SPECIFIC KILLING OF HIV-INFECTED LYMPHOCYTES BY A RECOMBINANT IMMUNOTOXIN DIRECTED AGAINST THE HIV-1 ENVELOPE GLYCOPROTEIN

Background: 3B3 is a high-affinity anti-gp120 antibody that neutralize s a wide range of primary and laboratory isolates of HIV-1. The parent al antibody was isolated from a combinatorial phage display library co nstructed from bone marrow RNA of an HIV-infected individual. We have generated a highly active immunotoxin using the 3B3 single-chain Fv (s cFv) which can specifically kill lymphocytes infected by HIV-1. Materi als and Methods: We used recombinant DNA technology to clone the Fv fr agment of 3B3 and produce a single-chain Fv (scFv). 3B3 scFv was then fused to a truncated version of Pseudomonas exotoxin A (PE38), giving rise to a recombinant immunotoxin 3B3(Fv)PE38 that was expressed in E, coli and purified to near homogeneity. Results: 3B3(Fv)-PE38 binds wi th the same affinity as the parental Fab antibody to the MN strain of gp120. The immunotoxin specifically kills a gp120-expressing transfect ed cell line and a chronically HN-infected lymphocytic cell line. The immunotoxin is very stable at 37 degrees C, retaining 80% of its origi nal activity after 24 hr. Conclusions: Potent immunotoxins such as 3B3 (Fv)PE38 could be utilized in combination with multidrug cocktails tha t limit viral replication to help reduce viral reservoirs in patients with AIDS.