scholarly journals Linkage between Anaplasma marginale Outer Membrane Proteins Enhances Immunogenicity but Is Not Required for Protection from Challenge

2013 ◽  
Vol 20 (5) ◽  
pp. 651-656 ◽  
Author(s):  
Susan M. Noh ◽  
Joshua E. Turse ◽  
Wendy C. Brown ◽  
Junzo Norimine ◽  
Guy H. Palmer
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Protective Immunity ◽  
Bacterial Infections ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Anaplasma Marginale ◽  
Anamnestic Response ◽  
Covalent Bonds ◽  
Content Type

ABSTRACTThe prevention of bacterial infections via immunization presents particular challenges. While outer membrane extracts are often protective, they are difficult and expensive to isolate and standardize and thus are often impractical for development and implementation in vaccination programs. In contrast, individual proteins, which are easily adapted for use in subunit vaccines, tend to be poorly protective. Consequently, identification of the specific characteristics of outer membrane-based immunogens, in terms of the antigen contents and contexts that are required for protective immunity, represents a major gap in the knowledge needed for bacterial vaccine development. Using as a modelAnaplasma marginale, a persistent tick-borne bacterial pathogen of cattle, we tested two sets of immunogens to determine whether membrane context affected immunogenicity and the capacity to induce protection. The first immunogen was composed of a complex of outer membrane proteins linked by covalent bonds and known to be protective. The second immunogen was derived directly from the first one, but the proteins were individualized rather than linked. The antibody response induced by the linked immunogen was much greater than that induced by the unlinked immunogen. However, both immunogens induced protective immunity and an anamnestic response. These findings suggest that individual proteins or combinations of proteins can be successfully tested for the ability to induce protective immunity with less regard for overall membrane context. Once protective antigens are identified, immunogenicity could be enhanced by cross-linking to allow a reduced immunogen dose or fewer booster vaccinations.

scholarly journals Genetic Similarity of Gonococcal Homologs to Meningococcal Outer Membrane Proteins of Serogroup B Vaccine

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Henju Marjuki ◽  
Nadav Topaz ◽  
Sandeep J. Joseph ◽  
Kim M. Gernert ◽  
Ellen N. Kersh ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Vaccine Development ◽  
Membrane Vesicle ◽  
Outer Membrane Proteins ◽  
The United States ◽  
Cross Protection ◽  
Outer Membrane Vesicle ◽  
Content Type ◽  
Sequence Identity

ABSTRACT The human pathogens Neisseria gonorrhoeae and Neisseria meningitidis share high genome identity. Retrospective analysis of surveillance data from New Zealand indicates the potential cross-protective effect of outer membrane vesicle (OMV) meningococcal serogroup B vaccine (MeNZB) against N. gonorrhoeae. A licensed OMV-based MenB vaccine, MenB-4C, consists of a recombinant FHbp, NhbA, NadA, and the MeNZB OMV. Previous work has identified several abundantly expressed outer membrane proteins (OMPs) as major components of the MenB-4C OMV with high sequence similarity between N. gonorrhoeae and N. meningitidis, suggesting a mechanism for cross-protection. To build off these findings, we performed comparative genomic analysis on 970 recent N. gonorrhoeae isolates collected through a U.S surveillance system against N. meningitidis serogroup B (NmB) reference sequences. We identified 1,525 proteins that were common to both Neisseria species, of which 57 proteins were predicted to be OMPs using in silico methods. Among the MenB-4C antigens, NhbA showed moderate sequence identity (73%) to the respective gonococcal homolog, was highly conserved within N. gonorrhoeae, and was predicted to be surface expressed. In contrast, the gonococcal FHbp was predicted not to be surface expressed, while NadA was absent in all N. gonorrhoeae isolates. Our work confirmed recent observations (E. A. Semchenko, A. Tan, R. Borrow, and K. L. Seib, Clin Infect Dis, 2018, https://doi.org/10.1093/cid/ciy1061) and describes homologous OMPs from a large panel of epidemiologically relevant N. gonorrhoeae strains in the United States against NmB reference strains. Based on our results, we report a set of OMPs that may contribute to the previously observed cross-protection and provide potential antigen targets to guide the next steps in gonorrhea vaccine development. IMPORTANCE Gonorrhea, a sexually transmitted disease, causes substantial global morbidity and economic burden. New prevention and control measures for this disease are urgently needed, as strains resistant to almost all classes of antibiotics available for treatment have emerged. Previous reports demonstrate that cross-protection from gonococcal infections may be conferred by meningococcal serogroup B (MenB) outer membrane vesicle (OMV)-based vaccines. Among 1,525 common proteins shared across the genomes of both N. gonorrhoeae and N. meningitidis, 57 proteins were predicted to be surface expressed (outer membrane proteins [OMPs]) and thus preferred targets for vaccine development. The majority of these OMPs showed high sequence identity between the 2 bacterial species. Our results provide valuable insight into the meningococcal antigens present in the current OMV-containing MenB-4C vaccine that may contribute to cross-protection against gonorrhea and may inform next steps in gonorrhea vaccine development.

