Project description:West Nile virus (WNV) is a mosquito-borne RNA flavivirus and the cause of more than 31,000 cases in the USA from 1999-2011 including 1, 262 fatalities. WNV infections are typically asymptomatic, but some patients, especially the elderly and immunocompromised, may experience severe neurological disease and even death. Control of WNV infection by the immune system is multifactorial. We profiled antibody, cytokine responses and gene expression from a stratified cohort of WNV subjects to define immune responses that contribute to disease severity and outcome. Differential gene expression by human PBMCs from asymptomatic and severe patients with WNV infection were generated by microarray.
Project description:West Nile virus (WNV) is a mosquito-borne RNA flavivirus which has caused more than 31,000 cases in the USA from 1999-2011 including 1,262 fatalities. WNV infections are typically asymptomatic, but some patients, especially the elderly and immunocompromised, may experience severe neurological disease and even death. Control of WNV infection by the immune system is multifactorial. We profiled antibody and cytokine responses from a stratified cohort of WNV subjects to define immune responses that contribute to disease severity. While antibody levels were not significantly different between asymptomatic and severely ill subjects in our cohort, subjects with severe infections had lower levels of serum IL-4. Further, we detected 158 genes that were differentially expressed by asymptomatic and severely infected cohorts and using cluster analysis correlated WNV susceptibility with IL-4 related gene expression pathways. Our results suggest an important contribution for IL4 in more severe responses to WNV.
Project description:During probing and feeding, an infected mosquito injects both virus and saliva into the host skin. The presence of mosquito saliva in the skin increases arbovirus pathogenesis in the bitten host, however the exact mechanism behind this remains to be determined. It is hypothesized that disease enhancement is dependent on the function of the dermal endothelium, where an increased permeability aids in the influx of virus-susceptible cells to the bite site and therefore more cells for the virus to replicate in. Here, we investigate and compare the effects of saliva from Culex and Aedes species on the human dermal endothelial cell function in vitro. Furthermore, we investigate the effect of Culex saliva on West Nile virus (WNV) pathogenesis in a mouse model. We found that salivary gland extract from anthropophilic mosquito species (Aedes and Cx. pipiens molestus) induce permeability of the human dermal endothelium, while an ornithophilic mosquito species (Cx. pip. pipiens) does not. We identified that this effect is due to the presence of protease(s) in Cx. pipiens molestus saliva. In addition, we show that the presence of Cx. saliva at the WNV inoculation site in vivo leads to more consistent weight loss, increased permeability in the inoculation site, and increased mortality compared to inoculation of WNV alone. Moving forward, identification and characterization of novel salivary proteins from similar but genetically distinct mosquito species will advance the development of intervention methods to combat potential transmission risks and disease severity of emerging mosquito-borne pathogens.