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Lovett AL, Riley CB, Chapman V, Bell B, Bishop B, Grierson A, Johnstone LJ, Sykes BW. Tetanus prophylaxis in horses: guidelines for New Zealand and Australia based on a critical appraisal of the evidence. N Z Vet J 2024; 72:241-255. [PMID: 38910032 DOI: 10.1080/00480169.2024.2365283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 05/19/2024] [Indexed: 06/25/2024]
Abstract
Horses are exquisitely sensitive to tetanus neurotoxin and are exposed to the risk of infection with Clostridium tetani throughout life. The vaccine against tetanus is highly effective at preventing disease, whereas tetanus in unvaccinated populations is associated with high mortality rates. Current guidelines in New Zealand and Australia for the available vaccine contain contradictions and limitations surrounding the optimal tetanus immunisation protocols for both adult horses and foals. This review critically evaluates the scientific literature on tetanus prophylaxis in horses within the context of equine practice and available products in New Zealand and Australia. The review was conducted by a panel of industry and specialist veterinarians to obtain agreement on nine equine tetanus prophylaxis guidelines for practising veterinarians. The primary protocol for tetanus toxoid (TT) immunisation consists of a three-dose series IM for all horses ≥ 6 months of age, and a four-dose series IM is proposed if commencing vaccination in foals between 3 and 6 months of age. Tetanus prophylaxis in foals < 3 months of age relies on passive immunity strategies. Following the completion of the primary protocol, a TT booster dose IM should be administered within 5 years, and every 5 years thereafter. When followed, these protocols should provide adequate protection against tetanus in horses. Additional tetanus prophylaxis guidelines are provided for veterinarians attending a horse experiencing a known "risk event" (e.g. wound, hoof abscess, surgery, umbilical infection). When a correctly vaccinated horse experiences a risk event, pre-existing immunity provides protection against tetanus. When an unvaccinated horse or one with unknown vaccination status, or a foal born to an unvaccinated dam, experiences a risk event, TT IM and tetanus antitoxin (TAT) 1,500 IU SC should be administered simultaneously at separate sites, and the TT primary immunisation protocol should subsequently be completed for the horse's respective age. In previously immunised pregnant broodmares, a TT booster dose administered 4-8 weeks prior to parturition optimises the transfer of passive immunity against tetanus to the newborn foal via colostrum; provided that post-natal IgG concentration in serum is > 800 mg/dL (8 g/L), such foals should be passively protected against tetanus up to 6 months of age. Survivors of clinical tetanus must still receive the primary protocol for vaccination against tetanus. In summary, all horses in New Zealand and Australia should be vaccinated against tetanus with protection maintained throughout life via TT booster doses, facilitated by accurate medical record keeping and client education.
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Affiliation(s)
- A L Lovett
- Tāwharau Ora - School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - C B Riley
- Tāwharau Ora - School of Veterinary Science, Massey University, Palmerston North, New Zealand
- Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - V Chapman
- Zoetis New Zealand Ltd., Auckland, New Zealand
| | - B Bell
- VetSouth Equine, Invercargill, New Zealand
| | - B Bishop
- Canterbury Equine Surgical Consultancy Ltd., Prebbleton, New Zealand
| | - A Grierson
- Auckland Veterinary Centre, Takanini, New Zealand
| | - L J Johnstone
- Tāwharau Ora - School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - B W Sykes
- Tāwharau Ora - School of Veterinary Science, Massey University, Palmerston North, New Zealand
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Cohen ND, Kahn SK, Bordin AI, Gonzales GM, da Silveira BP, Bray JM, Legere RM, Ramirez-Cortez SC. Association of pneumonia with concentrations of virulent Rhodococcus equi in fecal swabs of foals before and after intrabronchial infection with virulent R. equi. J Vet Intern Med 2022; 36:1139-1145. [PMID: 35322902 PMCID: PMC9151490 DOI: 10.1111/jvim.16409] [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: 01/06/2022] [Revised: 03/08/2022] [Accepted: 03/09/2022] [Indexed: 12/03/2022] Open
Abstract
Background Intragastric administration of virulent Rhodococcus equi protects foals against subsequent experimental intrabronchial (IB) infection, but it is unknown whether R. equi naturally ingested by foals contributes to their susceptibility to pneumonia. Hypothesis Fecal concentration of virulent R. equi before IB infection with R. equi is positively associated with protection from pneumonia in foals. Animals Twenty‐one university‐owned foals. Methods Samples were collected from experimental studies. Five foals were gavaged with live, virulent R. equi (LVRE) at age 2 and 4 days; the remaining 16 foals were not gavaged with LVRE (controls). Fecal swabs were collected from foals at ages 28 days, immediately before IB infection. Foals were monitored for clinical signs of pneumonia, and fecal swabs were collected approximately 2 weeks after IB infection. Swabs were tested by quantitative PCR for concentration of virulent R. equi (ie, copy numbers of the virulence‐associated protein A gene [vapA] per 100 ng fecal DNA). Results Fecal concentrations of virulent R. equi (vapA) before IB infection were significantly (P < .05) lower in control foals (25 copies/100 ng DNA [95% CI, 5 to 118 copies/100 ng DNA) that developed pneumonia (n = 8) than in healthy control foals (n = 8; 280 copies/100 ng DNA; 95% CI, 30 to 2552 copies/100 ng DNA) or those gavaged with LVRE (707 copies/100 ng DNA, 95% CI, 54 to 9207 copies/100 ng DNA). Conclusions and Clinical Importance Greater natural ingestion of LVRE might contribute to protection against pneumonia among foals.
