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Blasco JM, Moreno E, Muñoz PM, Conde-Álvarez R, Moriyón I. A review of three decades of use of the cattle brucellosis rough vaccine Brucella abortus RB51: myths and facts. BMC Vet Res 2023; 19:211. [PMID: 37853407 PMCID: PMC10583465 DOI: 10.1186/s12917-023-03773-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 10/04/2023] [Indexed: 10/20/2023] Open
Abstract
Cattle brucellosis is a severe zoonosis of worldwide distribution caused by Brucella abortus and B. melitensis. In some countries with appropriate infrastructure, animal tagging and movement control, eradication was possible through efficient diagnosis and vaccination with B. abortus S19, usually combined with test-and-slaughter (T/S). Although S19 elicits anti-smooth lipopolysaccharide antibodies that may interfere in the differentiation of infected and vaccinated animals (DIVA), this issue is minimized using appropriate S19 vaccination protocols and irrelevant when high-prevalence makes mass vaccination necessary or when eradication requisites are not met. However, S19 has been broadly replaced by vaccine RB51 (a rifampin-resistant rough mutant) as it is widely accepted that is DIVA, safe and as protective as S19. These RB51 properties are critically reviewed here using the evidence accumulated in the last 35 years. Controlled experiments and field evidence shows that RB51 interferes in immunosorbent assays (iELISA, cELISA and others) and in complement fixation, issues accentuated by revaccinating animals previously immunized with RB51 or S19. Moreover, contacts with virulent brucellae elicit anti-smooth lipopolysaccharide antibodies in RB51 vaccinated animals. Thus, accepting that RB51 is truly DIVA results in extended diagnostic confusions and, when combined with T/S, unnecessary over-culling. Studies supporting the safety of RB51 are flawed and, on the contrary, there is solid evidence that RB51 is excreted in milk and abortifacient in pregnant animals, thus being released in abortions and vaginal fluids. These problems are accentuated by the RB51 virulence in humans, lack diagnostic serological tests detecting these infections and RB51 rifampicin resistance. In controlled experiments, protection by RB51 compares unfavorably with S19 and lasts less than four years with no evidence that RB51-revaccination bolsters immunity, and field studies reporting its usefulness are flawed. There is no evidence that RB51 protects cattle against B. melitensis, infection common when raised together with small ruminants. Finally, data acumulated during cattle brucellosis eradication in Spain shows that S19-T/S is far more efficacious than RB51-T/S, which does not differ from T/S alone. We conclude that the assumption that RB51 is DIVA, safe, and efficaceous results from the uncritical repetition of imperfectly examined evidence, and advise against its use.
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Affiliation(s)
- J M Blasco
- Instituto Agroalimentario de Aragón-IA2 (CITA-Universidad de Zaragoza), Zaragoza, España
| | - E Moreno
- Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica
| | - P M Muñoz
- Instituto Agroalimentario de Aragón-IA2 (CITA-Universidad de Zaragoza), Zaragoza, España
- Departamento de Ciencia Animal, Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Zaragoza, España
| | - R Conde-Álvarez
- Instituto de Investigación Sanitaria de Navarra and Departamento de Microbiología y Parasitología, Universidad de Navarra, Pamplona, Spain
| | - I Moriyón
- Instituto de Investigación Sanitaria de Navarra and Departamento de Microbiología y Parasitología, Universidad de Navarra, Pamplona, Spain.
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Touloudi A, McGiven J, Cawthraw S, Valiakos G, Kostoulas P, Duncombe L, Gortázar C, Boadella M, Sofia M, Athanasakopoulou Z, Chatzopoulos DC, Spyrou V, Petrovska L, Billinis C. Development of a Multiplex Bead Assay to Detect Serological Responses to Brucella Species in Domestic Pigs and Wild Boar with the Potential to Overcome Cross-Reactivity with Yersinia enterocolitica O:9. Microorganisms 2022; 10:microorganisms10071362. [PMID: 35889081 PMCID: PMC9324436 DOI: 10.3390/microorganisms10071362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/01/2022] [Accepted: 07/04/2022] [Indexed: 11/16/2022] Open
Abstract
The aim of this study was to develop a multiplex bead assay using a Brucella rLPS antigen, a Brucella suis smooth antigen, and a Yersinia enterocolitica O:9 antigen that not only discriminates Brucella-infected from Brucella-uninfected pigs and wild boar, but also overcomes the cross reactivity with Y. enterocolitica O:9. Sera from 126 domestic pigs were tested: 29 pigs were Brucella infected, 80 were non-infected and 17 were confirmed to be false positive serological reactors (FPSR). Sera from 49 wild boar were tested: 18 were positive and 31 were negative. Using the rLPS antigen, 26/29 Brucella-infected domestic pigs and 15/18 seropositive wild boar were positive, while 75/80 non-Brucella infected domestic pigs, all FPSR, and all seronegative wild boar were negative. Using the smooth B. suis 1330 antigen, all Brucella-infected domestic pigs, 9/17 FPSR and all seropositive wild boar were positive, while all non-infected pigs and 30/31 seronegative wild boar were negative. The ratio of the readouts from the smooth B. suis antigen and Y. enterocolitica O:9 antigen enabled discriminating all Brucella infected individuals from the FPSR domestic pigs. These results demonstrate the potential of this assay for use in the surveillance of brucellosis, overcoming the cross-reactivity with Y. enterocolitica.
