Immunotherapy of spontaneous mammary tumors in mongrel dogs with autologous tumor cells and neuraminidase

Exploration of the Sialic Acid World

Sialic acids are cytoprotectors, mainly localized on the surface of cell membranes with multiple and outstanding cell biological functions. The history of their structural analysis, occurrence, and functions is fascinating and described in this review. Reports from different researchers on apparently similar substances from a variety of biological materials led to the identification of a 9-carbon monosaccharide, which in 1957 was designated "sialic acid." The most frequently occurring member of the sialic acid family is N-acetylneuraminic acid, followed by N-glycolylneuraminic acid and O-acetylated derivatives, and up to now over about 80 neuraminic acid derivatives have been described. They appeared first in the animal kingdom, ranging from echinoderms up to higher animals, in many microorganisms, and are also expressed in insects, but are absent in higher plants. Sialic acids are masks and ligands and play as such dual roles in biology. Their involvement in immunology and tumor biology, as well as in hereditary diseases, cannot be underestimated. N-Glycolylneuraminic acid is very special, as this sugar cannot be expressed by humans, but is a xenoantigen with pathogenetic potential. Sialidases (neuraminidases), which liberate sialic acids from cellular compounds, had been known from very early on from studies with influenza viruses. Sialyltransferases, which are responsible for the sialylation of glycans and elongation of polysialic acids, are studied because of their significance in development and, for instance, in cancer. As more information about the functions in health and disease is acquired, the use of sialic acids in the treatment of diseases is also envisaged.

Synthesis of N-acetylneuraminyl-alpha 2,3(6)lactose-malate dehydrogenase conjugate for detecting sialic acid terminal groups on glycoproteins via homogeneous lectin-based enzyme-linked binding assay

An N-acetylneuraminyl-alpha 2,3(6)lactose-malate dehydrogenase (MDH-Lac-Neu5Ac) conjugate is prepared via an isothiocyanate conjugation method using a p-aminophenethylamino derivative of sialyllactose. The newly synthesized conjugate can be utilized as a reagent in a novel homogeneous lectin-based, enzyme-linked, competitive binding assay (1-3) for probing the specific carbohydrate structure and content of intact glycoproteins. The enzymatic activity of the MDH-Lac-Neu5Ac conjugate is shown to be significantly inhibited (35%) by sialic acid-binding lectin, Limax flavus agglutinin (LFA), and this inhibition is reversed by mucin, a glycoprotein possessing sialic acid terminals. The asialo form of mucin, however, binds weakly to LFA, yielding no substantial increase in the MDH-Lac-Neu5Ac activity at comparable glycoprotein concentrations. Use of the newly synthesized conjugate in conjunction with LFA or other lectins capable of binding sialic acid may provide a rapid and convenient way to detect the presence and relative amount of sialic acid terminal groups within intact glycoprotein structures.

Immunological aspects of mammary tumors in dogs and cats: a survey including own studies and pertinent literature

Naturally occurring cancer in companion animals parallels cancer in man more closely than does experimentally induced cancer in inbred laboratory animals. In dogs and cats, as in man, a role for immune responses is indicated in the development of tumors. A survey is presented based on the literature and our own studies concerning the immunological and immunotherapeutic aspects of canine and feline mammary neoplasia. In dogs bearing mammary neoplasms, circulating immune complexes appear to play a negative role in the generation of effective antitumor immune responses. The functional role of peripheral blood lymphocytes and tumor-infiltrating lymphocytes in dogs and cats with mammary tumors is not yet fully established. No tumor antigen responsible for humoral or cellular responses has yet been identified. Extracorporeal perfusion of serum of dogs with mammary tumors and subcutaneous administration of mitomycin- and neuraminidase-treated autologous tumor cells are associated with improved prognosis. The opposite was true for i.v. treatment with BCG or Corynebacterium parvum vaccine in our study, in contrast to a previous report. A number of other treatment modalities in cats and dogs with mammary carcinomas failed to induce tumor regression. Canine and feline mammary carcinomas are good candidates for modern immunotherapeutic approaches.