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Affiliation(s)
- Noah D Cohen
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Susanne K Kahn
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Angela I Bordin
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Giana M Gonzales
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Bibiana Petri da Silveira
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Jocelyne M Bray
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Rebecca M Legere
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Sophia C Ramirez-Cortez
- Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, USA
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Cywes-Bentley C, Rocha JN, Bordin AI, Vinacur M, Rehman S, Zaidi TS, Meyer M, Anthony S, Lambert M, Vlock DR, Giguère S, Cohen ND, Pier GB. Antibody to Poly-N-acetyl glucosamine provides protection against intracellular pathogens: Mechanism of action and validation in horse foals challenged with Rhodococcus equi. PLoS Pathog 2018; 14:e1007160. [PMID: 30024986 PMCID: PMC6053243 DOI: 10.1371/journal.ppat.1007160] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 06/15/2018] [Indexed: 12/16/2022] Open
Abstract
Immune correlates of protection against intracellular bacterial pathogens are largely thought to be cell-mediated, although a reasonable amount of data supports a role for antibody-mediated protection. To define a role for antibody-mediated immunity against an intracellular pathogen, Rhodococcus equi, that causes granulomatous pneumonia in horse foals, we devised and tested an experimental system relying solely on antibody-mediated protection against this host-specific etiologic agent. Immunity was induced by vaccinating pregnant mares 6 and 3 weeks prior to predicted parturition with a conjugate vaccine targeting the highly conserved microbial surface polysaccharide, poly-N-acetyl glucosamine (PNAG). We ascertained antibody was transferred to foals via colostrum, the only means for foals to acquire maternal antibody. Horses lack transplacental antibody transfer. Next, a randomized, controlled, blinded challenge was conducted by inoculating at ~4 weeks of age ~106 cfu of R. equi via intrabronchial challenge. Eleven of 12 (91%) foals born to immune mares did not develop clinical R. equi pneumonia, whereas 6 of 7 (86%) foals born to unvaccinated controls developed pneumonia (P = 0.0017). In a confirmatory passive immunization study, infusion of PNAG-hyperimmune plasma protected 100% of 5 foals against R. equi pneumonia whereas all 4 recipients of normal horse plasma developed clinical disease (P = 0.0079). Antibodies to PNAG mediated killing of extracellular and intracellular R. equi and other intracellular pathogens. Killing of intracellular organisms depended on antibody recognition of surface expression of PNAG on infected cells, along with complement deposition and PMN-assisted lysis of infected macrophages. Peripheral blood mononuclear cells from immune and protected foals released higher levels of interferon-γ in response to PNAG compared to controls, indicating vaccination also induced an antibody-dependent cellular release of this critical immune cytokine. Overall, antibody-mediated opsonic killing and interferon-γ release in response to PNAG may protect against diseases caused by intracellular bacterial pathogens. Development of effective vaccines for diseases such as tuberculosis, brucellosis and others caused by intracellular pathogens has proved challenging, as data exist supporting both antibody and cellular immune effectors as mediators of protection. To address this problem against an important, and representative, equine intracellular pathogen, we chose to test a vaccine candidate for the ability to protect horse foals challenged at 4 weeks of age with Rhodococcus equi. To make these foals immune, their pregnant mares were immunized with a vaccine targeting the conserved surface antigen found on many microbes, termed PNAG. Antibody in the pregnant mares was transferred to their foals and, after the foals were challenged, 91% of those born to vaccinated mares were protected against R. equi pneumonia. Meanwhile, 86% of the non-vaccinated controls developed pneumonia. We also showed antibody to PNAG could kill various bacteria that produce this antigen when residing inside of human macrophage cells, a new mechanism for antibody-mediated immunity to intracellular bacteria. These results support the development of PNAG as a vaccine for intracellular bacterial pathogens.
