Immunization with plasmid DNA encoding antigenic proteins elicits both antibody and cell-mediated immune responses. This method of producing the protein antigens of interest directly in host cells can provide appropriate tertiary structure for the induction of conformationally specific antibodies, and also facilitates the induction of cellular immune responses. DNA immunization has provided effective protective immunity in various animal models. The immune responses induced by DNA vaccines may in some instances be preferable to those produced by immunization using conventional methods. DNA vaccination appears to be applicable to a variety of pathogens and is a useful method of raising immune responses. Thus this approach to vaccination has the potential to be a successful method of rapidly screening for antigens capable of inducing protective immunity, and of inducing protective immunity against pathogens of clinical importance.