The human γ-herpesviruses Epstein–Barr virus (EBV) and Kaposi's sarcoma herpesvirus (KSHV) establish latency in cellular reservoirs that are maintained for the life of the infected individual. Intermittent reactivation leads to infection of new cells within the host and secretion of virions in saliva. Primary infections are usually asymptomatic. However, in immunocompromised patients and in other special but poorly understood circumstances, tumors and other virus-associated diseases may manifest. Both human γ-herpesviruses were first identified in tumors and primary effusion lymphomas are typically dually infected (Cesarman et al., 1995; Chang et al., 1994; Epstein, 2001). For all their similarities, however, there are also striking differences between the viruses. EBV is nearly ubiquitous whereas KSHV is restricted to particular populations. EBV is most commonly associated with B-, T- and NK-cell tumors and epithelial tumors, whereas KSHV is associated with endothelial and B-cell tumors. In this chapter, aspects of virus–disease associations and therapies will be explored.
EBV
Transmission of EBV generally involves oral contact (Cohen, 2000). This might occur through the maternal chewing of food for young infants such as occurs in some cultures, the sharing of eating utensils, or kissing (Niederman et al., 1976). Infection may also occur through genital transmission, blood transfusion, and organ or bone marrow transplantation (Crawford et al., 2002). By adulthood more than 90% of adults show serologic evidence of EBV infection.