HIV-exposed and yet persistently uninfected individuals have been an intriguing, repeated observation in multiple studies, but uncertainty persists on the significance and implications of this in devising protective strategies against HIV. We carried out a cross-sectional analysis of exposed uninfected partners in a Ugandan cohort of heterosexual serodiscordant couples (37.5% antiretroviral therapy naive) comparing their T cell responses to HIV peptides with those of unexposed uninfected individuals. We used an objective definition of exposure and inclusion criteria, blinded ex vivo and cultured gamma interferon (IFN-γ) enzyme-linked immunospot assays, and multiparameter flow cytometry and intracellular cytokine staining to investigate the features of the HIV-specific response in exposed versus unexposed uninfected individuals. A response rate to HIV was detectable in unexposed uninfected (5.7%, 95% confidence interval [CI] = 3.3 to 8.1%) and, at a significantly higher level (12.5%, 95% CI = 9.7 to 15.4%, P = 0.0004), in exposed uninfected individuals. The response rate to Gag was significantly higher in exposed uninfected (10/50 [20.%]) compared to unexposed uninfected (1/35 [2.9%]) individuals (P = 0.0004). The magnitude of responses was also greater in exposed uninfected individuals but not statistically significant. The average number of peptide pools recognized was significantly higher in exposed uninfected subjects than in unexposed uninfected subjects (1.21 versus 0.47; P = 0.0106). The proportion of multifunctional responses was different in the two groups, with a higher proportion of single cytokine responses, mostly IFN-γ, in unexposed uninfected individuals compared to exposed uninfected individuals. Our findings demonstrate both quantitative and qualitative differences in T cell reactivity to HIV between HESN (HIV exposed seronegative) and HUSN (HIV unexposed seronegative) subject groups but do not discriminate as to whether they represent markers of exposure or of protection against HIV infection.
In 2009, the United Nations Estimated that 33.2 Million People worldwide were living with human immunodeficiency virus type 1 (HIV-1) infection and that 2.6 million people had been newly infected.1 The need for effective HIV-1 prevention has never been greater. In this review, we address recent critical advances in our understanding of HIV-1 transmission and acute HIV-1 infection. Fourth-generation HIV-1 testing, now available worldwide,2,3 will allow the diagnosis of infection in many patients and may lead to new treatments and opportunities for prevention.
A vaccine against human immunodeficiency virus (HIV) seems to be on the horizon. Correlates of risk of infection for the RV144 trial have been found. There is understanding of what makes HIV envelope–specific antibodies broadly neutralizing and new T cell vaccine approaches can overcome virus variability.
HIV infection is characterized by a gradual deterioration of immune function mainly in the CD4 compartment. To better understand the dynamics of HIV-specific T cells, we analyzed the kinetics and polyfunctional profiles of Gag-specific CD4+ and CD8+ T cell responses in 12 subtype C-infected individuals with different disease progression profiles from acute to chronic HIV infection. The frequencies of Gag-responsive CD4+ and CD8+ T cells showed distinct temporal kinetics. The peak frequency of Gag-responsive IFNγ+CD4+ T cell was observed at a median of 28 days (IQR: 21-81) post Fiebig I/II staging, whilst Gag-specific IFNγ+CD8+ T cell responses peaked at a median of 253 days (IQR: 136-401 and showed a significant biphasic expansion. The proportion of TNFα-expressing cells within the IFNγ+CD4+ T cell population increased (p=0.001) over time, whilst TNFα-expressing cells within IFNγ+CD8+ T cells declined (p=0.005). Both Gag-responsive CD4+ and CD8+ T cells showed decreased Ki67 expression within the first 120 days post Feibig I/II staging. Prior to the disappearance of Gag-responsive Ki67+CD4+ T cells, these cells positively correlated (p=0.00038) with viremia, indicating that early Gag-responsive CD4 events are shaped by viral burden. No such associations were observed in the Gag-specific CD8+ T cell compartment. Overall, these observations indicate that circulating Gag-responsive CD4+ and CD8+ T cell frequencies and functions are not synchronous and properties change rapidly at different tempos during early HIV infection.
