With the onset of the COVID-19 pandemic, a number of molecular-based tests have been developed to diagnose SARS-CoV-2 infection. However, numerous available serological tests lack sufficient sensitivity or specificity. They do not detect specific antibodies in a significant proportion of patients with PCR-confirmed COVID-19. There is evidence that some convalescents have a relatively short-lived humoral immunity. In contrast, a number of publications have shown that T-cell response to human coronaviruses, including SARS-CoV-1, MERS, and SARS-CoV-2, can be strong and long-term. Assessment of T-cell immunity to SARS-CoV-2 is important not only for stratification of risks and identification of potentially protected populations with immunity acquired as a result of previous infection, but also for determining immunogenicity and potential efficacy of vaccines under development. The existing methods of quantitative or semi-quantitative assessment of specific T-cell response are mainly used in scientific research and are not standardised. The aim of the study was to develop and verify experimentally a test kit to be used in a standardised procedure for in vitro determination of T-cells specific to SARS-CoV-2 antigens, in human peripheral blood. Materials and methods: the TigraTest^® SARS-CoV-2 kit developed by GENERIUM, which determines the number of T-cells secreting interferon gamma in vitro, was tested in the study. Samples of venous blood of volunteers from three different groups were analysed in the study: presumably healthy volunteers; COVID-19 convalescents; individuals vaccinated against SARS-CoV-2. Results: the authors developed the TigraTest^® SARS-CoV-2 kit for in vitro determination of T-cells specific to SARS-CoV-2 antigens in human peripheral blood, demonstrated its specificity and performed preliminary assessment of its sensitivity. The study analysed the range and magnitude of the T-cell response in convalescent and vaccinated individuals. A pronounced T-cell response was also shown in some individuals with no symptoms or with unconfirmed diagnosis. It was discovered that the mean T-cell response to peptides of the spike protein (S-protein) was higher in the vaccinated individuals than in the convalescent patients. A correlation was determined between the severity of the disease and the level of T-cell response. Specific contributions of various groups of antigens to the T-cell response after COVID-19 infection were also determined. Conclusions: the TigraTest^® SARS-CoV-2 kit is a specific and sensitive tool for the assessment of T-cell immunity to the SARS-CoV-2 virus, which can also be used for vaccinated individuals. The kit may be used in clinical practice for comprehensive assessment of immunity to SARS-CoV-2.

Recombinant tissue plasminogen activator (international nonproprietary name — alteplase) which was developed by «GENERIUM» (Russia) and received a marketing authorisation in Russia is completely analogous to Actilyse® which is used to treat medical conditions accompanied by thrombosis, such as acute myocardial infarction, pulmonary embolism, and ischemic stroke. The aim of the study was to carry out a comprehensive comparison of physico-chemical and biological properties of Revelyse® and the reference product Actilyse® in order to assess their biosimilarity. Materials and Methods: comparative peptide mapping and determination of comparability of chromatographic profiles of tryptic hydrolysates was performed using RP-HPLC and massspectrometry; the molecular weight distribution was determined by mass-spectrometry and polyacrylamide gel electrophoresis (Laemmli method). The purity and homogeneity of products as well as the content of related impurities (oligomers and fragments) were determined using gel filtration; N-glycosylation profile was analysed by hydrophilic HPLC, total sialic acid was quantified by the Svennerholm resorcinol method. Protein binding to fibrin and human fibrinogen was assessed by surface plasmon resonance, and the specific activity was compared by fibrin clot lysis. Results: the research demonstrated a complete overlap of the products’ peptide maps, which indicates the identity of аlteplase amino acid sequences in the two medicines being compared. The authors of the study also determined the molecular weight and the content of the intact single-stranded form of the protein, and quantified post-translational modifications, the content of sialic acids and neutral sugars. The analysis of the N-glycosylation profile revealed insignificant differences in the percentage of multiantenna complex glycans. The specificity of alteplase was evaluated by analysing the formation of protein complexes with natural alteplase ligands – fibrin and plasminogen activator inhibitor-1, but no significant differences were found. The comparison of specific activation of plasminogen fibrinolytic activity was performed based on the results of the assay analysing the fibrin clot lysis rate, and it demonstrated comparability of Revelyse® and Actilyse®. Conclusions: comparative experimental studies have shown no differences in the structure, charge distribution heterogeneity, impurities content, and specific activity of alteplase as a component of Revelyse® and the reference product Actilyse®, which leads to the conclusion that they are similar in terms of physicochemical and biological properties.

