Subject(s)
Antigens, Protozoan/genetics , Cysteine Endopeptidases/genetics , Genes, Protozoan , Plasmodium/genetics , Amino Acid Sequence , Animals , Antigens, Protozoan/chemistry , Antigens, Protozoan/metabolism , Cysteine Endopeptidases/chemistry , Cysteine Endopeptidases/metabolism , Molecular Sequence Data , Plasmodium/enzymology , Plasmodium/growth & development , Plasmodium/immunology , Protozoan Proteins/chemistry , Protozoan Proteins/genetics , Protozoan Proteins/metabolism , Sequence Alignment , Sequence Homology, Amino AcidABSTRACT
The Plasmodium falciparum serine repeat antigen (SERA) and serine repeat protein homologue (SERPH) contain highly conserved domains that appear to encode cysteine proteases or related proteins. Humoral immune responses against the protease domains of SERA and SERPH were evaluated. Malaria-immune Africans, but not nonimmune controls, demonstrated potent humoral responses against the protease domains. As the SERA and SERPH protease domains are likely accessible to circulating antibody, these results suggest that humoral responses to the domains may contribute to antimalarial immunity.
Subject(s)
Antibodies, Protozoan/blood , Antigens, Protozoan/immunology , Cysteine Endopeptidases/immunology , Malaria, Falciparum/immunology , Plasmodium falciparum/immunology , Adolescent , Adult , Africa , Aged , Animals , Antibodies, Protozoan/immunology , Antibody Specificity , Antigens, Protozoan/genetics , Cysteine Endopeptidases/genetics , Female , Humans , Male , Middle Aged , Plasmodium falciparum/geneticsABSTRACT
The Plasmodium falciparum proteins serine repeat antigen (SERA) and serine repeat protein homologue (SERPH) have similarity in sequence with cysteine proteases in a well-conserved protease domain. We identified three SERA homologues from the murine malaria parasite Plasmodium vinckei and evaluated immune responses to the protease domains of these proteins. Mice that developed protective immunity to P. vinckei after serial infection and cure demonstrated humoral and cell-mediated responses against the SERA homologue protease domains. Mice immunized with Salmonella typhimurium expressing the protease domain of one of these antigens demonstrated cellular responses against the antigen and increased survival against lethal challenge with P. vinckei. Our results suggest that the protease domains of SERA and SERPH are worthy of additional study as potential components of a malaria vaccine.