New experimental vaccine may boost fight against malaria

A new experimental malaria vaccine may offer long-lasting immunity against the persistent parasite that infects hundreds of millions of people each year, a study suggests.

The approach, described in the journal PLOS ONE, uses a cytomegalovirus-based platform that is already being used in vaccines developed to battle HIV and tuberculosis.

This new vaccine reduced the malaria-causing parasite's release from the liver and into the blood of infected rhesus macaques by 75 to 80 per cent.

"The problem with most vaccines is that their effectiveness is often short-lived," said Klaus Fruh, a professor at the Oregon Health & Science University (OHSU) in the US.

"Our cytomegalovirus-based vaccine platform can create and keep immunity for life. With further research and development, it could offer a lifetime of protection against malaria," Fruh said.

Malaria is a serious and sometimes fatal disease caused by Plasmodium parasites, which are spread to humans through mosquito bites.

It can cause high fevers, shaking chills, flu-like illness and, in the worst cases, death. Worldwide, 216 million people were infected with malaria in 2016, leading to 445,000 deaths. The vast majority of infections occur in Africa, researchers said.

The decades-long search for an effective malaria vaccine has been challenging.

The World Health Organization (WHO) is using one vaccine -- known as RTS,S/AS01 -- as part of new, routine vaccination programmes in three African countries.

However, RTS,S has been shown to only reduce malaria transmission in kids -- in whom malaria is most often fatal -- by 39 per cent four years after it was administered.

Its efficacy was further reduced to 4.4 per cent seven years afterwards. Vaccines against viruses and bacteria typically have protection rates of more than 90 per cent.

Most vaccines are designed to encourage the human body to respond to invading, disease-causing pathogens by creating antibodies that disable those pathogens.

The new vaccine takes a different approach by using a weakened form of a common herpes virus -- cytomegalovirus, or CMV -- that infects most people without causing disease.

Fruh and his colleagues weave tiny bits of their target pathogen into CMV. Those who receive the resulting, re-engineered CMV vaccine produce memory T-cells that can search for and destroy pathogen-infected cells.

Studies have shown this approach enables vaccinated nonhuman primates to develop and maintain a high state of immunity years later.

The CMV vaccine platform has been licensed by US-based Vir Biotechnology which plans to lead a human clinical trial for a CMV-based HIV vaccine in 2019.