C.J. Leake

Cell lines from larvae of Aedes (Stegomyia) malayensis Colless and Aedes (S) pseudoscutellaris (Theobald) and their infection with some arboviruses.

Abstract The establishment of 2 cell lines from first stage larvae of the mosquitoes, Aedes malayensis and Aedes pseudoscutellaris is described. The cells of the A. malayensis line are diploid while those of A. pseudoscutellaris are predominantly polyploid. West Nile and Japanese B encephalitis viruses produced a cytopathic effect (CPE) in the A. malayensis cells. Both these viruses and Dengue-2 virus also produced a cytopathic effect in the A. pseudoscutellaris cells. There was some evidence that the CPE was influenced by the nature of the container. A. malayensis cells of early subcultures grown in Falcon plastic flasks formed large syncytia while those of later subcultures infected under identical conditions produced only small syncytia. Cells of the A. malayensis line grown on glass did not show any cytopathic response in early subcultures, but in cells of higher subcultures grown on glass, the viruses produced a definite CPE presenting as degenerate clumps of cells and floating single cells. It is suggested that the different result is due to continual adaptation of the cells to the culture conditions in the early stages. Cells of the A. pseudoscutellaris line, following infection with viruses formed syncytia, clearly visible on plastic surfaces, but less obvious on glass. An unadapted strain of Dengue-2 in infected human serum produced syncytia in the cells, but did not produce any plaques in a stable line in pig kidney cells. The infected cultures recovered after some days and formed healthy monolayers. Such cells were subcultured without showing any cytopathic response, but continued to produce virus.

Cytopathic effect and plaque formation by arboviruses in a continuous cell line (XTC-2) from the toad Xenopus laevis.

Forty-six arboviruses were tested for c.p.e. and/or plaque formation in an amphibian cell line. C.p.e. was observed with a high proportion of the viruses tested. Comparative plaque assay, in the XTC-2 cells at 28 degrees C and Vero cells at 37 degrees C, suggests that these systems are comparable in sensitivity and susceptibility to infection. Practical uses of this cell line are discussed.

Changes in enzyme titres with age in four geographical strains of Aedes aegypti and their association with insecticide resistance.

Abstract. The enzymes acetylcholinesterase, glutathione S‐transferase (GST), glucose 6‐phosphate dehydrogenase (G6PD), and general esterases were assayed in four strains of Aedes aegypti mosquitoes aged between 1 and 30 days. Microtitre plate methods were used to assay activity in the homogenates of individual mosquitoes. The levels of GST and G6PD declined with the age of the mosquitoes, while the activity for the other enzymes remained constant. Soluble protein content was also found to decline with mosquito age in all the strains.

Isolations in a Mosquito (Aedes pseudoscutellaris) Cell Line (Mos. 61) of Yellow Fever Virus Strains from Original Field Material

A simple, rapid and inexpensive method of isolating yellow fever (YF) virus from naturally infected mosquitoes, human liver and the serum of a sentinel monkey by inoculation of a continuous line of mosquito cells is described. The mosquito cells were more sensitive than suckling mice and marginally better than Vero cells for primary isolation. This is the first time that mosquito cells have been successfully used for primary isolation of YF virus from field material.

Isolation of japanese encephalitis virus strains from sentinel pigs in northern thailand, 1982

Abstract : Pigs were placed at homes of patients with viral encephalitis in Thailand in 1982 in and effort to isolate the causative virus. The studies showed that transmission of Japanese encephalitis virus to pigs was intense, and suggest that the peak rate of transmission to pigs was two weeks before the peak rate of transmission of humans.

The vector competence of colonized Aedes (Stegomyia) katherinensis for dengue-2 virus

Colonized Aedes (Stegomyia) katherinensis mosquitoes from Australia were infected with the PR-159 strain of dengue-2 virus using a membrane feeding technique and by intrathoracic inoculation. Virus replication to low levels was detected when mosquitoes infected by both routes were assayed using the virus-sensitive Ae. pseudoscutellaris (LSTM-AP-61) mosquito cell line in a microculture system. Analysis by indirect immunofluorescence revealed the expected 100% infection rates in inoculated mosquitoes compared with only 45% in orally infected mosquitoes. Few of the orally infected mosquitoes showed any viral antigen associated with the head and no virus transmission was detected. Preliminary studies also demonstrated that Ae. (S.) katherinesis was refractory to oral infection with Japanese encephalitis virus but was readily infected by intrathoracic inoculation. On the basis of this data, it is concluded that there is a high threshold of infection in this mosquito and that it is unlikely that Ae. (S.) katherinensis could be important as a vector of dengue-2 virus in Australia.