Natural killer cell responses to dendritic cells infected by the ANRS HIV-1 vaccine candidate, MVAHIV.

Innate mechanisms are critical for the development of the host immune responses to antigen. Particularly, early interaction between natural killer (NK) cells and dendritic cells (DC) greatly impacts the establishment of both innate and adaptive immune responses. In this study, using an autologous in vitro co-culture system we analyzed the NK cell response against MVAHIV-infected DC as well as the subsequent ability of these MVAHIV-primed NK cells to control HIV-1 infection in autologous DC. We found that NK cells responded early to MVAHIV- or MVAWT-infected DC in terms of degranulation and cytokine production. After a 4-day priming of NK cells by MVAHIV- or MVAWT-infected DC we observed an enhanced proliferation and modulation in the NK cell receptor repertoire expression. Interestingly, we found that MVAHIV-primed NK cells had a significant higher ability to control HIV-1 infection in autologous DC compared to MVAWT-primed NK cells; and this enhanced anti-HIV-1 activity appeared to be HIV-specific as MVAHIV-primed NK cells did not have a better ability to control other viral infections or respond against tumoral cells. Furthermore, we observed that NK cell receptors NKG2D and NKp46 modulate the priming of NK cells. This data provides evidence that in vitro NK cells can be primed by viral vector-infected DC, in the context of a NK/DC culture, to specifically target viral infected cells.

S100A9 protein is a novel ligand for the CD85j receptor and its interaction is implicated in the control of HIV-1 replication by NK cells.

BACKGROUND: The reportedly broad expression of CD85j across different immune cell types suggests an importance for this molecule in the human immune system. Previous reports have shown that this receptor interacts with several HLA class-I molecules, as well as with some viral proteins. We have demonstrated that the subset of CD85j + Natural Killer (NK) cells efficiently controls human immunodeficiency virus type 1 (HIV-1) replication in monocyte-derived dendritic cells (MDDC) in vitro and this led us to hypothesize that the CD85j + NK cell-mediated anti-HIV activity in MDDC is specifically dependent on the interaction between the CD85j receptor and unknown non-HLA class-I ligand(s). RESULTS: In this study, we focused our efforts on the identification of these non-described ligands for CD85j. We found that the CD85j receptor interacts with a calcium-binding proteins of the S100 family; namely, S100A9. We further demonstrated that HIV-1 infection of MDDC induces a modulation of S100A9 expression on surface of the MDDC, which potentially influences the anti-HIV-1 activity of human NK cells through a mechanism involving CD85j ligation. Additionally, we showed that stimulation of NK cells with exogenous S100A9 enhances the control of HIV-1 infection in CD4+ T cells. CONCLUSIONS: Our data show that S100A9 protein, through ligation with CD85j, can stimulate the anti-HIV-1 activity of NK cells.

Dynamic shift from CD85j/ILT-2 to NKG2D NK receptor expression pattern on human decidual NK during the first trimester of pregnancy.

During the first trimester of human pregnancy, Natural Killer (NK) cells of the maternal uterine mucosa (e.g. decidua) have a unique phenotype and are involved in crucial physiological processes during pregnancy. We investigated whether modifications of the NK receptor repertoire occur during the first trimester of pregnancy. We found significantly decreased expression of KIR2DL1/S1 and KIR2DL2/L3/S2 receptors, NKp30 and NKp44 activatory receptors, and the CD85j (ILT-2) inhibitory receptor. We also observed significantly increased expression of the NKG2D activatory receptor at the decidual NK cell surface. By flow cytometry, we further highlighted an evolution of NK subsets between 8 and 12 weeks of gestation, with a shift from the KIR2DL1/S1⁺/KIR2DL2/L3/S2⁺ subset towards the double negative subset, coupled with a decrease of the CD85j⁺/NKG2D⁻ subset in favour of the CD85j⁻/NKG2D⁺ subset. Furthermore, cell surface expression of NK receptor ligands, including CD85j and NKG2D ligands, has been characterized by flow cytometry on decidual immune CD14⁺ and CD3⁺ cells. HLA-G, the high affinity ligand of CD85j, was detected on both cell types. In contrast, NKG2D ligands ULBP-2 ULBP-3 and MICA/B were not expressed on CD14⁺ and CD3⁺ cells, however a variable expression of ULBP-1 was observed. The ligand expression of KIR2DL1/S1 and KIR2DL2/L3/S2 was also analyzed: the HLA-C molecule was expressed at a low level on some CD14⁺ cells whereas it was not detected on CD3⁺ cell surface. NK receptor ligands are known to be also expressed on the invading placental trophoblast cells. Thus, the phenotypic evolutions of decidual NK cells described in this present study may preserve their activation/inhibition balance during the first trimester of pregnancy.

