An equine herpesvirus 1 mutant with a lacZ insertion between open reading frames 62 and 63 is replication competent and causes disease in the murine respiratory model.

The research focuses on the construction and examination of a mutant version of equine herpesvirus 1 (EHV-1), created by inserting a lacZ gene between two of the virus’s existing genes. This mutation didn’t affect the virus’s growth or pathology but allowed for improved monitoring of its progress. This mutant virus remained virulent, still causing the disease in a mouse model and facilitating understanding of the virus’s pathogenic process.

Methodology and Findings

• The researchers produced a mutation of EHV-1 by inserting a lacZ expression cassette, which is used to monitor the behavior of the virus, between genes 62 and 63 of the virus.
• In laboratory conditions, this mutated virus, referred to as lacZ62/63-EHV-1, exhibited similar growth patterns to the wild type virus, with identical plaque formation and cellular effects, demonstrating that the mutation didn’t interfere with its routine activities.
• Verification techniques such as reverse transcriptase PCR and immunoblot analysis confirmed that the inserted lacZ gene didn’t interfere with the functioning or expression of neighboring genes.
• The lacZ62/63-EHV-1 virus was found to cause respiratory disease in BALB/c mice, a model organism, in a pattern similar to the original, non-mutated virus.
• The use of X-gal staining allowed the researchers to visually track the virus in lung tissues, highlighting infected cells with a blue color, thereby proving the usefulness of the lacZ gene addition.

Implications and Conclusions

• The lacZ62/63-EHV-1 virus’s success as a replication-capable, disease-inducing, and monitorable virus proves the feasibility of inserting a foreign gene such as lacZ into the EHV-1 virus without impairing its functionality.
• The use of the lacZ gene, which can be easily visualized and examined in laboratory conditions, provides a valuable tool for studying the virus’s behavior and growth.
• The results highlight the potential for similar approaches in studying other viruses or developing vaccines, as the lacZ gene insertion allows real-time tracking of the virus in host tissues.
• The research provides a critical foundation for further studies into the pathology and potential treatment avenues for EHV-1.