Novel approach for designing rotavirus vaccine candidate based on two plant viruses

Rotavirus А (genus Rotavirus , family Reoviridae ) is still the main cause of viral gastroenteritis in children under 5 years. Existing attenuated vaccines have serious disadvantages, including the risk of potential reversion to pathogenic form, and side effects, the most dangerous of which is intussusception. Moreover, they occurred to be less effective in developing countries, where the most rotavirus-associated deaths are recorded. The development of an effective recombinant rotavirus A vaccine is an actual assignment; herewith the selection of effective and safe adjuvant is the key point for that. Plant viruses are very promising for innovative vaccine designing; they possess high immunostimulating properties, safe for humans and mammals and can serve as a carrier for pathogens’ epitopes. Here we suggest an approach for rotavirus A vaccine development that involves two plant viruses: Alternanthera mosaic virus (AltMV) and Tobacco mosaic virus (TMV) as simultaneously epitope carriers and adjuvants. Spherical particles (SPs) generating by the heating of tobacco mosaic virus were used as an adjuvant and platform for presentation of obtained in our previous study chimeric recombinant protein ER6, which is an AltMV coat protein (CP) fused with the epitope RV14 (RLSFQLMRPPNMTP) of rotavirus A antigen VP6. Epitope RV14 are able to induce protective immune response and is conservative for the majority of rotavirus A strains therefore its usage gives hope to the successful overcoming of one of the main difficulties in rotavirus A vaccine development: wide serological diversity. In present work, effective adsorption of ER6 on the SPs surface leading to the SPs-ER6 complex formation without loss of ER6 antigenic specificity was demonstrated. Two immune antisera with specificity to RV14 epitope within ER6 were obtained. The first serum was obtained via anti-ER6 sera depletion with AltMV CP and recombinant AltMV CP (AltMV rCP), which was expressed in Escherichia coli but did not contain RV14 sequence. The second serum was obtained by a direct immunization with synthetic peptide RLSFQLMRPPNMTP. These sera were utilized for studying RV14 within SPs-ER6 complexes. By means of immunofluorescent microscopy, SPs-ER6 complexes were demonstrated to interact with both depleted serum and anti-RV14 serum. Therefore, rotavirus epitope was confirmed to keep its ability to interact with antibodies within obtained complexes. Considering unique adjuvant properties of spherical particles and characteristics of selected epitope obtained SPs-ER6 complexes can be thought as a promising component for recombinant rotavirus A vaccine. Moreover, it can be hoped that the suggested in present work approach, involving the usage of TMV SPs as a platform and adjuvant for chimeric AltMV CP, containing pathogen’s epitope, will be useful not only for rotavirus A vaccine development but for designing of vaccines against other pathogens of humans or farm animals.