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 neutralizes a wide range of primary and laboratory isolates of HIV-1. The parental antibody was isolated from a combinatorial phage display library constructed from bone marrow RNA of an HIV-infected individual. We have generated a highly active immunotoxin using the 3B3 single-chain Fv (scFv) which can specifically kill lymphocytes infected by HIV-1.


METHODS
We used recombinant DNA technology to clone the Fv fragment 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 with the same affinity as the parental Fab antibody to the MN strain of gp120. The immunotoxin specifically kills a gp120-expressing transfected cell line and a chronically HIV-infected lymphocytic cell line. The immunotoxin is very stable at 37 degrees C, retaining 80% of its original activity after 24 hr.


CONCLUSIONS
Potent immunotoxins such as 3B3(Fv)-PE38 could be utilized in combination with multidrug cocktails that limit viral replication to help reduce viral reservoirs in patients with AIDS.
Bera
T K
TK
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
Kennedy
P E
PE
Berger
E A
EA
Barbas
C F
CF
Pastan
I
I
D019380:Anti-HIV Agents / Q000494:pharmacology*; D000914:Antibodies, Viral / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D015704:CD4 Antigens / Q000378:metabolism; D003429:Cross Reactions; D003602:Cytotoxicity, Immunologic; D015699:HIV Envelope Protein gp120 / Q000276:immunology* / Q000378:metabolism; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000922:Immunotoxins / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology*; D008214:Lymphocytes / Q000187:drug effects* / Q000821:virology*; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology
D019380:Anti-HIV Agents; D000914:Antibodies, Viral; D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D007128:Immunoglobulin Fragments; D000922:Immunotoxins; D011994:Recombinant Proteins; C055966:immunoglobulin Fv