Development of a coronavirus disease 2019 nonhuman primate model using airborne exposure.

Airborne transmission is predicted to be a prevalent route of human exposure with SARS-CoV-2. Aside from African green monkeys, nonhuman primate models that replicate airborne transmission of SARS-CoV-2 have not been investigated. A comparative evaluation of COVID-19 in African green monkeys, rhesus macaques, and cynomolgus macaques following airborne exposure to SARS-CoV-2 was performed to determine critical disease parameters associated with disease progression, and establish correlations between primate and human COVID-19. Respiratory abnormalities and viral shedding were noted for all animals, indicating successful infection. Cynomolgus macaques developed fever, and thrombocytopenia was measured for African green monkeys and rhesus macaques. Type II pneumocyte hyperplasia and alveolar fibrosis were more frequently observed in lung tissue from cynomolgus macaques and African green monkeys. The data indicate that, in addition to African green monkeys, macaques can be successfully infected by airborne SARS-CoV-2, providing viable macaque natural transmission models for medical countermeasure evaluation.

Validation of a pan-orthopox real-time PCR assay for the detection and quantification of viral genomes from nonhuman primate blood.

BACKGROUND: In 1980, smallpox disease was eradicated from nature and Variola virus, the etiological agent of smallpox, was confined to two laboratories, one located in Russia (Moscow) later moved to VECTOR (Novosibirsk, Siberia) and one in the United States (CDC Atlanta). Vaccinations among the general public ceased shortly after the successful eradication campaign, resulting in an increasingly immunologically susceptible population. Because of the possibility of intentional reintroduction of Variola virus and the emergence of other pathogenic poxviruses, there is a great need for the development of medical countermeasures to treat poxvirus disease. It is highly likely that the U.S. FDA "animal rule" will be necessary for regulatory approval of these interventions. Therefore, relevant animal models and the associated supporting assays will require development to stand up to regulatory scrutiny. METHODS: An optimized real time PCR assay for the detection of orthopoxviruses has been developed by researchers at the United States Army Research Institute of Infectious Diseases (USAMRIID). To support animal studies that will be used to support approval of medical countermeasures by the U.S. FDA, the assay was designed to quantitate poxvirus genomic DNA in a nonhuman primate (cynomolgus macaque) blood matrix as a measurement of viremia. This manuscript describes the validation of the process, including DNA extraction from whole blood anticoagulated with EDTA, for obtaining and quantitating monkeypox genomes by evaluating precision, accuracy, the standard curve, specificity, robustness and stability of the assay and/or components of the assay. RESULTS: The assay had a lower limit of quantitation of 50 genome copies/5 uL sample, upper limit of quantitation of 5 × 107 GC/5uL sample and a limit of detection of 2.5 genome copies /5uL sample. The assay was specific for orthopoxvirus. Matrix effects were detected and suggest the presence of PCR inhibitor(s) that was co-extracted with the target DNA. CONCLUSIONS: The assay has been validated for the purpose of quantitating monkeypox viral load in blood from cynomolgus macaques. This assay has and will continue to support submissions to the FDA for approval of antiviral therapeutics for smallpox.

Modelling hepatitis C virus incidence, prevalence and long-term sequelae in Australia, 2001.

BACKGROUND: To plan an appropriate public health response to the hepatitis C virus (HCV) epidemic requires that estimates of HCV incidence and prevalence, and projections of the long-term sequelae of infection, are as accurate as possible. In this paper, mathematical models are used to synthesize data on the epidemiology and natural history of HCV in Australia to estimate HCV incidence and prevalence in Australia to end 2001, and project future trends in the long-term sequelae of HCV infection. METHODS: Mathematical models of the HCV epidemic in Australia were developed based on estimates of the pattern of injecting drug use. Estimates of HCV infections due to injecting drug use were then adjusted to allow for HCV infections resulting from other transmission routes. Projections of the long-term sequelae of HCV infection were obtained by combining modelled HCV incidence with estimates of the progression rates to these outcomes. RESULTS: It was estimated that there were 210 000 (lower and upper limits of 157 000 and 252 000) people in Australia living with HCV antibodies at the end of 2001, with HCV incidence in 2001 estimated to be 16 000 (11 000-19 000). It was estimated that 6500 (5000-8000) people were living with HCV-related cirrhosis in 2001, that 175 (130-210) people developed HCV-associated liver failure, and that there were 50 (40-60) incident cases of HCV-related hepatocellular carcinoma (HCC). It was estimated that in 2001 22 500 quality adjusted life years were lost to chronic HCV infection, the majority (77%) in people with early (stage 0/1) liver disease. DISCUSSION: Model-based estimates were broadly consistent with other sources of information on the HCV epidemic in Australia. These models suggest that the prevalence of HCV-related cirrhosis and the incidence of HCV-related liver failure and HCC will more than triple in Australia by 2020.