[Immunologic properties of coli surface antigen 6(CS6) of enterotoxigenic Escherichia coli and cholera toxin subunit B expressed in Shigella flexneri 2a strain T32].

A host-plasmid balancing system composed with a delta asd mutant (FaD) of an avirulent strain (T32) of Shigella flexneri 2a and plasmid harboring asd gene was used to express enterotoxigenic E. coli surface antigen 6(CS6) and V. cholerae toxin subunit B (CTB). The results of Western blotting and ELISA showed that all of recombinant plasmids (pYX201, pYX202 and pYX203) could be maintained stably and expressed CS6 and CTB respectively in T32 without any antibiotic selection. All the recombinant bacterial strains could elicit the corresponding antibodies in rabbits. The antibodies against CTB elicited by both FaD/pYX201 and FaD/pYX203 showed to be high level, and had long prolongation time, in otherwise, the antibodies against CS6 showed to be low level, indicating that higher expression level of foreign antigen may be benefit for construction of genetic multivalent vaccine.

Progressive subluxation and polyethylene wear in total knee replacements with flat articular surfaces.

One hundred eighty-six Microloc tricompartmental, cruciate-sparing, primary total knee replacements in 136 patients were performed between 1983 and 1987. Femoral components were made of cobalt-chrome-molybdenum alloy. The tibial component baseplates were made of titanium-aluminum-vanadium alloy. The baseplates were made with three small porous-coated pegs for fixation with or without cement, or with a central stem for fixation with cement. The polyethylene was affixed to the baseplate by a mechanical locking mechanism that was nonmodular. The articular surfaces of both components were flat mediolaterally and anteroposteriorly. The patellar components were dome shaped and metal backed with titanium-aluminum alloy. Seventy-three percent of the femoral components, 26% of the tibial components, and 48% of the patellar components were inserted without bone cement. The average time to maximum follow-up examination was 6.1 years (range, four to nine years). Of implants that had not been revised, 84.4% had good or excellent results (using the Hospital for Special Surgery scoring system) at final follow-up examination. The average range of motion of functioning implants at final follow-up examination was 108 degrees. Revisions for failure only of the metal-backed patellar component were performed in 22 knees (11.8%). Forty knees (21.5%) required revision for failure of the femoral-tibial articulation. Reasons for failure in this group included: polyethylene wear (57.5%); loosening (15.0%); tibial tray fracture (10.0%); sepsis (12.5%); and dislocation or ligament laxity (5.0%). An additional 15 functioning knees (8.1%) have radiographic evidence of progressive femoral-tibial subluxation. Future failure of these devices is considered likely. Polyethylene wear requiring revision was not statistically associated with patient age, gender, preoperative diagnosis, height, weight, or component size. Polyethylene failure leading to revision was related to the radiographic appearance of femoral-tibial component subluxation. This subluxation was most likely to occur after five years of component implantation. The development of progressive femoral-tibial subluxation was statistically associated with postoperative extremity malalignment, excessive varus positioning of the tibial component, bone grafting of the tibial plateau, the use of the small-pegged tibial component, and the use of this component without cement. Polyethylene wear associated with progressive femoral-tibial subluxation occurred at the periphery of the tibial plateau and along the raised portion of the tibial spine. The metal baseplate at the edge of the plateau was frequently exposed and worn. Bone lysis associated with the presence of polyethylene, metal, and cement debris was frequently observed.