Diet-induced obesity and diabetes enhance mortality and reduce vaccine efficacy for SARS-CoV-2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), emerged in Wuhan, China, in December 2019. As of September 2023, there have been over 770 million confirmed cases of COVID-19, including over 6.9 million deaths. Epidemiologic studies have indicated that comorbidities of obesity and diabetes mellitus are associated with increased morbidity and mortality following SARS-CoV-2 infection. We determined how the comorbidities of obesity and diabetes affect morbidity and mortality following SARS-CoV-2 infection in unvaccinated and adjuvanted spike nanoparticle (NVX-CoV2373) vaccinated mice. We find that obese/diabetic mice infected with SARS-CoV-2 have increased morbidity and mortality compared to age-matched normal mice. Mice that were fed a high-fat diet (HFD) and then vaccinated with NVX-CoV2373 produce equivalent neutralizing antibody titers compared to those fed a normal diet (ND). However, the HFD mice have reduced viral clearance early in infection. Analysis of the inflammatory immune response in HFD mice demonstrates a recruitment of neutrophils that was correlated with increased mortality and reduced clearance of the virus. Depletion of neutrophils in diabetic/obese vaccinated mice reduced disease severity and protected mice from lethality. This model recapitulates the increased disease severity associated with obesity and diabetes in humans with COVID-19 and is an important comorbidity to study with increasing obesity and diabetes across the world. IMPORTANCE Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a wide spectrum of diseases in the human population, from asymptomatic infections to death. It is important to study the host differences that may alter the pathogenesis of this virus. One clinical finding in coronavirus disease 2019 (COVID-19) patients is that people with obesity or diabetes are at increased risk of severe illness from SARS-CoV-2 infection. We used a high-fat diet model in mice to study the effects of obesity and type 2 diabetes on SARS-CoV-2 infection as well as how these comorbidities alter the response to vaccination. We find that diabetic/obese mice have increased disease after SARS-CoV-2 infection and they have slower clearance of the virus. We find that the lungs of these mice have increased neutrophils and that removing these neutrophils protects diabetic/obese mice from disease. This demonstrates why these diseases have increased risk of severe disease and suggests specific interventions upon infection.