STOP researchers collaborate in a study performed in Southern Mozambique, where both diseases are endemic. The study analysed immune responses in people exposed to both types of parasites.
A school in Manhiça. Author: Berta Grau
Malaria and helminthiasis are two common diseases in tropical and subtropical regions, particularly among poor populations with limited access to drinking water and sanitation. Hence, the probability that both parasites will end up infecting the same person is high.
“We know that the malaria parasite (P. falciparum) and helminths induce different types of immune response,” explains Carlota Dobaño, ISGlobal researcher and senior co-author of the study. The former induces what is called a Th1 response, characterised by the productionof IgG1 and IgG3 antibodies and effective in eliminating intracellular parasites. In contrast, helminths induce a less inflammatory Th2-type response, more effective against extracellular parasites and mediated by IgE and IgG4 antibodies. “We therefore wondered how is the immune response in someone who has been infected by both parasites”, says Dobaño.
To answer that question, STOP researchers- including project leader Jose Muñoz- and a team at the Manhiça Health Research Center (CISM), worked hand in hand with researchers from the Malaria Programme at ISGlobal, to determine the type of antibodies recognising both parasites in a cohort living in Manhiça, a district in Southern Mozambique where both infections are endemic
The study included 715 children and adults from six locations in Manhiça, for which detailed socioeconomic information was also available. The research team analysed the level and type of antibodies against 16 P. falciparum antigens and 11 antigens from different helminths. In addition, they determined whether the participants were infected at that moment or had been previously exposed to the parasites.
The results show that 83% of participants were infected, or had been previously infected, by both parasites. This coinfected or coexposed group (which concentrated most of the adults) had higher levels of total IgE and IgG and a higher diversity of IgG antibodies against both parasites (i.e. capable of recognising a higher number of antigens from both parasites), as compared to those who had only been infected by one type of parasite. In addition, coinfection among children was associated with a trend towards a higher load of P. falciparum parasites.
“We think that the observed increase in antibodies reflects a higher exposure to the parasite,” says Rebeca Santano, first co-author of the study together with Rocío Rubio. “This suggests that P. falciparum infections create an “immune environment” that facilitates helminth infections, and vice versa,” she adds.
The majority of adults belonged to the coinfected or coexposed group, but this was not associated with socioeconomic factors or access to water and sanitation. “However, we cannot discard the role of other factors, such as malnutrition, in increasing susceptibility to both infections in this population,” says Gemma Moncunill, senior co-author of the study.
“One of the strengths of this study is that it also included people who were not infected at the moment, but had been previously infected by P. falciparum or helminths,” say the authors. This is particularly relevant in endemic areas where repeated infections can leave a footprint on the immune system, affecting the way it responds to subsequent infections.
Reference
Rebeca Santano, Rocío Rubio, Berta Grau-Pujol, Valdemiro Escola, Osvaldo Muchisse, Inocência Cuamba, Marta Vidal, Pau Cisteró, Gemma Ruiz-Olalla, Ruth Aguilar, Maria Demontis, Jose Carlos Jamine, Anélsio Cossa, Charfudin Sacoor, Jorge Cano, Luis Izquierdo, Chetan E. Chitnis, Ross L. Coppel, Virander Chauhan, David Cavanagh, Sheetij Dutta, Evelina Angov, Deepak Gaur, Lisette van Lieshout, Bin Zhan, Jose Muñoz, Gemma Moncunill, Carlota Dobaño. Plasmodium falciparum and helminth coinfections increase IgE and parasite-specific IgG responses. Microbiology Spectrum. 2021.