Biochemistry and Molecular Biology of Insects

  HEADDr ROTH, Charles /
HOLM Inge / Dr PAUL Richard / Dr ROSINSKI-CHUPIN Isabelle

  Annual Report


Anopheles gambiae, the vector of human malaria.

A female Anopheles gambiae mosquito, the most important vector of malaria in sub-Saharan Africa, probes probes the human skin in search of a blood meal that will allow her to produce eggs. The proboscis releases saliva to lubricate its piercing of the dermis. If the mosquito is infected with malaria parasites, the sporozoite form matures in the salivary gland and can migrate into the human skin via the excreted saliva, The parasites then migrate to the human liver where they develop into the form that infects red blood cells and cause malaria. Preventing mosquito biting blocks the only natural route of malaria parasite transmission.


The laboratory has studied gene transcription in normal and in infected salivary glands to measure changes related to plasmodium infection using the SAGE technique. Using this procedure, fifty-seven Anopheles differentially expressed genes were detected and four are being studied in detail. Likewise, sixty-six new Plasmodium sporozoite transcripts were identified and several of these genes are being studied to determine their role in salivary gland invasion and mammalian infection.


The transcriptional analysis is being complemented by proteomic analysis of the salivary gland and of saliva. 131 salivary gland proteins were identified - 89 for the first time. The value of these studies is exemplified by our observations that when apyrase RNA was reduced by 85%, nucleotidase activity was only reduced by 35%. However, “apyrase RNAi-injected” mosquito salivary gland extracts were significantly less efficient than those of controls for inhibiting ADP induced platelet aggregation. Additionally, the decreased apyrase level in saliva correlated with significantly lengthened mosquito probing time.


Continuing our involvement with the Anopheles genome project, we have continued our collaboration with Genoscope, the French National Sequencing Center. About 100,000 “full-length enriched” cDNAs from compete mosquitoes, embryos and larval stages have been synthesized, sequenced and annotated. We have also participated in the international Aedes aegypti genome sequencing and annotation project. This cDNA project was in collaboration with a team at the University of Sao Paulo, Brazil.


In people living in areas of seasonal malaria transmission, the sexual forms of the P. falciparum parasite are found at low levels during the dry season when mosquitoes are rare. At the beginning of the wet season, when A. gambiae returns to the area and can transmit the parasite, the number of sexual forms in infected individuals increases dramatically. We have been working in Senegal to test the hypothesis that the mosquito saliva from early mosquito bites stimulates the malaria parasites to produce more sexual forms and, thus, to increase the probability of malaria transmission.

Keywords: insect vectors, malaria, paludism, salivary gland, transcriptome, SAGE, proteome, parasite transmission


Anopheles gambiae, the vector of human malaria.

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Publications 2006 of the unit on Pasteur's references database

Activity Reports 2006 - Institut Pasteur
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