Hepatitis C virus (HCV) infection is the most common blood borne infection in the U.S. with estimates of 4 million HCV-infected individuals in the U.S. and 170 million worldwide1. The majority (70%–80%) of HCV infections persist and about 30% of individuals with persistent infection develop chronic liver disease, including cirrhosis and hepatocellular carcinoma2. Epidemiological, viral, and host factors have been associated with the differences in HCV clearance or persistence and studies have demonstrated that a strong host immune response against HCV favors viral clearance3,4. Thus, variation in genes involved in the immune response may contribute to the ability to clear the virus. In a recent genome-wide association study, a single nucleotide polymorphism (rs12979860) 3kb upstream of the IL28B gene, which encodes the type III interferon IFN-λ3, was shown to associate strongly with more than a 2-fold difference in response to HCV drug treatment5. To determine the potential effect of rs12979860 variation on outcome to HCV infection in a natural history setting, we genotyped this variant in HCV cohorts comprised of individuals who spontaneously cleared the virus (N = 388) or had persistent infection (N = 620). We show that the C/C genotype strongly enhances resolution of HCV infection amongst individuals of both European and African ancestry (European: OR = 0.38, p = 10−7; African: OR = 0.32, p = 10−4; combined: OR = 0.33, p <10−12). To date, this is the strongest and most significant genetic effect associated with natural clearance of HCV, and these results implicate a primary role for IL28B in resolution of HCV infection.

Charles S., "Interleukin-1 polymorphisms associated with increased risk of gastric cancer" (2000). To evaluate dopaminergic cells of the dorsomedial cluster by tyrosine hydroxylase immunostaining, serial 4-mm sections were cut to include the entire brain. Immunopositive cells at the level of the giant interneuron commissure, posterior to the fan-shaped body, were counted in well oriented frontal sections at 1, 10, 30 and 60 days. At 1 day all control and experimental sections contained four or ®ve cells in the delineated region. At 30 and 60 days all controls showed four or ®ve cells. At 30 and 60 days all a-synucleinexpressing animals (a-synuclein, elav±GAL4 and a-synuclein, Ddc±GAL4 transheterozygotes) showed 0 or 1 tyrosine-hydroxylase-positive cell in the de®ned region. Tyrosinehydroxylase-positive cells outside the dorsomedial cluster were present, and served as internal controls for the immunostaining procedure. At least four, and usually between six and ten brains were examined for wild-type a-synuclein and each mutant a-synuclein. Controls included young and aged¯ies of the genotypes elav±GAL4/+ and Ddc±GAL4/+. We evaluated expression of a-synuclein and b-galactosidase on similar serial section preparations. Quanti®cation was simpli®ed in these experiments because no clear cellbody-associated a-synuclein or b-galactosidase immunoreactivity was observed in the aged a-synuclein transgenic¯ies at the times reported.For histological examination of retinas, heads were ®xed in glutaraldehyde and embedded in epon. Tangential retinal sections were prepared at a thickness of 1 mm and stained with toluidine blue (Fig 4).Standard electron microscopy was performed on brains from 25-day-old experimental (UAS±A30P a-synuclein/elav±GAL4) and control (elav±GAL4/+)¯ies. For immunoelectron microscopy, pre-embedding immunohistochemistry with an Hrp-congugated secondary antibody was performed on 60-day adult brains from experimental (UAS± A30P a-synuclein/elav±GAL4) and control (elav±GAL4/+)¯ies ®xed in 4% paraformaldehyde with 0.5% glutaraldehyde. Tissue was post-®xed in osmium and embedded in epon. Unstained ultrathin sections and ultrathin sections stained with uranyl acetate and lead citrate were examined. Climbing assayThe climbing assay was performed as described 19,20 . Forty¯ies were placed in a plastic vial, and gently tapped to the bottom of the vial. The number of¯ies at the top of the vial was counted after 18 s of climbing. Twenty trials were performed for each time point. The data shown represent results from a cohort of¯ies tested serially over 55 days. The experiment was repeated three times, with independently derived transgenic lines. Similar results were obtained from each experiment. The experiment was carried out under red light (Kodak Safelight Filter 1A). Control¯ies were of the genotype elav±GAL4/+. Experimental animals were of the following genotypes: (1) elav±GAL4/+; UAS±wild-type a-synuclein/+; (2) UAS±A30P a-synuclein/elav±GAL4; and (3) UAS±A53T a-synuclein/elav±GAL4.

Natural killer (NK) cells provide a central defense against viral infection by using inhibitory and activation receptors for major histocompatibility complex class I molecules as a means of controlling their activity. We show that genes encoding the inhibitory NK cell receptor KIR2DL3 and its human leukocyte antigen C group 1 (HLA-C1) ligand directly influence resolution of hepatitis C virus (HCV) infection. This effect was observed in Caucasians and African Americans with expected low infectious doses of HCV but not in those with high-dose exposure, in whom the innate immune response is likely overwhelmed. The data strongly suggest that inhibitory NK cell interactions are important in determining antiviral immunity and that diminished inhibitory responses confer protection against HCV.

