Platform for the generation of oral vaccines based on protozoan surface proteins.

The international spread of infectious diseases is a global problem of health security. Vaccination is one of the most successful and profitable health interventions. Oral immunization has significant advantages over the widely used parental vaccines. Intestinal and free-living protozoa express on their surface a dense layer of proteins that protect them from hostile environmental conditions. The use of variable surface proteins (VSPs), such as those of the intestinal protozoan Giardia lamblia, is a feasible mechanism for the generation of oral vaccines, since they are highly immunogenic as well as resistant to changes in pH and proteases. In a recently published article, we showed that these properties of VSPs can be exploited to protect and enhance the immunogenicity of vaccine antigens, thus enabling their oral administration. We recently generated an oral vaccine against influenza virus composed of virus-like particles (VLPs) containing VSPs of G. lamblia and the HA antigen (viral hemagglutinin) in its envelope. When administered orally to mice, these coated particles elicit HA-specific humoral (systemic and local) and cellular responses, without the need of any additional adjuvant. Treated mice are protected against viral challenge as well as against the development of tumors expressing the HA vaccine antigen.