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Affiliation(s)
- Antonia Touloudi
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (M.S.); (Z.A.)
| | - John McGiven
- Department of Bacteriology, Animal and Plant Health Agency, OIE/FAO Brucellosis Reference Laboratory, Woodham Lane, Addlestone, Surrey KT15 3NB, UK; (J.M.); (S.C.); (L.D.)
| | - Shaun Cawthraw
- Department of Bacteriology, Animal and Plant Health Agency, OIE/FAO Brucellosis Reference Laboratory, Woodham Lane, Addlestone, Surrey KT15 3NB, UK; (J.M.); (S.C.); (L.D.)
| | - George Valiakos
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (M.S.); (Z.A.)
| | - Polychronis Kostoulas
- Faculty of Public and One Health, University of Thessaly, 431 00 Karditsa, Greece; (P.K.); (D.C.C.)
| | - Lucy Duncombe
- Department of Bacteriology, Animal and Plant Health Agency, OIE/FAO Brucellosis Reference Laboratory, Woodham Lane, Addlestone, Surrey KT15 3NB, UK; (J.M.); (S.C.); (L.D.)
| | - Christian Gortázar
- SaBio, Instituto de Investigación en Recursos Cinegéticos IREC, 13005 Ciudad Real, Spain;
| | | | - Marina Sofia
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (M.S.); (Z.A.)
| | - Zoi Athanasakopoulou
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (M.S.); (Z.A.)
| | - Dimitris C. Chatzopoulos
- Faculty of Public and One Health, University of Thessaly, 431 00 Karditsa, Greece; (P.K.); (D.C.C.)
| | - Vassiliki Spyrou
- Faculty of Animal Science, University of Thessaly, 412 22 Larissa, Greece;
| | - Liljana Petrovska
- Department of Bacteriology, Animal and Plant Health Agency, OIE/FAO Brucellosis Reference Laboratory, Woodham Lane, Addlestone, Surrey KT15 3NB, UK; (J.M.); (S.C.); (L.D.)
- Correspondence: (L.P.); (C.B.)
| | - Charalambos Billinis
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (M.S.); (Z.A.)
- Faculty of Public and One Health, University of Thessaly, 431 00 Karditsa, Greece; (P.K.); (D.C.C.)
- Correspondence: (L.P.); (C.B.)
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Blasco JM, Moreno E, Moriyón I. Efficacy of Brucella abortus S19 and RB51 vaccine strains: A systematic review and meta-analysis. Transbound Emerg Dis 2021; 69:1670-1673. [PMID: 34964556 DOI: 10.1111/tbed.14440] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 10/27/2021] [Indexed: 11/27/2022]
Affiliation(s)
- J M Blasco
- Unidad de Producción y Sanidad Animal, Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA) e Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza, Zaragoza, Spain
| | - E Moreno
- Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica
| | - I Moriyón
- Instituto de Salud Tropical, Instituto de Investigación Sanitaria de Navarra and Departamento de Microbiología y Parasitología, Universidad de Navarra, Spain
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Touloudi A, Valiakos G, Cawthraw S, Kostoulas P, Gortázar C, Boadella M, Giannakopoulos A, Birtsas P, Sofia M, Athanasiou LV, Satra M, Athanasakopoulou Z, Kantere M, Spyrou V, Petrovska L, Billinis C. Development of a Multiplex Bead Assay for Simultaneous Serodiagnosis of Antibodies against Mycobacterium bovis, Brucella suis, and Trichinella spiralis in Wild Boar. Microorganisms 2021; 9:microorganisms9050904. [PMID: 33922494 PMCID: PMC8144985 DOI: 10.3390/microorganisms9050904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 04/16/2021] [Accepted: 04/20/2021] [Indexed: 11/16/2022] Open
Abstract
The aim of this study was to evaluate the diagnostic performance of a multiplex bead assay for the simultaneous detection of antibodies against Mycobacterium bovis, Brucella suis, and Trichinella spiralis. Sera from Eurasian wild boar of known serological status for TB (64 seropositive, 106 seronegative), Brucella (30 seropositive, 39 seronegative), and Trichinella (21 seropositive, 97 seronegative) were used for the development and evaluation of the assay. Magnetic beads coated with recombinant MPB83 antigen (TB), a whole-cell B. suis 1330 antigen, and an E/S T. spiralis antigen were used for the detection of specific antibodies using Bio-Rad Bio-Plex technology. The sensitivities (Se) and specificities (Sp) of the multiplex assay were, for M. bovis, 0.98 and 0.86; for B. suis, 1.00 and 0.97; and for T. spiralis, 0.90 and 0.99 (Se and Sp, respectively). The results show the diagnostic potential of this assay for the simultaneous detection of antibodies against M. bovis, B. suis, and T. spiralis in wild boar.
