To determine the role of mosquito-derived factors on dengue pathogenesis, we inoculated Ifnar–/–mice i.d. with 105 PFU of the mouse-adapted virulent DENV2 strain D220 [31] (hereafter termed “DENV”) in PBS or mixed with SGE (equivalent to one salivary gland of a female Ae. aegypti mosquito). The gene discussed is IFNAR1; the disease is dengue disease.