First attempt to validate human IgG antibody response to Nterm-34kDa salivary peptide as biomarker for evaluating exposure to Aedes aegypti bites

Abstract

Background: Much effort is being devoted for developing new indicators to evaluate the human exposure to Aedes mosquito bites and the risk of arbovirus transmission. Human antibody (Ab) responses to mosquito salivary components could represent a promising tool for evaluating the human-vector contact.

Methodology/principal findings: To develop a specific biomarker of human exposure to Aedes aegypti bites, we measured IgG Ab response to Ae. aegypti Nterm-34 kDa salivary peptide in exposed children in 7 villages of Southern Benin (West Africa). Results showed that specific IgG response presented high inter-individual heterogeneity between villages. IgG response was associated with rainfall and IgG level increased from dry (low exposure) to rainy (high exposure) seasons. These findings indicate that IgG Ab to Nterm-34 kDa salivary peptide may represent a reliable biomarker to detect variation in human exposure to Ae. aegypti bites.

Conclusion/significance: This preliminary study highlights the potential use of Ab response to this salivary peptide for evaluating human exposure to Ae. aegypti. This biomarker could represent a new promising tool for assessing the risk of arbovirus transmission and for evaluating the efficacy of vector control interventions.

Figure 1. Amino-acid sequence of Nterm-34 kDa Peptide.

Amino-acid sequence of the putative 34 kDa family secreted salivary protein of Aedes aegypti (gi: 94468336, NCBI database) is presented and sequence of the Nterm-34 kDa peptide is underlined. Signal peptide (SP) sequence is indicating by dotted underline.

Figure 2. Evolution of IgG antibody response to Nterm-34 kDa peptide and rainfall during the studied period.

The evolution of specific IgG level in children and the accumulated rainfall in the studied area are presented for each studied period in 2008 and 2009. Black points indicate individual IgG response (ΔDO) of each child of the studied population. Bars indicate median value in each studied period and dotted line represent the threshold (TR) of specific Ab response (ΔDO>0.151). Statistical significant difference between medians is indicated (non-parametric Kruskal-Wallis test). Rainfalls are presented for each month from February 2008 to October 2009 and were acquired using the GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure (Giovanni) as part of the NASA's Goddard Earth Sciences (GES). Data and Information Services Center (DISC). http://disc2.nascom.nasa.gov/Giovanni/tovas/TRMM).

Figure 3. Evolution of individual IgG response to Nterm-34 kDa peptide between dry and rainy seasons.

The results are presented for the peak of the dry (February) and the rainy (July) seasons in 2008 (A) and 2009 (B). Black points indicate individual IgG response (ΔDO) and bars indicate the median value for each group. Dotted line represent the threshold (TR) of specific Ab response (ΔDO>0.151) and statistical significant differences between medians are indicated (non- parametric Wilcoxon test).

Figure 4. Season-related evolution of IgG response to Nterm-34 kDa peptide according to villages.

The evolution of median value of IgG level from the peak of the dry season (February) to the peak of rainy season (July) was presented in 2008 (A) and 2009 (B) according to the 7 studied villages. Numbers from 1 to 7 indicate the villages (1 = Aidjédo; 2 = Dokamé; 3 = Kindjitokpa; 4 = Guézohoué; 5 = Hékandji; 6 = Satré; 7 = Wanho).