A NEW METHOD BASED ON THE USE OF IMMOBILIZED SINGLE-DOMAIN ANTIBODIES TO REMOVE CERTAIN MAJOR PROTEINS FROM BLOOD PLASMA HELPS TO REDUCE NONSPECIFIC SIGNAL IN AN IMMUNOASSAY

A generally underestimated problem of immunoassays is its susceptibility to various interferences, being the Achilles heel of these assays (interventions in the analysis). The presence of interfering substances in the patient’s specimen can cause erroneous test sample result, which may lead to incorrect diagnosis and catastrophic consequences for the patient. Hence, one should pay particular attention to identifying possible interferences in the test systems used and, when possible, develop and apply methods to overcome them. The issue of avoiding interference is particularly important for immunoassays of biomarkers in human plasma or serum. In order to reduce possible interferences, it would be desirable to have an opportunity of specific and adaptable pretreatment of blood samples for a specifically assayed marker protein, as applied to a specific test system. We assume that such pretreatment may be done by combining the immunosorbents based on the use of special single-domain antibodies (nanobodies).The nanobodies are recombinant proteins, derivatives of single-domain antigen-recognizing variable fragments of specific antibodies, consisting of a dimer of truncated heavy chains in the complete absence of light chains. Such specific antibodies are detectable in the normal samples taken from members of the Camelidae family (Camelids), and in some species of cartilaginous fishes, along with the common antibodies. The special properties of nanobodies can provide certain advantages in their use, compared with antibodies of traditional structure and their derivatives.In this paper, we have shown for the first time, that the immunosorbents based on certain combination of single-domain antibodies used as ligands able for specifically binding and removal of specific high-abundance human blood proteins, may be selected for a given marker blood antigen in such a way that they will be an effective tool for blood pretreatment, aiming to reduce possible effects of interference and increased sensitivity in the diagnostic “sandwich” enzyme immunoassay. A new method of plasma pretreatment is demonstrated with human plasma samples (at a dilution of 1:40) of two patients. A previously developed model system for detection of lactoferrin protein was used to analyze plasma samples. It is shown that a significantly increased ratio of total detected signal to the nonspecific background signal could be obtained after drastic reduction of this background by affinity removal of 3 major protein fractions, i.e., fibrinogen, IgG alpha-2-macroglobulin from blood plasma samples, using appropriate immobilized single domain antibodies

ALL-1/MLL1, a homologue of Drosophila TRITHORAX, modifies chromatin and is directly involved in infant acute leukaemia

Rearrangements of the ALL-1/MLL1 gene underlie the majority of infant acute leukaemias, as well as of therapy-related leukaemias developing in cancer patients treated with inhibitors of topoisomerase II, such as VP16 and doxorubicin. The rearrangements fuse ALL-1 to any of \u3e50 partner genes or to itself. Here, we describe the unique features of ALL-1-associated leukaemias, and recent progress in understanding molecular mechanisms involved in the activity of the ALL-1 protein and of its Drosophila homologue TRITHORAX

SINGLE DOMAIN ANTIBODIES AND BIOENGINEERING DRUGS ON THEIR BASIS: NEW OPPORTUNITIES FOR DIAGNOSTICS AND THERAPY

Almost 20 years ago, a unique class of antibodies devoid of L chains was discovered in Camelidae blood serum. Only one variable domain is responsible for antigen recognition in these unusual antibodies. A recombinant protein, which is analogue to such antigen-recognizing variable domain was called the single domain antibody (sdAb), “nanobody” or “nanoantibody”. The single-domain antibodies and their derivatives have been widely used in the field of biology, toxicology and medicine offering new opportunities for diagnosis and treatment of cancer, autoimmune diseases, infectious diseases, and for toxin neutralization. This review focuses on latest researches in the field and concerns some prospectives for creation of nanoantibody-based diagnostic and therapeutic drugs

B2 RNA and 7SK RNA, RNA polymerase III transcripts, have a cap-like structure at their 5' end.

We found that hydrolysates of poly(A)+ RNA from Ehrlich ascites carcinoma cells which were transcribed by RNA polymerase III contained an unusual component designated as X. It was part of B2 RNA representing a transcript of B2 retroposon, typical of rodents. The component X possesses a cap-like structure, xppp5'G, where x has a non-nucleotide structure. About half of all B2 RNAs contained this group at the 5' end. Previously, Epstein et al. (1) detected a similar structure at the 5' end of small nuclear U6 RNA. Later, Singh and Reddy (2) showed methyl to be the blocking group in the component x of U6 RNA. Besides B2 RNA, we found 5' ends containing methyl groups in 7SK RNA

Nucleotide sequence of small polyadenylated B2 RNA.

Small poly(A)-containing RNA molecules which hybridize to the ubiquitous short repetitive sequence B2 and which are transcribed by RNA polymerase III have been identified in the cytoplasm of mouse cells. Here, we describe the structure of this small B2 RNA. A cDNA library was prepared from low-molecular-weight cytoplasmic poly(A)+RNA isolated from Ehrlich carcinoma cells and the clones which hybridized to B2 sequence were selected. The clones were sequenced and shown to contain B2 sequences followed by a poly(A) tract. The sequences of the cloned B2 RNAs different from each other by 3-10%, being similar in this respect to genomic B2 copies. Thus, B2 RNA is transcribed from many different B2 sequences in the genome. The 5'-ends of B2 RNA at least in most molecules coincide with the beginning of B2 genomic sequence. The poly(A) segments located at the 3'-end of small B2 RNA are the same size as in mRNA molecules, suggesting posttranscriptional formation. In some clones, additional sequences were detected between the 3'-end of B2 sequence and the poly(A) stretch. They seem to result from a lesion in the RNA polymerase III terminator in the corresponding B2 sequences. The possible significance of B2 sequences and small B2 RNA is discussed

Anti-Idiotypic Nanobodies Mimicking an Epitope of the Needle Protein of the Chlamydial Type III Secretion System for Targeted Immune Stimulation

The development of new approaches and drugs for effective control of the chronic and complicated forms of urogenital chlamydia caused by Chlamydia trachomatis, which is suspected to be one of the main causes of infertility in both women and men, is an urgent task. We used the technology of single-domain antibody (nanobody) generation both for the production of targeting anti-chlamydia molecules and for the subsequent acquisition of anti-idiotypic nanobodies (ai-Nbs) mimicking the structure of a given epitope of the pathogen (the epitope of the Chlamydial Type III Secretion System Needle Protein). In a mouse model, we have shown that the obtained ai-Nbs are able to induce a narrowly specific humoral immune response in the host, leading to the generation of intrinsic anti-Chlamydia antibodies, potentially therapeutic, specifically recognizing a given antigenic epitope of Chlamydia. The immune sera derived from mice immunized with ai-Nbs are able to suppress chlamydial infection in vitro. We hypothesize that the proposed method of the creation and use of ai-Nbs, which mimic and present to the host immune system exactly the desired region of the antigen, create a fundamentally new universal approach to generating molecular structures as a part of specific vaccine for the targeted induction of immune response, especially useful in cases where it is difficult to prepare an antigen preserving the desired epitope in its native conformation