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PubMed2005

[Evaluation of mouse brain-derived, inactivated Japanese encephalitis vaccine].

Japanese encephalitis (JE) is a serious encephalitis caused by JE virus. Approximately 20% of JE patients die and 50% patients recover with neuro-psychiatric sequelae. In Japan, the number of JE patients was over 1000 per year in 1960s; however, the number decreased dramatically and has been less than 10 since 1990. Ministry of Health, Labour and Welfare suspended the strong recommendation for vaccination with the mouse brain-derived JE vaccine, because of cases who developed acute disseminated encephalomyelitis (ADEM) after vaccination with JE vaccine. However, it has not been fully confirmed on scientific bases that ADEM was caused by mouse brain-derived JE vaccine. Tissue culture derived-JE vaccine is under development. It is expected that this new vaccine will come to the market soon and that the recommendation of universal vaccination with JE vaccine will be implemented at the earliest occasion.

Animals↗
PubMed1997

Allergic mucocutaneous reactions to Japanese encephalitis vaccine.

Japanese encephalitis (JE) vaccine has been used in childhood immunization programmes in Asia for many years. Also travellers from other parts of the world have been vaccinated before travelling in Asian countries. Recommendations for the use of JE vaccine are still debated because severe cases of adverse reactions have been reported. In Denmark an inactivated JE vaccine derived from infected mouse brain has been used and 350000 doses have been distributed from the Statens Serum Institut since 1983. In the period 1983-1995, 101 adverse reactions after JE vaccination have been registered including 73 allergic mucocutaneous reactions. These reactions have occurred each year since 1989 with frequencies varying from 1-17 per 10,000 vaccinees. The highest frequencies and the most serious reactions acquiring hospitalization were seen in the period 1989-1992. Three batches (EJN 012, 033 and 048) distributed before 1992 caused the highest number of reactions but all batches delivered in Denmark since 1989 have caused reactions. Therefore, it is still very important to collect information on adverse events as well as information of the risk of acquiring JE infection in order to give sound recommendations to travellers.

Adult↗
PubMed2000

Case-control study of allergic reactions to Japanese encephalitis vaccine.

Japanese encephalitis (JE) vaccine is widely used in Asia for childhood immunizations, but the vaccine is also used for travellers to Asia from other parts of the world. In Denmark, more than 400,000 doses have been distributed from Statens Serum Institut since 1982. In 1989, the first allergic mucocutaneous reactions after JE vaccination were registered in Denmark and, although the number of reactions have decreased since 1992, reactions are still observed. No explanation of these reactions have been found. The present case-control study, including 49 travellers with allergic reactions and 148 travellers without similar reactions after JE vaccination was performed in order to clarify any possible risk factors. About one third of the adverse reactions to the vaccine could be attributed to an allergic predisposition in the vaccinees. The main risk factors were young age, female gender and previous allergic skin reactions or hayfever. The study also indicated that cases more often reacted to nickel and more often had severe edema after mosquito or other insect bites. Hormone intake was more often spontaneously reported by females in the case group. Accordingly, information on any history of allergy in young adults should be given before JE vaccination, the vaccination should be carried out more than a week before departure and antihistamine treatment should be available if a reaction occurs.

Adolescent↗
PubMed1997

A Cluster of Severe Reactions Following Improperly Administered Takeda Japanese Encephalitis Vaccine.

Japanese encephalitis (JE) is an infection caused by a mosquito-transmitted virus present in many parts of Asia, including India, and Oceania. Infection is usually asymptomatic, leading to overt encephalitis in only 0.1-5% of infected individuals. When encephalitis occurs it is usually severe, with a 25% fatality rate, and 30% of cases resulting in permanent neurologic deficiencies. Since 1981, eight cases of JE have occurred in United States (U.S.) military personnel and their dependents stationed overseas.1 JE vaccine manufactured by Biken (Research Institute for Microbial Diseases, Osaka, Japan) is given to certain military personnel assigned to endemic areas in Asia. Concern about vaccine-associated hypersensitivity reactions has limited more widespread use. We report three cases of severe hypersensitivity following JE vaccination with a non-Biken JE vaccine (Takeda) under unusual circumstances.

Journal Article↗
PubMed2000

Immunogenicity and protective efficacy of the current inactivated Japanese encephalitis vaccine against different Japanese encephalitis virus strains.

Mouse brain-derived, inactivated Japanese encephalitis (JE) vaccine has been internationally used for many years. It is believed that this vaccine made a great contribution to the reduction of JE patients in several countries. Mouse brain-derived, Beijing-1 and Nakayama JE vaccines induce high levels of neutralizing antibodies. High levels of induced antibodies are maintained at least for 3-4 yr. The induced antibodies are cross-reactive to heterologous strains; however, the neutralizing antibody titers against heterologous strains are usually lower than those against homologous strains. Considering that both Nakayama and Beijing-1 JE vaccines showed high levels of protective efficacy in Taiwan and Thailand where strains other than Nakayama and Beijing-1 were circulating, we conclude that the current inactivated JE vaccine can induce high levels of protective immunity against heterologous JE virus strains.

