Susceptibility of BALB/c-nu/nu mice and BALB/c mice to equine herpesvirus 9 infection.
Authors: El-Nahass E, El-Dakhly K M, El-Habashi N, Anwar S I, Sakai H, Hirata A, Okada A, Abo-Sakaya R, Fukushi H, Yanai T
Journal: Veterinary pathology
Summary
# Editorial Summary Equine herpesvirus 9 (EHV-9) demonstrates markedly different tissue tropism and persistence depending on the host's immune competence, as demonstrated in this comparative infection model using immunodeficient BALB/c-nu/nu mice and immunocompetent BALB/c controls following intranasal inoculation with 10⁵ PFU. Whilst EHV-9 antigen was detected abundantly throughout the olfactory epithelia and bulb in all immunodeficient animals, immunocompetent mice exhibited significantly restricted infection—limited to mild rhinitis in single animals at each timepoint, with viral clearance evident by 72 hours post-inoculation. Quantitative PCR analysis of the ORF30 gene revealed the critical difference: immunocompetent mice demonstrated peak viral gene expression at 48 hours followed by rapid decline, whereas immunodeficient mice showed sustained and elevated expression extending beyond 72 hours, indicating prolonged viral replication in respiratory tissues. These findings underscore the central role of adaptive immunity in controlling EHV-9, with particular implications for understanding vertical transmission risk and latency establishment in naturally infected horses, and suggest that immunocompromised animals warrant particular monitoring for persistent upper respiratory viral shedding and potential neurological involvement.
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Practical Takeaways
- •This laboratory model demonstrates the critical role of immune competence in controlling EHV-9 infection; immunocompromised horses may face similar challenges in viral clearance
- •Viral replication timing peaks around 48 hours post-infection, suggesting this window is critical for intervention strategies if applicable to equine disease
- •The olfactory epithelium appears to be a primary site of viral replication and persistence, which may inform understanding of natural infection routes in horses
Key Findings
- •BALB/c-nu/nu immunocompromised mice showed significantly greater susceptibility to EHV-9 infection with abundant viral antigen in olfactory epithelia compared to immunocompetent BALB/c mice
- •ORF30 gene expression peaked at 48 hours post-inoculation in both strains, with BALB/c-nu/nu mice showing sustained elevated expression through 48 h PI versus rapid clearance in BALB/c mice
- •Immunocompetent BALB/c mice demonstrated rapid viral clearance by 72 hours PI with mild rhinitis in only 1 animal per timepoint, whereas BALB/c-nu/nu mice maintained persistent infection