title: Quantitative PCR analysis of the salivary gland hypertrophy virus (GpSGHV) in a laboratory colony of Glossina pallidipes.
abstract: Many species of tsetse flies can be infected by a virus that causes salivary gland hypertrophy (SGH) and virus isolated from Glossina pallidipes (GpSGHV) has recently been sequenced. Flies having SGH have a reduced fecundity and fertility. To better understand the impact of this virus in a laboratory colony of G. pallidipes, where the majority of flies are infected but asymptomatic, and to follow the development of SGH in symptomatic flies in relation to virus copy number, a quantitative PCR (qPCR) method was developed. The qPCR analyses revealed that in asymptomatic flies virus copy number averaged 1.68E+5, 2.05E+5 and 1.07E+7log(10) in DNA from an excised leg, salivary glands and a whole fly, respectively. In symptomatic flies the virus copy number in the same organs averaged 1.34E+7, 1.42E+10 and 1.5E+9, respectively. Despite these statistically significant differences (p<<0.0001) in virus copy number between asymptomatic and symptomatic flies, there was no correlation between age and virus copy number for either sets in adult flies. A clear correlation between virus copy number in pupae and their mothers was observed. Reverse transcription quantitative PCR (RT-qPCR) of the viral messenger RNA encoding ODV-E66, an envelope protein, revealed a clear correlation between virus copy number and the level of gene expression with values of 2.77log(10) in asymptomatic males and 6.10log(10) in symptomatic males. Taken together these results confirm the close relationship between virus copy number and SGH syndrome. They demonstrate the vertical transmission of GpSGHV from mother to progeny, and suggest that the development of SGH may be correlated to the virus copy number acquired by the larva during its intra-uterine development.
authors.affiliation: Entomology Unit, FAO/IAEA Agriculture & Biotechnology Laboratory, IAEA Laboratories Seibersdorf, A-2444 Seibersdorf, Austria. a.m.m.abd-alla@iaea.org
authors.forename: Adly M M
authors.initials: AM
authors.lastname: Abd-Alla
authors.forename: François
authors.initials: F
authors.lastname: Cousserans
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Parker
authors.forename: Chiraz
authors.initials: C
authors.lastname: Jridi
authors.forename: Max
authors.initials: M
authors.lastname: Bergoin
authors.forename: Alan S
authors.initials: AS
authors.lastname: Robinson
mesh_terms: D000375:Aging; D000818:Animals; D003587:Cytomegalovirus / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics*; D005260:Female; D008297:Male; D016133:Polymerase Chain Reaction; D012469:Salivary Glands / Q000821:virology; D017678:Sex Distribution; D013696:Temperature; D014370:Tsetse Flies / Q000821:virology*
chemical_list: D017931:DNA Primers; D004279:DNA, Viral