Search

The most abundantly produced virion protein in human cytomegalovirus (HCMV) is the immunodominant phosphoprotein 65 (pp65), which is frequently included in CMV vaccines. Although it is nonessential for in vitro CMV growth, pp65 displays immunomodulatory functions that support a potential role in primary and/or persistent infection. To determine the contribution of pp65 to CMV infection and immunity, we generated a rhesus CMV lacking both pp65 orthologs (RhCMVΔpp65ab). While deletion of pp65ab slightly reduced growth in vitro and increased defective particle formation, the protein composition of secreted virions was largely unchanged. Interestingly, pp65 was not required for primary and persistent infection in animals. Immune responses induced by RhCMVΔpp65ab did not prevent reinfection with rhesus CMV; however, reinfection with RhCMVΔUS2-11, which lacks viral-encoded MHC-I antigen presentation inhibitors, was prevented. Unexpectedly, induction of pp65b-specific T cells alone did not protect against RhCMVΔUS2-11 challenge, suggesting that T cells targeting multiple CMV antigens are required for protection. However, pp65-specific immunity was crucial for controlling viral dissemination during primary infection, as indicated by the marked increase of RhCMVΔpp65ab genome copies in CMV-naive, but not CMV-immune, animals. Our data provide rationale for inclusion of pp65 into CMV vaccines but also demonstrate that pp65-induced T cell responses alone do not recapitulate the protective effect of natural infection., Introduction Human cytomegalovirus (HCMV) persistently infects most of humanity (1). While the vast majority of these infections are asymptomatic and not associated with any pathologic consequence, HCMV can cause serious [...]

IFN-gamma is an important Th1 proinflammatory cytokine and has a paradoxical effect on EAE in which disease susceptibility is unexpectedly heightened in IFN-gamma-deficient mice. In this study, we provide what we believe is new evidence indicating that IFN-gamma is critically required for the conversion of CD4+ CD25- T cells to CD4+ Tregs during EAE. In our study, the added severity of EAE in IFN-gamma knockout mice was directly associated with altered encephalitogenic T cell responses, which correlated with reduced frequency and function of CD4+ CD25+ Foxp3+ Tregs when compared with those of WT mice. It was demonstrated in both human and mouse systems that in vitro IFN-gamma treatment of CD4+ CD25- T cells led to conversion of CD4+ Tregs as characterized by increased expression of Foxp3 and enhanced regulatory function. Mouse CD4+ CD25- T cells, when treated in vitro with IFN-gamma, acquired marked regulatory properties as evidenced by suppression of EAE by adoptive transfer. These findings have important implications for the understanding of the complex role of IFN-gamma in both induction and self regulation of inflammatory processes. [ABSTRACT FROM AUTHOR]