The Role of Cell-Specific Tropism in the Pathogenesis of Rhesus Cytomegalovirus Infection

The 40-year quest for a vaccine against human cytomegalovirus (HCMV) infection has been partially met by targeting the major envelope glycoprotein B (gB). However, the complex natural history of HCMV and the virus ability to infect a wide range of host cell types illustrate the central role cellular tropism plays in HCMV pathogenesis and emphasize the need for a vaccine that targets additional viral determinants of cellular tropism. Multiple genes located within the UL/b' region (UL128-UL154) of the HCMV genome have been implicated in regulating virus entry into epithelial and endothelial cells and modulating several host immune responses mounted against HCMV infection. We utilized virological, histopathological, and epidemiological tools to characterize the relationship between rhesus cytomegalovirus (RhCMV) cellular tropism and the pattern of viral infection in vivo and illustrated the potential of targeting products of genes within the UL/b' region in future vaccine developments. To address this, we inoculated rhesus macaques with three RhCMV strains that vary in their UL/b' coding content. RhCMV UCD52 and UCD59 encode a full complement of open reading frames (ORF) in the UL/b' region; RhCMV 68-1 lacks the UL128 complex essential for endothelial/epithelial tropism, and alpha-chemokine-like ORFs; and RhCMV 180.92 tropic for endothelial/epithelial cells but lacks viral determinants of host immune evasion. Two histopathological hallmarks were observed with the acute infection with RhCMV UCD52 and UCD59 strains: neutrophilic inflammation and infected endothelial cells, both of which were observed during recurrent RhCMV disease in animals coinfected with wild-type RhCMV and simian immunodeficiency virus (SIV). In contrast, animals inoculated with RhCMV 68-1 were noted for an absence of neutrophilic infiltrates and infected endothelial cells, demonstrating the role of UL128 complex in epithelial/endothelial tropism in vivo and further suggest that the long-term pattern of viral infection is determined in large part by the earliest virus-host interactions. Further investigations using RhCMV 180.92 demonstrated lower levels of plasma viremia, limited systemic dissemination, low levels of tissue virus titers, and absent or low level of viral shedding in urine and saliva, compared to the in vivo pattern of a minor RhCMV 180.92 variant present in the virus stock potentially carrying the full complement of UL/b' region. These results demonstrate the possibility that other ORFs, independent of UL128 complex, within the UL/b' region may determine in vivo viral replication, dissemination, and shedding of RhCMV. Finally, RhCMV neuromuscular disease was identified in 10.5% of all SIV-infected animals and 6% demonstrated direct RhCMV infection of skeletal muscles. HCMV has been implicated by association in the pathogenesis of HIV-associated myopathies. However, in vivo studies failed to demonstrate a direct evidence of HCMV infection of skeletal muscle cells. Our results indicate that RhCMV is linked to skeletal myositis and suggest that human HCMV may be a causative agent for similar pathologies in HIV-infected humans

Limited Dissemination and Shedding of the UL128 Complex-Intact, UL/b′-Defective Rhesus Cytomegalovirus Strain 180.92

UnlabelledThe UL128 complex of human cytomegalovirus (CMV) is a major determinant of viral entry into epithelial and endothelial cells and a target for vaccine development. The UL/b' region of rhesus CMV contains several open reading frames, including orthologs of the UL128 complex. We recently showed that the coding content of the rhesus CMV (RhCMV) UL/b' region predicts acute endothelial tropism and long-term shedding in vivo in the rhesus macaque model of CMV infection. The laboratory-passaged RhCMV 180.92 strain has a truncated UL/b' region but an intact UL128 complex. To investigate whether the presence of the UL128 complex alone was sufficient to confer endothelial and epithelial tropism in vivo, we investigated tissue dissemination and viral excretion following experimental RhCMV 180.92 inoculation of RhCMV-seronegative rhesus macaques. We show the presence of at least two virus variants in the RhCMV 180.92 infectious virus stock. A rare variant noted for a nontruncated wild-type-virus-like UL/b' region, rapidly emerged during in vivo replication and showed high-level replication in blood and tissues and excretion in urine and saliva, features similar to those previously reported in naturally occurring wild-type RhCMV infection. In contrast, the predominant truncated version of RhCMV 180.92 showed significantly lower plasma DNAemia and limited tissue dissemination and viral shedding. These data demonstrate that the truncated RhCMV 180.92 variant is attenuated in vivo and suggest that additional UL/b' genes, besides the UL128 complex, are required for optimal in vivo CMV replication and dissemination.ImportanceAn effective vaccine against human CMV infection will need to target genes that are essential for virus propagation and transmission. The human CMV UL128 complex represents one such candidate antigen since it is essential for endothelial and epithelial cell tropism, and is a target for neutralizing antibodies in CMV-infected individuals. In this study, we used the rhesus macaque animal model of CMV infection to investigate the in vivo function of the UL128 complex. Using experimental infection of rhesus macaques with a rhesus CMV virus variant that contained an intact UL128 complex but was missing several other genes, we show that the presence of the UL128 complex alone is not sufficient for widespread tissue dissemination and virus excretion. These data highlight the importance of in vivo studies in evaluating human CMV gene function and suggest that additional UL/b' genes are required for optimal CMV dissemination and transmission

