The scientists found the proteins after investigating the reproductive habits of the Chlamydomonas algae. While this single celled organism can reproduce asexually, under adverse conditions the cells divide to produce sex cells, which roughly correspond to male and female sex cells, which then merge to produce a zygote in a similar manner to sexual reproduction.

According to Dr William Snell of the UT Southwestern Medical Centre in the USA, this zygote is more hardy to nutrient loss than the adult cells, allowing it to survive in harsher conditions.

By studying the molecular mechanisms surrounding the merging of these two sex cells, Snell and his team identified the protein that allowed the "male" sex cell to latch onto the female sex cell, and the protein that then allowed the two cells to fuse once this step had taken place. Snell's work will be published in the 14 April issue of Genes and Development.

Snell collaborated with researchers at Imperial College London to discover that the Plasmodium protozoa, which causes malaria, also reproduces sexually, using this same two step process, while it is carried in the mosquito's gut. In particular, they found that the same gene, HAP2, which codes for the protein that allows the two sex cells to fuse together once they have met, is also found in the Plasmodium protazoa.

"The intriguing part is that they can reproduce asexually in a infected person, but the Plasmodium in the red blood cells only emerges and turns into sex cells when ingested by a mosquito," Snell told LabTechnologist.com.

According to Snell, the adult protozoa are less hardy, whereas the zygote formed from these two sex cells can survive and crawl out of the gut of the mosquito to infect its body. Once the mosquito is infected, it can transmit malaria to other people that it bites.

However, if scientists could find a way to prevent the two cell cells from fusing, the zygote would not be formed and the plasmodium protozoa could not leave the gut of the mosquito, preventing it from itself being infected and in turn from infecting other people.

Snell believes that a new "altruistic vaccine" could trigger the human body into producing antibodies that targets the HAP2 protein. These antibodies would be ingested by the mosquito and would act in its gut to prevent the zygote from forming.

While this vaccine would not help someone who has actually been infected to fight the disease, it would mean that they could not transmit the disease to anyone else, hence the term "altruistic vaccine".

Currently, however, no vaccine has been found that targets these proteins, but Snell remains optimistic that this will be discovered in the future. "It could be that it's impossible to create a vaccine to block this protein, but we're hopeful that this will not be the case," he said.