scholarly journals Identification of Novel Antigenic Proteins in a Complex Anaplasma marginale Outer Membrane Immunogen by Mass Spectrometry and Genomic Mapping

2005 ◽  
Vol 73 (12) ◽  
pp. 8109-8118 ◽  
Author(s):  
Job E. Lopez ◽  
William F. Siems ◽  
Guy H. Palmer ◽  
Kelly A. Brayton ◽  
Travis C. McGuire ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Serum Antibody ◽  
Elongation Factor ◽  
Anaplasma Marginale ◽  
Antigenic Proteins ◽  
Associated Proteins

ABSTRACT Immunization with purified Anaplasma marginale outer membranes induces complete protection against infection that is associated with CD4+ T-lymphocyte-mediated gamma interferon secretion and immunoglobulin G2 (IgG2) antibody titers. However, knowledge of the composition of the outer membrane immunogen is limited. Recent sequencing and annotation of the A. marginale genome predicts at least 62 outer membrane proteins (OMP), enabling a proteomic and genomic approach for identification of novel OMP by use of IgG serum antibody from outer membrane vaccinates. Outer membrane proteins were separated by two-dimensional electrophoresis, and proteins recognized by total IgG and IgG2 in immune sera of outer membrane-vaccinated cattle were detected by immunoblotting. Immunoreactive protein spots were excised and subjected to liquid chromatography-tandem mass spectrometry. A database search of the A. marginale genome identified 24 antigenic proteins that were predicted to be outer membrane, inner membrane, or membrane-associated proteins. These included the previously characterized surface-exposed outer membrane proteins MSP2, operon associated gene 2 (OpAG2), MSP3, and MSP5 as well as recently identified appendage-associated proteins. Among the 21 newly described antigenic proteins, 14 are annotated in the A. marginale genome and include type IV secretion system proteins, elongation factor Tu, and members of the MSP2 superfamily. The identification of these novel antigenic proteins markedly expands current understanding of the composition of the protective immunogen and provides new candidates for vaccine development.

scholarly journals Protective Immunity and Reduced Renal Colonization Induced by Vaccines Containing Recombinant Leptospira interrogans Outer Membrane Proteins and Flagellin Adjuvant

2015 ◽  
Vol 22 (8) ◽  
pp. 965-973 ◽  
Author(s):  
D. Monaris ◽  
M. E. Sbrogio-Almeida ◽  
C. C. Dib ◽  
T. A. Canhamero ◽  
G. O. Souza ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Immune Responses ◽  
Outer Membrane ◽  
Protective Immunity ◽  
Outer Membrane Proteins ◽  
Protein A ◽  
Leptospira Interrogans ◽  
Renal Tubules ◽  
Subunit Vaccines ◽  
Content Type

ABSTRACTLeptospirosis is a global zoonotic disease caused by differentLeptospiraspecies, such asLeptospira interrogans, that colonize the renal tubules of wild and domestic animals. Thus far, attempts to develop effective leptospirosis vaccines, both for humans and animals, have failed to induce immune responses capable of conferring protection and simultaneously preventing renal colonization. In this study, we evaluated the protective immunity induced by subunit vaccines containing seven different recombinantLeptospira interrogansouter membrane proteins, including the carboxy-terminal portion of the immunoglobulinlike protein A (LigAC) and six novel antigens, combined with aluminum hydroxide (alum) orSalmonellaflagellin (FliC) as adjuvants. Hamsters vaccinated with the different formulations elicited high antigen-specific antibody titers. Immunization with LigAC, either with alum or flagellin, conferred protective immunity but did not prevent renal colonization. Similarly, animals immunized with LigACor LigACcoadministered with six leptospiral proteins with alum adjuvant conferred protection but did not reduce renal colonization. In contrast, immunizing animals with the pool of seven antigens in combination with flagellin conferred protection and significantly reduced renal colonization by the pathogen. The present study emphasizes the relevance of antigen composition and added adjuvant in the efficacy of antileptospirosis subunit vaccines and shows the complex relationship between immune responses and renal colonization by the pathogen.

scholarly journals Immunoproteomic Analysis To Identify Shiga Toxin-Producing Escherichia coli Outer Membrane Proteins Expressed during Human Infection

2014 ◽  
Vol 82 (11) ◽  
pp. 4767-4777 ◽  
Author(s):  
David Montero ◽  
Paz Orellana ◽  
Daniela Gutiérrez ◽  
Daniela Araya ◽  
Juan Carlos Salazar ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Shiga Toxin ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Antibiotic Use ◽  
Etiologic Agent ◽  
Human Infection ◽  
Content Type

ABSTRACTShiga-toxin producingEscherichia coli(STEC) is the etiologic agent of acute diarrhea, dysentery, and hemolytic-uremic syndrome (HUS). There is no approved vaccine for STEC infection in humans, and antibiotic use is contraindicated, as it promotes Shiga toxin production. In order to identify STEC-associated antigens and immunogenic proteins, outer membrane proteins (OMPs) were extracted from STEC O26:H11, O103, O113:H21, and O157:H7 strains, and commensalE. colistrain HS was used as a control. SDS-PAGE, two-dimensional-PAGE analysis, Western blot assays using sera from pediatric HUS patients and controls, and matrix-assisted laser desorption ionization–tandem time of flight analyses were used to identify 12 immunogenic OMPs, some of which were not reactive with control sera. Importantly, seven of these proteins have not been previously reported to be immunogenic in STEC strains. Among these seven proteins, OmpT and Cah displayed IgG and IgA reactivity with sera from HUS patients. Genes encoding these two proteins were present in a majority of STEC strains. Knowledge of the antigens produced during infection of the host and the immune response to those antigens will be important for future vaccine development.

scholarly journals A Disulfide Oxidoreductase (CHU_1165) Is Essential for Cellulose Degradation by Affecting Outer Membrane Proteins in Cytophaga hutchinsonii

2020 ◽  
Vol 86 (8) ◽  
Author(s):  
Dong Zhao ◽  
Ying Wang ◽  
Sen Wang ◽  
Weican Zhang ◽  
Qingsheng Qi ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Disulfide Bond ◽  
Cellulose Degradation ◽  
Outer Membrane Proteins ◽  
Hypothetical Protein ◽  
Pleiotropic Effect ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Disulfide Oxidoreductase

