DISPLAY OF A PORA PEPTIDE FROM NEISSERIA-MENINGITIDIS ON THE BACTERIOPHAGE-T4 CAPSID SURFACE

The exterior of bacteriophage T4 capsid is coated with two outer capsi d proteins, Hoc (highly antigenic outer capsid protein; molecular mass , 40 kDa) and Soc (small outer capsid protein; molecular mass, 9 kDa), at symmetrical positions on the icosahedron (160 copies of Hoc and 96 0 copies of Soc per capsid particle). Both these proteins are nonessen tial for phage infectivity and viability and assemble onto the capsid surface after completion of capsid assembly. We developed a phage disp lay system which allowed in-frame fusions of foreign DNA at a unique c loning site in the 5' end of hoc or sec. A DNA fragment corresponding to the 36-amino-acid PorA peptide from Neisseria meningitidis was clon ed into the display vectors to generate fusions at the N terminus of H oc or Sec. The PorA-Hoc and PorA-Soc fusion proteins retained the abil ity to bind to the capsid surface, and the bound peptide was displayed in an accessible form as shown by its reactivity,vith specific monocl onal antibodies in an enzyme-linked immunosorbent assay. By employing T4 genetic strategies, we show that more than one subtype-specific Por A peptide can be displayed on the capsid surface and that the peptide can also be displayed on a DNA-free empty capsid. Both the PorA-Hoc an d PorA-Soc recombinant phages are highly immunogenic in mice and elici t strong antipeptide antibody titers even with a weak adjuvant such as Alhydrogel or no adjuvant at all. The data suggest that the phage T4 hoc-soc system Is an attractive system for display of peptides on an i cosahedral capsid surface and may emerge as a powerful system for cons truction of the next generation multicomponent vaccines.