New insights into immunity to malaria in pregnancy

A Burnet-led evaluation of 20 years of research has found little evidence to associate any specific antibody response with protection from malaria in pregnancy, a finding with important implications for malaria vaccine development.

During their first pregnancy is when women in endemic areas are most at risk from the devastating outcomes of malaria, including maternal mortality, stillbirth, miscarriage, low birth weight, preterm birth, and anaemia.

Over successive pregnancies, however, women typically develop resistance or immunity to malaria in pregnancy due, it’s assumed, to the acquisition of antibodies to malaria parasite antigens.

“In order to identify suitable parasite antigens to develop vaccines, we need to understand more about the immune responses that actually protect women from malaria,” Dr Julia Cutts, research lead author, said.

“A lot of studies have looked at this, but our study is the first to pool all available data to determine whether there is a protective effect of pregnancy-specific malarial antibodies to specific antigens across pregnant women living in different geographical locations.

“We examined 33 studies from multiple populations, but when you look at them together, the evidence is not strong for any specific antibody response being associated with protection from malaria in pregnancy.

“This suggests that perhaps women need a broad range of antibodies to develop that immunity, or perhaps the methods that have been used to study antibody responses in the lab don’t really capture what’s going on in the body.”

Senior author, Professor Freya Fowkes, said the study findings suggest more research is needed across a broad range of geographical regions looking at antibody responses to malaria in pregnancy throughout the whole duration of a woman’s pregnancy.

“While the development of a pregnancy-specific malaria vaccine is underway, the devastating burden of malaria in pregnancy reminds us of the importance of developing and utilising a suite of interventions to prevent and treat malaria in pregnancy,” Professor Fowkes said.

“It’s still important that women receive long lasting insecticide bed nets, that they receive intermittent preventive treatment against malaria in pregnancy, and prompt diagnosis and treatment of malaria infections when they do occur in pregnancy to prevent the terrible outcomes for both the mother and child.”

The publication of the study in the journal BMC Medicine coincides with early stage clinical trials underway for two vaccines specifically for malaria in pregnancy.

Dr Cutts said a vaccine for malaria in pregnancy is much needed and would probably work differently from other vaccines.

“Malaria in pregnancy involves a particular interaction between a specific parasite strain that sticks to the lining of the maternal blood space in the placenta, so a vaccine targeting malaria in pregnancy would aim to prevent that interaction,” Dr Cutts said.

“Being able to demonstrate that a particular antigen is a specific target of a protective immune response is important for developing effective vaccines for malaria in pregnancy and for developing new tools that will allow us to detect whether women have been exposed to malaria in pregnancy.”

This research was conducted in collaboration with Monash University and the University of Melbourne.

Find out more about Burnet’s malaria research.