Design of microencapsulated immunoglobulins and peptide antigens for the prevention of human rotavirus infection

Human rotavirus (HRV) is the major causative agent of acute gastroenteritis in children, causing as many as 600 000 deaths annually. HRV vaccines have demonstrated variable efficacy, suggesting the need for alternatives to current vaccine strategies. Orally administered pathogen-specific antibodies present an attractive approach to establish local protective immunity against rotavirus. However, in order for orally administered antibodies to be effective, they must resist degradation in the stomach, and reach the small intestine, the site of viral replication, with their biological activity intact. The goal of this work was to investigate the use of peptide antigen constructs to induce specific HRV-neutralizing antibodies, and to establish an effective microencapsulation method to protect the HRV-neutralizing antibodies from gastrointestinal inactivation, in order to allow their use for passive immunization applications.; Peptide antigens containing the amino acid sequence M1ASLIYRQLL 10, a neutralization epitope on the VP8 subunit protein of HRV, were expressed as recombinant fusion proteins with thioredoxin, and examined for their ability to induce specific anti-peptide antibody titres and HRV-neutralizing antibodies. The antigen construct containing three tandem copies of the peptide sequence induced significantly higher anti-peptide antibody titres than all other antigens, including the VP8 protein, as well as high virus-neutralizing titres. These results suggest that M1-L10 epitope may be an important target for the production of specific HRV-neutralizing antibodies for passive immunotherapy applications.; Avian immunoglobulin (Ig) Y was previously examined as a source of HRV-neutralizing antibodies for passive immunization applications. An effective microencapsulation method would allow delivery and sustained slow release of intact IgY to the small intestine, where it could bind and neutralize the virus. A 35% (w/w) coating of a pH sensitive methacrylic acid-ethyl acrylate polymer was found to protect IgY from degradation in vitro, maintaining greater than 95% activity after 6 hours in simulated gastric fluid. The IgY was slowly released from the microencapsulated granules upon exposure to simulated intestinal fluid, and retained 80% activity after 8 hours exposure to pancreatic enzymes. In vivo, the encapsulated IgY retained significantly more activity than non-encapsulated IgY, indicating that microencapsulation may provide an effective means of protecting antibodies from gastric inactivation, allowing their use for the passive immunization against enteric pathogens such as HRV.