According to the lasting serological investigations of patients with rubella and measles, a major factor that determines the resistance to the infections is specific antibodies, that are still circulating in blood of recovered persons during their life. Since vaccinated people are also included in this concept, serological monitoring of people different ages who get vaccinated against rubella and measles is conducted in Russia. However the discrepancy between specific immunity intensity and the measles incidence was showed last years. Using “Vector Best” kits, the study of the anti-measles and antirubella population immunity in scale of age: under 1 year, 1–2 years, 3–6 years, 7–14 years, 15–17 years, 18–30 years, 31–40 years, 41–50 years, and 51–60 years was carried out in Moscow and Moscow region in 2013 (period of unfavorable epidemic situation). The serum probes were obtained from 654 random healthy donors and 646 patients with serologically confirmed measles infection. As a result, gradual increase of percentage of people with protective antibodies to rubella and measles have been demonstrated: 81.3% donors aged 7–14 years were protected from measles and more than 90% — from rubella. Moreover, percentage of individuals who have had immunity to rubella were the same in adults too. The most marked increase of percentage of seronegative persons to measles virus (40% and more) was in age from 18 to 30 years, and in groups over the age 40 years old protection reaches 85–95%. Comparison between percentage of measles patients different ages and percentage of persons with protective antibodies in serum have demonstrated significant negative correlation between measles prevalence and the level of specific antibody in population (r = –0.76). According to the results, increase (to 28%) and decrease (to 2.9%) of measles patients aged 18 to 30 and 51 to 60 years are based on decrease (to 55%) and increase (to 95%) of persons with protective immunity, respectively. Results of analysis of measles prevalence in different ages have demonstrated, that among adult measles patients (18–50 years) 14.5% responded on infection by secondary immune response; among children and teenagers there were no such patients, that proves the significant effectiveness of prophylactic vaccines.
An issue of eradicating measles and rubella virus-induced infections currently remains unresolved, despite existing effective methods for specific prophylaxis and WHO’s commitment to a mass vaccination policy. While improving epidemic situation, analysis of new challenges, such as measles incidence in adults, especially in adults vaccinated in childhood, is of particular interest. The aim of the study was to analyze serum measles and rubella virus-specific IgG antibodies in young healthy people and estimate antigen-specific cellular immune response in seronegative subjects. There were examined 100 healthy adults aged 18–30 years old. Level of serum specific IgG was measured by ELISA (Vector-Best, Russia). Antigen-specific cellular immune response was assessed by magnitude of surface CD107a expression on CD8hi T cells challenged by measles and rubella virus-derived antigens. It was found that average level of antibodies against rubella virus comprised 175.5 IU/ml, 49% of which recovered after rubella, 46% were vaccinated, whereas 5% subjects contained no virus-specific antibodies. In addition, mean level of anti-measles virus antibodies was below protective magnitude, among which 1% subjects recovered after measles, 31% displayed post-vaccination immunity, 55% subjects were seronegative, and 13% had equivocal levels of specific antibodies. Thus, 68% subjects were unprotected against measles virus based on the level of serum virus-specific antibodies. Moreover, 40 out of 68 subjects were vaccinated against measles in childhood. Additional screening adult subjects for intensity of measles and rubella virus-specific cellular immunity demonstrated that 57.37% of them contained peripheral blood CD8 T cells against measles virus and 59.01% — against rubella virus. Further analysis allowed to identify 4 subgroups displaying: 1) high level of virus-specific antibodies and T cells; 2) neither antibodies nor specific T-cells reaching as low as 20% of baseline group; 3) high antibody level combined with low amount of specific T cells; and 4) low antibody level combined with high level of specific T cells. thus, it may be assumed that cellular and humoral immune arms are maintained independently and being active for a long term after vaccination. Preserving a specific T-cell immunity seems to provide protection against infection, thereby accounting for the lack of measles manifestation in all seronegative subjects.
