Animal vaccinations.

Tricolor guinea pigs were vaccinated subcutaneously with either Δ123A7-S VLPs or RBDA7-S VLPs (8 per group) containing the equivalent of 10 μg of E2 or vaccinated with VLPs containing S alone (6 per group) containing the equivalent of 40 μg of S antigen, formulated with AddaVax (InvivoGen, San Diego, CA) adjuvant at a 1:1 ratio in a total volume of 200 μL. All guinea pigs received four doses of the vaccine formulation at weeks 0, 3, 6, and 9. At week 11, blood was collected via nonrecovery cardiac puncture. This was performed under anesthesia with isoflurane/oxygen (induction, 3 to 4%; maintenance, 1 to 2%; 1.2 L/min). Guinea pigs were then humanely euthanized by intracardiac injection of potassium chloride (KCl; 4 M; 2.5 mL/kg) under anesthetic (isoflurane). Guinea pigs used for immunizations were cared for in accordance with the Australian code for the care and use of animals for scientific purposes (59), under SAHMRI AEC project number SAM210.