# Invasion preferences suggest a possible role for Plasmodium falciparum parasites in the expansion of Duffy negativity in West and Central Africa

## TL;DR

The study suggests that Plasmodium falciparum may influence the spread of Duffy-negative blood cells in parts of Africa.

## Contribution

The paper provides new evidence that P. falciparum preferentially invades Duffy-positive red blood cells and links this to the evolutionary spread of Duffy negativity.

## Key findings

- P. falciparum parasites preferentially invade Duffy-positive red blood cells.
- Duffy negativity increases in low transmission settings due to P. falciparum's invasion inhibition.
- DARC may play a direct or indirect role in P. falciparum invasion of human RBCs.

## Abstract

Duffy antigen receptor for chemokines (DARC) is the primary red blood cell (RBC) receptor for invasion of human RBCs by Plasmodium vivax and Plasmodium knowlesi parasites. By contrast, Plasmodium falciparum parasites use multiple RBC receptors for invasion. Whether DARC is one of these receptors has never been systematically explored. We used flow cytometry and microscopy-based approaches to investigate whether P. falciparum parasites preferentially invade specific Duffy RBC phenotypes and explored 2 potential explanations for invasion preference—differences in RBC biophysical properties and surface protein composition. P. falciparum parasites showed a consistent preference for Duffy-positive RBCs, and some biophysical properties and surface protein expression varied between Duffy-positive and Duffy-negative RBCs. We then used our in vitro invasion data to parametrize an evolutionary-epidemiological model of the relationship between P. falciparum and the FYBES allele. Our model accounts for immunity against P. falciparum virulence, gained through exposure, and thus mutations that impede infection are not always advantageous. The inhibition of P. falciparum invasion that we observed in vitro leads to FYBES frequencies increasing at low levels of P. falciparum transmission but decreasing at high levels of transmission. The impact of P. falciparum on the prevalence of Duffy negativity may therefore be most apparent in lower transmission settings. Our findings show a link between Duffy negativity and P. falciparum and suggest that DARC may directly or indirectly be involved in P. falciparum invasion of human RBCs which could, together with P. vivax, explain the distribution of Duffy negativity in sub-Saharan Africa.