Researchers at UT Southwestern Medical Centre have discovered a reproductive mechanism of the organism responsible for malaria, a finding that may harbour the possibility of developing new vaccines for the mosquito borne disease.

The study revealed that sexual reproduction begins with two genetically different steps. First, two reproductive cells must latch onto each other with one protein, and secondly, they must fuse their membranes to form a single cell using a different protein.

The researchers conducted the study using a single-celled green alga nicknamed Chlamy (Chlamydomona) found in soil and water and which is easy to grow and study under laboratory conditions.

When they blocked the "male" and "female" malarial cells from fusing, spread of the mosquito-borne disease was stopped.

"A silly little green scum has led us to an exciting new vaccine target for malaria," said Dr. William Snell, professor of cell biology at UT Southwestern and co-senior author of the study.

He also said that understanding fertilization in microorganisms might lead to a new type of vaccine, called 'altruistic' vaccine.

The fusion of the parasite is controlled by a gene not found in mammals, so blocking this step might prove effective in stanching the spread of the disease without harming humans, said Snell.

After realizing that Plasmodium species, including the one that causes malaria in humans, also use "male" and "female" cells to reproduce, Dr. Snell contacted malaria researchers at Imperial College London to test whether HAP2, a gene that controlled whether cells fused, might be involved in reproduction in that organism and in the spread of malaria.

The British researchers found that blocking HAP2 in Plasmodium cells stops the fusing step.

When mutant Plasmodium organisms lacking HAP2 were injected into mice, mosquitoes that bit the mice did not become infected with Plasmodium and therefore could not spread the infection to other mice.

"There has been a lot of speculation about species-specific egg-sperm binding and fusion and whether the two steps involve the same or different proteins, but no one had the molecules to show this," Dr. Snell said.

"There has been a lot of speculation about species-specific egg-sperm binding and fusion and whether the two steps involve the same or different proteins, but no one had the molecules to show this," said Dr. Snell.

The study appears online and will be published in the April 14 issue of the journal Genes and Development.