Impact of age, gender, and race on circulating γδ T cells.

A major subset of human peripheral blood γδ T cells expresses the Vγ2Vδ2 T cell receptor and responds to malignant or infectious diseases. We noted significant differences in the numbers of Vγ2Vδ2 T cells in blood samples from healthy Caucasian CA or African American (AA) donors. On average, CA donors had 3.71% ± 4.37% Vδ2 cells (as a percentage of total lymphocytes) compared with 1.18% ± 2.14% Vδ2 cells for AA donors (p < 0.0001). Age and race had the greatest impact on Vδ2 cell levels; the effect of age was similar for both racial groups. The Vδ2 cell population was dominated, for both donor groups, by cells expressing the Vγ2-Jγ1.2 Vδ2 T cell receptor, an apparent result of strong positive selection and there was substantial overlap in the public Vγ2 clonotypes from both racial groups. Mechanisms for selection and amplification of Vδ2 cells are nearly identical for both groups, despite the significant difference in baseline levels. These data show that appropriate controls, matched for age and race, may be required for clinical studies of Vγ2Vδ2 T cells in infectious disease or cancer and raise important questions about the mechanisms regulating the levels of circulating Vδ2 cells.

Natural viral suppressors of HIV-1 have a unique capacity to maintain gammadelta T cells.

OBJECTIVE: To evaluate Vgamma2Vdelta2 T cells in a group of HIV-infected patients who suppress HIV replication without antiretroviral therapy (natural viral suppressors, NVSs). DESIGN: : It is a cross-sectional study. METHODS: We compared Vgamma2Vdelta2 T-cell frequency, T-cell repertoire, and responses to isopentenyl pyrophosphate stimulation between NVSs (n = 21) and HIV-uninfected controls (n = 27) and between NVSs and HIV-infected patients taking HAART with suppressed viral replication (HIV-P; n = 25). RESULTS: NVSs had a mean frequency of 1.06 +/- 0.82% CD3Vdelta2+ cells among total lymphocytes, which was significantly higher than both control groups (HIV-negative: 0.50 +/- 0.53%, P = 0.042; HIV-P: 0.34 +/- 0.37%, P = 0.002). The proportion of Vgamma2 chains correlating with the Vgamma2-Jgamma1.2 rearrangement was reduced among NVSs compared with HIV-negative controls (0.57 +/- 0.06 vs. 0.32 +/- 0.04; P = 0.016) but was increased compared with HIV-P patients (0.32 +/- 0.04 vs. 0.22 +/- 0.03; P = 0.03). NVSs had a similar baseline frequency of CD27/CD45RA effector cells (19.6 +/- 4.2%) compared with HIV-negative controls (20.8 +/- 12.9%; P = 0.35). CONCLUSION: The altered gammadelta T-cell receptor repertoire among NVS was consistent with the known effect of HIV-1 on these cells. Uniquely among all HIV-infected groups, NVS reconstituted the gammadelta T-cell population, eventually reaching levels significantly above controls. This capacity to recover gammadelta T-cell numbers and function distinguishes individuals who control HIV-1 with and without HAART.

Isopentenyl pyrophosphate-activated CD56+ {gamma}{delta} T lymphocytes display potent antitumor activity toward human squamous cell carcinoma.

PURPOSE: The expression of CD56, a natural killer cell-associated molecule, on alphabeta T lymphocytes correlates with their increased antitumor effector function. CD56 is also expressed on a subset of gammadelta T cells. However, antitumor effector functions of CD56(+) gammadelta T cells are poorly characterized. EXPERIMENTAL DESIGN: To investigate the potential effector role of CD56(+) gammadelta T cells in tumor killing, we used isopentenyl pyrophosphate and interleukin-2-expanded gammadelta T cells from peripheral blood mononuclear cells of healthy donors. RESULTS: Thirty to 70% of expanded gammadelta T cells express CD56 on their surface. Interestingly, although both CD56(+) and CD56(-) gammadelta T cells express comparable levels of receptors involved in the regulation of gammadelta T-cell cytotoxicity (e.g., NKG2D and CD94), only CD56(+) gammadelta T lymphocytes are capable of killing squamous cell carcinoma and other solid tumor cell lines. This effect is likely mediated by the enhanced release of cytolytic granules because CD56(+) gammadelta T lymphocytes expressed higher levels of CD107a compared with CD56(-) controls following exposure to tumor cell lines. Lysis of tumor cell lines is blocked by concanamycin A and a combination of anti-gammadelta T-cell receptor + anti-NKG2D monoclonal antibody, suggesting that the lytic activity of CD56(+) gammadelta T cells involves the perforin-granzyme pathway and is mainly gammadelta T-cell receptor/NKG2D dependent. Importantly, CD56-expressing gammadelta T lymphocytes are resistant to Fas ligand and chemically induced apoptosis. CONCLUSIONS: Our data indicate that CD56(+) gammadelta T cells are potent antitumor effectors capable of killing squamous cell carcinoma and may play an important therapeutic role in patients with head and neck cancer and other malignancies.