Sant and McMichael discuss new advances in detecting CD4+ T cells at the right time and place during viral infection.
Protective immunity to chronic and acute viral infection relies on both the innate and adaptive immune response. Although neutralizing antibody production by B cells and cytotoxic activity of CD8+ T cells are well-accepted components of the adaptive immune response to viruses, identification of the specific role of CD4+ T cells in protection has been more challenging to establish. Delineating the contribution of CD4+ T cells has been complicated by their functional heterogeneity, breadth in antigen specificity, transient appearance in circulation, and sequestration in tissue sites of infection. In this minireview, we discuss recent progress in identifying the multiple roles of CD4+ T cells in orchestrating and mediating the immune responses against viral pathogens. We highlight several recent reports, including one published in this issue, that have employed comprehensive and sophisticated approaches to provide new evidence for CD4+ T cells as direct effectors in antiviral immunity.
Background. Most reported human H5N1 viral infections have been severe and were detected after hospital admission. A case ascertainment bias may therefore exist, with mild cases or asymptomatic infections going undetected. We sought evidence of mild or asymptomatic H5N1 infection by examining H5N1-specific T-cell and antibody responses in a high-risk cohort in Vietnam.
Methods. Peripheral blood mononuclear cells were tested using interferon-γ enzyme-linked immunospot T assays measuring the response to peptides of influenza H5, H3, and H1 hemagglutinin (HA), N1 and N2 neuraminidase, and the internal proteins of H3N2. Horse erythrocyte hemagglutination inhibition assay was performed to detect antibodies against H5N1.
Results. Twenty-four of 747 individuals demonstrated H5-specific T-cell responses but little or no cross-reactivity with H3 or H1 HA peptides. H5N1 peptide-specific T-cell lines that did not cross-react with H1 or H3 influenza virus HA peptides were generated. Four individuals also had antibodies against H5N1.
Conclusions. This is the first report of ex vivo H5 HA-specific T-cell responses in a healthy but H5N1-exposed population. Our results indicate that the presence of H5N1-specific T cells could be an additional diagnostic tool for asymptomatic H5N1 infection.
HIV-1 accumulates mutations in and around reactive epitopes to escape recognition and killing by CD8+ T cells. Measurements of HIV-1 time to escape should therefore provide information on which parameters are most important for T cell–mediated in vivo control of HIV-1. Primary HIV-1–specific T cell responses were fully mapped in 17 individuals, and the time to virus escape, which ranged from days to years, was measured for each epitope. While higher magnitude of an individual T cell response was associated with more rapid escape, the most significant T cell measure was its relative immunodominance measured in acute infection. This identified subject-level or “vertical” immunodominance as the primary determinant of in vivo CD8+ T cell pressure in HIV-1 infection. Conversely, escape was slowed significantly by lower population variability, or entropy, of the epitope targeted. Immunodominance and epitope entropy combined to explain half of all the variability in time to escape. These data explain how CD8+ T cells can exert significant and sustained HIV-1 pressure even when escape is very slow and that within an individual, the impacts of other T cell factors on HIV-1 escape should be considered in the context of immunodominance.
