Nonhuman Primate Model of Long Covid: Immune Insights of Glycometabolic Dysfunctions

Background: A major consequence of COVID-19 is long-term metabolic complications (metabolic PASC or Long COVID) following acute disease resolution leading to hyperglycemia, increased risk of diabetes or defects in glucose metabolism. However, the mechanisms underlying the links between COVID-19 and glycometabolic disruptions remain unclear. Method(s): 15 African green monkeys (AGM;Chlorocebus aethiops) were infected with SARS-CoV-2 (Wuhan stain) and divided into two groups: unvaccinated (n=10) and vaccinated (BNT162b2 (Pfizer) 4-days post infection;n=5). Subgenomic SARS-CoV-2 mRNA (sgRNA) reflecting active replication was quantified in nasal and pharyngeal swabs, and blood chemistry analysis was performed longitudinally up to 18 weeks post-infection. We quantified liver glycogen at necropsy using Periodic acid-Schiff staining. Finally, we longitudinally analyzed 96 plasma proteins using a proximity extension assay (Olink). STRING was used to identify enriched protein networks. Comparisons between the two groups over time were performed using PERMANOVA. Result(s): All animals had detectable sgRNA ( >3.64x106) at day 3, and only two were undetectable at week 5. Post-infection BNT162b2 vaccination partially inhibited the SARS-CoV-2 mediated disruption of glucose levels (P=0.001, Fig. 1A). Liver glycogen levels following necropsy correlated positively with blood glucose levels at week 12 (r=0.74, P =0.003). Histopathological analysis revealed no marked evidence of long-term inflammation or fibrosis of pancreatic islets. Using the plasma proteomic data, we identified a signature of 15 SARS-CoV-2-modulated plasma proteins coinciding with early onset hyperglycemia during acute infection (P=0.001, Fig. 1B). These proteins are enriched for biological processes linked to chemotaxis (FDR=1.38E-06), and viral protein interaction with cytokines (FDR=1.01E-12) (Fig. 1C). Of these, CCL25 and glial cell derived neurotrophic factor (GDNF) remained persistently elevated post-acute infection and correlated with blood glucose levels (r=0.57, P=0.0003;and r=0.64, P<0.0001, respectively, Fig. 1D). Conclusion(s): Our AGM model validates phenotypes of metabolic PASC and offers an opportunity to mechanistically study the manifestations of PASC. Our preliminary data suggest that vaccine-preventable early insults by metabolicregulating immune factors may contribute to long-term dysregulated liver and systemic glucose homeostasis during PASC. These immune factors warrant further investigation for their mechanistic links to PASC. (Figure Presented).

Mucosal rAd5 Immunization against SARS-CoV-2 Spike Elicits Cross-Reactive Nasal and Serum Neutralizing Antibodies and Protects Against Beta Variant Challenge in African Green Monkeys

Background. Mucosal vaccination may offer increased protection against SARS-CoV-2 compared to parental immunization. Here, we describe immunogenicity and efficacy following viral challenge in non-human primates after intranasal delivery of three unique non-replicating adenoviral vector vaccine (rAd5) candidates. Methods. African green monkeys (AMG) were prime boost immunized 29 days apart with vaccine candidates either expressing the parental spike protein alone (Wuhan-S), spike plus nucleocapsid(Wuhan-S-N), or the spike protein fromthe beta variant (beta-S). Serumand nasal swabs were collected every 14 days and humoral responses to full length spike (S) and receptor binding domain (RBD) were assessed.AllAMGs were challenged with SARS-CoV-2 B.1.351 (beta variant)onday 56. Viral loadsmeasured every two days by TCID50 in nasal washes and bronchial lavage fluid post challenge. Results. Mucosal immunization with Wuhan-S induced significant increases in serum IgG and IgA responses against the homologous parental lineage, as well as beta, delta, and omicron variants. In nasal samples, Wuhan-S immunization elicited over 500-fold increases in in cross-reactive IgA against multiple variants of concern including delta and omicron. While the beta-S rAd5 vaccine candidate induced enhanced serum IgG responses to homologous S and RBD proteins, this approach resulted in less cross-reactive antibodies to other variants compared to Wuhan-S rAd5 vaccine. Despite the differences in the ability to elicit cross-reactive antibody responses, all vaccinated AMGs challenged with SARS-CoV-2 B.1.351 (beta variant), had a significant reduction in viral titers by TCID50 in the nasal passages and reduced viral load in bronchial lavage fluid compared to unvaccinated controls. Conclusion. These results demonstrate mucosal administration of rAd5 clinical candidate vaccine, Wuhan-S, is immunogenic and offers cross-protective humoral responses in both serum and nasal compartments against a mismatched SARS-CoV-2 challenge virus.

