Advances in research of interchangeable immunization with live attenuated Japanese encephalitis vaccines and inactivated vaccines / 中华预防医学杂志

Japanese encephalitis (JE) virus is the leading cause of vaccine-preventable encephalitis in Asia and the Western Pacific, which mainly invades central nervous system. Vaccination is the most important strategy to prevent JE. Currently, both live attenuated Japanese encephalitis vaccines (JE-L) and inactivated vaccines (JE-I) are in use. Due to the supply of vaccines and the personal choice of recipients, there will be a demand for interchangeable immunization of these two vaccines. However, relevant research is limited. By reviewing domestic and foreign research evidence, this article summarizes the current situation of the interchangeable use of JE-L and JE-I, and makes recommendations when the interchangeable immunization is in urgent need, so as to provide reference for practical vaccination and policymaking in China.

The Immunogenicity and Safety of the Live-attenuated SA 14-14-2 Japanese Encephalitis Vaccine Given with a Two-dose Primary Schedule in Children

Effective and tolerable vaccination is an essential strategy to prevent Japanese encephalitis (JE) in endemic areas. Although the live attenuated SA 14-14-2 JE vaccine (LAJEV) has been widely used since its introduction, the systemic data of LAJEV was very rarely available in Korea. We conducted the open-label, prospective cohort study to assess the immunogenicity and safety of this vaccine. Ninety subjects were enrolled, and LAJEV in a 2-dose primary series was given with a 12-month interval. Neutralizing antibody titers were measured before and after each vaccination, and active monitoring for adverse events was performed. After the first dose, 91.1% of subjects had seroprotection with a geometric mean titer (GMT) of 40.9. Seroprotection rate after the second dose was 97%, and GMT showed an increase of 6.5-fold. Most adverse events following immunization were self-limited, and no serious adverse events were reported until 42 days after each dose. The 2-dose administration of LAJEV in the primary immunization schedule appeared to be highly immunogenic and safe.

Gianotti-Crosti Syndrome Following Japanese Encephalitis Vaccination

We report a three-year-old Korean boy who presented with itching symmetrical erythematous macules and papules on his face, trunk, and extremities for 1 week. Lymphadenopathies were detected on physical examination. He was vaccinated against Japanese B Encephalitis (JE) 1 day before developing skin rashes. The patient's serum JE antibody titer by hemagglutinin inhibition (HI) test was 1:40. Under the diagnosis of Gianotti-Crosti syndrome following JE vaccination, he was conservatively treated with an antihistamine agent, and his symptoms were all cleared 2 weeks after treatment.

A field study on Nakayama and Beijing strains of Japanese encephalitis vaccines.

A field study to compare the immune response of children aged 1-6 years to Nakayama and Beijing strains JE vaccines was carried out in Mae Hong Son Province, northwest Thailand, where there was low incidence of JEV infection. The first and second dose of each vaccine was given 1-2 weeks apart and the third dose was 1 year after the second dose. Seroconversion rate was similarly high, about 94% in both groups of vaccinees. At 6 and 12 months after 2 doses of vaccines, the seroconversion rates dropped in both groups of vaccinees, so there were 10-20% of children (50-65% if cross protection was considered) susceptible to JEV infections during this period. After the third dose of vaccine, the seroconversion rate rose to 100% in both groups. The GMT in Bejing strain vaccinees were slightly higher than Nakayama strain JE vaccines. To reduce the number of susceptible children during 6-12 months after the second dose and for longer protection, the primary JE immunization should be 3 doses and the timing for the third dose should be at 6 months after the second dose. Either Nakayama or Beijing strain vaccine could be used in Thailand.

Prevalence of hemagglutination-inhibition and neutralizing antibodies to arboviruses in horses of java.

