Nicole F. Bernard

Increased proportion of KIR3DS1 homozygotes in HIV-exposed uninfected individuals.

Objectives:Natural killer (NK) cell activity is increased in individuals who remain uninfected despite repeated exposures to HIV. Given that a combined major histocompatibility complex (MHC) class I and killer immunoglobulin-like receptor (KIR) KIR3D genotype has been linked to rate of HIV disease progression, we assessed whether these genotypes played a role in protection from infection. Design:The study genotyped 80 HIV-exposed uninfected (EU) and 304 subjects in HIV primary infection (PI) at the MHC class IB and KIR3DS/L1 loci. Methods:KIR3D genotyping was performed by sequence-specific primer polymerase chain reaction using two pairs of specific primers for each locus. The MHC class IB locus was typed by sequence-specific oligonucleotide polymerase chain reaction and sequencing to resolve Bw4 and Bw6 alleles and the amino acid present at position 80. Results:Comparison of the genetic distribution of KIR3D, HLA Bw4 and HLA Bw4-I80 genotypes in EU versus PI subjects reveal an increased proportion of KIR3DS1 homozygotes in EU (11/80, 13.8%) compared to subjects in PI (16/304, 5.3%). Analyses of combined MHC class I and KIR3D expression show no differences between the two populations. Conclusions:Homozygosity for the activating NK receptor KIR3DS1, may contribute to the more active NK cell function observed in EU and their relative resistance to HIV infection.

A combined genotype of KIR3DL1 high expressing alleles and HLA-B*57 is associated with a reduced risk of HIV infection.

Objectives:Coexpression of certain combinations of natural killer cell receptor KIR3DL1 and HLA-B alleles is associated with slower time to AIDS. The strongest protection in terms of disease outcome in KIR3DL1 homozygotes (3DL1 hmz) is coexpression of HLA-B*57 and a set of KIR3DL1 genotypes (3DL1*h/*y) lacking alleles expressed at low levels on natural killer cells. We questioned whether this allele combination could also influence resistance to infection. Design:The genetic distribution of 3DL1*h/*y and HLA-B*57 was compared in 41 HIV-exposed uninfected and 186 recently HIV-infected 3DL1 hmz. Methods:KIR3DL1 subtyping was performed by sequencing the exons 3, 4, 5, 7–9. The major histocompatibility complex class IB locus was typed by sequence specific oligonucleotide PCR and sequencing to resolve Bw4 and Bw6 alleles and the amino acid present at position 80. Results:Percentage carriers of HLA-B*57 in HIV-exposed uninfected and individuals in a primary infection cohort was 12.2 and 4.3%, respectively (P = 0.0631), whereas that of 3DL1*h/*y was similar in both populations (P = 0.221). The 3DL1*h/*y-HLA-B*57 combined genotype was more frequent in exposed uninfected individuals (12.2%) than individuals in primary infection (2.7%) (P = 0.019; odds ratio, 5.03; 95% confidence intervals, 1.38–18.3). Conclusion:Coexpression of 3DL1*h/*y and B*57, which has been associated with a reduced risk of progressing to AIDS in HIV-infected individuals also lowers the risk of HIV infection in exposed uninfected individuals.

CD160 and PD-1 Co-Expression on HIV-Specific CD8 T Cells Defines a Subset with Advanced Dysfunction

Chronic viral infections lead to persistent CD8 T cell activation and functional exhaustion. Expression of programmed cell death-1 (PD-1) has been associated to CD8 T cell dysfunction in HIV infection. Herein we report that another negative regulator of T cell activation, CD160, was also upregulated on HIV-specific CD8 T lymphocytes mostly during the chronic phase of infection. CD8 T cells that expressed CD160 or PD-1 were still functional whereas co-expression of CD160 and PD-1 on CD8 T cells defined a novel subset with all the characteristics of functionally exhausted T cells. Blocking the interaction of CD160 with HVEM, its natural ligand, increased HIV-specific CD8 T cell proliferation and cytokine production. Transcriptional profiling showed that CD160−PD-1+CD8 T cells encompassed a subset of CD8+ T cells with activated transcriptional programs, while CD160+PD-1+ T cells encompassed primarily CD8+ T cells with an exhausted phenotype. The transcriptional profile of CD160+PD-1+ T cells showed the downregulation of the NFκB transcriptional node and the upregulation of several inhibitors of T cell survival and function. Overall, we show that CD160 and PD-1 expressing subsets allow differentiating between activated and exhausted CD8 T cells further reinforcing the notion that restoration of function will require multipronged approaches that target several negative regulators.

