Population Medicine & Diagnostic Sciences


Cats  

Advancing the health and well-being of animals and people


Dogs  

Advancing the health and well-being of animals and people


Pig  

Advancing the health and well-being of animals and people


Cells  

Advancing the health and well-being of animals and people


Cattle  

Advancing the health and well-being of animals and people


Horses  

Advancing the health and well-being of animals and people


Yung-Fu Chang

DrChangDirector, Infectious Disease Research Laboratory
Animal Health Diagnostic Center
Professor
Department of Population Medicine and Diagnostic Sciences
C1-114, Vet Medical Center
College of Veterinary Medicine
Cornell University
Ithaca, New York 14853-5786
Phone:  607-253-3675
e-mail: yc42@cornell.edu

 

Research Interests

Research interests include molecular biology of infectious disease; DNA and recombinant subunit vaccine development; molecular basis of bacterial pathogenesis; immunopathology of infectious diseases; molecular diagnosis of infectious diseases; host defense mechanisms; comparative genomics and proteomics.

Dr. Chang’s lab has applied the functional genomics approaches to study the pathogenesis of Clostridium difficile infection. Using multi-omics methods and animal models, we are investigating the virulence mechanisms of Clostridium difficile. C. difficile has emerged in recent years as the leading cause of nosocomial diarrhea. We use genome sequencing, RNA-seq and proteome approaches to analyze the evolutionary changes in historic and recently emergent hypervirulent strains. Production of spores that are very resistant to disinfectants is major reason for persistent hospital associated C. difficile infections. To understand the conditions and cellular pathways that trigger spore formation, we are testing the sporulation kinetics of C. difficile exposed to over 700 nutrient conditions. We are also studying how cellular metabolism controls the toxin production in C. difficile. For these studies, we use a mouse model of infection and employ metabolome and metagenome analysis to understand the physiological changes in the gut following C. difficile infection.

Our lab is also working on the adhesins and host cell receptors interaction. One of the most effective strategies in preventing bacterial infection is to block bacterial attachment to host cell receptors and subsequent colonization of host mucosal surfaces during primary stages of infection. Bacterial attachment to host tissues usually involves bacterial surface adhesin proteins (microbial surface components recognizing adhesive matrix molecules, MSCRAMM) that interact with host cell receptors. Adhesins used as vaccine components may induce protection by impeding colonization, thereby blocking infection, and preventing disease inducing infections. We have been working on the adhesins from Lepotospira spp. and Mycobacterium avium subsp. paratuberculosis and their interaction with host cell receptors, extracellular matrixes (ECMs) to understand how their interaction may contribute to virulence and may also assist in the development of new therapeutic strategies and the construction of a protective vaccine against the diseases.

We have working on the development recombinant protein vaccines or attenuated mutants against Leptospira spp. and Mycobacterium avium subsp. paratuberculosis. Additionally, we’ve been working on vaccine adjuvant and vaccine delivery systems using microsphere, liposome and attenuated Salmonella as a carrier.

Education

  • DVM - 1974 National Pingtung Institute of Agriculture, Taiwan (Currently National Ping-Tung University of Science and Technology)
  • M.S. - 1981 University of Idaho, Moscow, Idaho (Immunology/Pathology)
  • Ph.D. - 1984 Texas A&M University, College Station, Texas (Microbiology/Immunology)
  • Postdoc - 1984-1989 Texas A&M University, College Station, Texas (Molecular Biology/Genetics)


Research and Professional Experience

  • 1974-1979 Assistant Pathologist, Veterinary Pathology Division, Taiwan Provincial Research Institute for Animal Health, Taipei, Taiwan
  • 1979-1981 Research Assistant and Graduate Student, Department of Veterinary Science, University of Idaho, Moscow, Idaho
  • 1981-1984 Research Assistant and Graduate Student, Department of Veterinary Microbiology and Parasitology, College of Veterinary Medicine, Texas A&M University, College Station, Texas
  • 1984-1985 Research Associate, Department of Medical Biochemistry and Genetics, College of Medicine, Texas A&M University, College Station, Texas
  • 1986-1989 Assistant Research Scientist, Department of Medical Biochemistry and Genetics, College of Medicine, and Department of Biochemistry and Biophysics, College of Agriculture & Life Science, Texas A&M University, College Station, Texas
  • 1989-1996 Assistant Professor and Assistant Director of the Microbiology Section, Diagnostic Center, College of Veterinary Medicine, Cornell University, Ithaca, New York
  • 1996-2002 Associate Professor and Assistant Director of the Microbiology Section, Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York
  • 2003 Jan - Jul Visiting Professor, Department of Infectious disease and Medicine, College of Medicine, Stanford University. Stanford, California
  • 2003-present Professor, Department of Population Medicine & Diagnostic
    Sciences, and Director of infectious disease program, New York State Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University, Ithaca, New York


