Virological and Immunological Determinants of Arbovirus Infection in New Caledonia

Arboviruses, diseases transmitted to humans by the bite of an insect vector, are a major public health problem, particularly in tropical and sub-tropical countries. In New Caledonia, dengue epidemics are recurrent and may be associated with the co-circulation of other arboviruses such as Zika or chikungunya. The virological determinants which condition the occurrence of these epidemics may be linked to an increased vectorial competence of the vector mosquito Aedes aegypti for a particular viral isolate. In fact, the Aedes aegypti mosquito is infected by making a blood meal on a person infected with an arbovirus. The virus infects its digestive tract, then spreads throughout the mosquito's body until it reaches its salivary glands. The virus is then present in the saliva and will be injected into the human host during a new blood meal. Some viral variants are best transmitted by Aedes aegypti. In general, the study of this vectorial competence is carried out by experiments in the laboratory during which an artificial blood meal composed of mammalian blood (human, rabbit, etc.) is mixed with a viral stock. Carrying out deported blood meals during which blood collected from patients infected with an arbovirus is used to gorge mosquitoes makes it possible to place oneself in experimental conditions as close as possible to the natural cycle of transmission of arboviruses. In the human host, cells of the myeloid lineage present in the peripheral blood constitute preferred targets of replication for arboviruses. At the same time, the peripheral blood cells of patients are activated in response to infection and secrete many soluble factors released into the blood of patients. The study of blood samples from patients infected with arboviruses is therefore of prime importance for understanding both the replicative mechanisms of arboviruses but also the immune response they induce.