Manthri S. near-native MSA2 on merozoites was elicited by oral administration. Intestinal antibodies to MSA2 were produced only after oral immunisation. MSA2-specific Th-cell activation could be demonstrated. Based on these results, the immunogenicity in oral immunisations of MSA2, bound non-covalently to non-genetically modifiedL. lactisGEM particles, was compared with MSA2 that was bound covalently to genetically modifiedL. lactis. These two forms elicited similar titres of serum antibodies. The results illustrate the potential of using non-genetically modifiedL. lactisas a safe vaccine delivery vehicle to elicit systemic antibodies, thereby avoiding the dissemination of recombinant DNA into the environment. Keywords:Surface display,Lactococcus lactis, Gram-positive enhancer matrix (GEM) particles,Plasmodium falciparum, Merozoite surface antigen Rabbit Polyclonal to PERM (Cleaved-Val165) 2 (MSA2), Mucosal vaccines == 1. Introduction == Nasal and oral vaccination is preferable to injections from the point of view of safety, ease of administration and compliance. Mucosal vaccines are an alternative to injectable vaccines, because it is e.g. increasingly more difficult to incorporate new injectable vaccines into the existing paediatric vaccination programmes. In addition, mucosally delivered vaccines activate the mucosal immune system to elicit protective secretory IgA antibodies and cellular immunity. This is relevant for protection against viruses, bacteria and parasites that enter the body through mucosal surfaces and cause diseases of the intestinal, respiratory and genital tracts. Oral administration of soluble protein antigens generally leads to systemic tolerance[1]but ingested particulate antigens and microbes in some instances generate mucosal and systemic immune responses[2]through stimulation of the gut-associated lymphoreticular tissue (GALT). Both soluble and particle-associated proteins given intranasally can, through uptake by the nasopharynx-associated lymphoreticular tissue (NALT), elicit local and distal mucosal as well as systemic immune responses[3]. Therefore, oral or nasal immunisation may also be useful against pathogens that enter the body through routes other than mucosa. Attenuated strains of bacterial pathogens such asSalmonella typhi,Mycobacterium bovisandBordetella pertussisare being developed as vectors for mucosal immunisation, but suffer from the disadvantage that they tend to disseminate in the body[3]and can be unsafe in immuno-compromised persons. Lactococcus lactisis ubiquitous in the human environment and in food. It is used for making cheese and buttermilk, and is generally recognized as safe (GRAS).L. lactissurvives passage through the gastrointestinal tract but does not colonise the gut[4]. This lactic acid bacterium may therefore provide a safer alternative to attenuated pathogens for mucosal immunisation purposes[5]. Several bacterial or viral antigens have been expressed inL. lactisfor use in oral and intranasal immunisations[6],[7],[8],[9],[10],[11],[12],[13]. The advantage in relation to the potency of the elicited immune response of anchoring the antigens to the cell wall of the producingL. lactiscells as opposed to intracellular expression has been demonstrated by others[9],[10],[12],[13],[14]. Therefore, we focused in the present study on the cell wall presentation of the antigen. In all previously described ZT-12-037-01 studies on the use ofL. lactisin mucosal immunisation strategies, genetically modified vaccine strains were employed. AlthoughL. lactisis an innocuous bacterium, its widespread use as a genetically modified strain in vaccinations, especially mucosal vaccinations, may cause undesirable shedding of recombinant DNA into the environment with the attendant risk of transfer to other organisms. In order to eliminate this risk we developed a non-genetically modifiedL. lactissupport that allows highly efficient binding of proteins that are fused to a lactococcal peptidoglycan binding domain, the protein anchor (PA). For ZT-12-037-01 this purpose,L. lactiscells are pre-treated with an acid that removes surface components[15], leaving non-living particles that we termed Gram-positive enhancer matrix (GEM)[16],[17]. The pre-treated and neutralized GEM particles are ZT-12-037-01 used to bind the antigen-PA fusion that was produced by another source (in transbinding). In this way, the antigen can be presented to the immune system as a bacterial particle that does not contain the recombinant DNA encoding the antigen. We report here on the immunogenicity after oral delivery ZT-12-037-01 in rabbits of aPlasmodium falciparumparasite antigen presented in two different ways on the surface ofL..