Monoclonal Antibodies in Immunodiagnosis & Immunotherapy

It is the stepwise accumulation of scientific information that allows the rare breakthrough which forever changes our understanding of a disease process. This paper begins with a review of the history of great experiments initiated in the 1960s which showed that multiple chronic neurological diseases were transmissible and in some instances were caused by a virus. Such an historical perspective combined with the rationale for the viral etiology of MS described herein, led Dr. Hilary Koprowski to organize a team of clinicians, pathologists, cell biologists, virologists, and immunologists to obtain MS brain, propagate MS brain cells in tissue culture, and to analyze cells for productive or latent infection. No virus was found with the state-of-the-art techniques available in the 1970s. However, currently available molecular biologic strategies and techniques allow virus detection not possible 30 years ago. These studies could confirm Dr. Koprowski's prophetic vision and identify the virus that causes MS, including the mechanism by which demyelination is produced.

CO17-1A/GA73-3/EpCam/KSA is a cellular adhesion molecule expressed on the majority of tumor cells in most patients with colorectal carcinoma. One of the first mouse monoclonal antibodies (MAbs) for therapeutic use was produced against this particular tumor associated antigen (MAb17-1A). MAb17-1A has served as a model for the development of antibody therapy. It exerts therapeutic effects through antibody dependent cellular cytotoxicity (ADCC), induction of an idiotypic network cascade and maybe also by complement activation. Addition of cytokines that augment these functions, mainly granulocyte macrophage-cerebrospinal fluid (GM-CSF), seemed to improve the clinical efficacy as well as chemotherapeutic agents (5-Fu). In advanced disease the clinical effect is, however, modest while the most beneficial clinical situation seems to be the adjuvant setting. Twenty years have passed since the EpCam antigen was identified as a target structure for immunotherapy, but still we do not know how to optimally use this target. The antigen might, however, be a rewarding structure to utilize for therapy. Preclinical and clinical trials are ongoing aimed at improving passive and active immunotherapy using CO17-1A/EpCam as a target antigen in colorectal carcinoma.

Tumor cells may evade immune surveillance by possessing polysaccharides or carbohydrates on their surface. This evasive strategy is effective because glycans are poorly immunogenic and fail to elicit immunological memory responses due to an absence of T-cell processing. Induction of an immune response to cell surface carbohydrate antigens is considered as an important strategy to fight cancer. As carbohydrates per se are poor immunogens, alternative approaches are being evaluated to induce functional cross-reactive responses. We are focusing on the use of peptide mimotopes of tumor-associated carbohydrate antigens to challenge cancer, as we would manipulate the immune system to establish protective immunity based on carbohydrate cross-reactive humoral and cellular responses.

Several in vivo studies demonstrated that tumor metastasis depend on the expression of carbohydrate Lewis structures. Lewis antigens and their derivatives such as Lewis b (Le^b), Lewis X (LeX), sialyl Lewis X (SA-LeX), sialyl Lewis a (SA-Le^a), and Lewis Y (LeY) were identified as tumor-associated structures approximately 20 years ago by Koprowski et al. using hybridoma technology and showed that upregulation and/or de novo expression of these determinants on the tumor cell surface is associated with a poor prognosis. LeX and SA-LeX are ligands for selectin adhesion molecules; E- and P-selectins are vascular receptors expressed on activated endothelial cells (ECs) and L-selectin is expressed on leukocytes. Leukocytes also express on their surface LeX and SA-LeX determinants, which are involved in the initial steps of extravasation, that is, rolling, which is α step mediated by interaction with E-selectin on ECs. We hypothesized that the tumor cells transmigration from the bloodstream to metastatic sites is similar to lymphocyte extravasation and that adhesion of cancer cells in analogy with the lymphocyte rolling is mediated by interaction of carbohydrate determinants on tumor cells with selectins on ECs. To assess the role of interaction of carbohydrate structures with E-selectin in metastatic process in vivo, we demonstrated that the peptides mimicking SA-Le^a blocked colonization of tumor cells in experimental model of lung metastasis in vivo. Furthermore, the metastases formation was completely attenuated in E-selectin-knock out (KO) mice demonstrating the importance of selectin-mediated interaction in this process. We also showed that a peptide mimicking SA-Le^a E-selectin ligand has an ability to significantly reduce neutrophil recruitment into peritoneal cavity in acute inflammatory conditions. These studies support the hypothesis that the interaction of tumor cells via the carbohydrate SA-Le^a determinant and E-selectin constitutes the important step in the metastatic process in analogy with lymphocyte extravasation and that carbohydrate antigen mimics have a potential as anti-inflammatories and anti-adhesive tumor therapeutics.

