Characterization of humoral immune responses and degree of protection induced by influenza vaccine in cotton rats: Effects of low vaccine dose and single vs booster vaccination

Animal Models Utilized for the Development of Influenza Virus Vaccines

Animal models have been an important tool for the development of influenza virus vaccines since the 1940s. Over the past 80 years, influenza virus vaccines have evolved into more complex formulations, including trivalent and quadrivalent inactivated vaccines, live-attenuated vaccines, and subunit vaccines. However, annual effectiveness data shows that current vaccines have varying levels of protection that range between 40–60% and must be reformulated every few years to combat antigenic drift. To address these issues, novel influenza virus vaccines are currently in development. These vaccines rely heavily on animal models to determine efficacy and immunogenicity. In this review, we describe seasonal and novel influenza virus vaccines and highlight important animal models used to develop them.

Characterization of humoral immune responses and degree of protection induced by influenza vaccine in cotton rats: Effects of low vaccine dose and single vs booster vaccination

Introduction

Cotton rats are a suitable model for the study of influenza disease symptoms and responses to influenza vaccination. We have previously shown that two immunizations with 15 µg whole inactivated virus (WIV) influenza vaccine could completely protect animals from infection with the H1N1pdm09 virus.

Methods

To further explore the cotton rat model, we here investigated the protective potential of a single intramuscular immunization and of prime/boost intramuscular immunizations with a low amount of antigen.

Results

A single intramuscular immunization with doses more than or equal to 0.5 µg WIV reliably evoked antibody responses and doses more than or equal to 1 µg protected the animals from virus replication in the lungs and from severe weight loss. However, clinical symptoms like an increased respiration rate were still apparent. Administration of a booster dose significantly increased the humoral immune responses but did not or only moderately improved protection from clinical symptoms.

Conclusion

Our data suggest that complete and partial protection by influenza vaccines can be mimicked in cotton rats by using specific vaccination regimens.