CD8-mediated virus inhibition can be detected in HIV-1-positive subjects who naturally control virus replication. Characterizing the inhibitory function of CD8+ T cells during acute HIV-1 infection (AHI) can elucidate the nature of the CD8+ responses that can be rapidly elicited and that contribute to virus control. We examined the timing and HIV-1 antigen specificity of antiviral CD8+ T cells during AHI. Autologous and heterologous CD8+ T cell antiviral functions were assessed longitudinally during AHI in five donors from the CHAVI 001 cohort using a CD8+ T cell-mediated virus inhibition assay (CD8 VIA) and transmitted/founder (T/F) viruses. Potent CD8+ antiviral responses against heterologous T/F viruses appeared during AHI at the first time point sampled in each of the 5 donors (Fiebig stages 1/2 to 5). Inhibition of an autologous T/F virus was durable to 48 weeks; however, inhibition of heterologous responses declined concurrent with the resolution of viremia. HIV-1 viruses from 6 months postinfection were more resistant to CD8+-mediated virus inhibition than cognate T/F viruses, demonstrating that the virus escapes early from CD8+ T cell-mediated inhibition of virus replication. CD8+ T cell antigen-specific subsets mediated inhibition of T/F virus replication via soluble components, and these soluble responses were stimulated by peptide pools that include epitopes that were shown to drive HIV-1 escape during AHI. These data provide insights into the mechanisms of CD8-mediated virus inhibition and suggest that functional analyses will be important for determining whether similar antigen-specific virus inhibition can be induced by T cell-directed vaccine strategies.
A modest change in HIV-1 fitness can have a significant impact on viral quasispecies evolution and viral pathogenesis, transmission and disease progression. To determine the impact of immune escape mutations selected by cytotoxic T lymphocytes (CTL) on viral fitness in the context of the cognate transmitted/founder (T/F) genome, we developed a new competitive fitness assay using molecular clones of T/F genomes lacking exogenous genetic markers and a highly sensitive and precise parallel allele-specific sequencing (PASS) method.
The T/F and mutant viruses were competed in CD4+ T-cell enriched cultures, relative proportions of viruses were assayed after repeated cell-free passage, and fitness costs were estimated by mathematical modeling. Naturally occurring HLA B57-restricted mutations involving the TW10 epitope in Gag and two epitopes in Tat/Rev and Env were assessed independently and together. Compensatory mutations which restored viral replication fitness were also assessed. A principal TW10 escape mutation, T242N, led to a 42% reduction in replication fitness but V247I and G248A mutations in the same epitope restored fitness to wild-type levels. No fitness difference was observed between the T/F and a naturally selected variant carrying the early CTL escape mutation (R355K) in Env and a reversion mutation in the Tat/Rev overlapping region.
These findings reveal a broad spectrum of fitness costs to CTL escape mutations in T/F viral genomes, similar to recent findings reported for neutralizing antibody escape mutations, and highlight the extraordinary plasticity and adaptive potential of the HIV-1 genome. Analysis of T/F genomes and their evolved progeny is a powerful approach for assessing the impact of composite mutational events on viral fitness.
Human immunodeficiency virus type I; Viral fitness; Cytotoxic T lymphocytes; Immune escape mutation; Transmitted/founder virus; Mathematical model
A large body of functional and epidemiological evidence have previously illustrated the impact of specific MHC class I subtypes on clinical outcome during HIV-1 infection, and these observations have recently been re-iterated in genome wide association studies (GWAS). Yet because of the complexities surrounding GWAS-based approaches and the lack of knowledge relating to the identity of rarer single nucleotide polymorphism (SNP) variants, it has proved difficult to discover independent causal variants associated with favourable immune control. This is especially true of the candidate variants within the HLA region where many of the recently proposed disease influencing SNPs appear to reflect linkage with ‘protective’ MHC class I alleles. Yet causal MHC-linked SNPs may exist but remain overlooked owing to the complexities associated with their identification. Here we focus on the ancestral TNFα promoter −237A variant (rs361525), shown historically to be in complete linkage disequilibrium with the ‘protective’ HLA-B*5701 allele. Many of the ancestral SNPs within the extended TNFα promoter have been associated with both autoimmune conditions and disease outcomes, however, the direct role of these variants on TNFα expression remains controversial. Yet, because of the important role played by TNFα in HIV-1 infection, and given the proximity of the −237 SNP to the core promoter, its location within a putative repressor region previously characterized in mice, and its disruption of a methylation-susceptible CpG dinucleotide motif, we chose to carefully evaluate its impact on TNFα production. Using a variety of approaches we now demonstrate that carriage of the A SNP is associated with lower TNFα production, via a mechanism not readily explained by promoter methylation nor the binding of transcription factors or repressors. We propose that the −237A variant could represent a minor causal SNP that additionally contributes to the HLA-B*5701-mediated ‘protective’ effect during HIV-1 infection.
