BACKGROUND:
Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) is a blood-borne virus that is etiologically associated with Kaposi's sarcoma (KS), primary effusion lymphoma which is a form of non-Hodgkin's lymphoma, and a subset of multicentric Castleman's disease which is a lymphoproliferative disorder. The investigators developed serologic assays to measure antibodies specific to KSHV latent and lytic antigens. Antibodies to KSHV antigens are found in 70-100 percent of all clinical forms of KS patients. In contrast, relatively low prevalence (2 to 5 percent) is found in the general population of North America. Seroconversion is detected prior to KS onset in AIDS-KS patients, suggesting that primary KSHV infection occurs predominantly in adulthood and is not ubiquitous. Antibody titers to KSHV antigens remain elevated for years after seroconversion. The investigators have recently found a 5 percent prevalence of KSHV infection in blood donors from San Antonio. Further, KSHV has been found in the peripheral blood mononuclear cells (PBMC) of blood donors, and organ transplantation and animal studies have provided evidence of likely person-to-person transmission of KSHV. Thus, KSHV is a potential candidate for screening in blood and plasma donors in view of its etiologic role for several malignancies, low but appreciable prevalence in the general population, and lifelong persistence in a cross-sectional study in blood donors from Texas.
DESIGN NARRATIVE:
The first aim of the study was to determine the prevalence of KSHV infection in blood donors using specific KSHV serologic assays. The investigators used recently developed KSHV specific serologic assays for detecting antibody to KSHV latent nuclear antigen, lytic antigen, and orf65 (lytic antigen minor capsid protein) to determine the prevalence of KSHV infection in a cross-sectional study of four representative blood banks in San Antonio, Dallas, and Houston, Texas. A total of 500 random donors at each site were studied to detect site-specific seroprevalence to plus or minus 2 percent with 95 percent confidence.
The second aim of the study was to analyze the demographic characteristics and the patterns of other blood-borne infections of KSHV-seropositive blood donors. The cross-sectional study in Houston and San Antonio was expanded to prospective study seroprevalence in a larger population with questionnaire obtained demographic data to include gender, age, ethnicity, education level, household income, and zip code. A total of 10,500 donors were obtained from Houston. As the San Antonio center had the highest proportion of Hispanic donors, an additional 2,000 donors were obtained and characterized demographically.
The third aim was to investigate KSHV molecular epidemiology in blood donors through sequence determination of specific nested-polymerase chain reaction (PCR) and RT-PCR products from peripheral blood mononuclear cells (PBMC) of KSHV-seropositive donors. The 2,000 blood samples from San Antonio were also used to amplify KSHV sequences from peripheral blood mononuclear cells of KSHV positive donors using PCR, nested PCR and RT-PCR with and without phorbol ester induction. Sequencing of amplified products was compared to KSHV isolates from New York, Italy, England, and Africa for phylogenetic analysis and assessment of diversity and distribution of KSHV strains in Texas. While the proposed sampling represented only one center in Texas, comparison to isolates for New York and abroad allowed determination of the likelihood that Texas strains were unique or imported from Europe or Africa.
This regional project was performed in collaboration with the University Health System Donor Center in San Antonio, BloodCare in Dallas, and Gulf Coast Regional Blood Center in Houston, thus providing results for three separate metropolitan areas with rather different ethnic compositions. These studies should provide valuable information to assess the necessity and feasibility of national screening of blood donors for KSHV, and gain insight into the patterns of infection as well as the diversity, the distribution, and the origins of the virus strains in blood donors.
