Expression profile of KIR3DS1/KIR3DL1 receptors in association with immunological responses in TB, HIV and HIV/TB infected patients.

Several studies investigated KIR3DS1 and KIR3DL1 in the context of various infections. However, none of the studies were performed on KIR3DS1/L1 in association with IFN-É£/IL-10 in TB, HIV-1, and their confections. We aimed to evaluate KIR3DS1/KIR3DL1 expression in association with IFNÉ£/IL-10 in HIV-1 and TB mono-infections and HIV-1/TB confection and compared with uninfected controls using RTq PCR. We also performed correlation analysis between KIR3DS1, KIR3DL1, IFN-É£ and IL-10 in the respective cohorts. The overall expression of KIR3DS1 was found to be downregulated in all groups, whereas in HIV-1 and HIV-1/TB, the frequency of KIR3DS1(+) expression was significantly (p < 0.05) associated with undetected HIV-1 viral load. However, expression of KIR3DL1 was found to be significantly (p < 0.05) upregulated in HIV-1 only. In addition, IFNÉ£ expression was significantly (p < 0.05) decreased in TB, whereas in HIV-1/TB, IFNÉ£ expression was significantly (p < 0.05) increased. In contrast, IL-10 expression was significantly (p < 0.05) increased in HIV-1 and HIV-1/TB but not in TB. Also, we found significant positive correlation (p < 0.05, r = 0.61) between KIR3DL1 and IFNÉ£ expression in TB and negative correlation (p < 0.05, r = - 0.62) between KIR3DS1 and IL-10 in HIV-1/TB. In conclusion, we suggest that expression of KIR3DS1/L1 is associated with IFNÉ£/IL-10 responses and it is involved in modulating disease severity in HIV-1 and TB infections.

A Genome-Wide CRISPR/Cas9-Based Screen Identifies Heparan Sulfate Proteoglycans as Ligands of Killer-Cell Immunoglobulin-Like Receptors.

While human leukocyte antigen (HLA) and HLA-like proteins comprise an overwhelming majority of known ligands for NK-cell receptors, the interactions of NK-cell receptors with non-conventional ligands, particularly carbohydrate antigens, is less well described. We previously found through a bead-based HLA screen that KIR3DS1, a formerly orphan member of the killer-cell immunoglobulin-like receptor (KIR) family, binds to HLA-F. In this study, we assessed the ligand binding profile of KIR3DS1 to cell lines using Fc fusion constructs, and discovered that KIR3DS1-Fc exhibited binding to several human cell lines including ones devoid of HLA. To identify these non-HLA ligands, we developed a magnetic enrichment-based genome-wide CRISPR/Cas9 knock-out screen approach, and identified enzymes involved in the biosynthesis of heparan sulfate as crucial for the binding of KIR3DS1-Fc to K562 cells. This interaction between KIR3DS1 and heparan sulfate was confirmed via surface plasmon resonance, and removal of heparan sulfate proteoglycans from cell surfaces abolished KIR3DS1-Fc binding. Testing of additional KIR-Fc constructs demonstrated that KIR family members containing a D0 domain (KIR3DS1, KIR3DL1, KIR3DL2, KIR2DL4, and KIR2DL5) bound to heparan sulfate, while those without a D0 domain (KIR2DL1, KIR2DL2, KIR2DL3, and KIR2DS4) did not. Overall, this study demonstrates the use of a genome-wide CRISPR/Cas9 knock-out strategy to unbiasedly identify unconventional ligands of NK-cell receptors. Furthermore, we uncover a previously underrecognized binding of various activating and inhibitory KIRs to heparan sulfate proteoglycans that may play a role in NK-cell receptor signaling and target-cell recognition.

Upregulation of HLA-F expression by BK polyomavirus infection induces immune recognition by KIR3DS1-positive natural killer cells.

