GROWTH OF VENEZUELAN EQUINE ENCEPHALITIS VIRUS IN TISSUE CULTURES OF MINCED AEDES AEGYPTI LARVAE

Abstract

Abstract : A method for the germfree cultivation of the mosquitoes Aedes aegypti and Aedes triseriatus was developed, and primary tissue cultures were prepared from minced larvae of both insect species. The Trinidad and the 9t strains of Venezuelan equine encephalitis (VEE) virus and the Louisiana strain of eastern equine encephalitis (EEE) virus were grown in larval tissue cultures of A. aegypti. The Trinidad strain of VEE virus was also grown in A. triseriatus larval tissue cultures. The growth of VEE virus in A. aegypti larval tissue culture was influenced by the length of time, the temperature, and the virus concentration used for the adsorption process, and the temperature, pH, and agitation of cultures during the growth process. In these cultures, the Trinidad strain grew somewhat better than the 9t strain; its latent period was shorter by about 8 hours, its growth rate was faster, and it reached higher maximal virus titers. However, EEE virus was superior to the Trinidad strain in each of these growth characteristics. The Trinidad strain, the 9t strain, and the Louisiana strain attained maximal titers of 7.4, 6.1, and 7.6 log pfu/ml, respectively. The presence of a viral inactivating material was detected in larval tissue cultures of both species of mosquitoes. Ten serial passages of the Trinidad strain or five serial passages of the 9t strain in A. aegypti larval tissue cultures caused no detectable changes in either the mouse virulence or plaque size distribution of both virus strains.