to understand their role in development of interventions to prevent progression to TB in high risk individuals.

Reducing IRF-1 to Levels Observed in HESN Subjects Limits HIV Replication, But Not the Extent of Host Immune Activation

Cells from women who are epidemiologically deemed resistant to HIV infection exhibit a 40-60% reduction in endogenous IRF-1 (interferon regulatory factor-1), an essential regulator of host antiviral immunity and the early HIV replication. This study examined the functional consequences of reducing endogenous IRF-1 on HIV-1 replication and immune response to HIV in natural HIV target cells. IRF-1 knockdown was achieved in ex vivo CD4(+) T cells and monocytes with siRNA. IRF-1 level was assessed using flow cytometry, prior to infection with HIV-Bal, HIV-IIIB, or HIV-VSV-G. Transactivation of HIV long terminal repeats was assessed by p24 secretion (ELISA) and Gag expression (reverse transcription-polymerase chain reaction (RT-PCR)). The expression of IRF-1-regulated antiviral genes was quantitated with RT-PCR. A modest 20-40% reduction in endogenous IRF-1 was achieved in >87% of ex vivo-derived peripheral CD4(+) T cells and monocytes, resulted in >90% reduction in the transactivation of the HIV-1 genes (Gag, p24) and, hence, HIV replication. Curiously, these HIV-resistant women demonstrated normal immune responses, nor an increased susceptibility to other infection. Similarly, modest IRF-1 knockdown had limited impact on the magnitude of HIV-1-elicited activation of IRF-1-regulated host immunologic genes but resulted in lessened duration of these responses. These data suggest that early expression of HIV-1 genes requires a higher IRF-1 level, compared to the host antiviral genes. Together, these provide one key mechanism underlying the natural resistance against HIV infection and further suggest that modest IRF-1 reduction could effectively limit productive HIV infection yet remain sufficient to activate a robust but transient immune response.

Innate activation of MDC and NK cells in high-risk HIV-1-exposed seronegative IV-drug users who share needles when compared with low-risk nonsharing IV-drug user controls

BACKGROUND

Previous studies have described increased innate immune activation in HIV-1-exposed seronegative intravenous drug users (HESN-IDU), but have not addressed the independent role of injected drugs and/or repeated injections in driving immune activation.

METHODS

In this study, we investigated innate [natural killer (NK) cells and dendritic cells] and adaptive (HIV-specific antibody and CD8 T cell) immune parameters among a high-risk cohort of needle-sharing HESN-IDU subjects and compared them with low-risk nonsharing IDU subjects (NS-IDU) and non-drug-user controls.

RESULTS

We observed that HIV-specific antibody and CD8 T-cell responses were not detected in HESN-IDU subjects, yet innate immune cell activation was found to be significantly increased on NK cells (CD69 and CD107a upregulation) and myeloid dendritic cells (CD40 and CD83 upregulation) when compared with NS-IDU subjects or non-drug-user controls (P < 0.01 and P < 0.05, respectively). HESN-IDU subjects maintained strong NK-cell CD107a degranulation and cytokine (IFN-gamma, TNF-alpha, and MIP-1 beta) production after target cell incubation suggesting that constitutive innate activation does not induce functional exhaustion of innate cells in HESN-IDU subjects. NK activation in HESN-IDU subjects was independent of drug use patterns but was durable over time and correlated with plasma levels of IP-10 by Luminex analysis (ρ = 0.5073, P = 0.0059, n = 28).

CONCLUSIONS

Our results indicate that heightened innate immune cell activation in HESN-IDU subjects is not the result of the IV drugs and repeated injection practice itself, but to repeated exposure to factors intrinsic to sharing needles (ie, exposure to pathogens or heterologous cells among donor blood).

