Improving Thermostability of A Candidate Live Attenuated Camelpox Vaccine

Abstract

The main focus of this work was to determine the effect of serial passage of camelpox virus on thermostability, as well as to select a thermostable derivatives of the vaccine strain. First, the virulent, passage 50 and passage 100 strains were stored at 37, 4 and – 20°C for up to 90 days. The stability of the viral strains was tested, marked reduction of viral infectivity was noticed. Similar results were obtained during incubation at 4 and –20°C, while all strains completely lost infectivity at 37?C within 30 days. It seemed that thermostability was affected during viral attenuation. Secondly, the vaccine virus was subjected to extreme heat selection at 56?C for increasing time (10-50 min) for nine passages aiming at improving the heat stability. Thermostability testing at 56?C for 30 and 60 min showed that treated vaccine lost 2 to 4 log10 , while original vaccine virus lost 3 to 5 log10 of the infectivity titer. Improving thermostability would give the vaccine adequate short-term stability at non-freezing temperatures to support manufacturing, short-term shipping and storage and significantly enhance its utility in the control of a camelpox outbreak. *Corresponding Author