A novel high-resolution melting analysis strategy for detecting cystic fibrosis-causing variants.

Cystic fibrosis (CF), an autosomal recessive disease, is caused by variants in both alleles of the CF transmembrane conductance regulator (CFTR) gene. A new assay based on allele-specific polymerase chain reaction and high-resolution melting analysis was developed for the detection of 18 CF-causing CFTR variants previously identified in Cuba and Latin America. The assay is also useful for zygosity determination of mutated alleles and includes internal controls. The reaction mixtures were normalized and evaluated using blood samples collected on filter paper. The evaluation of analytical parameters demonstrated the specificity and sensitivity of the method to detect the included CFTR variants. Internal and external validations yielded a 100% agreement between the new assay and the used reference tests. This assay can complement CF newborn screening not only in Cuba but also in Latin America.

Retos del Sistema Nacional de Salud en los tiempos pos-COVID / Challenges of the National Health System in post-COVID times

El Sistema Nacional de Salud de Cuba se fundó en el año 1961 y es una entidad dependiente del Ministerio de Salud Pública de Cuba. Este constituye una prioridad nacional, tiene carácter universal, gratuito y se basa en el modelo del médico de familia, con un enfoque clínico, epidemiológico y social de los problemas sanitarios. Se sustenta en siete principios que expresan el derecho del pueblo a la salud, con responsabilidad del Estado, y las prácticas de salud se sostienen sobre una base científica sólida con acciones preventivas. En el año 2019, una epidemia azotó a la mayoría de los países del mundo (la COVID-19), entre ellos, Cuba. Ello conllevó a que los profesionales de la salud asumieran retos importantes ante una situación de salud sin precedentes. Este trabajo se refiere a los retos asumidos, principalmente, después de la COVID-19.

The Cuban National Health System was founded in 1961 and is an entity dependent on the Cuban Ministry of Public Health. This constitutes a national priority, is universal, free and is based on the family doctor model, with a clinical, epidemiological and social approach to health problems. It is supported in seven principles that express the right of the people to health, with responsibility of the State and the health practices are sustained on a solid scientific basis with preventive actions. In 2019, an epidemic hit most of the countries in the world (COVID-19), including Cuba. This led health professionals to assume important challenges in order to face an unprecedented health situation. This work refers to the challenges assumed, mainly, after COVID-19.

Evaluación de estuches de PCR-tiempo real para detección de virus del papiloma humano de alto riesgo / Evaluation of real-time PCR kits to detect high-risk human papillomavirus

RESUMEN Introducción: El empleo de técnicas moleculares para el diagnóstico de virus del papiloma humano de alto riesgo oncogénico (VPH-AR) es crucial para la detección precoz del cáncer cervicouterino. Objetivo: Evaluar el desempeño analítico de dos estuches de PCR-tiempo real, comercializados por el Centro de Inmunoensayo de Cuba, para detectar VPH-AR. Métodos: Se utilizaron dos paneles de ADN de muestras cervicouterinas: uno con 150 muestras, para validar el estuche SUMASIGNAL HPV 16/18, el proceso de extracción de ADN y su utilidad como prueba cuantitativa, y otro con 163 muestras para evaluar el estuche HPV 13+2. Se determinó la utilidad clínica del estuche HPV 13+2 en 55 muestras cervicovaginales autocolectadas. Se calcularon los indicadores de desempeño analítico de ambos estuches con respecto a pruebas de referencia. Resultados: Los indicadores de desempeño para SUMASIGNAL HPV 16/18 fueron excelentes (> 95 %), concordancia 96 %, índice kappa=0,93 [0,85-1,01]. La extracción de ADN mostró 100 % de especificidad clínica y analítica y 95 % de sensibilidad analítica. Se obtuvo buena correlación con la prueba de referencia cuantitativa (r = + 0,688). El estuche HPV 13+2 tuvo especificidad y sensibilidad clínicas del 100 %, la especificidad analítica fue del 84 % debido a reactividad cruzada con otros VPH-AR. Su aplicación clínica reveló alta frecuencia de infección (41,8 %): 23,6 % con VPH-AR, particularmente en mujeres jóvenes (50 %). La muestra autocolectada resultó útil (100 %). Conclusión: Los ensayos evaluados mostraron altos estándares de calidad, lo que permitiría su uso con una cobertura nacional en una plataforma tecnológica disponible para todo el país.