BK polyomavirus-associated nephropathy is a common complication after kidney transplantation leading to reduced graft function or loss. The molecular pathogenesis of BK polyomavirus-induced nephropathy is not well understood. A recent study had described a protective effect of the activating natural killer cell receptor KIR3DS1 in BK polyomavirus-associated nephropathy, suggesting a role of NK cells in modulating disease progression. Using an in vitro cell culture model of human BK polyomavirus infection and kidney biopsy samples from patients with BK polyomavirus-associated nephropathy, we observed significantly increased surface expression of the ligand for KIR3DS1, HLA-F, on BK polyomavirus-infected kidney tubular cells. Upregulation of HLA-F expression resulted in significantly increased binding of KIR3DS1 to BK polyomavirus-infected cells and activation of primary KIR3DS-positive natural killer cells. Thus, our data provide a mechanism by which KIR3DS-positive natural killer cells can control BK polyomavirus infection of the kidney, and rationale for exploring HLA-F/KIR3DS1 interactions for immunotherapeutic approaches in BK polyomavirus-associated nephropathy.

The Loss of HLA-F/KIR3DS1 Ligation Is Mediated by Hemoglobin Peptides.

The human leukocyte antigen (HLA)-Ib molecule, HLA-F, is known as a CD4+ T-cell protein and mediator of HIV progression. While HLA-Ia molecules do not have the chance to select and present viral peptides for immune recognition due to protein downregulation, HLA-F is upregulated. Post HIV infection, HLA-F loses the affinity to its activating receptor KIR3DS1 on NK cells leading to progression of the HIV infection. Several studies aimed to solve the question of the biophysical interface between HLA ligands and their cognate receptors. It became clear that even an invariant HLA molecule can be structurally modified by the variability of the bound peptide. We recently discovered the ability of HLA-F to select and present peptides and the HLA-F allele-specific peptide selection from the proteomic content using soluble HLA (sHLA) technology and a sophisticated MS method. We established recombinant K562 cells that express membrane-bound HLA-F*01:01, 01:03 or 01:04 complexes. While a recombinant soluble form of KIR3DS1 did not bind to the peptide-HLA-F complexes, acid elution of the peptides resulted in the presentation of HLA-F open conformers, and the binding of the soluble KIR3DS1 receptor increased. We used CD4+/HIV- and CD4+/HIV+ cells and performed an MS proteome analysis. We could detect hemoglobin as significantly upregulated in CD4+ T-cells post HIV infection. The expression of cellular hemoglobin in nonerythroid cells has been described, yet HLA-Ib presentation of hemoglobin-derived peptides is novel. Peptide sequence analysis from HLA-F allelic variants featured hemoglobin peptides as dominant and shared. The reciprocal experiment of binding hemoglobin peptide fractions to the HLA-F open conformers resulted in significantly diminished receptor recognition. These results underpin the molecular involvement of HLA-F and its designated peptide ligand in HIV immune escape.

Activating killer cell immunoglobulin-like receptors: Detection, function and therapeutic use.

Killer cell immunoglobulin-like receptors (KIRs) have a central role in the control of natural killer (NK) cell function. The functions of the activating KIRs, as compared to those of the inhibitory KIR, have been more difficult to define due to difficulties in antibody-mediated identification and their apparent low affinities for HLA class I. Immunogenetic studies have shown associations of activating KIRs with the outcome of autoimmune diseases, pregnancy-associated disorders, infectious diseases and cancers. Activating KIR are thus thought to have important roles in the control of natural killer cell functions and their role in disease. In this review, we discuss current knowledge on activating KIR, their ligands and, their roles in the pathogenesis and potential therapy of human diseases.

HLA-F on HLA-Null 721.221 Cells Activates Primary NK Cells Expressing the Activating Killer Ig-like Receptor KIR3DS1.

