Improved quality control protocol for fowl pox virus vaccines based on the use of PCR and sequence analysis to detect REV and ALV as contaminants

ABSTRACT

In the present study, twenty one Fowl pox virus [FPV] vaccines were collected in the period between 2003-2005 and tested using the currently used and an improved quality control protocols. Results of currently used quality control protocol revealed negativity of all tested vaccines for the presence of contaminants and the results were satisfactory. Using PCR to detect Reticuloendotheliosis virus [REV] as contaminant in such vaccines revealed negative result except one suspected contaminated vaccine. Inoculation of this vaccine in egg, chicken embryo fibroblasts [CEFs], Specific pathogen free [SPF] chicks for three passages and testing of samples collected from inoculated host revealed positive amplification using REV specific primers. Sequence analysis of the obtained amplification fragment for REV revealed its negativity and confirmed the non specific amplification of such primers which were previously published in several PCR studies for REV. Using avian leucosis virus [ALV] sets of primers to detect groups A, B, C, D and J in a PCR reaction revealed positive amplification of ALV fragment and confirming the contamination of tested vaccine with ALV. The study proposes the importance of using PCR followed by sequence analysis of the amplified product to confirm the contaminations fonnd in the FPV vaccines