Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) is an emerging tool for routine identification of bacteria, archaea and fungi. It has also been recently applied as an accurate approach for arthropod identification. Preliminary studies have shown that the MALDI-TOF MS was able to differentiate whether ticks and mosquitoes were infected or not with some bacteria and Plasmodium parasites, respectively. The aim of the present study was to test the efficiency of MALDI-TOF MS tool in distinguishing protein profiles between uninfected mosquitoes from specimens infected by filarioid helminths. Aedes aegypti mosquitoes were engorged on microfilaremic blood infected with Dirofilaria immitis, Brugia malayi or Brugia pahangi. Fifteen days post-infective blood feeding, a total of 534 mosquitoes were killed by freezing. To assess mass spectra (MS) profile changes following filariae infections, one compartment (legs, thorax, head or thorax and head) per mosquito was submitted for MALDI-TOF MS analysis; the remaining body parts were used to establish filariae infectious status by real-time qPCR. A database of reference MS, based on the mass profiles of at least two individual mosquitoes per compartment, was created. Subsequently, the remaining compartment spectra (N = 350) from Ae. aegypti infected or not infected by filariae were blind tested against the spectral database. In total, 37 discriminating peak masses ranging from 2062 to 14869 daltons were identified, of which 17, 11, 12 and 7 peak masses were for legs, thorax, thorax-head and head respectively. Two peak masses (4073 and 8847 Da) were specific to spectra from Ae. aegypti infected with filariae, regardless of nematode species or mosquito compartment. The thorax-head part provided better classification with a specificity of 94.1% and sensitivity of 86.6, 71.4 and 68.7% of D. immitis, B. malayi and B. pahangi respectively. This study presents the potential of MALDI-TOF MS as a reliable tool for differentiating non-infected and filariae-infected Ae. aegypti mosquitoes. Considering that the results might vary in other mosquito species, further studies are needed to consolidate the obtained preliminary results before applying this tool in entomological surveillance as a fast mass screening method of filariosis vectors in endemic areas.
Filariosis is a disease group affecting humans and animals, caused by nematode parasites of the family Onchocercidae, superfamily Filarioidea. These parasites can be transmitted, essentially, by mosquitoes during blood meals of infected female specimens. Screening vectors for these filariae currently relies on time- and resource-consuming methods such as dissection and polymerase chain reaction-based methods. Here, we applied matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) to assess whether this tool can detect changes in the protein profiles of Aedes aegypti infected with filarioid helminths compared to those uninfected by testing different parts of mosquitoes. First a reference mass spectra database from Ae. aegypti infected or not infected by filariae was created using MS from 47 specimen compartments. Then we tested the remaining mass spectra (350 x 4) in a blind validation test. Regardless of filariae species, the best correct classification rate was obtained from the thorax-head part with a specificity of 94.1% and sensitivity of 86.6, 71.4 and 68.7% for non-infected and D. immitis, B. malayi and B. pahangi infected mosquitoes respectively. The results indicated that MALDI-TOF MS is potentially able to screen Aedes aegypti mosquitoes as being non-infected or filariae-infected. Furthermore, complementary works using other mosquito species infected with different filarioids are needed to reinforce these preliminary results prior to apply this tool on field samples.