Meeting report: Spontaneous Lesions and Diseases in Wild, Captive-Bred, and Zoo-Housed Nonhuman Primates and in Nonhuman Primate Species Used for Drug Safety Studies

The combination of loss of habitat, human population encroachment, and increased demand of select species for biomedical research has expanded the list of emerging diseases. There remains a need for knowledge and expertise in understanding background findings as related to the age, source, strain, and disease status of nonhuman primates. In particular, for safety/biomedical studies, a broader understanding and documentation of lesions would help clarify background from treatment related findings. A workshop and mini-symposium on spontaneous lesions and diseases in nonhuman primates were sponsored by the concurrent Annual Meetings of the American College of Veterinary Pathologists and the American Society for Veterinary Clinical Pathology held December 3-4, 2011 in Nashville, TN. The first session had presentations from Drs. Linda Lowenstine and Richard Montali, pathologists with extensive experience in wild and zoo populations of nonhuman primates, which was followed by presentations of 20 unique case studies of rare or newly observed spontaneous lesions in nonhuman primate species. The mini-symposium concentrated on background and spontaneous lesions in nonhuman primate species used for drug safety studies, and included presentations on incidence and range of spontaneous findings in cynomolgus macaques; lesions in the urogenital system of macaques; gastrointestinal lesions and pathogens in macaques and marmosets; age-associated lesions in rhesus macaques; and effects of Plasmodium infection on drug development. Both sessions were heavily attended by meeting participants that included students, pathology trainees, and experienced pathologists from academia and industry with an interest in spontaneous diseases of nonhuman primates

The first 2 months of the SARS-CoV-2 epidemic in Yemen: Analysis of the surveillance data.

IntroductionYemen was one of the last countries in the world to declare the first case of the pandemic, on 10 April 2020. Fear and concerns of catastrophic outcomes of the epidemic in Yemen were immediately raised, as the country is facing a complex humanitarian crisis. The purpose of this report is to describe the epidemiological situation in Yemen during the first 2 months of the SARS-CoV-2 epidemic.MethodsWe analyzed the epidemiological data from 18 February to 05 June 2020, including the 2 months before the confirmation of the first case. We included in our analysis the data from 10 out of 23 governorates of Yemen, located in southern and eastern part of the country.ResultsA total of 469 laboratory confirmed, 552 probable and 55 suspected cases with onset of symptoms between 18 February and 5 June 2020 were reported through the surveillance system. The median age among confirmed cases was 46 years (range: 1-90 years), and 75% of the confirmed cases were male. A total of 111 deaths were reported among those with confirmed infection. The mean age among those who died was 53 years (range: 14-88 years), with 63% of deaths (n = 70) occurring in individuals under the age 60 years. A total of 268 individuals with confirmed SARS-CoV-2 infection were hospitalized (57%), among whom there were 95 in-hospital deaths.ConclusionsThe surveillance strategy implemented in the first 2 months of the SARS CoV 2 in the southern and eastern governorates of Yemen, captured mainly severe cases. The mild and moderate cases were not self-reported to the health facilities and surveillance system due to limited resources, stigma, and other barriers. The mortality appeared to be higher in individuals aged under 60 years, and most fatalities occurred in individuals who were in critical condition when they reached the health facilities. It is unclear whether the presence of other acute comorbidities contributed to the high death rate among SARS-CoV-2 cases. The findings only include the southern and eastern part of the country, which is home to 31% of the total population of Yemen, as the data from the northern part of the country was inaccessible for analysis. This makes our results not generalizable to the rest of the country