Duration of activity of western equine encephalitis neutralizing antibodies in Aedes nigromaculis and Culex tarsalis.

Abstract

SummaryAedes nigromaculis and Culex tarsalis mosquitoes were fed on sera or whole blood of man or animals immune to Western equine encephalitis in order to determine the length of time that ingested neutralizing antibodies remain active in mosquitoes and might interfere with tests for living virus. Neutralizing antibody titers were determined on four different pools of mosquitoes prepared at various intervals up to 65 hours after feeding. Two intervals of incubation at 4°C. were used before mouse inoculation; one hour following the usual laboratory procedure (short test), and 24 hours to provide a more sensitive test for diluted antibodies (long test).Protection by neutralization was demonstrated in two of the four short tests and in all the long tests of mosquito suspensions made within 24 hours of feeding. Lack of time for virus-antibody combination was shown in two pools prepared immediately after feeding. Except for one instance of demonstrable neutralization 24 hours after feeding, no protection was shown in mosquito samples taken 24 hours or more after ingestion of immune bodies.Neutralization of virus in pools of field-collected mosquitoes would undoubtedly take place to a lesser extent than in these experiments since not all would have fed on immune hosts, and such immune blood as was ingested would have a lower titer of neutralizing antibodies. Hence, it is probable that ingested antibodies would not interfere with the isolation of virus from infected mosquitoes if they are held alive at room temperature for approximately 24 hours before freezing.