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Parasites and Vectors

, 10:186

First Online: 18 April 2017Received: 10 August 2016Accepted: 24 March 2017DOI: 10.1186-s13071-017-2109-5

Cite this article as: Habtewold, T., Groom, Z. & Christophides, G.K. Parasites Vectors 2017 10: 186. doi:10.1186-s13071-017-2109-5

Abstract

BackgroundThe Anopheles gambiae complex consists of species that vary greatly in their capacity to transmit malaria. The mosquito immune system has been identified as a key factor that can influence whether Plasmodium infection establishes within the mosquito vector. This study was designed to investigate the immune responses of An. coluzzii, An. arabiensis and An. quadriannulatus mosquitoes. The first two mosquito species are major vectors of malaria in sub-Saharan Africa, while the third is thought to be a non-vector.

MethodsAll three mosquito species were reared in mixed cultures. Their capacity to eliminate P. berghei and regulate midgut bacteria was examined.

ResultsOur results revealed large differences in mosquito resistance to P. berghei. In all three mosquito species, immune reactions involving the complement system were triggered when the number of parasites that mosquitoes were challenged with exceeded a certain level, i.e. immune tolerance threshold. This threshold was markedly lower in An. quadriannulatus compared to An. coluzzii and An. arabiensis. We also demonstrated that the level of immune tolerance to P. berghei infection in the haemolymph is inversely correlated with the level of immune tolerance to microbiota observed in the midgut lumen after a blood meal. The malaria non-vector mosquito species, An. quadriannulatus was shown to have a much higher level of tolerance to microbiota in the midgut than An. coluzzii.

ConclusionsWe propose a model whereby an increased tolerance to microbiota in the mosquito midgut results in lower tolerance to Plasmodium infection. In this model, malaria non-vector mosquito species are expected to have increased immune resistance in the haemocoel, possibly due to complement priming by microbiota elicitors. We propose that this strategy is employed by the malaria non-vector mosquito, An. quadriannulatus, while An. coluzzii has reduced tolerance to bacterial infection in the midgut and consequently reduced immune resistance to Plasmodium infection at the haemocoel level. An in-depth understanding of the molecular mechanisms regulating immune tolerance versus resistance in different mosquito vectors of malaria could guide the design of new vector and disease control strategies.

KeywordsMosquito immunity Pathogen tolerance-resistance Plasmodium Microbiota Haemolymph antimicrobial activity AbbreviationsAPL1Anopheles-Plasmodium-responsive leucine-rich repeat 1

CSPCircumsporozoite protein

Duox-IMPerDual oxidase - immunomodulatory peroxidase

GFPGreen fluorescent protein

ImdImmune deficiency pathway

NF-κBNuclear factor-kappaB

PGRPPeptidoglycan recognition protein

qPCRQuantitative real-time polymerase chain reaction

RLIM1Leucine-rich repeat proteins 1

RT-qPCRReverse-transcription qPCR

TEP1Thioester-containing protein 1

Electronic supplementary materialThe online version of this article doi:10.1186-s13071-017-2109-5 contains supplementary material, which is available to authorized users.





Autor: Tibebu Habtewold - Zoe Groom - George K. Christophides

Fuente: https://link.springer.com/



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