ABSTRACT Cytophaga hutchinsonii cells can bind to the surface of insoluble cellulose and degrade it by utilizing a novel cell contact-dependent mechanism, in which the outer membrane proteins may play important roles. In this study, the deletion of a gene locus, chu_1165, which encodes a hypothetical protein with 32% identity with TlpB, a disulfide oxidoreductase in Flavobacterium psychrophilum, caused a complete cellulolytic defect in C. hutchinsonii. Further study showed that cells of the Δ1165 strain could not bind to cellulose, and the levels of many outer membrane proteins that can bind to cellulose were significantly decreased. The N-terminal region of CHU_1165 is anchored to the cytoplasmic membrane with five predicted transmembrane helices, and the C-terminal region is predicted to stretch to the periplasm and has a similar thioredoxin (Trx) fold containing a Cys-X-X-Cys motif that is conserved in disulfide oxidoreductases. Recombinant CHU_1165His containing the Cys-X-X-Cys motif was able to reduce the disulfide bonds of insulin in vitro. Site-directed mutation showed that the cysteines in the Cys-X-X-Cys motif and at residues 106 and 108 were indispensable for the function of CHU_1165. Western blotting showed that CHU_1165 was in an oxidized state in vivo, suggesting that it may act as an oxidase to catalyze disulfide bond formation. However, many of the decreased outer membrane proteins that were essential for cellulose degradation contained no or one cysteine, and mutation of the cysteine in these proteins did not affect cellulose degradation, indicating that CHU_1165 may have an indirect or pleiotropic effect on the function of these outer membrane proteins. IMPORTANCE Cytophaga hutchinsonii can rapidly digest cellulose in a contact-dependent manner, in which the outer membrane proteins may play important roles. In this study, a hypothetical protein, CHU_1165, characterized as a disulfide oxidoreductase, is essential for cellulose degradation by affecting the cellulose binding ability of many outer membrane proteins in C. hutchinsonii. Disulfide oxidoreductases are involved in disulfide bond formation. However, our studies show that many of the decreased outer membrane proteins that were essential for cellulose degradation contained no or one cysteine, and mutation of cysteine did not affect their function, indicating that CHU_1165 did not facilitate the formation of a disulfide bond in these proteins. It may have an indirect or pleiotropic effect on the function of these outer membrane proteins. Our study provides an orientation for exploring the proteins that assist in the appropriate conformation of many outer membrane proteins essential for cellulose degradation, which is important for exploring the novel mechanism of cellulose degradation in C. hutchinsonii.

scholarly journals Catecholamine-Modulated Novel Surface-Exposed Adhesin LIC20035 ofLeptospiraspp. Binds Host Extracellular Matrix Components and Is Recognized by the Host during Infection

2017 ◽  
Vol 84 (6) ◽  
Author(s):  
Karukriti Kaushik Ghosh ◽  
Aman Prakash ◽  
Vinayagamurthy Balamurugan ◽  
Manish Kumar
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Membrane Surface ◽  
Outer Membrane Proteins ◽  
Extracellular Matrices ◽  
Content Type ◽  
Extracellular Matrix Components ◽  
Gene Transcripts ◽  
Host Tissues

ABSTRACTIn this study, the effect of the host stress hormone catecholamine onLeptospiragene transcripts encoding outer membrane proteins was investigated. There was no impact of catecholamine supplementation on thein vitrogrowth pattern ofLeptospira interrogans; however, 7 genes out of 41 were differentially transcribed, and the effect was reversed to the basal level in the presence of the antagonist propranolol. Comprehensive analysis of one of the differentially regulated proteins, LIC20035 (in serovar Copenhageni)/LB047 (in serovar Lai) (due to catecholamine supplementation), revealed immunogenicity and ability to adhere to host extracellular matrices. Protease accessibility assay and phase partition of integral membrane proteins ofLeptospirashowed LIC20035/LB047 to be an outer membrane surface-exposed protein. The recombinant LIC20035 protein can be serologically detected using human/bovine sera positive for leptospirosis. Moreover, the recombinant LIC20035 can bind to diverse host extracellular matrices, with a higher affinity toward collagen and chondroitin sulfate.IMPORTANCELeptospirosis is a neglected tropical disease of global importance. This study aimed to identify outer membrane proteins of pathogenicLeptospiraresponding to host chemical signals like catecholamines, with the potential to serve as virulence factors, new serodiagnostic antigens, and vaccine candidates. This study mimicked the plausible means by whichLeptospiraduring infection and hormonal stress intercepts host catecholamines to disseminate in host tissues.

scholarly journals Putative β-Barrel Outer Membrane Proteins of the Bovine Digital Dermatitis-Associated Treponemes: Identification, Functional Characterization, and Immunogenicity

2020 ◽  
Vol 88 (5) ◽  
Author(s):  
G. J. Staton ◽  
S. D. Carter ◽  
S. Ainsworth ◽  
J. Mullin ◽  
R. F. Smith ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Functional Characterization ◽  
Signal Peptidase ◽  
Effective Vaccine ◽  
Digital Dermatitis ◽  
Diverse Range ◽  
Content Type ◽  
Signal Peptidase I