NK cells elicit important responses against transformed and virally infected cells. Carriage of the gene encoding the activating killer Ig-like receptor KIR3DS1 is associated with slower time to AIDS and protection from HIV infection. Recently, open conformers of the nonclassical MHC class Ib Ag HLA-F were identified as KIR3DS1 ligands. In this study, we investigated whether the interaction of KIR3DS1 on primary NK cells with HLA-F on the HLA-null cell line 721.221 (221) stimulated KIR3DS1+ NK cells. We used a panel of Abs to detect KIR3DS1+CD56dim NK cells that coexpressed the inhibitory NK cell receptors KIR2DL1/L2/L3, 3DL2, NKG2A, and ILT2; the activating NK cell receptors KIR2DS1/S2/S3/S5; and CCL4, IFN-γ, and CD107a functions. We showed that both untreated and acid-pulsed 221 cells induced a similar frequency of KIR3DS1+ cells to secrete CCL4/IFN-γ and express CD107a with a similar intensity. A higher percentage of KIR3DS1+ than KIR3DS1- NK cells responded to 221 cells when either inclusive or exclusive (i.e., coexpressing none of the other inhibitory NK cell receptors and activating NK cell receptors detected by the Ab panel) gating strategies were employed to identify these NK cell populations. Blocking the interaction of HLA-F on 221 cells with KIR3DS1-Fc chimeric protein or anti-HLA-F Abs on exclusively gated KIR3DS1+ cells reduced the frequency of functional cells compared with that of unblocked conditions for stimulated KIR3DS1+ NK cells. Thus, ligation of KIR3DS1 activates primary NK cells for several antiviral functions.

KIR3DL1 alleles and their epistatic interactions with human leukocyte antigen class I influence resistance and susceptibility to HIV-1 acquisition in the Pumwani sex worker cohort.

OBJECTIVE: To determine the associations of KIR3DL1/S1(3DL1/S1) and its epistatic interactions with human leukocyte antigen class I (HLA-I) alleles with resistance and susceptibility to HIV-1. DESIGN: Despite repeated exposure to HIV-1, a subset of women enrolled in the Pumwani sex worker cohort remain HIV uninfected. Previous studies have shown that specific HLA class I and II alleles were associated with this natural immunity. In this study, we investigated the association of 3DL1/S1 and its epistatic interactions with HLA-I, with resistance or susceptibility to HIV-1 acquisition. METHODS: We used a sequence-based typing method to genotype 3DL1/S1 of 641 women in this cohort. The association of 3DL1/S1 and its epistatic interactions with HLA-I were analyzed using SPSS statistics software. RESULTS: 3DL1041 is enriched in the HIV-1-resistant women [P = 0.009, Pc = 0.0468, odds ratio (OR): 3.359, 95% confidence interval (CI): 1.39-8.32], whereas, 3DL1020 was associated with susceptibility to HIV-1 infection before correction for multiple comparisons (P = 0.029, Pc = 0.0858, OR: 0.316, 95%CI: 0.10-1.04). Epistatic interactions between several 3DL1 alleles and specific HLA-I alleles were observed. Among them the cocarriage of 3DL1041 with Bw4 (P = 1E - 05, Pc = 0.0015, OR: 13.33, 95%CI: 3.43-51.9), or Bw6 (P = 0.008, Pc = 0.272, OR: 3.92, 95%CI: 1.51-10.17), increased the odds of remaining HIV-1 uninfected. Further, 3DL1041+/Bw4+ women who entered the cohort HIV negative remained uninfected (P = 0.032, Pc = 0.0858). Cocarriage of 3DL101501 with C02 : 10 (P = 2.73E - 07, Pc = 7.0954E - 06), B15 : 03 (P = 3.21E - 04, Pc = 0.0042), A24 supertype (P = 8.89E - 04, Pc = 0.0077), or A23 : 01 (P = 0.0036, Pc = 0.0236) was associated with increased susceptibility to seroconversion. CONCLUSION: The effects of interactions between 3DL1 and HLA-I alleles on resistance/susceptibility to HIV-1 infection suggest that innate immunity plays an important role in HIV-1 acquisition and should be studied and explored for HIV prevention.

HIV exposed seronegative (HESN) compared to HIV infected individuals have higher frequencies of telomeric Killer Immunoglobulin-like Receptor (KIR) B motifs; Contribution of KIR B motif encoded genes to NK cell responsiveness.

