Comparative efficacy of various chemical stabilizers on the thermostability of a live-attenuated peste des petits ruminants (PPR) vaccine

Abstract

Thermostability of a live-attenuated peste des petits ruminants (PPR) vaccine recently developed at Indian Veterinary Research Institute was studied using conventional lyophilization conditions. A total of four stabilizers viz., lactalbumin hydrolysate–sucrose (LS), Weybridge medium (WBM), buffered gelatin-sorbitol (BUGS) and trehalose dihydrate (TD) were used to prepare the lyophilized vaccine. The study revealed that the PPR vaccine lyophilized with either LS or TD is more stable than rest of the stabilizers having an expiry period of at least 45 days (so far studied) at 4 °C, 15–19 days at 25 °C and 1–2 days at 37 °C. However, at a temperature of 45 °C, BUGS had a marginal superiority, although lasted for few hours, followed by TD and LS with respect to shelf-life, LS and TD with respect to half-life. On the basis of half-life also LS followed by TD appeared superior at a temperature of 4, 25 and 37 °C. Reconstitution of vaccine with distilled water or 1 M MgSO4 or 0.85% NaCl maintained the required virus titre (2.5 log10 TCID50 per dose) up to 8 h at 37 °C and 7 h at 45 °C. Among the three diluents, 1 M MgSO4 appeared to be the better diluent for reconstitution of lyophilized PPR vaccine, as the loss on dilution was lowest and maintain the required virus titre for a longer period. Investigation suggests for using LS as stabilizer for lyophilization and 1 M MgSO4 as vaccine diluent for the newly developed PPR vaccine.