The pathogenesis of ED71, a defined deletion mutant of equine herpesvirus-1, in a murine intranasal infection model for equine abortion.

The study looks at the effects of a modified equine herpesvirus-1 (EHV-1) in a mouse model replicating equine abortion. More specifically, it investigates how mutant ED71 affects pregnant mice, despite previously being deemed ineffective.

Introduction to EHV-1 and its Relevance

• The research project revolves around a group of equine herpesvirus-1 (EHV-1) mutants with deletions in non-essential genes. These mutants were previously tested in a murine (mouse model) intranasal infection model to simulate equine abortion conditions.
• One such mutant, dubbed ED71, was identified as attenuated in the model, indicating its limited ability to cause disease.

Inoculation of ED71 in Pregnant Mice

• Despite ED71’s attenuation, the study delves deeper into its effect if introduced into pregnant mice. The report indicates a premature parturition outcome, leading to the birth of dead or dying foetuses. This is a critical finding contradicting the initial assumption of ED71’s feeble pathogenic properties.

Evaluation of Protection Against Abortion

• The study also examines the potential prevention of abortion in mice previously inoculated with the ED71 mutant, followed by an encounter with the wild type virus.
• The research suggests that inoculation with the ED71 mutant 14 days post-conception provides no protection against abortion, against the hypotheses that the body’s immune response to the attenuated virus may confer some protection against the disease.

Study Significance

• The research shows the potential dangers of the previously deemed attenuated virus variant, ED71. Despite its reported inability to cause disease initially, it proves to be pathogenic in pregnant mice, leading to premature birth and dead or critically ill foetuses.
• The study, therefore, refutes the assumption of the previous characterization of the virus and highlights the complexities of viral pathogenesis, especially relating to gestation and virus-induced abortion.