Mucosal surfaces constitute one of the most important points of entry of infectious agents; protection against infections requires the induction of immune responses at mucosal level . Polysaccharides and LPS from enteric pathogens are considered as some of the most important antigens to induce protection . However, their mucosal administration has proven to be inefficient for the stimulation of the immune system . Mucosal adjuvants can overcome this problem and potentiate their immune responses . Protollin is a complex mix of outer membrane proteins from Neisseria meningitidis B and LPS from Shig uella flexneri (proteosome), this formulation was administered by the i.n route to humans and mice and improved the immune response against LPS antigen [4, 10]. Therefore, we evaluated the effect of coadministration of PLc with Poli Vi by the i.n route.
Results showed that proteoliposomes extracted from V. cholerae O1 (Figure 1A) contain immunogenic and immunostimulatory molecules like OmpU, MSHA and LPS (Fig 1B). Coadministration of PLc with the polysaccharide improves the mucosal and systemic immune response induced vs. Poli Vi (Figure 2) without affecting the immune response vs V. cholerae antigens (results not shown). Purified Poli Vi antigen has been used in the formulation of a parenteral vaccine against typhoid fever  but has never been used by a mucosal route as a with vaccine purposes. Mucosal immunization has been approached by administration by the oral route of the attenuated S. Typhi strain CVD 909 (HolaVax-Typhoid®) expressing the Vi polysaccharide . In these experiments the systemic immune response was superior to that induced by the attenuated S. Typhi strain Ty21a which do not express Poli Vi . Ty21a is also the strain used in the licensed vaccine Vivotif®, against typhoid fever . Specific IgG anti Poli Vi in sera is crucial to avoid pathogen invasion to macrophages and evasion from immunocompetent cells . The role of IgA anti Poli Vi may also be related to the blockade of pathogen invasion at a mucosal level , however the mechanisms of the protection induced by our formulation needs to be evaluated.
The use of mucosal vaccines has many advantages when compared to parenteral administration. Particularly, if vaccine formulations are intended against pathogens that colonize or invade via the mucosal route, like V. cholerae and S. Typhi . Mucosal immunisation offers an attractive two-pronged approach as it stimulates both local and systemic immunity . Furthermore, it also offers the potential for rapid administration in mass vaccination programs  without risk of injury and cross-infection through contaminated needles . In addition, with a growing awareness for environmental impact, disposal of needles, decontamination costs, and incineration waste products has helped to influence development of mucosal vaccines as a greener alternative .
Overall, PLc has been demonstrated to be immunogenic against V. cholerae O1  and also has immune adjuvant effects when coadministered with Poli Vi. PLc is part of the adjuvant family developed by the Finlay Institute, AFPL (Adjuvant Finlay Proteoliposome) and named AFPL2. Further studies are envisaged to evaluate the adjuvant potential of AFPL2 with other antigens and using other mucosal routes like oral to develop a multiple mucosal vaccine candidate against enteric pathogens.