Cytotoxic T-Lymphocyte Activity Specific for Hemagglutinin (H) Protein of Canine Distemper Virus in Dogs.

Abstract

ABSTRACT. Cytotoxic T-lymphocyte (CTL) responses to hemagglutinin (H) protein of canine distemper virus (CDV) were evaluated in dogs using the replication-deficient adenovirus protein expression system. Skin fibroblasts were isolated from two dogs and were infected with recombinant adenovirus bearing the CDV-H gene (Ade-CDVH). CTL assay was performed using fibroblasts expressing CDV-H protein as target cells and peripheral blood lymphocytes (PBL) collected from the same dogs one week after immunization of CDV as effector cells. Specific cytotoxic activity was observed against autologous but not heterologous fibroblasts expressing Canine distemper virus (CDV) belongs to the genus Morbillivirus family Paramyxoviridae and induces fatal diseases including encephalitis with demyelination, diarrhea and respiratory disorders in dogs. CDV infection had been well controlled by vaccination. However, epidemics of CDV infection have been appeared in the last decade even in vaccinated dogs [6,7].Cytotoxic T lymphocytes (CTL) play an important role in the immune system for the clearance and protection against morbilliviruses [3,22]. CTL epitopes and responses to measles virus (MV) infection have been well studied in a mouse model. The major target antigen for CTL in mice was identified as the nucleocapsid (N) protein by several groups, which can induce cross reactive CTL between MV and CDV [1-3, 15, 19]. In addition, it was also reported that H protein of MV [1] and CDV [21] could be one of the CTL epitopes in mice. However, Jaye et al. reported that the fusion (F) and hemagglutinin (H) proteins were important targets for measles CTL responses in humans, a natural host of MV, receiving measles polypetides [11]. On the other hand, CTL responses in infection with another morbillivirus, rinderpest virus (RPV), were also analyzed in mice and cattle, the latter of which is a natural host of RPV. A CTL response against RPV N protein was detected and a CTL epitope within the N protein was identified in the mouse model [13]. However, the role of N protein in protection and induction of CTL responses against RPV infection in cattle was limited [16]. The CTL response against H protein in cattle is more effective and its effect lasts for at least two years [17,20]. These discrepant results suggested that the CTL response in the mouse model does not always reflect that in the natural host, and analyses concerning the development of CTL activity using the virus and the natural host are required.Restriction of the major histocompatibility complex (MHC) in CTL assay makes it difficult to develop an assay system in outbred animals. Recently, an easy method to produce recombinant adenoviruses based on a replicationdeficient adenovirus vector was established, and this method has been shown to be useful for delivery of vectors for gene therapy and protein expression [12,14]. The adenovirus vector possesses useful characteristics such as high level of protein expression, broad host cell range, applicability to non-replicating cells including neu...

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