|Da Graca, J.|
Submitted to: Journal of Virological Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2006
Publication Date: 2/21/2006
Citation: Herron, C.M., Mirkov, T.E., Da Graca, J.V., Lee, R.F. 2006. Citrus tristeza virus transmission by the toxoptera citricida vector: in vitro acquisition and transmission and infectivity immunoneutralization experiments. Journal of Virological Methods. Interpretive Summary: Citrus tristeza virus (CTV) is the most economically important citrus virus, and Toxoptera citricida, known as the brown citrus aphid (BrCA), is the most efficient vector. Little is known about the interaction between the virus and vector. This study reports the experimental transmission of CTV acquired through an artifical membrane by BrCA from crude extracts but partially purified extracts could not be transmitted. Using the membrane acquisition system, aphids were forced to feed on various CTV-specific antibodies after being fed on CTV infected source trees; antibodies against the coat protein and minor coat protein had no effect on the transmission rate, but in one test antibodies against the p20 CTV gene enhanced the transmission rate. This is the first report of aphid transmission of CTV acquired by feeding on artifical membranes, and the data suggests that inactivity of CTV p20 aids aphid transmission of virions.
Technical Abstract: Citrus tristeza virus (CTV) is transmitted by several aphid species in a semi-persistent manner with Toxoptera citricida, the brown citrus aphid (BrCA), being the most efficient. As yet, the molecular interactions between the virus and its aphid vectors have not been determined. This is the first report of aphids acquiring CTV from preparations through an artificial membrane and then transmitting CTV to receptor plants. The BrCA fed across artificial membranes on crude tissue preparations made from CTV-infected bark tissue were able to transmit CTV to virus-free receptor plants at low rates. CTV p20, p27 and p25 proteins, detected by western blots, were present in all crude preparations from CTV-infected plants. Partially purified CTV preparations were not transmitted by the BrCA in this manner. Infectivity immunoneutralization experiments were conducted where aphids were forced to feed in vitro on three CTV-specific antibodies (p25, p27 and p20) before being placed on receptor plants following a 48 hr acquisition feed on CTV-infected source plants. There were no differences in transmission rates among the majority of treatments and the control treatments. However in one infectivity immunoneutralization experiment, the CTV p20 antibodies significantly enhanced CTV transmission compared to buffer only, pre-immune antiserum or no antibody control treatments. This suggests the inactivity of CTV p20 aids BrCA transmission of virions.