Anti-HIV-1 immunotoxin 3B3(Fv)-PE38: enhanced potency against clinical isolates in human PBMCs and macrophages, and negligible hepatotoxicity in macaques

Kennedy, Paul E.; Bera, Tapan K.; Wang, Qingcheng; Gallo, Maria; Wagner, Wendeline; Lewis, Mark G.; Berger, Edward A.; Pastan, Ira

doi:10.1189/jlb.0306139

Cited by 27 publications

(27 citation statements)

References 55 publications

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“…Many of the animals receiving the ITs had early AIDS, with increasing weight loss, diarrhea, and opportunistic infections, yet most tolerated the ITs well, even at very high doses. These results are consistent with observations in healthy, uninfected macaques dosed with MAb 3B3-PE38, a precursor of HY-KDEL, and with CD4-PE40 (26).…”

Section: Studies In Macaquessupporting

confidence: 82%

Design andIn VivoCharacterization of Immunoconjugates Targeting HIV gp160

Pincus

Song

Maresh

et al. 2017

J Virol

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The envelope (Env) glycoprotein of HIV is expressed on the surface of productively infected cells and can be used as a target for cytotoxic immunoconjugates (ICs), in which cell-killing moieties, including toxins, drugs, or radionuclides, are chemically or genetically linked to monoclonal antibodies (MAbs) or other targeting ligands. Such ICs could be used to eliminate persistent reservoirs of HIV infection. We have found that MAbs which bind to the external loop of gp41, e.g., MAb 7B2, make highly effective ICs, particularly when used in combination with soluble CD4. We evaluated the toxicity, immunogenicity, and efficacy of the ICs targeted with 7B2 in mice and in simian-human immunodeficiency virus-infected macaques. In the macaques, we tested immunotoxins (ITs), consisting of protein toxins bound to the targeting agent. ITs were well tolerated and initially efficacious but were ultimately limited by their immunogenicity. In an effort to decrease immunogenicity, we tested different toxic moieties, including recombinant toxins, cytotoxic drugs, and tubulin inhibitors. ICs containing deglycosylated ricin A chain prepared from ricin toxin extracted from castor beans were the most effective in killing HIVinfected cells. Having identified immunogenicity as a major concern, we show that conjugation of IT to polyethylene glycol limits immunogenicity. These studies demonstrate that cytotoxic ICs can target virus-infected cells in vivo but also highlight potential problems to be addressed. IMPORTANCE It is not yet possible to cure HIV infection. Even after years of fully effective antiviral therapy, a persistent reservoir of virus-infected cells remains. Here we propose that a targeted conjugate consisting of an anti-HIV antibody bound to a toxic moiety could function to kill the HIV-infected cells that constitute this reservoir. We tested this approach in HIV-infected cells grown in the lab and in animal infections. Our studies demonstrated that these immunoconjugates are effective both in vitro and in test animals. In particular, ITs constructed with the deglycosylated A chain prepared from native ricin were the most effective in killing cells, but their utility was blunted because they provoked immune reactions that interfered with the therapeutic effects. We then demonstrated that coating of the ITs with polyethylene glycol minimized the immunogenicity, as has been demonstrated with other protein therapies.

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Section: Studies In Macaquessupporting

confidence: 82%

Design andIn VivoCharacterization of Immunoconjugates Targeting HIV gp160

Pincus

Song

Maresh

et al. 2017

J Virol

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“…We have examined over 100 anti-Env mabs for efficacy in targeting ICs, and have identified a key epitope on gp41, defined by mAb 7B2, as the best target [10]–[15]. Abs to other epitopes on Env, including the CD4 binding site and V3 loop, as well as CD4 itself, have also been used to target ICs [10], [24], [25], but are less effective when directly compared to 7B2 in the presence of sCD4, see figure 6, and references [12], [14], [15]. Over the past several years, a host of potent broadly neutralizing Abs to HIV gp120 have been developed [62]–[65], but in side-by-side assays as ICs, none is as effective as 7B2+ sCD4 (S.H.…”