Failure to restore the Vgamma2-Jgamma1.2 repertoire in HIV-infected men receiving highly active antiretroviral therapy (HAART).

Gammadelta (gammadelta) T cells expressing the Vgamma2-Jgamma1.2Vdelta2 (Vgamma9-JPVdelta2, alternate nomenclature) T cell receptor (TCR) constitute the major peripheral blood population of gammadelta T cells in adult humans and are specifically depleted during human immunodeficiency virus (HIV) disease. Vgamma2-Jgamma1.2Vdelta2 T cells provide a convenient model for assessing the impact of antiretroviral therapy on cell populations that are not susceptible to direct infection because they do not express CD4 and depletion occurs by indirect mechanisms. We obtained longitudinal PBMC samples from 16 HIV-infected individuals who enrolled in the Multicenter AIDS Cohort Study (MACS) and were starting highly active antiretroviral therapy (HAART). Vgamma2-Jgamma1.2Vdelta2 T cells were depleted in these individuals as a result of HIV infection. Despite evidence for clinical benefits of HAART, the Vgamma2-Jgamma1.2Vdelta2 T cell repertoire did not recover after HAART initiation irrespective of treatment duration. These studies highlight important defects among cell subsets lost due to indirect effects of HIV.

Impacts of HIV infection on Vgamma2Vdelta2 T cell phenotype and function: a mechanism for reduced tumor immunity in AIDS.

HIV infection causes rapid and lasting defects in the population of Vgamma2Vdelta2 T cells. To fully describe the impact of HIV, we examined PBMC samples from HIV+ patients receiving highly active antiretroviral therapy, who had displayed prolonged viral control and CD4 counts above 300 cells/mm3. We observed lower frequencies of CD27-/CD45RA- Vgamma2Vdelta2 cells in HIV+ individuals when compared with controls, coupled with an increased proportion of CD45RA+ cells. These changes were common among 24 HIV+ patients and were not related to CD4 cell count or viral RNA burden. Vgamma2 cells from HIV+ individuals had lower expression of Granzyme B and displayed reduced cytotoxicity against Daudi targets after in vitro stimulation. There was increased expression of FasR (CD95) on Vgamma2 cells from HIV+ PBMC that may be a mechanism for depletion of Vgamma2 cells during disease. In addition to the well-characterized defects in the Vgamma2 repertoire and functional responses to phosphoantigen, the proportion of CD27-/CD45RA- Vgamma2Vdelta2 T cells after isopentenyl pyrophosphate stimulation was reduced sharply in HIV+ donors versus controls. Thus, HIV infection has multiple impacts on the circulating Vgamma2Vdelta2 T cell population that combine to reduce the potential effector activity in terms of tumor cytotoxicity. Changes in Vgamma2Vdelta2 T cells, along with concomitant effects on NK and NKT cells that also contribute to tumor surveillance, may be important factors for elevating the risk of malignancy during AIDS.

Individual Vgamma2-Jgamma1.2+ T cells respond to both isopentenyl pyrophosphate and Daudi cell stimulation: generating tumor effectors with low molecular weight phosphoantigens.

Human Vgamma2Vdelta2 T cells exhibit T cell receptor-dependent, MHC-unrestricted recognition of antigen and play important roles in tumor and pathogen immunity. To characterize antigen recognition by the Vgamma2Vdelta2 TCR, we used the combined approach of spectratyping and CDR3 sequence analysis that measures changes in the TCR repertoire before and after stimulation with a phosphoantigen (isopentenyl pyrophosphate) or an irradiated tumor cell line (Daudi B lymphoma). Here we describe common Vgamma2 chains that are substantially involved in the response to both phosphoantigens and tumor cells. The recognition properties of common Vgamma2 chains explains the observation that Vgamma2Vdelta2 T cells expanded by phosphoantigen stimulation specifically recognize and kill some but not all tumor cell lines. Our studies further justify efforts to stimulate tumor immunity by administering low molecular weight phosphoantigens and boosting the frequency and tumor effector functions of circulating Vgamma2Vdelta2 T cells.