Characterisation and heterologous biosynthesis of burnettiene A, a new polyene-decalin polyketide from Aspergillus burnettii

Chemical exploration of the recently described Australian fungus, Aspergillus burnettii, uncovered a new metabolite, burnettiene A. Here, we characterise the structure of burnettiene A as a polyene-decalin polyketide. Bioinformatic analysis of the genome of A. burnettii identified a putative biosynthetic gene cluster for burnettiene A (bue), consisting of eight genes and sharing similarity to the fusarielin gene cluster. Introduction of the reassembled bue gene cluster into Aspergillus nidulans for heterologous expression resulted in the production of burnettiene A under native promoters. Omission of bueE encoding a cytochrome P450 led to the production of preburnettiene A, confirming that BueE is responsible for catalysing the regiospecific multi-oxidation of terminal methyl groups to carboxylic acids. Similarly, bueF was shown to encode an ester-forming methyltransferase, with its omission resulting in the production of the tricarboxylic acid, preburnettiene B. Introduction of an additional copy of the transcription factor bueR under the regulation of the gpdA promoter significantly improved the heterologous production of the burnettienes. Burnettiene A displayed strong in vitro cytotoxicity against mouse myeloma NS-1 cells (MIC 0.8 µg/mL).

Preparation of polyclonal and monoclonal anti-idiotypic antibodies against morphine-specific immunoglobulins

The preparation and study of anti-idiotypic (secondary) antibodies (Ab2) against monoclonal primary antibodies (Ab1) specific to biologically active molecules with a known structure is of great scientific and practical importance. Due to partial antigenic similarity of Ab2 and the initial antigen structures, these antibodies can be the basis of the vaccine, if the antigen usage is not possible, or is limited by law. In particular, one may create Ab2-based preparations, designed for immunization, in order to prevent and treat the drug addiction. The value of Ab2 properties increases even more if Ab1, used to obtain them, recognize different parts of the antigen molecule, which makes it possible to obtain second-generation antibodies with a wide range of specificity. In this work, the morphine-like polyclonal and monoclonal Ab2 were obtained. In each case, as the first-generation immunoglobulins for immunization, we used two murine monoclonal antibodies (mAbs) specific to different morphine derivatives: 3K11 antibodies to 3-0-carboxymethyl (CMM) and 2-p-carboxyphenylazomethyl (FAM) derivatives, as well as 6G1 antibodies to 6-hemisuccinyl derivative (GSM). After immunization of the horse with Ab1 and development of immune response, three pools of specific polyclonal antibodies were isolated from the animal blood serum: horse anti-species antibodies to the total mouse immunoglobulins (HAM); horse anti-idiotypic antibodies against 3K11 antibodies (HAM-K11), and against 6G1 antibodies (HAM-G1). In parallel, immunization of mice with 3K11 and 6G1 antibodies and fusion of obtained lymphocytes with Sp2/0 mouse myeloma cells by the Milstein-Köhler method resulted in three producers of anti-idiotypic antibodies: a clone producing mouse monoclonal Ab2 specific for mAb-6G1 (AIG1), as well as clones producing anti-mAb-3K11 antibodies (AI-K11A and AI-K11B). The physico-chemical and antigenic properties of all the Ab2 obtained were characterized. It was shown that the horse anti-idiotypic immunoglobulins not only belong to different classes, but are also polyvalent, while all monoclonal Ab2 obtained are represented by IgM immunoglobulins, being also strictly specific to the corresponding first-generation antibodies. Subsequently, the morphine-like properties of the first domestic polyclonal and monoclonal Ab2 obtained in the work will be investigated in a cellular model. Likewise, we shall study their ability to induce Ab3 as well as morphine-specific Ab1.

PREPARATION AND PROPERTIES OF MURINE ANTI-IDIOTYPIC MONOCLONAL ANTIBODIES RECOGNIZING PRIMARY RABBIT POLYCLONAL ANTIBODIES AGAINST MORPHINE DERIVATIVES

Anti-idiotypic antibodies (Ab2), according to the network theory of Jerne, are second-generation immunoglobulins that are produced against the idiotype of an antibody to a specific antigen. Despite the large number of works devoted to the study of the properties of these proteins, their role in the regulation of the immune system is not fully known. It may consist in maintaining or blocking a minimal immune response to the antigen. The study of Ab2 is of great practical and scientific importance. The special properties of Ab2, namely, the ability to partially reproduce the structure of the primary antigen and, upon immunization, induce the appearance of tertiary antibodies, which, like first-generation antibodies, can bind to the antigen, have found application in the development of Ab2-based vaccines, in particular, for the treatment of tumors. In view of the presence of a number of limitations on research related to psychoactive substances, the development of Ab2- based vaccines against drug addiction also seems promising. To example, anti-idiotypic antibodies obtained for this purpose possessing a cocaine-like structure are described in the literature. In this work, murine monoclonal anti-idiotypic antibodies (mAb2) mimicking the structure of various morphine derivatives were obtained. Rabbit polyclonal antibodies to the 6-hemisuccinyl derivative of morphine conjugated with bovine serum albumin isolated by affinity chromatography were used as primary antibodies for immunization. Four hybridoma clones were obtained as a result of the fusion of immunized mice lymphocytes with mouse Sp2/0 mouse myeloma cells by the Milstein-Köhler method. After growth in animals, mAb2 produced by hybridoma cells were affinity purified. We investigated the physicochemical and antigenic properties of the isolated antibodies. It was shown that the obtained mAb2 differ in immunological specificity, competing in different degree with morphine derivatives for binding to first-generation antibodies. We tested the possibility of using the obtained mAb2 as antigen analogues in the solid-phase enzyme-linked immunosorbent assay to determine the titer of primary antibodies against morphine in the blood serum of laboratory animals immunized with morphine derivatives. Based on the obtained anti-idiotypic antibodies, it is proposed to develop test systems to determine the serum opiate-specific antibodies in people after specific vaccination for therapeutic or prophylactic purposes to avoid the use of drugs as antigens immobilized on the solid phase in the analysis.