A 10-Day-Old Murine Model of Coxsackievirus A6 Infection for the Evaluation of Vaccines and Antiviral Drugs

Abstract

Coxsackievirus A6 (CVA6) is recognized as a major enterovirus type that can cause severe hand, foot, and mouth disease and spread widely among children. Vaccines and antiviral drugs may be developed more effectively based on a stable and easy-to-operate CVA6 mouse infection model. In this study, a wild CVA6-W strain was sub-cultured in newborn mice of different ages (in days), for adaptation. Therefore, a CVA6-A mouse-adapted strain capable of stably infecting the mice was generated, and a fatal model was built. As the result indicated, CVA6-A could infect the 10-day-old mice to generate higher levels of IFN-γ, IL-6, and IL-10. The mice infected with CVA6-A were treated with IFN-α1b at a higher dose, with complete protection. Based on this strain, an animal model with active immunization was built to evaluate antiviral protection by active immunization. The three-day-old mice were pre-immunized with inactivated CVA6 thereby generating IgM and IgG antibodies within 7 days that enabled complete protection of the pre-immunized mice following the CVA6 virus challenge. There were eight mutations in the genome of CVA6-A than in that of CVA6-W, possibly attributed to the virulence of CVA6 in mice. Briefly, the CVA6 infection model of the 10-day-old mice built herein, may serve as an applicable preclinical evaluation model for CVA6 antiviral drugs and vaccine study.

A mouse-adapted CVA6 strain exhibits neurotropism and triggers systemic manifestations in a novel murine model

“…Therefore, establishing animal models with typical clinical symptoms is one of the important steps to understanding the pathogenesis of CVA6 infection and the development of vaccines, therapeutic antibodies, and antiviral drugs. Recently, several animal models [ 20 , 27 , 28 , 39 ] have been reported to evaluate vaccines and antiviral drugs and study the pathogenesis. However, those CVA6 animal models differ from our model in several important respects, namely the dose and route of inoculation, the strain of laboratory mice used, and, critically, the virus strain used.…”

“…Compared with other injection routes, the oral infection route better simulates the human infection. Secondly, compared with the age of the mice used previously [ 20 ], elderly newborn mice can deliver a higher dose of drugs and are easy to use to evaluate antiviral drugs subsequently. Third, 15-day-old newborn mice were also used in our study, which provides a possibility for the establishment of elderly mice models.…”

“…The brains, spinal cords, lungs, limb muscles, hearts, kidneys, intestines, livers, stomachs, spleens, skins, upper jaws, down jaws, tongues, and claws samples were obtained and fixed in 10% paraformaldehyde for 48 h. After fixation, paraffin-embedded organs and tissues were cut into 5 μm sections and stained with hematoxylin and eosin (H&E). The expression of CVA6 VP1 (GeneTex Inc., Irvine, CA, USA) (Catalog number: GTX132346) in those tissues of mock- and CVA6-infected mice was detected by immunohistochemical (IHC) staining in accordance with a standard immunoperoxidase procedure as described previously [ 20 ]. Because the mouse-adapted CVA6 strain was generated from muscle tissue of mice, muscle slices were used as positive controls in this study.…”

“…Overall, Enterovirus animal models mainly consist of the models of mouse-adaptation models [ 20 ], murine [ 21 ], gerbil [ 22 ], immunodeficient mice [ 23 ], non-human primate [ 24 ], tree shrew [ 25 ] and transgenic mice models [ 26 ]. SCARB2, a functional receptor for EVA71 entry, has an essential effect on EVA71 infection, indicated by our recent research on Enterovirus infection [ 26 ].…”

“…Another study introduced a 10-day-old murine model of CVA6 with mouse-adapted strains via i.p. inoculation [ 20 ]. Nevertheless, because i.p., i.m.…”