Natural Recombinant between Equine Herpesviruses 1 and 4 in the ICP4 Gene

Abstract

Equine herpesvirus 1 (EHV‐1) is a pathogen causing rhinopneumonia in young horses, abortion in mares, and myeloencephalitis in adult horses. Two types, EHV‐1 P and EHV‐1 B, have recently been dominant among 16 electropherotypes. EHV‐1 P and EHV‐1 B viruses were compared by long and accurate polymerase chain reaction (LA‐PCR) and restriction fragment length polymorphism (RFLP) analysis. Differences in restriction sites were found to be focused in ORF64, which encodes the infected cell protein 4 (ICP4), and downstream of the ICP4 gene. The 3′‐end and downstream of ICP4 gene of EHV‐1 B were found to be replaced by the corresponding region of EHV‐4, indicating that EHV‐1 B is a naturally occurring recombinant virus between progenitors of EHV‐1 P and EHV‐4. This is the first report showing a natural interspecies recombinant in alphaherpesviruses.

Comparison of the Growth Kinetics of Neuropathogenic and Nonneuropathogenic Equid Herpesvirus Type 1 (EHV-1) Strains in Cultured Murine Neuronal Cells and the Relevance of the D/N752 Coding Change in DNA Polymerase Gene (ORF30)

“…The main electropherotypes are P and B, both of which are currently detected in horse populations in Japan [14,17,20]. EHV-1 isolated from horses with neurological disorders has been characterized as type P but not as type B [18,21].We previously observed differences between EHV-1 P and B in ORF64 encoding infected cell protein 4 (ICP4), which is involved in transcription regulation and interaction with host factors [5,20]. The 3'-end and downstream region of ORF64 in EHV-1 B were replaced with the corresponding regions in EHV-4.…”

“…The main electropherotypes are P and B, both of which are currently detected in horse populations in Japan [14,17,20]. EHV-1 isolated from horses with neurological disorders has been characterized as type P but not as type B [18,21].…”

“…We previously observed differences between EHV-1 P and B in ORF64 encoding infected cell protein 4 (ICP4), which is involved in transcription regulation and interaction with host factors [5,20]. The 3'-end and downstream region of ORF64 in EHV-1 B were replaced with the corresponding regions in EHV-4.…”

“…EHV-9 was isolated from a Thomson's gazelle that died due to acute neurological disease in Japan [8]. All the viruses used in this study were propagated as described previously [11,20] and were not cloned.…”

“…Total DNA for each virus was extracted from infected fetal equine kidney cells using the sodium dodecyl sulfate, proteinase K and phenol-chloroform method, as described previously [20]. A 1066-bp sequence of ORF30 was amplified by polymerase chain reaction (PCR) using the following primers: 5'-actccagtttgatgggcgctcta-3' (forward-1) and 5'-tattgtatccaggactctaggct-3' (reverse-4).…”