PfRH2a

PfRH2a, or Plasmodium falciparum reticulocyte-binding protein homologue 2a, is a member of the PfRH family of merozoite invasion ligands in the malaria parasite Plasmodium falciparum. The PfRH proteins are secreted from parasite rhoptries during the invasion of erythrocytes and contribute to the recognition and attachment processes that lead to red blood cell entry. PfRH2a is one of several paralogs, including PfRH2b, PfRH1, PfRH4, and the well-studied PfRH5, that together support alternative pathways for invasion.

Localization and expression of PfRH2a have been described in the context of the late stages of schizogony, with the protein or its fragments detected at the merozoite surface or in rhoptry-derived secretions in various studies. Its expression patterns can vary between parasite strains, contributing to differences in invasion preferences and receptor usage among isolates.

Functionally, PfRH2a is believed to participate in erythrocyte invasion by binding to specific receptors on the red blood cell surface. Invasion is a multi-ligand process, and PfRH2a often acts in redundancy with other invasion ligands such as PfRH2b or PfRH4. This redundancy allows parasites to switch invasion pathways in response to immune pressure or receptor availability, a phenomenon known as invasion plasticity.

Genetic variation in PfRH2a, including strain-dependent differences in sequence and expression, reflects ongoing adaptation to host immunity. While PfRH2a is not currently a primary vaccine target like PfRH5, understanding its role helps explain the complexity of parasite invasion and the challenges of eradicating malaria through invasion-blocking strategies.