A Neonatal Murine Model Of Coxsackievirus A6 Infection For Evaluation Of Antiviral And Vaccine Efficacy

Hand,foot,and mouth disease?HFMD?is a global health concern.Family Picornaviridae members,particularly enterovirus 71?EV-71?and coxsackievirus A16?CV-A16?,are the primary etiological agents of HFMD;however,a third enterovirus.A species,CVA6,has been recently associated with epidemic outbreaks.Study of the pathogenesis of CVA6 infection and development of antivirals and vaccines are hind-ered by a lack of appropriate animal models.In this study,we have developed and characterized a murine model of CVA6 infection that was employed to evaluate the antiviral activities of different drugs and the protective efficacies of CVA6-inactivated vaccines.Neonatal mice were susceptible to CVA6infection via intramuscular inoculation,and the susceptibility of mice to CVA6 infection was age and dose dependent.Five-day-old mice infected with 10^5.5 50%tissue culture infective doses(TCID₅₀)of the CVA6 WF057R strain consistently exhibited clinical signs,including reduced mobility,lower weight gain,and quadriplegia with significant pathology in the brain,hind limb skeletal muscles,and lungs of the infected mice in the moribund state.Immunohistochemicalanalysis and quantitative reverse transcription-PCR analyses showed heavy viral loads?11 log10?in skeletal muscle,and elevated levels of interleukin-6?IL-6;2,000 pg/ml?were associated with severe viral pneumonia and encephalitis.Ribavirinandgammainterferonadministeredprophylacticallydiminished CVA6-associated pathology in vivo,and treatment with IL-6 accelerated the death of neonatal mice.Both specific anti-CVA6 serum and maternal antibody play important roles in controlling CVA6 infection and viral replication.Collectively,these findings indicate that this neonatal murine model will be invaluable in future studies to develop CVA6-specific antivirals and vaccines.