ABSTRACT Introduction: The use of molecular techniques for the diagnosis of high oncogenic risk human papillomavirus (hrHPV) is crucial for the early detection of cervical cancer. Objective: To evaluate the analytical performance of two real-time PCR kits, commercialized by the Cuban Immunoassay Center, to detect hrHPV. Methods: Two DNA panels from cervical samples were used: one with 150 samples to validate the SUMASIGNAL HPV 16/18 kit, the DNA extraction process and its usefulness as a quantitative test; and another with 163 samples to evaluate the HPV 13+2 kit. The clinical utility of the HPV 13+2 kit was determined in 55 self-collected cervicovaginal samples. The analytical performance indicators of both kits were calculated with respect to reference tests. Results: Performance indicators for SUMASIGNAL HPV 16/18 were excellent (>95%), concordance 96%, kappa index=0.93 [0.85-1.01]. DNA extraction showed 100% clinical and analytical specificity and 95% analytical sensitivity. Good correlation was obtained with the quantitative reference test (r = + 0.688). The HPV 13+2 kit had 100% clinical specificity and sensitivity, analytical specificity was 84% due to cross-reactivity with other hrHPVs. Its clinical application revealed a high frequency of infection (41.8%): 23.6% with hrHPV, particularly in young women (50%). The self-collected sample was viable (100%). Conclusion: The assays evaluated showed high quality standards, which would allow their use with national coverage in a technological platform available for the whole country.

Evaluación del desempeño clínico del ensayo SUMASIGNAL VHC para la detección del ARN del virus de la hepatitis C

RESUMEN Introducción: La detección y cuantificación del genoma del virus de la hepatitis C (ARN-VHC), mediante la transcripción inversa-PCR en tiempo real (RT-qPCR), es vital para el diagnóstico y seguimiento del tratamiento antiviral de los pacientes con hepatitis C. Objetivo: Evaluar los indicadores de desempeño clínico como la especificidad, sensibilidad y reproducibilidad del ensayo SUMASIGNAL VHC, comercializado por el Centro de Inmunoensayo (Cuba), tomando como técnica de referencia la prueba Artus® HCV RG RT-qPCR. Métodos : Se empleó un panel conformado por 70 muestras de suero: 46 ARN-VHC positivas, 12 ARN-VHC negativas y 12 positivas a marcadores moleculares de otros virus. El coeficiente de correlación de Pearson (r) y la prueba de Bland-Altman, se utilizaron para comparar las cargas virales del VHC, obtenidas por las técnicas SUMASIGNAL VHC y la de referencia; las que fueron expresadas en logaritmo en base 10 (log10) UI/mL. Los valores de p< 0,05 se consideraron estadísticamente significativos. Resultados: La sensibilidad y especificidad clínica del SUMASIGNAL VHC fue 100 %; mientras que no se detectó reactividad cruzada con los otros virus evaluados. Se demostró que el ensayo en cuestión, tuvo una correlación buena (r= 0,89) y fuerte concordancia (media= -0,01 Log10 UI/mL) con la prueba de referencia (p< 0,0001). La reproducibilidad de la cuantificación del ARN-VHC en dos momentos diferentes, con la prueba SUMASIGNAL VHC mostró una correlación excelente (r= 0,97; p< 0,0001). Conclusiones: El ensayo SUMASIGNAL VHC proporciona datos válidos, reproducibles y técnicamente confiables para realizar el diagnóstico específico del VHC, incluso constituye una herramienta útil para monitorear la carga viral de este agente en el Sistema Nacional de Salud Cubano.