ABSTRACT Bovine digital dermatitis (BDD), an infectious disease of the bovine foot with a predominant treponemal etiology, is a leading cause of lameness in dairy and beef herds worldwide. BDD is poorly responsive to antimicrobial therapy and exhibits a relapsing clinical course; an effective vaccine is therefore urgently sought. Using a reverse vaccinology approach, the present study surveyed the genomes of the three BDD-associated Treponema phylogroups for putative β-barrel outer membrane proteins and considered their potential as vaccine candidates. Selection criteria included the presence of a signal peptidase I cleavage site, a predicted β-barrel fold, and cross-phylogroup homology. Four candidate genes were overexpressed in Escherichia coli BL21(DE3), refolded, and purified. Consistent with their classification as β-barrel OMPs, circular-dichroism spectroscopy revealed the adoption of a predominantly β-sheet secondary structure. These recombinant proteins, when screened for their ability to adhere to immobilized extracellular matrix (ECM) components, exhibited a diverse range of ligand specificities. All four proteins specifically and dose dependently adhered to bovine fibrinogen. One recombinant protein was identified as a candidate diagnostic antigen (disease specificity, 75%). Finally, when adjuvanted with aluminum hydroxide and administered to BDD-naive calves using a prime-boost vaccination protocol, these proteins were immunogenic, eliciting specific IgG antibodies. In summary, we present the description of four putative treponemal β-barrel OMPs that exhibit the characteristics of multispecific adhesins. The observed interactions with fibrinogen may be critical to host colonization and it is hypothesized that vaccination-induced antibody blockade of these interactions will impede treponemal virulence and thus be of therapeutic value.

scholarly journals Differential Expression and Sequence Conservation of the Anaplasma marginale msp2 Gene Superfamily Outer Membrane Proteins

2006 ◽  
Vol 74 (6) ◽  
pp. 3471-3479 ◽  
Author(s):  
Susan M. Noh ◽  
Kelly A. Brayton ◽  
Donald P. Knowles ◽  
Joseph T. Agnes ◽  
Michael J. Dark ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Differential Expression ◽  
Outer Membrane Proteins ◽  
Anaplasma Marginale ◽  
Surface Proteins ◽  
Transcriptional Analysis ◽  
Mammalian Host ◽  
Anaplasma Ovis ◽  
Sequence Comparisons

ABSTRACT Bacterial pathogens in the genera Anaplasma and Ehrlichia encode a protein superfamily, pfam01617, which includes the predominant outer membrane proteins (OMPs) of each species, major surface protein 2 (MSP2) and MSP3 of Anaplasma marginale and Anaplasma ovis, Anaplasma phagocytophilum MSP2 (p44), Ehrlichia chaffeensis p28-OMP, Ehrlichia canis p30, and Ehrlichia ruminantium MAP1, and has been shown to be involved in both antigenic variation within the mammalian host and differential expression between the mammalian and arthropod hosts. Recently, complete sequencing of the A. marginale genome has identified an expanded set of genes, designated omp1-14, encoding new members of this superfamily. Transcriptional analysis indicated that, with the exception of the three smallest open reading frames, omp2, omp3, and omp6, these superfamily genes are transcribed in A. marginale-infected erythrocytes, tick midgut and salivary glands, and the IDE8 tick cell line. OMPs 1, 4, 7 to 9, and 11 were confirmed to be expressed as proteins by A. marginale within infected erythrocytes, with expression being either markedly lower (OMPs 1, 4, and 7 to 9) or absent (OMP11) in infected tick cells, which reflected regulation at the transcript level. Although the pfam01617 superfamily includes the antigenically variable MSP2 and MSP3 surface proteins, analysis of the omp1-14 sequences throughout a cycle of acute and persistent infection in the mammalian host and tick transmission reveals a high degree of conservation, an observation supported by sequence comparisons between the St. Maries strain and Florida strain genomes.

scholarly journals Composition of the Surface Proteome of Anaplasma marginale and Its Role in Protective Immunity Induced by Outer Membrane Immunization

2008 ◽  
Vol 76 (5) ◽  
pp. 2219-2226 ◽  
Author(s):  
Susan M. Noh ◽  
Kelly A. Brayton ◽  
Wendy C. Brown ◽  
Junzo Norimine ◽  
Gerhard R. Munske ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protective Immunity ◽  
Vaccine Development ◽  
Bacterial Pathogen ◽  
Protein Composition ◽  
Anaplasma Marginale ◽  
Surface Proteins ◽  
Mammalian Host ◽  
Surface Complexes ◽  
Surface Proteome

