Characterization of recombinant polioviruses expressing regions of rotavirus VP4, hepatitis B surface antigen, and herpes simplex virus type 2 glycoprotein D.

Recombinant polioviruses expressing antigens from rotavirus, herpes simplex virus type 2, and hepatitis B virus were generated. Fusion of the heterologous polypeptides to the amino terminus of the poliovirus polyprotein did not prevent myristylation of VP0, suggesting a novel mechanism of myristylation for these recombinant viruses. The effects of the parental genetic background, different foreign sequences, and different insertsizesongrowthcharacteristicswerecompared.Boththesizeandthenatureoftheheterologoussequence appeared to be factors influencing the growth and stability of recombinant polioviruses. All of the recombinants showed a temperature-sensitive phenotype, regardless of the genetic background (attenuated or wild type) from which they were derived. Preliminary studies with transgenic mice carrying the poliovirus receptor gene are discussed. Poliovirus is a human enteric pathogen that belongs to the Enterovirus genus of the Picornaviridae family and undergoes extensive multiplication in the human intestinal tract. It has a positive-sense single-stranded RNA genome of approximately 7.5 kb. The viral RNA encodes a single large polyprotein precursor that is cleaved by virus-encoded proteases to give rise to the mature structural and nonstructural proteins (6, 20, 21). The capsid protein precursor, P1, is cotranslationally myristylated and is cleaved into VP0, VP3, and VP1 (21, 30). The final processing step is the autocatalytic cleavage of VP0 into VP2 and VP4, which takes place after RNA encapsidation. A myristate group remains covalently linked to each VP4 molecule and plays an important role in the stability of the virus capsid (3, 4). The use of polioviruses as vectors for the delivery of heterologous antigens to the intestinal mucosa has several advantages. Attenuated strains of poliovirus (Sabin strains) have proven to be very safe and efficacious. The use of these strains as vectors for heterologous antigens provides a system for making combined pediatric vaccines. Oral poliovirus vaccine results in generation of mucosal plus systemic immunity (19), which is advantageous for the generation of protection at the mucosal surface. In previous work, we have characterized Sabin 3 recombinant viruses that carried fragments of the rotavirus outer capsid glycoprotein VP7 gene in two different locations of the poliovirus genome (15, 17). In the present study, we generated recombinant polioviruses carrying genes encoding several different antigens in a variety of poliovirus backgrounds. Characterization of vectors included comparison of the effects of attenuated and wild-type (wt) backgrounds and different poliovirus serotypes (type 3 and type 1) on the growth of recombinantviruses.Thevectorsconstructedinwtbackgroundswere generated with the aim of improving the replication of the recombinant polioviruses in transgenic mice carrying the poliovirus receptor gene (23).