This study aimed to clarify the timing and infectivity of equine herpesvirus 9 (EHV-9) infection in BALB/c-nu/nu mice andtheir immunocompetent counterpart (BALB/c). Following intranasal inoculation with 105PFU of EHV-9, specimens from 8mice per group were collected at different times postinoculation (PI) and assessed using histopathology, immunohisto-chemistry for viral antigen, and quantitative real-time polymerasechainreactionforORF30geneexpression.InBALB/c-nu/nu mice, EHV-9 antigen was abundant in olfactory epithelia of all inoculated animals, and in the olfactory bulb of 1animal. In contrast, only 1 BALB/c mouse per time point had rhinitis, with mild to moderate immunopositivity starting from12 to 48 h PI, followed by a gradual virus clearance at 72 h PI. Statistically, significant differences were noted in theimmunohistochemistry reactions between the 2 mouse strains, indicating that BALB/c-nu/nu is more susceptible toinfection. Relative expression levels of ORF30 gene in olfactory epithelia were significantly different between the 2 groups,with the exception of 12 h PI, when BALB/c-nu/nu animals showed dramatic increases in ORF30 gene expression level until48 h PI, followed by a decline in expression level until the endof experiment. In contrast, the expression level in brainsshowed no differences between mouse strain except at 96 h PI. Inboth strains, the highest messenger RNA expression wasdetected at 48 h PI, followed by a decline in BALB/c mice, proving a rapid clearance of virus in BALB/c and a gradual slowingdown of the increased expression levels in BALB/c-nu/nu. (PDF) Susceptibility of BALB/c-nu/nu Mice and BALB/c Mice to Equine Herpesvirus 9 Infection. Available from: https://www.researchgate.net/publication/242334323_Susceptibility_of_BALBc-nunu_Mice_and_BALBc_Mice_to_Equine_Herpesvirus_9_Infection [accessed Sep 10 2019].