VIRAL INFECTION IN BATS 



maintained at room temperature were transferred to the cold room 

 on the 42nd day, and blood specimens were obtained one month later. 

 Persistence of antibody was observed in 5 bats, but in each instance 

 agglutinin titer dropped. Bats kept in simulated hibernation for 42 

 days were transferred to room temperature and one month later (or 

 72 days after initiation of the experiment) blood samples were ob- 

 tained. Although no additional antigen was administered upon trans- 

 fer to room temperature, 6 of 10 animals uniformly negative after 30 

 days in the cold possessed agglutinating antibody one month after 

 transfer to the warm room. Presumably, antigen persisted during 

 hibernation. 



Several studies have been made to determine the immune response 

 of big brown bats experimentally infected with Japanese B encepha- 

 litis virus and held at room temperature or in simulated hibernation 

 for extended periods. Results indicate an extremely close associa- 

 tion between the cessation of viremia and the appearance of detect- 

 able neutralizing antibody. Even virus may be detected in low titer in 

 blood samples containing neutralizing antibody. Also, preliminary 

 studies indicate that bats experimentally infected with this virus 

 do not regularly produce antibodies detectable by the complement 

 fixation (CF) and hemagglutination- inhibition (HI) techniques cur- 

 rently in use. Experiments designed to study the antibody response 

 to the hibernating bat and the fate of any neutralizing antibody pre- 

 sent in the animals entering hibernation indicate that antibody is 

 produced by bats kept at room temperature, while none is detectable 

 in those held in the cold. As in the case with the bacterial antigen, 

 there is evidence that transfer to room temperature stimulates anti- 

 body syntheses. In general, it has been found that bats which had 

 equivocal titers(l,0tol.7LNI)^atl7to 21 days were usually strongly 

 positive about 2 months post- inoculation. Although viremia develops 

 in all experimentally infected bats, some fail to develop even equi- 

 vocal titers. As was the case in experiments with the bacterial anti- 

 gen, none of the bats aroduced neutralizing antibody in response to 

 Japanese B encephalitis virus during 43 days at 10° C. Similar re- 

 sults were Obtained with some bats which were inoculated with ra- 

 bies virus and bled after 43 days in the cold (Sulkin et al., 1960), 



2 Log neutralization Index (LNI). AnLNIof < UO was considered negative, 1.0 to 1.7 equi- 

 vocal, and 1.7 or above positive. 



383 