Previously, we showed that Killer Immunoglobulin-like Receptor (KIR)3DS1 homozygotes (hmz) are more frequent in HIV exposed seronegative (HESN) than in recently HIV infected (HIV+) individuals. KIR3DS1 encodes an activating Natural Killer (NK) cell receptor (NKR). The link between KIR genotype and HIV outcomes likely arises from the function that NK cells acquire through expression of particular NKRs. An initial screen of 97 HESN and 123 HIV+ subjects for the frequency of KIR region gene carriage observed between-group differences for several telomeric KIR region loci. In a larger set of up to 106 HESN and 439 HIV+ individuals, more HESN than HIV+ subjects were KIR3DS1 homozygotes, lacked a full length KIR2DS4 gene and carried the telomeric group B KIR haplotype motif, TB01. TB01 is characterized by the presence of KIR3DS1, KIR2DL5A, KIR2DS3/5 and KIR2DS1, in linkage disequilibrium with each other. We assessed which of the TB01 encoded KIR gene products contributed to NK cell responsiveness by stimulating NK cells from 8 HIV seronegative KIR3DS1 and TB01 motif homozygotes with 721.221 HLA null cells and evaluating the frequency of KIR3DS1+/-KIR2DL5+/-, KIR3DS1+/-KIR2DS1+/-, KIR3DS1+/-KIR2DS5+/- NK cells secreting IFN-γ and/or expressing CD107a. A higher frequency of NK cells expressing, versus not, KIR3DS1 responded to 721.221 stimulation. KIR2DL5A+, KIR2DS1+ and KIR2DS5+ NK cells did not contribute to 721.221 responses or modulate those by KIR3DS1+ NK cells. Thus, of the TB01 KIR gene products, only KIR3DS1 conferred responsiveness to HLA-null stimulation, demonstrating its ligation can activate ex vivo NK cells.

HLA-F and MHC-I Open Conformers Bind Natural Killer Cell Ig-Like Receptor KIR3DS1.

Based on previous findings supporting HLA-F as a ligand for KIR3DL2 and KIR2DS4, we investigated the potential for MHC-I open conformers (OCs) as ligands for KIR3DS1 and KIR3DL1 through interactions measured by surface plasmon resonance. These measurements showed physical binding of KIR3DS1 but not KIR3DL1 with HLA-F and other MHC-I OC while also confirming the allotype specific binding of KIR3DL1 with MHC-I peptide complex. Concordant results were obtained with biochemical pull-down from cell lines and biochemical heterodimerization experiments with recombinant proteins. In addition, surface binding of HLA-F and KIR3DS1 to native and activated NK and T cells was coincident with specific expression of the putative ligand or receptor. A functional response of KIR3DS1 was indicated by increased granule exocytosis in activated cells incubated with HLA-F bound to surfaces. The data extend a model for interaction between MHC-I open conformers and activating KIR receptors expressed during an inflammatory response, potentially contributing to communication between the innate and adaptive immune response.

Open conformers of HLA-F are high-affinity ligands of the activating NK-cell receptor KIR3DS1.

The activating natural killer (NK)-cell receptor KIR3DS1 has been linked to the outcome of various human diseases, including delayed progression of disease caused by human immunodeficiency virus type 1 (HIV-1), yet a ligand that would account for its biological effects has remained unknown. We screened 100 HLA class I proteins and found that KIR3DS1 bound to HLA-F, a result we confirmed biochemically and functionally. Primary human KIR3DS1(+) NK cells degranulated and produced antiviral cytokines after encountering HLA-F and inhibited HIV-1 replication in vitro. Activation of CD4(+) T cells triggered the transcription and surface expression of HLA-F mRNA and HLA-F protein, respectively, and induced binding of KIR3DS1. HIV-1 infection further increased the transcription of HLA-F mRNA but decreased the binding of KIR3DS1, indicative of a mechanism for evading recognition by KIR3DS1(+) NK cells. Thus, we have established HLA-F as a ligand of KIR3DS1 and have demonstrated cell-context-dependent expression of HLA-F that might explain the widespread influence of KIR3DS1 in human disease.

Hematopoietic stem cell transplantation: Improving alloreactive Bw4 donor selection by genotyping codon 86 of KIR3DL1/S1.