Recombinant modified vaccinia virus Ankara expressing HIV-1 antigens (MVA.HIVA) was used in ELISpot assays to monitor HIV-1-specific T cell responses in infants. Responses to MVA.HIVA and HIV-1 peptides were examined in 13 infected and 81 exposed uninfected infants in Nairobi, Kenya. Responses to MVA.HIVA (38%) and peptide stimulation (38%) were similar in frequency (p = 1.0) and magnitude (mean 176 versus 385 HIVSFU/106, p = 0.96) in HIV-1 infected infants. In exposed uninfected infants, MVA.HIVA detected more positive responses and higher magnitude responses as compared to peptide. MVA.HIVA ELISpot is a sensitive method for quantification of HIV-1-specific CD8+ T cell responses in HIV-1 exposed infants. These results demonstrate the relevance of HIV-1 clade A consensus-derived immunogen HIVA for the viruses currently circulating in Nairobi.
Enzyme-linked immunospot assay; Exposed seronegatives; Mother to child transmission
Reliable methods for measuring human immunodeficiency virus (HIV) incidence are a high priority for HIV prevention. They are particularly important to assess the population-level effectiveness of new prevention strategies, to evaluate the community-wide impact of ongoing prevention programs, and to assess whether a proposed prevention trial can be performed in a timely and cost-efficient manner in a particular population and setting. New incidence assays and algorithms that are accurate, rapid, cost-efficient, and can be performed on easily-obtained specimens are urgently needed. On May 4, 2011, the Division of AIDS (DAIDS), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), sponsored a 1-day workshop to examine strategies for developing new assays to distinguish recent from chronic HIV infections. Participants included leading investigators, clinicians, public health experts, industry, regulatory specialists, and other stakeholders. Immune-based parameters, markers of viral sequence diversity, and other biomarkers such as telomere length were evaluated. Emerging nanotechnology and chip-based diagnostics, including algorithms for performing diverse assays on a single platform, were also reviewed. This report summarizes the presentations, panel discussions, and the consensus reached for pursuing the development of a new generation of HIV incidence assays.
The CHAVI002 study was designed to characterize immune responses, particularly HIV-specific T-cell responses, amongst 2 cohorts of HIV-exposed seronegative (HESN) individuals. The absence of a clear definition of HESNs has impaired comparison of research within and between such cohorts. This report describes two distinct HESN cohorts and attempts to quantify HIV exposure using a ‘HIV risk index’ (RI) model.
HIV serodiscordant couples (UK; 24, Uganda; 72) and HIV unexposed seronegative (HUSN) controls (UK; 14, Uganda; 26 couples, 3 individuals) completed sexual behavior questionnaires every 3 months over a 9 month period. The two cohorts were heterogeneous, with most HESNs in the UK men who have sex with men (MSM), while all HESNs in Uganda were in heterosexual relationships. Concordance of responses between partners was determined. Each participant’s sexual behavior score (SBS) was estimated based on the number and type of unprotected sex acts carried out in defined time periods. Independent HIV acquisition risk factors (partner plasma viral load, STIs, male circumcision, pregnancy) were integrated with the SBS, generating a RI for each HESN.
96 HIV serodiscordant couples completed 929 SBQs. SBSs remained relatively stable amongst the UK cohort, whilst decreasing from Visit 1 to 2 in the Ugandan cohort. Compared to the Ugandan cohort, SBSs and RIs in the UK cohort were lower at visit 1, and generally higher at later visits. Differences between the cohorts, with lower rates of ART use in Uganda and higher risk per-act sex in the UK, had major impacts on the SBSs and RIs of each cohort. There was one HIV transmission event in the UK cohort.
Employment of a risk quantification model facilitated quantification and comparison of HIV acquisition risk across two disparate HIV serodiscordant couple cohorts.
