Evasion of CD8 + T Cells Is Critical for Superinfection by Cytomegalovirus

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Abstract
Cytomegalovirus Immune Evasion Strategy: 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 re-infects hosts who are already infected with the virus, even in the presence of a strong, specific immune response. Hansen et al. (p. 102 ; 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.