A Chimeric Plasmodium falciparum Merozoite Surface Protein Vaccine Induces High Titers of Parasite Growth Inhibitory Antibodies

ABSTRACTThe C-terminal 19-kDa domain ofPlasmodium falciparummerozoite surface protein 1 (PfMSP119) is an established target of protective antibodies. However, clinical trials ofPfMSP142, a leading blood-stage vaccine candidate which contains the protective epitopes ofPfMSP119, revealed suboptimal immunogenicity and efficacy. Based on proof-of-concept studies in thePlasmodium yoeliimurine model, we produced a chimeric vaccine antigen containing recombinantPfMSP119(rPfMSP119) fused to the N terminus ofP. falciparummerozoite surface protein 8 that lacked its low-complexity Asn/Asp-rich domain, rPfMSP8 (ΔAsn/Asp). Immunization of mice with the chimeric rPfMSP1/8 vaccine elicited strong T cell responses to conserved epitopes associated with the rPfMSP8 (ΔAsn/Asp) fusion partner. While specific forPfMSP8, this T cell response was adequate to provide help for the production of high titers of antibodies to bothPfMSP119and rPfMSP8 (ΔAsn/Asp) components. This occurred with formulations adjuvanted with either Quil A or with Montanide ISA 720 plus CpG oligodeoxynucleotide (ODN) and was observed in both inbred and outbred strains of mice.PfMSP1/8-induced antibodies were highly reactive with two major alleles ofPfMSP119(FVO and 3D7). Of particular interest, immunization withPfMSP1/8 elicited higher titers ofPfMSP119-specific antibodies than a combined formulation of rPfMSP142and rPfMSP8 (ΔAsn/Asp). As a measure of functionality,PfMSP1/8-specific rabbit IgG was shown to potently inhibit thein vitrogrowth of blood-stage parasites of the FVO and 3D7 strains ofP. falciparum. These data support the further testing and evaluation of this chimericPfMSP1/8 antigen as a component of a multivalent vaccine forP. falciparummalaria.

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Evaluation of the Immunogenicity and Vaccine Potential of Recombinant Plasmodium falciparum Merozoite Surface Protein 8

Infection and Immunity ◽

10.1128/iai.00211-12 ◽

2012 ◽

Vol 80 (7) ◽

pp. 2473-2484 ◽

Cited By ~ 11

Author(s):

James R. Alaro ◽

Evelina Angov ◽

Ana M. Lopez ◽

Hong Zhou ◽

Carole A. Long ◽

...

Keyword(s):

Plasmodium Falciparum ◽

T Cell ◽

Surface Protein ◽

Merozoite Surface Protein ◽

Plasmodium Yoelii ◽

Full Length ◽

T Cell Epitopes ◽

Content Type ◽

Rich Domain ◽

Vaccine Potential

ABSTRACTThe C-terminal 19-kDa domain of merozoite surface protein 1 (MSP119) is the target of protective antibodies but alone is poorly immunogenic. Previously, using thePlasmodium yoeliimurine model, we fusedP. yoeliiMSP119(PyMSP119) with full-lengthP. yoeliimerozoite surface protein 8 (MSP8). Upon immunization, the MSP8-restricted T cell response provided help for the production of high and sustained levels of protectivePyMSP119- andPyMSP8-specific antibodies. Here, we assessed the vaccine potential of MSP8 of the human malaria parasite,Plasmodium falciparum. Distinct fromPyMSP8,P. falciparumMSP8 (PfMSP8) contains an N-terminal asparagine and aspartic acid (Asn/Asp)-rich domain whose function is unknown. Comparative analysis of recombinant full-lengthPfMSP8 and a truncated version devoid of the Asn/Asp-rich domain,PfMSP8(ΔAsn/Asp), showed that both proteins were immunogenic for T cells and B cells. All T cell epitopes utilized mapped within rPfMSP8(ΔAsn/Asp). The dominant B cell epitopes were conformational and common to both rPfMSP8 and rPfMSP8(ΔAsn/Asp). Analysis of nativePfMSP8 expression revealed thatPfMSP8 is present intracellularly in late schizonts and merozoites. Following invasion,PfMSP8 is found distributed on the surface of ring- and trophozoite-stage parasites. Consistent with a low and/or transient expression ofPfMSP8 on the surface of merozoites,PfMSP8-specific rabbit IgG did not inhibit thein vitrogrowth ofP. falciparumblood-stage parasites. These studies suggest that the further development ofPfMSP8 as a malaria vaccine component should focus on the use ofPfMSP8(ΔAsn/Asp) and its conserved, immunogenic T cell epitopes as a fusion partner for protective domains of poor immunogens, includingPfMSP119.