KIR3DL1 is a natural killer (NK) cell receptor that recognizes the Bw4 epitope of human leukocyte antigen (HLA) class I molecules. Following hematopoietic stem cell transplantation for patients lacking Bw4, KIR3DL1-expressing NK cells from Bw4-positive donors can be alloreactive and eliminate tumor cells. However, KIR3DL1 alleles having T instead of C at nucleotide 320 (encoding leucine 86 instead of serine 86) are not expressed on the cell surface. Thus, not all individuals testing positive for KIR3DL1 are optimal donors for Bw4-negative recipients. Therefore, we developed a method for genotyping codon 86, which was validated by its perfect correlation with NK cell phenotype for 100 donors of diverse KIR3DL1/S1 genotype. We typed 600 donors and found that ∼12.2% had the KIR3DL1 gene, but did not express cell-surface KIR3DL1. By contrast, high-expressing allotypes were identified when haplotypes from four families with duplicated KIR3DL1/S1 genes were characterized at high resolution. Identifying donors who have KIR3DL1 but lack cell-surface KIR3DL1 would refine donor selection. With this technique, the number of individuals identified who may not be optimal donors for Bw4-negative patients increases by threefold, when compared with standard methods. Taken together, we propose that allele typing of killer cell Ig-like receptor (KIR) polymorphisms should become a standard practice when selecting donors.

Comparison of the KIR3DS1/Bw4 distribution in Chinese healthy and acute myeloid leukemia individuals.

Killer cell immunoglobulin like receptor (KIR) 3DS1 is one of the most important activating receptors and some studies revealed that KIR3DS1 combined with HLA ligand was not related to acute myeloid leukemia (AML), but rare data was reported in Chinese population. In this study, KIR3DS1 gene polymorphisms and HLA-Bw4 were investigated in 189 Chinese AML patients compared with 166 healthy individuals. The results showed that the distributions of KIR3DS1, Bw4, 3DS1/Bw4 and 3DS1/Bw4-80I were insignificantly different between AML and healthy individuals. This study suggests that the presence of 3DS1 and HLA-Bw4 ligands have no effect on AML disease.

Human cytomegalovirus infection promotes rapid maturation of NK cells expressing activating killer Ig-like receptor in patients transplanted with NKG2C-/- umbilical cord blood.

NK cells are the first lymphoid population recovering after allogeneic hematopoietic stem cell transplantation and play a crucial role in early immunity after the graft. Recently, it has been shown that human CMV (HCMV) infection/reactivation can deeply influence NK cell reconstitution after umbilical cord blood transplantation by accelerating the differentiation of mature NKG2A(-) killer Ig-like receptor (KIR)(+) NK cells characterized by the expression of the NKG2C-activating receptor. In view of the hypothesis that NKG2C could be directly involved in NK cell maturation driven by HCMV infection, we analyzed the maturation and function of NK cells developing in three patients with hematological malignancies given umbilical cord blood transplantation from donors carrying a homozygous deletion of the NKG2C gene. We show that HCMV infection can drive rapid NK maturation, characterized by the expansion of CD56(dim)NKG2A(-)KIR(+) cells, even in the absence of NKG2C expression. Interestingly, this expanded mature NK cell subset expressed surface-activating KIR that could trigger NK cell cytotoxicity, degranulation, and IFN-γ release. Given the absence of NKG2C, it is conceivable that activating KIRs may play a role in the HCMV-driven NK cell maturation and that NK cells expressing activating KIRs might contribute, at least in part, to the control of infections after transplantation.

A comprehensive analysis of the binding of anti-KIR antibodies to activating KIRs.

Analysis of killer cell immunoglobulin-like receptor (KIR) expression has been notoriously difficult because of the cross-reactivity of available antibodies, in particular between activating and inhibitory isoforms. We undertook a comprehensive study of available anti-KIR antibodies binding to activating KIRs (a-KIRs). Using cell lines stably transfected with a-KIRs (KIR2DS1-S5 and KIR3DS1), we confirmed documented binding specificities. In addition, we show that clones HPMA4 and 143211-previously assumed to be specific for KIR2DS1/L1 and KIR2DL1, respectively-bind KIR2DS5 and KIR2DS3 (HPMA4), and KIR2DS5 (143211). Other antibodies with previously undocumented binding were JJC11.6 (recognizing KIR2DS3) and 5.133 (recognizing all a-KIRs except KIR2DS1 and KIR2DS3). The novel KIR2DS5 reactivities were confirmed by blocking with soluble KIR-Fc fusion proteins, and by reverse transcriptase-PCR analysis of sorted primary natural killer cells. In conclusion, we show formerly undocumented binding properties of anti-KIR antibodies. These cross-reactivities should be taken into account when analyzing KIR expression.

