The rotavirus inner
capsid protein VP6 contains conserved
epitopes that are potential targets for eliciting protective immunity against different serotypes within the same group of rotavirus. In order to determine whether VP6 alone can induce protective immunity, an expression vector pcDNA1/EDIM6 containing gene 6 of rotavirus
EDIM strain was constructed and used as a
vaccine in an adult mouse model. Cloned gene 6 was determined to be 1356
nucleotides long and contained a 5' noncoding region of 23
nucleotides, a 3' noncoding region of 139
nucleotides, and a coding frame of 1194
nucleotides for a
polypeptide of 397
amino acid residues. Recombinant VP6 was expressed in rabbit reticulocyte lysate and the heat-denatured recombinant VP6 migrated in SDS-
gels with an apparent molecular weight of approximately 43 kDa. Five additional
polypeptide bands corresponding to oligomers of recombinant VP6 were observed when the expressed product was not heat denatured. To determine the immunogenicity of recombinant VP6, female BALB/c mice were injected intramuscularly or intradermally with pcDNA1/EDIM6, or were inoculated epidermally with plasmid-coated
gold beads using the Geniva Accell particle delivery device. Only
intradermal injection and particle delivery elicited measurable serum anti-rotavirus
IgG responses, but responses developed following particle delivery were significantly (P < 0.001) greater. However, none of the delivery methods induced serum or stool anti-rotavirus
IgA responses and, when challenged with
EDIM no protection against
infection was observed in the immunized mice. Therefore, parenteral immunization with VP6 alone elicited large anti-rotavirus
IgG responses but did not elicit protection against murine
rotavirus infection in this model.