Mucosal and systemic immune responses induced by immunisation of cotton rats with recombinant adenoviruses

by Papp, Zsuzsanna

Replication-defective and replication-competent recombinant human adenovims type 5 vectors efficiently expressed the glycoprotein D (gD) or the transmembrane anchor tnincated gD (ta) of bovine herpesvirus type 1 (BHV-1) in vitro. To facilitate the evaluation of the efficacy of immunisation with these recombinant adenoviruses in conferring protection against BHV-1 infection, a cotton rat (Sigmodonhispidus) model for intranasal BHV-1 challenge was developed. 1 used this model to assess the ability of different routes of immunisation with the recombinant adenoWuses to elicit gD-specific systemic and mucosal bunity and confer protection against BHV-1 challenge. Immunisation with gD-expressing vectors induced better immunity and protection than immunisation with tgD-expressing vinises. Mucosal immunisation with the replicationcompetent virus was more efficient than that with the replication-defective vector in inducing gD-specific antibody in the sem and the respiratory tract. In contrast, systemic immunisation with the two vectors stimulated similar gD-specific antibody levels. These results indicate that the route of immunisation was crucial when assessing the efficacy of recombinant adenovinses as vaccine vectors. The importance of the route of administration was fûrther demonstrated by the finding that intranasal immunisation with the replication-competent vector stimulated higher antigen-specific IgA levels and antibody-secreting ce11 numbers in the respiratory tract than intradermal, intrapentoneal or entenc immunisation. Protection correlated with gD-specific antibody levels such that intranasal immunisation, even 3 months following vaccination, conferreci complete, while intradermal or enteric immunisation conferred partial protection of the lungs of cotton rats dgainst intranasal BHV-1 challenge. Pre-existing active adenovirus-specific imrnunity stimulated by intranasal administration of wild type adenovirus significantly inhibited the development of gD-specific antibody responses and protection against BHV- 1 challenge following immunisation with recombinant adenovinis. In contrast, passive transfer of adenovinis-specificantibody caused ody a slight inhibition. Overail, mucosal and systemic immunisation with adenovhs vecton could induce antigen-specific immunity and protection against BHV-1 challenge. The level of gD-specific immune responses and protection f?om challenge were, however, dependent on the characteristics of the heterologous protein, the replication-capabilityof the vinises, the route of immunisation and the presence or absence of pre-existingadenovim-specific imrnunity in the Cotton rat. I wish to thank Dr. Lome A. Babiuk and Dr. Maria E. Baca Estrada, my supe~sors at the Department of Veterinary Microbiology and the Veteri Infectious Disease Organisation (ViDO), for their advice and support in completion of this thesis. My special thanks go to the members of my graduate committee, Drç. Dale L. Godson, Lou Qualtiere, John A. Ellis, John R. Gordon and Henry Tabel. To Dr. Maria Baca-Estrada I am also grateful for her assistance in my experirnents and her guidance in the field of immunology. 1 appreciate Dr. Dale Gocison's help in my laboratory work, in different everyday tasks and in preparation for academic presentations. 1would like to thank Dr. Dorothy M. Middleton (Department of Veterinary Pathology) for sharing her expertise in pathology and Drs. Suresh K. Mitial, Xiaoping Liang, and Philip .J. Griebel (VIDO) for their theoretical and technicd advice in the fields of virology and immunology. This project could not have been completed without the help of the staff of VIDO, especially Marlene Snider (immunology lab), Barry Carrcd, Trent Watts, Jane Fitzpatrick, Norleen Caddy, Cindy Toy and Linda Boyer (Animal Care Unit). 1also thank Dr. Deborah M. Haines at the Department of Veterinary Microbiology and Kathy Caspell at the Department of Veterinary Pathology for their technical support. The pwified gD and anticonon rat IgA provided by Drs. Sylvia van Dmen Littel-van den Hurk WO) and Brian Underdown (McMaster University) were essential for my work and are very much appreciated. My special thanks go to the graduate students at VIDO, especially Dr. P. Jefiey Lewis, Dr. Sanipa Suradhat and Camilo Raggo, for their advice, technical help and encouragement. Finally, I express my thanks for the financial support fiom the Medical Research Council of Canada, the Naniral Sciences and Engineering Research Council of Canada, the Saskatchewan Department of Agriculture and the Department of Western Econornic Diversification, Govemment of Canada. To cotton rat # 96- 108-VIDO