204 Pakistan Veterinary Journal ISSN: 0253-8318 (PRINT), 2074-7764 (ONLINE) Accessible at: www.pvj.com.pk Serum Neutralization Titers and Protective Efficacy Induced by Foot and Mouth Disease Virus Inactivated Vaccine with different 146S Particles Concentrations in Cattle Abdel-Hamid I. Bazid 1* , Wagdy R El-Ashmawy 2 and Magdy El-Sayed 2,3 1 Department of Virology, Faculty of Veterinary Medicine, University of Sadat City; 2 Department of Internal Medicine and Infectious Diseases, Faculty of Veterinary Medicine, Cairo University; 3 Middle East for Veterinary Vaccines, Second Industrial Area, El-Salhya El-Gedida, El-Sharqia, Egypt *Corresponding author: abdelhameed.mousa@vet.usc.edu.eg; Bazid1976@yahoo.com ARTICLE HISTORY (15-245) ABSTRACT Received: Revised: Accepted: Published online: May 13, 2015 December 17, 2015 December 31, 2015 March 11, 2016 Foot and Mouth Disease (FMD) vaccine evaluation required viral challenge of vaccinated cattle. Difficulties of potency testing include finding animals FMDV antibodies free and the challenge should be conducting in high containments. Alternative approaches, such as Serum Neutralization Test (SNT) and antigen concentration (146S) were developed. In this study, antigen dose, SNT, and animal challenge were evaluated after a single dose. Three vaccine batches with different antigen doses of inactivated trivalent FMD vaccine prepared from Egyptian strains (serotypes A, O, and SAT2) were evaluated. Calves 6-8 month old were vaccinated with 2ml of the vaccine, sera collected at 28 days post vaccination and animals were challenged with 10 4 BID50 of homologous FMDV strains via intra-dermolingual route. All the antigen doses induced SN protective titers with the exception of one animal in each of the serotype O batch-2 (3.1μg/dose) and serotype SAT2 batch-1 (2.7μg/dose) which showed 0.9 log10 SN titers. All animals were completely protected against challenge with serotype A in all tested batches. Serotype O batch- 1 and 3 (2.5 and 5μg/dose) induced a complete protection; however, batch-2 (3.1μg/dose) showed 80% protection. In serotype SAT2 challenge, the lowest dose of 2.7μg/dose showed 80% protection meanwhile other doses of 3.3 and 5.4μg/dose completely protected the animals. In both serotypes O and SAT2, feet lesions were observed in the calves that showed the lowest SNT levels (0.9log10). In conclusion, the study results indicate that 146S particles concentration (3.3, 2.5 and 1.4 μg) for serotypes SAT2; O and A, respectively can be used for vaccine formulation. Additionally, both SNT and 146S particles concentration could be suggested as an alternative method for vaccine evaluation. ©2015 PVJ. All rights reserved Key words: 146S content Challenge FMDV SNT Vaccine To Cite This Article: Bazid AI, El-Ashmawy WR and El-Sayed M, 2016. Serum neutralization titers and protective efficacy induced by foot and mouth disease virus inactivated vaccine with different 146S particles concentrations in cattle. Pak Vet J, 36(2): 204-208. INTRODUCTION Foot and Mouth Disease (FMD) is an economically devastating disease of livestock. Although, vaccines are available since 1900s, the FMD inactivated vaccines still used for FMD eradication from parts in the world, the disease still affecting millions of animals around the world. The FMD remains a major economic concern for livestock-health in endemic countries and a continued threat to disease free countries (Boklund et al., 2013) and remains the main sanitary barrier to commerce of animals and animal's products (Depa et al., 2012; Ashfaq et al., 2015; Jamil et al., 2015; Zhang et al., 2015). Foot and Mouth Disease virus (FMDV) is a small positive sense ssRNA virus (approx. 8.3kb) which belongs to the aphthovirus genus of the family picornaviridae (Belsham, 1993). There are seven antigenically distinct serotypes of FMDV (A, O, C, Asia 1and South African Territories (SAT) types 1-3) and each serotype has many subtypes. This antigenic variation creates a major problem for the control of FMD as infection or vaccination with one serotype does not protect against other serotypes and may fail to protect fully against other subtypes within the same serotype (Paton et al., 2005). There are three types of viral protein in the harvest of FMDV infected BHK- 21cells: i) the infective 146S virus particles, comprising one molecule of ssRNA and 60 copies of each of four RESEARCH ARTICLE