The ecology unit at Polo GGB: rearing modified mosquitoes in large cages

Posted 20th February 2020 by Dr Alekos Simoni

It is nearly five o’clock in the evening when the bright lights in the ceiling are dimming, while an orangish light is appearing from the back end of the room, mimicking the sunset, creating a clear contrast with a dark panel on the floor to simulate the horizon. This is the signal that hundreds of male mosquitoes were waiting for their most important daily activity: they start to fly in a circle mid-air like a dance over a black square marker on the floor, looking for females to mate with. Anopheles mosquitoes, the vector of human malaria, usually mate in swarms at dusk, and soon after, mated females begin their search of a prey (usually large mammals) to suck up the blood they need to produce eggs. Here, at the Genetics and Ecology Research Centre of Polo of Genomics, Genetics and Biology (Polo GGB) in Terni (an hour drive north of Rome, Italy) we feed our mosquitoes with a synthetic membrane loaded off cow blood.

Target Malaria’s insectary in Terni, Italy. from Target Malaria on Vimeo.

The Genetics and Ecology Research Centre hosted at Polo GGB is a unique state-of-the-art infrastructure where four climatic chambers can be set to reproduce tropical environment in terms of light quality, temperature and humidity best adapted to rear and study Anopheles mosquitoes. Two of those chambers are equipped with 9 large cages, from 4.6m² to almost 10m² each, where hundreds, or even thousands, of mosquitoes can be monitored and studied.

These large cages allow more realistic and complex behaviours to be observed in lab settings, and more accurate data on mosquito fitness and behaviour can be generated, compared to standard small-size cages used to rear mosquitoes (usually as big as a shoe box). The cages at Polo GGB are within a high-containment area (Arthropod Containment Level 2-ACL2), that prevents mosquitoes from escaping and testing follows the highest standard of safety and containment.

Polo GGB is a not-for-profit organization, partner of Target Malaria. We like to see ourselves as the bridge between the Crisanti molecular lab at Imperial College London, where genetically modified mosquitoes are engineered; and the sites in Africa, where Target Malaria mosquitoes could one day help reduce the burden of malaria. At Polo GGB we rear and test wild-type and modified Anopheles in both small- and large-size cages. We gather several important parameters and fitness data, necessary to understand if these mosquitoes are ‘fit for the field’. Data at Polo GGB are also generated to inform regulatory authorities for the process of regulating the import and eventually release of modified mosquitoes on the African continent.

Some of the experiments we perform involve the use of modified mosquitoes within the large cages. At Polo GGB we also rear several wild-type mosquito strains collected from different sites in Africa, such as Burkina Faso and Mali. We then ‘introgress’, that means that we transfer a genetic modification from the lab strain (initially used to engineer the mosquito genome, a strain that has been in culture for over 40 years) into the African mosquito strains by a series of consecutive back-crossings. This means the mosquito strains we test in the lab are genetically the closest to the wild mosquitoes they would encounter in the field, were they to be released.

Polo GGB plays a key role in the development of genetic control strategies under Target Malaria. Our activities are fundamental for the stepwise deployment pathway of gene drive mosquitoes from the lab to the field.