HIV-1 often evades cytotoxic T cell (CTL) responses by generating variants that are not recognized by CTLs. We used single-genome amplification and sequencing of complete HIV genomes to identify longitudinal changes in the transmitted/founder virus from the establishment of infection to the viral set point at 1 year after the infection. We found that the rate of viral escape from CTL responses in a given patient decreases dramatically from acute infection to the viral set point. Using a novel mathematical model that tracks the dynamics of viral escape at multiple epitopes, we show that a number of factors could potentially contribute to a slower escape in the chronic phase of infection, such as a decreased magnitude of epitope-specific CTL responses, an increased fitness cost of escape mutations, or an increased diversity of the CTL response. In the model, an increase in the number of epitope-specific CTL responses can reduce the rate of viral escape from a given epitope-specific CTL response, particularly if CD8+ T cells compete for killing of infected cells or control virus replication nonlytically. Our mathematical framework of viral escape from multiple CTL responses can be used to predict the breadth and magnitude of HIV-specific CTL responses that need to be induced by vaccination to reduce (or even prevent) viral escape following HIV infection.
The rapid evolution of Human Immunodeficiency Virus (HIV-1) allows studies of ongoing host–pathogen interactions. One key selective host factor is APOBEC3G (hA3G) that can cause extensive and inactivating Guanosine-to-Adenosine (G-to-A) mutation on HIV plus-strand DNA (termed hypermutation). HIV can inhibit this innate anti-viral defense through binding of the viral protein Vif to hA3G, but binding efficiency varies and hypermutation frequencies fluctuate in patients. A pivotal question is whether hA3G-induced G-to-A mutation is always lethal to the virus or if it may occur at sub-lethal frequencies that could increase viral diversification. We show in vitro that limiting-levels of hA3G-activity (i.e. when only a single hA3G-unit is likely to act on HIV) produce hypermutation frequencies similar to those in patients and demonstrate in silico that potentially non-lethal G-to-A mutation rates are ∼10-fold lower than the lowest observed hypermutation levels in vitro and in vivo. Our results suggest that even a single incorporated hA3G-unit is likely to cause extensive and inactivating levels of HIV hypermutation and that hypermutation therefore is typically a discrete “all or nothing” phenomenon. Thus, therapeutic measures that inhibit the interaction between Vif and hA3G will likely not increase virus diversification but expand the fraction of hypermutated proviruses within the infected host.
Human cells have conserved antiviral defense systems, which protect against a range of viruses. A key component of this innate, intra-cellular defense is APOBEC3G (hA3G), which can cause extensive and inactivating G-to-A mutations (termed hypermutation) in viral DNA. To circumvent this, human immunodeficiency virus type-1 (HIV-1) encodes a protein, Vif, which can bind hA3 and prevent its antiviral effects. Vif is however, not always fully efficient, and many HIV-1 infected patients harbor hypermutated sequences. A key question is whether hA3G also might generate sub-lethal levels of G-to-A mutations, which could increase viral evolution, possibly accelerating disease progression. If this were to occur, drugs and vaccine-induced CTL-responses targeting Vif might have counterproductive effects. We show through in vitro, in vivo, and in silico analyses that it is unlikely that hA3G-activity can enhance virus evolution. Thus, measures that inhibit the interaction between Vif and APOBEC3G are likely to only increase the fraction of hypermutated, inactivated HIV sequences in the infected host.
To date, CCR5 variants remain the only human genetic factors to be confirmed to impact HIV-1 acquisition. However, protective CCR5 variants are largely absent in African populations, in which sporadic resistance to HIV-1 infection is still unexplained. Here we perform a genome-wide association study (GWAS) in a population of 1,532 individuals from Malawi, a country with high prevalence of HIV-1 infection, to investigate whether common genetic variants associate with HIV-1 susceptibility in Africans. Using single nucleotide polymorphisms (SNPs) present on the genome-wide chip, we also investigated previously reported associations with HIV-1 susceptibility or acquisition. Recruitment was coordinated by the Center for HIV/AIDS Vaccine Immunology at two sexually transmitted infection clinics. HIV status was determined by HIV rapid tests and nucleic acid testing.
