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Seminar 816  

Seminar:  816 

1

Speaker(s)

Nan-Ling Kuan

Topic

Development of a Inactivated Vaccine with Toxoid against Actinobacillus pleuropneumoniae

Abstract

Actinobacillus pleuropneumoniaeAP is the pathogen, causing hemorrhagic, necrotizing and fibrinous pleuropneumonia in swine. Out of 15 known serotypes of AP, serotypes 1 and 5 are the predominant strains in Taiwan. With complicated pathogenicity, ApxI is one of the important virulence factors of AP. The aim of this study was to develop multivalent inactivated vaccine supplemented with important toxins.

The vaccine was composed of 1 × 108 CFU/ml for each serotype (AP1 and AP5), 10x concentrated ApxI and adjuvant ISA 25 (O/W). The vaccine passed the safety tests in mice, and the defense index (DI) for serotype 1 and 5 were 1.3 and 1.5, respectively. In addition, the vaccine was tested for the effective dosage against AP1 in pigs. The pigs weredivided into three groups: group-1(n=3, immunized intramuscular injection. twice with 2 ml vaccine), group-2 (n=3, immunized i.m. twice with 1 ml vaccine) and group-3 as a control (n=4, immunized i.m. twice with 2 ml PBS). After challenging with 2.3x106 CFU of serotype 1, the vaccinated groups were survived until termination of the experiment, whereas the control group was died in 72 hours. Hemolysis inhibition assay and ELISA kits were used for antibody detection. One week after booster immunization, the ELISA titers of AP were ascending and the hemolysis inhibition titers were 1,280 x in both vaccinated groups. The results showed that the inactivated vaccine with toxoid ApxI provided successful protection against AP1 by two iintramuscular injections of 1 ml vaccine with 3 weeks interval.

2

Speaker(s)

Yu-Hua Shih

Topic

The safety and efficacy tests of waterfowl parvovirus tissue culture bivalent live vaccine

Abstract

Waterfowl parvovirus infection caused either by goose parvovirus (GPV) or  muscovy duck parvovirus (MDPV) infects gosling and duckling showing clinical fibrous necrotizing enteritis, stunting and short beak. In 1982 and 1989, there had been outbreaks of both GDV and MDPV infections in Taiwan, respectively, which caused a large number of deaths in geese and ducks. The viruses can be propagated well in goose and Muscovy duck embryonic eggs and their fibroblast cell cultures, but  specific pathogen-free (SPF) embryo eggs are not accessible all year round due to off their breeding seasons. For this reason, the purpose of the study is to develop the  tissue culture bivalent live vaccine to protect ducklings and goslings against both GDV and MDPV infections simultaneously in the field.

For the safety test, each of ten 1-day-old Muscovy ducklings was inoculated intramuscularly (IM) with 10 doses (107.0 TCID50) of the trial vaccine and clinical observations were carried out for 21 consecutive days. All the test ducklings showed neither clinical symptoms nor gross lesions and death during the observation period. In the efficacy study, one-day-old Muscovy ducklings, each was vaccinated with one dose of the trial vaccine via IM and their serum neutralization (SN) antibody titers  against both GDV and MDPV were reached 1:158 on 7 DPI (days post inoculation) and were beyond 1:360 on 18 DPI. In ducklings, whether vaccinated once or boosted one dose on 3, 5 or 7 DPI, their SN antibody titers could be higher than 1:32 on 7DPI. If the SN titer higher than 1:32, the vaccine can provide enough protection in duckling and gosling against virulent strains challenge. In addition, the SN antibody titers of breeder Muscovy ducks would reach beyond 1:2,560 on 10 DPI. Based on the above mentioned results, it has confirmed the vaccine not only possesses high safety and good immunity that can be used to prevent the infections the vaccine also solves the problem of acquisition for SPF goose and duck embryo eggs during the non-breeding seasons.

3

Speaker(s)

Ai-Ping Hsu

Topic

Development of a bovine ephemeral fever G protein subunit vaccine

Abstract

Bovine ephemeral fever (BEF) caused by bovine ephemeral fever virus (BEFV, rhabdovirus) is an arthropod-borne disease of cattle. In Taiwan, the first outbreak was in 1967, and since then it has occurred every 3-6 years. The febrile disease causes seriously economic impact on reduced milk production and raised cull rate in dairy and grazing industries. The current commercial killed vaccines produced in cell culture have high production cost due to low virus titers.  Based on the excellent immunogenicity and good neutralizing antibody induced by G protein, the aim of this study is to develop a BEFV G protein subunit vaccine by a baculovirus expression system. In the preliminary results, recombinant progeny baculovirus selection has been conducted, and the accurate size of G proteins have also been confirmed after expressing in infecting insect cells by the recombinant baculovirus. In addition, after   IFA (indirect immunofluorescence assay) with multiple polyclonal antisera against BEFV was performed, 3 recombinant G proteins have been selected, and immunization of these G proteins in cattle could induce neutralization antibodies. Furthermore, the G protein with 5 diverse adjuvants have been properly mixed for intramuscular injection in mice. The protective neutralization antibody titers of over 1:32 were detected and remained up to 4 months after immunization in 2 adjuvant groups. For the future study, the next task is to develop process optimization of large scale production in suspension culture and protein extraction, and then to prepare BEFV G protein subunit vaccines for safety and efficacy tests in cattle.