HLA-C Level Is Regulated by a Polymorphic Oct1 Binding Site in the HLA-C Promoter Region.

Differential HLA-C levels influence several human diseases, but the mechanisms responsible are incompletely characterized. Using a validated prediction algorithm, we imputed HLA-C cell surface levels in 228 individuals from the 1000 Genomes dataset. We tested 68,726 SNPs within the MHC for association with HLA-C level. The HLA-C promoter region variant, rs2395471, 800 bp upstream of the transcription start site, gave the most significant association with HLA-C levels (p = 4.2 × 10-66). This imputed expression quantitative trait locus, termed impeQTL, was also shown to associate with HLA-C expression in a genome-wide association study of 273 donors in which HLA-C mRNA expression levels were determined by quantitative PCR (qPCR) (p = 1.8 × 10-20) and in two cohorts where HLA-C cell surface levels were determined directly by flow cytometry (n = 369 combined, p < 10-15). rs2395471 is located in an Oct1 transcription factor consensus binding site motif where the A allele is predicted to have higher affinity for Oct1 than the G allele. Mobility shift electrophoresis demonstrated that Oct1 binds to both alleles in vitro, but decreased HLA-C promoter activity was observed in a luciferase reporter assay for rs2395471_G relative to rs2395471_A on a fixed promoter background. The rs2395471 variant accounts for up to 36% of the explained variation of HLA-C level. These data strengthen our understanding of HLA-C transcriptional regulation and provide a basis for understanding the potential consequences of manipulating HLA-C levels therapeutically.

Broadly reactive human CD8 T cells that recognize an epitope conserved between VZV, HSV and EBV.

Human herpesviruses are important causes of potentially severe chronic infections for which T cells are believed to be necessary for control. In order to examine the role of virus-specific CD8 T cells against Varicella Zoster Virus (VZV), we generated a comprehensive panel of potential epitopes predicted in silico and screened for T cell responses in healthy VZV seropositive donors. We identified a dominant HLA-A*0201-restricted epitope in the VZV ribonucleotide reductase subunit 2 and used a tetramer to analyze the phenotype and function of epitope-specific CD8 T cells. Interestingly, CD8 T cells responding to this VZV epitope also recognized homologous epitopes, not only in the other α-herpesviruses, HSV-1 and HSV-2, but also the γ-herpesvirus, EBV. Responses against these epitopes did not depend on previous infection with the originating virus, thus indicating the cross-reactive nature of this T cell population. Between individuals, the cells demonstrated marked phenotypic heterogeneity. This was associated with differences in functional capacity related to increased inhibitory receptor expression (including PD-1) along with decreased expression of co-stimulatory molecules that potentially reflected their stimulation history. Vaccination with the live attenuated Zostavax vaccine did not efficiently stimulate a proliferative response in this epitope-specific population. Thus, we identified a human CD8 T cell epitope that is conserved in four clinically important herpesviruses but that was poorly boosted by the current adult VZV vaccine. We discuss the concept of a "pan-herpesvirus" vaccine that this discovery raises and the hurdles that may need to be overcome in order to achieve this.

Recombinant structures expand and contract inter and intragenic diversification at the KIR locus.

BACKGROUND: The human KIR genes are arranged in at least six major gene-content haplotypes, all of which are combinations of four centromeric and two telomeric motifs. Several less frequent or minor haplotypes also exist, including insertions, deletions, and hybridization of KIR genes derived from the major haplotypes. These haplotype structures and their concomitant linkage disequilibrium among KIR genes suggest that more meaningful correlative data from studies of KIR genetics and complex disease may be achieved by measuring haplotypes of the KIR region in total. RESULTS: Towards that end, we developed a KIR haplotyping method that reports unambiguous combinations of KIR gene-content haplotypes, including both phase and copy number for each KIR. A total of 37 different gene content haplotypes were detected from 4,512 individuals and new sequence data was derived from haplotypes where the detailed structure was not previously available. CONCLUSIONS: These new structures suggest a number of specific recombinant events during the course of KIR evolution, and add to an expanding diversity of potential new KIR haplotypes derived from gene duplication, deletion, and hybridization.

Expression of candidate chromosome 3p21.3 tumor suppressor genes and down-regulation of BLU in some esophageal squamous cell carcinomas.

