Babesia bovis Merozoite Surface Antigen 1 and Rhoptry-Associated Protein 1 Are Expressed in Sporozoites, and Specific Antibodies Inhibit Sporozoite Attachment to Erythrocytes

ABSTRACT We examined Babesia bovis sporozoites for the expression of two molecules, merozoite surface antigen 1 (MSA-1) and rhoptry-associated protein 1 (RAP-1), that are postulated to be involved in the invasion of host erythrocytes. Both MSA-1 and RAP-1 were transcribed and expressed in infectious sporozoites. Importantly, monospecific MSA-1 and RAP-1 antisera each inhibited sporozoite invasion of erythrocytes in vitro. This is the first identification of antigens expressed in Babesia sp. sporozoites and establishes that, at least in part, sporozoites and merozoites share common targets of antibody mediated inhibition of erythrocyte invasion.

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Babesia bovis Merozoite Surface Antigen 2 Proteins Are Expressed on the Merozoite and Sporozoite Surface, and Specific Antibodies Inhibit Attachment and Invasion of Erythrocytes

Infection and Immunity ◽

10.1128/iai.70.11.6448-6455.2002 ◽

2002 ◽

Vol 70 (11) ◽

pp. 6448-6455 ◽

Cited By ~ 55

Author(s):

Juan Mosqueda ◽

Terry F. McElwain ◽

Guy H. Palmer

Keyword(s):

Surface Antigen ◽

Significant Inhibition ◽

Babesia Bovis ◽

Merozoite Invasion ◽

Specific Antibodies ◽

Surface Molecules ◽

Erythrocyte Invasion ◽

Merozoite Surface Antigen ◽

Initial Binding ◽

Bovine Erythrocytes

ABSTRACT The Babesia bovis merozoite surface antigen 2 (MSA-2) locus encodes four proteins, MSA-2a1, -2a2, -2b, and -2c. With the use of specific antibodies, each MSA-2 protein was shown to be expressed on the surface of live extracellular merozoites and coexpression on single merozoites was confirmed. Individual antisera against MSA-2a, MSA-2b, and MSA-2c significantly inhibited merozoite invasion of bovine erythrocytes. As tick-derived sporozoites also directly invade erythrocytes, expression of each MSA-2 protein on the sporozoite surface was examined and verified. Finally, statistically significant inhibition of sporozoite binding to the erythrocytes was demonstrated by using antisera specific for MSA-2a, MSA-2b, and MSA-2c. These results indicate an important role for MSA-2 proteins in the initial binding and invasion of host erythrocytes and support the hypothesis that sporozoites and merozoites use common surface molecules in erythrocyte invasion.

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The Babesia bovis Merozoite Surface Antigen 1 Hypervariable Region Induces Surface-Reactive Antibodies That Block Merozoite Invasion

Infection and Immunity ◽

10.1128/iai.00032-06 ◽

2006 ◽

Vol 74 (6) ◽

pp. 3663-3667 ◽

Cited By ~ 17

Author(s):

Tanya LeRoith ◽

Shawn J. Berens ◽

Kelly A. Brayton ◽

Stephen A. Hines ◽

Wendy C. Brown ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Surface Antigen ◽

Hypervariable Region ◽

Babesia Bovis ◽

Related Family ◽

Erythrocyte Invasion ◽

Merozoite Surface Antigen ◽

Carboxy Terminal ◽

Blocking Antibodies

ABSTRACT A hypervariable region (HVR) previously identified in the carboxy-terminal one-third of the Babesia bovis variable merozoite surface antigen family was more extensively analyzed in merozoite surface antigen 1 (MSA-1) from 16 strains and isolates. The MSA-1 HVR is proline rich and contains three semiconserved motifs nearly identical to those described for the related family member MSA-2. Two MSA-1-specific monoclonal antibodies previously shown to be reactive with the merozoite surface bound to a recombinant construct encoding the HVR, indicating that the HVR is surface exposed and accessible to antibody binding. Importantly, these surface-reactive, HVR-specific monoclonal antibodies were capable of inhibiting merozoite infectivity of the host erythrocyte in vivo. The results indicate that the MSA-1 HVR is involved in erythrocyte invasion and suggest that selection of MSA-1 variants may be driven by invasion-blocking antibodies.

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Merozoite Surface Antigen 2 Proteins of Babesia bovis Vaccine Breakthrough Isolates Contain a Unique Hypervariable Region Composed of Degenerate Repeats

Infection and Immunity ◽

10.1128/iai.73.11.7180-7189.2005 ◽

2005 ◽

Vol 73 (11) ◽

pp. 7180-7189 ◽

Cited By ~ 48

Author(s):

Shawn J. Berens ◽

Kelly A. Brayton ◽

John B. Molloy ◽

Russell E. Bock ◽

Ala E. Lew ◽

...

