Innocuity of a commercial live attenuated vaccine for epizootic hemorrhagic disease virus serotype 2 in late-term pregnant cows. Issue 12 (14th March 2016)

• Record Type: Journal Article
• Authors: Spedicato, Massimo; Carmine, Irene; Teodori, Liana; Leone, Alessandra; Portanti, Ottavio; Marini, Valeria; Pisciella, Maura; Lorusso, Alessio; Savini, Giovanni
• Is Part Of: Vaccine. Volume 34:Issue 12(2016)
• Page Start: 1430
• Page End: 1435
• Publication Date: 2016-03-14
• Subjects: Epizootic hemorrhagic disease virus serotype 2 -- Pregnant cows -- Transplacental transmission -- Vaccine safety -- Live attenuated vaccines; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2016.02.003
• Languages: English
• ISSNs: 0264-410X

Abstract

Abstract : Highlights: The capability to cross the placental barrier is a well-known feature of some lab adapted, including vaccines, strains of Bluetongue virus. We tested the innocuity of the live attenuated vaccine strain used in Japan to control the virulent EHDV-2 Ibaraki virus. The vaccine has been shown to be immunogenic in vaccinees and it did not pass the placental barrier. Viremia in dams was absent and calves did show neither viral RNA nor infectious virus in the blood samples. The recent Ibaraki outbreak in Japan (2013) was not related to the spread of the vaccine strain in the environment. Abstract: Epizootic hemorrhagic disease (EHD) is an arthropod-borne infectious viral disease sustained by the epizootic hemorrhagic disease virus (EHDV). The only commercially available and currently used vaccines are manufactured for EHDV-2 in Japan, either live or inactivated vaccines. In this study we tested the innocuity for fetuses of the live attenuated EHDV-2 vaccine in five late-term pregnant cows. Whole blood and serum samples were collected from dams and screened for the presence of EHDV-2 RNA, infectious virus and antibodies. After calving, whole blood and serum samples collected from calves, before and after colostrum intake, were also tested for antibodies and for virus detection. In dams, neither fever nor clinical signs were observed. All of them seroconverted and a strong humoral response was detected throughout the sampling period. All blood samples tested negative for EHDV-2 except for one sample collected from a dam 11 days post-vaccination which tested positive at virus isolation at the third cell passage following two rounds of blind passages. Although they had free access to colostrum, calves tested serologically negative for EHDV-2 during the entire course of the experiment. Overall, the tested live attenuated vaccine can be safely administered to late-term pregnant cows as it was not demonstrated to cross the placental barrier. The safety of the live-attenuated vaccine is further confirmed by the emergence of Ibaraki virus in 2013 in Japan which is apparently not related to the spread of the vaccine strain currently used in Japan.