After quality control, the population consisted of 848 high-risk seronegative and 531 HIV-1 seropositive individuals. Logistic regression testing in an additive genetic model was performed for SNPs that passed quality control. No single SNP yielded a significant P-value after correction for multiple testing. The study was sufficiently powered to detect markers with genotype relative risk ≥ 2.0 and minor allele frequencies ≥12%. This is the first GWAS of host determinants of HIV-1 susceptibility, performed in an African population. The absence of any significant association can have many possible explanations: rarer genetic variants or common variants with weaker effect could be responsible for the resistance phenotype; alternatively, resistance to HIV-1 infection might be due to non-genetic parameters or to complex interactions between genes, immunity and environment.
Human immunodeficiency virus (HIV-1); acquisition; resistance; Genome Wide Association Study (GWAS); Africa
Polymorphism in the Human Leukocyte Antigen (HLA) region of chromosome is the major source of host genetic variability in HIV-1 outcome, but there is limited understanding of the mechanisms underlying the beneficial effect of protective class I alleles such as HLA-B57, B27 and B51. Taking advantage of a unique cohort infected with clade B’ HIV-1 through contaminated blood, in which many variables, such as the length of infection, the infecting viral strain and host genetic background are controlled, we performed a comprehensive study in order to understand HLA-B51 associated HIV-1 control. We focused on the T-cell responses against three dominant HLA-B51 restricted epitopes: Gag327-345(NI9) NANPDCKTI, Pol743-751(LI9) LPPVVAKEI and Pol283-289(TI8) TAFTIPSI. Mutations in all three dominant epitopes were significantly associated with HLA-B51 in the cohort. A clear hierarchy in selection of epitope mutations was observed through epitope sequencing. L743I in Position 1 of epitope LI9 was seen in most B51+ individuals, followed by V289X in Position 8 of the TI8, then A328S in Position 2 of the NI9 epitope was also seen in some B51+individuals. Good control of viral load and higher CD4+ counts were significantly associated with at least one detectable T cell response to un-mutated epitopes, whereas lower CD4+ counts and higher viral loads were observed in patients who had developed escape mutations in all three epitopes or who lacked T-cell responses specific to these epitope(s). We propose that patients with HLA-B51 benefit from having multiple layers of effective defence against the development of immune escape mutations.
Cultured ELISpot; HIV; IFN-γ; Latent Mycobacterium tuberculosis infection; T cell
Mutations within MHC class I-restricted epitopes have been studied in relation to T cell-mediated immune escape, but their impact on NK cells via interaction with killer Ig-like receptors (KIRs) during early HIV infection is poorly understood. In two patients acutely infected with HIV-1, we observed the appearance of a mutation within the B*57-restricted TW10 epitope (G9E) that did not facilitate strong escape from T cell recognition. The NK cell receptor KIR3DL1, carried by these patients, is known to recognize HLA-B*5703 and is associated with good control of HIV-1. Therefore, we tested whether the G9E mutation influenced the binding of HLA-B*5703 to soluble KIR3DL1 protein by surface plasmon resonance, and while the wild-type sequence and a second (T3N) variant were recognized, the G9E variant abrogated KIR3DL1 binding. We extended the study to determine the peptide sensitivity of KIR3DL1 interaction with epitopes carrying mutations near the C termini of TW10 and a second HLA-B*57-restricted epitope, IW9. Several amino acid changes interfered with KIR3DL1 binding, the most extreme of which included the G9E mutation commonly selected by HLA-B*57. Our results imply that during HIV-1 infection, some early-emerging variants could affect KIR-HLA interaction, with possible implications for immune recognition.
The authors that the number of activating and inhibitory KIR genes varies between individuals and plays a role in the regulation of immune mechanisms that determine HIV-1 control.