Honors and Awards

  • Beta Rho Chapter of Phi Sigma National Honor Society
  • Diplomate of the American College of Veterinary Microbiologist
  • The Society of Phi Zeta
  • Who's Who in America?
  • Distinguish alumni, National Ping-Tung University of Sciences and Technology, 2007.

 

Professional Society Memberships

  • American Association of Veterinary Laboratory Diagnosticians
  • American Leptospirosis Research Conference, Inc.
  • American Society for Microbiology
  • American College of Veterinary Microbiologist
  • Conference of Research Workers in Animal Diseases
  • International Leptospirosis Society
  • New York State Veterinary Society
  • Society of Sigma Xi
  • The Society of Phi Zeta
  • United States Animal Health Association
  • AALVD Enteric Disease Committee, 1991-present
  • Associate Editor, Journal of Veterinary Science, 2006-Present
  • Associate Editor, PLoS One, 2012-Present
  • Editors-in-Chief, Advance in Microbiology, 2012-Present
  • Editors-in-Chief, Advances in Infectious Diseases, 2013-Present
  • Treasure, American Leptospirosis Research Conference, Inc., 2001-present
  • Adviser, Cornell Taiwanese Student Association (Graduate students), 1996-present

 

Selected Publications

  1. Chang, Y. F., R. Young., D. Post, and D. K. Struck. 1987. Identification and characterization of the Pasteurella haemolytica leukotoxin. Infect. Immun. 55: 2348-2354.
  2. Chang, Y. F., R. Young, and D. K. Struck. 1989. Cloning and characterization of a hemolysin gene from Actinobacillus (Haemophilus) pleuropneumoniae DNA &Cell biology: 8: 635-647.
  3. Cruz, W.T., R. Young, Y. F. Chang, and D.K. Struck. 1990. Deletion analysis resolves cell-binding and lytic domains of the Pasteurella leukotoxin. Mol. Microbiol. 4: 1933-1939.
  4. Chang, Y. F., R. Young, and D.K. Struck. 1991. The Actinobacillus pleuropneumoniae determinant: unlinked appCA and appBD loci flanked by pseudogenes. J. Bacteriol. 173: 5151-5158.
  5. McWhinney, D.R., Y. F. Chang, R.Young, and D. K.Struck. 1992 Separable domains define target cell specificities of the RTX hemolysin from Actinobacillus pleuropneumoniae. J. Bacteriol. 174: 291-297.
  6. Appel, M. J.G., S. Allan, R. H. Jacobson, T.L. Lauderdale, Y. F. Chang, S. J. Shin, J. Thomford, R. Todhunter, and B. A. Summers. 1993. Experimental Lyme disease in dogs produced arthritis and persistent infection. J. Infect. Dis. 167: 651-664.
  7. Chang, Y. F., D. P. Ma, J. Shi, and M. M. Chengappa. 1993. Molecular characterization of a leukotoxin gene from a Pasteurella haemolytica-like organism, encoding a new member of RTX family. Infect. Immun. 61: 2089-2095.
  8. Chang, Y. F., J. Shi, D. P. Ma, S. J. Shin, and D. H. Lein. 1993. Molecular analysis of the Actinobacillus pleuropneumoniae RTX toxin-III gene cluster. DNA. Cell Biol. 12: 351-362.
  9. Chang, Y. F., M. J. Appel, R. H. Jacobson, S. J. Shin, P. Harpending, R. Straubinger, L. A. Patrican, H. Mohammed, and B. A. Summers. 1995. Recombinant OspA protects dogs against infection and disease caused by Borrelia burgdorferi. Infect. Immun. 63: 3543-3549.
  10. Chang, Y. F., R. Straubinger, R. H. Jacobson, J. B. Kim, T. J. Kim, D. Kim, S. J. Shin, and M. J. G. Appel. 1996. Dissemination of Borrelia burdorferi after experimental infection in dogs. J. Spiro. Tick-Borne Dis. 3: 80-86.
