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A bacteriophage lambda DNA vaccine expressing the small surface antigen (HBsAg) of hepatitis B was compared with Engerix B, a commercially available vaccine based on the homologous recombinant protein (r-HBsAg). Rabbits (five per group) were vaccinated intramuscularly at weeks 0, 5 and 10. Antibody responses against r-HBsAg were measured by indirect enzyme-linked immunosorbent assay, by limiting dilutions and by subtyping. Specific lymphocyte proliferation in vitro was also measured. After one vaccination, three of the five phage-vaccinated rabbits showed a strong antibody response, whereas no r-HBsAg-vaccinated animals responded. Following two vaccinations, all phage-vaccinated animals responded and antibody levels remained high throughout the experiment (220 days total). By 2 weeks after the second vaccination, antibody responses were significantly higher (P

Whole bacteriophage lambda particles, containing reporter genes under the control of the cytomegalovirus promoter (P(CMV)), have been used as delivery vehicles for nucleic acid immunisation. Following intramuscular injection of mice with lambda-gt11 containing the gene for hepatitis B surface antigen (HBsAg), anti-HBsAg responses in excess of 150 mIU ml(-1) were detected. When isolated peritoneal macrophages were incubated with whole lambda particles containing the gene for green fluorescent protein (GFP) under the control of P(CMV), GFP antigen was detected on the macrophage surface 8 h later. Results suggested that direct targeting of antigen-presenting cells by bacteriophage 'vaccines' may occur, leading to enhanced immune responses compared to naked DNA delivery. Bacteriophage DNA vaccines offer several advantages: they do not contain antibiotic resistance genes, they offer a large cloning capacity (approximately 15 kb), the DNA is protected from environmental degradation, they offer the potential for oral delivery, and large-scale production is cheap, easy and extremely rapid.