Establishment of an immortal cynomolgus macaque fibroblast cell line for propagation of cynomolgus macaque cytomegalovirus (CyCMV)

Evolution and Genetic Diversity of Primate Cytomegaloviruses

Cytomegaloviruses (CMVs) infect many mammals, including humans and non-human primates (NHPs). Human cytomegalovirus (HCMV) is an important opportunistic pathogen among immunocompromised patients and represents the most common infectious cause of birth defects. HCMV possesses a large genome and very high genetic diversity. NHP-infecting CMVs share with HCMV a similar genomic organization and coding content, as well as the course of viral infection. Recent technological advances have allowed the sequencing of several HCMV strains from clinical samples and provided insight into the diversity of NHP-infecting CMVs. The emerging picture indicates that, with the exclusion of core genes (genes that have orthologs in all herpesviruses), CMV genomes are relatively plastic and diverse in terms of gene content, both at the inter- and at the intra-species level. Such variability most likely underlies the strict species-specificity of these viruses, as well as their ability to persist lifelong and with relatively little damage to their hosts. However, core genes, despite their strong conservation, also represented a target of adaptive evolution and subtle changes in their coding sequence contributed to CMV adaptation to different hosts. Indubitably, important knowledge gaps remain, the most relevant of which concerns the role of viral genetics in HCMV-associated human disease.

Examining the species-specificity of rhesus macaque cytomegalovirus (RhCMV) in cynomolgus macaques

Cytomegalovirus (CMV) is a highly species-specific virus that has co-evolved with its host over millions of years and thus restricting cross-species infection. To examine the extent to which host restriction may prevent cross-species research between closely related non-human primates, we evaluated experimental infection of cynomolgus macaques with a recombinant rhesus macaque-derived CMV (RhCMV-eGFP). Twelve cynomolgus macaques were randomly allocated to three groups: one experimental group (RhCMV-eGFP) and two control groups (UV-inactivated RhCMV-eGFP or media alone). The animals were given two subcutaneous inoculations at week 0 and week 8, and a subset of animals received an intravenous inoculation at week 23. No overt clinical or haematological changes were observed and PBMCs isolated from RhCMV-eGFP inoculated animals had comparable eGFP- and IE-1-specific cellular responses to the control animals. Following inoculation with RhCMV-eGFP, we were unable to detect evidence of infection in any blood or tissue samples up to 4 years post-inoculation, using sensitive viral co-culture, qPCR, and Western blot assays. Co-culture of urine and saliva samples demonstrated the presence of endogenous cynomolgus CMV (CyCMV) cytopathic effect, however no concomitant eGFP expression was observed. The absence of detectable RhCMV-eGFP suggests that the CyCMV-seropositive cynomolgus macaques were not productively infected with RhCMV-eGFP under these inoculation conditions. In a continued effort to develop CMV as a viral vector for an HIV/SIV vaccine, these studies demonstrate that CMV is highly restricted to its host species and can be highly affected by laboratory cell culture. Consideration of the differences between lab-adapted and primary viruses with respect to species range and cell tropism should be a priority in evaluating CMV as vaccine vector for HIV or other pathogens at the preclinical development stage.