Applying biotin-streptavidin binding for iscom (immunostimulating complex) association of recombinant immunogens.
We have previously reported strategies for Escherichia coli production of recombinant immunogens fused to hydrophobic peptide or lipid tags to improve their capacity to be incorporated into an adjuvant formulation. In the present study, we have explored the strong interaction between biotin and SA (streptavidin) (K(D) approximately 10(-15) M) to couple recombinant immunogens to iscoms (immunostimulating complexes). Two different concepts were evaluated. In the first concept, a His(6)-tagged SA fusion protein (His(6)-SA) was bound to Ni(2+)-loaded iscom matrix (iscom without associated protein), and biotinylated immunogens were thereafter associated with the SA-coated iscoms. The immunogens were either biotinylated in vivo on E. coli expression or double biotinylated in vivo and in vitro. In the second concept, the recombinant immunogens were expressed as SA fusion proteins, which were directly bound to a biotinylated iscom matrix. A 53-amino-acid malaria peptide (M5), derived from the central repeat region of the Plasmodium falciparum blood-stage antigen Pf155/RESA, and a 232-amino-acid segment (SRS2') from the central region (from Pro-97 to Lys-328) of the major surface antigen NcSRS2 of the protozoan parasite Neospora caninum, served as model immunogens in the present study. All fusion proteins generated were found to be efficiently expressed and could be recovered to high purity using affinity chromatography. The association between the different immunogen-containing fusion proteins and the corresponding iscom matrix was demonstrated by analytical ultracentrifugation in a sucrose density gradient. However, some fusion proteins were, to a certain extent, also found to associate unspecifically with a regular iscom matrix. Furthermore, selected iscom fractions were demonstrated to induce high-titre antigen-specific antibody responses on immunization of mice. For the particular target immunogen SRS2', the induced antibodies demonstrated reactivity to the native antigen NcSRS2. We believe that the presented concepts offer convenient methods to achieve efficient adjuvant association of recombinant immunogens, and the advantages and disadvantages of the two concepts are discussed.
Wikman
Maria
M
Department of Biotechnology, AlbaNova University Center, Kungl Tekniska Högskolan (KTH), SE-106 91 Stockholm, Sweden.
Friedman
Mikaela
M
Pinitkiatisakul
Sunan
S
Hemphill
Andrew
A
Lövgren-Bengtsson
Karin
K
Lundén
Anna
A
Ståhl
Stefan
S
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D000953:Antigens, Protozoan / Q000276:immunology / Q000378:metabolism; D000954:Antigens, Surface / Q000276:immunology / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D001710:Biotin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D005260:Female; D005818:Genetic Engineering; D007114:Immunization; D051379:Mice; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D014614:Vaccines, Synthetic / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification
D000906:Antibodies; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D001426:Bacterial Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; C115389:SRS2 protein, Neospora caninum; D014614:Vaccines, Synthetic; C066114:biotin-streptavidin complex; C050256:ring-infected erythrocyte surface antigen (RESA), Plasmodium falciparum; D001710:Biotin