Impact of ETIF Deletion on Safety and Immunogenicity of Equine Herpesvirus Type 1-Vectored Vaccines

Abstract

Heterologous gene transfer by viral vector systems is often limited by factors such as preexisting immunity, toxicity, low packaging capacity, or weak immunogenic potential. A novel viral vector system derived from equine herpesvirus type 1 (EHV-1) not only overcomes some of these obstacles but also promotes the robust expression of a delivered transgene and the induction of antigen-specific immune responses. Regarding an enhanced safety profile, we assessed the impact of the gene encoding the sole essential tegument protein, ETIF, on the replication and immunogenicity of recombinant EHVs. The deletion of ETIF severely attenuates replication in permissive RK13 cells and a human lung epithelial cell line but without influencing transgene expression. Whereas the intranasal administration of a recombinant luciferase EHV in BALB/c mice resulted in transgene expression in nasal cavities and lungs for 5 to 6 days, the ETIF deletion limited expression to 2 days and resulted in 30-fold-less luminescence. Attenuated replication was accompanied by a decreased capacity to induce CD8 ؉ T cells against a delivered HIV Gag transgene in BALB/c mice following repeated intranasal application. However, a single subcutaneous immunization with a gag DNA vaccine primed specific T cells for substantial expansion by two subsequent intranasal booster immunizations with either the gag recombinant ETIF mutant or the parental virus. In addition to inducing Gag-specific serum antibodies, this prime-boost strategy clearly outperformed three sequential immunizations with the parental or EHV-⌬ETIF virus or repeated DNA vaccination by inducing substantial specific secretory IgA (sIgA) titers.

Similar regulation of two distinct UL24 promoters by regulatory proteins of equine herpesvirus type 1 (EHV‐1)

“…Rabbit kidney cells (RK13) were purchased from the American Type Culture Collection (ATCC) and cultured them in Dulbecco's modified Eagle's medium supplemented with 10% foetal bovine serum (FBS), 100 units/ml penicillin and 100 μg/ml streptomycin at 37 °C with 5% CO 2 . The 438/77 strain of EHV‐1 were obtained from ATCC and propagated in the RK13 cells and performed the plaque assays to titre EHV‐1 as previously described [39].…”

Effects of Different Anesthetics in the Murine Model of EHV-1 Infection

“…However, because of the irritant properties to mucous membranes, especially those of the respiratory tract, and the significant risk of fire or explosion, this popular anesthetic was replaced by ketamine/xylazine 13 or by isoflurane. 14 Several studies have suggested that anesthetics may alter tissue homeostasis. 5,9,25 So far, the possible effects of such anesthetics on EHV-1 infection have not been investigated.…”