Influence of α₂-Macroglobulin, Anti-Parasite IgM and ABO Blood Group on Rosetting in Plasmodium falciparum Clinical Isolates and Their Associations with Disease Severity in a Ghanaian Population

Abstract

Purpose

The severity of Plasmodium falciparum infections is associated with the ability of the infected red blood cells to cytoadhere to host vascular endothelial surfaces and to uninfected RBCs. Host blood group antigens and two serum proteins α₂-macroglobulin (α₂M) and IgM have been implicated in rosette formation in laboratory-adapted P. falciparum. However, there is only limited information about these phenotypes in clinical isolates.

Methods

This was a hospital-based study involving children under 12 years-of-age reporting to the Hohoe Municipal Hospital with different clinical presentations of malaria. Parasite isolates were grown and rosette capabilities and characteristics were investigated by fluorescence microscopy. α₂M and IgM were detected by ELISA.

Results

Rosette formation was observed in 46.8% (75/160) of the parasite isolates from all the blood groups tested. Rosettes were more prevalent (55%) among isolates from patients with severe malaria compared to isolates from patients with uncomplicated malaria (45%). Rosette prevalence was highest (30%) among patients with blood group O (30%) and B (29%), while the mean rosette frequency was higher in isolates from patients with blood group A (28.7). Rosette formation correlated negatively with age (r = −0.09, P= 0.008). Participants with severe malaria had a lower IgM concentration (3.683±3.553) than those with uncomplicated malaria (5.256±4.294) and the difference was significant (P= 0.0228). The mean concentrations of anti-parasite IgM measured among the clinical isolates which formed rosettes was lower (4.2 ±3.930 mg/mL), than that in the non rosetting clinical isolates (4.604 ±4.159 mg/mL) but the difference was not significant (P=0.2733). There was no significant difference in plasma α₂M concentration between rosetting and non rosetting isolates (P=0.442).

Conclusion

P. falciparum parasite rosette formation was affected by blood group type and plasma concentration of IgM. A lower IgM concentration was associated with severe malaria whilst a higher α₂M concentration was associated with uncomplicated malaria.

Keywords:

• Plasmodium falciparum
• severe malaria
• uncomplicated malaria
• rosettes
• blood group
• alpha-2 macroglobulin
• immunoglobulin M

Abbreviations

α₂M, alpha 2 macroglobulin; CR1, complement receptor 1; ELISA, enzyme linked immunosorbent assay; ERC, ethical review committee; GHS, Ghana health service; HRP, horse radish peroxidase; HS, heparan sulphate; IgM, immunoglobulin M; IRBC, infected red blood cells; MOH, ministry of health; NHS, normal human serum; OD, optical density; OPD, out patient department; PBS, phosphate buffered saline; PBST, phosphate buffered saline 0.1% Tween 20 detergent; PfEMP1, plasmodium falciparum erythrocyte membrane protein 1; RBC, red blood cells; RDT, rapid diagnostic test; RIFIN, P. falciparum-encoded repetitive interspersed families of polypeptides; RPMI, Roswell Parks Memorial Institute; SM, severe malaria; STEVOR, subtelomeric variable open reading frame; TMB, 3,3′,5,5′-tetramethylbenzidine; UM, uncomplicated malaria; VSA, variant surface antigens.

Data Sharing Statement

The datasets analysed in this study are available from the corresponding author on reasonable request.

Acknowledgments

The authors are grateful to the parents and guardians of the children involved in the study. Special thanks also go to the management and staff of the Hohoe Municipal Hospital as well as the staff of the Immunology Department, NMIMR. Mr Alex Danso-Coffie is thanked for his logistic and technical support.

Author Contributions

All authors made significant contribution to the work, whether in the conception, study design, implementation, acquisition of data, analysis or interpretation. All the authors were involved in the drafting, revising and critical reviewing of the article. They all agreed on the journal to which the article has been submitted and agreed to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

Michael F. Ofori and Lars Hviid are supported by the Danish Research Council for Development Research (Grant No. 17-02-KU). The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.