Horizontal transmission of endemic viruses among rhesus macaques (Macaca mulatta): Implications for human cytomegalovirus vaccine/challenge design.

INTRODUCTION: Rhesus macaques are natural hosts to multiple viruses including rhesus cytomegalovirus (RhCMV), rhesus rhadinovirus (RRV), and Simian Foamy Virus (SFV). While viral infections are ubiquitous, viral transmissions to uninfected animals are incompletely defined. Management procedures of macaque colonies include cohorts that are Specific Pathogen Free (SPF). Greater understanding of viral transmission would augment SPF protocols. Moreover, vaccine/challenge studies of human viruses would be enhanced by leveraging transmission of macaque viruses to recapitulate expected challenges of human vaccine trials. MATERIALS AND METHODS: This study characterizes viral transmissions to uninfected animals following inadvertent introduction of RhCMV/RRV/SFV-infected adults to a cohort of uninfected juveniles. Following co-housing with virus-positive adults, juveniles were serially evaluated for viral infection. RESULTS: Horizontal viral transmission was rapid and absolute, reaching 100% penetrance between 19 and 78 weeks. CONCLUSIONS: This study provides insights into viral natural histories with implications for colony management and modeling vaccine-mediated immune protection studies.

Analysis of rhesus rhadinovirus microRNAs expressed in virus-induced tumors from infected rhesus macaques.

Rhesus rhadinovirus (RRV), a primate gamma-herpesvirus related to human Kaposi's sarcoma-associated herpesvirus (KSHV), causes a similar pattern of pathogenesis. Previously, RRV was shown to express 7 pre-microRNAs (pre-miRNAs) in latently infected cells. Using deep sequencing, we analyzed the pattern of small RNA expression in vivo using latently RRV-infected B-cell lymphoma and retroperitoneal fibromatosis tissues. We identified 15 virally encoded pre-miRNAs in both tumors, including all previously reported RRV pre-miRNAs. Although all 15 RRV pre-miRNAs, like all 12 KSHV pre-miRNAs, are located 3' to the conserved viral ORF71 gene and in the same transcriptional orientation, only one RRV miRNA is homologous to a KSHV miRNA. One previously identified RRV miRNA, miR-rR1-3, is actually a miRNA offset RNA (moRNA) derived from sequences located adjacent to pre-miR-rR1-3. Several other RRV-derived moRNAs were obtained, including one recovered >600 times. Together, this research provides a comprehensive list of the miRNAs and moRNAs encoded by RRV.

Multiple diagnostic techniques identify previously vaccinated individuals with protective immunity against monkeypox.

Approximately 50% of the US population received smallpox vaccinations before routine immunization ceased in 1972 for civilians and in 1990 for military personnel. Several studies have shown long-term immunity after smallpox vaccination, but skepticism remains as to whether this will translate into full protection against the onset of orthopoxvirus-induced disease. The US monkeypox outbreak of 2003 provided the opportunity to examine this issue. Using independent and internally validated diagnostic approaches with >or=95% sensitivity and >or=90% specificity for detecting clinical monkeypox infection, we identified three previously unreported cases of monkeypox in preimmune individuals at 13, 29 and 48 years after smallpox vaccination. These individuals were unaware that they had been infected because they were spared any recognizable disease symptoms. Together, this shows that the US monkeypox outbreak was larger than previously realized and, more importantly, shows that cross-protective antiviral immunity against West African monkeypox can potentially be maintained for decades after smallpox vaccination.

Duration of antiviral immunity after smallpox vaccination.

Although naturally occurring smallpox was eliminated through the efforts of the World Health Organization Global Eradication Program, it remains possible that smallpox could be intentionally released. Here we examine the magnitude and duration of antiviral immunity induced by one or more smallpox vaccinations. We found that more than 90% of volunteers vaccinated 25-75 years ago still maintain substantial humoral or cellular immunity (or both) against vaccinia, the virus used to vaccinate against smallpox. Antiviral antibody responses remained stable between 1-75 years after vaccination, whereas antiviral T-cell responses declined slowly, with a half-life of 8-15 years. If these levels of immunity are considered to be at least partially protective, then the morbidity and mortality associated with an intentional smallpox outbreak would be substantially reduced because of pre-existing immunity in a large number of previously vaccinated individuals.

Complete sequence and genomic analysis of rhesus cytomegalovirus.

The complete DNA sequence of rhesus cytomegalovirus (RhCMV) strain 68-1 was determined with the whole-genome shotgun approach on virion DNA. The RhCMV genome is 221,459 bp in length and possesses a 49% G+C base composition. The genome contains 230 potential open reading frames (ORFs) of 100 or more codons that are arranged colinearly with counterparts of previously sequenced betaherpesviruses such as human cytomegalovirus (HCMV). Of the 230 RhCMV ORFs, 138 (60%) are homologous to known HCMV proteins. The conserved ORFs include the structural, replicative, and transcriptional regulatory proteins, immune evasion elements, G protein-coupled receptors, and immunoglobulin homologues. Interestingly, the RhCMV genome also contains sequences with homology to cyclooxygenase-2, an enzyme associated with inflammatory processes. Closer examination identified a series of candidate exons with the capacity to encode a full-length cyclooxygenase-2 protein. Counterparts of cyclooxygenase-2 have not been found in other sequenced herpesviruses. The availability of the complete RhCMV sequence along with the ability to grow RhCMV in vitro will facilitate the construction of recombinant viral strains for identifying viral determinants of CMV pathogenicity in the experimentally infected rhesus macaque and to the development of CMV as a vaccine vector.