Age Grading Tools for Anopheles Mosquitoes with a Field Validation

Abstract

Estimating the age distribution of mosquito populations is not only crucial for assessing their capacity to transmit malaria but it can also be used to determine the efficacy of vector control programs against mosquito vectors. Vector age grading tools that can rapidly and cost-effectively determine the age of large numbers of mosquito populations are required. The first objective of this study was to evaluate protein expression changes occurring in the heads and thoraces of laboratory reared Anopheles gambiae s.s. Giles from Ifakara and Anopheles stephensi Liston New Delhi strain relative to their age. Protein expression was assessed using 2D-Difference Gel Electrophoresis (2D-DIGE) and the identity of differentially expressed proteins was determined using Matrix-Assisted Laser Desorption Ionization (MALDI) / tandem time-of-flight (TOF/TOF) mass spectrometry and by matching peptides to published An. gambiae protein database. In two separately reared cohorts of An. stephensi, a total of 702 and 691 spots were detected from cohort one and cohort two respectively. Of these, 3.8% (N=27) and 13% (N = 90) were found to be differentially expressed in cohorts one and two, respectively. Nineteen protein spots were shared between the two cohorts. For An. gambiae, 754 and 585 protein spots were present on 2D fusion images from cohort one and cohort two, respectively. 3.6% (N = 27) of cohort one spots and 5% (N = 30) of cohort two spots were found to change significantly in expression with age. However, only nine spots were shared between the two cohorts. Six An. gambiae and nine An. stephensi protein spots that were shared between cohorts were significantly matched to published An. gambiae sequences within a compiled UniProtKB database. The proteins identified included; AGAP012056; referred to as Actin Depolymerising Factor (ADF) from An. stephensi and probable Methylmalonate-semialdehyde dehydrogenase mitochondrial acylating protein (MMSA) from An. gambiae.