ABSTRACT
Background: The disparity in COVID-19 disease burden between European, Asian, and African countries is notable, with considerably higher morbidity and mortality in many European countries as well as the U.S. Dietary differences between regions could play a role in differential COVID-19 pathogenesis, as Western diets high in fat and sugar have been implicated in enhancing gut damage and pathogenesis during viral infections. Here we investigate the effect of diet on gut immunity and SARS-CoV-2 infection. Method(s): Six pigtail macaques were fed a commercial monkey chow diet, then transitioned to a high fat and sugar chow diet (HFD) for approximately two months prior to infection with Delta strain SARS-CoV-2. Animals were sampled prior to HFD initiation, during HFD administration but prior to infection, and for approximately one month post-infection. HFD was maintained following infection and animals were euthanized at the study conclusion. Result(s): Viral RNA was detected for up to 28 days post-infection in nose swabs, with peak viral load at day 2 at a mean of 8.2x109 copies/mL of swab fluid. Subgenomic RNA (sgRNA, indicating viral replication) decayed more rapidly, with all animals having undetectable sgRNA by day 21, and a lower peak of 2.6x109 copies/mL swab fluid on day 2. Viral RNA load was approximately 3.5 logs greater and sgRNA load approximately 3 logs higher at day 2 than in rhesus macaques infected with WA2020 SARS-CoV-2 and fed standard monkey chow. Mucosal rectal biopsies indicated significantly lower B cell frequencies from baseline to approximately two months following HFD administration (p=0.04, Dunn's), and frequencies had not recovered approximately one month postinfection. GI tract-resident IgG+ B cells were nearly absent at necropsy, with mean frequency 0.03% of total B cells. B cell loss was coupled with modest T cell expansion during HFD administration, though frequencies declined following infection. Furthermore, NK cell frequencies tended to decline from baseline throughout HFD administration, and were further depleted at necropsy one month post-infection. Conclusion(s): SARS-CoV-2 infection can induce lymphopenia, and our sampling of gut mucosal tissue indicates B cell depletion and NK cell loss with a HFD that is further exacerbated by SARS-CoV-2 infection. Excess dietary fat and sugar may disrupt gut barrier integrity and immunity, in turn predisposing the tissue to pathology of viral infection.