Molecular Characterization of ORF M43 of Murine CMV

Sean Umamoto, University of California, Berkeley
Basic-Applied Clinical

Human cytomegalovirus (HCMV) is one of the most frequent opportunistic infections of patients with advanced HIV infection. Patients usually develop HCMV- associated diseases, which may include retinitis, pneumonia, general gastrointestinal diseases, central nervous system complications, and oral ulcers and lesions. Understanding the biology of cytomegalovirus infection and transmission is essential to develop new strategies for treatment and prevention of CMV-associated diseases.

One of the most important hallmarks of cytomegalovirus pathogenesis is its ability to infect and replicate in salivary gland. Salivary glands are a major source of persistent virus and have been shown to be a site for CMV latent infections. Viruses in saliva that are shed from infected salivary glands are believed to be one of the major sources for oral infections as well as for horizontal transmission. However, little is currently known about the mechanism of how the virus infects and replicates in salivary gland. Equally elusive are the identity of the viral determinants responsible for infection in the salivary gland and the mechanism of how they support viral infection and replication in the organ.

Using murine cytomegalovirus (MCMV) as a model system, my dissertation research proposed here is to investigate the function of MCMV open reading frame M43 in viral infection of salivary gland. Our laboratory has recently shown that MCMV mutants with deletion and truncation of M43 coding sequence replicated in vitro as well as the wild type virus. Moreover, when inoculated into immunocompetent Balb/c mice and immunocompromised SCID mice, these mutants replicated equally well in spleens, livers, lungs, and kidneys of the animals as the wild type virus. In contrast, they are significantly attenuated in growth in the salivary glands and salivary gland-derived cells. These results suggest that M43 encodes a viral determinant specifically responsible for cytomegalovirus infection and replication in salivary gland.

In this dissertation research, I will initially study the mRNA and protein expression of M43 and attempt to characterize cellular proteins that potentially interact with M43. Furthermore, I will examine the lytic replication cycle of the M43- inactivating mutants and to investigate how the mutants are deficient in growth in salivary gland-derived cells. The overall objective is to investigate the function of M43 in supporting viral infection and replication in salivary gland. These results are important to our understanding of cytomegalovirus infection and transmission, and should facilitate the development of novel approaches for treating and preventing HCMV infection, which is ubiquitous among AIDS patients in California and the United States.