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Affiliation(s)
- Colette Cywes-Bentley
- Harvard Medical School, Brigham & Women’s Hospital, Boston, MA, United States of America
| | - Joana N. Rocha
- College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, United States of America
| | - Angela I. Bordin
- College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, United States of America
| | - Mariana Vinacur
- Harvard Medical School, Brigham & Women’s Hospital, Boston, MA, United States of America
| | - Safia Rehman
- Harvard Medical School, Brigham & Women’s Hospital, Boston, MA, United States of America
| | - Tanweer S. Zaidi
- Harvard Medical School, Brigham & Women’s Hospital, Boston, MA, United States of America
| | - Mark Meyer
- Mg Biologics, Ames, IA, United States of America
| | | | | | | | - Steeve Giguère
- College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
| | - Noah D. Cohen
- College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, United States of America
- * E-mail: (NDC); (GBP)
| | - Gerald B. Pier
- Harvard Medical School, Brigham & Women’s Hospital, Boston, MA, United States of America
- * E-mail: (NDC); (GBP)
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Hamza E, Mirkovitch J, Steinbach F, Marti E. Regulatory T cells in early life: comparative study of CD4+CD25high T cells from foals and adult horses. PLoS One 2015; 10:e0120661. [PMID: 25790481 PMCID: PMC4366079 DOI: 10.1371/journal.pone.0120661] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 01/25/2015] [Indexed: 11/28/2022] Open
Abstract
The immune system of mammals is subject to continuous development during the postnatal phase of life. Studies following the longitudinal development of the immune system in healthy children are limited both by ethical considerations and sample volumes. Horses represent a particular valuable large animal model for T regulatory (Treg) cells and allergy research. We have recently characterised Treg cells from horses, demonstrated their regulatory capability and showed both their expansion and induction in vitro. Insect bite hypersensitivity (IBH) is a common allergy in horses resembling atopic dermatitis and studies have shown that first exposure to allergens in adult life results in an increased incidence of IBH. The aim of the present study was to characterize circulating CD4+CD25highFoxP3+cells in foals, evaluate their suppressive capability and their in vitro induction compared to adult horses. 19 foals (age range, 1–5 months), their adult mothers and six one-year-old horses (yearlings) were included in the study. The proportion of FoxP3+ cells within the circulating CD4+CD25high population was significantly higher in foals (47%) compared to their mothers (18%) and to yearlings (26%). Treg cells from foals also displayed a higher suppressive capability. Furthermore, CD4+CD25high cells in foals could be induced in vitro from CD4+CD25− cells in a significantly higher proportion compared to mares. These cells also displayed a significantly enhanced suppressive capability. In summary these findings support the notion that exposure of horses to allergens during maturation of the immune system assists the establishment of induced (i)Treg driven tolerance.
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Affiliation(s)
- Eman Hamza
- Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- * E-mail:
| | - Jelena Mirkovitch
- Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Falko Steinbach
- School of Veterinary Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Eliane Marti
- Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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Sanz MG, Villarino N, Ferreira-Oliveira A, Horohov DW. VapA-specific IgG and IgG subclasses responses after natural infection and experimental challenge of foals with Rhodococcus equi. Vet Immunol Immunopathol 2015; 164:10-5. [PMID: 25681111 DOI: 10.1016/j.vetimm.2015.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 12/11/2014] [Accepted: 01/09/2015] [Indexed: 10/24/2022]
Abstract
Rhodococcus equi is a common cause of pneumonia in young foals worldwide and has considerable economic effects on the global equine industry. Despite ongoing efforts, no vaccine is currently available to prevent rhodococaal pneumonia. This is due, in part, to an incomplete understanding of the protective immune response to this bacterium. While antibodies to VapA, a lipoprotein produced by virulent R. equi, are useful in differentiating antibody production in response to pathogenic versus non-pathogenic strains, the significance of the humoral response of foals to this lipoprotein remains poorly defined. The objectives of this study were to evaluate changes in VapA-specific IgG and IgG subclasses after exposure and infection of neonatal foals. Experimental foals included those challenged with R. equi at 1 (n=18), 2 (n=4) and 3 (n=6) weeks of age. Confirmed naturally infected (n=7) and not infected (n=3) foals were also included. All foals were bled 24h after birth and weekly thereafter for a period of 8 weeks. Antibody changes over time were evaluated. Following birth, VapA-specific IgGs significantly (p<0.05) decreased over time in all foals as a result of normal decay of passively transferred antibodies. Both VapA-specific IgGa and IgG(T) significantly increased (p<0.05) after experimental challenge, however, the rise in IgG(T) occurred earlier. Only a significant (p<0.05) increase in VapA-specific IgG(T) over time was seen after natural infection. Whether VapA-specific IgG(T) can be used to differentiate rhodococcal from other pneumonias requires further investigation under field conditions.
