Partial nucleotide sequences of ORF72 (glycoprotein D,
gD), ORF64 (infected cell protein 4, ICP4)
and ORF30 (DNA polymerase) genes were compared with
corresponding sequences of EHV-1 reference strains to characterize the molecular
variability of Brazilian strains. Virus isolation assays were applied to 74
samples including visceral tissue, total blood, cerebrospinal fluid (CSF) and
nasal swabs of specimens from a total of 64 animals. Only one CSF sample
(Iso07/05 strain) was positive by virus isolation in cell culture. EHV-1
Iso07/05 neurologic strain and two abortion visceral tissues samples (Iso11/06
and Iso33/06) were PCR-positive for ORF33 (glycoprotein B, gB)
gene of EHV-1. A sequence analysis of the ORF72, ORF64 and
ORF30 genes from three EHV-1 archival strains (A3/97,
A4/72, A9/92) and three clinical samples (Iso07/05, Iso11/06 and Iso33/06)
suggested that among Brazilian EHV-1 strains, the amplified region of the
gD gene sequence is highly conserved. Additionally, the
analysis of ICP4 gene showed high nucleotide and amino acid
identities when compared with genotype P strains, suggesting that the EHV-1
Brazilian strains belonged to the same group. All the EHV-1 Brazilian strains
were classified as non-neuropathogenic variants (N752) based on the
ORF30 analysis. These findings indicate a high conservation
of the gD-, ICP4- and ORF30-encoding
sequences. Different pathotypes of the EHV-1 strain might share identical genes
with no specific markers, and tissue tropism is not completely dependent on the
gD envelope, immediate-early ICP4 and DNA
polymerase proteins.