ZH501-VSVRI: Is it Still the Best Choice for Vaccination Against Rift Valley Fever in Egypt?
- *Corresponding Author:
- Haitham M Amer
Department of Botany and Microbiology
College of Science, King Saud University
P.O. Box 2455, Riyadh 11451
Kingdom of Saudi Arabia
E-mail: [email protected]
Received date: May 21, 2011; Accepted date: August 22, 2011; Published date: August 24, 2011
Citation: Atwa MH, El-Sabagh IM, Amer HM, Saad S, Yousif AA, et al. (2011) ZH501-VSVRI: Is it Still the Best Choice for Vaccination Against Rift Valley Fever in Egypt? J Vaccines Vaccin 2:121. doi:10.4172/2157-7560.1000121
Copyright: © 2011 Atwa MH, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
ZH501 strain of Rift valley fever virus (RVFV) was originally isolated from a human patient during the outbreak of 1977 in Egypt. This virus strain was used since 1980 for preparation of an inactivated RVF vaccine at Veterinary Serum and Vaccine Research Institute (VSVRI), Egypt. Two subpopulations of ZH501 with a single nucleotide polymorphism (A/G) at nucleotide position 847 of Gn gene of M segment have been described. This nucleotide substitution affected significantly RVFV virulence in the mouse model. In this report, the genetic makeup of the Gn gene of ZH501-VRVSI vaccine virus stock was analyzed for verification of its safety and stability. Plaque assay of the vaccine stock virus revealed the presence of two populations that produced different plaque forms. The viruses that developed large plaques resembling those produced by the virulent virus strains were isolated for genetic analysis. Comparison of the Gn gene nucleotide sequence of the isolated viruses with those of the wild-type ZH501 and other reference strains identified five nucleotide substitutions, of which three are capable to induce amino acid changes in the mature protein. Protean analysis suggested a potential change in the three dimensional structure of the Gn protein in relation to the parent strain. The results of this study throw light on the changes occurred in the master seed virus used for preparation of RVFV vaccine in Egypt. Further studies focusing on the other gene segments of ZH501-VSVRI are required to conclude is it still the best choice for vaccination against RVF in Egypt.