Acronym: DenVect Vector competence of Aedes aegypti for Dengue viruses in New Caledonia
Principal investigator: O. O’Connor
IPNC main investigator: O. O’Connor, M. Dupont-Rouzeyrol
IPNC collaborators: C. Inizan, N. Pocquet
 Budget 8380 € Budget devoted to IPNC:
Financial supports IPNC
Timeline Start date: Aug.2016 End date: July 2017
Occurence of dengue outbreaks needs three key actors: the pathogen (i.e. the virus), the vector (Aedes sp.) and the human host. In New Caledonia, Ae. aegypti is the major (the only proven to date) vector of arboviruses. Since World War II, NC was regularly affected by dengue outbreaks with a cycling circulation of the four DENV serotypes. However, by the beginning of the year 2000, this pattern has changed with the persistence of DENV-1. These observations suggest that our local vector is competent for DENV. However, its capability to be infected by DENV, allowing the replication and transmission of the virus to human host, has not been studied yet.
We propose to investigate the ability of New Caledonian Ae. aegypti population to transmit different DENV serotypes, in link with the epidemiological profile observed.

Selection of DENV strains from viro-bank and virus stock production: one representative DENV strain of each serotype/genotype will be selected in IPNC viro-bank depending on the year of epidemic circulation. The selected strains will be amplified on C6/36 cells with no more than three passages. Quantification of viruses obtained will be performed by immunofluorescent focus assay on C6/36 cells.

Phenotypic characterization of representative strains in the vector: An Ae. aegypti F1 generation will be used for vector competence studies carrying out on each representative DENV strains. Two independent experiments will be performed, each with the four DENV serotype strains. Infection, dissemination and transmission rates will be measured at day 7 and 14 post-exposure. Samples analysis will be performed as previously described.

DENV-1 to -4 strains, phylogenetically characterized, were obtained on C6/36 cells. The two independent vector competence experiments were conducted with all DENV strains. Preliminary results obtained from the first experiment show that New Caledonian Ae. aegypti are capable to transmit DENV.  Transmission of DENV-1 (genotype I “Asian”) and DENV-4 is observed as early as 7 days post-exposure with rates of 20% and 33% respectively. At 14 days post-exposure, the transmission efficiency is varying from 12.5% to 22% for all the DENV strains. Analysis of the second experiment is in progress.
In New Caledonia, the context is particularly favourable to study the dynamic of DENV transmission, as Ae.  aegypti is the only proven arboviruses vector and the epidemiology of dengue is well-kown. Thus, this project will allow us to have a global vision of the Ae. aegypti competence at a given time, which is an important point to better understand the transmission and dynamics of DENV in New Caledonia.