  11. Straubinger, R. K., A. F. Straubinger, L. Harter, R. H. Jacobson, Y. F. Chang, B. A. Summers, H. N. Erb, and M. J. G. Appel. 1997. Borrelia burgdorferi migration and proliferation causes up-regulation of interleukin-8 in synovial membranes of experimentally infected dogs. Infect. Immun. 65: 1273-1285.
  12. Chang, Y. F., V. Novosel, S. P. McDonough, R. H. Jacobson, C. F. Chang, T. Divers, F. W. Quimby, S. Shin, and D. H. Lein. 1999. Vaccination against Lyme disease with recombinant Borrelia burgdorferi outer surface protein A (OspA) in horses. Vaccine 18: 540-548.
  13. Chang, Y. F.,S. P. McDonough, K.S. Shin, C. F. Chang, and T. Divers. 2000. Human granulocytic ehrlichiosis agent (HGE) infection in a pony vaccinated with recombinant OspA vaccine and challenged by exposure to naturally infected ticks. Clin. Diag. Lab. Immunol. 7: 68-71.
  14. Simpson, K.W., D. Strauss-Ayali, E. Scanziani, R. K. Straubinger, P. L. McDonough, A.F. Straubinger, Y. F. Chang, C. Domeneghini, N. Arebi, and J. Calm. 2000. Helicobacter felis infection is associated with lymphpoid follicular hyperplasia and mild gastritis but normal gastric secretory function in cats. Infect. Immun. 68: 779-790.
  15. Simpson, K.W., D. Strauss-Ayali, E. Scanziani, R. K. Straubinger, P. L. McDonough, A. F. Straubinger, Y. F. Chang, M. Esteves, J. G. Fox, C. Domeneghini, N. Arebi, and J. Calam. 2001. Gastric secretory function in cats with Helicobacter pylori infection. Helicobacter 6: 1-14.
  16. Raghavan, P. U. M., Y. F. Chang, S. S. D. Jusuf, S. Artiushin, J. F. Timoney, S. P. McDonough, S. C. Barr, T. J. Divers, P. McDonough, K. W. Simpson, and H. Mohammed. 2002. Cloning and molecular characterization of an immunogenic LigA of Leptospira interrogans. Infect. Immun. 70:5924-5930.
  17. Teng, C.H., R. U.M. Palaniappan, and Y. F. Chang. 2003. Cloning and characterization of an Ehrlichia canis gene encoding a protein localized to the morula membrane. Infect. Immun. 71:2218-2225.
  18. Palaniappan, R. U., Y. F. Chang, F. Hassan, S.P. McDonough, M. Pough, S.C. Barr, K. W. Simpson, H. O. Mohammed, S. Shin, P. McDonough, R. Zuerner, J. Qu, & B. Roe. 2004. Expression of leptospiral immunoglobulin-like protein from Leptospiral interrogans and evaluation of its diagnostic potential in kinetic enzyme linked immunosorbent assay. J. Med. Microbiol. 53: 975-84.
  19. Shin, S.J., C.F. Chang, C. C. Chang, S. P. McDonough, B. Thompson, H.S. Yoo, and Y. F. Chang. 2005. In vitro cellular immune response to recombinant antigens of Mycobacterium avium subsp. paratuberculosis. Infect. Immun. 73:5074-5085.
  20. Ku, Y.W., S. P. McDonough, R.U.M. Palaniappan, C. F. Chang, Y. F. Chang. 2005. Identification and characterization of in vivo attenuated mutants of Salmonella enterica serovar Choleraesuis using signature-tagged mutagenesis in a pig infection model. Infect. Immun. 73:8194-8203.
  21. Raghavan, P. U. M., S. P. McDonough, T. J. Divers, C. S. Chen, M.J. Pan, M. Matsumoto and Y. F. Chang. 2006. Immunoprotection of recombinant leptospiral immunoglobulin like A protein (LigA) against Leptospira interrogans serovar Pomona infection. Infect. Immun. 74:1745-1750.
  22. Palaniappan, R. U., Y. Zhang, D. Chiu, A. Torres, C. DebRoy, T. S. Whittam and Y. F. Chang. 2006. Differentiation of Escherichia coli pathotypes by oligonucleotide spotted array. J. Clin. Microbiol. 44:1495-1501.
