Immune evasion proteins of human cytomegalovirus do not prevent a diverse CD8+ cytotoxic T-cell response in natural infection.

Although cytomegalovirus (CMV) expresses proteins that interfere with antigen presentation by class I major histocompatibility complex (MHC) molecules, CD8+ cytotoxic T cells (CTLs) are indispensable for controlling infection and maintaining latency. Here, a cytokine flow cytometry assay that employs fibroblasts infected with a mutant strain of CMV (RV798), which is deleted of the 4 viral genes that are responsible for interfering with class I MHC presentation, was used to examine the frequency and specificity of the CD8+ CTLs to CMV in immunocompetent CMV-seropositive individuals. A large fraction of the CD8+ CTL response was found to be specific for viral antigens expressed during the immediate early and early phases of virus replication and presented by fibroblasts infected with RV798 but not wild-type CMV. These results demonstrate that the inhibition of class I antigen presentation observed in CMV-infected cells in vitro is not sufficient to prevent the induction of a broad repertoire of CD8+ CTLs after natural infection in vivo. Thus, reconstitution of T-cell immunity in immunodeficient patients by cell therapy or by vaccination may need to target multiple viral antigens to completely restore immunologic control of CMV.

Selectively reduced tat mRNA heralds the decline in productive human immunodeficiency virus type 1 infection in monocyte-derived macrophages.

The transcription and splicing of human immunodeficiency virus type 1 (HIV-1) mRNA in primary blood monocyte-derived macrophages (MDM) and CD4(+) peripheral blood lymphocytes (PBL) were compared to determine whether any differences might account for the slower noncytopathic infection of cells of the macrophage lineage. The expression of regulatory mRNAs during acute infection of MDM was delayed by about 12 h compared to that of PBL. In each cell type, an increase in spliced viral mRNAs slightly preceded virus production from the culture. Following the peak of productive infection, there was a proportional decrease in the expression of all regulatory mRNAs detected in PBL. In MDM, a dramatic additional decrease specifically in the tat mRNA species heralded a reduction in virus production. This decline in tat mRNA was reflected by a concomitant decrease in Tat activity in the cells and occurred with the same kinetics irrespective of the age of the cells when infected. Addition of exogenous Tat protein elicited a burst of virus production from persistently infected MDM, suggesting that the decrease in virus production from the cultures is a consequence of the reduction in tat mRNA levels. Our results show that modulation of HIV-1 mRNAs in macrophages during long-term infection, which is dependent on the period of infection rather than cell differentiation or maturation, results in a selective reduction of Tat protein levels at the commencement of a persistent, less productive phase of infection. Determination of the mechanism of this mRNA modulation may lead to novel targets for control of replication in these important viral reservoirs.

Association between immune recovery uveitis and a diverse intraocular cytomegalovirus-specific cytotoxic T cell response.

Cytomegalovirus (CMV) causes serious infection in individuals with deficient T cell immunity. In acquired immunodeficiency syndrome, the retina is a major site of progressive infection, despite the availability of therapy that targets CMV. The administration of highly active antiretroviral therapy to suppress human immunodeficiency virus frequently results in resolution of CMV retinitis, but this may be complicated by ocular inflammation termed "immune recovery uveitis" (IRU). To provide insight into the pathogenesis of IRU, the phenotype and specificity of intraocular T cells in a single patient were analyzed. The T cell infiltrate consisted of a diverse population of CD8(+) CMV-specific T cells, but only a minority of these T cells recognized the CMV phosphoprotein 65 and immediate early protein 1, which have been considered major targets of the host response. These results imply that reconstitution of CMV-specific T cells plays a role in IRU and suggest that the specificity of T cells engaged in the control of CMV at local sites of reactivation may be broad.