Equid herpesvirus-1 Distribution in Equine Lymphoid and Neural Tissues 70 Days Post Infection
Susanna Samoilowa1, Kim S Giessler1,2, Carlos E Medina Torres1
1Equine Hospital, Division of Medicine and Reproduction, Center for Clinical Veterinary Medicine, Ludwig-Maximilians University, 80539 Munich, Germany.
Pathogens (Basel, Switzerland)
|July 2, 2021
Summary
Equid herpesvirus-1 (EHV-1) establishes latent infections in horses. Viral DNA was found in various neural and lymphoid tissues, but not in peripheral blood mononuclear cells (PBMC).
Area of Science:
- Veterinary Virology
- Equine Infectious Diseases
- Herpesvirus Pathogenesis
Background:
- Equid herpesvirus-1 (EHV-1) is a significant pathogen in horses, causing respiratory illness, abortions, and neurological disease.
- Latency is a critical factor in EHV-1 epidemiology, with known sites including trigeminal ganglia (TG), respiratory associated lymphoid tissue (RALT), and peripheral blood mononuclear cells (PBMC).
- The full tissue distribution of EHV-1 during latent infection remains incompletely understood.
Purpose of the Study:
- To investigate the comprehensive distribution of EHV-1 DNA throughout the equine body.
- To determine the presence of viral DNA in various neural and lymphoid tissues following experimental EHV-1 infection.
- To assess viral gene expression in different tissues.
Main Methods:
- Experimental intranasal infection of 25 horses with three different EHV-1 strains.
- Necropsy and tissue collection on Day 70 post-infection, including various ganglia, RALT, mesenteric lymph nodes, spleen, and PBMC.
- Quantitative PCR (qPCR) to measure viral loads and L-gene transcriptional activity.
- Immunohistochemistry (IHC) to detect viral protein expression in neural tissues.
Main Results:
- EHV-1 DNA was detected in numerous neural and lymphoid tissues.
- Viral DNA was notably absent in peripheral blood mononuclear cells (PBMC) of infected horses.
- No L-gene transcriptional activity or protein expression was detected in any of the sampled tissues.
- Tissue tropism varied between the wild-type Ab4 virus and the two mutant strains.
Conclusions:
- EHV-1 DNA disseminates to a wider range of neural and lymphoid tissues than previously confirmed.
- PBMC do not appear to harbor EHV-1 DNA during the investigated phase of infection.
- The lack of detectable viral gene expression suggests a quiescent state of latency in these tissues at 70 days post-infection.
- Distinct tissue tropism profiles exist among different EHV-1 strains.
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