Lyophilized turkey herpesvirus (HVT): Stability of vaccine and minimum protective dose

Abstract

SUMMARYThe research reported showed that: the stability of cell-free HVT vaccine, Iyophilized and sealed under vacuum, is very high: after one year at 4°-6°C and after 10 days at 37°C the titre decreased only about 0.4 log 10 ; the stability of the vaccine, when reconstituted for use in the diluent (sucrose-phosphate buffer), is high (80%) for at least 2 hours; the degree of protection, found in 3 tests, was about 90% with an inoculum of 20 to 100 pfu, and the PD 50 was 4.9 pfu of virus per chick.

Differential effect of maternal antibodies on efficacy of cellular and cell‐free Marek's disease vaccines

“…Exposure of this flock to MD virus is presumed but cannot be proved. These neutralising titres are similar to those for 1-day-old chicks reported by Zanella et al (1974), Yoshida et al (1975), and Basarab and Hall (1976); however, neutralising titres may vary among flocks, and we have no assurance that the neutralisation assays used by different laboratories are equally sensitive. We have no reason to believe, however, that the antibodies in the chicks used in these studies were abnormal in titres or type; consequently, we feel that these chicks should be representative of chicks from HVT-immunised commercial breeding flocks.…”