1Department of Veterinary Microbiology, College of Veterinary Science, Assam Agricultural University, Guwahati-781 022, Assam, India.
2Department of Animal Biotechnology, College of Veterinary Science, Assam Agricultural University, Guwahati-781 022, Assam, India.
3Department of Veterinary Biochemistry, College of Veterinary Science, Assam Agricultural University, Guwahati-781 022, Assam, India.
*Corresponding Author: Jayashree Sarma, Department of Veterinary Microbiology, College of Veterinary Science, Assam Agricultural University, Guwahati-781 022, Assam, India. Email: jayashreesarma4@gmail.com
Classical swine fever, a highly endemic pig disease in India, particularly in the NER, spots Assam with the highest outbreaks. Despite available CSF vaccines, concern prevails over protective immune response of C-strain vaccine, as emerging genotype 2 replaces genotype 1 globally, causing outbreak in immunized herds.
The study assessed the cross-protective and cross-neutralization potency of existing vaccines against additional prevalent genotypes. Archived CSFV samples were reconfirmed by S-ELISA and nRT-PCR. Following E2 full-length genome sequencing and phylogeny (MEGA-X), representative CSFV samples from NER were isolated in PK-15 cell line. Hyper-immune serum was raised to test neutralization and cross-neutralization efficacy.
Of 77 archived samples, 43 were S-ELISA positive and 47 nRT-PCR. Phylogenetic analysis revealed either 1.1 or 2.2 subgenotypes. Virus titre was 4.49-5.16 log TCID50 per ml in four samples representing two sub-genotypes (1.1 and 2.2) after 5 passages in PK-15 cells. Neutralization assay showed complete neutralization for sub-genotype 1.1, sub-genotype 2.2 showed 84% with C-strain specific antibody. The study revealed prevalence of both sub-genotypes 1.1 and 2.2 in NER with lower neutralization efficacy of vaccine strain antibodies to heterologous genotypes with conserved immunogenic epitope.
Classical swine fever (CSF), C-strain vaccine, Genotypes, Neutralization