Keyword(s):

Surface Antigen ◽

Protective Immunity ◽

Sequence Variation ◽

Immune Escape ◽

Hypervariable Region ◽

Babesia Bovis ◽

Erythrocyte Invasion ◽

Merozoite Surface Antigen ◽

Nucleotide Repeats ◽

Degenerate Nucleotide

ABSTRACT The merozoite surface antigen 2 (MSA-2) proteins of Babesia bovis are members of the variable merozoite surface antigen (VMSA) family that have been implicated in erythrocyte invasion and are important targets for antibody-mediated blocking of invasion. Extensive sequence variation in another VMSA member, MSA-1, has been shown in all vaccine breakthrough isolates. To test the hypothesis that the msa-2 genes of vaccine breakthrough isolates would also encode a diverse set of proteins, the complete msa-2 locus was characterized from 12 Australian B. bovis strains and isolates, including two vaccine strains and eight vaccine breakthrough isolates, and compared to the loci in previously and newly characterized American strains. In contrast to American strains, the msa-2 loci of all Australian strains and isolates examined contain, in addition to msa-2c, only a solitary gene (designated msa-2a/b) closely related to American strain msa-2a and msa-2b. Nevertheless, the proteins encoded by these genes are quite diverse both between and within geographic regions and harbor evidence of genetic exchange among other VMSA family members, including msa-1. Moreover, all but one of the Australian breakthrough isolate MSA-2a/b proteins is markedly different from the vaccine strain from which immune escape occurred, consistent with their role in strain-specific protective immunity. The densest distribution of polymorphisms occurs in a hypervariable region (HVR) within the carboxy third of the molecule that is highly proline rich. Variation in length and content of the HVR is primarily attributable to differences in the order and number of degenerate nucleotide repeats encoding three motifs of unknown function.

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Characterization of Allelic Variation in theBabesia bovis Merozoite Surface Antigen 1 (MSA-1) Locus and Identification of a Cross-Reactive Inhibition-Sensitive MSA-1 Epitope

Infection and Immunity ◽

10.1128/iai.68.12.6865-6870.2000 ◽

2000 ◽

Vol 68 (12) ◽

pp. 6865-6870 ◽

Cited By ~ 66

Author(s):

Carlos E. Suarez ◽

Monica Florin-Christensen ◽

Stephen A. Hines ◽

Guy H. Palmer ◽

Wendy C. Brown ◽

...

Keyword(s):

Surface Antigen ◽

Allelic Variation ◽

Sequence Divergence ◽

Amino Acid Sequences ◽

Babesia Bovis ◽

Erythrocyte Invasion ◽

Merozoite Surface Antigen ◽

Inhibitory Antibodies ◽

Limited Sequence

ABSTRACT The Babesia bovis merozoite surface antigen 1 (MSA-1), a member of the variable merozoite surface antigen (VMSA) family, is an immunodominant glycoprotein which elicits antibodies that inhibit erythrocyte invasion. While antigenic polymorphism is a general feature of vmsa genes, the molecular basis and extent ofmsa-1 sequence polymorphism have not been well characterized. In this study we defined the msa-1 locus in the biologically cloned Mexico Mo7 strain of B. bovis and identified the sequence differences between MSA-1 antigenically dissimilar strains. We then determined whether sequences conserved between distinct msa-1 alleles would induce cross-reactive CD4+ T lymphocytes or inhibitory antibodies. Themsa-1 locus in Mo7 contains a single msa-1 gene flanked by transcribed genes with no sequence homology to members of the VMSA gene family. Argentina B. bovis strains R1A and S2P have msa-1 genes with amino acid sequences that are 98.8% identical to each other, and antibodies against S2P MSA-1 cross-react with native R1A MSA-1. In contrast, identity between the Argentina and Mexico Mo7 msa-1 alleles is only 52%, with no continuous stretch of identity longer than 16 amino acids. Despite limited sequence conservation, antibodies against R1A MSA-1 were able to inhibit invasion of erythrocytes by Mo7 merozoites. The results indicate that inhibition-sensitive epitopes are conserved despite significant sequence divergence between Mexico and Argentina strain alleles and support a conserved functional role for polymorphic MSA-1 in erythrocyte invasion.

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Vaccination-induced variation in the 140 kD merozoite surface antigen of Plasmodium knowlesi malaria.