Natural killer (NK) cells provide defense in the early stages of the innate immune response against viral infections by producing cytokines and causing cytotoxicity. The killer immunoglobulin-like receptors (KIRs) on NK cells regulate the inhibition and activation of NK-cell responses through recognition of human leukocyte antigen (HLA) class I molecules on target cells KIR and HLA loci are both highly polymorphic, and some HLA class I products bind and trigger cell-surface receptors specified by KIR genes. Here we report that the activating KIR allele KIR3DS1, in combination with HLA-B alleles that encode molecules with isoleucine at position 80 (HLA-B Bw4-80Ile), is associated with delayed progression to AIDS in individuals infected with human immunodeficiency virus type 1 (HIV-1). In the absence of KIR3DS1, the HLA-B Bw4-80Ile allele was not associated with any of the AIDS outcomes measured. By contrast, in the absence of HLA-B Bw4-80Ile alleles, KIR3DS1 was significantly associated with more rapid progression to AIDS. These observations are strongly suggestive of a model involving an epistatic interaction between the two loci. The strongest synergistic effect of these loci was on progression to depletion of CD4(+) T cells, which suggests that a protective response of NK cells involving KIR3DS1 and its HLA class I ligands begins soon after HIV-1 infection.

A selective advantage against infectious disease associated with increased heterozygosity at the human major histocompatibility complex [human leukocyte antigen (HLA) class I and class II] is believed to play a major role in maintaining the extraordinary allelic diversity of these genes. Maximum HLA heterozygosity of class I loci (A, B, and C) delayed acquired immunodeficiency syndrome (AIDS) onset among patients infected with human immunodeficiency virus-type 1 (HIV-1), whereas individuals who were homozygous for one or more loci progressed rapidly to AIDS and death. The HLA class I alleles B*35 and Cw*04 were consistently associated with rapid development of AIDS-defining conditions in Caucasians. The extended survival of 28 to 40 percent of HIV-1-infected Caucasian patients who avoided AIDS for ten or more years can be attributed to their being fully heterozygous at HLA class I loci, to their lacking the AIDS-associated alleles B*35 and Cw*04, or to both.

Allotypes of the natural killer (NK) cell receptor KIR3DL1 vary in both NK cell expression patterns and inhibitory capacity upon binding to their ligands, HLA-B Bw4 molecules, present on target cells. Using a sample size of over 1,500 human immunodeficiency virus (HIV)+ individuals, we show that various distinct allelic combinations of the KIR3DL1 and HLA-B loci significantly and strongly influence both AIDS progression and plasma HIV RNA abundance in a consistent manner. These genetic data correlate very well with previously defined functional differences that distinguish KIR3DL1 allotypes. The various epistatic effects observed here for common, distinct KIR3DL1 and HLA-B Bw4 combinations are unprecedented with regard to any pair of genetic loci in human disease, and indicate that NK cells may have a critical role in the natural history of HIV infection.

Decline of peak viremia during acute HIV-1 infection occurs before the development of vigorous adaptive immunity, and the level of decline correlates inversely with the rate of AIDS progression, implicating a potential role for the innate immune response in determining disease outcome. The combined expression of an activating natural killer (NK) cell receptor, the killer immunoglobulin-like receptor (KIR) 3DS1, and its presumed ligand, human leukocyte antigen (HLA)–B Bw4-80I, has been associated in epidemiological studies with a slow progression to AIDS. We examined the functional ability of NK cells to differentially control HIV-1 replication in vitro based on their KIR and HLA types. NK cells expressing KIR3DS1 showed strong, significant dose- and cell contact–dependent inhibition of HIV-1 replication in target cells expressing HLA-B Bw4-80I compared with NK cells that did not express KIR3DS1. Furthermore, KIR3DS1+ NK cells and NKLs were preferentially activated, and lysed HIV-1 infected target cells in an HLA-B Bw4-80I–dependent manner. These data provide the first functional evidence that variation at the KIR locus influences the effectiveness of NK cell activity in the containment of viral replication.

The discovery of dendritic cell (DC)-specific intercellular adhesion molecule (ICAM)-3–grabbing nonintegrin (DC-SIGN) as a DC-specific ICAM-3 binding receptor that enhances HIV-1 infection of T cells in trans has indicated a potentially important role for adhesion molecules in AIDS pathogenesis. A related molecule called DC-SIGNR exhibits 77% amino acid sequence identity with DC-SIGN. The DC-SIGN and DC-SIGNR genes map within a 30-kb region on chromosome 19p13.2-3. Their strong homology and close physical location indicate a recent duplication of the original gene. Messenger RNA and protein expression patterns demonstrate that the DC-SIGN–related molecule is highly expressed on liver sinusoidal cells and in the lymph node but not on DCs, in contrast to DC-SIGN. Therefore, we suggest that a more appropriate name for the DC-SIGN–related molecule is L-SIGN, liver/lymph node–specific ICAM-3–grabbing nonintegrin. We show that in the liver, L-SIGN is expressed by sinusoidal endothelial cells. Functional studies indicate that L-SIGN behaves similarly to DC-SIGN in that it has a high affinity for ICAM-3, captures HIV-1 through gp120 binding, and enhances HIV-1 infection of T cells in trans. We propose that L-SIGN may play an important role in the interaction between liver sinusoidal endothelium and trafficking lymphocytes, as well as function in the pathogenesis of HIV-1.