Hemagglutinin Gene Diversity of Canine Distemper Virus from Clinical Samples in Brazil.

Canine distemper virus (CDV) affects both domestic dogs and wild animals, resulting in high rates of morbidity and mortality. The viral genome encodes six different proteins. Hemagglutinin (H) is the most variable one, being the basis for molecular phylogenetic analysis, and may lead to antibody recognition mismatch and vaccine failure. The study aimed to analyze the H gene of the CDV in field samples from naturally infected dogs in Brazil.24 urine samples and eye discharge swabs were collected from naturally infected dogs in endemic areas of Brazil. Viral ribonucleic acid (RNA) of collected samples was extracted, converted to cDNA and amplified by polymerase chain reaction (PCR). PCR amplicons of H gene were purified and sequenced for phylogenetic analysis. The protein sequences of the samples were subjected to a Genbank search and aligned with the amino acids sequence of the CDV vaccine strain, "Onderstepoort", to explore their similarity profiles. Sequencing of the fragments that represent the entire H gene sequence demonstrated five distinct isolates, two of them sequenced in full-length. The phylogenetic analysis of the isolates showed that they belong to the cluster of Europe/South America1, differing substantially from the currently used vaccine strains. Deduced amino acid sequence analyzed, showed that the specific substitutions at the SLAM receptor site of the H gene, previously linked to the emergence of diseases in new hosts, and were not detected in these sequences. However, the R580Q substitution detected in the isolated strain H_CDV_A5_PE (GenBank: MK423863) is considered imminently deleterious to the efficiency of fusion and expression of the surface of the binding protein. These findings demonstrate that the genetic variability identified in field strains of the distemper virus in endemic areas in Brazil shows genetic alterations that may lead to antibody mismatch. [ABSTRACT FROM AUTHOR]