POTENTIAL BREAKTHROUGH

Kenyans 100% resistant to malaria found, hopes high for better jab

The knowledge raises hopes for new approaches for the development of a broadly effective malaria vaccine.

In Summary

• Researchers infected 142 volunteers from Kilifi and Ahero with a malaria parasite from West Africa, which is genetically distant to East African parasites.

• The little understanding of how natural immunity to malaria is achieved and how it is maintained has always been proclaimed as a major hurdle to the development of a malaria vaccine.

A child gets the RTS,S malaria vaccine during the clinical trials.
A child gets the RTS,S malaria vaccine during the clinical trials.
Image: FILE

Some people from Western Kenya and the Coast are already well-known to be immune to the locally circulating malaria parasite.

Now scientists have discovered that some of these people can also completely suppress parasite strains originating from outside Kenya.

This means they are immune to malaria regardless of the source of infection.

The finding was made by researchers from the Kenya Medical Research Institute-Wellcome Trust Research Programme in Kilifi.

They infected 142 volunteers from Kilifi and Ahero with a malaria parasite from West Africa, which is genetically distant to East African parasites.

In 23.3 per cent of the volunteers, there was complete suppression of parasite growth.

“The challenge strain is genetically distant to East African parasites, implying that the complete suppression of parasite growth was the result of heterologous immunity,” they say in findings published in the JCI Insight journal.

Heterologous immunity is a phenomenon whereby a history of an immune response against one pathogen can provide some immunity to a second unrelated pathogen.

Of the 142 volunteers, only 39.5 per cent developed parasite growth leading to densities that required treatment.

In the remaining 37.3 per cent, there was limited parasite growth that was partially suppressed such that treatment criteria were not met.

The scientists said this knowledge raises hopes for new ways for the development of a broadly effective malaria vaccine.

The lack of understanding of how natural immunity to malaria is achieved and how it is maintained has always been proclaimed as a major hurdle to the development of a malaria vaccine.

The Kemri study provides the largest dataset to date on controlled human malaria infection outcomes in an adult population from a malaria-endemic area.

“It is likely that prior malaria exposure rather than human genetic differences explain the observed variations in controlled human malaria infection outcomes,” the scientists say.

They are Kemri’s Melissa Kapulu, Patricia Njuguna, Mainga Hamaluba, Domtila Kimani, Joyce Ngoi, Janet Musembi, Omar Ngoto, Edward Otieno,  and Peter Billingsley from Malaria, Sanaria Inc, of the United States.

The participants did not have history of taking antimalarials, neither did they have malaria symptoms nor sickle cell, which is also known to protect people from malaria.

Kenya has an estimated 3.5 million new clinical cases of malaria every year and 10,700 deaths, according to the Ministry of Health.

The country has also deployed RTS,S, a malaria vaccine also known as Mosquirix, in eight counties with the highest malaria burden in western Kenya: Bungoma, Busia, Homa Bay, Kakamega, Kisumu, Migori, Vihiga, and Siaya.

By May, Kenya had administered more than 450,000 doses of RTS,S, according to the Division of National Malaria Programme.