Genetic Susceptibility to Oncogenic Viruses

An NCI goal is to identify every human gene that predisposes people to cancer. Recent studies of HIV -1 indicate that genetic polymorphisms can affect susceptibility to viral infections and that such alleles may be detected in studies of small numbers of highly exposed-uninfected subjects. Because such alleles may be racially restricted, a range of racial and ethnic groups should be included in such studies. We propose to examine genetic determinants of infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) in an ethnically diverse population of injection drug users (lDUs). HBV and HCV are important causes of hepatocellular carcinoma, but little is known about genetic factors that alter susceptibility to these infections. Subjects will be recruited in diverse inner-city neighborhoods as part of the University of California, San Francisco's Urban Health Study. Since 1986, this study has successfully recruited and evaluated IDUs from street-based settings. About half of the participants are African-American, one-third are white, 10% are Latino, and the remainder are Asian or Native American. The mean duration of drug use exceeds 20 years. About 80% of subjects have evidence of HBV infection and a similar prevalence of HCV infection is anticipated. We will enroll about 1500 subjects over a 13 month period. Archived, unlinked serum specimens may obtained from previous enrollees to increase the sample size, as needed. Highly exposed-uninfected subjects will be ascertained on the basis of the serologic testing for each virus, as well as the duration and frequency of injection drug use. These highly exposed-uninfected subjects will be compared to infected subjects with regard to their frequency of genetic polymorphisms (chemokines, chemokine receptors, human leukocyte antigens, and others), in collaboration with scientists from NCI's Laboratory of Genomic Diversity.