Identification of immune‐responsive genes in the mosquito Culex quinquefasciatus infected with the filarial parasite Wuchereria bancrofti

Abstract

Several antimicrobial/parasitic peptides are known to be upregulated in mosquitoes upon infection with parasites. The aim of this study was to identify immune-responsive genes in the vector mosquito, Culex quinquefasciatus Say (Diptera: Culicidae) against the human lymphatic filarial parasite, Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae). Suppression subtractive hybridization was performed using RNA from filarial infected and non-infected mosquitoes to obtain differentially expressed transcripts, and their identities were confirmed through reverse transcriptase polymerase chain reaction (RT-PCR). Out of 23 clones selected from the suppression subtractive library, three corresponded to antimicrobial peptide genes, defensins, and four corresponded to regulatory serpin peptide genes. RT-PCR using defensin-specific primers and sequencing of the product showed a 284-bp defensin cDNA. Sequence alignment with defensins of the mosquitoes Anopheles gambiae s.s. Giles and Aedes aegypti (L.) showed maximum homology with the former. Similarly, that of serpin-specific primers showed a 406-bp cDNA encoding serpins. Sequence alignment showed maximum homology with that of An. gambiae, as in the case of defensins. Hence, this investigation revealed upregulation of defensins and serpins in Cx quinquefasciatus infected with W. bancrofti. Antimicrobial peptide genes such as defensins may have limited or no specific role in regulating parasite development. Serpins may prove to be facilitating molecules, by regulating melanization of the parasite. However, the exact functions of these molecules in the immune system of the vector mosquito are yet to be investigated.

Mosquito Infection Responses to Developing Filarial Worms

“…aegypti infected with W. bancrofti [29], but transcriptional responses that occur in these mosquitoes may not represent genes that are used to deter filarial worm infection in an incompatible system, i.e., it is quite possible that differences in gene transcription of mosquitoes in different genera could represent unique strategies for overcoming damage caused by filarial worms and therefore do not represent anti-filarial worm responses. Similarly, identification of immune-responsive genes activated in response to filarial worm infection does not indicate that the mosquito is/has mounted an immune response against the parasites itself [30]. It is possible that the observed response could be an indirect effect caused by the infection, i.e., mf midgut penetration or muscle cell damage that occurs later in development in compatible mosquitoes.…”

Highly specific host-pathogen interactions influence Metarhizium brunneum blastospore virulence against Culex quinquefasciatus larvae

“…Transferrin is a defence molecule which has been shown to be up-regulated in Cx. quinquefasciatus during activation of the immune response [51]. Transferrin is an iron-binding protein involved in iron transport, however in insects it also inhibits the growth of bacteria and other invading organisms by sequestering iron [52,53].…”

Seasonal Variation of Midgut Bacterial Diversity in Culex quinquefasciatus Populations in Haikou City, Hainan Province, China

“…quinquefasciatus , one of the most significant mosquito vectors in the world, is widespread in most parts of southern China with a wide range of distribution. A variety of diseases could be spread, including bancroftian filariasis, West Nile encephalitis, St. Louis encephalitis [ 26 , 27 , 28 ], etc. There is no doubt that these studies were exceedingly necessary for mosquito-borne diseases, but there was a lack of depth exploration of the processes affecting mosquito-pathogen interactions.…”