Comparative study for the sensitivity of BHK-21 and bovine kidney cell line for the isolation of FMD viruses

Abstract

Foot and Mouth disease (FMDV) is one of highly contagious diseases of cloven footed animals, although mortality is low in adult animals, but still causing heavy economic losses. Importance of this project is the effective control of disease which is based on quick and sensitive diagnostic assays. The objectives of this particular study is to evaluate the propagation of FMD viruses on two different cell lines and find out not only the rapid and accurate diagnosis as well as isolation of FMD virus on cell lines. For this study, oropharyngeal fluid (OF) samples were collected from 20 buffaloes from peri urban dairy farms in Islamabad. Probang cups were used for sampling. Probang sampling was first time introduced in Pakistan. These OF samples were treated with tricholotriflouroethane (TTE). Afterwards, these samples were inoculated onto two different cell lines, BHK-21 (Baby Hamster Kidney) and bovine kidney (BK) cells. A sample was declared positive for FMD virus when FMD virus specific cytopathic effects (CPEs) were observed. The virus was passaged for five passages level on BHK-21 and three passage level on BK cells. If a sample did not show any CPEs after this, it was declared as negative for FMD. The agreement, between the two cell lines on the presence of FMD virus in OF samples, was estimated by Cohen's kappa statistics (κ). Of the 20 OF samples passaged on BHK21 cell line, 8 (40%) showed characteristic CPEs within 5 blind passages; the BK cells showed characteristic CPEs for 15 (75%) samples within 3 blind passages. Kappa value was -1.13 (p= 0.99) showing that both cell lines moderately disagree on the status of OF fluids regarding FMD but there was no evidence against the null hypothesis that both cell lines are equally good at detecting the FMD virus in OF samples. The results suggest that both cell lines may largely disagree on the status of a OF sample for FMD. It was clearly evident from the infectivity titres of BK cell line that is 2.25 it is more suitable for vaccine production than BHK-21, but will need further studies with large sample size to evaluate these findings.