ABSTRACT Surface proteins of tick-borne, intracellular bacterial pathogens mediate functions essential for invasion and colonization. Consequently, the surface proteome of these organisms is specifically relevant from two biological perspectives, induction of protective immunity in the mammalian host and understanding the transition from the mammalian host to the tick vector. In this study, the surface proteome of Anaplasma marginale, a tick-transmitted bacterial pathogen, was targeted by using surface-specific cross-linking to form intermolecular bonds between adjacent proteins. Liquid chromatography and tandem mass spectroscopy were then employed to characterize the specific protein composition of the resulting complexes. The surface complexes of A. marginale isolated from erythrocytes of the mammalian host were composed of multiple membrane proteins, most of which belong to a protein family, pfam01617, which is conserved among bacteria in the genus Anaplasma and the closely related genus Ehrlichia. In contrast, the surface proteome of A. marginale isolated from tick cells was much less complex and contained a novel protein, AM778, not identified within the surface proteome of organisms from the mammalian host. Immunization using the cross-linked surface complex induced protection against high-level bacteremia and anemia upon A. marginale challenge of cattle and effectively recapitulated the protection induced by immunization with whole outer membranes. These results indicate that a surface protein subset of the outer membrane is capable of inducing protective immunity and serves to direct vaccine development. Furthermore, the data support that remodeling of the surface proteome accompanies the transition between mammalian and arthropod hosts and identify novel targets for blocking transmission.

scholarly journals Immunization with Ehrlichia P28 Outer Membrane Proteins Confers Protection in a Mouse Model of Ehrlichiosis

2011 ◽  
Vol 18 (12) ◽  
pp. 2018-2025 ◽  
Author(s):  
Patricia A. Crocquet-Valdes ◽  
Nagaraja R. Thirumalapura ◽  
Nahed Ismail ◽  
Xuejie Yu ◽  
Tais B. Saito ◽  
...  
Keyword(s):  
T Cells ◽  
Membrane Proteins ◽  
Immune Responses ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
The United States ◽  
Mononuclear Phagocytes ◽  
Specific Cell ◽  
Content Type ◽  
Ifn Γ

ABSTRACTThe obligately intracellular bacteriumEhrlichia chaffeensisthat resides in mononuclear phagocytes is the etiologic agent of human monocytotropic ehrlichiosis (HME). HME is an emerging and often life-threatening, tick-transmitted infectious disease in the United States. Effective primary immune responses againstEhrlichiainfection involve generation ofEhrlichia-specific gamma interferon (IFN-γ)-producing CD4+T cells and cytotoxic CD8+T cells, activation of macrophages by IFN-γ, and production ofEhrlichia-specific antibodies of the Th1 isotype. Currently, there are no vaccines available against HME. We evaluated the ability of 28-kDa outer membrane proteins (P28-OMP-1) of the closely relatedEhrlichia muristo stimulate long-term protective memory T and B cell responses and confer protection in mice. The spleens of mice vaccinated withE. murisP28-9, P28-12, P28-19, or a mixture of these three P28 proteins (P28s) using a DNA prime-protein boost regimen and challenged withE. murishad significantly lower bacterial loads than the spleens of mock-vaccinated mice. Mice immunized with P28-9, P28-12, P28-19, or the mixture inducedEhrlichia-specific CD4+Th1 cells. Interestingly, mice immunized with P28-14, orthologs of which inE. chaffeensisandE. canisare primarily expressed in tick cells, failed to lower the ehrlichial burden in the spleen. Immunization with the recombinant P28-19 protein alone also significantly decreased the bacterial load in the spleen and liver compared to those of the controls. Our study reports, for the first time, the protective roles of theEhrlichiaP28-9 and P28-12 proteins in addition to confirming previous reports of the protective ability of P28-19. Partial protection induced by immunization with P28-9, P28-12, and P28-19 againstEhrlichiawas associated with the generation ofEhrlichia-specific cell-mediated and humoral immune responses.

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