Tumor therapy of neoplastic diseases with tumor cells and neuraminidase: experimental studies on chessboard vaccination in transplantation tumors

The therapeutic effect of intradermal (i.d.) injection of tumor cells mixed with VCN on growth of spontaneous metastases in transplantable tumors in mice (3-Lewis lung adenocarcinoma; B16-melanoma) and rats (R-3230 mammary adenocarcinoma) was investigated. Intradermal injection was done in a chessboard-like manner; increasing numbers (10(5), 10(6) and 10(7)) of Mitomycin-treated tumor cells (M-TC) were each mixed with increasing amounts (10, 50 and 100 mU) of Vibrio cholerae Neuraminidase (VCN). These different mixtures were injected i.d. at different sites one day after resection of the primary tumor graft to mice and rats, suffering from minimal residual disease. The therapeutic effect of this so-called chessboard vaccination on minimal residual disease was compared to that of the subcutaneous or i.d. injection of VCN-treated M-TC (10(5), 10(6), 10(7) or 10(8) cells) or of single mixtures of M-TC and VCN. The results show that compared to VCN-treated M-TC or single mixtures of M-TC and VCN, chessboard vaccination is the only procedure that is therapeutically effective on metastasation of Lewis lung adenocarcinoma. The therapeutic effect could be abrogated by heat-inactivation of VCN. Incomplete chessboard vaccinations (10(5), 10(6), 10(7) tumor cells, each mixed with 5 mU VCN only) were likewise ineffective. However, treatment with incomplete chessboard vaccinations in combination with a low dose of cyclophosphamide (which is not immunosuppressive, but partly inhibits tumor growth) had a synergistic therapeutic effect on minimal residual disease of Lewis lung adenocarcinoma. In contrast, growth of metastases of B16-melanoma and R-3230 adenocarcinoma could not significantly be influenced by any of those treatments. The DTH response of tumor bearing animals against i.d. applied tumor cells was neither significantly enhanced by the admixture of enzymatically active VCN nor did the DTH response seem to be predictive for a tumor-therapeutic effect. Thomsen-Friedenreich antigens could serologically be detected on untreated cells of Lewis lung adenocarcinoma, B16-melanoma and R-3230 adenocarcinoma. Exposure of Thomsen-Friedenreich antigens after treatment with VCN was enhanced on cells of all tumors except Lewis lung adenocarcinoma. As chessboard vaccination only proved to be successful in Lewis lung adenocarcinoma, but not in the other tumors, it can be concluded that the exposure of Thomsen-Friedenreich antigen plays no decisive role in tumor therapy with tumor cells and VCN. Chessboard vaccination was tolerated without any side effects. Tumor enhancement was not observed.(ABSTRACT TRUNCATED AT 400 WORDS)

BCG versus VCN: the antigenicity and the adjuvant effect of both compounds

Enzymatically active Vibrio cholerae neuraminidase (VCN) acts as an adjuvant when it is combined with an antigen. This has been demonstrated for bacterial, viral, protein, and cellular antigens and was found for the humoral, but more pronounced for the cellular immune response. In this study, the adjuvant activity of VCN for live BCG is discussed. Live BCG itself is regarded as a rather potent immunostimulator. A total of 6.5 mU of VCN, being most effective as derived from previous adjuvant experiments, was combined with 10(6) or 10(7) live BCG and injected IV into mice. Booster injections were given on day 12. Challenge was administered in the footpad on day 17 either with 6.5 mU VCN or with 5 x 10(4) or 5 x 10(6) dead BCG. Footpad swelling was recorded 24 h after challenge. After clinical examination, mice were bled and antibodies against BCG and VCN were measured. The results show that VCN specifically enhances the cellular, not the humoral, immune reaction against BCG, while BCG is unable specifically to enhance immune reaction against VCN. However, BCG unspecifically stimulates the cellular reaction of the organism against an antigen, primarily injected, subsequent to BCG for instance, against VCN.