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Affiliation(s)
- Antonia Touloudi
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - George Valiakos
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - Shaun Cawthraw
- Animal and Plant Health Agency, Addlestone KT15 3NB, UK; (S.C.); (L.P.)
| | - Polychronis Kostoulas
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
- Faculty of Public and Integrated Health, University of Thessaly, 431 00 Karditsa, Greece;
| | - Christian Gortázar
- SaBio, Instituto de Investigación en Recursos Cinegéticos IREC, 13005 Ciudad Real, Spain;
| | | | - Alexios Giannakopoulos
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - Periklis Birtsas
- Faculty of Forestry, Wood Science and Design, 431 00 Karditsa, Greece;
| | - Marina Sofia
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - Labrini V. Athanasiou
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - Maria Satra
- Faculty of Public and Integrated Health, University of Thessaly, 431 00 Karditsa, Greece;
| | - Zoi Athanasakopoulou
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - Maria Kantere
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
| | - Vassiliki Spyrou
- Faculty of Animal Science, University of Thessaly, 412 22 Larissa, Greece;
| | - Liljana Petrovska
- Animal and Plant Health Agency, Addlestone KT15 3NB, UK; (S.C.); (L.P.)
| | - Charalambos Billinis
- Faculty of Veterinary Science, University of Thessaly, 431 00 Karditsa, Greece; (A.T.); (G.V.); (P.K.); (A.G.); (M.S.); (L.V.A.); (Z.A.); (M.K.)
- Faculty of Public and Integrated Health, University of Thessaly, 431 00 Karditsa, Greece;
- Correspondence:
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Olsen SC, Crawford LS, Fuentes A, Kostovic M, Boggiatto PM. Influence of species of negative control sera on results of a brucellosis fluorescence polarization assay. J Vet Diagn Invest 2020; 33:67-72. [PMID: 33213290 DOI: 10.1177/1040638720970888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
We evaluated serologic responses of cattle, bison, elk, and swine representing negative control, early vaccination (4-8 wk), late vaccination (21-28 wk) or booster vaccination, early after-experimental challenge (2-4 wk), and late after-experimental challenge (8-21 wk), in a brucellosis fluorescence polarization assay (FPA; n = 10 sera per species per treatment) using negative control sera from cattle, bison, elk, and swine (n = 5 per species). Sera from cattle shedding Brucella abortus strain RB51 in milk were also evaluated against the 20 negative control sera. The species of negative control sera used in the FPA could increase (p < 0.05) delta millipolarization (mP; delta mP = sample mP - negative control mP) results. In general, the species of negative control sera did not alter the interpretation of FPA results in control, vaccinated, or infected animals. Even after repeated RB51 vaccinations in bison, cattle, or elk, or in cattle shedding RB51 in milk, serologic results from the FPA remained negative. Species differences in FPA results were noted; elk developed robust humoral responses very quickly after infection that resulted in strong positive FPA results. In cattle and bison, humoral responses appeared to develop over a longer period of time, and greater delta mP values were detected at later times after infection. Sensitivity of the FPA for detecting infected animals was greatest for elk in early challenge samples and bison in late challenge samples. Our data suggest that species of origin of negative control sera does not influence interpretation of the FPA in natural hosts of Brucella abortus.
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Affiliation(s)
- Steven C Olsen
- Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA
| | - Lauren S Crawford
- Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA
| | - Antonio Fuentes
- Montana Department of Livestock, Montana Veterinary Diagnostic Laboratory, Bozeman, MT
| | | | - Paola M Boggiatto
- Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA
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Dabral N, Burcham GN, Jain-Gupta N, Sriranganathan N, Vemulapalli R. Overexpression of wbkF gene in Brucella abortus RB51WboA leads to increased O-polysaccharide expression and enhanced vaccine efficacy against B. abortus 2308, B. melitensis 16M, and B. suis 1330 in a murine brucellosis model. PLoS One 2019; 14:e0213587. [PMID: 30856219 PMCID: PMC6411116 DOI: 10.1371/journal.pone.0213587] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 02/25/2019] [Indexed: 12/17/2022] Open
Abstract
Brucella abortus RB51 is an attenuated, stable, spontaneous rough mutant derived in the laboratory from the virulent strain B. abortus 2308. Previous studies discovered that the wboA gene, which encodes a glycosyltransferase required for synthesis of the O-polysaccharide, is disrupted in strain RB51 by an IS711 element. However, complementation of strain RB51 with a functional wboA gene (strain RB51WboA) does not confer it a smooth phenotype but results in low levels of cytoplasmic O-polysaccharide synthesis. In this study, we asked if increasing the potential availability of bactoprenol priming precursors in strain RB51WboA would increase the levels of O-polysaccharide synthesis and enhance the protective efficacy against virulent Brucella challenge. To achieve this, we overexpressed the wbkF gene, which encodes a putative undecaprenyl-glycosyltransferase involved in bactoprenol priming for O-polysaccharide polymerization, in strain RB51WboA to generate strain RB51WboAKF. In comparison to strain RB51WboA, strain RB51WboAKF expressed higher levels of O-polysaccharide, but was still attenuated and remained phenotypically rough. Mice immunized with strain RB51WboAKF developed increased levels of smooth LPS-specific serum antibodies, primarily of IgG2a and IgG3 isotype. Splenocytes from mice vaccinated with strain RB51WboAKF secreted higher levels of antigen-specific IFN-γ and TNF-α and contained more numbers of antigen-specific IFN-γ secreting CD4+ and CD8+ T lymphocytes when compared to those of the RB51 or RB51WboA vaccinated groups. Immunization with strain RB51WboAKF conferred enhanced protection against virulent B. abortus 2308, B. melitensis 16M and B. suis 1330 challenge when compared to the currently used vaccine strains. Our results suggest that strain RB51WboAKF has the potential to be a more efficacious vaccine than its parent strain in natural hosts.
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Affiliation(s)
- Neha Dabral
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, United States of America
- Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Grant N. Burcham
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, United States of America
| | - Neeta Jain-Gupta
- Department of Biomedical Sciences and Pathobiology, VA-MD College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Nammalwar Sriranganathan
- Department of Biomedical Sciences and Pathobiology, VA-MD College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Ramesh Vemulapalli
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, United States of America
- Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Dabral N, Jain-Gupta N, Seleem MN, Sriranganathan N, Vemulapalli R. Overexpression of Brucella putative glycosyltransferase WbkA in B. abortus RB51 leads to production of exopolysaccharide. Front Cell Infect Microbiol 2015; 5:54. [PMID: 26157707 PMCID: PMC4478442 DOI: 10.3389/fcimb.2015.00054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 06/10/2015] [Indexed: 11/13/2022] Open
Abstract
Brucella spp. are Gram-negative, facultative intracellular bacteria that cause brucellosis in mammals. Brucella strains containing the O-polysaccharide in their cell wall structure exhibit a smooth phenotype whereas the strains devoid of the polysaccharide show rough phenotype. B. abortus strain RB51 is a stable rough attenuated mutant which is used as a licensed live vaccine for bovine brucellosis. Previous studies have shown that the wboA gene, which encodes a glycosyltransferase required for the synthesis of O-polysaccharide, is disrupted in B. abortus RB51 by an IS711 element. Although complementation of strain RB51 with a functional wboA gene results in O-polysaccharide synthesis in the cytoplasm, it does not result in smooth phenotype. The aim of this study was to determine if overexpression of Brucella WbkA or WbkE, two additional putative glycosyltransferases essential for O-polysaccharide synthesis, in strain RB51 would result in the O-polysaccharide synthesis and smooth phenotype. Our results demonstrate that overexpression of wbkA or wbkE gene in RB51 does not result in O-polysaccharide expression as shown by Western blotting with specific antibodies. However, wbkA, but not wbkE, overexpression leads to the development of a clumping phenotype and the production of exopolysaccharide(s) containing mannose, galactose, N-acetylglucosamine, and N-acetylgalactosamine. Moreover, we found that the clumping recombinant strain displays increased adhesion to polystyrene plates. The recombinant strain was similar to strain RB51 in its attenuation characteristic and in its ability to induce protective immunity against virulent B. abortus challenge in mice.
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Affiliation(s)
- Neha Dabral
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University West Lafayette, IN, USA
| | - Neeta Jain-Gupta
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech Blacksburg, VA, USA
| | - Mohamed N Seleem
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University West Lafayette, IN, USA
| | - Nammalwar Sriranganathan
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech Blacksburg, VA, USA
| | - Ramesh Vemulapalli
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University West Lafayette, IN, USA
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Sancho P, Tejedor C, Sidhu-Muñoz RS, Fernández-Lago L, Vizcaíno N. Evaluation in mice of Brucella ovis attenuated mutants for use as live vaccines against B. ovis infection. Vet Res 2014; 45:61. [PMID: 24898325 PMCID: PMC4057616 DOI: 10.1186/1297-9716-45-61] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Accepted: 05/23/2014] [Indexed: 11/28/2022] Open
Abstract
Brucella ovis causes ram contagious epididymitis, a disease for which a specific vaccine is lacking. Attenuated Brucella melitensis Rev 1, used as vaccine against ovine and caprine brucellosis caused by B. melitensis, is also considered the best vaccine available for the prophylaxis of B. ovis infection, but its use for this purpose has serious drawbacks. In this work, two previously characterized B. ovis attenuated mutants (Δomp25d and Δomp22) were evaluated in mice, in comparison with B. melitensis Rev 1, as vaccines against B. ovis. Similarities, but also significant differences, were found regarding the immune response induced by the three vaccines. Mice vaccinated with the B. ovis mutants developed anti-B. ovis antibodies in serum of the IgG1, IgG2a and IgG2b subclasses and their levels were higher than those observed in Rev 1-vaccinated mice. After an antigen stimulus with B. ovis cells, splenocytes obtained from all vaccinated mice secreted similar levels of TNF-α and IL12(p40) and remarkably high amounts of IFN-γ, a crucial cytokine in protective immunity against other Brucella species. By contrast, IL-1α -an enhancer of T cell responses to antigen- was present at higher levels in mice vaccinated with the B. ovis mutants, while IL-10, an anti-inflammatory cytokine, was significantly more abundant in Rev 1-vaccinated mice. Additionally, the B. ovis mutants showed appropriate persistence, limited splenomegaly and protective efficacy against B. ovis similar to that observed with B. melitensis Rev 1. These characteristics encourage their evaluation in the natural host as homologous vaccines for the specific prophylaxis of B. ovis infection.
