Full‐length cDNA clones encoding D7 (AnsD7) and D7‐related (AnsD7r1) secreted salivary gland proteins were isolated from Anopheles stephensi. Corresponding proteins were separated by SDS‐PAGE and analysed by N‐terminal sequencing, which also identified a second D7‐related protein (AnsD7r2). AnsD7 encodes a protein of 37 kDa, AnsD7r1 of 18 kDa, and AnsD7r2 of 16 kDa. Polyclonal antibodies against recombinant AnsD7 showed immunological cross‐reactivity with the D7‐related proteins, and alignment demonstrated sequence similarity between the C‐terminal region of AnsD7 and the D7‐related proteins. AnsD7, AnsD7r1 and AnsD7r2 were major female‐specific salivary gland proteins, and Western blotting, immunohistochemistry and immunogold labelling demonstrated expression was predominantly in the secretory cavities of the distal‐lateral and median lobes. Expression and localization of D7 and D7‐related proteins was similar in Plasmodium berghei‐infected and uninfected mosquitoes.
To a large extent, control of malaria vectors relies on the elimination of breeding sites and the application of chemical agents. There are increasing problems associated with the use of synthetic insecticides for vector control, including the evolution of resistance, the high cost of developing and registering new insecticides and an awareness of pollution from insecticide residues. These factors have stimulated interest in the application of molecular biology to the study of mosquito vectors of malaria; focussing primarily on two aspects. First, the improvement of existing control measures through the development of simplified DNA probe systems suitable for identification of vectors of malaria. The development of synthetic, non-radioactive DNA probes suitable for identification of species in the Anopheles gambiae complex is described with the aim of defining a simplified methodology wich is suitable for entomologist in the field. The second aspect to be considered is the development of completely novel strategies through the development of completely novel strategies through the genetic manipulation of insect vectors of malaria in order to alter their ability to transmit the disease. The major requirements for producing transgenic mosquitoes are outlined together with the progress wich has been made to date and discussed in relation to the prospects which this type of approach has for the future control of malaria.
DOI : 10.1590/S0074-02761992000700005 Anahtar Kelimeler :
molecular biology, DNA probes, vectors, malaria control
Cilt: 87 Sayfa: 43 - 49
Tests were carried out in Kenya to determine whether the enzyme-linked synthetic oligonucleotide probe (pAna 1) developed for identifying species of the Anopheles gambiae complex could be used under field conditions. The An. arabiensis male-specific pAna 1 probe was able to identify all male larval instars and adult males. however, the non-radioactive assay was not sufficiently sensitive to identify male sperm dna in all the mated female an. arabiensis. Although the ratio of An. arabiensis to An. gambiae s.s. identified with pAna 1 in males during the dry season was in agreement with the ratio in half-gravid females identified cytogenetically, the ratios were different during the wet season. This study demonstrates that the enzyme-linked DNA probe assay is applicable under field conditions.
A variety of very effective methods have been employed for suppressing insect vector populations, including the application of biological control agents and the elimination of breeding sites, with a continuing and heavy reliance on the use of chemical insecticides. However, the development of insecticide resistance by vector insects, the cost of developing and registering new insecticidal compounds, and the increase in legislation to combat the detrimental effects of insecticidal residues on the environment, have emphasized the need to assess alternative strategies for vector control. What is required is a completely novel approach to either suppress vector populations, or to alter their ability to transmit disease-causing organisms in such a way as to have a profound and long-lasting effect on disease transmission. Genetic manipulation of insect vectors may provide just such an approach. The major requirements for genome manipulation in insects and the progress which has been made to create transgenic vector insects are reviewed. The potential applications of this methodology are then explored in the context of its future use for the control of vector-borne diseases.