The expression of six chromosome 3p21.3 candidate tumor suppressor genes (BLU, FUS2, HYAL2, NPRL2, RASSF1A, and SEMA3B) in esophageal squamous cell carcinoma (ESCC) has been investigated. Reduced expression of BLU was detected in some ESCC cell lines and tumor tissues and the difference was quantitated by real-time quantitative polymerase chain reaction. Methylation specific-PCR revealed the down-regulation of BLU by epigenetic inactivation. However, exogenous expression of BLU did not functionally suppress tumorigenicity in nude mice. These results suggest that over-expression of BLU alone is not sufficient to inhibit tumorigenicity. Further studies on BLU interacting proteins are required to elucidate the possible role of BLU in the development of ESCC.

Functional characterization of the candidate tumor suppressor gene NPRL2/G21 located in 3p21.3C.

Initial analysis identified the NPRL2/G21 gene located in 3p21.3C, the lung cancer region, as a strong candidate tumor suppressor gene. Here we provide additional evidence of the tumor suppressor function of NPRL2/G21. The gene has highly conserved homologs/orthologs ranging from yeast to humans. The yeast ortholog, NPR2, shows three highly conserved regions with 32 to 36% identity over the whole length. By sequence analysis, the main product of NPRL2/G21 encodes a soluble protein that has a bipartite nuclear localization signal, a protein-binding domain, similarity to the MutS core domain, and a newly identified nitrogen permease regulator 2 domain with unknown function. The gene is highly expressed in many tissues. We report inactivating mutations in a variety of tumors and cancer cell lines, growth suppression of tumor cells with tet-controlled NPRL2/G21 transgenes on plastic Petri dishes, and suppression of tumor formation in SCID mice. Screening of 7 renal, 5 lung, and 7 cervical carcinoma cell lines showed homozygous deletions in the 3' end of NPRL2 in 2 renal, 3 lung, and 1 cervical (HeLa) cell line. Deletions in the 3' part of NPRL2 could result in improper splicing, leading to the loss of the 1.8 kb functional NPRL2 mRNA. We speculate that the NPRL2/G21 nuclear protein may be involved in mismatch repair, cell cycle checkpoint signaling, and activation of apoptotic pathway(s). The yeast NPR2 was shown to be a target of cisplatin, suggesting that the human NPRL2/G21 may play a similar role. At least two homozygous deletions of NPRL2/G21 were detected in 6 tumor biopsies from various locations and with microsatellite instability. This study, together with previously obtained results, indicates that NPRL2 is a multiple tumor suppressor gene.

The RASSF1A tumor suppressor gene is inactivated in prostate tumors and suppresses growth of prostate carcinoma cells.

We analyzed expression status of the recently identified tumor suppressor geneRASSF1A in primary prostate carcinomas and in prostate cell lines. We found complete methylation of the RASSF1A promoter in 63% of primary microdissected prostate carcinomas (7 of 11 samples). The remaining 4 samples (37%) were partially methylated, possibly because of contamination with normal cells. No promoter methylation was observed in matching normal prostate tissues. High levels of RASSF1A transcript and no methylation of RASSF1A promoter were found in explanted primary normal prostate epithelial and stromal cells. Complete silencing and methylation of RASSF1A promoter was observed in five widely used prostate carcinoma cell lines, which acquired the ability to grow in culture spontaneously, including LNCaP, PC-3, ND-1, DU-145, 22Rv1, and one primary prostate carcinoma immortalized by overexpression of the human telomerase catalytic subunit (RC-58T/hTERT). However, no silencing of RASSF1A was found in four other prostate carcinoma cell lines, which were adapted for cell culture after transformation with human papillomaviral DNA. Suppression of cell growth in vitro was demonstrated after the reintroduction of RASSF1A-expressing construct into LNCaP prostate carcinoma cells. Our data implicate the RASSF1A gene in human prostate tumorigenesis.

Amino acid residues that are important for Hyal2 function as a receptor for jaagsiekte sheep retrovirus.