Special Issue: One health. (Special Issue: One health.)

This special issue consists of 17 papers dealing with issues animal health (captive and wild primates), environmental health (rain forests and mountain areas), and human health (the role of religion in One Health, lessons from the Hanuman langur (Semnopithecus entellus) and other human-non-human primate interactions,and Covid-19).

EVIDENCE of BRAIN HYPOXIA in NEUROPATHOLOGY of SARS-CoV-2-INFECTED NONHUMAN PRIMATES

Background: Neurological manifestations are a major complication of sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and likely contribute to symptoms of "long COVID". Elucidating the mechanisms that underlie neuropathogenesis in infection is critical for identifying or developing viable therapeutic strategies. While neurological injury in infection is varied, cerebrovascular disease is seen at a high frequency among patients over 50 years of age. Additionally, microhemorrhages and hypoxic-ischemic injury are often described in brain autopsy series of human subjects who died from COVID-19. Here, we report neuropathology in aged SARS-CoV-2 infected non-human primates (NHPs) is consistent with that observed in aged human subjects and provide insight into the underlying cause. Methods: Four adult Rhesus macaques and four African green monkeys were inoculated with the 2019-nCoV/USA-WA1/2020strain of SARS-CoV-2 via a multi-route mucosal or aerosol challenge. Two of each species were included as age-matched controls. Frontal, parietal, occipital, and temporal lobes, basal ganglia, cerebellum, and brainstem were interrogated through histopathological and immunohistochemical techniques to identify and characterize the observed pathology. Results: Like humans, pathology was variable but included wide-spread inflammation with nodular lesions, neuronal injury, and microhemorrhages. Neuronal degeneration and apoptosis were confirmed with FluoroJade C and cleaved caspase 3 IHC, which showed foci of positivity, particularly among cerebellar Purkinje cells. This was seen even among infected animals that did not develop severe respiratory disease but was not seen in age-matched controls. Significant upregulation of the alpha subunit of hypoxia inducible factor 1 (HIF1-α), indicative of tissue hypoxia, was observed in brain of all infected animals, regardless of disease severity. Sparse virus was detected in brain endothelial cells but did not associate with the severity of CNS injury. Conclusion: SARS-CoV-2 infected NHPs are a viable animal model for advancing our current understanding of infection-associated neuropathogenesis. Upregulation of HIF1-α in brain of infected animals suggests cerebral hypoxia may underlie or contribute to neuroinflammation and neuronal injury/death and may provide some insight into neurological manifestations observed among asymptomatic patients or those only suffering mild disease.

SARS-CoV-2/COVID-19 models in Macaca mulatta and Papio cynocephalus. Need to replace macaques with baboons

The COVID-19 (or SARS-CoV-2) pandemic has significantly increased the demand for rhesus macaques (Macaca mulatta) for COVID-19 and other biomedical research, so much so that it has outstripped supply. Baboons (Papio cynocephalus) and African green monkeys (Chlorocebus pygerythrus and Chlorocebus aethiops), other well-characterized primate models used in biomedical research, should be considered a promising alternative for COVID-19 infection studies other than macaques.

Intra-Host SARS-CoV-2 Evolution in the Gut of Mucosally-Infected Chlorocebus aethiops (African Green Monkeys).

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 not detected in viral RNA 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, which were detected in rectal swabs from all sampled animals. These findings are demonstrative of intra-host SARS-CoV-2 evolution and may identify a host-adapted variant of SARS-CoV-2 that would be useful in future primate models involving SARS-CoV-2 infection.