Innate Immunity and KSHV

DESCRIPTION (provided by applicant): KSHV is both a commensal and pathogenic microorganism in the human host. Many studies have shown that KSHV is present in the saliva and oral cavity and can be transmitted through both oral and sexual transmission routes. In healthy individuals with an intact immune system, KSHV is kept in check and normally does not cause disease. However, in conditions of immune suppression e.g. HIV infection or immunosuppressive therapy, KSHV is associated with the development of sarcomas and lymphomas, including in the oral cavity. Although these diseases are usually seen in the context of immune suppression, even healthy HIV-negative individuals can develop KSHV- associated cancers. Thus, it is clear that the host immune system plays a critical role in preventing diseases associated with KSHV infection. It is currently unclear how the immune system keeps KSHV in check in healthy individuals, but allows disease to progress during times of immunosuppresion. Toll-like receptors (TLRs) are a very important means by which the innate immune system recognizes microbial pathogens like KSHV. TLR activation requires a slew of intracellular players that play both positive and negative roles in the regulation of innate immunity in response to pathogens. TLRs are considered the first line of defense in innate immunity since they are located either on the cytoplasmic membrane or in endosomes and detect the invading pathogen. Additionally, NLR (nucleotide-binding domain leucine-rich repeat containing) and RLR (RIG-I-like receptors) are two other families of intracellular sensors that also play key roles in pathogen detection. Certain NLR proteins play central roles in the inflammasome, a molecular complex that is necessary for caspase-1 activation and subsequent IL-1b production. RLRs are involved in sensing the intracellular RNA transcripts of foreign pathogens. In the previous grant period, we reported that both TLRs and NLRs are capable of detecting KSHV in a variety of different biologically relevant cell types during primary infection and during reactivation from latency. In order to survive in the human host, we propose that KSHV must encode several immune modulators that blunt activation of the TLR, RLR, and NLR innate immune pathways. In this application, we propose to determine the various roles of TLRs, RLRs and NLRs in recognizing KSHV, as well as KSHV viral proteins that modulate these innate immune sensors and allow the virus to successfully establish life-long latency in the human host.