Determination of T-cell immune response to SARS-CoV-2 is important both for diagnosis of the disease in symptomatic patients, and for determination of the total number of people who have had the disease, including its asymptomatic form. In addition, these assays are efficient for assessing the immune response after vaccination, as well as immunity levels in risk groups and in convalescent patients. The most promising method of T-cell immune response assessment is an ELISPOT-based assay measuring the release of interferon-gamma (IGRA) after stimulation with coronavirus-specific antigens. The present review analyses the prospects for using the ELISPOT technological platform in the clinical laboratory setting when dealing with the new coronavirus infection COVID-19, given specific aspects of the immune response. The review summarises data from articles published in peer-reviewed journals, preprints of articles available at arXiv resources, and information that some leading immunologists shared with the authors during private discussions. It has been shown that the introduction of B- and T-cell ELISPOT assays will make it possible to monitor the immunological status of patients, select a treatment strategy, identify the most vulnerable populations, carry out comprehensive assessment of vaccines during the development, clinical trials and implementation stages. The paper discusses the issues of maintaining T-cell immunity in the blood of people who have had HCoV, SARS, MERS, and COVID-19 coronavirus infections. It also discusses the advantages of the T-cell ELISPOT assay over serological tests as regards epidemiological assessment of the prevalence of the new coronavirus infection, and clinical trials of COVID-19 vaccines. Biotechnology companies have a ready-made technological platform for the development and industrial-scale production of ELISPOT kits, and this platform is easily adaptable to specific types of assays and pathogens. The paper supports the need to develop vaccines that would stimulate both cellular and humoral immune responses, and raises the question of the protective potential of cross-immunity acquired before the COVID-19 pandemic.

Mucopolysaccharidosis type VI (Maroteaux–Lamy syndrome) is an orphan genetic disease caused by deficiency of the lysosomal enzyme arylsulfatase B (ASB). The need to develop a highly productive cell line for the production of recombinant ASB, is behind the concept and relevance of this study. The most promising approach seems to be the development of CHO producer cell lines coexpressing the target ASB enzyme and an auxiliary formylglycine-generating enzyme (FGE). At the same time, it is important from a practical perspective to have the possibility of cultivating producer cell lines as suspensions free of serum or other components of animal origin. The aim of the study was to develop highly productive cell lines for the production of recombinant ASB by coexpression of the auxiliary FGE. Materials and methods: a suspension CHO cell line was used in the study. CHO cells were transfected by electroporation using the MaxCyte STX system. Monoclonal cell lines were obtained with the help of the Cell Metric system. Enzyme-linked immunosorbent assay was used for determination of ASB concentration in the culture fluid. Culture fluid samples were analysed using polyacrylamide gel electrophoresis and Western blotting. The mRNA level was measured by real-time polymerase chain reaction. Results: producer cell lines coexpressing the target ASB enzyme and auxiliary FGE were obtained. An increase in the yield of the active target ASB enzyme from 2 to 100 mg/L was achieved by selecting the optimal ratio of plasmids during transfection. The highest yield of the target ASB enzyme was achieved at the 90:10 ratio (%) of plasmids encoding the ASB and FGE genes, respectively. Conclusions: the authors developed highly productive cell lines for the production of recombinant ASB, which coexpress the target and auxiliary enzymes. The coexpression of ASB and FGE improves the growth and production characteristics of the cell line, probably due to the modification of the ASB active site. The obtained results will help resolve the problem of low enzyme yield, which is typical of this class of medicines.