BACKGROUND: Infection by jaagsiekte sheep retrovirus (JSRV) and by enzootic nasal tumor virus (ENTV) depends on cell-surface expression of the virus entry receptor, hyaluronidase 2 (Hyal2). Human Hyal2 binds the envelope (Env) proteins of these viruses and is functional as a receptor, but Hyal2 from mice does not bind Env nor does it mediate entry of either virus. Here we have explored the amino acid determinants that account for the difference in receptor function. RESULTS: Analysis of human-mouse Hyal2 chimeric proteins showed that amino acid differences responsible for the difference in Hyal2 receptor activity were localized to the central third of Hyal2. Human Hyal2 mutants containing single or double amino acid replacements with the respective mouse amino acids were generated across this region and were assayed for activity. None of the single or double mutation reduced the receptor activity of human Hyal2 by more than 10-fold, whereas mouse Hyal2 activity is reduced 1,000-fold from that of human Hyal2. While the 3-dimensional structures of mammalian Hyal2 proteins are unknown, bee venom hyaluronidase shows significant amino acid similarity to human and mouse Hyal2 and its structure has been determined. Many mutations having the largest negative effects on human Hyal2 function mapped to a small region of the bee venom hyaluronidase close to but not overlapping the active site of the enzyme, suggesting that this site represents the binding site for Env. Analysis of synonymous and non-synonymous nucleotide substitutions in the coding sequences of multiple mammalian Hyal2 proteins shows that the proteins are undergoing strong selection for amino acid conservation. We found no evidence for positive selection of amino acid changes that might reflect evolution of mammalian hosts to resist JSRV or ENTV infection. CONCLUSION: These results show that the greatly reduced receptor activity of mouse Hyal2 in comparison to that of human Hyal2 is determined by multiple amino acid changes acting in concert. In particular, no one amino acid change blocks infection. However, the most important amino acids map to a small patch on a predicted 3-dimensional Hyal2 structure, which may represent the binding site for Env.

Impact of protective killer inhibitory receptor/human leukocyte antigen genotypes on natural killer cell and T-cell function in HIV-1-infected controllers.

OBJECTIVE: Both protective T-cell genotypes and natural killer (NK) cell genotypes have been associated with delayed progression to AIDS and shown to be co-inherited in HIV-1-infected individuals who limit viral replication in absence of antiretroviral therapy ('controllers'). However, a comparative analysis of the genotype and function of the innate and adaptive immune compartments in HIV-1-infected controller individuals has been understudied to date. DESIGN: Here, we simultaneously tested NK and T-cell function in controllers to investigate the mechanism(s) that might account for host immune control over viral replication. METHODS: We measured CD8 T-cell responses against HIV-1 utilizing overlapping 15-mer peptides spanning the HIV-1 consensus clade B Gag protein and tested NK cell degranulation and cytokine secretion against tumor target cells following interferon-α (IFNα) stimulation. RESULTS: Among a cohort of 37 controllers, the presence of protective major histocompatibility complex class I human leukocyte antigen (HLA) alleles (such as HLA-B*57) was not correlated with HIV-specific CD8 responses. In contrast, the inheritance of a protective killer inhibitory receptor KIR3DL1*h/*y receptor genotype along with the corresponding HLA-Bw4*80I ligand was associated with significantly heightened target cell-induced NK degranulation and cytokine secretion following IFNα stimulation (P = 0.0201, n = 13). Interestingly, we observed a significant inverse association between the IFNα stimulated NK response to K562 cells and the HIV-specific CD8 T-cell response to Gag among elite controllers (rho = -0.8321, P = 0.0010, n = 12). CONCLUSION: Together, these results suggest that heightened NK responses can be evidenced independently of HIV-specific T-cell responses in HIV-1-infected elite controllers.

Increased plasmacytoid dendritic cell maturation and natural killer cell activation in HIV-1 exposed, uninfected intravenous drug users.

BACKGROUND: Increased natural killer (NK) activation has been associated with resistance to HIV-1 infection in several cohorts of HIV-1 exposed, uninfected individuals. Inheritance of protective NK receptor alleles (KIR3DS1 and KIR3DL1) has also been observed in a subset of HIV-1 exposed, uninfected individuals. However, the exact mechanism contributing to NK activation in HIV-1 exposed, uninfected intravenous drug users (EU-IDU) remains to be elucidated. OBJECTIVE: We investigated the role of both host genotype and pathogen-induced dendritic cell modulation of NK activation during high-risk activity in a cohort of 15 EU-IDU individuals and 15 control, uninfected donors from Philadelphia. DESIGN: We assessed the activation status of NK cells and dendritic cells by flow cytometry and utilized functional assays of NK-DC cross-talk to characterize the innate immune compartment in EU-IDU individuals. RESULTS: As previously reported, NK cell activation (CD69) and/or degranulation (CD107a) was significantly increased in EU-IDU individuals compared with control uninfected donors (P = 0.0056, n = 13). Genotypic analysis indicated that the frequency of protective KIR (KIR3DS1) and HLA-Bw4*80I ligands was not enriched in our cohort of EU-IDU individuals. Rather, plasmacytoid dendritic cells (PDC) from EU-IDU exhibited heightened maturation (CD83) compared with control uninfected donors (P = 0.0011, n = 12). When stimulated in vitro, both PDCs and NK cells from EU-IDU individuals maintained strong effector cell function and did not exhibit signs of exhaustion. CONCLUSION: Increased maturation of PDCs is associated with heightened NK activation in EU-IDU individuals suggesting that both members of the innate compartment may contribute to resistance from HIV-1 infection in EU-IDU.

