DAB389CD4, a CD4-BASED Immunotoxin is active against HIV in SCID mice model.

Martín-Serrano J¹ , Del Real G², Grau M¹ and Alcamí J¹.

(1) AIDS Immunopathogenesis Unit. Instituto de Salud Carlos III. Madrid; (2) Centro Nacional de Biotecnología. CSIC. Madrid (Spain)

Background: DAB389CD4 is a fusion protein in which the receptor binding domain of diphteria toxin has been replaced by the D1 and D2 domains of human CD4 which contain the gp120 binding site. We have previously shown that this immunotoxin presents a strong antiviral activity against wild type viruses and selectively eliminates infected lymphocytes from HIV patients in culture. The aim of this work was to evaluate the antiviral activity of the DAB389CD4 immunotoxin “in vivo” using the hu-SCID mice model. Material and Methods: BalB/cByJ-SCID were reconstituted with 10⁷ peripheral blood mononuclear cells (PBMC) from HIV-infected patients. In the treated group, four doses of the immunotoxin (1mg/kg) were administered by intravenous route at 24, 48, 72 and 96 hours after cell inoculation. Viral replication was analyzed measuring viral load in plasma by RT-PCR at one and two weeks after infection. Two weeks after infection, mononuclear cells were obtained by peritoneal washing and HIV isolation was performed. To this aim, 10⁶ cells were activated with PHA and IL2 for two weeks and p24 HIV antigen production was measured in culture supernatants. Results: No toxic effects were observed in animals treated with the DAB389CD4 toxin. In mice reconstituted with PBMC from four different HIV+ patients (n=39) plasma viral load was detected in 10% of immunotoxin-treated mice as compared to 37% in the untreated group (p=0.05, Fischer´s exact test). Viral isolation was successful in only 10% of immunotoxin-treated mice as compared to 61% of positive cultures obtained in the control group (p=0.003, Yates corrected Chi Square test). Conclusions: Our data show that the immunotoxin DAB389CD4 is active against HIV in a SCID mice model “in vivo”.