Equine herpesvirus 1 is causing respiratory, reproductive and neurological disorders, resulting in financial losses in horse industry. In Belgium, only inactivated vaccines are available which only partially protects horses. As an infection with wild type virus is establishing a full protection for 6 months, an intranasal vaccination will give the best prevention. Two intranasal attenuated EHV-1 viruses have been developed in the promoter’s lab based on new pathogenesis insights. One is genetically gD deleted but phenotypically gD complemented (EHV1 gD-/+). A second one is making a soluble gD (EHV1 gDs/+), which will induce more neutralising antibodies. EHV1 gD-/+ infects epithelial cells and spreads cell-associated, making small plaques; newly produced virus (EHV1 gD-/-) is not infectious. In the project, the vaccine candidates will be tested in vitro (replication kinetics in nasal mucosa explants, primary respiratory epithelial cells and monocytes/T-lymphocytes; analysis of absence of viral transmission from infected leukocytes to endothelial cells) and in vivo (safety and efficacy; intranasal vaccination with the most suitable candidate and challenge 4 weeks later). Next, a foreign gene (HA of equine influenza virus) will be introduced in the gG gene of the candidate vaccine and the vector function will be tested in vitro and in vivo. For the latter, only the safety and immunogenicity will be tested (induction of neutralising antibodies against EHV-1 and EIV).