The insect vector always bites twice

In Senegal the rate of antisalivary antibodies against Anopheles in young children (under 5 years), the population most exposed to the risk of malaria, appeared to be proportional to the actual degree of exposure, which had been assessed beforehand by standard entomological capture techniques. All the children involved in the study showed a higher level during the period of most intense transmission, in September. The antibody rate proved also to be associated with the risk of occurrence of a malarial attack in the following three months. These antisalivary antibodies consequently seem to be indicators of the risk of malaria in endemic areas, that could be used to improve strategies of prevention and care of young patients in the context of seasonal transmission of the disease.

The objective of the work conducted on human African trypanosomiasis was to analyse the antibody response to identify exactly, in total saliva extract of Glossinia flies, the immunogenic proteins responsible for synthesis of these specific antibodies (2). The different saliva proteins of four Glossinia species, uninfected, vectors or non-vectors, were separated then put into contact with the serum of individual subjects, infected or uninfected, exposed to bites. Comparison of salivary protein immunogenic profiles obtained showed that they differ depending on the infection status of the subjects (exposed uninfected/infected) and the vector or non-vector status of the Glossinia. Hence, immunogenic proteins specific for two Glossinia species investigated (a 42 kDa protein in G. fuscipes fuscipes, and 50, 55, 65 and 72 kDa proteins in G. morsitans morsitans) could be used to assess specifically the degree of exposure to bites of each of these species.

Starting from immunogenic salivary proteins, simple and effective prevention tools (immuno-tests) can be devised to assess the exposure of human subjects, or be used in endemic areas to evaluate the efficacy of existing vector control strategies, such as the use of impregnated mosquito nets. Analysis of the host-vector relationship, up to now dealt with mainly from the angle of allergic responses to bites or in the search for veterinary vaccines, constitutes now an important research path for new surveillance and prevention strategies.

Marie Guillaume-Signoret – IRD
Translation : Nicholas Flay