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Projekt
Molecular determinants of alphavirus vector competence
Antragstellerinnen / Antragsteller
Privatdozentin Dr. Beate Kümmerer; Professor Dr. Martin Pfeffer
Fachliche Zuordnung
Virologie
Förderung
Förderung von 2013 bis 2016
Projektkennung
Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 226337459
The transmission and spread of mosquito-borne arboviruses is poorly understood, in part because of the difficulty in reliably locating both vectors and hosts for sampling. Mosquito-borne alphaviruses are responsible for a variety of zoonotic illnesses throughout the world. However it is not known what causes epidemics to occur in some areas at particular times and what triggers their emergence. Of particular interest in this context is the vector competence of a mosquito species to a given alphavirus. How effective a vector can transmit a virus depends on environmental factors, mostly the temperature, but the general ability to serve as a vector is thought to be genetically defined. To overcome these restrictions, genetic alterations of an arbovirus will allow adaptation to the mosquito vector, i.e. infection of the midgut cells or faster and more efficient replication within the mosquito. The severe consequences such mutations can cause, was impressively demonstrated by the recent pandemic of Chikungunya virus (CHIKV). A single amino acid exchange in the CHIKV E1 protein resulted in better dissemination rates in Aedes albopictus leading to millions of human cases in Africa and Asia in only a few years. This study is using CHIKV as a model system, aiming to define genetic elements that determine vector competence and allow a virus to cross vector species or even mosquito genera. Three mosquito species differing in their susceptibility for CHIKV from high (Aedes albopictus) to weak (Ae. vexans) to refractory (Culex pipiens) will be used in the laboratory. This setup will allow us to investigate the genetic changes of the virus needed to modulate infectivity for each mosquito vector species. Three independent approaches will be used to force and trace the corresponding alteration(s): (i) passaging the virus in weak-/non-susceptible mosquito cells in vitro, (ii) passaging the virus in weak-/non-susceptible mosquito vector species in vivo via oral feeding using a very high titred virus solution and forced intrathoracic inoculation, thereby circumventing the midgut infection barrier, and (iii) using chimeric viruses. The latter will be established by exchanging fragments within an infectious CHIKV cDNA clone against the corresponding regions of Sindbis virus, another alphavirus known to be transmitted by Cx. pipiens. Finally, marker rescue experiments with adaptive mutations obtained after serial passage in the insect cells and/or mutations obtained after passage in the mosquitoes will be performed in the mosquitoes using the CHIKV cDNA clone. These studies will determine the genetic requirements that allow CHIKV to break the species barrier thereby allowing this arbovirus to change and/or extend its vector host range.
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