mediated by anti-recombinant V antigen is dependent on polymorphism of V antigen

mediated by anti-recombinant V antigen is dependent on polymorphism of V antigen. within 3 days. F1-V given s.c. (with adjuvant) protected 33% of the immunized mice, while 88% of the oral F1-V mice survived aerosolized challenge. A comparison of splenic CFU counts showed that there was a 7- to 10-log reduction in the mean bacterial burden in survivors. Taken together, these data indicate that oral booster doses effectively elicit protective immune responses in vivo. In addition, this is the first report VAV2 of a plant-derived oral vaccine that protected animals from live challenge, bringing the likelihood of lower-cost vaccines closer to reality. The establishment of successful protocols for oral vaccination could radically alter the current landscape of infectious diseases. Oral delivery of plant-derived vaccine antigens could eliminate expensive fermentation and purification systems, cold storage and transportation steps, and delivery via sterile needles, significantly reducing costs. Plant-derived oral vaccines have other distinct advantages, including the ability to stimulate both systemic and mucosal immune responses, facilitating large-scale production and simplified storage (eliminating frozen stocks), improving safety due to the lack of human pathogens or microbial toxin contamination, protecting therapeutic proteins by bioencapsulation, and delivering these proteins to the gut-associated lymphoid tissue (7, 15, 80). The engineering of chloroplasts for the production of vaccines and biopharmaceuticals has ushered in a new era in biotechnology (15, 17, 44). Chloroplast transgenes can express large amounts of foreign proteins (up to 46% of the total leaf protein [19]). Transgene silencing does not occur in chloroplasts at the levels of transcription and translation (19, 20). Chloroplasts translate heterologous operons, processed monocistrons, and unprocessed polycistrons (67), enabling the expression of multivalent vaccines. Most important, chloroplast transformation offers transgene containment via maternal inheritance; expression in leaves or vegetative organs eliminates transmission of transgenes in reproductive structures (14, 16). Additional containment methods, such as cytoplasmic male sterility, have also been developed using the chloroplast genome (71). Foreign proteins expressed in chloroplasts are protected in the digestive tract and are efficiently delivered to the circulatory system (52). Plastid transformation of edible crops, including soybean, carrot, and lettuce, has been accomplished recently (22, 45, 49). Moreover, human therapeutic proteins have been stably expressed in lettuce chloroplasts; oral delivery of proinsulin expressed in chloroplasts protected NPI64 nonobese diabetic mice against the development of insulitis (70). These advancements have opened the door for developing vaccine antigens that can be orally administered. Several vaccine antigens have already been expressed in chloroplasts, including the cholera toxin B subunit of (18), protective antigen (47, 87), LecA from (11), the 2L21 peptide from the canine parvovirus (59), and TetC of (83). These antigens were evaluated mostly by using conventional vaccination strategies, i.e., needle-based subcutaneous (s.c.) or intraperitoneal delivery. Therefore, further studies are required to evaluate and understand the mechanism of oral delivery of chloroplast-derived vaccine antigens in plant cells. has caused three plague pandemics and killed approximately 200 million people (62). At least 2,000 cases of plague are reported annually by the World Health Organization (http://www.who.int/mediacentre/factsheets/fs267/en/index.html), including several recent outbreaks in India. The nonavailability of a human plague vaccine is a public health concern, given the potential use of as an agent for bioterrorism NPI64 (42). Since the lungs and respiratory tract are vulnerable to a first exposure to challenges was found to be associated with F1-V-specific IgG1, a TH2-associated antibody. Systemic IgG is a known consequence of parenteral immunization, and many studies have NPI64 demonstrated the efficacy of s.c. and intramuscular vaccines for providing protection against pathogen challenge NPI64 (for a review, see reference 94). However, intranasal or even oral delivery of subunit vaccines may be more effective because of the ability of such vaccines to elicit protective immunity directly at the mucosal surface. Human plague vaccines based on either a live, attenuated strain or.