KIR3DS1/L1 and HLA-Bw4-80I are associated with HIV disease progression among HIV typical progressors and long-term nonprogressors.

BACKGROUND: Natural killer (NK) cells have emerged as pivotal players in innate immunity, especially in the defense against viral infections and tumors. Killer immunoglobulin-like receptors (KIRs)--an important recognition receptor expressed on the surface of NK cells--regulate the inhibition and/or activation of NK cells after interacting with human leukocyte antigen (HLA) class I ligands. Various KIR genes might impact the prognosis of many different diseases. The implications of KIR-HLA interaction in HIV disease progression remains poorly understood. METHODS: Here, we studied KIR genotypes, mRNA levels, HLA genotypes, CD4+ T cell counts and viral loads in our cohort of Human Immunodeficiency Virus (HIV)-infected individuals, a group that includes HIV long-term nonprogressors (LTNPs) and typical progressors (TPs). RESULTS: We found that the frequency of KIR3DS1/L1 heterozygotes with HLA-Bw4-80I gene was much higher in LTNPs than in TPs (P = 0.001) and that the KIR3DL1 homozygotes without HLA-Bw4-80I gene had higher viral loads and lower CD4+ T cell counts (P = 0.014 and P = 0.021, respectively). Our study also confirmed that homozygosity for the HLA-Bw6 allele was associated with rapid disease progression. In addition to the aforementioned results on the DNA level, we observed that higher level expression of KIR3DS1 mRNA was in LTNP group, and that higher level expression of KIR3DL1 mRNA was in TP group. CONCLUSIONS: Our data suggest that different KIR-HLA genotypes and different levels of transcripts associate with HIV disease progression.

The genetic predisposition of natural killer cell to BK virus-associated nephropathy in renal transplant patients.

BK virus (BKV) infection represents a serious complication in renal transplant patients resulting in BKV-associated nephropathy and subsequent allograft loss. Natural killer cells are crucial in the antiviral immune response; however, an understanding of the role of natural killer cells in protection against BKV is limited. To elucidate whether killer-cell immunoglobulin-like receptors and their interaction between donor-/recipient-related ligands have a role in BKV infection, we performed genotyping analysis in 48 kidney transplant recipients with a history of severe BKV infection/BKV-associated nephropathy and 110 recipients with stable renal function and no BKV reactivation. Of interest, we found that telomeric gene content motif was significantly associated with severe course of BKV infection/BKV-associated nephropathy and detected significantly higher percentage of patients with BKV-associated nephropathy carrying low numbers of activating receptors compared with the control group. Detailed analysis of each single receptor revealed significantly lower frequencies of the activating receptor KIR3DS1 in patients with BKV infection/nephropathy as compared with the controls. Thus, our study supports protective effects of activating receptors in BKV infection and suggest natural killer-cell-related genetic predisposition to the development of BKV-associated nephropathy.

NK cell responses to cytomegalovirus infection lead to stable imprints in the human KIR repertoire and involve activating KIRs.

Human natural killer (NK) cells are functionally regulated by killer cell immunoglobulin-like receptors (KIRs) and their interactions with HLA class I molecules. As KIR expression in a given NK cell is genetically hard-wired, we hypothesized that KIR repertoire perturbations reflect expansions of unique NK-cell subsets and may be used to trace adaptation of the NK-cell compartment to virus infections. By determining the human "KIR-ome" at a single-cell level in more than 200 donors, we were able to analyze the magnitude of NK cell adaptation to virus infections in healthy individuals. Strikingly, infection with human cytomegalovirus (CMV), but not with other common herpesviruses, induced expansion and differentiation of KIR-expressing NK cells, visible as stable imprints in the repertoire. Education by inhibitory KIRs promoted the clonal-like expansion of NK cells, causing a bias for self-specific inhibitory KIRs. Furthermore, our data revealed a unique contribution of activating KIRs (KIR2DS4, KIR2DS2, or KIR3DS1), in addition to NKG2C, in the expansion of human NK cells. These results provide new insight into the diversity of KIR repertoire and its adaptation to virus infection, suggesting a role for both activating and inhibitory KIRs in immunity to CMV infection.

