Construction and immunogenicity in mice of attenuated Salmonella typhi expressing Plasmodium falciparum merozoite surface protein 1 (MSP-1) fused to tetanus toxin fragment C.
One strategy to develop a multi-antigen malaria vaccine is to employ live vectors to carry putative protective Plasmodium falciparum antigens to the immune system. The 19 kDa carboxyl terminus of P. falciparum merozoite surface protein 1 (MSP-1), which is essential for erythrocyte invasion and is a leading antigen for inclusion in a multivalent malaria vaccine, was genetically fused to fragment C of tetanus toxin and expressed within attenuated Salmonella typhi CVD 908. Under conditions in the bacterial cytoplasm, the fragment C-MSP-1 fusion did not form the epidermal growth factor (EGF)-like domains of MSP-1; monoclonal antibodies failed to recognize these conformational domains in immunoblots of non-denatured protein extracted from live vector sonicates. The MSP-1 was nevertheless immunogenic. One month following intranasal immunization of BALB/c mice with the live vector construct, four out of five mice exhibited > or =four-fold rises in anti-MSP-1 by ELISA (GMT=211); a single intranasal booster raised titers further (GMT=1280). Post-immunization sera recognized native MSP-1 on merozoites as determined by indirect immunofluorescence. These data encourage efforts to optimize MSP-1 expression in S. typhi (e.g. as a secreted protein), so that the EGF-like epitopes, presumably necessary for stimulating protective antibodies, can form.
Wu
S
S
Center for Vaccine Development and the Division of Geographic Medicine, Department of Medicine, University of Maryland, School of Medicine, 685 West Baltimore Street, Baltimore, MD 21201, USA.
Beier
M
M
Sztein
M B
MB
Galen
J
J
Pickett
T
T
Holder
A A
AA
Gómez-Duarte
O G
OG
Levine
M M
MM
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D018928:Immunity, Mucosal; D020066:Merozoite Surface Protein 1 / Q000235:genetics* / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000235:genetics*; D010963:Plasmodium falciparum / Q000276:immunology*; D012485:Salmonella typhi / Q000235:genetics* / Q000276:immunology*; D013744:Tetanus Toxin / Q000235:genetics*
D017931:DNA Primers; D020066:Merozoite Surface Protein 1; D010446:Peptide Fragments; D013744:Tetanus Toxin; C040635:tetanus toxin fragment C