Treating Cancer as an Infectious Disease—Viral Antigens as Novel Targets for Treatment and Potential Prevention of Tumors of Viral Etiology

Nearly 20% of human cancers worldwide have an infectious etiology with the most prominent examples being hepatitis B and C virus-associated hepatocellular carcinoma and human papilloma virus-associated cervical cancer. There is an urgent need to find new approaches to treatment and prevention of virus-associated cancers.Viral antigens have not been previously considered as targets for treatment or prevention of virus-associated cancers. We hypothesized that it was possible to treat experimental HPV16-associated cervical cancer (CC) and Hepatitis B-associated hepatocellular carcinoma (HCC) by targeting viral antigens expressed on cancer cells with radiolabeled antibodies to viral antigens. Treatment of experimental CC and HCC tumors with (188)Re-labeled mAbs to E6 and HBx viral proteins, respectively, resulted in significant and dose-dependent retardation of tumor growth in comparison with untreated mice or mice treated with unlabeled antibodies.This strategy is fundamentally different from the prior uses of radioimmunotherapy in oncology, which targeted tumor-associated human antigens and promises increased specificity and minimal toxicity of treatment. It also raises an exciting possibility to prevent virus-associated cancers in chronically infected patients by eliminating cells infected with oncogenic viruses before they transform into cancer

Pre-Clinical Evaluation of a 213Bi-Labeled 2556 Antibody to HIV-1 gp41 Glycoprotein in HIV-1 Mouse Models as a Reagent for HIV Eradication

Any strategy for curing HIV infection must include a method to eliminate viral-infected cells. Based on our earlier proof-of-principle results targeting HIV-1 infected cells with radiolabeled antibody (mAb) to gp41 viral antigen, we embarked on identifying a suitable candidate mAb for preclinical development.Among the several human mAbs to gp41 tested, mAb 2556 was found to have high affinity, reactivity with multimeric forms of gp41 present on both the surface of virus particles and cells expressing HIV-1 Env, and recognition of a highly conserved epitope of gp41 shared by all HIV-1 subtypes. Also, mAb 2556 was the best in competition with HIV-1+ serum antibodies, which is an extremely important consideration for efficacy in the treatment of HIV patients. When radiolabeled with alpha-emitting radionuclide 213-Bismuth ((213)Bi) - (213)Bi-2556 efficiently and specifically killed ACH-2 human lymphocytes chronically infected with HIV-1, and HIV-1 infected human peripheral blood mononuclear cells (hPBMCs). The number of binding sites for (213)Bi-2556 on the surface of the infected cells was >10(6). The in vivo experiments were performed in two HIV-1 mouse models--splenic and intraperitoneal. In both models, the decrease in HIV-1 infected hPBMCs from the spleens and peritoneum, respectively, was dose-dependent with the most pronounced killing of hPBMCs observed in the 100 µCi (213)Bi-2556 group (P = 0.01). Measurement of the blood platelet counts and gross pathology of the treated mice demonstrated the lack of toxicity for (213)Bi-2556.We describe the preclinical development of a novel radiolabeled mAb reagent that could potentially be part of an HIV eradication strategy that is ready for translation into the clinic as the next step in its development. As viral antigens are very different from "self" human antigens - this approach promises high selectivity, increased efficacy and low toxicity, especially in comparison to immunotoxins

Novel IgG to melanin shows promise for radioimmunotherapy of metastatic melanoma

Despite several novel drugs for metastatic melanoma entering the market in the last few years, there is an enormous need for novel effective treatments that would not rely on patients’ specific genotypes, biochemical pathways, microbiomes or the variability of an individual’s immune system. Earlier we have conducted a successful Phase 1 Clinical trial in patients with metastatic melanoma of a murine antibody to melanin radiolabeled with beta emitter 188Rhenium (188Re). The trial demonstrated safety and was indicative of the efficacy of the approach targeting melanin with radiolabeled antibodies (1). However, the IgM isotype of that first generation antibody presented an impediment for its humanization and further clinical development. Recently, we have identified an 8C3 murine antibody to melanin of the IgG isotype which is amenable to humanization. The goal of this study was to evaluate the possibility of radiolabeling this new antibody with 188Re and alpha emitter 213Bismuth (213Bi) and to assess its potential as a radioimmunotherapy (RIT) reagent for metastatic melanomaJRC.G.I.5-Advanced Nuclear Knowledg

A Monoclonal Antibody to Bacillus anthracis Protective Antigen Defines a Neutralizing Epitope in Domain 1

Antibody (Ab) responses to Bacillus anthracis toxins are protective, but relatively few protective monoclonal antibodies (MAbs) have been reported. Protective antigen (PA) is essential for the action of B. anthracis lethal toxin (LeTx) and edema toxin. In this study, we generated two MAbs to PA, MAbs 7.5G and 10F4. These MAbs did not compete for binding to PA, consistent with specificities for different epitopes. The MAbs were tested for their ability to protect a monolayer of cultured macrophages against toxin-mediated cytotoxicity. MAb 7.5G, the most-neutralizing MAb, bound to domain 1 of PA and reduced LeTx toxicity in BALB/c mice. Remarkably, MAb 7.5G provided protection without blocking the binding of PA or lethal factor or the formation of the PA heptamer complex. However, MAb 7.5G slowed the proteolytic digestion of PA by furin in vitro, suggesting a potential mechanism for Ab-mediated protection. These observations indicate that some Abs to domain 1 can contribute to host protection

Expression of E6 and E7 in human cervical carcinoma cell lines and of HBx in hepatocellular carcinoma cell line by Western blot and effect of MG132 proteasome inhibitor treatment on the levels of E6, E7 and HBx in these cell lines:

<p>a) E6 from protein extracts of CasKi cells treated with MG132 for 3 hrs; b) E7 from protein extracts of CasKi cells treated with MG132 for 3 hrs; c) E6 from protein extracts of CasKi cells treated with MG132 for 6 hrs; d) E7 from protein extracts of SiHa cells treated with MG132 for 3 hrs; e) E7 from protein extracts of HeLa S3 cells treated with MG132 for 3 hrs; f) HBX from protein extracts of Hep 3B2.1-7 cells treated with MG132 for 3 hrs.</p

Radioimmunotherapy of Hep 3B2.1-7 tumors in nude mice:

<p>a) changes in tumor volume; b) control untreated mouse; c) mouse treated with 600 µCi ¹⁸⁸Re-4H9 mAb. Both mice shown on Day 18 post-treatment. In b and c lower panels show H&E stained tumors at the completion of the experiment.</p