A study was conducted to measure the prevalence of hemagglutination-inhibition (HI) and neutralizing antibodies against two arboviruses (Chikungunya and Japanese encephalitis virus) in horses of Java, Indonesia. Blood specimens were collected from a sample of 112 horses at two stables: Pulo Mas, a racing track-horse complex, located in a residential area in North Jakarta, and Pamulang, a riding school, located in a rural environment of West Jaya. Sera were tested by the HI assay and plaque reduction neutralization test. JEV antibodies were detected by HI in 58 (52%) of the horses, while only 11 (10%) had Chikungunya antibodies by HI. The proportion of Pamulang horses infected with JEV (66%) was significantly higher than found among Pulo Mas horses (40%) screened (p < 0.01). Of the 58 horses with JEV antibodies by HI, 52 (90%) were found to have specific neutralization antibodies to JEV. HI and neutralization tests on horse sera indicated that the risk to alpha virus infections was minimal in horses surveyed from Java. However, there was a high risk of JEV infection among the same population.

Comparative evaluation of bioassay and ELISA for detection of Japanese encephalitis virus in field collected mosquitos.

Comparative evaluation of enzyme-linked immunosorbent assay (ELISA) and bioassay (virus isolation in Toxorhynchites splendens larvae and identification by immunofluorescence test using virus specific monoclonal antibody) was carried out in order to define a suitable strategy for monitoring Japanese encephalitis virus infection in field mosquitos. A total of 8,850 adult female mosquitos in 177 pools (Culex tritaeniorhynchus 91, Cx. vishnui 59 and Cx. fuscocephala 27) collected from an endemic area of Tamil Nadu were examined by both the techniques. In ELISA, 9 pools which had optical densities (OD) equal to the mean of normal infected pools plus > or = 4 standard deviations (SD) mean considered positive and all of them were virus positive by the bioassay also. Sixty-five pools had OD = Mean + 2-3 SD and 103 pools had OD = Mean + < 2 SD of normal pools. From these groups, 12 (18.5%) and 8 (7.8%) pools respectively were found to be virus positive by the bioassay. In total 29 (16%) pools were positive by the bioassay as against 9 (5%) by ELISA. This study demonstrated that the bioassay is sensitive for estimation of true positives and ELISA is a rapid screening system. A protocol has now been developed for surveillance in which field pools are first screened by ELISA and only those with OD = Mean + > or 2 SD are assayed in Toxorhynchites. By excluding a large majority of pools with low OD (Mean + < 2 SD), which are likely to yield to only a small percentage of true positives, the cost, time and labor involved are greatly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Biting cycles of some potential vector mosquitos of Japanese encephalitis of Assam, India.

Biting activities of five potential vector species of Japanese encephalitis (JE) were observed in a JE affected district of Assam, India. Most of the species exhibited two peak periods of biting activity, one in early hours and other around midnight. However, in case of Culex fuscocephala several peaks were observed throughout the night.

Protective effect of 6-MFA, a fungal interferon inducer against Japanese encephalitis virus in bonnet macaques.

6-MFA, an extract from the fungus Aspergillus ochraceus was administered to 8 bonnet macaques. An equal number of monkeys matched for age, sex and weight received placebo and served as controls. Twenty hours after the administration of the 6-MFA/placebo the monkeys were challenged with an Indian strain of Japanese encephalitis virus by the intranasal route. Signs and symptoms of the disease such as fever, tremors, loss of appetite, dehydration, flaccid paraplegia or quadriplegia were pronounced in all the control monkeys, while in the 6-MFA treated group only two developed symptoms. Virus could be isolated from only one of the 6-MFA treated monkeys on day 6, and from four control monkeys; one each from CSF, spinal cord, blood and from both nasal swab and blood of the fourth monkey. The appearance of HI and N antibodies in 6-MFA treated group was either delayed or completely suppressed. The results indicate that 6-MFA is a potential antiviral agent which can be used to reduce the morbidity and mortality in bonnet macaques (Macaca radiata) experimentally infected with Japanese encephalitis virus.