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Transient Deficiency of Dendritic Cells Results in Lack of a Merozoite Surface Protein 1-Specific CD4 T Cell Response during Peak Plasmodium chabaudi Blood-Stage Infection

Infection and Immunity ◽

10.1128/iai.00820-12 ◽

2012 ◽

Vol 80 (12) ◽

pp. 4248-4256 ◽

Cited By ~ 6

Author(s):

Anne-Marit Sponaas ◽

Nikolai Belyaev ◽

Mika Falck-Hansen ◽

Alexandre Potocnik ◽

Jean Langhorne

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Surface Protein ◽

Merozoite Surface Protein ◽

T Cell Response ◽

Blood Stage ◽

Cd4 T Cell ◽

Blood Stage Infection ◽

Stage Infection

ABSTRACTSplenic dendritic cells are crucial for controlling the immune response to malaria by initiating a CD4 gamma interferon (IFN-γ) response early in a blood-stage infection, which contributes to parasite clearance as well as to acute-stage immunopathology. CD8−CD11chighdendritic cells have been described previously to be important antigen-presenting cells for induction of these CD4 T cell responses in the spleens ofPlasmodium chabaudi-infected mice. However, when isolated during the period of maximum parasitemia and shortly thereafter, the dendritic cells transiently lose their ability to stimulate T cells, recovering only as the parasitemia is controlled. This loss of a CD4 T cell response is also observedin vivoduring this part of the infection. CD4 T cells from a T cell receptor-transgenic mouse recognizing a peptide of merozoite surface protein 1 (MSP1) injected into BALB/c mice during peak parasitemia proliferate poorly, and very few cells produce IFN-γ and interleukin-2 (IL-2), compared with transgenic T cells injected earlier in the blood-stage infection. CD8−dendritic cells at day 10 can process and present peptides on major histocompatibility complex (MHC) class II with an efficiency similar to that of dendritic cells from earlier in infection. The failure of the day 10 dendritic cells to activate MSP1-specific CD4 T cells fullyin vitrois associated with reduced expression of CD86 and lower production of IL-12 rather than with induction of inhibitory DC receptors or production of IL-10.

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Systematic Genetic Analysis of the Plasmodium falciparum MSP7-Like Family Reveals Differences in Protein Expression, Location, and Importance in Asexual Growth of the Blood-Stage Parasite

Eukaryotic Cell ◽

10.1128/ec.00048-10 ◽

2010 ◽

Vol 9 (7) ◽

pp. 1064-1074 ◽

Cited By ~ 24

Author(s):

Madhusudan Kadekoppala ◽

Solabomi A. Ogun ◽

Steven Howell ◽

Ruwani S. Gunaratne ◽

Anthony A. Holder

Keyword(s):

Plasmodium Falciparum ◽

Protein Expression ◽

Surface Protein ◽

Gene Families ◽

Merozoite Surface Protein ◽

Blood Stage ◽

Asexual Blood Stage ◽

Content Type ◽

Specific Proteins ◽

Proteolytic Cleavages

ABSTRACT Proteins located on Plasmodium falciparum merozoites, the invasive form of the parasite's asexual blood stage, are of considerable interest in vaccine research. Merozoite surface protein 7 (MSP7) forms a complex with MSP1 and is encoded by a member of a multigene family located on chromosome 13. The family codes for MSP7 and five MSP7-related proteins (MSRPs). In the present study, we have investigated the expression and the effect of msrp gene deletion at the asexual blood stage. In addition to msp7, msrp2, msrp3, and msrp5 are transcribed, and mRNA was easily detected by hybridization analysis, whereas mRNA for msrp1 and msrp4 could be detected only by reverse transcription (RT)-PCR. Notwithstanding evidence of transcription, antibodies to recombinant MSRPs failed to detect specific proteins, except for antibodies to MSRP2. Sequential proteolytic cleavages of MSRP2 resulted in 28- and 25-kDa forms. However, MSRP2 was absent from merozoites; the 25-kDa MSRP2 protein (MSRP225) was soluble and secreted upon merozoite egress. The msrp genes were deleted by targeted disruption in the 3D7 line, leading to ablation of full-length transcripts. MSRP deletion mutants had no detectable phenotype, with growth and invasion characteristics comparable to those of the parental parasite; only the deletion of MSP7 led to a detectable growth phenotype. Thus, within this family some of the genes are transcribed at a significant level in asexual blood stages, but the corresponding proteins may or may not be detectable. Interactions of the expressed proteins with the merozoite also differ. These results highlight the potential for unexpected differences of protein expression levels within gene families.

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CpG oligodeoxynucleotide enhances immunity against blood-stage malaria infection in mice parenterally immunized with a yeast-expressed 19 kDa carboxyl-terminal fragment of Plasmodium yoelii merozoite surface protein-1 (MSP119) formulated in oil-based Montanides

Vaccine ◽

10.1016/s0264-410x(03)00132-4 ◽

2003 ◽

Vol 21 (21-22) ◽

pp. 2923-2932 ◽

Cited By ~ 38

Author(s):

C. Hirunpetcharat ◽

J. Wipasa ◽

S. Sakkhachornphop ◽

T. Nitkumhan ◽

Y.Z. Zheng ◽

...

