Golden syrian hamsters

For hamster experiments, three- to four-week-old male Golden Syrian hamsters were purchased from Envigo. Animals were intranasally inoculated with 100 μL PBS (mock) or PBS containing 105 focus forming units (ffu) of WT or F17A mutant SARS-CoV-2. Animals were monitored for weight loss and signs of disease for 7 days. On 2 and 4 days post infection (dpi), cohorts of 5 animals were nasal washed with PBS and then sacrificed. Lung tissue was then taken to analyze viral titer by focus forming assay and pathology by hemoxylin and eosin (H&E) staining. H&E staining was performed by the University of Texas Medical Branch Histology Laboratory and then analyzed and scored by a blinded pathologist.
All animal studies were carried out in accordance with a protocol approved by the University of Texas Medical Branch Institutional Animal Care and Use Committee and complied with United States Department of Agriculture guidelines in a laboratory accredited by the Association for Assessment and Accreditation of Laboratory Animal Care. Procedures involving infectious SARS-CoV-2 were performed in the Galveston National Laboratory animal biosafety level 3 (ABSL3) facility.

For all experiments, golden Syrian hamsters (male, three- to four-week old) were purchased from Envigo. All studies were carried out in accordance with a protocol approved by the University of Texas Medical Branch Institutional Animal Care and Use Committee and complied with United StatesDepartment of Agriculture guidelines in a laboratory accredited by the Association for Assessment and Accreditation of Laboratory Animal Care. Procedures involving infectious SARS-CoV-2 were performed in the Galveston National Laboratory ABSL3 facility.
For pathogenesis studies, animals were housed in groups of five and intranasally inoculated with 10⁴ PFU of WT or KR mt SARS-CoV-2. For competition/transmission studies, animals were intranasally inoculated with 10⁴ PFU of SARS-CoV-2 comprising both WT and the KR mt at a 1:1 ratio based on stock titer. During competition/transmission studies, animals were singly housed throughout the experiment, except during the 8-hour transmission period, when they were housed in groups of two (1 donor and 1 recipient). For all experiments, animals were monitored daily for weight loss and development of clinical disease until the termination of the experiment. Inoculations and other animal manipulations (except weighing) were carried out under anesthesia with isoflurane (Henry Schein Animal Health).

C57 BL/6 mice (females, aged 10–12 weeks, Charles River) were used for all murine studies. Golden Syrian Hamsters (females, aged 16–18 weeks old; Envigo) were used for the hamster study. All animal procedures were performed under the UK Home Office project license PPL 70/8276. For enumeration of C. difficile spores in feces or cecum, samples were homogenized in 70% ethanol, incubated overnight, serially diluted in sterile water and plated onto selective ChromID. Plates were incubated anaerobically for 2 days (37 °C) before counting [35 (link)]. Toxins A and B in fecal and cecal samples were quantified using ELISA (Supplementary Methods) [35 (link)].

Fifteen 4-week-old golden Syrian hamsters (Envigo, Indianapolis, IN) were immunized intranasally with 1.5 × 10⁵ PFU per animal of XBB.1.5 spike-based monovalent vaccine (recombinant mumps virus expressing spike of XBB.1.5). Three weeks later, hamsters were boosted with the same vaccine at the same dose. Blood was collected at week 5 after initial immunization (week 2 after booster immunization).