BackgroundNijmegen breakage syndrome (NBS) is a combined primary immunodeficiency with DNA repair defect, microcephaly, and other phenotypical features. It predominantly occurs in Slavic populations that have a high frequency of carriers with the causative NBN gene c.657_661del5 mutation. Due to the rarity of the disease in the rest of the world, studies of NBS patients are few. Here, we report a prospective study of a cohort of Russian NBS patients.Methods35 Russian NBS patients of ages 1–19 years, referred to our Center between years 2012 and 2016, were prospectively studied.ResultsDespite the fact that in 80% of the patients microcephaly was diagnosed at birth or shortly thereafter, the average delay of NBS diagnosis was 6.5 years. Though 80% of the patients had laboratory signs of immunodeficiency, only 51% of the patients experienced significant infections. Autoimmune complications including interstitial lymphocytic lung disease and skin granulomas were noted in 34%, malignancies—in 57% of the patients. T-cell excision circle (TREC)/kappa-deleting recombination excision circle (KREC) levels were low in the majority of patients studied. Lower KREC levels correlated with autoimmune and oncological complications. Fifteen patients underwent hematopoietic stem cell transplantation (HSCT), 10 of them were alive and well, with good graft function. Three patients in the HSCT group and five non-transplanted patients died; tumor progression being the main cause of death. The probability of the overall survival since NBS diagnosis was 0.76 in the HSCT group and 0.3 in the non-transplanted group.ConclusionBased on our findings of low TRECs in most NBS patients, independent of their age, TREC detection can be potentially useful for detection of NBS patients during neonatal screening. KREC concentration can be used as a prognostic marker of disease severity. HSCT is a viable treatment option in NBS and should be especially considered in patients with low KREC numbers early on, before development of life-threatening complications.

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Резюме. Первичные иммунодефициты (ПИД), тяжелый комбинированный иммунодефицит (ТКИН) и Х-сцепленная агаммаглобулинемия, характеризуются отсутствием функциональных Ти В-лимфоцитов соответственно. Без своевременной ранней диагностики и лечения дети с ПИД страдают от инфекционных заболеваний с тяжелым течением, что приводит к их инвалидизации или смерти. Цель: разработать и апробировать на группе детей с верифицированными диагнозами ТКИН и Х-сцепленной агаммаглобулинемией простую, недорогую, высокопропускную методику на основе количественного определения молекул ДНК TREC и KREC с помощью ПЦР в режиме реального времени. В настоящем исследовании мы разработали и валидировали метод проведения мультиплексной полимеразной цепной реакции в режиме «реального времени» для количественного анализа молекул ДНК TREC и KREC. Нами было показано, что в области концентраций от 10 9 коп/мл до 5 × 10 4 коп/ мл для всех мишеней наблюдается линейный диапазон изменения Сt в зависимости от концентрации с коэффициентом корреляции R 2 не хуже 0,98. Наименьшее количество копий, надежно детектиру-Gordukova M.A. et al. Гордукова М.А. и др. Medical Immunology (Russia)/Meditsinskaya Immunologiya Медицинская Иммунология емых в одной ПЦР реакции объемом 25 мкл, было: 10 для TREC, 5 для KREC и 5 для внутреннего контроля-локуса IL17RA. Нами определены референсные значения для количества TREC и KREC в цельной крови в зависимости от возраста в группе из 29 мальчиков и 27 девочек с нормальными иммунологическими параметрами. Были определены граничные значения для содержания TREC и KREC в сухих пятнах крови в зависимости от метода экстракции ДНК. Предложенная методика показала 100% диагностическую чувствительность и специфичность на исследуемой выборке. Метод может быть предложен как скрининговый для диагностики ТКИН и Х-сцепленной агаммаглобулинемии как в цельной крови, так и в сухих пятнах крови. Требуется дальнейшая апробация методики на выборках большего объема.

Primary immunodeficiency diseases (PID) is a heterogeneous group of disorders caused by genetic defects of the immune system, which manifests clinically as recurrent infections, autoimmune diseases, or malignancies. Early detection of other PID remains a challenge, particularly in older children due to milder and less specific symptoms, a low level of clinician PID awareness and poor provision of hospital laboratories with appropriate devices. T-cell recombination excision circles (TREC) and kappa-deleting element recombination circle (KREC) in a dried blood spot and in peripheral blood using real-time polymerase chain reaction (PCR) are used as a tool for severe combined immune deficiency but not in PID. They represent an attractive and cheap target for a more extensive use in clinical practice. This study aimed to assess TREC/KREC correspondence with lymphocyte subpopulations, measured by flow cytometry and evaluate correlations between TREC/KREC, lymphocyte subpopulations and immunoglobulins. We carried out analysis of data from children assessed by clinical immunologists at Speransky Children’s Hospital, Moscow, Russia with suspected immunodeficiencies between May 2013 and August 2016. Peripheral blood samples were sent for TREC/KREC, flow cytometry (CD3, CD4, CD8, and CD19), IgA, IgM, and IgG analysis. A total of 839 samples were analyzed for using TREC assay and flow cytometry and 931 KREC/flow cytometry. TREC demonstrated an AUC of 0.73 (95% CI 0.70–0.76) for CD3, 0.74 (95% CI 0.71–0.77) for CD4 and 0.67 (95% CI 0.63–0.70) for CD8, respectively, while KREC demonstrated an AUC of 0.72 (95% CI 0.69–0.76) for CD19. Moderate correlation was found between the levels of TREC and CD4 (r = 0.55, p < 0.01) and KREC with CD19 (r = 0.56, p < 0.01). In this study, promising prediction models were tested. We found that TREC and KREC are able to moderately detect abnormal levels of individual lymphocyte subpopulations. Future research should assess associations between TREC/KREC and other lymphocyte subpopulations and approach TREC/KREC use in PID diagnosis.

Sanger sequencing is a common method of reading DNA sequences. It is less expensive than high-throughput methods, and it is appropriate for numerous applications including molecular diagnostics. However, sequencing mixtures of similar DNA of pathogens with this method is challenging. This is important because most clinical samples contain such mixtures, rather than pure single strains. The traditional solution is to sequence selected clones of PCR products, a complicated, time-consuming, and expensive procedure. Here, we propose the base-calling with vocabulary (BCV) method that computationally deciphers Sanger chromatograms obtained from mixed DNA samples. The inputs to the BCV algorithm are a chromatogram and a dictionary of sequences that are similar to those we expect to obtain. We apply the base-calling function on a test dataset of chromatograms without ambiguous positions, as well as one with 3–14% sequence degeneracy. Furthermore, we use BCV to assemble a consensus sequence for an HIV genome fragment in a sample containing a mixture of viral DNA variants and to determine the positions of the indels. Finally, we detect drug-resistant Mycobacterium tuberculosis strains carrying frameshift mutations mixed with wild-type bacteria in the pncA gene, and roughly characterize bacterial communities in clinical samples by direct 16S rRNA sequencing.