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Neutralizing antibody responses to Japanese encephalitis vaccine in children
Insights
Two doses of the Japanese encephalitis (JE) vaccine stimulate robust antibody responses to the Nakayama strain, but slightly lower responses to wild JE virus strains JaGAr-01 and E-50.
Area of Science:
- Virology
- Immunology
- Vaccinology
Background:
- Japanese encephalitis (JE) is a serious mosquito-borne viral disease prevalent in Asia.
- The current JE vaccine is based on the Nakayama strain.
- Understanding immune responses to wild JE virus strains is crucial for vaccine efficacy.
Purpose of the Study:
- To evaluate the immune response in children after two doses of the current JE vaccine.
- To compare the neutralizing antibody responses to the vaccine strain (Nakayama) and two wild strains (JaGAr-01, E-50).
Main Methods:
- Children received two doses of the JE vaccine.
- Neutralizing (N) antibody titers were measured against Nakayama, JaGAr-01, and E-50 strains.
- Seroconversion rates were calculated after the second vaccination.
Main Results:
- High seroconversion rates (100% for Nakayama, 99% for JaGAr-01, 97% for E-50) were observed after two doses.
- Geometric mean titers (GMT) were highest for the Nakayama strain (2.89) compared to JaGAr-01 (1.87) and E-50 (1.75).
- Antibody responses to wild strains were lower than to the vaccine strain, with some individuals showing no seroconversion after the first dose.
Conclusions:
- Two doses of the current JE vaccine are necessary for effective immune responses against wild JE virus strains.
- While the vaccine induces broad protection, responses to wild strains are less potent than to the vaccine strain.
- Further evaluation may be needed to optimize vaccine strategies against circulating wild JE virus strains.
Abstract:
Two shots of the current Japanese encephalitis (JE) vaccine were given to children and their immune responses to the Nakayama strain (the vaccine strain) and two wild strains (JaGAr-01 and E-50) of JE virus were examined by neutralizing (N) antibody titrations. Seventy vaccinees had no N antibody to JE virus before the first vaccination and were bled one month after the second vaccination. The N antibody responses to the JaGAr-01 and E-50 strains were found to be similar and to be less than that to the Nakayama strain after the second vaccination: the geometric mean titers (GMT) of N antibodies to the JaGAr-01 and E-50 strains (as logarithms) were 1.87 and 1.75, respectively, while the GMT to the Nakayama strain was 2.89. The seroconversion rates to the Nakayama, JaGAr-01 and E-50 strains were 70/70 (100%), 69/70 (99%) and 68/70 (97%), respectively, after the second vaccination. Twenty-seven of the 70 vacciness were also bled before the second vaccination. Most of them showed a considerably high N antibody response against the Nakayama strain and only one vaccinee failed to show seroconversion after the first vaccination. However, the antibody response to the E-50 strain appeared to be rather low and 9 of 25 vaccinees did not show any seroconversion. Similarly 3 of 25 failed to show any seroconversion against the JaGAr-01 strain. These results indicate that at the initial immunization two shots, at least, of the current JE vaccine are necessary to stimulate effective immune responses to wild strains of JE virus.