Drug-susceptible HIV-1 infection despite intermittent fixed-dose combination tenofovir/emtricitabine as prophylaxis is associated with low-level viremia, delayed seroconversion, and an attenuated clinical course.

BACKGROUND: Continued high rates of HIV-1 transmission have fueled interest in the use of antiretrovirals to prevent infection. Attenuated infection with failure of tenofovir as prophylaxis has been reported in animal models. Here, we report a case of HIV-1 infection despite intermittent use of fixed-dose combination tenofovir and emtricitabine (FTC). METHODS: The patient was treated with tenofovir DF/FTC for reported repeated high-risk sexual exposures. After seroconversion, he was subjected to routine laboratory testing, CCR5 and HLA genotyping, and biopsy of gastrointestinal (GI) tissue. Resistance testing was performed both as bulk sequencing of plasma and cloning and sequencing of virus derived from plasma, peripheral blood mononuclear cells, and GI tissue. RESULTS: In this patient with no readily identifiable modifying host factors, acute HIV-1 infection with tenofovir DF/FTC-susceptible HIV-1 was associated with an attenuated clinical course, very low postseroconversion HIV-1 RNA levels, slow kinetics of seroconversion, and relative sparing of mucosal CD4+ T cells in the GI tract. CONCLUSIONS: Despite the failure of tenofovir DF/FTC as prophylaxis, selection for drug-resistant transmission did not occur and the blunting of postinfection levels of viremia likely reduced the probability of subsequent forward transmissions during the acute phase. These results support continued investigations of the use of antiretrovirals as a means to reduce HIV-1 transmission.

Role of virus receptor Hyal2 in oncogenic transformation of rodent fibroblasts by sheep betaretrovirus env proteins.

The ovine betaretroviruses jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV) cause contagious cancers in the lungs and upper airways of sheep and goats. Oncogenic transformation assays using mouse and rat fibroblasts have localized the transforming activity to the Env proteins encoded by these viruses, which require the putative lung and breast cancer tumor suppressor hyaluronidase 2 (Hyal2) to promote virus entry into cells. These results suggested the hypothesis that the JSRV and ENTV Env proteins cause cancer by inhibiting the tumor suppressor activity of Hyal2. Consistent with this hypothesis, we show that human Hyal2 and other Hyal2 orthologs that can promote virus entry, including rat Hyal2, can suppress transformation by the Env proteins of JSRV and ENTV. Furthermore, we provide direct evidence for binding of the surface (SU) region of JSRV Env to human and rat Hyal2. However, mouse Hyal2 did not mediate entry of virions bearing JSRV or ENTV Env proteins, bound JSRV SU poorly if at all, and did not suppress transformation by the JSRV or ENTV Env proteins, indicating that mouse Hyal2 plays no role in transformation of mouse fibroblasts and that the Env proteins can transform at least some cells by a Hyal2-independent mechanism. Expression of human Hyal2 in mouse cells expressing JSRV Env caused a marked reduction in Env protein levels, indicating that human Hyal2 suppresses Env-mediated transformation in mouse cells by increasing Env degradation rather than by exerting a more general Env-independent tumor suppressor activity.

Mechanism of cell entry and transformation by enzootic nasal tumor virus.

