At a presentation during the 60th annual meeting of the American Society of Tropical Medicine and Hygiene, three leaders in malaria vaccine development announced their collaboration of assessing a potential vaccine candidate designed to prevent transmission of malaria from mosquitoes to humans. Researchers believe that the type of vaccine could contribute to the eventual eradication of malaria.

The partners – the PATH Malaria Vaccine Initiative (MVI), the National Institute of Allergy and Infectious Diseases (NIAID) and the Johns Hopkins Bloomberg School of Public Health Center for Immunization Research (CIR) – will collaborate on conducting a Phase 1 clinical trial in healthy adults to assess the safety and immunogenicity of the protein Pfs25 in a conjugated vaccine developed at NIAID.

Malaria claims almost 800,000 lives each year, with most of the victims being African children younger than 5 years. The battle against the disease has been challenging, as both the parasite and the mosquito host are highly adaptive and have survived for thousands of years. Even though drugs and insecticides have had a substantial effect on the burden of disease, the resistance of the parasite and mosquito continues to pose an ongoing threat.

The TBV Pfs25 approach aims to block malaria from being transmitted from mosquitoes to humans by preventing the malaria parasite from developing in the mosquito, and although such a vaccine would not directly protect an immunized individual from developing clinical malaria, it would reduce the chances that others in the community contract malaria by preventing the spread of infection by the mosquito.

A transmission-blocking vaccine (TBV) would work in combination with drugs and insecticides by blocking the transmission of the parasite. This would decrease the demand on other measures, therefore slowing the development of resistance and subsequently extend their effectiveness.
v Ashley Birkett, PhD, director of research and development at MVI, said:

“This is the first clinical trial supported by MVI to use a transmission-blocking approach. This is the first step in what is typically a long process of evaluation. Nonetheless, we are excited by the potential of TBVs to significantly limit the spread of malaria infection. Eradication of malaria may be decades away, but we believe a successful TBV – used alongside safe and effective drugs, insecticides, bed nets, and possibly a malaria vaccine that protects the individual against infection and disease – would be essential to achieving that goal.”

Kawsar Talaat, MD, clinical principal investigator and assistant scientist at the Bloomberg School added:

“The Pfs25 vaccine and other transmission blocking vaccines are unique in their approach in that they target a key stage of the malaria parasite’s lifecycle rather than attempting to build immunity to malaria in humans. We’ll need many tools to defeat malaria and an effective transmission-blocking vaccine could go a long way toward achieving that goal.”

Petra Rattue