Keyword(s):

Malaria Infection ◽

Surface Protein ◽

Merozoite Surface Protein ◽

Plasmodium Yoelii ◽

Blood Stage ◽

Merozoite Surface Protein 1 ◽

Terminal Fragment ◽

Cpg Oligodeoxynucleotide ◽

Carboxyl Terminal ◽

Blood Stage Malaria

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Comparative Immunogenicities of Full-Length Plasmodium falciparum Merozoite Surface Protein 3 and a 24-Kilodalton N-Terminal Fragment

Clinical and Vaccine Immunology ◽

10.1128/cvi.00064-11 ◽

2011 ◽

Vol 18 (8) ◽

pp. 1221-1228 ◽

Cited By ~ 6

Author(s):

Maryam Imam ◽

Yengkhom Sangeeta Devi ◽

Akhilesh K. Verma ◽

Virander Singh Chauhan

Keyword(s):

Plasmodium Falciparum ◽

Surface Protein ◽

Merozoite Surface Protein ◽

Terminal Region ◽

Content Type ◽

Conserved Domain ◽

Terminal Fragment ◽

Falciparum Merozoite ◽

Form Part ◽

Parasite Lysate

ABSTRACTRecombinantPlasmodium falciparummerozoite surface protein 3 (PfMSP3F) and a 24-kDa fragment from its N terminus (MSP3N) that includes the essential conserved domain, which elicits the maximum antibody (Ab)-dependent cellular inhibition (ADCI), were expressed as soluble proteins inEscherichia coli. Both proteins were found to be stable in both soluble and lyophilized forms. Immunization with MSP3F and MSP3N formulated separately with two human-compatible adjuvants, aluminum hydroxide (Alhydrogel) and Montanide ISA 720, produced significant antibody responses in mice and rabbits. Polyclonal Abs against both antigens recognized native MSP3 in the parasite lysate. These two Abs also recognized two synthetic peptides, previously characterized to possess B cell epitopes from the N-terminal region. Antibody depletion assay showed that most of the IgG response is directed toward the N-terminal region of the full protein. Anti-MSP3F and anti-MSP3N rabbit antibodies did not inhibit merozoite invasion or intraerythrocytic development but significantly reduced parasitemia in the presence of human monocytes. The ADCI demonstrated by anti-MSP3N antibodies was comparable to that exhibited by anti-MSP3F antibodies (both generated in rabbit). These results suggest that the N-terminal fragment of MSP3 can be considered a vaccine candidate that can form part of a multigenic vaccine against malaria.

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Age-Dependent IgG Subclass Responses to Plasmodium falciparum EBA-175 Are Differentially Associated with Incidence of Malaria in Mozambican Children

Clinical and Vaccine Immunology ◽

10.1128/cvi.05523-11 ◽

2011 ◽

Vol 19 (2) ◽

pp. 157-166 ◽

Cited By ~ 25

Author(s):

Carlota Dobaño ◽

Diana Quelhas ◽

Llorenç Quintó ◽

Laura Puyol ◽

Elisa Serra-Casas ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Malaria Incidence ◽

Controlled Trial ◽

Intermittent Preventive Treatment ◽

Antibody Test ◽

Merozoite Surface Protein ◽

Blood Stage ◽

Enzyme Linked Immunosorbent Assay ◽

Igg Subclass ◽

Content Type

ABSTRACTPlasmodium falciparumblood-stage antigens such as merozoite surface protein 1 (MSP-1), apical membrane antigen 1 (AMA-1), and the 175-kDa erythrocyte binding antigen (EBA-175) are considered important targets of naturally acquired immunity to malaria. However, it is not clear whether antibodies to these antigens are effectors in protection against clinical disease or mere markers of exposure. In the context of a randomized, placebo-controlled trial of intermittent preventive treatment in infants conducted between 2002 and 2004, antibody responses toPlasmodium falciparumblood-stage antigens in a cohort of 302 Mozambican children were evaluated by immunofluorescence antibody test and enzyme-linked immunosorbent assay at 5, 9, 12, and 24 months of age. We found that IgG subclass responses to EBA-175 were differentially associated with the incidence of malaria in the follow-up period. A double amount of cytophilic IgG1 or IgG3 was associated with a significant decrease in the incidence of malaria (incidence rate ratio [IRR] = 0.49, 95% confidence interval [CI] = 0.25 to 0.97, andP= 0.026 and IRR = 0.44, CI = 0.19 to 0.98, andP= 0.037, respectively), while a double amount of noncytophilic IgG4 was significantly correlated with an increased incidence of malaria (IRR = 3.07, CI = 1.08 to 8.78,P= 0.020). No significant associations between antibodies to the 19-kDa fragment of MSP-1 (MSP-119) or AMA-1 and incidence of malaria were found. Age, previous episodes of malaria, present infection, and neighborhood of residence were the main factors influencing levels of antibodies to all merozoite antigens. Deeper understanding of the acquisition of antibodies against vaccine target antigens in early infancy is crucial for the rational development and deployment of malaria control tools in this vulnerable population.

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