Vaccine 21 (2003) 4728–4735 Comparative efficacy of various chemical stabilizers on the thermostability of a live-attenuated peste des petits ruminants (PPR) vaccine J. Sarkar, B.P. Sreenivasa ∗ , R.P. Singh, P. Dhar,S.K. Bandyopadhyay Division of Virology, Indian Veterinary Research Institute, Mukteswar Campus, Nainital, Uttaranchal 263138, India Received 20 February 2003; accepted 26 June 2003 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 MgSO 4 or 0.85% NaCl maintained the required virus titre (2.5 log 10 TCID 50 per dose) up to 8 h at 37 ◦ C and 7 h at 45 ◦ C. Among the three diluents, 1 M MgSO 4 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 MgSO 4 as vaccine diluent for the newly developed PPR vaccine. © 2003 Elsevier Ltd. All rights reserved. Keywords: Peste des petits ruminants; PPR; Vaccine; Thermostability 1. Introduction Peste des petits ruminants (PPR) is an acute, highly con- tagious and fatal disease of sheep and goats characterized by pyrexia, oculo-nasal discharge, stomatitis, pneumonia and diarrhea. The causative agent, PPR virus is a member of the genus Morbillivirus within the family Paramyxoviridae and is antigenically closely related to rinderpest virus [1], another member of the genus Morbillivirus which causes similar but distinct disease in wild and domestic ruminants. The disease is considered as one of the major constraints to the productivity of small ruminants in sub Saharan Africa, in Arabian peninsula [2], in Middle East [3] and in India [4–6]. For the control of PPR, the usual practice was to use het- erologous rinderpest (RP) vaccine of Plowright and Ferris [7]. Due to the ongoing rinderpest eradication programs in different countries, use of rinderpest vaccine for the control of PPR in small ruminants has been restricted or banned in ∗ Corresponding author. Present address: Indian Veterinary Research Institute, Bangalore Campus, Hebbal, Bangalore 560024, India. Tel.: +91-80-3410729; fax: +91-80-3412509. E-mail address: bpsrini@scientist.com (B.P. Sreenivasa). order to avoid complications in RP sero-surveillance. The only way to control PPR is the use of a homologous vaccine. At present, the only commercially available vaccine has been developed from an African isolate of PPR virus [8]. Recently, a homologous live-attenuated vaccine has been developed at Indian Veterinary Research Institute (IVRI) at its Mukteswar Laboratory [9] from an indigenous isolate of PPR virus, which has reached a stage of phase III trials. The IVRI’s PPR vaccine is a live-attenuated vaccine and is susceptible to thermal degradation similar to RP virus. No published data is presently available on the thermosta- bility of conventionally lyophilized PPR vaccine. In a recent report [10], the PPR vaccine virus of Diallo et al. [8] was used to prepare ‘Xerovac’, a novel thermostable vaccine prepared using trehalose dihydrate. Thermostability of a live vaccine can be defined in terms of its shelf-life at ambient temperature simulated with field situation. Such studies are important for vaccines to be used in developing countries where vaccine quality suffers due to difficulties in transportation and storage facilities owing to frequent power failures and untrained manpower. The objective of present study was to compare the efficacy of various chemical stabilizers on the thermostability of a 0264-410X/$ – see front matter © 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0264-410X(03)00512-7