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Seminar 824  
Date:2013-04-10
Update:2014-08-12

 

Seminar:  824

1

Speaker(s)

Chia-yi Chang

Topic

Identification of Antigenic Epitopes at the Domains D/A and the C-terminal Region of CSFV E2 Glycoprotein

Abstract

Envelope glycoprotein E2 of classical swine fever virus (CSFV) is the major antigen that induces neutralizing antibodies in infected pigs. Previous studies revealed that most epitopes are present in the N-terminal half of E2. However, studies of antigenicity beyond the B/C domains remain limited. In this study, antigenicity among various subgroups of E2 glycoprotein of CSFV was analyzed by expression of several truncated or mutated E2 proteins of various CSFV strains using baculovirus system and tested for their reactions to a panel of monoclonal antibodies (mAbs) against CSFV. Our study revealed that conformational epitopes were present on the domains D/A as well as the proximal C-terminal of E2, since the mutation of cysteine abrogated their bindings to mAbs. Substitutions of cysteines in domains D/A not only abrogated the binding to mAbs directed to D/A, but also affected the binding of the downstream C-terminal region to its specific mAbs, suggesting a close interaction between the two conformational epitopes. Mutations on the five proximal cysteines in the C-terminal region only affected the binding to its specific mAbs binding sites. In addition, mutation on the three distal C-terminal cysteines resulted in loss of E2 homodimerization. This study demonstrates new antigenic epitopes on domains D/A and C-terminal of E2 that have not been reported before, and that the nine cysteines in the C-terminal function differently in either maintaining the antigenic structure or in intermolecular dimerization of E2.

2

Speaker(s)

Sue-Min Huang

Topic

Application an Inactive Iridovir

Abstract

Grouper iridovirus (GIV) is one of the major viral pathogens that infects grouper aquaculture. The iridovirus isolates from Taiwan could be divided into 3 major genotypes that were related to GIV, red sea bream iridovirus (RSIV) and infectious spleen and kidney necrosis iridovirus (ISKNV), respectively. Manufacturing license has been received in November 2012 for an inactive vaccine against GIV. To promote immunization program, one million injection doses of vaccine were producted and offered freely for farmers. The immunization program launched in October 2011 has been used 788,000 doses of vaccine in the field. The vaccine has been used in field trials to assess the safety and efficacy in orang-spotted grouper (Epinephelus coioides) for two years. The vaccinated fish showed an increase in the survival rates by 20-30% compared to non-vaccinated fish 1 year post vaccination, and those weight were significantly higher than the non-vaccined groups 6-8 weeks post vaccination. In addition, the vaccine used in giant grouper (Epinephelus lanceolatus) under clean field conditions showed 100 survival rates both in vaccinated and non-vaccinated fish groups, but the weight was significantly higher than the non-vaccine groups 8 weeks post vaccination. The survival rates were up to 90% in downstream farms. The results showed that the tested vaccine protects against iridoviruses in grouper cultured in field conditions that it is safe for use in the target species.

3

Speaker(s)

Min-Shiuh Lee

Topic

Molecular Characterization of H5N2 Avian Influenza Viruses Isolated in Taiwan in 2012

Abstract

Avian influenza (AI) is a highly contagious disease caused by the type A influenza virus, which has many subtypes with respect to two surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA) (16). Sixteen HA (H1–H16) and nine NA (N1–N9) subtypes have been identified (10). All of the influenza virus subtypes are found in aquatic birds, which serve as the primordial reservoir of the influenza A viruses. Among 16 HA subtypes, only H5 and H7 are highly pathogenic in poultry.

This article reports the genetic characteristics of H5N2 avian influenza viruses isolated in Taiwan between 2004 and 2012. Genetic analysis of the eight segments of the isolate indicated that these isolated virus was a reassortant whose HA and NA gene segments belonged to the American lineage and internal genes to the Eurasian lineage. In particular, with the evolution of the virus, resulting in the hemagglutinin protein cleavage site motifs appear -REKR*GLF, -RKKR*GLF and -RRKR*GLF.