Live vaccine against contagious ecthyma of sheep - prepd. from virus attenuated by passaging on foetal skin cells

摘要

Live viral vaccine against contagious ecthyma of sheep comprises the attenuated viral strain 'L-1' (deposition number 8). This is isolated from the infected areas of the skin of a lamb and adapted by repeated passages on a primary culture of sheep foetal skin cells. Esp. 10-20 passages on cells from a 3-3.5 month old foetus are carried out at 36-37 deg.C. The attenuated strain is grown on cells of 3-month old sheep foetal skin at 36 deg.C. pref. using medium N199 contg. 2% bovineserum for maintenance. Particularly the virus contg. material is first harvested when 50-70% of the cells are infected and the second harvest is taken 24-36 hrs. later. This vaccine is highly immunogenic, safe and free from contaminating viruses. The attenuated strain can be grown on readily available substrates and provides immunity (which lasts for at least 9 months) against a wide range of epizootic viral strains.