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Affiliation(s)
| | | | | | | | - Nieves Vizcaíno
- Departamento de Microbiología y Genética, Edificio Departamental, Universidad de Salamanca, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
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Proteomic analysis of detergent resistant membrane domains during early interaction of macrophages with rough and smooth Brucella melitensis. PLoS One 2014; 9:e91706. [PMID: 24643124 PMCID: PMC3958395 DOI: 10.1371/journal.pone.0091706] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 02/13/2014] [Indexed: 12/20/2022] Open
Abstract
The plasma membrane contains discrete nanometer-sized domains that are resistant to non-ionic detergents, and which are called detergent resistant membrane domains (DRMDs) or lipid rafts. Exposure of host cells to pathogenic bacteria has been shown to induce the re-distribution of specific host proteins between DRMDs and detergent soluble membranes, which leads to the initiation of cell signaling that enable pathogens to access host cells. DRMDs have been shown to play a role in the invasion of Brucella into host macrophages and the formation of replicative phagosomes called Brucella-containing vacuoles (BCVs). In this study we sought to characterize changes to the protein expression profiles in DRMDs and to respective cellular pathways and networks of Mono Mac 6 cells in response to the adherence of rough VTRM1 and smooth 16 M B. melitensis strains. DRMDs were extracted from Mono Mac 6 cells exposed for 2 minutes at 4°C to Brucella (no infection occurs) and from unexposed control cells. Protein expression was determined using the non-gel based quantitative iTRAQ (Isobaric Tags for Relative and Absolute Quantitation) mass spectrometry technique. Using the identified iTRAQ proteins we performed enrichment analyses and probed constructed human biochemical networks for interactions and metabolic reactions. We identified 149 proteins, which either became enriched, depleted or whose amounts did not change in DRMDs upon Brucella exposure. Several of these proteins were distinctly enriched or depleted in DRMDs upon exposure to rough and smooth B. melitensis strains which results in the differential engagement of cellular pathways and networks immediately upon Brucella encounter. For some of the proteins such as myosin 9, small G protein signaling modulator 3, lysine-specific demethylase 5D, erlin-2, and voltage-dependent anion-selective channel protein 2, we observed extreme differential depletion or enrichment in DRMDs. The identified proteins and pathways could provide the basis for novel ways of treating or diagnosing Brucellosis.
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Olsen SC, Stoffregen WS. Essential role of vaccines in brucellosis control and eradication programs for livestock. Expert Rev Vaccines 2014; 4:915-28. [PMID: 16372886 DOI: 10.1586/14760584.4.6.915] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Brucellosis, in particular infections with Brucella abortus, Brucella melitensis or Brucella suis, remains a significant human health threat in many areas of the world. The persistence of pathogenic Brucella spp. in domestic livestock or free-ranging wildlife remains unresolved, despite decades of regulatory efforts worldwide. Although vaccination is probably the most economic control measure, administration of currently available vaccines alone is not sufficient for elimination of brucellosis in any host species. Complacency in brucellosis control programs usually results in failure, or at best, limited reductions in disease prevalence or incidence of human infections. New brucellosis vaccines with high efficacy and safety are needed that address the diversity in host species and can be more widely applied under field conditions. Development of safer and more efficacious vaccines alone, or combined with enhancements or increased emphasis on other regulatory program components, could have tremendous impact on reducing the worldwide prevalence of brucellosis and the associated zoonotic infections.
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Affiliation(s)
- Steven C Olsen
- National Animal Disease Center, Bacterial Diseases of Livestock Research Unit, Agricultural Research Service, United States Department of Agriculture, Ames, IA 50010, USA.
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Adone R, Muscillo M, La Rosa G, Francia M, Tarantino M. Antigenic, immunologic and genetic characterization of rough strains B. abortus RB51, B. melitensis B115 and B. melitensis B18. PLoS One 2011; 6:e24073. [PMID: 22065984 PMCID: PMC3204967 DOI: 10.1371/journal.pone.0024073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 07/29/2011] [Indexed: 11/19/2022] Open
Abstract
The lipopolysaccharide (LPS) is considered the major virulent factor in Brucella spp. Several genes have been identified involved in the synthesis of the three LPS components: lipid A, core and O-PS. Usually, Brucella strains devoid of O-PS (rough mutants) are less virulent than the wild type and do not induce undesirable interfering antibodies. Such of them proved to be protective against brucellosis in mice. Because of these favorable features, rough strains have been considered potential brucellosis vaccines. In this study, we evaluated the antigenic, immunologic and genetic characteristics of rough strains B.abortus RB51, B.melitensis B115 and B.melitensis B18. RB51 derived from B.abortus 2308 virulent strain and B115 is a natural rough strain in which the O-PS is present in the cytoplasm. B18 is a rough rifampin-resistan mutant isolated in our laboratory. The surface antigenicity of RB51, B115 and B18 was evaluated by testing their ability to bind antibodies induced by rough or smooth Brucella strains. The antibody response induced by each strain was evaluated in rabbits. Twenty-one genes, involved in the LPS-synthesis, were sequenced and compared with the B.melitensis 16M strain. The results indicated that RB51, B115 and B18 have differences in antigenicity, immunologic and genetic properties. Particularly, in B115 a nonsense mutation was detected in wzm gene, which could explain the intracellular localization of O-PS in this strain. Complementation studies to evaluate the precise role of each mutation in affecting Brucella morphology and its virulence, could provide useful information for the assessment of new, attenuated vaccines for brucellosis.
