Structure and function of a thymic peptide is mimicked by Plasmodium falciparum peptides

Numerous Plasmodium falciparum antigens contain repetitive amino acid sequences. Two blood stage antigens, Pf11-1 and Pf332, were characterized in our laboratories and present high cross-reactivities, defining a family of cross-reacting antigens. In this report, we show that amino acid sequence homologies might explain these cross-reactivities, but that they extend to polypeptides from the host, namely thymosin-α1 (Tα1). An antiserum raised in chickens and Saimiri monkeys against the synthetic Pf11-1 peptide cross-reacts with synthetic Tα1. Synthetic Pf11-1 and Pf332 peptides share some of the biological activities of Tα1. These results are discussed with respect to the mechanisms devised by malaria parasites for escape from the host immune response.