  23. Chang, Y.F., C. S. Chen, R. U.M. Palaniappan, S. P. McDonough, W. Yang, M. J. Pan, and C. F. Chang. 2007. Immunogenicity and protection of the recombinant leptospiral immunogenic proteins as vaccine candidates. Vaccine 25: 8190-8197.
  24. Yu, C.Y., S. J. chou, C. M. Yeh, M.R. Chao, K. C. Huang, Y. F. Chang, C. S. Chiou, F. X. Weill, C. H. Chiu, C. H. Chu, and C. S. Chu. 2007. Prevalence and characterization of multidrug-resistant (ACSSuT) Salmonella enterica serovar Typhimurium isolated from our Gosling’s farms and a hatchery farm. J. Clin. Microbiol. 46:522-526.
  25. Faisal, S.M., W. Yan, C. S. Chen, R. U.M. Palaniappan, S. P. McDonough, and Y. F. Chang. 2008. Evaluation of protective immunity of Leptospira immunoglobulin like protein A (LigA) DNA vaccine against challenge in hamsters. Vaccine, 26:277-287.
  26. Chen, L. H., K. Kathaperumal, C. J. Huang, S. P. McDonough, S. Stehman, B. Akey, J. Huntley, C.F. Chang and Y. F. Chang. 2008. Immune responses in mice to Mycobacterium avium subsp. paratuberculosis following vaccination with a novel 74F recombinant polyprotien. Vaccine 26:1253-1262.
  27. Kathaperumal, K., S. U. Park, S. P. McDonough, S. Stehman, B. Akey, J. Huntley, S. Wong, L. H. Chen, C.-F. Chang and Y. F. Chang. 2008. Vaccination with recombinant Mycobacterium avium subsp. paratuberculosis proteins induces differential immune responses and protects calves against infection by oral challenge. Vaccine, 26:1652-1663.
  28. Park, S.U., K. Kathaperumal, S. McDonough, B. Akey, J. Huntley, J. P. Bannantine and Y.F. Chang. 2008. Immunization with a DNA vaccine cocktail induces a Th1 response and protects mice against Mycobacterium avium subsp. paratuberculosis. Vaccine. 26:4329-4337.
  29. Lin, Y.P. R. Raman, Y. Sharma, and Y. F. Chang. 2008. Calcium binds to Leptospiral immunoglobulin-like protein, LigB and modulates fibronectin-binding. J. Biol. Chem. 283(12): 25140-25149.
  30. Kathaperumal, K,, V. Kumanan, S. McDonough, L. H. Chen, S. U. Park, M. A. Moreira, B. Akey, J. Huntley, C. F. Chang, and Y. F. Chang 2009. Evaluation of immune responses and protective efficacy in a goat model following immunization with a coctail of recombinant antigens and a polyprotein of Mycobacterium avium subsp. paratuberculosis. Vaccine 27:123-135.
  31. Faisal, S.M., W. Yan, S. P. McDonough, and Y. F. Chang 2009. Leptospira immunoglobulin-like protein A variable region (LigAvar) incorporated in Liposomes and PLGA-Microspheres produces a robust immune response correlating to protective immunity. Vaccine 27:378-387.
  32. Yan, W., S. M. Faisal, S. P. McDonough, T. J. Divers, S. C. Barr, M. J. Pan, C. F. Chang and Y.F. Chang. 2009. Recombinant Leptospira Immunoglobulin-Like Protein B (rLigB) protects hamsters against lethal Leptospira interrogans infection. Microbes Infect.11:230-237.
  33. Janvilisri T., J. Scaria, A. Thompson, A. Nicholson, B. Limbargo, L. G. Arroyo, J. G. Songer, Y. T. Grohn, and Y. F. Chang. 2009. Microarray identification of Clostridium difficile core components and divergent regions associated with host origin. J. Bacteriol. 191:3881-3891.
  34. Lin Y.P., D.W. Lee, S. P. McDonough, L. K. Nicholson, Y. Sharma, and Y. F. Chang.2009. Repeated domains of leptospira immunoglobulin-like proteins interact with elastin and tropoelastin. J. Biol. Chem. 284:19380-19391.