Enzootic nasal tumor virus (ENTV) induces nasal epithelial cancer in infected sheep, but it is a simple retrovirus lacking a known oncogene. ENTV is closely related to jaagsiekte sheep retrovirus (JSRV), which also causes cancer in sheep but in the epithelial cells of the lower airways and alveoli. Here we show that as with JSRV, the envelope (Env) protein of ENTV can transform cultured cells and thus is likely to be responsible for oncogenesis in animals. In addition, the ENTV Env protein mediates virus entry using the same receptor as does JSRV Env, the candidate tumor suppressor Hyal2. However, ENTV Env mediates entry into cells from a more restricted range of species than does JSRV, and based on this finding we have identified amino acid regions in the Env proteins that are important for virus entry. Also, because ENTV does not efficiently use human Hyal2 as a receptor, we cloned the ovine Hyal2 cDNA and show that the encoded protein functions as an efficient receptor for both ENTV and JSRV. In summary, although ENTV and JSRV use the same cell surface receptor for cell entry and apparently transform cells by the same mechanism, they induce cancer in different tissues of infected sheep, indicating that oncogenesis is regulated at some other level. The transcriptional regulatory elements in these viruses are quite different, indicating that tissue-specific oncogenesis is likely regulated at the level of viral gene expression.

Hyaluronidase 2 negatively regulates RON receptor tyrosine kinase and mediates transformation of epithelial cells by jaagsiekte sheep retrovirus.

The candidate tumor-suppressor gene hyaluronidase 2 (HYAL2) encodes a glycosylphosphatidylinositol-anchored cell-surface protein that serves as an entry receptor for jaagsiekte sheep retrovirus, a virus that causes contagious lung cancer in sheep that is morphologically similar to human bronchioloalveolar carcinoma. The viral envelope (Env) protein alone can transform cultured cells, and we hypothesized that Env could bind and sequester the HYAL2 receptor and thus liberate a potential oncogenic factor bound and negatively controlled by HYAL2. Here we show that the HYAL2 receptor protein is associated with the RON receptor tyrosine kinase (also called MST1R or Stk in the mouse), rendering it functionally silent. In human cells expressing a jaagsiekte sheep retrovirus Env transgene, the Env protein physically associates with HYAL2. RON liberated from the association with HYAL2 becomes functionally active and consequently activates the Akt and mitogen-activated protein kinase pathways leading to oncogenic transformation of immortalized human bronchial epithelial cells. We find activated RON in a subset of human bronchioloalveolar carcinoma tumors, suggesting RON involvement in this type of human lung cancer.

C to A single nucleotide polymorphism in intron 18 of the human MST1R (RON) gene that maps at 3p21.3.

The MST1R (RON) gene, that maps at 3p21.3, encodes a protein tyrosine kinase receptor comprised of an extra-cellular domain that contains the ligand binding pocket and an intracellular region where the kinase domain is located. It controls cell survival and motility programs related to invasive growth. With the single strand conformation polymorphism (SSCP) method, a C to A nucleotide polymorphism (SNP) was found in intron 18 of the gene. The SNP has a frequency of 0.28 among African-American, 0.25 among Caucasian CEPH and 0.09 among Asian healthy individuals. During these studies, an alternatively spliced cDNA of MST1R, lacking exon 19, was also found that may result from this change.

Characterization of a new SNP c767A/T (Arg222Trp) in the candidate TSG FUS2 on human chromosome 3p21.3: prevalence in Asian populations and analysis of association with nasopharyngeal cancer.

The FUS2 gene, encoding a novel cytoplasmic acetyltransferase, resides in the tumor suppressor gene region on human chromosome 3p21.3 and is considered a promising candidate tumor suppressor gene. We have identified a new single nucleotide polymorphism (SNP), c767A/T, in the coding region of the gene. The polymorphism leads to a non-conservative amino acid change (R222W) located between the acetyltransferase (GNAT) and the proline-rich domains of the protein. We have analyzed 254 subjects included in 14 sub-populations. The occurrence of the SNP varies with the ethnicity of the population, suggesting that this SNP could be a valuable biomarker for population genetics. It is most prevalent in various Asian populations (T allele frequency>0.54), followed by the Canadian polar Inuit (T allele frequency=0.3), African American (T allele frequency=0.17), and Caucasian population (T allele frequency=0.1). Since nasopharyngeal carcinoma (NPC) is frequent in Southern China, Taiwan, Borneo and polar Canada, we further tested for the possible association of the FUS2 SNP with this form of endemic cancer. Our analysis, albeit limited, suggests no likely association between NPC and the FUS2 gene polymorphism. Further large-scale case-control studies are necessary and warranted to prove the strength of this contention.