Journal of Experimental Medicine ◽

10.1084/jem.165.2.359 ◽

1987 ◽

Vol 165 (2) ◽

pp. 359-367 ◽

Cited By ~ 31

Author(s):

F W Klotz ◽

D E Hudson ◽

H G Coon ◽

L H Miller

Keyword(s):

Monoclonal Antibodies ◽

Malaria Infection ◽

Rhesus Monkeys ◽

Plasmodium Knowlesi ◽

Rabbit Antiserum ◽

Antigenic Determinants ◽

Partial Protection ◽

Erythrocyte Invasion ◽

Merozoite Surface Antigen

Immunity to 143/140 kD schizont antigens of a monkey malaria, Plasmodium knowlesi, provides partial protection to lethal malaria infection in rhesus monkeys challenged with uncloned parasites. To determine the capacity of a cloned parasite to generate variants of the 143/140 kD antigens, immunized monkeys were challenged with a clone of P. knowlesi. Parasites recovered 8 d after inoculation with a cloned parasite retained the 143/140 kD antigens. Parasites recovered 30 d after challenge had undergone changes in the 143/140 kD antigens. Antibodies that block erythrocyte invasion in vitro of the inoculum parasites did not inhibit invasion of erythrocytes by two isolates recovered from the immunized monkeys. An isolate from one monkey recovered on day 30 contained clones expressing new 76/72 kD antigens reactive with rabbit antiserum against the 143/140 kD proteins, and other clones expressing no antigens crossreactive with antisera against the 143/140 kD proteins. An isolate from another monkey obtained 59 d after challenge expressed new antigens of 160/155, 115/113, and 87/85 kD. Using monoclonal antibodies, we found that epitopes were lost from the variant proteins, but we were unable to determine whether new epitopes had appeared. We conclude that clones of P. knowlesi can rapidly vary antigenic determinants on the 143/140 kD proteins in animals immunized with these antigens.

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Antibodies induced by Plasmodium falciparum merozoite surface antigen-2-designed pseudopeptides possess neutralizing properties of the in vitro malarial infection

Peptides ◽

10.1016/j.peptides.2007.07.029 ◽

2007 ◽

Vol 28 (10) ◽

pp. 1954-1965 ◽

Cited By ~ 4

Author(s):

José Manuel Lozano ◽

Francy J. Montoya-Fajardo ◽

Johan Hoebeke ◽

Gladys H. Cifuentes ◽

Martha Forero ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Surface Antigen ◽

Malarial Infection ◽

Merozoite Surface Antigen ◽

Falciparum Merozoite

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Diversity of Babesia bovis merozoite surface antigen genes in the Philippines

Parasitology International ◽

10.1016/j.parint.2013.09.003 ◽

2014 ◽

Vol 63 (1) ◽

pp. 57-63 ◽

Cited By ~ 12

Author(s):

Muncharee Tattiyapong ◽

Thillaiampalam Sivakumar ◽

Adrian Patalinghug Ybanez ◽

Rochelle Haidee Daclan Ybanez ◽

Zandro Obligado Perez ◽

...

Keyword(s):

Surface Antigen ◽

The Philippines ◽

Babesia Bovis ◽

Merozoite Surface Antigen

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Persistence of Antibodies against Epitopes Encoded by a Single Gene Copy of the Babesia bovis Merozoite Surface Antigen 1 (MSA-1)

Journal of Parasitology ◽

10.2307/3284511 ◽

1998 ◽

Vol 84 (2) ◽

pp. 449 ◽

Cited By ~ 3

Author(s):

Terry F. McElwain ◽

Stephen A. Hines ◽

Guy H. Palmer

Keyword(s):

Surface Antigen ◽

Single Gene ◽

Babesia Bovis ◽

Gene Copy ◽

Merozoite Surface Antigen

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A 32 kDa surface antigen of Theileria parva: characterization and immunization studies

Parasitology ◽

10.1017/s0031182099005934 ◽

2000 ◽

Vol 120 (6) ◽

pp. 553-564 ◽

Cited By ~ 15

Author(s):

R. A. SKILTON ◽

A. J. MUSOKE ◽

C. W. WELLS ◽

Y. YAGI ◽

V. NENE ◽

...

Keyword(s):

Monoclonal Antibody ◽

Cell Surface ◽

Immunoelectron Microscopy ◽

Surface Antigen ◽

Immunoblot Analysis ◽

Theileria Parva ◽

Specific Antibodies ◽

Major Antigen

Previous studies using monoclonal antibody (mAb) 4C9 specific for a 32 kDa antigen (p32) of Theileria parva demonstrated expression of the antigen on the surface of the sporozoite, making it a potential antigen for sporozoite neutralization. A full-length cDNA encoding the major merozoite/piroplasm surface antigen (mMPSA) of T. parva was cloned and expressed in bacteria. The expressed product reacted strongly with mAb 4C9, demonstrating identity between the p32 and mMPSA of T. parva. Using immunoblot analysis and immunoelectron microscopy with mAb 4C9 it was shown that the mMPSA is a major antigen of the merozoite and piroplasm at the cell surface, while lower levels of antigen are expressed in the sporozoite and schizont stages. Upregulation of the mMPSA occurs at merogony and can be induced by culturing schizont-infected lymphocytes at 42 °C. Recombinant mMPSA of T. parva induced high titres of specific antibodies in cattle but failed to confer protection against a T. parva sporozoite stabilate challenge. The pre-challenge sera also failed to neutralize infectivity of sporozoites in an in vitro assay. Possible reasons for the lack of parasite neutralization in vivo and in vitro are discussed.

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