  35. Lin Y.P., A. Greenwood, L. K. Nickolson, Y. Sharma, S. P.McDonough, and Y. F. Chang. 2009. Fibronectin binds to and induces conformational change in a disordered region of Leptospiral immunoglobulin-like protein B. J. Biol. Chem. 284:23547-23557.
  36. Faisal, S.M., W. Yan, S. P. McDonough, and Y. F. Chang. 2009. Immune response and prophylactic efficacy of smegmosomes in a hamster model of leptospirosis. Vaccine, 27:6129-6136.
  37. Faisal, S.M., W. Yan, S. P. McDonough, M. J. Pan, C. F. Chang and Y. F. Chang. 2009. Leptosome-associated antigens conferred significantly higher levels of protection against leptospirosis in hamsters compared to those associated with conventional liposomes. Vaccine, 27:6537-6545.
  38. Janvilisri T., J. Scaria, R. Gleed, S. Fubini, M. M. Bonkosky, Y. T. Grohn, and Y. F. Chang. 2010. Development of a microarray for identification of pathogenic Clostridium species. Diagn. Microbiol. Infect. Dis. 66:140-147.
  39. Yan, W., S. M. Faisal, S. P. McDonough, C. F. Chang, M. J. Pan, and Y.F. Chang. 2010. Identification and characterization of OmpA-like proteins as novel vaccine candidates for Leptospirosis. Vaccine. 28:2277-2283.
  40. Janvilisri T., J. Scaria, and Y. F. Chang. 2010. Transcriptional profiling of Clostridium difficile and Caco-2 cells during infection. J. Infect. Dis. 202:282-290.
  41. Lin Y.P., S. P. McDonough, Y. Sharma and Y.F. Chang. 2010. The terminal immunoglobulin-like repeats of LigA and LigB of Leptospira enhance their binding to gelatin binding domain of fibronectin and host cells. Plos one: 5:e11301.
  42. Scaria, J., L. Ponnala, T. Janvilisri, W. Yan, L. A. Mueller and Y. F. Chang. 2010. Analysis of Ultra Low Genome Conservation in Clostridium difficile. PLoS One. 5: e15147.
  43. Rama, R., V. Rajanikanth, R. U. M. Palaniappan, Y.P. Lin, H. He, S. P. McDonough, Y. Sharma and Y. F. Chang. 2010. Big Domains are Novel Ca2+-binding Modules: Evidences from Big Domains of Leptospira immunoglobulin-like (Lig) Proteins. PLoS One. e14377.
  44. Lin, Y.P., C. J. Kuo, X. Koleci, S. P. McDonough, and Y. F. Chang. 2011. Manganese binds to Clostrdium difficile Fbp68 and is essential for fibronectin binding. J. Biol. Chem. 286:3957-3969, 2011.
  45. Lin, Y.P., S. P. McDonough, Y. Sharma, and Y. F. Chang. 2011. Leptospiral immunoglobulin-like protein (LigB) binds to the C-teminal fibrinogen αC domain inhibiting fibrin clot formation, platelet adhesion, and aggregation. Mol. Microbiol. 79:1063-1076.
  46. Faisal S.M, J. W. Chen, S.P. McDonough, C.F. Chang, C.H. Teng, and Y.F. Chang. 2011. Immunostimulatory and antigen delivery properties of liposomes made up of total polar lipids from non-pathogenic bacteria leads to efficient induction of both innate and adaptive immune responses. Vaccine 29:2381-2391.
  47. Scaria J., T. Janvilisri, S. Fubini, R. D. Gleed, S. P. McDonough, and Y.F. Chang. 2011. Clostridium difficile transcriptome analysis using pig ligated loop model reveals modulation of pathways not modulated in vitro. J. Infect. Dis. 203:1613-1620.
  48. Cao Y, S.M. Faisal,W. Yan, Y.C. Chang,S. P. McDonough,N. Zhang, B. L.Akey, and Y. F. Chang. 2011. Evaluation of novel fusion proteins derived from extracellular matrix binding domains of LigB as vaccine candidates against leptospirosis in a hamster model. Vaccine. 29:7379-86
