Jose Azocar

Interaction of NK inhibitory receptor genes with HLA-C and MHC class II alleles in Hepatitis C virus infection outcome

Natural killer cells are important in innate defense against viral infections. The interplay between stimulatory and inhibitory natural killer cell receptors and their corresponding human leukocyte antigen ligands are known to influence the outcome of acute Hepatitis C virus infection. Frequencies of NK receptor genes (8 inhibitory, 6 activating and 2 pseudogenes) and HLA class II alleles (DRB1, DQB1) were analyzed in 160 Puerto-Rican American drug users with Hepatitis C virus infection; 121 had chronic viremia (CV) and 39 were spontaneous clearance (SC). We further ruled out genetic stratification using short tandem repeats. Interaction between KIR gene receptor 2DL3/2DL3 and its ligand, C1/C1 of HLA-Cw alleles and spontaneous clearance was confirmed (p=0.03, OR=3.05). We also found a new interaction between the KIR receptor gene 2DL3 with HLA-DRB1*1201 (p=0.0001, OR=22) associated with SC, and an association of HLA DQB1*0501 (p=0.05, OR=0.30) with CV. Our findings suggested a role for MHC class II alleles in Hepatitis C virus peptide presentation to T cells together with NK ligand interaction involving pathways that will be useful for the development of immunotherapeutic interventions.

SENSITIVITY OF HUMAN NATURAL KILLER CELLS TO HYPERTHERMIA

Abstract Significantly less natural killer (NK) activity is exhibited by human lymphocytes when the NK assay is carried out at temperatures above 37°C. Hyperthermia seems to act directly on the NK effector cells. The effect is partially abrogated by treatment of the heated cells with human leucocyte interferon.

Protective KIR-HLA interactions for HCV infection in intravenous drug users.

Intravenous drug use has become the principal route of hepatitis C virus (HCV) transmission due to the sharing of infected needles. In this study, we analyzed the distribution of HLA-KIR genotypes among 160 Puerto Rican intravenous drug users (IDUs) with HCV infection and 92 HCV-negative Puerto Rican IDUs. We found a significant association between the presence of different combinations of KIR inhibitory receptor genes (KIR2DL2 and/or KIR2DL3, pC=0.01, OR=0.07; KIR2DL2 and/or KIR2DL3+KIR2DS4, pC=0.01, OR=0.39) and HLA-C1 homozygous genotypes (HLA-C1+KIR2DS4, pC=0.02, OR=0.43; HLA-C1+KIR2DL2+KIR2DS4, pC=0.02, OR=0.40) together with the activating receptor KIR2DS4 (HLA-C1+KIR2DS4+KIR2DL3 and/or KIR2DL2, pC=0.004, OR=0.38) with protection from HCV infection. Our findings in HCV-infected and non-infected IDUs suggest an important role for KIRs (KIR2DL2 and KIR2DL3) with group HLA-C1 molecules, in the presence of activating KIR2DS4, in protection from HCV infection. These results support the hypothesis that activator signaling, mediated by KIR2DS4, plays a determinant role in the regulation of NK cell antiviral-activity.

MHC class II genes in HCV viral clearance of hepatitis C infected Hispanic patients

The frequency of class II human leukocyte antigen (HLA) alleles in 112 infected patients of Hispanic ancestry with serology positive for hepatitis C virus (HCV) was investigated. Our studies failed to demonstrate significant association between class II HLA alleles and the outcome of HCV infection: chronic viremia versus spontaneous viral clearance. Our results suggest that the genes responsible for the outcome are unknown, so far, and those HLA associations reported in several ethnic groups may represent genetic markers in nonrandom association with the responsible genes involved in determining viral clearance or chronic viremia following HCV infection.

Changes in the expression of HLA and β2-microglobulin by cultured lymphoid cells

Changes in the expression of HLA and beta 2-microglobulin (beta 2-m) antigens by cultured human lymphoid cell lines were investigated. HLA expression was assayed by indirect trace binding radioimmunoassay (RIA) with monoclonal antibodies and by determining sensitivity to complement-dependent lysis by alloantisera. Lymphoid cells in culture were found to undergo changes in the expression of HLA and beta 2-m antigens characterized by decreased membrane expression of these antigens at high cell densities or after a prolonged period of cultivation. The decreased expression of HLA and beta 2-m antigens apparently is due neither to a masking phenomenon nor to a lack of nutrients or an accumulation of metabolites in the culture media but is perhaps mediated by a cell-to-cell contact mechanism. Human interferon was found to enhance the expression of HLA and beta 2-m, apparently overriding the effects on major histocompatibility complex (MHC) expression induced by cell density.

