Replication of insect iridescent virus 6 in a whitefly cell line.

The whitefly, Bemisia tabaci, B biotype (syn. B. arentifolii Bellows and Perring) (Homoptera:Aleyrodiae), is a major problem in agroecosystems throughout ropical and subtropical regions of the world. Large opulations of whiteflies reduce crop yields, cause conamination of plant parts with excreted honeydew, and ct as vectors of Begomoviruses and other plant viuses that cause serious economic losses in vegetable nd fiber crops (Brown et al., 1995). According to the Ecological Database of the World’s Insect Pathogens (http://insectweb.inhs.uiuc.edu/ Pathogens/EDWIP/), a pathogenic virus of whiteflies has not been reported to date. Although virus-like particles have been observed in B. tabaci male germ and cyst cells (Báo et al., 1996) and in mycetomes and ovarian tissue (Costa et al., 1996), whether the partiles are of viral origin is not known. One candidate iral pathogen of whiteflies is the Insect iridescent vius 6 (IIV-6), also known as the Chilo iridescent virus. This virus was originally isolated from the rice stem borer (Chilo suppressalis) (Lepidoptera) (Fukaya and Nasu, 1966), but it was previously demonstrated that the virus can replicate in leafhoppers, leafhopper cells, and planthopper tissue explants (Jensen et al., 1972; itsuhashi, 1967). The ability to replicate in leafhoper cells raised the possibility that a whitefly cell line ould also support IIV-6 replication. This report decribes the productive infection of a whitefly cell line ith IIV-6 using light and electron microscopy, fluoresent antibody staining, and Western blot analysis. A recently established whitefly embryo cell line, desgnated BtB-2.97-Hunter & Polston (manuscript in reparation), was cultured in modified Liu and Black nsect medium (Kimura, 1984). The BtB-2.97 cells ere incubated at room temperature (20–22°C) and assed at a 1:3 ratio once per week. An IIV-6 isolate obtained from J. Kalmakoff) was amplified in thirdnstar Tricoplusia ni larvae and purified using differential centrifugation (Marina et al., 1999). The identity of the amplified virus isolate was confirmed by sequencing a portion of the major capsid protein gene (not shown). The virus solution was passed through a sterile 0.45-mm filter before infection of cells. Initial attempts at infecting whitefly cells were made by adding a filtered IIV-6 suspension (0.2 mg protein > 3 10 PFU) to 1.8 3 10 BtB-2.97 cells and by passing nfected cell media (1:67 dilution) to additional whitefly