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Affiliation(s)
- M G Sanz
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, Kentucky,Lexington, KY 40546-009, United States
| | - N Villarino
- Washington State University, College of Veterinary Medicine, Pullman, WA 99164-6610, United States
| | - A Ferreira-Oliveira
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, Kentucky,Lexington, KY 40546-009, United States
| | - D W Horohov
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, Kentucky,Lexington, KY 40546-009, United States.
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Giles C, Vanniasinkam T, Ndi S, Barton MD. Rhodococcus equi (Prescottella equi)vaccines; the future of vaccine development. Equine Vet J 2014; 47:510-8. [DOI: 10.1111/evj.12310] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 06/12/2014] [Indexed: 12/29/2022]
Affiliation(s)
- C. Giles
- School of Pharmacy and Medical Sciences; University of South Australia; Adelaide Australia
| | - T. Vanniasinkam
- School of Biomedical Sciences; Charles Sturt University; Wagga Wagga New South Wales Australia
| | - S. Ndi
- School of Pharmacy and Medical Sciences; University of South Australia; Adelaide Australia
| | - M. D. Barton
- School of Pharmacy and Medical Sciences; University of South Australia; Adelaide Australia
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Cauchard S, Giguère S, Venner M, Muscatello G, Cauchard J, Cohen ND, Haas A, Hines SA, Hondalus MK, Horohov DW, Meijer WG, Prescott JF, Vázquez-Boland J. Rhodococcus equi research 2008-2012: report of the Fifth International Havemeyer Workshop. Equine Vet J 2014; 45:523-6. [PMID: 23909447 DOI: 10.1111/evj.12103] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Sanz M, Loynachan A, Sun L, Oliveira A, Breheny P, Horohov DW. The effect of bacterial dose and foal age at challenge on Rhodococcus equi infection. Vet Microbiol 2013; 167:623-31. [PMID: 24139178 DOI: 10.1016/j.vetmic.2013.09.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/11/2013] [Accepted: 09/13/2013] [Indexed: 10/26/2022]
Abstract
While Rhodococcus equi remains the most common cause of subacute or chronic granulomatous bronchopneumonia in foals, development of a relevant model to study R. equi infection has proven difficult. The objective of this study was to identify a challenge dose of R. equi that resulted in slow progressive disease, spontaneous regression of lung lesions and age-dependent susceptibility. Foals less than one-week of age were challenged intratracheally using either 10(6), 10(5), 10(4), 10(3) or 10(2) cfu of R. equi. Two doses (10(3) cfu and 10(5) cfu) were used to challenge 2 and 3-week-old, and 3 and 6-week-old foals, respectively. Physical examination, thoracic ultrasound and blood work were performed. Foals were euthanized at the end of the study or when clinical signs of pneumonia developed. All foals were necropsied and their lung lesions scored. Foals challenged with low concentrations of R. equi developed slow progressive pneumonia and approximately 50% of the foals recovered spontaneously. Likewise, macroscopic (>1cm diameter) pyogranulomatous lesions were only observed when low doses of R. equi were used. Clinical pneumonia was not seen after low dose challenge in the 3-week-old foals or in the 6-week-old foals. This study demonstrates that the use of low doses of R. equi to challenge neonatal foals provides an improved model for studying this disease. Furthermore, susceptibility to R. equi infection was shown to diminish early in the foal's life, as has been reported in the field.
