Reduced neutralizing antibody titer against genotype I virus in swine immunized with a live-attenuated genotype III Japanese encephalitis virus vaccine

• Published in: Veterinary microbiology Vol. 163; no. 3-4; pp. 248 - 256
• Main Authors: Fan, Yi-Chin, Chen, Jo-Mei, Chen, Yi-Ying, Lin, Jen-Wei, Chiou, Shyan-Song
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 03.05.2013
• Subjects: amino acids; Animals; antibodies; Antibodies, Neutralizing; Antibodies, Neutralizing - immunology; Antibodies, Viral; Antibodies, Viral - blood; blood; chemistry; Cross Protection; Cross Protection - immunology; Encephalitis Virus, Japanese; Encephalitis Virus, Japanese - chemistry; Encephalitis Virus, Japanese - genetics; Encephalitis Virus, Japanese - immunology; Encephalitis, Japanese; Encephalitis, Japanese - prevention & control; Encephalitis, Japanese - veterinary; genetics; Genotype; Genotype replacement; immunology; Japanese encephalitis; Japanese Encephalitis Vaccines; Japanese Encephalitis Vaccines - immunology; Japanese encephalitis virus; Live-attenuated vaccine; neutralization; piglets; prevention & control; Protective threshold; seroprevalence; structural proteins; Swine; Swine Diseases; Swine Diseases - immunology; Swine Diseases - prevention & control; Swine Diseases - virology; Taiwan; Vaccination; Vaccination - veterinary; vaccines; Vaccines, Attenuated; Vaccines, Attenuated - immunology; veterinary; Viral Envelope Proteins; Viral Envelope Proteins - chemistry; Viral Envelope Proteins - genetics; Viral Envelope Proteins - immunology; virology; viruses; Taiwan; Protective threshold; Live-attenuated vaccine; Genotype replacement; Japanese encephalitis
• ISSN: 0378-1135; 1873-2542; 1873-2542
• DOI: 10.1016/j.vetmic.2013.01.017

A shift in prevalence from Japanese encephalitis virus (JEV) genotype III (GIII) to GI virus has been observed in several Asian countries. Genotype I virus was first detected in Taiwan in 2008, and became the dominant JEV island-wide within a year. We conducted a serosurvey using swine serum specimens from multiple counties in Taiwan following the transmission season in 2009 and results showed 67–100% of JEV seropositive swine showed evidence of GI virus infection. The envelope (E) protein is a structural protein that elicits protective neutralizing antibodies (Nt Ab). The GIII at222 (a live-attenuated swine vaccine) virus E protein differs at eight amino acid residues (E-123, E-129, E-138, E-176, E-209, E-222, E-327 and E-366) from that of the GI TC2009-1 strain (isolated in Taiwan in 2009). Twenty piglets were vaccinated with two doses of at222 vaccine, and serum specimens were collected to evaluate the strain-specific Nt Ab titer against GIII at222, GIII CJN, and GI TC2009-1 viruses. Seropositivity rates (Nt Ab titer≥1:10) and geometric mean titers (GMT) were similar against at222 and CJN viruses. However, sera from swine vaccinated with at222 were least potently neutralizing against GI TC2009-1 virus. The estimated protective threshold against GI virus was observed only when the PRNT50 against at222 virus was ≥1:320. Thus, our current study indicates that the live-attenuated at222 swine vaccine can be partially protective against GI virus, and suggests that the efficacy of GIII swine vaccines currently used may require a comprehensive reevaluation in the field.