Genetic interactions of KIR and G1M immunoglobulin allotypes differ in obese from non-obese individuals with type 2 diabetes

We analyzed the natural killer cell immunoglobulin-like receptor (KIR) genes and immunoglobulin allotypes in the development of type 2 diabetes (T2D) based on body mass index (BMI) measurements (obese vs. non-obese) in Puerto Rican Americans. Genetic interactions between the KIR haplotype A homozygotes (HAH) and its fraction containing two inhibitory receptors 2DL3 and 2DL1 and the activating receptor 2DS4 with immunoglobulin allotypes were studied. We found a significant association between the HAH and T2D (p=0.002; OR=7.97) and its interaction with the immunoglobulin allotype z: GM f/f (-) (p=<0.0001; OR, not determined) only in non-obese individuals. This association were due to the interactions between the 2DL3/2DL3, 2DL1/2DL1, and 2DS4 fragment with GM f/f (-) in T2D patients (p=0.0017; OR=3.45). Analysis based on BMI demonstrated associations in both obese (p=0.037; OR=2.43; 95% CI=0.97-6.31) and non-obese individuals (p=<0.0001; OR=8.38; 95% CI=2.49-29.31). By contrast, the interaction of the GM allotype f/f (-) with the HAH fragment was associated with T2D only in non-obese individuals (p=<0.0001; OR=18.2; 95% CI=3.71-113.4). As expected, interaction of both HAH and its fragment with HLA-C groups ligands were significant. We used informative short tandem repeats (STRs) that distinguish major populations to determine genetic admixture and found that there was no genetic stratification in our cohort. Our findings are consistent with the possibility of an autoimmune and/or innateimmune component in the pathogenesis of T2D: NK receptors with chronic inflammation in obese and genetic interactions with G1M allotype in T2D non-obese possibly mediating autoimmunity.

Cell culture density modulates the incorporation of HLA antigens by enveloped viruses

Uninfected, as well as feline leukemia virus (FeLV) infected human cells cultured under high cell density conditions undergo changes in the expression of major histocompatibility complex (MHC) antigens, as determined by indirect trace binding radio immunoassay (RIA) using monoclonal anti-HLA antibodies and by decreased sensitivity to complement mediated cytotoxicity by anti-HLA alloantibodies. FeLV particles produced by the viral infected cells are also sensitive to neutralization by anti-HLA antibodies, suggesting that enveloped viral particles incorporated MHC antigens in the viral envelope. The amount of HLA antigens expressed in the viral enveloped, closely reflects the expression of HLA antigens by the virus-producer lymphoid cells. FeLV-infected HsB-2 (T) and SB (B) lymphoid cells cultured under high cell concentration condition show decreased expression of some HLA antigens (A2, B12, B17), and the viral particles produced by those cells also incorporate lower amounts of such antigens. Our results, based on the findings that human lymphoid cells (uninfected, as well as FeLV infected) show decreased expression of some HLA membrane determinants when grown under high cell density conditions, indicate that no viral selective mechanism operates in the incorporation of HLA determinants by enveloped viruses. Instead, our results suggest that viruses pick up MHC antigens from the host cell membrane according to the concentration of those antigens on the surface of the cells at the time of virus budding.

Interaction between immunoglobulin allotypes and NK receptor genes in diabetes post-hepatitis C virus infection

Genetic interactions between natural killer (NK) cells immunoglobulin-like receptor (KIR) genes and immunoglobulin allotypes have been previously reported in type 2 diabetes mellitus (DM) patients. Puerto Rican Americans with a history of intravenous drug use who developed DM following HCV infection (n=32) were compared to individuals infected with HCV without diabetes (n=121) and to DM non-infected individuals (n=95). Subjects were genotyped for KIRs and immunoglobulin allotypes. We found interactions of immunoglobulin allotypes KM3/KM3 with NK inhibitory receptors 2DL3/2DL3, 2DL1 in the absence of 2DS4 associated with susceptibility to DM in HCV infected individuals. These data suggest the possibility that a subset of patients with HCV could have an immune-mediated component contributing to the development of DM.