Effect of GPI anchor moiety on the immunogenicity of DNA plasmids encoding the 19‐kDa C‐terminal portion of Plasmodium falciparum MSP‐1

Abstract

SUMMARY The glycosylphosphatidylinositol (GPI)‐anchored Plasmodium falciparum merozoite surface protein 1 (MSP‐1) is a widely studied malaria vaccine candidate. The C‐terminal 19‐kDa portion of MSP‐1 (MSP‐119) is of particular interest because this polypeptide moiety remains bound to the parasite even after erythrocyte invasion, while the remainder of MSP‐1 is shed during invasion. Studies have shown that antibodies against MSP‐119 inhibit merozoite invasion of erythrocytes efficiently, and that MSP‐119 produces protective immunity in mice and monkeys. To investigate the efficacy of MSP‐119 DNA vaccine and role of GPI anchor moiety in the immunogenicity of MSP‐119, we constructed expression vectors that produce MSP‐119 as either secretory or GPI‐anchored polypeptide. Both constructs efficiently expressed MSP‐119 in transfected HEK‐293 cells. While the recombinant plasmid lacking GPI anchor signal sequence expressed MSP‐119 mainly as secreted polypeptide, that containing GPI anchor signal sequence produced GPI‐anchored MSP‐119 on cell surface. In immunized mice, both constructs produced substantial levels of MSP‐119‐specific IgG1, IgG2a, IgG2b, IgG3, IgA and IgM antibodies. In both cases, the IgG1 level was significantly higher than other isotypes. Interestingly, the plasmid containing GPI anchor signal sequence produced significantly higher levels of IgG2a and IgG2b than the plasmid that lacks GPI signal sequence.

An Erythrocyte Membrane-Associated Antigen, PvTRAg-26 of Plasmodium vivax: A Study of Its Antigenicity and Immunogenicity

“…Immunization with recombinant PvTRAg-26 resulted in a high level of IgG antibody response in mice, in which IgG1 subclass was predominant, followed by IgG2a. Similar results were also seen in the studies of mice with other malaria vaccine candidates, such as PvMSP1 19 , PfMSP1 19 , and PvMSP9 (34)(35)(36). The IgG1 and IgG3 antibodies are non-cytophilic and responsible for Th2-biased response (37), while the IgG2a and IgG2b are cytophilic and link to Th1 response in mice.…”

Immune responses elicited by co‐immunization of Plasmodium vivax and P. falciparum MSP‐1 using prime‐boost immunization strategies

“…Antibody to the C-terminal region of this protein (MSP-1 19 ) has been shown to block parasite invasion in vitro (11)(12)(13). Earlier studies have demonstrated that immune responses elicited separately by PvMSP-1 19 (14,15) or PfMSP-1 19 (16)(17)(18) antigens in mice induced high levels of IgG1 antibodies followed by IgG2a and IgG2b as well as a high level of IFN-c. A partial protection was also observed after immunization of nonhuman primates with PfMSP-1 19 (5) and PvMSP-1 19 (19). In addition, several studies on naturally acquired immunity showed that the antibodies (IgG1 and IgG3) against this antigen are correlated with protection (20)(21)(22)(23).…”

Recombinant proteins of Plasmodium malariae merozoite surface protein 1 (PmMSP1): Testing immunogenicity in the BALB/c model and potential use as diagnostic tool

“…The five recombinant proteins induced similar antibody patterns, being IgG1, IgG2a and IgG2b the most predominant. Previous studies have shown that immune responses induced by PvMSP1 19 antigens [35,36] or PfMSP1 19 [37,38,39] in mice confer high levels of IgG1 subclasses, followed by IgG2a and IgG2b. Others authors also found similar results with recombinant proteins derived from PvMSP9 [40].…”