  49. Chen J.W, S. M.Faisal, S. Chandra, S. P. McDonough, M. A. Moreira, J. Scaria, C. F. Chang, J. P. Bannantine, B. Akey B, and Y. F. Chang. 2012 Immunogenicity and protective efficacy of the Mycobacterium avium subsp. paratuberculosis attenuated mutants against challenge in a mouse model. Vaccine. 30:3015-3025.
  50. Kuo C.J, H. Bell, C. L. Hsieh, C. P. Ptak, and Y. F. Chang. 2012. The novel Mycobacteria antigen 85 complex binding motif on Fibronectin.J Biol Chem. 287:1892-1902.
  51. Mao BH, Chang YF, Scaria J, Chang CC, Chou LW, Tien N, Wu JJ, Tseng CC, Wang MC, Chang CC, Hsu YM, Teng CH. 2012. Identification of Escherichia coli genes associated with urinary tract infections. J. Clin. Microbiol. 50:449-456.
  52. Chen, J.W., J. Scaria and Y. F. Chang. 2012. Phenotypic and transcriptomic response of auxotrophic Mycobacterium avium subsp. paratuberculosis leuD mutant under environmental stress. PLoS one. 7:e37884.
  53. Janvilisri, T., J. Scaria, C. H. Teng, S. P. McDonough, R. D. Gleed, S. L Fubini, S. Zhang, B. L. Akey, Y.F. Chang. 2012. Temporal differential proteomes of Clostridium difficile in the pig ileal-ligated loop model. PLoS one. 7: e45608.
  54. Chandra S., S. M. Faisal, J. W. Chen, T.T. Chen, S. P. McDonough, S. Liu, M. A. P. Moreira, B. L. Akey, C. F. Chang, and Y.F. Chang. 2012. Immune response and protective efficacy of live attenuated Salmonella vaccine expressing antigens of Mycobacterium avium subsp. paratuberculosis against challenge in mice. Vaccine, 31:242-251
  55. Stabel, J.R., A, Barnhill, J. P. Bannantine, Y. F. Chang, and M. A. Osman. 2012. Evaluation of protection in a mouse model after vaccination with Mycobacterium avium subsp. paratuberculois protein cocktails. Vaccine, 31(1):127-34.
  56. Kuo, C. J., C. P. Ptak, C.L. Hsieh, B. L. Akey, and Y. F. Chang. 2013. Elastin, a Novel Extracellular Matrix Protein Adhering to Mycobacteria Antigen 85 Complex. J. Biol. Chem. 288:3886-3896.
  57. Chen J.W., J. Scaria, C. Mao, B. Sobral, S. Zhang, T. Lawley, and Y. F. Chang. 2013. Proteomic comparison of historic and recently emerged hypervirulent Clostridium difficile strains. J Proteome Res. 12:1151-1161.
  58. Faisal S.M., J. W. Chen1, F. Yan, T. T. Chen, N. M. Useh, W. Yan, S. Guo, S.J. Wang, A. L. Glaser, S. P. McDonough, B. Singh, W. C. Davis , B. L. Akey, and Y. F. Chang. 2013. Evaluation of Mycobacterium avium subsp. paratuberculosis leuD mutant as vaccine candidate against challenge in a caprine model. Clin. Vaccine Immunol. 20:572-591.
  59. Yan, W., M. H. Saleem, P. McDonough, S. P. McDonough,T. J. Divers, Y. F. Chang. 2013. Development of an ELISA using recombinant LigACon4-7.5 as antigen for the diagnosis of equine leptospirosis. Clin Vaccine Immunol. 20:1143-1149.
  60. Raman, R., C. P. Ptak, C. L. Hsieh, R. E. Oswald, Y. F. Chang and Y. Sharma.2013. The Perturbation of Tryptophan Fluorescence by Phenylalanine to Alanine Mutations Identifies the Hydrophobic Core in a Subset of Bacterial Ig-like Domains. Biochemistry. 52:4589-4591.
  61. Faisal, S. M., Y. Falong, T.T. Chen, N. Useh, S. Guo, W,Yan, S. J. Wang, A. L. Glaser, S. P. McDonough, B. Singh, and Y. F. Chang. 2013. Evaluation of a Salmonella vectored vaccine expressing Mycobacterium avium subsp. paratuberculosis antigens against challenge in a goat model. PLoS One. e70171.