Mosquito saliva enhances virus replication and disease

Mosquito saliva, which is injected into the host as a mosquito probes for a blood vessel, contains a collection of chemicals which include anticoagulants to prevent blood clotting, vasodilators to keep blood vessels wide, and anesthetics to prevent us from sensing the mosquito. Saliva also contains components that enhance viral replication, dissemination, and pathogenesis by inducing an inflammatory response that inadvertently promotes infection by providing new cell targets for infection (paper link). To separate the bite from virus inoculation, mice were first exposed to Aedes aegyptii mosquitoes, and then infected at the bite site with two different mosquito transmitted viruses, Semliki Forest virus or Bunyamwera virus. Mosquito bites caused more virus replication at the inoculation site, greater dissemination of virus, and more lethality compared with control mice that received only virus. How does mosquito saliva enhance virus replication and dissemination? Part of the story is that as the mosquito probes for a blood vessel, it causes damage that leads to vascular leakage and accumulation of fluid (edema) which inhibits movement of virus to draining lymph nodes. But delaying dissemination of virus alone does not promote infection and disease. Mosquito bites cause an infiltration of neutrophils (a type of white blood cell) into the bite site. The edema at the bite site is enhanced by neutrophils, because depleting these cells from mice greatly reduced edema. This deple...
Source: virology blog - Category: Virology Authors: Tags: Basic virology Information arbovirus Bunyamwera virus dissemination edema inflammation macrophage mosquito neutrophil saliva Semliki Forest virus viral viremia Source Type: blogs