Parasites only mate when enough

For years, microbiologist Dr Stephen Beverley has tried to make the parasite Leishmania mating. On the Science page this week, he and his colleagues at the National Institutes of Health reported that they finally found the answer: putting enough Leishmania individuals into the intestines of insects called sand flies , these parasites will conduct sexual intercourse.

Several species of parasites are deadly and kill hundreds of thousands of people every year in developing countries. The individual child born from the mating of these parasites may hold the gene key to neutralize the poison. This achievement may be an important step in identifying the genes that determine the parasite's toxicity. That may promote the development of new therapies for these infections.

'Our idea is to try to breed less toxic species with more poisonous species, and to study the younger generation to find out the factors that retain the ability to cause serious poisoning,' said Beverley, a professor at the university. Marvin A. Brennecke and head of Molecular Microbiology research team said. 'With the observation of which components of the genetic material of the poisoned parent are passed on to the poisoned offspring, we will be able to identify the gene segments that control the potential for toxicity. indeed of this parasite. "

Along with Beverley, the co-author of the report is Master David Sacks, a researcher at the National Institutes of Health specializing in sand flies and parasitic immunity. The infectious parasite Leishmania, also known as Leishmaniasis, is mainly spread through sand fly bites, which is a serious problem in public health in Asia, Africa, the Middle East and other countries. other developing countries.

Symptoms include extensive lesions on the skin, fever, swelling of the spleen and liver, and even facial deformities in severe cases.

The most dangerous form of Leishmaniasis, a condition sometimes called black fever, is a fatal disease if left untreated; It is estimated that this form kills more people than any other parasite, except Plasmodium, a malaria-causing parasite.

Like many microorganisms, Leishmania can reproduce by asexual reproduction through the creation of individual animals containing genetic material from more than one parent - this form is equivalent to mating. Now, researchers can only find mating in Leishamnia in its final product: an individual with an unusual genetic mixture.

Sand flies, such as the species Phlebotomus papatasi are the main culprits in spreading infectious diseases of Leishmaniasis;this is caused by intracellular protozoa of Leishmania species.(Photo: CDC Frank Collins)

After more than 20 years of trying to make Leishmania breed through mating while it is not known if this species has ever reproduced sexually, Beverley and Sacks have recently found that the answer is to give some. certain individuals enter the sand fly body. Master Natalia Akopyants, tutor in Molecular Microbiology at vWashington University, has discovered atomic parasites through genetic analysis.

'Our theory, though unproven, is that this is a matter of quantity,' Beverley said. 'Every time we get enough parasites in a fly body, we see sexual reproduction. If we don't have enough of this quantity, we won't see any mating phenomenon. '

The activity within the body of the sand fly is not particularly special: most parasites conduct asexual reproduction instead of mating. The mechanisms of sexual reproduction in Leishmania species are still unclear. For example, it is still unclear whether they are in the form of egg-like and sperm-like gametes, each of which contains half of the genes and then coalesce to form a perfect gene-like body in high organisms. more or not.

Beverley hopes to develop a tool to better understand Leishmania bodies as they are making sexual reproduction, so that researchers can better understand what happens during mating and from It quickly identifies the factors that promote this process in the intestine of flies.

'If we can clearly see the parasites that are in the mating process, we will get some kind of idea like what song we can give them to make mating in the medium of implantation. ' he said.

Beverley noted that the new research could not have been carried out without the knowledge of Sacks about sandflies, but he wanted to find ways to remove sand flies from genetic experiments and study Leishmania only in the environment. culture.

'In nature, there are important interactions that take place between the sandfly body and the parasite, we need to understand that, and as the world's leading researcher in this area, Sacks' capabilities are extremely necessary, 'he said. 'But our goal is to find genes that make Leishmania dangerous to humans, so we will stop the research method by transplanting this parasite into the body of sand flies to save time and money. charge. '

The research was supported by the National Institutes of Health Research and the National Institute for Infectious Diseases and Allergies.

References:
Akopyants NS, Kimblin N, Secundino N, Patrick R, Peters N, Lawyer P, Dobson DE, Beverley SM, Sacks DL.Gene exchange during the periodic development of Leishmania parasites in sandfly insects.Journal of Science, April 10, 2008