Co-immunization with an HIV-1 Tat transduction peptide-rotavirus enterotoxin fusion protein stimulates a Th1 mucosal immune response in mice

The cholera toxin B subunit (CTB) and a 12 aa HIV-1 Tat transduction peptide were genetically linked to a 90 aa peptide from the murine rotavirus non-structural enterotoxin protein (NSP4) for comparison of receptor directed and transduction peptide mediated antigen targeting to the gut associated lymphoid tissues for enhanced protection against rotavirus infection. Oral immunization with Tat-NSP4₉₀ fusion protein isolated from Escherichia coli generated detectable anti-NSP4₉₀ IgG titers in mice. CTB-NSP4₉₀ fusion protein stimulated higher serum IgG titers than CTB fused to a 22 aa immunodominant epitope NSP4₂₂ indicating the presence of additional immunogenic epitopes in the NSP4₉₀ peptide. Mice immunized with CTB-NSP4₂₂ stimulated high IgG2a antibody levels suggesting a dominant Th1 lymphocyte response. However, mice immunized with CTB-NSP4₉₀ generated similar levels of IgG1 and IgG2a suggesting equal stimulation of Th1 and Th2 responses. Mice co-immunized with CTB-NSP4 ₉₀ and Tat-NSP4₉₀ fusion proteins generated dominant IgG2a levels indicating that the two ligands co-operate to generate an increased Th1 response.