Aedes aegypti salivary protein "aegyptin" co-inoculation modulates dengue virus infection in the vertebrate host

Abstract

Dengue virus (DENV) is transmitted in the saliva of the mosquito vector Aedes aegypti during blood meal acquisition. This saliva is composed of numerous proteins with the capacity to disrupt hemostasis or modulate the vertebrate immune response. One such protein, termed "aegyptin," is an allergen and inhibitor of clot formation, and has been found in decreased abundance in the saliva of DENV-infected mosquitoes. To examine the influence of aegyptin on DENV infection of the vertebrate, we inoculated IRF-3/7(-/- -/-) mice with DENV serotype 2 strain 1232 with and without co-inoculation of aegyptin. Mice that received aegyptin exhibited decreased DENV titers in inoculation sites and in circulation, as well as increased concentrations of GM-CSF, IFN-γ, IL-5, and IL-6, at 48 h post-inoculation when compared to mice that received inoculation of DENV alone. These and other data suggest that aegyptin impacts DENV perpetuation via elevated induction of the immune response.

Keywords: Aegyptin; Allergen; Dengue; Mosquito; Mouse; Saliva; Virus.

Figure 1

DENV titers in inoculated ears and draining submandibular lymph nodes at 48 hours post inoculation. DENV titers, expressed as PFU-equivalents/mL (PFU*/mL) were significantly lower in the ears of mice that received co-inoculation of DENV + aegyptin (AV) as compared to the cohort that received DENV only (V, p=0.0057), as indicated by an asterisk. DENV titers were not found to be significantly different in the lymph nodes (p=0.0678), although they followed a similar trend as those of the ears. Associated bars represent standard error of the means.

Figure 2

Cytokine concentrations in the inoculated ears (A) and draining submandibular lymph nodes (B) at 48 hours post inoculation. The y-axis displays concentration in pg/mL and the x-axis denotes treatment groups (AV = DENV + aegyptin, V = DENV only, A = aegyptin only, M = mock inoculation). Significant comparisons are indicated by an asterisk (p≤0.05). Associated bars represent standard error of the means.

Figure 3

Comparison of circulating leukocyte percents (counts) at 48 hours post inoculation for the DENV + aegyptin inoculated cohort (AV) compared to the virus only cohort (V). Comparisons of each leukocyte were performed using odds ratios and significance is indicated by an asterisk (p≤0.05). Ninety-five percent confidence intervals are displayed.

Figure 4

DENV viremia titers in serum samples on the first six days post inoculation. DENV titers, expressed as PFU-equivalents/mL (PFU*/mL) were significantly lower in mice inoculated with DENV + aegyptin as compared to those inoculated with virus alone on day 2 post inoculation. DENV titers were significantly higher in mice inoculated with DENV + aegyptin as compared to those inoculated with virus alone on day 5 post inoculation. Significance is indicated by an asterisk (p≤0.05). Associated bars represent standard error of the means.