Gene gun-mediated DNA immunization primes development of mucosal immunity against bovine herpesvirus 1 in cattle

Vaccination by a mucosal route is an excellent approach to the control of m ucosally acquired infections. Several reports on rodents suggest that DNA v accines can be used to achieve mucosal immunity when applied to mucosal tis sues. However, with the exception of one study with pigs and another with h orses, there is no information on mucosal DNA immunization of the natural h ost. In this study, the potential of inducing mucosal immunity in cattle by immunization with a DNA vaccine was demonstrated. Cattle were immunized wi th a plasmid encoding bovine herpesvirus 1 (BHV-1) glycoprotein B, which wa s delivered with a gene gun either intradermally or intravulvomucosally. In travulvomucosal DNA immunization induced strong cellular immune responses a nd primed humoral immune responses. This was evident after BHV-1 challenge when high levels of both immunoglobulin G (IgG) and IgA were detected. Intr adermal delivery resulted in lower levels of immunity than mucosal immuniza tion. To determine whether the differences between the immune responses ind uced by intravulvomucosal and intradermal immunizations might be due to tbe efficacy of antigen presentation, the distributions of antigen and Langerh ans cells in the skin and mucosa were compared. After intravulvomucosal del ivery, antigen was expressed early and throughout the mucosa, but after int radermal administration, antigen expression occurred later and superficiall y in the skin. Furthermore, Langerhans cells were widely distributed in the mucosal epithelium but found primarily in the basal layers of the epidermi s of the skin. Collectively, these observations may account for the stronge r immune response induced by mucosal administration.