The new coronavirus SARS-CoV-2 has become a global challenge to medicine and, in particular, laboratory diagnostics. The study of the antibodies’ level to SARS-CoV-2 can be used as a confirmation test in the diagnosis of a disease, but it becomes of paramount importance in assessing population immunity resulting from a disease or vaccination, as well as in selection of convalescent plasma donors. The kits developed in our country and abroad for detecting antibodies to the SARS-CoV-2 virus differ both in the methods of testing and in the used coronavirus antigens to which the antibodies are directed. The aim of this study was to compare the diagnostic sensitivity and specificity of five kits for the detection of IgG antibodies to the SARS-CoV-2 virus, based on different diagnostic methods. Serum samples from 137 COVID-19 convalescents and 166 donors of blood and its components were examined. The control group consisted of 50 blood sera collected at the beginning of 2019 and 19 sera collected in 2018 (before the advent of the SARS-CoV-2 virus) and stored at -70 °C. Testing was carried out in analytical systems: rapid test “COVID-19 IgM/IgG Rapid Test (Colloidal Gold)” (China), on an automatic immunochemical analyzer Abbott Architect™ i2000 and kit “SARS-CoV2-IgG” (Abbot, Chicago , IL USA), by the chemiluminescence method using an automatic analyzer of the CL series and kits of the “Mindray” company (China) “SARS-CoV-2 IgM” and “SARS-CoV-2 IgG” and by the enzyme immunoassay method on the kits of the companies “Diagnostic Systems” Ltd (Russia, Nizhny Novgorod) “DS-IFA-ANTI-SARS-CoV-2-G”, “Xema” Ltd (Federal State Budgetary Institution “National Medical Research Center of Hematology” of the Ministry of Health of Russia) “SARS-CoV-2-IgG-IFA” and “Vector-Best” CJSC (Russia, Novosibirsk)” SARS-COV-2-IgM-IFA-BEST” and “SARS-COV-2-IgG-IFABEST”. When comparing the results of testing 137 plasma samples on the Vector-Best and Mindray kits for IgG antibodies, 127 samples were positive, 7 samples were negative on both kits, the discrepancy was 2.2%. In the study of IgM antibodies, 32.1% were positive, and 52.6% were negative in both kits. The discrepancy rate was 15.3%. Out of 166 samples, 1 serum (0.6%) was negative in 5 kits. On the Mindray kit, IgG antibodies to the antigens of the SARS-CoV-2 virus were detected in 165 samples (99.4%), on Vector-Best – in 164 sera (98.8%), on Diagnostic systems – in 151 (90.96%), on Xema – in 154 (92.8%), and on Abbott – in 155 samples (93.4%). At the same time, 135 (81.33%) samples were positive in all kits, while 30 samples had discordant results (18.07%), and in 9 sera, specific IgG was not detected in 2 or more kits. ROC analysis revealed a high diagnostic value of all tested kits (AUC from 0.908 to 0.998), which indicates a high quality of the separation model of positive and negative samples (p < 0.001). With the cut-off set by the manufacturers, the sensitivity and specificity ranged from 82.8% and 93.3% for the Diagnostic Systems kit to 99.4% and 95.8% for the VectorBest kit. The calculated correlation coefficients were higher between kits with a similar composition of the antigen used in the kits; therefore, it is better to monitor the dynamics of antibodies by diagnostic kits from the same manufacturer.
Резюме. Введение. Реализация программы ВОЗ по элиминации кори дала существенные результаты, но в последние годы вновь отмечается рост заболеваемости этой инфекцией. Так, по данным ВОЗ, в 2019 г. случаев заболевания корью в мире было в 3 раза больше, чем в 2018 г. При расследовании вспышек кори среди заболевших, помимо непривитых, выделяется значительная группа привитых в детстве взрослых. Целью настоящей работы было исследование особенностей гуморального противокоревого иммунитета у взрослых больных корью и привитых от этой инфекции. Материалы и методы. Были обследованы 50 больных корью взрослых в возрасте от 20 до 55 лет. Диагноз был подтвержден клинически и лабораторно по наличию противокоревых IgM-антител. Вторую группу составили 50 серонегативных к кори, условно здоровых взрослых, сопоставимых по возрасту, привитых культуральной живой коревой вакциной (Микроген, Россия). Кровь из локтевой вены в количестве 4 мл брали на 6±1 день от появления сыпи у больных и через 6 недель после вакцинации у привитых. Специфические антитела к кори и их авидность определяли методом ИФА с помощью коммерческого набора Avidity: Anti-Measles Viruses ELISA/IgG (Euroimmun, Германия). Результаты. Показано, что люди в возрасте 20-35 лет чаще болеют корью, чем более взрослые лица. И именно в этой возрастной группе чаще встречаются серонегативные к кори здоровые индивиды. Среди привитых у 44% был установлен первичный тип иммунного ответа на вакцинацию, а у 56% -вторичный тип, тогда как среди заболевших корью первичный иммунный ответ зафиксирован у 4%, а вторичный -у 66%, что следует из спектра субклассов специфических IgG и их авидности. Вторичный тип иммунного ответа свидетельствует о том, что эти люди, по-видимому, были привиты в детстве от кори, но потеряли с возрастом долгоживущие плазматические клетки, синтезирующие защитные антитела. При сопоставлении параметров специфического гуморального иммунитета в группах с острой коревой инфекцией (6-й день от появления высыпаний) и ранних реконвалесцентов (через 3 недели после появления сыпи) показано, что у ранних реконвалесцентов в три раза возросло количество специфических IgG (p < 0,01) по сравнению с лицами с острой инфекцией. Уровень специфических IgA, напротив, снизился с 73,44 (69-75,3) Ме/мл до 48,64 (45-56,4) Ме/мл, оставаясь все еще очень высоким. При этом спектр субклассов специфических IgG изменился с первичного иммунного ответа (высокие IgG3 и низкие IgG1) на вторичный (низкие IgG3 и высокие IgG1), что типично для ответа формирующихся клеток памяти.
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