Comparative analysis of BTS-34 and Vero-76 cell lines for isolation of peste des Petits Ruminants (PPR) virus

Abstract

Peste de petits ruminant (PPR) is a highly contagious viral disease affecting predominantly sheep and goats. The virus belongs to the genus Morbillivirus accounting for causing immunosuppression and severe lymphopenia in host lymphoid cells principally due to the presence of a glycoprotein known as Signaling Lymphocyte Activation Molecule (SLAM) acting as cellular receptor. Limitations regarding the efficiency of PPR virus isolation using a variety of cell lines paved the way to the use of a new cell line (BTS-34) expressing these receptors. In the present study, a total of 18 PPRV confirmed strains were inoculated onto low passage Vero-76 and BTS-34 cell lines simultaneously to compare the susceptibilities of Vero and BTS cells for PPR virus isolation. The recovered viruses were then re-confirmed by Ic-ELISA and RT-PCR. In order to investigate the differences in titers of virus strains, serial tenfold dilutions were made separately using both cells at a density of 0.01x106 and tissue culture infective dose fifty (TCID50) was calculated. The results revealed that the characteristic pattern of the CPEs was more obvious in BTS-34 cell line marked by giant cells ultimately transforming into distinguished syncytia in 2 to 3 days. The average incubation time for virus isolation on Vero cells was about 10 days and syncytia formation were less marked. The growth curve indicated a one log increase in virus titer in case of BTS-34 cell line as compared to Vero-76. Statistically, there was significant difference between two types of cell lines in terms of number of days taken for PPR virus isolation as determined by single factor ANOVA (P<0.001). The study showed that BTS cells produced high virus titer with clearly distinct CPEs in short time due to the presence of SLAM receptors as compared to Vero cells suggesting the BTS cells to be more efficient and sensitive for PPRV isolation.