HIV Protective KIR3DL1 and HLA-B Genotypes Influence NK Cell Function Following Stimulation with HLA-Devoid Cells

Epidemiological studies in humans have implicated carriage of combinations of genes encoding certain KIR3DL1 (killer Ig-like receptor 3DL1) alleles and their HLA-Bw4 ligands in slower progression to AIDS, lower viral load and protection from infection. Given that the KIR3DL1*h/*y/HLA-B*57 genetic combination is strongly associated with favorable HIV outcomes, we measured responses from NK cells isolated from these individuals by multiparametric flow cytometry for cytokine secretion and degranulation in response to stimulation with HLA-devoid cells to assess whether the KIR/HLA compound genotypes linked to better HIV outcome favor increased NK cell functional potential. Our results indicate that NK cells from these individuals had increased functional potential, particularly in the KIR3DL1+ NK cell subset. These results support a link between KIR/HLA genotypes and NK cell function and could provide an explanation for the observation that some KIR/HLA combinations are associated protective phenotypes in the context of host-HIV interactions.

Thyroid-associated ophthalmopathy : a model for the association of organ-specific autoimmune disorders

The development of a characteristic ophthalmopathy is a feature of autoimmune diseases of the thyroid. The link between the conditions has not yet been discovered, but here Jack Wall and colleagues develop the theory that an autoimmune response to a 64 kDa antigen expressed on both thyroid and eye muscle membranes is responsible for this thyroid-associated ophthalmopathy.

The HIV-1 gp120 CD4-Bound Conformation Is Preferentially Targeted by Antibody-Dependent Cellular Cytotoxicity-Mediating Antibodies in Sera from HIV-1-Infected Individuals

ABSTRACT Recent studies have linked antibody Fc-mediated effector functions with protection or control of human immunodeficiency type 1 (HIV-1) and simian immunodeficiency (SIV) infections. Interestingly, the presence of antibodies with potent antibody-dependent cellular cytotoxicity (ADCC) activity in the Thai RV144 vaccine trial was suggested to correlate with decreased HIV-1 acquisition risk. These antibodies recently were found to recognize HIV envelope (Env) epitopes exposed upon Env-CD4 interaction. CD4 downregulation by Nef and Vpu, as well as Vpu-mediated BST-2 antagonism, were reported to modulate exposure of those CD4-induced HIV-1 Env epitopes and were proposed to play a role in reducing the susceptibility of infected cells to ADCC mediated by this class of antibodies. Here, we report the high prevalence of antibodies recognizing CD4-induced HIV-1 Env epitopes in sera from HIV-1-infected individuals, which correlated with their ability to mediate ADCC responses against HIV-1-infected cells, exposing these Env epitopes at the cell surface. Furthermore, our results indicate that Env variable regions V1, V2, V3, and V5 do not represent a major determinant for ADCC responses mediated by sera from HIV-1-infected individuals. Altogether, these findings suggest that HIV-1 tightly controls the exposure of certain Env epitopes at the surface of infected cells in order to prevent elimination by Fc-effector functions. IMPORTANCE Here, we identified a particular conformation of HIV-1 Env that is specifically targeted by ADCC-mediating antibodies present in sera from HIV-1-infected individuals. This observation suggests that HIV-1 developed sophisticated mechanisms to minimize the exposure of these epitopes at the surface of infected cells.

4-1BBL Induces TNF Receptor-Associated Factor 1-Dependent Bim Modulation in Human T Cells and Is a Critical Component in the Costimulation-Dependent Rescue of Functionally Impaired HIV-Specific CD8 T Cells

During chronic infection, HIV-specific CD8 T cells exhibit progressive signs of functional impairment, attributed to persistent antigenic stimulation, up-regulation of the inhibitory receptor PD-1, and declining T cell help. Strategies that directly improve CD8 T cell function offer the potential of restoring immune control of HIV. Although PD-1 expression has been identified as a cause of functional impairment in HIV, in this study, PD-1 expression was observed on only a subfraction of HIV-specific CD8 T cells in a subfraction of donors, whereas HIV-specific CTL from all donors exhibited a limited repertoire of effector functions. CD137L (4-1BBL) is emerging as an important stimulator of antiviral CD8 T cell responses. Regardless of the PD-1 status of the donors, here we show that 4-1BBL, when combined with CD80 or CD70, expands a population of Ag-specific CD8 T cells expressing multiple markers of effector function, from the functionally impaired starting population. In contrast, CD70 in combination with CD80 was insufficient for these effects and the related TNF family ligand, LIGHT, had negligible activity. The unique contribution of 4-1BBL correlated with down-regulation of the proapoptotic molecule Bim in activated CD8 T cells. Decreasing the level of TNFR-associated factor 1 in T cells using small interfering RNA resulted in increased levels of Bim in the 4-1BBL-stimulated T cells. Thus, costimulation via 4-1BBL leads to TNFR-associated factor 1-dependent Bim down-modulation in T cells, resulting in increased T cell expansion. These studies identify 4-1BBL as a critical component in therapeutic strategies aimed at improving CD8 T cell function.

