Safety, efficacy, and immunogenicity of a modified-live equine influenza virus vaccine in ponies after induction of exercise-induced immunosuppression.
OBJECTIVE
To determine safety, efficacy, and immunogenicity of an intranasal cold-adapted modified-live equine influenza virus vaccine administered to ponies following induction of exercise-induced immunosuppression.


METHODS
Prospective study.


METHODS
Fifteen 9- to 15-month old ponies that had not had influenza.


METHODS
Five ponies were vaccinated after 5 days of strenuous exercise on a high-speed treadmill, 5 were vaccinated without undergoing exercise, and 5 were not vaccinated or exercised and served as controls. Three months later, all ponies were challenged by nebulization of homologous equine influenza virus. Clinical and hematologic responses and viral shedding were monitored, and serum and nasal secretions were collected for determination of influenza-virus-specific antibody isotype responses.


RESULTS
Exercise caused immunosuppression, as indicated by depression of lymphocyte proliferation in response to pokeweed mitogen. Vaccination did not result in adverse clinical effects, and none of the vaccinated ponies developed clinical signs of infection following challenge exposure. In contrast, challenge exposure caused marked clinical signs of respiratory tract disease in 4 control ponies. Vaccinated and control ponies shed virus after challenge exposure. Antibody responses to vaccination were restricted to serum IgGa and IgGb responses in both vaccination groups. After challenge exposure, ponies in all groups generated serum IgGa and IgGb and nasal IgA responses. Patterns of serum hemagglutination inhibition titers were similar to patterns of IgGa and IgGb responses.


CONCLUSIONS
Results suggested that administration of this MLV vaccine to ponies with exercise-induced immunosuppression was safe and that administration of a single dose to ponies provided clinical protection 3 months later.
Lunn
D P
DP
Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison 53706, USA.
Hussey
S
S
Sebing
R
R
Rushlow
K E
KE
Radecki
S V
SV
Whitaker-Dowling
P
P
Youngner
J S
JS
Chambers
T M
TM
Holland
R E
RE
Horohov
D W
DW
D000281:Administration, Intranasal; D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis; D006385:Hemagglutination Inhibition Tests / Q000662:veterinary; D006734:Horse Diseases / Q000276:immunology* / Q000517:prevention & control; D006736:Horses; D007108:Immune Tolerance / Q000276:immunology*; D007070:Immunoglobulin A / Q000096:biosynthesis; D007074:Immunoglobulin G / Q000096:biosynthesis; D007165:Immunosuppression Therapy / Q000662:veterinary; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology / Q000592:standards*; D008213:Lymphocyte Activation / Q000276:immunology; D009330:Nebulizers and Vaporizers / Q000662:veterinary; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D005082:Physical Exertion / Q000502:physiology*; D011446:Prospective Studies; D012449:Safety; D013997:Time Factors; D016896:Treatment Outcome; D014611:Vaccination / Q000662:veterinary; D014613:Vaccines, Attenuated / Q000276:immunology / Q000592:standards; D017201:Virus Shedding
D000914:Antibodies, Viral; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated