ABSTRACT
This chapter describes the establishment of a Gn pig model of HuNoV infection and diarrhea using two GII.4 HuNoV variants GII.4/2006b and GII.4/2003 by determining their median infectious dose (ID50) and median diarrhea dose (DD50) in two separate studies. The ID50 of GII.4/2006b in Gn pigs at 33–34 days of age was determined to be 64,300 RNA copies using Reed and Muench method. Cytopathological changes in the small intestine, including irregular microvilli, necrosis and apoptosis, and detection of viral antigens in the tip of villi in the duodenum were demonstrated after HuNoV infection. Using various mathematical approaches (Reed and Muench, Dragstedt-Behrens, Spearman-Karber, exponential, approximate beta-Poisson dose-response models, and area under the curve methods), we estimated the ID50 and DD50 of GII.4/2003 to be between 2,400–3,400 RNA copies, and 21,000–38,000 RNA copies, respectively. Contemporary dose-response models offer greater flexibility and accuracy in estimating ID50. In contrast to classical methods of endpoint estimation, dose-response modeling allows seamless analyses of data that may include inconsistent dilution factors between doses or numbers of subjects per dose group, or small numbers of subjects. Determining challenge virus strain ID50 is crucial for the accurate evaluation of protective efficacies in pre-clinical studies of therapeutics, vaccines, and other prophylactics using this reliable animal model.
