HOMOLOGOUS AND HETEROLOGOUS NEUTRALIZATION ANTIBODY-RESPONSES AFTER IMMUNIZATION WITH JAPANESE ENCEPHALITIS VACCINE AMONG TAIWAN CHILDREN

Because 21 immunized children (13%) among the 162 confirmed Japanese e ncephalitis (JE) cases during 1986-1991 occurred in Taiwan, we collect ed 320 serum samples from Taiwan children aged 15-31 and 27-44 months immediately before the Ist dose (n = 41) and 1-3 months after the 2nd dose (n = 78, 27 pairs), and immediately before (n = 58) and 1-3 month s after the 3rd dose (n = 143, 44 pairs) to determine neutralization a ntibody (Nt Ab) against the Nakayama (N) and Beijing-l (B) strains and two Taiwan wild type JE viruses (JEV): CC-27 and CH-1392. Our Nt resu lts showed that (1) B vaccine stimulated a better homologous Ab respon se than N vaccine for Nt Ab seropositivity rate (NASR), produced a hig her level of Nt titer after the primary immunization [2 doses = 100% v s. 91%, geometric mean titer (GMT) = 115 vs. 22], had a greater booste r effect (3 doses: 100% vs. 95%; GMT = 320 vs. 33), and showed a bette r capability to neutralize two local Taiwan JEV strains, particularly only after 3 doses (ave. NASR for B vs. N = 90% vs. 10%; and GMT for B vs. N = 154 vs. 1); (2) the two wild type JEV strains had different p laque morphology and antigenic variation and the CC-27 strain was not neutralized as well as the CH-1392 strain after 3 doses of vaccine (BB B or NNN or NNB); and (3) 30% of the children had lost JEV Nt Ab one y ear after the 2nd dose of N vaccine and natural infection with JE viru s did occur among those children after immunization. In conclusion, (1 ) three doses of mouse-brain vaccine are the minimum requirement to pr otect children against the local Taiwan JEV; (2) the best strain for a JE vaccine depends on level of Nt Ab it induced, the molecular epidem iology and antigenic variation of the JEV in each local area; and (3) future vaccine must produce better B- and T-cell memory. (C) 1994 Wile y-Liss, Inc.