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Infection with human and simian immunodeficiency viruses (HIV/SIV) requires binding of the viral envelope glycoprotein (Env) to the host protein CD4 on the surface of immune cells. Although invariant in humans, the Env binding domain of the chimpanzee CD4 is highly polymorphic, with nine coding variants circulating in wild populations. Here, we show that within-species CD4 diversity is not unique to chimpanzees but found in many African primate species. Characterizing the outermost (D1) domain of the CD4 protein in over 500 monkeys and apes, we found polymorphic residues in 24 of 29 primate species, with as many as 11 different coding variants identified within a single species. D1 domain amino acid replacements affected SIV Env-mediated cell entry in a single-round infection assay, restricting infection in a strain- and allele-specific fashion. Several identical CD4 polymorphisms, including the addition of N-linked glycosylation sites, were found in primate species from different genera, providing striking examples of parallel evolution. Moreover, seven different guenons (Cercopithecus spp.) shared multiple distinct D1 domain variants, pointing to long-term trans-specific polymorphism. These data indicate that the HIV/SIV Env binding region of the primate CD4 protein is highly variable, both within and between species, and suggest that this diversity has been maintained by balancing selection for millions of years, at least in part to confer protection against primate lentiviruses. Although long-term SIV-infected species have evolved specific mechanisms to avoid disease progression, primate lentiviruses are intrinsically pathogenic and have left their mark on the host genome. [ABSTRACT FROM AUTHOR]

The Alphaherpesvirinae subfamily includes HSV types 1 and 2 and the sequence-divergent pathogen varicella zoster virus (VZV). T cells, controlled by TCR and HLA molecules that tolerate limited epitope amino acid variation, might cross-react between these microbes. We show that memory PBMC expansion with either HSV or VZV enriches for CD4 T cell lines that recognize the other agent at the whole-virus, protein, and peptide levels, consistent with bidirectional cross-reactivity. HSV-specific CD4 T cells recovered from HSV-seronegative persons can be explained, in part, by such VZV cross-reactivity. HSV-1-reaetive CD8 T cells also cross-react with VZV-infected cells, full-length VZV proteins, and VZV peptides, as well as kill VZV-infected dermal fibroblasts. Mono- and cross-reactive CD8 T cells use distinct TCRB CDR3 sequences. Cross-reactivity to VZV is reconstituted by cloning and expressing TCRA7TCRB receptors from T cells that are initially isolated using HSV reagents. Overall, we define 13 novel CD4 and CD8 HSV-VZV cross-reactive epitopes and strongly imply additional cross-reactive peptide sets. Viral proteins can harbor both CD4 and CD8 HSV/VZV cross-reactive epitopes. Quantitative estimates of HSV/VZV cross-reactivity for both CD4 and CD8 T cells vary from 10 to 50%. Based on these findings, we hypothesize that host herpesvirus immune historv may influence the pathogenesis and clinical outcome of subsequent infections or vaccinations for related pathogens and that cross-reactive epitopes and TCRs may be useful for multi-alphaherpesvirus vaccine design and adoptive cellular therapy. [ABSTRACT FROM AUTHOR]