| Abstract: | In our previous study, we genetically analyzed bovine viral diarrhea viruses (BVDVs)
isolated from 2000 to 2006 in Japan and reported that subgenotype 1b viruses were
predominant. In the present study, 766 BVDVs isolated from 2006 to 2014 in Hokkaido,
Japan, were genetically analyzed to understand recent epidemics. Phylogenetic analysis
based on nucleotide sequences of the 5′-untranslated region of viral genome revealed that
766 isolates were classified as genotype 1 (BVDV-1; 544 isolates) and genotype 2 (BVDV-2;
222). BVDV-1 isolates were further divided into BVDV-1a (93), 1b (371) and 1c (80)
subgenotypes, and all BVDV-2 isolates were grouped into BVDV-2a subgenotype (222). Further
comparative analysis was performed with BVDV-1a, 1b and 2a viruses isolated from 2001 to
2014. Phylogenetic analysis based on nucleotide sequences of the viral glycoprotein E2
gene, a major target of neutralizing antibodies, revealed that BVDV-1a, 1b and 2a isolates
were further classified into several clusters. Cross-neutralization tests showed that
BVDV-1b isolates were antigenically different from BVDV-1a isolates, and almost BVDV-1a,
1b and 2a isolates were antigenically similar among each subgenotype and each E2 cluster.
Taken together, BVDV-1b viruses are still predominant, and BVDV-2a viruses have increased
recently in Hokkaido, Japan. Field isolates of BVDV-1a, 1b and 2a show genetic diversity
on the E2 gene with antigenic conservation among each subgenotype during the last 14
years. |