Section: Discussionmentioning

confidence: 99%

Anti-HIV Double Variable Domain Immunoglobulins Binding Both gp41 and gp120 for Targeted Delivery of Immunoconjugates

Craig

Summa²,

Corti³

et al. 2012

PLoS ONE

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BackgroundAnti-HIV immunoconjugates targeted to the HIV envelope protein may be used to eradicate the latent reservoir of HIV infection using activate-and-purge protocols. Previous studies have identified the two target epitopes most effective for the delivery of cytotoxic immunoconjugates the CD4-binding site of gp120, and the hairpin loop of gp41. Here we construct and test tetravalent double variable domain immunoglobulin molecules (DVD-Igs) that bind to both epitopes.MethodsSynthetic genes that encode DVD-Igs utilizing V-domains derived from human anti-gp120 and anti-gp41 Abs were designed and expressed in 293F cells. A series of constructs tested different inter-V-linker domains and orientations of the two V domains. Antibodies were tested for binding to recombinant Ag and native Env expressed on infected cells, for neutralization of infectious HIV, and for their ability to deliver cytotoxic immunoconjugates to infected cells.FindingsThe outer V-domain was the major determinant of binding and functional activity of the DVD-Ig. Function of the inner V-domain and bifunctional binding required at least 15 AA in the inter-V-domain linker. A molecular model showing the spatial orientation of the two epitopes is consistent with this observation. Linkers that incorporated helical domains (A[EAAAK]nA) resulted in more effective DVD-Igs than those based solely on flexible domains ([GGGGS]n). In general, the DVD-Igs outperformed the less effective parental antibody and equaled the activity of the more effective. The ability of the DVD-Igs to deliver cytotoxic immunoconjugates in the absence of soluble CD4 was improved over that of either parent.ConclusionsDVD-Igs can be designed that bind to both gp120 and gp41 on the HIV envelope. DVD-Igs are effective in delivering cytotoxic immunoconjugates. The optimal design of these DVD-Igs, in which both domains are fully functional, has not yet been achieved.

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“…This suggests that there is also a therapeutic significance for saponinum album/saporin mixtures. For example, this combination might be of some use with HIV-infected macrophages that persist after an anti-retroviral therapy; commonly, these need to be eliminated by immunotoxins (van Oijen, 1998;Kennedy et al, 2006). Due to the high susceptibility of macrophages to saporin after combination with saponins, it would be a potential alternative to the administration of other potent immunotoxins for the induction of apoptosis in these HIV-infected macrophages.…”

Section: Discussionmentioning

confidence: 99%

Enhancement of Saporin Toxicity Against U937 Cells byGypsophilaSaponins

Weng

Melzig

Bachran

et al. 2008

Journal of Immunotoxicology

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Saporin, a type I ribosome-inactivating protein (RIP), removes an adenine residue from the 28S ribosomal RNA as part of a process that leads to inhibition of protein synthesis. As a result, saporin has been shown to exert a strong toxicity in the immune system against macrophages. However, studies have shown that macrophage-like U937 cells are fully resistant against low concentrations of unmodified and his-tagged saporin solutions (6 pM) that normally kill macrophages and APC. In the studies reported here, we noted that with these cells, these RIP solutions only became highly cytotoxic when they were used in a combined treatment with Gypsophila saponins. We determined that this cytotoxicity was the result of an induction of apoptosis triggered by the now-internalized saporin molecules that had previously remained outside of these cells. The results here indicate that the Gypsophila saponins induce, in some manner yet to be fully defined, a stimulation of the endocytosis of saporin by these cells.

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Anti-HIV-1 immunotoxin 3B3(Fv)-PE38: enhanced potency against clinical isolates in human PBMCs and macrophages, and negligible hepatotoxicity in macaques

Cited by 27 publications

References 55 publications

Design andIn VivoCharacterization of Immunoconjugates Targeting HIV gp160

Design andIn VivoCharacterization of Immunoconjugates Targeting HIV gp160

Anti-HIV Double Variable Domain Immunoglobulins Binding Both gp41 and gp120 for Targeted Delivery of Immunoconjugates

Enhancement of Saporin Toxicity Against U937 Cells byGypsophilaSaponins

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