Increased Serpin A5 levels in the cervicovaginal fluid of HIV-1 exposed seronegatives suggest that a subtle balance between serine proteases and their inhibitors may determine susceptibility to HIV-1 infection

HIV-exposed seronegative individuals (HESNs) are persons who remain seronegative despite repeated exposure to HIV, suggesting an in vivo resistance mechanism to HIV. Elucidation of endogenous factors responsible for this phenomenon may aid in the development of new classes of microbicides and therapeutics. We compared cervicovaginal protein abundance profiles between high-risk HESN and two control groups: low-risk HESN and HIV-positives. Four iTRAQ-based quantitative experiments were performed using samples classified based on presence/absence of particular gynaecological conditions. After statistical analysis, two proteins were shown to be differentially abundant between high-risk HESNs and control groups. Serpin A5, a serine proteinase inhibitor and Myeloblastin, a serine protease, were up- and downregulated, respectively. Commercially available ELISA assays were used to confirm differential Serpin A5 levels. These results suggest that HIV resistance in CVF of HESNs is the result of a delicate balance between two complementary mechanisms: downregulation of serine proteinases and upregulation of their inhibitors.

Natural killer cell function in women at high risk for HIV acquisition: insights from a microbicide trial

OBJECTIVE

To assess the role of natural killer (NK) cells in HIV acquisition.

DESIGN

We conducted a nested case-control substudy to the Center for the AIDS Programme of Research in South Africa (CAPRISA004) tenofovir gel trial.

METHODS

Thirty women who acquired HIV infection (cases) and 30 women with high-risk sexual activity who remained HIV-negative (controls) were selected. Proliferation, degranulation and interferon-γ (IFNγ) secretion were measured by multiparametric flow cytometry after culture of recombinant human interleukin-2 (rhIL-2)-activated peripheral blood mononuclear cells with 721.221 cells or in-vitro HIV-infected, autologous CD4 T-cell blasts. Relationships between pre-acquisition NK cell responses and HIV acquisition were modeled with logistic regression models.

RESULTS

NK cells from cases had lower IFNγ responses to human leukocyte antigen-deficient 721.221 cells than controls (median %IFNγposNK cells: 13.7 vs. 21.6%, P = 0.03). rhIL-2-activated NK cells from cases had responses to autologous HIV-infected target cells distinct from controls: cases had fewer proliferating and more frequent degranulating NK cells. NK cells from cases had significantly lower IFNγ responses to in-vitro HIV-infected autologous T cells than controls even after adjusting for responses to uninfected blasts (median %IFNγposNK-cells: 0.53 vs. 2.09%, P = 0.007). Responses to in-vitro HIV-infected autologous T cells were significantly lower in herpes simplex virus 2 (HSV-2)-infected women (P = 0.003). IFNγ NK cell responses to autologous HIV-infected cells were associated with lower risk of HIV acquisition (odds ratio adjusted for age, gel arm, HSV-2 and immune activation: 0.582, 95% confidence interval 0.347-0.977, P = 0.04).

CONCLUSION

At the time of exposure to HIV, women with impaired NK cell IFNγ responses were more likely to acquire HIV infection. NK cells, as early responders to viral exposure, were associated with lower risk of HIV acquisition, independent of the intercalated effect of HSV-2 infection suppressing NK cell responses.

Innate immunity in the control of HIV/AIDS: recent advances and open questions

From the publication of the first AIDS issue onwards, major advances have been made in the field of innate immunity during HIV infection. Innate immunity can be defined as the first and unspecific lines of defense constitutively present and ready to be mobilized upon infection. Although a large body of literature adamantly highlights that innate immunity is a critical weapon of defense against HIV and its simian parents (simian immunodeficiency virus, SIV), innate immunity is still underexplored. Focusing on innate immunity may open new paths for the development of innovative therapeutics and vaccine strategies against HIV. Understanding innate immunity may shed light on the natural protection occurring in rare HIV-1-infected individuals who control their infection. This review focuses on innate mechanisms sensing HIV-1 entry and controlling HIV-1 infection, as well as promoting inflammation and shaping adaptive immunity.