ABSTRACT
The novel coronavirus SARS-CoV-2 has caused a worldwide pandemic resulting in widespread efforts in development of animal models that recapitulate human disease for evaluation of medical countermeasures, and to dissect COVID-19 immunopathogenesis. We tested whether route of experimental infection substantially changes COVID-19 disease characteristics in two species (Macaca mulatta; rhesus macaques; RM, Chlorocebus atheiops; African green monkeys; AGM) of nonhuman primates. Species-specific cohorts of RM and AGM Rhesus macaques (Macaca mulatta, RMs) and African green monkeys (Chlorocebus aethiops, AGMs) were experimentally infected with homologous SARS-CoV-2 by either direct mucosal instillation or small particle aerosol in route-discrete subcohorts. Both species demonstrated equivalent infection initially by either exposure route although the magnitude and duration of viral loading was greater in AGMs than that of the RM. Clinical onset was nearly immediate (+1dpi) in mucosally-exposed cohorts whereas aerosol-infected animals began to show signs +7dpi. Myeloid cell responses indicative of the development of pulmonary scarring and extended lack of regenerative capacity in the pulmonary compartment was a conserved pathologic response in both species by either exposure modality. This pathological commonality may be useful in future anti-fibrosis therapeutic evaluations and expands our understanding of how SARS-CoV-2 infection leads to ARDS and functional lung damage.
ABSTRACT
In recent months, several SARS-CoV-2 variants have emerged that enhance transmissibility and escape host humoral immunity. Hence, the tracking of viral evolutionary trajectories is clearly of great importance. Little is known about SARS-CoV-2 evolution in nonhuman primate models used to test vaccines and therapies and to model human disease. Viral RNA was sequenced from rectal swabs from Chlorocebus aethiops (African green monkeys) after experimental respiratory SARS-CoV-2 infection. Two distinct patterns of viral evolution were identified that were shared between all collected samples. First, mutations in the furin cleavage site that were initially present in the virus as a consequence of VeroE6 cell culture adaptation were subsequently lost in virus recovered in rectal swabs, confirming the necessity of this motif for viral infection in vivo. Three amino acid changes were also identified; ORF 1a S2103F, and spike D215G and H655Y, that were detected in rectal swabs from all sampled animals. These findings are demonstrative of intra-host SARS-CoV-2 evolution unique to this nonhuman primate species and may identify a host-adapted variant of SARS-CoV-2 that would be useful in future development of primate disease models.
ABSTRACT
Coronavirus disease-19 (COVID-19) transmits by droplets generated from surfaces of airway mucus during processes of respiration within hosts infected by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) virus. We studied respiratory droplet generation and exhalation in human and nonhuman primate subjects with and without COVID-19 infection to explore whether SARS-CoV-2 infection, and other changes in physiological state, translates into observable evolution of numbers and sizes of exhaled respiratory droplets in healthy and diseased subjects. In our observational cohort study of the exhaled breath particles of 74 healthy human subjects, and in our experimental infection study of eight nonhuman primates infected by aerosol with SARS-CoV-2, we found that exhaled aerosol particles increase one to three orders of magnitude with aging, high BMI, and COVID-19 infection. These variances appear to be related to changes in airway mucus surface composition and the propensity for mucus surfaces to breakup into small droplets during acts of breathing. We also observed that 20% of those participating in our human study accounted for 80% of the overall exhaled bioaerosol, reflecting a bioaerosol distribution analogous to a classical 20:80 super spreader distribution.
