Glycoprotein C gene based molecular subtyping of a bovine herpesvirus -1 isolate from uttar pradesh, India

Development and evaluation of recombinant gD protein based ELISA for sero-surveillance of BoHV-1 in India

Bovine herpes virus-1 (BoHV-1) is responsible for production losses through decreased milk yields, abortions, infertility, and trade restrictions in the bovine population. The disease is endemic in many countries including India. As the virus harbors a unique feature of latency animals once infected with the virus remain sero-positive for lifetime and can re-excrete the virus when exposed to stressful conditions. Hence, identification and culling of infected animals is only the means to minimize infection-associated losses. In this study, an economical indigenous assay for the detection of BoHV-1 specific antibodies was developed to cater to the huge bovine population of the country. The viral structural gD protein, expressed in the prokaryotic system was used for optimization of an indirect ELISA for bovines followed by statistical validation of the assay. The diagnostic sensitivity and specificity of the indirect ELISA were 82.9% and 91.3% respectively. Systematically collected serum samples representing organized, unorganized and breeding farms of India were tested with the indigenously developed assay for further validation.

Phylogenetic analysis and characterization of bovine herpesvirus-1 in cattle of China, 2016-2019

Bovine herpesvirus type 1 (BoHV-1) is one of the most critical pathogens in cattle and is prevalent in China. BoHV-1 is divided into two gene types, BoHV-1.1 and 1.2, which are further differentiated into two subtypes, BoHV-1.2a and 1.2b. However, the phylogenetic analysis of BoHV-1 isolates has not been reported in China. To perform a molecular epidemiological survey based on isolates from cattle in China, 102 lung tissue samples of calves under ten months of age with respiratory disease (BRD) that died from 2016 to 2019 in China were used to isolate BoHV-1 with Madin-Darby bovine kidney (MDBK) cells. Part of the BoHV-1 isolates were applied to the phylogenetic analysis based on the region of the glycoprotein C (gC) gene of BoHV-1. Thirty BoHV-1 isolates were obtained, and the gC gene of 13 isolates was amplified by polymerase chain reaction (PCR) methods and sequenced. The result of the phylogenetic analysis according to the 451-nucleotide portion of the gC gene found that all of 13 isolates belonged to the BoHV-1.2b gene subtype, but these isolates had located two different phylogenetic tree branches. The gC gene sequence homology of isolates in group1 was higher with a reference strain of BoHV-1.2b EVI14 up to 98.0-100%, while in group 2, this was higher with reference strain BoHV-1.2b B589 up to 97.8-99.8%. The deduced amino acid sequence of gC from isolates in group 2 had two amino acid mutations with interference strain BoHV-1.2b K22 or BoHV-1.1 COOPER. The cytopathic effects (CPEs) of BoHV-1 isolates in group 2 were ulcered on the centration like a volcano on MDBK cell, and different from traditional CPEs of BoHV-1. Overall, BoHV-1.2b seems to be the primary strain of BoHV-1 in cattle in China and is also a critical cause of BRD. These BoHV-1.2b isolates had significant genetic variations.

Detection of bovine herpes virus (BOHV-1) infection in respiratory tract of bovines

Infectious bovine rhinotracheitis (IBR) is considered commonest form of BoHV-1 respiratory tract infection. The current work was designed to study the incidence of IBR using molecular technique and antigen detection sandwich ELISA. In the present study, nasal swab samples (100) and tracheal lavages (6) were collected from bovines, which were showing respiratory symptoms from clinics of College of Veterinary Science, GADVASU, Ludhiana. Four lung tissues were also collected from dead animals. All nasal samples were tested for IBR virus antigen by using commercial sandwich ELISA kit. The antigenic incidence of BoHV-1 was reported to be 1% in tested animals. For molecular detection of BoHV-1 in respiratory tract, the DNA was extracted from all samples (nasal swabs, tracheal lavages and lung tissues) and subjected to gI gene specific PCR by using published primers. The overall incidence of BoHV-1 in nasal swabs of animals with the history of respiratory symptoms was found to be 3% and rest of the samples were found negative for IBR virus in PCR. Species wise evaluation of BoHV-1 infection revealed that out of 75 cattle, 3 (4.0%) cattle were found positive in PCR where as none of the buffaloes were found positive in present study. The animals older than 3 year of age showed the higher incidence (4.2%) than animal up to 3 years of age (2.8%). In this study, all positive cattle were crossbred females. According to sex wise status, it was observed that females are more prone to infection, which may be because of production stress in female animals.

Phylogenetic analysis of glycoprotein B gene sequences of bovine herpesvirus 1 isolates from India reveals the predominance of subtype 1.1

AIM

This study was conducted for the isolation and molecular characterization of bovine herpesvirus 1 (BoHV-1) isolated from the nasal and vaginal swabs collected from naturally infected cattle showing clinical symptoms of the respiratory disease.

MATERIALS AND METHODS

Isolation of BoHV-1 virus performed on clinical samples collected from 65 cattle from five states of India. The BoHV-1 isolates were further confirmed by polymerase chain reaction (PCR) using primers specific for glycoprotein B (gB) genomic region. PCR amplification was performed using previously published gB gene-specific primer pairs. gB PCR amplicons obtained from all isolates were sequenced, and phylogenetic analysis was performed using software.

RESULTS

A total of 12 samples were found positive in cell culture isolation. 11 isolates showed the visible cytopathic effect on Madin-Darby bovine kidney after 72 h. Partial sequence analysis of gB gene of all isolates revealed 99.0-100% homology between them. All isolates showed 99.2-99.8% homology with Cooper stain.

CONCLUSION

BoHV-1.1 is the predominant circulating subtype of BoHV in India, and all isolates have homology with Cooper stain.