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Affiliation(s)
- Rosanna Adone
- Dipartimento Sanità Pubblica Veterinaria e Sicurezza Alimentare, Istituto Superiore di Sanità, Roma, Italy.
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Chacón-Díaz C, Muñoz-Rodríguez M, Barquero-Calvo E, Guzmán-Verri C, Chaves-Olarte E, Grilló MJ, Moreno E. The use of green fluorescent protein as a marker for Brucella vaccines. Vaccine 2011; 29:577-82. [DOI: 10.1016/j.vaccine.2010.09.109] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Revised: 08/04/2010] [Accepted: 09/26/2010] [Indexed: 11/27/2022]
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Chen F, He Y. Caspase-2 mediated apoptotic and necrotic murine macrophage cell death induced by rough Brucella abortus. PLoS One 2009; 4:e6830. [PMID: 19714247 PMCID: PMC2729395 DOI: 10.1371/journal.pone.0006830] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 07/29/2009] [Indexed: 12/15/2022] Open
Abstract
Brucella species are Gram-negative, facultative intracellular bacteria that cause zoonotic brucellosis. Survival and replication inside macrophages is critical for establishment of chronic Brucella infection. Virulent smooth B. abortus strain 2308 inhibits programmed macrophage cell death and replicates inside macrophages. Cattle B. abortus vaccine strain RB51 is an attenuated rough, lipopolysaccharide O antigen-deficient mutant derived from smooth strain 2308. B. abortus rough mutant RA1 contains a single wboA gene mutation in strain 2308. Our studies demonstrated that live RB51 and RA1, but not strain 2308 or heat-killed Brucella, induced both apoptotic and necrotic cell death in murine RAW264.7 macrophages and bone marrow derived macrophages. The same phenomenon was also observed in primary mouse peritoneal macrophages from mice immunized intraperitoneally with vaccine strain RB51 using the same dose as regularly performed in protection studies. Programmed macrophage cell death induced by RB51 and RA1 was inhibited by a caspase-2 inhibitor (Z-VDVAD-FMK). Caspase-2 enzyme activation and cleavage were observed at the early infection stage in macrophages infected with RB51 and RA1 but not strain 2308. The inhibition of macrophage cell death promoted the survival of rough Brucella cells inside macrophages. The critical role of caspase-2 in mediating rough B. abortus induced macrophage cell death was confirmed using caspase-2 specific shRNA. The mitochondrial apoptosis pathway was activated in macrophages infected with rough B. abortus as demonstrated by increase in mitochondrial membrane permeability and the release of cytochrome c to cytoplasm in macrophages infected with rough Brucella. These results demonstrate that rough B. abortus strains RB51 and RA1 induce apoptotic and necrotic murine macrophage cell death that is mediated by caspase-2. The biological relevance of Brucella O antigen and caspase-2-mediated macrophage cell death in Brucella pathogenesis and protective Brucella immunity is discussed.
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Affiliation(s)
- Fang Chen
- Unit for Laboratory Animal Medicine and Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Yongqun He
- Unit for Laboratory Animal Medicine and Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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Martins H, Garin-Bastuji B, Lima F, Flor L, Pina Fonseca A, Boinas F. Eradication of bovine brucellosis in the Azores, Portugal—Outcome of a 5-year programme (2002–2007) based on test-and-slaughter and RB51 vaccination. Prev Vet Med 2009; 90:80-9. [DOI: 10.1016/j.prevetmed.2009.04.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2008] [Revised: 04/01/2009] [Accepted: 04/07/2009] [Indexed: 11/16/2022]
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Zygmunt MS, Blasco JM, Letesson JJ, Cloeckaert A, Moriyón I. DNA polymorphism analysis of Brucella lipopolysaccharide genes reveals marked differences in O-polysaccharide biosynthetic genes between smooth and rough Brucella species and novel species-specific markers. BMC Microbiol 2009; 9:92. [PMID: 19439075 PMCID: PMC2698832 DOI: 10.1186/1471-2180-9-92] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2008] [Accepted: 05/13/2009] [Indexed: 02/05/2023] Open
Abstract
Background The lipopolysaccharide is a major antigen and virulence factor of Brucella, an important bacterial pathogen. In smooth brucellae, lipopolysaccharide is made of lipid A-core oligosaccharide and N-formylperosamine O-polysaccharide. B. ovis and B. canis (rough species) lack the O-polysaccharide. Results The polymorphism of O-polysaccharide genes wbkE, manAO-Ag, manBO-Ag, manCO-Ag, wbkF and wbkD) and wbo (wboA and wboB), and core genes manBcore and wa** was analyzed. Although most genes were highly conserved, species- and biovar-specific restriction patterns were found. There were no significant differences in putative N-formylperosamyl transferase genes, suggesting that Brucella A and M serotypes are not related to specific genes. In B. pinnipedialis and B. ceti (both smooth), manBO-Ag carried an IS711, confirming its dispensability for perosamine synthesis. Significant differences between smooth and rough species were found in wbkF and wbkD, two adjacent genes putatively related to bactoprenol priming for O-polysaccharide polymerization. B. ovis wbkF carried a frame-shift and B. canis had a long deletion partially encompassing both genes. In smooth brucellae, this region contains two direct repeats suggesting the deletion mechanism. Conclusion The results define species and biovar markers, confirm the dispensability of manBO-Ag for O-polysaccharide synthesis and contribute to explain the lipopolysaccharide structure of rough and smooth Brucella species.
