Sex differences in lung imaging and SARS-CoV-2 antibody responses in a COVID-19 golden Syrian hamster model

Abstract

In the ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more severe outcomes are reported in males compared with females, including hospitalizations and deaths. Animal models can provide an opportunity to mechanistically interrogate causes of sex differences in the pathogenesis of SARS-CoV-2. Adult male and female golden Syrian hamsters (8-10 weeks of age) were inoculated intranasally with 105 TCID50 of SARS-CoV-2/USA-WA1/2020 and euthanized at several time points during the acute (i.e., virus actively replicating) and recovery (i.e., after the infectious virus has been cleared) phases of infection. There was no mortality, but infected male hamsters experienced greater morbidity, losing a greater percentage of body mass, developing more extensive pneumonia as noted on chest computed tomography, and recovering more slowly than females. Treatment of male hamsters with estradiol did not alter pulmonary damage. Virus titers in respiratory tissues, including nasal turbinates, trachea, and lungs, and pulmonary cytokine concentrations, including IFNb and TNFa, were comparable between the sexes. However, during the recovery phase of infection, females mounted two-fold greater IgM, IgG, and IgA responses against the receptor-binding domain of the spike protein (S-RBD) in both plasma and respiratory tissues. Female hamsters also had significantly greater IgG antibodies against whole inactivated SARS-CoV-2 and mutant S-RBDs, as well as virus neutralizing antibodies in plasma. The development of an animal model to study COVID-19 sex differences will allow for a greater mechanistic understanding of the SARS-CoV-2 associated sex differences seen in the human population.

Progression and Resolution of SARS-CoV-2 Infection in Golden Syrian Hamsters

“…While infectious virus was cleared from the respiratory tract of most of the hamsters by 7 DPI, infectious virus was detected in the lungs of a single animal. No sex differences in viral load were detected in infected hamsters 28 .…”

“…Infectious virus titers in the respiratory tissue homogenates were determined by the 50% tissue culture infectious dose (TCID50) assay 28 . Briefly, tissue homogenates were serially diluted 10-fold, transferred in sextuplicate into 96-well plates confluent with Vero-E6-TMPRSS2 cells (obtained from the Japan Institute of Infectious Diseases), incubated at 37 0 C for 4 days, and then stained with naphthol blue-black solution for visualization.…”

“…For detection of SARS-CoV-2 genome copies, RNA was extracted from lungs using the Qiagen viral RNA extraction kit (Qiagen) and reverse transcriptase PCR (RTqPCR) was performed as previously described 29 . Viral data from a subset of these animals has been included in a report on humoral responses in this model 28 .…”

A bacterial extracellular vesicle-based intranasal vaccine against SARS-CoV-2 protects against disease and elicits neutralizing antibodies to wild-type and Delta variants

“…We report that this technology efficiently couples a SpyTag-RBD fusion protein produced in mammalian cell culture onto bacterial OMVs, resulting in RBD-OMVs that are recognized by antibodies against SARS-CoV-2. Furthermore, we show that intranasal vaccination with RBD-OMVs elicits antibodies, including neutralization responses against both wild-type and Delta viral variants, and confers protection against challenge with SARS-CoV-2 in a recently developed hamster model (18,19).…”

“…On days 0, 7, 14, 21, 28, 35, and 42, hamsters were weighed, temperature was measured, and 200-300 µl blood was collected via sublingual vein into EDTA tubes. On day 44, hamsters were challenged intranasally with 10^7 TCID50 of SARS-CoV-2 USA/Washington-1/2020, NR-52281 [BEI Resources, virus prepared as described previously (16)] diluted in 100 µl DMEM in an animal biosafety level 3 (ABSL3) facility. Weight and temperature were monitored daily after infection, up to day 48 (4 days post infection).…”