Receptor-Ligand Requirements for Increased NK Cell Polyfunctional Potential in Slow Progressors Infected with HIV-1 Coexpressing KIR3DL1*h/*y and HLA-B*57

ABSTRACT Carriage of the natural killer (NK) receptor genotype KIR3DL1*h/*y with its HLA-B*57 ligand (*h/*y+B*57) is associated with slow time to AIDS and low viral load (VL). To provide a functional basis for these epidemiological observations, we assessed whether HIV-1-infected slow progressors (SP) carrying the *h/*y+B*57 compound genotype would have increased NK cell polyfunctional potential in comparison to SP with other killer immunoglobulin-like receptor (KIR)/HLA compound genotypes and whether this enhanced polyfunctionality was dependent upon the coexpression of both KIR3DL1*h/*y and HLA-B*57. The functional potential of NK cells was investigated by stimulating peripheral blood mononuclear cells with HLA-devoid targets or single HLA transfectants. Multiparametric flow cytometry was used to detect NK cells with seven functional profiles representing all permutations of CD107a expression and gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) secretion. NK cells from individuals carrying KIR3DL1 receptor–HLA-Bw4 ligand pairs had greater trifunctional responses than those from KIR3DL1 homozygotes (hmz), who were Bw6 homozygotes. NK cells from subjects carrying the *h/*y+B*57 genotypes exhibited the highest trifunctional potential, and this was dependent on cocarriage of the NK receptor and its ligand. Trifunctional cells secreted more of each function tested on a per-cell basis than each corresponding monofunctional NK subset. Although VL influenced NK functionality, individuals with defined KIR/HLA genotypes exhibited differences in NK cell polyfunctionality that could not be accounted for by VL alone. The protective effect of HLA-B*57 on slow progression to AIDS and low VL may be mediated through its interaction with KIR3DL1 alleles to educate NK cells for potent activity upon stimulation.

Evaluation of OX40 ligand as a costimulator of human antiviral memory CD8 T cell responses: Comparison with B7.1 and 4-1BBL

CTL are important effectors of antiviral immunity. Designing adjuvants that can induce strong cytotoxic T cell responses in humans would greatly improve the effectiveness of an antiviral vaccination or therapeutic strategy. Recent evidence suggests that, in addition to its well-established role in costimulation of CD4 T cell responses, OX40L (CD134) can directly costimulate mouse CD8 T cells. In this study, we evaluated the role of OX40L in costimulation of human antiviral CD8 T cell responses and compared it with two other important costimulators, B7.1 (CD80) and 4-1BBL (CD137L). Delivery of OX40L to human monocytes using a recombinant replication-defective adenovirus led to greater expansion, up-regulation of perforin, enhanced cytolytic activity, and increased numbers of IFN-γ- and TNF-α-producing antiviral memory CD8 T cells in cultures of total T cells. Synergistic or additive effects were observed when OX40L costimulation was combined with 4-1BBL (CD137L) or B7.1 (CD80) costimulation. In total T cell cultures, at low Ag dose, 4-1BBL provided the most potent costimulus for influenza-specific CD8 T cell expansion, followed by B7.1 (CD80) and then OX40L. For isolated CD8 T cells, 4-1BBL was also the most consistent costimulator, followed by B7.1. In contrast, OX40L showed efficacy in direct activation of memory CD8 T cells in only one of seven donors. Thus, OX40L costimulates human antiviral memory CD8 T cell responses largely through indirect effects and can enhance anti-influenza, anti-EBV, and anti-HIV responses, particularly in combination with 4-1BBL or B7.

APOBEC3G genetic variants and their association with risk of HIV infection in highly exposed Caucasians.

The cytosine deaminase APOBEC3G has been identified as a host factor that inhibits HIV-1 replication. We investigated whether genetic variants of APOBEC3G that could potentially affect the proteins expression or function were associated with the risk of infection in 122 Caucasians highly exposed to HIV-1. A novel C40693T variant was significantly associated with an increased risk of infection, suggesting that there might be a role for APOBEC3G in susceptibility to HIV-1 infection that warrants further investigation.