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Affiliation(s)
- Michel S Zygmunt
- INRA, UR1282, Infectiologie Animale et Santé Publique, IASP, Nouzilly, France.
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Isolation of rifampicin resistant Flavobacterium psychrophilum strains and their potential as live attenuated vaccine candidates. Vaccine 2008; 26:5582-9. [DOI: 10.1016/j.vaccine.2008.07.083] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Revised: 07/28/2008] [Accepted: 07/29/2008] [Indexed: 11/24/2022]
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Robles CA, Nielsen K, Gall D, Willems P. Evaluation of three different antigens in an indirect enzyme-linked immunoassay for the detection of antibodies against Brucella abortus SRB51 in vaccinated heifers. Vet Immunol Immunopathol 2008; 127:153-5. [PMID: 18980780 DOI: 10.1016/j.vetimm.2008.09.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 08/02/2008] [Accepted: 09/12/2008] [Indexed: 11/28/2022]
Abstract
The live attenuated Brucella abortus SRB51 (SRB51) is a partial O-chain-deprived mutant. The relative lack of the polysaccharide prevents it from inducing antibodies detectable by most of the serological tests used for the diagnosis of bovine brucellosis. The performance of three antigens used in an indirect enzyme-linked immunoassay test for detecting SRB51 antibodies were evaluated. A homogeneous group of twenty-five 10-month-old Hereford heifers was used. The animals were bled on day 0 and then subcutaneously vaccinated with 2 ml of a commercially available SRB51 vaccine (Schering-Plough) containing 1x10(7) to 3.4x10(7) viable cells. Blood samples without anticoagulant for sera obtaining were then collected at days 30, 90, 210 and 360 post-vaccination. To detect the SRB51 antibodies, Brucella ovis hot saline extract, B. ovis RLPS (RLPS), and SRB51-RLPS were used. The buffered antigen plate agglutination test and an indirect enzyme-linked immunoassay (I-ELISA) using the smooth LPS (SLPS) antigen from B. abortus were used as control tests. All the sera samples were negative in the BPA test and in the standard I-ELISA using the SLPS. The SRB51-RLPS and the B. ovis RLPS antigens performed better than the B. ovis hot saline extract antigen.
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Affiliation(s)
- C A Robles
- Animal Health Unit, The National Institute for Agricultural Technology (INTA), Bariloche, Argentina.
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Lopez EH, Andrade LH, Resendiz GP, Aparicio ED. Study of Brucellosis Incidence in a Bovine Dairy Farm Infected with Brucella abortus, Where Cattle Was Revaccinated with RB51. ACTA ACUST UNITED AC 2006. [DOI: 10.3923/ijds.2007.50.57] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Nielsen K, Smith P, Yu W, Nicoletti P, Jungersen G, Stack J, Godfroid J. Serological discrimination by indirect enzyme immunoassay between the antibody response to Brucella sp. and Yersinia enterocolitica O:9 in cattle and pigs. Vet Immunol Immunopathol 2006; 109:69-78. [PMID: 16140390 DOI: 10.1016/j.vetimm.2005.07.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 06/28/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
A rapid, inexpensive and rugged serological test that distinguishes cattle and swine infected with Brucella sp. or Yersinia enterocolitica O:9 is described. The test protocol, which is an indirect enzyme immunoassay uses a high concentration of divalent cation chelating agents to minimize binding of Y. enterocolitica O:9 antibody to rough lipopolysaccharide antigen derived from B. abortus RB51. No false positive reactions were observed when testing 100 Canadian cattle and swine without any evidence of brucellosis. The assay detected 91.6% of cattle (n=155) and 93.5% (n=31) of swine infected with Brucella sp. Sera from 58 cattle and 38 swine exposed to Y. enterocolitica O:9 were negative while only 20 sera from 121 'false positive' reactors of unspecified origin gave low level positive reactions, eliminating 84% of the false positive reactions.
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Affiliation(s)
- K Nielsen
- Animal Diseases Research Institute, 3851 Fallowfield Road, Ottawa, Ont., Canada.