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Affiliation(s)
- M Sanz
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546-0099, United States
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Vázquez-Boland JA, Giguère S, Hapeshi A, MacArthur I, Anastasi E, Valero-Rello A. Rhodococcus equi: the many facets of a pathogenic actinomycete. Vet Microbiol 2013; 167:9-33. [PMID: 23993705 DOI: 10.1016/j.vetmic.2013.06.016] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 06/27/2013] [Indexed: 12/20/2022]
Abstract
Rhodococcus equi is a soil-dwelling pathogenic actinomycete that causes pulmonary and extrapulmonary pyogranulomatous infections in a variety of animal species and people. Young foals are particularly susceptible and develop a life-threatening pneumonic disease that is endemic at many horse-breeding farms worldwide. R. equi is a facultative intracellular parasite of macrophages that replicates within a modified phagocytic vacuole. Its pathogenicity depends on a virulence plasmid that promotes intracellular survival by preventing phagosome-lysosome fusion. Species-specific tropism of R. equi for horses, pigs and cattle appears to be determined by host-adapted virulence plasmid types. Molecular epidemiological studies of these plasmids suggest that human R. equi infection is zoonotic. Analysis of the recently determined R. equi genome sequence has identified additional virulence determinants on the bacterial chromosome. This review summarizes our current understanding of the clinical aspects, biology, pathogenesis and immunity of this fascinating microbe with plasmid-governed infectivity.
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Affiliation(s)
- José A Vázquez-Boland
- Microbial Pathogenesis Unit, School of Biomedical Sciences and Edinburgh Infectious Diseases, University of Edinburgh, Edinburgh EH9 3JT, UK; Grupo de Patogenómica Bacteriana, Facultad de Veterinaria, Universidad de León, 24071 León, Spain.
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Rhodococcus equi pneumonia in the foal--part 1: pathogenesis and epidemiology. Vet J 2011; 192:20-6. [PMID: 22015138 DOI: 10.1016/j.tvjl.2011.08.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 06/20/2011] [Accepted: 08/12/2011] [Indexed: 10/16/2022]
Abstract
Rhodococcus equi pneumonia is a worldwide infectious disease of major concern to the equine breeding industry. The disease typically manifests in foals as pyogranulomatous bronchopneumonia, resulting in significant morbidity and mortality. Inhalation of aerosolised virulent R. equi from the environment and intracellular replication within alveolar macrophages are essential components of the pathogenesis of R. equi pneumonia in the foal. Recently documented evidence of airborne transmission between foals indicates the potential for an alternative contagious route of disease transmission. In the first of this two-part review, the complexity of the host, pathogen and environmental interactions that underpin R. equi pneumonia will be discussed through an exploration of current understanding of the epidemiology and pathogenesis of R. equi pneumonia in the foal.
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Equine neonates have attenuated humoral and cell-mediated immune responses to a killed adjuvanted vaccine compared to adult horses. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2010; 17:1896-902. [PMID: 20943883 DOI: 10.1128/cvi.00328-10] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The objectives of this study were to compare relative vaccine-specific serum immunoglobulin concentrations, vaccine-specific lymphoproliferative responses, and cytokine profiles of proliferating lymphocytes between 3-day-old foals, 3-month-old foals, and adult horses after vaccination with a killed adjuvanted vaccine. Horses were vaccinated intramuscularly twice at 3-week intervals with a vaccine containing antigens from bovine viral respiratory pathogens to avoid interference from maternal antibody. Both groups of foals and adult horses responded to the vaccine with a significant increase in vaccine-specific IgGa and IgG(T) concentrations. In contrast, only adult horses and 3-month-old foals mounted significant vaccine-specific total IgG, IgGb, and IgM responses. Vaccine-specific concentrations of IgM and IgG(T) were significantly different between all groups, with the highest concentrations occurring in adult horses, followed by 3-month-old foals and, finally, 3-day-old foals. Only the adult horses mounted significant vaccine-specific lymphoproliferative responses. Baseline gamma interferon (IFN-γ) and interleukin-4 (IL-4) concentrations were significantly lower in 3-day-old foals than in adult horses. Vaccination resulted in a significant decrease in IFN-γ concentrations in adult horses and a significant decrease in IL-4 concentrations in 3-day-old foals. After vaccination, the ratio of IFN-γ/IL-4 in both groups of foals was significantly higher than that in adult horses. The results of this study indicate that the humoral and lymphoproliferative immune responses to this killed adjuvanted vaccine are modest in newborn foals. Although immune responses improve with age, 3-month-old foals do not respond with the same magnitude as adult horses.
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