A genome-wide screen for large structural variants showed that a copy number variant (CNV) in the region encoding killer cell immunoglobulin-like receptors (KIR) associates with HIV-1 control as measured by plasma viral load at set point in individuals of European ancestry. This CNV encompasses the KIR3DL1-KIR3DS1 locus, encoding receptors that interact with specific HLA-Bw4 molecules to regulate the activation of lymphocyte subsets including natural killer (NK) cells. We quantified the number of copies of KIR3DS1 and KIR3DL1 in a large HIV-1 positive cohort, and showed that an increase in KIR3DS1 count associates with a lower viral set point if its putative ligand is present (p = 0.00028), as does an increase in KIR3DL1 count in the presence of KIR3DS1 and appropriate ligands for both receptors (p = 0.0015). We further provide functional data that demonstrate that NK cells from individuals with multiple copies of KIR3DL1, in the presence of KIR3DS1 and the appropriate ligands, inhibit HIV-1 replication more robustly, and associated with a significant expansion in the frequency of KIR3DS1+, but not KIR3DL1+, NK cells in their peripheral blood. Our results suggest that the relative amounts of these activating and inhibitory KIR play a role in regulating the peripheral expansion of highly antiviral KIR3DS1+ NK cells, which may determine differences in HIV-1 control following infection.
There is marked intrinsic variation in the extent to which individuals are able to control HIV-1. We have identified a genetic copy number variable region (CNV) in humans that plays a significant role in the control of HIV-1. This CNV is located in the genomic region that encodes the killer cell immunoglobulin-like receptors (KIRs) and specifically affects the KIR3DS1 and KIR3DL1 genes, encoding two KIRs that interact with human leukocyte antigen B (HLA-B) ligands. KIRs are expressed on the surface of natural killer (NK) cells, which serve as important players in the innate immune response, and are involved in the recognition of infected and malignant cells through a loss or alteration in “self” ligands. We use both genetic association and functional evidence to show a strong interaction between KIR3DL1 and KIR3DS1, indicating that increasing gene counts for KIR3DL1 confer increasing levels of protection against HIV-1, but only in the presence of at least one copy of KIR3DS1. This effect was associated with a dramatic increase in the abundance of KIR3DS1+ NK cells in the peripheral blood, and strongly associated with a more robust capacity of peripheral NK cells to suppress HIV-1 replication in vitro. This work provides one of the few examples of an association between a relatively common CNV and a human complex trait.
CD4 helper T cells producing the pro-inflammatory cytokine IL17 (Th17) have been implicated in a number of inflammatory arthritides including the Spondyloarthritides. Th17 development is promoted by IL23. Ankylosing Spondylitis (AS), the commonest Spondyloarthritis, is genetically associated with both HLA-B27 (B27) and with IL23 receptor polymorphisms, however the link remains unexplained. We have previously shown that B27 can form heavy chain dimers (termed B272), which, unlike classical HLA-B27, bind the Killer-cell Immunoglobulin-like Receptor KIR3DL2. Here we show that B272-expressing antigen presenting cells stimulate the survival, proliferation and IL17 production of KIR3DL2+ CD4 T. KIR3DL2+ CD4 T cells are expanded and enriched for IL17 production in the blood and synovial fluid of patients with spondyloarthritis (SpA). Despite KIR3DL2+ cells comprising a mean of just 15% of CD4 T in the peripheral blood of SpA patients, this subset accounted for 70% of the observed increase in Th17 numbers in SpA subjects compared to controls. TCR-stimulated peripheral blood KIR3DL2+CD4 T cell lines from SpA patients secreted four fold more IL17 than KIR3DL2+ lines from controls or KIR3DL2-negative CD4 T. Strikingly, KIR3DL2+ CD4 T cells account for the majority of peripheral blood CD4 T cell IL23 receptor expression and produce more IL17 in the presence of IL23. Our findings link HLA-B27 with IL-17 production and suggest new therapeutic strategies in AS/SpA.
Ankylosing Spondylitis; HLA-B27; IL17; Th17; KIR3DL2