Animals↗
PubMed1986

Enzyme-linked immunosorbent assay for detection of serum antibody in children vaccinated with Japanese encephalitis vaccine.

Serum antibodies in children who had been vaccinated with Japanese encephalitis (JE) vaccine were measured by enzyme-linked immunosorbent assay (ELISA) and neutralization (N) and hemagglutination-inhibition (HI) tests. Of 20 serum samples obtained after two shots of JE vaccine in the first year, all but one showed positive titers in the ELISA and N test, but five showed negative titers in the HI test. All 12 serum samples obtained after booster immunization with JE vaccine in the second year showed positive and considerably higher titers in all three tests. Moreover, a high correlation was found between the ELISA, N and HI titers. These results indicate that the ELISA is useful for detecting antibodies in subjects immunized with JE vaccine.

Antibodies, Viral↗
PubMed1995

Australian Case-Control Study of Adverse Reactions to Japanese Encephalitis Vaccine.

Background: Japanese encephalitis (JE) is widely distributed in Asia and is the world's most common aborviral encephalitis. An effective vaccine against JE has been used in Asia for decades without reports of serious adverse reactions. Since 1989, an apparent increase in frequency of allergic reactions to JE vaccine has been reported from a number of nonendemic countries, including Australia. The objective of this study was to evaluate possible risk factors for allergic reactions associated with Japanese encephalitis (JE) vaccine. Methods: A case-control study was carried out in Australia. Subjects were persons who had developed an allergic reaction (rash and/or edema) that had occurred within 1 week of a dose of Biken JE vaccine. All cases had been reported to the Australian Adverse Reactions Advisory Committee, and all could be accessed for purposes of this study. Three matched controls were recruited for each of five cases. Participants completed a questionnaire and had venous blood drawn. Results: Cases were significantly less likely than controls to give a history of contact with dogs (Fisher's exact test p =.03); were more likely than controls to have received other immunizations in the 1-9 days prior to, rather than on the same day, as the JE vaccine (chi-square test for independence p =.015); and were more likely than controls to have consumed more than usual quantities of alcohol in the 48 hours following the last dose of JE vaccine (Fisher's exact test p =.034). Conclusions: We recommend, where possible, that JE vaccine be administered concurrently with other vaccines, that recipients be advised to avoid more than usual alcohol intake after receiving JE vaccine, and that active surveillance of adverse events associated with JE vaccine be conducted.

Journal Article↗
PubMed1987

Effect of current Japanese encephalitis vaccine on different strains of Japanese encephalitis virus.

Inactivated Japanese encephalitis (JE) vaccine was given to healthy children and their neutralizing antibody titres against nine JE virus strains were measured. After two shots of the vaccine in the first year, most of the children showed seroconversion, but their neutralizing antibody titres were not high, and one year after vaccination their titres had decreased to low levels. However, a booster dose of vaccine in the second year had a marked effect on the antibody response. The neutralizing antibodies induced by the vaccine reacted to almost the same extent with nine different JE virus strains, though significantly higher titres against the Nakayama strain, the vaccine strain, were observed after vaccination in the second year.

Antibodies, Viral↗
PubMed2006

Dengue tetravalent DNA vaccine increases its immunogenicity in mice when mixed with a dengue type 2 subunit vaccine or an inactivated Japanese encephalitis vaccine.

We previously developed a dengue tetravalent DNA vaccine that can induce neutralizing antibodies against four dengue viruses in mice. Here, we demonstrated that immunogenicity of our tetravalent vaccine is synergistically increased in mice by co-immunization with dengue type 2 virus (DENV2) subviral extracellular particles (D2EPs) or inactivated Japanese encephalitis vaccine (JEVAX). A single immunization with a mixture of 100 microg of the tetravalent vaccine and 150 ng of D2EPs or a 1/10 dose of JEVAX induced moderate levels of neutralizing antibodies in a 90% plaque reduction assay. Immunized mice were protected from "artificial" viremia created by intravenous injection with DENV2.

Animals↗
PubMed1996

Adverse reactions to Japanese encephalitis vaccine in travellers.

Vaccination against Japanese Encephalitis (JE) has been carried out extensively in many Asian countries for the past 20 years. The vaccine was generally considered to be effective and of low reactogenity. However, since 1989 an unusual number of systemic reactions characterized mainly by generalized urticaria and/or angioedema following JE vaccination were reported from Australia, Canada and Denmark, 860 travellers were recruited during a period of 16 months for a prospective study with the aim to investigate the type and incidence of side effects following JE vaccination (JEV) in German travellers. 826 received a primary immunization (2 injections at days 0 and 7-14) and 34 received a single booster injection. A detailed standardized questionnaire was distributed to all vaccinees after the first injection. A total of 509 questionnaires could be evaluated, which represents a return rate of 59.2%. 46% of the vaccinees reported about no adverse events at all. 54% reported about one or more adverse effects. Local reactions at the injection site were observed by 209 vaccinees, while 65 reported about systemic side effects like headache, fever, dizziness and generalized rash. There was no significant difference following first or second injection of the primary immunization or the booster injection, respectively, regarding incidence, severity or type of side effects. 2.2% of the vaccinees reporting reactions sought medical advice and 1.8% were judged unfit for work for an average of 2.2 days. The amount of systemic reactions might indicate a potential hazard of serious anaphylactic reactions. Unlike hepatitis A. Japanese encephalitis is an extremely rare disease in travellers. Therefore, the risk of acquiring the disease when travelling to affected areas without prior immunization should be considered against the risk of developing serious side effects after vaccination. We conclude that JEV should remain restricted to travellers with an increased risk of acquiring JE.

