Antibody-inducing properties of a prototype bivalent herpes simplex virus/enterotoxigenic Escherichia coli DNA vaccine.

The antibody-inducing properties of a bacterial/viral bivalent DNA vaccine (pRECFA), expressing a peptide composed of N- and C-terminal amino acid sequences of the herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) fused with an inner segment encoding the major structural subunit of enterotoxigenic Escherichia coli (ETEC) CFA/I fimbriae (CFA/I), was evaluated in BALB/c mice following intramuscular immunization. The bivalent pRECFA vaccine elicited serum antibody responses, belonging mainly to the IgG2a subclass, against both CFA/I and HSV gD proteins. pRECFA-elicited antibody responses cross-reacted with homologous and heterologous ETEC fimbrial antigens as well as with type 1 and type 2 HSV gD proteins, which could bind and inactivate intact HSV-2 particles. On the other hand, CFA/I-specific antibodies could bind but did not neutralize the adhesive functions of the bacterial CFA/I fimbriae. In spite of the functional restriction of the antibodies targeting the bacterial antigen, the present evidence suggests that fusion of heterologous peptides to the HSV gD protein represents an alternative for the design of bivalent DNA vaccines able to elicit serum antibody responses.