Abstract
Purpose::
Protease IV (PIV) has been established in two animal models as a corneal virulence factor of Pseudomonas aeruginosa. Injection of this protease into animals has yielded little or no antibody. This study is a new effort to produce a potent antibody response to PIV.
Methods::
PIV from P. aeruginosa PA103-29 and recombinant PIV (rPIV) were purified for immunization. Antibody of low titer was incubated with 50 or 100 µg of rPIV to form antigen-antibody complexes (Ag-Ab). PIV alone or Ag-Ab complexes were injected intravenously into SPF rabbits (n = 3) from which pre-immunization sera had been obtained. For a control, rabbits were injected with normal rabbit sera. Three weeks after immunization, rabbits were bled and sera were tested for antibodies to PIV using ELISA and Western blot techniques. Immunization boosts were administered 2 days after each bleed for a total of 4 immunizations.
Results::
Pre-bleed rabbit sera and the sera of rabbits injected with normal sera had a low average ELISA titer to PIV (< 1.6 ± 0.46 [log10]) and produced no reaction with PIV on Western blot. Upon primary immunization with PIV alone, the average antibody titer was 1.80 ± 0.10 and after four immunizations the titer was 2.03 ± 0.03. In contrast, the titer following one immunization with the Ag-Ab complexes was 2.51 ± 0.51 and after four immunizations, the antibody titer rose to 4.90 ± 0.11. Sera from rabbits immunized with PIV failed to produce bands on Western blots, whereas sera of rabbits immunized two to four times with Ag-Ab complexes produced bands on Western blots, even when diluted > 1 : 500.
Conclusions::
The use of antibody:antigen complexes strongly favored the development of a potent antibody response to protease IV.
Keywords: Pseudomonas • immunomodulation/immunoregulation • keratitis