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Trans R Soc Trop Med Hyg. 2008 May;102(5):400-8. doi: 10.1016/j.trstmh.2008.01.024. Epub 2008 Mar 14.

The enhancement of arbovirus transmission and disease by mosquito saliva is associated with modulation of the host immune response.

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Institut Pasteur, Département de Parasitologie, Unités de Réponses Précoces aux Parasites et Immunopathologie, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France.


Arthropod-borne (arbo-) viruses have emerged as a major human health concern. Viruses transmitted by mosquitoes are the cause of the most serious and widespread arbovirus diseases worldwide and are ubiquitous in both feral and urban settings. Arboviruses, including dengue and West Nile virus, are injected into vertebrates within mosquito saliva during mosquito feeding. Mosquito saliva contains anti-haemostatic, anti-inflammatory and immunomodulatory molecules that facilitate the acquisition of a blood meal. Collectively, studies investigating the effects of mosquito saliva on the vertebrate immune response suggest that at high concentrations salivary proteins are immmunosuppressive, whereas lower concentrations modulate the immune response; specifically, T(H)1 and antiviral cytokines are downregulated, while T(H)2 cytokines are unaffected or amplified. As a consequence, mosquito saliva can impair the antiviral immune response, thus affecting viral infectiousness and host survival. Mounting evidence suggests that this is a mechanism whereby arbovirus pathogenicity is enhanced. In a range of disease models, including various hosts, mosquito species and arthropod-borne viruses, mosquito saliva and/or feeding is associated with a potentiation of virus infection. Compared with arbovirus infection initiated in the absence of the mosquito or its saliva, infection via mosquito saliva leads to an increase in virus transmission, host susceptibility, viraemia, disease progression and mortality.

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