Current evidence suggests that the induction of cell-mediated immunity is required for a successful HIV-1 vaccine. Delayed type hypersensitivity (DTH) and cellular cytotoxicity are closely linked elements of the cellular immune response, both are favored by immunizations that result in a T-helper (Th)-1 response. The classical experimental animal for the study of DTH is the guinea pig. Here we report that guinea pigs can readily be sensitized for DTH skin reactions to envelope protein with a plasmid expressing HIV-1_MN (subtype B) envelope, as well as with the recombinant HIV-1 envelope protein. Further, utilizing peptide probes that in aggregate represent the entire gp120 molecule, common and unique dominant epitopes induced by each method of immunization were identified.

Since the first development of a rabies vaccine by Pasteur in the late 19th century, second- and third-generation vaccines with improved efficacy and less reactogenicity have been developed for use in humans and animals. Despite the availability of safe but rather expensive vaccines based on inactivated virus propagated in diploid cell cultures, much of the human vaccinations worldwide are still carried out with nerve tissue-containing vaccines, which have various side effects. A number of experimental vaccines are under development that may provide alternative safe and potent but less expensive vaccine options. These include DNA vaccines, recombinant viral vaccines, and recombinant protein vaccines. Further testing is needed to determine if and which one of these novel vaccines will make their way into mass production and application in the future.

In the United States, extensive reservoirs of the rabies virus exist in many diverse wild animal species, which continue to pose a serious risk of lethal infection of humans and cause an economic burden exceeding $1 billion annually. Previous experience with rabies control in foxes in Europe has clearly demonstrated that oral immunization with live vaccines is the only practical approach to eradicate rabies in free-ranging animals. However, unlike Europe where vulpine rabies was the only major reservoir, the Americas harbor a variety of species including raccoons, skunks, coyotes, and bats that serve as the primary reservoirs of rabies. Each of these animal reservoirs carries an antigenically distinct virus variant. The currently available modified-live rabies virus vaccines have either safety problems or do not induce sufficient protective immunity in particular wildlife species. Therefore, there is a need for the development of new live rabies virus vaccines that are very safe and highly effective in particular wildlife species. Based on previous observations indicating that the potency of a vaccine is significantly increased if the G protein of the vaccine strain is identical to that of the target virus, we have used a reverse genetics approach to engineer viruses that contain G proteins from virus strains associated with relevant wildlife species. Furthermore, because our recent data also indicate that the pathogenicity of a particular rabies virus strain is inversely proportional to its ability to induce apoptosis and that low-level apoptosis-inducing ability is associated with low anti-viral immune responses, we inserted genes encoding pro-apoptotic proteins to stimulate immunity or otherwise interfere with viral pathogenesis into these recombinant viruses to enhance their efficacy and safety.

Research marches on the feet of methodology. Advances are made when we have acquired the means to utilize the accrued information. In this way, investigation into the influence of energy restriction in cancer has gone through three distinct periods. After the initial observation by Moreschi in 1909, there was about a decade of active research in this area. Then interest waned, possibly because the field had gone as far as it could considering the knowledge and methodology available at the time. Interest was rekindled in 1940 due, principally, to the work coming from the laboratories of Tannenbaum at the Michael Reese Hospital in Chicago and Baumann at the University of Wisconsin. Another decade of active research followed. In this period we learned how to design experimental diets and interest was expressed in dietary constituents. By 1950 publications on this type of research had dwindled and the field lay virtually dormant for 30 years. Since the early 1980s research on this topic has blossomed and we now know enough about physiology and molecular biology to probe the mechanisms underlying the phenomenon. Energy flux, as in exercise, also inhibits carcinogenesis. Energy restriction modulates oxidative DNA damage and enhances DNA repair. It is now apparent that energy restriction affects adrenal metabolism, insulin metabolism, and various aspects of gene expression. Understanding the basic mechanisms should provide important insights into control of tumor proliferation.