The article discusses the results of a comparative phase III clinical trial of the efficacy and safety of the biosimilar Complarate (CPR; JSC Generium, Russia) and the reference drug Actemra (ACT; F. Hoffmann-La Roche Ltd., Switzerland) to assess their equivalence in patients with rheumatoid arthritis, RA (NCT06475508 clinicaltrials.gov).Materials and methods. Male and female patients aged 18–75 years with RA with moderate to high disease activity and insufficient response to methotrexate (MTX) monotherapy and/or poor tolerability of MTX and/or insufficient response or intolerance to other standard DMARDs in combination with or without MTX were enrolled in the study. 464 (89.4%) patients were randomized in a 2:1 ratio into two groups. The study and the reference drug were administered as an intravenous infusion at a dose of 8 mg/kg once every 4 weeks. The primary endpoint was the proportion of patients with an ACR20 after 24 weeks of therapy.Results and discussion. The proportion of responders in CPR group was 91.2%, and in ACT group – 90.7% (p = 0.866). The difference between the groups was 0.5% (95% CI: -5,2%−6,1%), which is fully within the declared boundaries of recognition of therapeutic equivalence. Comparability of the biosimilar CPR and the reference drug ACT is also confirmed by the results of secondary efficacy endpoints: the proportion of patients with ACR50/70, dynamics of the DAS28, SDAI, CDAI, the functional activity of patients (HAQ), laboratory parameters of inflammatory activity (ESR and CRP). Comparability of the study and the reference drugs is also demonstrated by the results of the safety analysis.Conclusion. Based on the results of the clinical study, it has been proven that CPR (JSC Generium, Russia) is a biological analogue of ACT (F. Hoffmann-La Roche Ltd., Switzerland).

Introduction. The SARS-CoV-2 coronavirus pandemic has been a major challenge for all areas of medical science, causing a surge of new developments in various fields ranging from diagnostic techniques to therapeutic and preventive approaches. Intranasal vaccination is an innovative approach to immunization against SARS-CoV-2, which has attracted the attention of many drug developers. Dynamics of blood virus-neutralizing antibodies (VNAs) in recovered COVID-19 patients or vaccinated healthy volunteers is one of the objective parameters for assessing vaccine immunological efficacy, which requires high standards of bioanalytical techniques within the framework of clinical trials. Immunogenicity data on the two-component Salnavak®(intranasal) and Gam-COVID-Vac®(intramuscular) vaccination obtained in randomized double-blind multicenter phase 3 clinical trial interim analysis are presented. The objective of the study was to assess immunogenicity of intranasal and intramuscular vaccination against COVID-19 using a neutralization reaction with pseudoviral particles and HEK293T-hACE2 cell culture.Materials and methods.A total of 137 healthy volunteers with a baseline anti-RBD IgG level not exceeding 100 BAU/ml received immunization by a two-component (Ad26 and Ad5 based) intranasal or intramuscular vaccine administered on day 1 and day 21. Immunogenicity level based on VNA quantitative analysis using a neutralization reaction with pseudoviral particles and a HEK293T-hACE2 cell culture as well as to SARS-CoV-2 S-protein receptor-binding domain (anti-RBD) IgG antibodies on days 21 and 42 after administration of component I was assessed.Results.The geometric mean VNA titer against SARS-CoV-2 on day 42 was 238.34±3.93 and 616.94±3.73 in the Salnavac®and Gam-COVID-Vac®groups, respectively. Trial data shows sufficient immunological efficacy of both intramuscular and intranasal vaccines based on a high protection level at VNA titer of more than 100 while using the pseudoviral neutralization method. The geometric mean of the anti-RBD IgG level by day 42 was 131.22±3.91 and 782.03±3.04 in the Salnavac®and Gam-COVID-Vak®groups, respectively. A direct moderate correlation was shown between VHA and anti-RBD IgG.Conclusion. Neutralization reaction using pseudoviral particles was successfully validated and used to determine the VNA titer during clinical trial. Trial interim data revealed that intranasal vaccine Salnavac®vs intramuscular vaccine Gam-COVID-Vak®resulted in lower but sufficient stringency of humoral immunity.