Adolescent↗
PubMed2025

Key virulence factors responsible for differences in pathogenicity between clinically proven live-attenuated Japanese encephalitis vaccine SA14-14-2 and its pre-attenuated highly virulent parent SA14.

Japanese encephalitis virus (JEV), a neuroinvasive and neurovirulent orthoflavivirus, can be prevented in humans with the SA14-14-2 vaccine, a live-attenuated version derived from the wild-type SA14 strain. To determine the viral factors responsible for the differences in pathogenicity between SA14 and SA14-14-2, we initially established a reverse genetics system that includes a pair of full-length infectious cDNAs for both strains. Using this cDNA pair, we then systematically exchanged genomic regions between SA14 and SA14-14-2 to generate 20 chimeric viruses and evaluated their replication capability in cell culture and their pathogenic potential in mice. Our findings revealed the following: (i) The single envelope (E) protein of SA14-14-2, which contains nine mutations (eight in the ectodomain and one in the stem region), is both necessary and sufficient to render SA14 non-neuroinvasive and non-neurovirulent. (ii) Conversely, the E protein of SA14 alone is necessary for SA14-14-2 to become highly neurovirulent, but it is not sufficient to make it highly neuroinvasive. (iii) The limited neuroinvasiveness of an SA14-14-2 derivative that contains the E gene of SA14 significantly increases (approaching that of the wild-type strain) when two viral nonstructural proteins are replaced by their counterparts from SA14: (a) NS1/1', which has four mutations on the external surface of the core β-ladder domain; and (b) NS2A, which has two mutations in the N-terminal region, including two non-transmembrane α-helices. In line with their roles in viral pathogenicity, the E, NS1/1', and NS2A genes all contribute to the enhanced spread of the virus in cell culture. Collectively, our data reveal for the first time that the E protein of JEV has a dual function: It is the master regulator of viral neurovirulence and also the primary initiator of viral neuroinvasion. After the initial E-mediated neuroinvasion, the NS1/1' and NS2A proteins act as secondary promoters, further amplifying viral neuroinvasiveness.

Animals↗
PubMed1998

[Production of purified Japanese encephalitis vaccine from Vero cells with roller bottles].

OBJECTIVE: To study the production process of purified Japanese encephalitis (JE) vaccine from Vero cells cultivated in roller bottles to improve the quality of JE vaccine. METHODS: The 15 L roller bottles were used for propagation of Vero cells and JE virus, then the virus was inactivated, concentrated, treated by protamine sulphate, purified by sucrose gradient density centrifugation and lyophylized as final product. RESULTS: Three batches of high quality lyophylized vaccine were produced and the quality control tests of vaccine for human use had been passed. CONCLUSION: Using roller bottles to cultivate continuous cell line-Vero cells for JE vaccine production is feasible.

Animals↗
PubMed2005

[Development of new Japanese encephalitis vaccine].

We have developed the new inactivated Japanese encephalitis vaccine derived from virus-infected Vero cells cultured on microcarriers. The safety and effectiveness of this new vaccine were compared with those of current mouse-brain-derived vaccine that have some intrinsic demerits such as possible contamination of adventitious agents. The results of pre-clinical and clinical trials suggested that the safety and effectiveness of new vaccine are approximate equivalent to those of currently conventional vaccine in humans and animals, and that the availability of Vero cell-derived vaccine is anticipated.

Animals↗
PubMed1997

Japanese encephalitis vaccine in travellers. Is wider use prudent?

Vaccination against Japanese encephalitis has been carried out extensively in many Asian countries for the past 20 years and is also increasingly recommended for travellers to endemic areas. Although the currently available vaccine, manufactured from mouse brain, is generally considered to be highly effective and of low reactogenicity, approximately 50% of vaccinees report experiencing usually mild adverse effects following vaccination. Concern has been raised regarding potential neurological adverse effects but the incidence of such effects appears to be very low (around 1 to 2.3 per 1000000 vaccinations). Routine vaccination of all travellers to endemic areas is clearly not beneficial at this moment and use of the vaccine should remain restricted to persons spending a month or longer in endemic areas, especially rural areas, during the transmission season. However, when counselling individual travellers, it has to be kept in mind that the possibility of Japanese encephalitis can never be ruled out completely when travelling to endemic areas, and that such an infection can prove disastrous for the individual concerned.

Animals↗