Modulation of the natural killer cell KIR repertoire by cytomegalovirus infection.

Patients carrying activating killer cell immunoglobulin-like receptor (KIR) genes are significantly protected from CMV-associated complications after solid organ or hematopoietic stem cell transplantation. Whether previous infection with CMV affects NK-cell function in healthy donors is unknown. We studied the KIR repertoire and alterations of KIR expression after in vitro exposure to CMV in 54 healthy donors. The expression of neither activating nor inhibitory KIRs was different at baseline between 23 seropositive and 31 seronegative donors. However, after co-culture of NK cells with CMV-infected fibroblast cells, expression of the inhibitory receptors KIR2DL1 and KIR2DL3 and the activating receptor KIR3DS1 significantly increased in CMV-seropositive donors. In CMV-seronegative donors, changes were subtle and restricted to the subset of NK cells expressing NK-cell group antigen 2C (NKG2C). Expansion of inhibitory KIRs occurred exclusively in donors carrying the cognate HLA class I ligands, whereas the presence of the putative ligand HLA-Bw4 was not necessary for the expansion of KIR3DS1-expressing NK cells. Our data show that previous infection with CMV does not alter the resting NK-cell receptor repertoire, but appears to modify how NK cells respond to re-exposure to CMV in vitro.

Role of HLA-B α-3 domain amino acid position 194 in HIV disease progression.

HLA class I molecules play a role in the regulation of innate immune response. Therefore, the interaction of HLA class I molecules with different activating and inhibitory receptors leads to balancing the immune response. Among the different family of receptors, NK receptors KIR3DL1/S1 and LIR1, play a major role. Aim of this study was to evaluate the role of amino acid polymorphic positions of HLA class I molecules interacting with NK receptors in HIV progression. In order to minimize the influence of viral variability, a cohort of children with a nosocomial monophyletic HIV-1 infection from the Benghazi Children Hospital has been evaluated. To assess the role of single amino acid positions, we translated all HLA alleles in the different amino acid position polymorphisms. Interestingly, the polymorphism Val 194 located in the α3-domain of HLA-B, resulted associated with LTNP (LTNP=73.08%, FP=34.78%; P<0.02). When Val is present at position 194, HLA-B is known to interact with the receptor LIR1 (ILT2/LILRB1/CD85j). Therefore, we analyzed the role of the polymorphism in position 194 in HLA-B/LIR1 interaction by homology molecular modeling. The change Val to Ile at position 194 alters significantly the network of interaction between the amino acid residues of HLA-B and LIR1. In conclusion, considering the limitation of the small population evaluated, polymorphisms outside the peptide binding region of the HLA class I molecule can play a key role in HIV progression through interaction with other immune-relevant receptors.

Innate immune control of HIV.

Mounting evidence suggests a role for innate immunity in the early control of HIV infection, before the induction of adaptive immune responses. Among the early innate immune effector cells, dendritic cells (DCs) respond rapidly following infection aimed at arming the immune system, through the recognition of viral products via pattern recognition receptors. This early response results in the potent induction of a cascade of inflammatory cytokines, intimately involved in directly setting up an antiviral state, and indirectly activating other antiviral cells of the innate immune system. However, epidemiologic data strongly support a role for natural killer (NK) cells as critical innate mediators of antiviral control, through the recognition of virally infected cells through a network of receptors called the killer immunoglobulin-like receptors (KIRs). In this review, the early events in innate immune recognition of HIV, focused on defining the biology underlying KIR-mediated NK-cell control of HIV viral replication, are discussed.