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Cloeckaert A, Jacques I, Grilló MJ, Marín CM, Grayon M, Blasco JM, Verger JM. Development and evaluation as vaccines in mice of Brucella melitensis Rev.1 single and double deletion mutants of the bp26 and omp31 genes coding for antigens of diagnostic significance in ovine brucellosis. Vaccine 2004; 22:2827-35. [PMID: 15246618 DOI: 10.1016/j.vaccine.2004.01.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2003] [Revised: 12/29/2003] [Accepted: 01/07/2004] [Indexed: 11/17/2022]
Abstract
The live attenuated Brucella melitensis Rev.1 strain is considered the best vaccine available for the prophylaxis of brucellosis in sheep caused by either B. melitensis or Brucella ovis. However, its application stimulates antibody responses in vaccinated animals indistinguishable by the current conventional serological tests from those observed in infected animals. The periplasmic protein BP26 and the outer membrane protein (OMP) Omp31 are immunodominant antigens in the serological responses of B. melitensis and B. ovis infected sheep, respectively. Accordingly, vaccine strain Rev.1 single and double deletion mutants of the bp26 and omp31 genes were developed, based on the principle that the use of such mutants as vaccines in association with diagnostic tests based on BP26 and Omp31 antigens would allow the serological differentiation between infected and vaccinated animals. The deletion mutants obtained were indistinguishable from the parental Rev.1 strain by conventional bacteriological and typing tests. The expression of their major surface antigens, as determined by reactivity with specific monoclonal antibodies (MAbs), remained unaffected, i.e. smooth-lipopolysaccharide (S-LPS) and OMPs besides in the expression of the antigens whose respective genes were deleted. The bp26 and omp31 deletions did not modify the kinetics of splenic infection nor the residual virulence of Rev.1 in the BALB/c mouse model. Vaccination of BALB/c mice with the deletion mutants conferred significant protective immunity against B. melitensis strain H38 or B. ovis strain PA challenges, to the same extent as that induced by parental Rev.1 strain. Thus, these Rev.1 bp26 or omp31 deletion mutants are promising vaccine candidates against B. melitensis and B. ovis infections and will be further evaluated in sheep.
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Affiliation(s)
- Axel Cloeckaert
- Laboratoire de Pathologie Infectieuse et Immunologie, Unité BioAgresseurs Santé et Environnement, Institut National de la Recherche Agronomique, Nouzilly 37380, France.
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Abstract
Rough mutants of Brucella spp. are attenuated for survival in animal models. However, conflicting in vitro evidence has been obtained concerning the intracellular survival of rough mutants. Transposon-derived rough mutants isolated in our laboratory were previously shown to exhibit small but significant reductions in intracellular survival in a 12-h in vitro assay. Several recent publications report that rough mutants exhibited increased macrophage uptake relative to their smooth parental strains, and a reduction in numbers at the end of the assay has been interpreted as intracellular killing. In an effort to explore the role of O antigen in the interaction between Brucella abortus and macrophages, we have monitored the uptake of rough mutants and survival in vitro by using the murine macrophage cell line J774.A1. The results confirm a 10- to 20-fold-increased uptake of rough mutants over that of smooth organisms under standard conditions. Recovery of the rough mutants persisted up to 8 h postinfection, but at the point when intracellular replication of the smooth organisms was observed, the number of rough organisms recovered declined. Fluorescence microscopy revealed the intracellular multiplication of both smooth and rough organisms, and assays performed in the absence of antibiotic confirmed the replication of the rough organisms. Examination by phase-contrast microscopy revealed the lytic death of macrophages infected with the rough mutants, which was confirmed by the release of lactate dehydrogenase (LDH) from the cell cytoplasm. Thus, the decline in the number of rough organisms was the result of the lysis of macrophages and not from intracellular killing. The cytopathic effect is characterized as necrotic rather than apoptotic cell death based on early LDH release, annexin V and propidium iodide staining, morphological changes of infected cells and nuclei, and glycine protection. The cytopathic effect was observed with macrophages at multiplicities of infection (MOIs) of as low as 20 and was not observed with epithelial cells at MOIs of as high as 2000. These findings suggest a role for O antigen during the early stages of host-agent interaction that is essential in establishing an intracellular niche that maintains and supports persistent intracellular infection resulting in disease.
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Affiliation(s)
- Jianwu Pei
- Veterinary Pathobiology, Texas A&M University and Texas Agricultural Experiment Station, College Station, Texas 77843-4467, USA
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Abstract
The first effective Brucella vaccine was based on live Brucella abortus strain 19, a laboratory-derived strain attenuated by an unknown process during subculture. This induces reasonable protection against B. abortus, but at the expense of persistent serological responses. A similar problem occurs with the B. melitensis Rev.1 strain that is still the most effective vaccine against caprine and ovine brucellosis. Vaccines based on killed cells of virulent strains administered with adjuvant induced significant protection but also unacceptable levels of antibodies interfering with diagnostic tests. Attempts were made to circumvent this problem by using a live rough strain B. abortus 45/20, but this reverted to virulence in vivo. Use of killed cells of this strain in adjuvant met with moderate success but batch to batch variation in reactogenicity and agglutinogenicity limited application. This problem has been overcome by the development of the rifampicin-resistant mutant B. abortus RB51 strain. This strain has proved safe and effective in the field against bovine brucellosis and exhibits negligible interference with diagnostic serology. Attempts are being made to develop defined rough mutant vaccine strains that would be more effective against B. melitensis and B. suis. Various studies have examined cell-free native and recombinant proteins as candidate protective antigens, with or without adjuvants. Limited success has been obtained with these or with DNA vaccines encoding known protective antigens in experimental models and further work is indicated.
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Affiliation(s)
- Gerhardt G Schurig
- Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
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