Cytomegalovirus (CMV) infects a large percentage of the world's population. Most of those infected are asymptomatic; however, CMV is a substantial public health concern for immunocompromised individuals and neonates. CMV is unusual in that it can superinfect: It reinfects hosts who are already infected with the virus, even in the presence of a strong, specific immune response. Hansen et al. (see the Perspective by Hengel and Koszinowski) now find that in rhesus macaques, a good model for human CMV superinfection, CMV establishes superinfections by evading the immune response mediated by CD8+ T cells. A series of viral mutants deficient in expression of the US2-11 glycoproteins, which regulate antigen presentation to CD8+ T cells, revealed that, although able to establish the initial infection, these viral mutants were unable to superinfect. Depletion of CD8+ T cells from the monkeys allowed infection by the mutant viruses. These results highlight the difficulties in developing an effective protective vaccine against CMV itself but suggest that CMV-based vectors may be useful in other vaccine efforts, such as those against HIV.
S. G. Hansen, C. J. Powers, R. Richards, A. B. Ventura, J. C. Ford, D. Siess, M. K. Axthelm, J. A. Nelson, M. A. Jarvis, L. J. Picker, K. Früh, Evasion of CD8+ T cells is critical for superinfection by cytomegalovirus. Science 328, 102–106 (2010). [Abstract] [Full Text]