BUNYAVIRUS PERSISTENCE IN AEDES ALBOPICTUS CELL CULTURES.

Abstract

Some viruses which infect plants, animals and man are transmitted by an intermediary arthropod vector. The viruses for which this is true are termed arboviruses (Arthropod-borne-viruses). In many instances the virus delivered to the new host results in the establishment of a disease state and/or the death of the infected host. In all instances, however, the arthropod (invertebrate) vector is apparently unaffected by the virus it is carrying. One family of viruses which are transmitted to their vertebrate host via an arthropod vector is the virus family Bunyaviridae, in this dissertation specifically the viruses Inkoo and Uukuneimi are described. The characteristics of Inkoo and Uukuneimi growth in both vertebrate baby hamster kidney (BHK-21, WI2) and invertebrate Aedes albopictus (mosquito) cell cultures has been examined. Vertebrate cells supported, to a high titer, the growth of both Inkoo and Uukuneimi virus while Aedes albopictus cell cultures supported high titer growth of Inkoo but not Uukuneimi. In both cases, however, the vertebrate cells were killed as a cosequence of infection where as, the invertebrate infection did not result in cell death or in detectable cytopathic effect. The invertebrate cells infected with either Inkoo or Uukuneimi continue to grow and also continue to express virus specific (actinomycin D resistent) RNA synthesis. The virus infected invertebrate cells are characterized as being persistently infected because of their resistence to homologous virus superinfection and by detectable virus specific RNA synthesis. Virus released from the Inkoo persistently infected cells displays a heterogeneous plaque morphology as well as temperature sensitive virus plaque mutants. Virus particles released from the Inkoo persistently infected Aedes albopictus cells are considered defective interfering-like. The RNA profile both intracellularly and of released virus particles from the persistently infected cell cultures is different from that observed during vertebrate cell culture infections. Cell death resulted from infection of BHK-21 WI2 cells with virus from Inkoo persistently infected Aedes albopictus cell cultures. The virus plaque morphology and RNA profile is similar to standard virus infection of BHK-21 WI2 cells. The experiments with tissue culture virus-cell systems aids in understanding the natural transmission of arboviruses between the vertebrate-invertebrate portions of the arbovirus natural life-cycle.