An intranasal challenge model for testing Japanese encephalitis vaccines in rhesus monkeys.

Abstract

Abstract. Placebo-controlled field efficacy trials of new Japanese encephalitis (JE) vaccines may be impractical. Therefore, an animal model to evaluate efficacy of candidate JE vaccines is sought. Previous work has shown that exposure of monkeys to JE virus (JEV) via the intranasal route results in encephalitis. Here we report the further development of this model and the availability of titered virus stocks to assess the protective efficacy of JE vaccines. To determine the effective dose of our JE challenge virus, dilutions of a stock JEV (KE-93 isolate) were inoculated into four groups of three rhesus monkeys. A dose-dependent response was observed and the 50% effective dose (ED 50 ) was determined to be 6.0 ϫ 10 7 plaque forming units (pfu). Among animals that developed encephalitis, clinical signs occurred 9-14 days postinoculation. Infection with JEV was confirmed by detection of JEV in nervous tissues and IgM to JEV in the cerebrospinal fluid. Viremia with JEV was also detected intermittently throughout infection. Validation of the model was performed using a known effective JE vaccine and saline control. One ED 90 of virus (2.0 ϫ 10 9 pfu) was used as a challenge dose. Four of four animals that received saline control developed encephalitis while one of four monkeys administered the JE vaccine did so. This study demonstrates that the virus strain, route of inoculation, dose, and the outcome measure (encephalitis) are suitable for assessment of protective efficacy of candidate JE vaccines.Japanese encephalitis (JE) is the leading cause of mosquito-borne viral encephalitis in the world, accounting for approximately 35,000 cases and 10,000 deaths each year in Asia. The JE virus (JEV) is transmitted by culicine mosquitoes through an epizootic cycle involving primarily pigs and birds. Most infections in humans are asymptomatic. It is estimated that only one in 20 to one in 1,000 infections result in encephalitis. However, once encephalitis occurs, it is fatal in 25% of the cases with 50% of the survivors experiencing neurologic sequelae. [1][2][3] Several JE vaccines are in use. Live attenuated vaccines have been developed and licensed for use only in China. [4][5][6] A more widely used vaccine is a highly purified formalininactivated virus preparation derived from infected mouse brain. In 1984In -1985, an efficacy trial was conducted in 65,224 Thai children using monovalent (Nakayama strain) and bivalent (Nakayama and Beijing strain) mouse brain vaccines manufactured by BIKEN (Research Foundation of

Chimeric Yellow Fever Virus 17D-Japanese Encephalitis Virus Vaccine: Dose-Response Effectiveness and Extended Safety Testing in Rhesus Monkeys

“…The diversity of natural JE strains was reflected in the neutralizing antibody responses of monkeys immunized with ChimeriVax-JE expressing the E protein of a Chinese (genotype 1) virus; prechallenge neutralizing antibodies to heterologous strains were significantly lower than to the homologous vaccine and were undetectable (titer of Ͻ20) in some cases (Table 4). Postchallenge anamnestic responses to heterologous strains were not measured in this study and will be reported elsewhere; however, it is likely that these responses would be characterized by a marked broadening of the antibody response across all JE strains (7,12,26). Cross-protection between heterologous members of the JE antigenic complex has been repeatedly demonstrated (8).…”

“…challenge is intranasal (i.n.) inoculation of high virus doses, which also causes encephalitis (10,26); the i.n. route presumably leads to direct viral spread to the brain via olfactory neurons and is thus simply a delayed form of i.c.…”

Etiology of encephalitis syndrome among hospitalized children and adults in Takeo, Cambodia, 1999-2000.

“…Reverse transcription and amplification were performed for DENV according to Lanciotti and others 7 and for JEV according to Raengsakulrach and others. 8 Routine DENV and JEV assays were able to detect 10 1 tissue culture infective dose (TCID) 50 /mL and 10 1 plaque-forming units per milliliter of specimen, respectively.…”

Canarypox Virus-Induced Maturation of Dendritic Cells Is Mediated by Apoptotic Cell Death and Tumor Necrosis Factor Alpha Secretion

“…ALVAC constructs encoding foreign proteins have been shown to induce humoral and cellular immune responses against a variety of infectious pathogens. These include rabies virus (19,58), feline immunodeficiency virus (59), human immunodeficiency virus type (HIV-1) and HIV-2 (1,4,6,15,18,35,49), Japanese encephalitis virus (32,43), rabbit hemorrhagic disease virus (17), and canine distemper virus (CDV) (39,55), as well as tumor antigens (25,34,46). In fact, very recent studies revealed that mucosal application of ALVAC containing CDV genes induced high titers of neutralizing antibodies (Abs) and protection against a mucosal challenge with CDV (63).…”