This study will identify and characterize immune factors involved in hepatitis C infection and elimination of the virus. Individual responses to hepatitis C infection vary; some people are able to eliminate the virus, whereas others remain chronically infected. This study may identify factors important in preventing infection that may be of help in developing a vaccine or more effective treatments.

People over 18 years old who have been exposed to hepatitis C virus may participate in this study. Subjects will be recruited from the National Institutes of Health, Inova Fairfax Hospital, Occupational Medical Services-IDP P.C., Washington Hospital Center and Holy Cross Hospital, all in the Washington, D.C. metropolitan area. Individual patients from other centers will also be recruited on a case by case basis.

Participants will have 40 to 60 cc (1 to 2 ounces) of blood drawn at seven intervals. The first collection will be as soon as possible after exposure to hepatitis C virus and then again at 2, 4, 6, 12, 24, and 48 weeks after exposure. The white blood cells will be studied for their response to the virus, and markers for infection will be followed. If infection develops, additional samples of blood may be requested, and patients will be offered evaluation for treatment. Test results will be kept confidential and will not be entered into any medical records.

The course and outcome of hepatitis C virus (HCV) infection is determined by both host and viral factors, none of which have been well defined. In this study, we will follow and assess patients who are occupationally exposed to HCV for viral and immunologic factors that may relate to disease outcome. This protocol is mostly a sample acquisition protocol to support laboratory research. Patients will be interviewed and have blood (and lymphocytes) taken as soon as possible after exposure and again after 2, 4, 6, 12, 24 and 48 weeks. Virological markers, serum antibodies and both CD4 and CD8 T cell responses to HCV will be monitored. Persons who develop hepatitis C will be referred for therapy or enrolled in therapeutic trials currently in place at the National Institutes of Health. These studies will help define the relative roles of virological and immunological factors in determining the course and outcome of HCV infection.

• INCLUSION CRITERIA:

Male or female;

All ethnic groups;

Age above 18 years;

Defined exposure to hepatitis C.

EXCLUSION CRITERIA:

Subjects with a Hct of less than 30.