Association between Immunoglobulin G Subtypes Immune responses to Plasmodium falciparum Merozoite Surface Protein 1-19  and Malaria

Emmanuel Athanase; Arnold Ndaro; Linda Minja; Jaffu Chilongola

Emmanuel Athanase Kilimanjaro Christian Medical University College, P.O.Box 2240, Moshi, Tanzania.
Arnold Ndaro Kilimanjaro Clinical Research Institute, P.O.Box 2236, Moshi, Tanzania and Kilimanjaro Christian Medical Centre, P.O.Box 3010, Moshi, Tanzania.
Linda Minja Kilimanjaro Clinical Research Institute, P.O.Box 2236, Moshi, Tanzania.
Jaffu Chilongola Kilimanjaro Christian Medical University College, P.O.Box 2240, Moshi, Tanzania.

Keywords: MSP1-19 antigen, IgG subtypes, malaria, immunity, falciparum

Abstract

Aims: To determine Immunoglobulin G (IgG) subtypes (IgG1, IgG2, IgG3 and IgG4) responses to PfMSP1-₁₉ antigens and their associations with malaria across different age groups.

Study Design: A community based cross sectional study.

Place and Duration of Study: Bondo Ward, in Handeni district of Tanga Region between January and May 2016.

Methodology: We included 331 participants; 216 females, 115 males aged between 1 and 82 years, with a median age of 10 years and an inter-quartile range 5 -30 years. Two milliliters of blood was collected from each participant in EDTA coated tubes for detection of malaria and serology. Anti-MSP1-19 IgG subtypes were measured by indirect ELISA based on a protocol developed by Afro Immuno-Assay Consortium. Demographic data were collected using designed record form.

Results: Out of 331 participants, 68 (20.5%) were malaria positive. We report malaria prevalence to be highest in the age category of between 6 and 15 years, compared to individuals above 15 years (OR= 4.5; 95% CI = 2.28.9). Most participants were seropositive for total IgG (87.0%), IgG1 (78.5%) and IgG3 (52.9%). Concentration (optical densities) of total IgG, IgG1 and IgG3 was generally lower in the 1-5 year age category. There was no clear pattern for IgG 2 and IgG4 seropositivity across age categories. After adjusting for age, only IgG1 seropositivity was significantly associated with lower malaria prevalence in all age categories (OR=0.4; 95% CI = 0.2 0.8).

Conclusion: IgG1subtype to MSP1-₁₉is associated with lower malaria prevalence which may imply its possible suitability a target of a prospective malaria vaccine. We report a high prevalence of malaria in the study area, with highest malaria prevalence recorded in older children of 6-15 years of age. Our findings show that only IgG1 antibody to MSP1-19 is associated with low malaria prevalence, suggesting a possible protective role of the subtype against malaria. We report very low responses and seropositivity of IgG2 and IgG4 subtypes. Based on our present findings, IgG1 to MSP1-19 could be an important target of a prospective malaria vaccine.