ABSTRACT Introduction: Detection and quantification of the hepatitis C virus genome (HCV RNA) by real time reverse transcription PCR (RT-qPCR) are vital for the diagnosis and antiviral treatment follow-up of hepatitis C patients. Objective: Evaluate the clinical performance of the SUMASIGNAL HCV assay for quantification of HCV viral load. Methods: A panel was formed with 70 serum samples: 46 HCV RNA positive, 12 HCV RNA negative and 12 positive for molecular markers of other viruses. Pearson's correlation coefficient (r) and the Bland-Altman plot were used to compare the HCV viral loads obtained by SUMASIGNAL HCV techniques with reference values, which were expressed as base 10 logarithm (log10) UI/ml. Values of p <0.05 were considered statistically significant. Results: The clinical sensitivity and specificity of SUMASIGNAL HVC were 100%, and no cross-reactivity was detected with the other viruses evaluated. The study assay exhibited a good correlation (r= 0.89) and strong concordance (mean= -0.01 Log10 UI/ml) with the reference test (p< 0.0001). Reproducibility of the HCV RNA quantification with the SUMASIGNAL HCV test at two different moments displayed an excellent correlation (r= 0.97; p< 0.0001). Conclusions: The SUMASIGNAL HVC assay provides valid, reproducible and technically reliable data for specific HCV diagnosis. It is also a useful tool to monitor the viral load of this agent in the Cuban National Health System.

Evaluación de una reacción en cadena de la polimerasa en tiempo real simple y rápida para la cuantificación del ADN del virus de la hepatitis B / Evaluation of a simple and fast real time polymerase chain reaction assay for quantification of hepatitis B virus DNA

Introducción: Los ensayos para cuantificar el ADN del virus de la hepatitis B (VHB) o carga viral son imprescindibles en el diagnóstico y en el seguimiento de los pacientes con hepatitis B crónica; de ahí que estén disponibles estuches diagnósticos para esta función. En el presente estudio se muestra la validación de SUMASIGNAL VHB (un paso), el cual es un sistema de reacción en cadena de la polimerasa en tiempo real (RCP-TR) para la cuantificación del genoma del VHB, propuesto por el Centro de Inmunoensayo. Objetivo: Evaluar el desempeño analítico de SUMASIGNAL VHB (un paso). Métodos: Se utilizó un panel de 80 muestras de suero bien caracterizadas y el Tercer Estándar Internacional de la OMS para las técnicas de amplificación de ácidos nucleicos del virus de la hepatitis B. Se determinaron las características del ensayo como especificidad clínica, especificidad analítica (reactividad cruzada), rango lineal o linealidad y exactitud, precisión intraensayo y comparación con un ensayo de referencia. Resultados: La especificidad analítica y clínica fue del 100 por ciento. Al evaluar la linealidad y exactitud con un estándar de referencia de la OMS, se obtuvo que la totalidad de las diferencias entre los Log10 del valor obtenido y el de referencia resultaron inferiores a 0,5 Log10 (r= 0,9977 y r2= 0,9954). Además, se obtuvieron bajos coeficientes de variación intraensayo. La evaluación comparativa con el estuche comercial Artus HBV RG PCR kit mostró una correlación fuerte (r= 0,8882). Conclusiones: SUMASIGNAL VHB (un paso) es un ensayo fácil de realizar manualmente, es rápido e incluye reactivos de extracción de ácidos nucleicos. Teniendo en cuenta la validez del método para el uso previsto, puede ser recomendado para su introducción en el diagnóstico, la vigilancia y la indicación de tratamiento en los pacientes con hepatitis B crónica(AU)

Introduction: Assays to quantify hepatitis B virus (HBV) DNA or viral load are indispensable for the diagnosis and follow-up of patients with chronic hepatitis B, hence the availability of diagnostic kits for this purpose. The present study deals with the validation of HBV SUMASIGNAL (one step), a real time polymerase chain reaction (RT-PCR) system for quantification of the HBV genome proposed by the Immunoassay Center. Objective: Evaluate the analytical performance of HBV SUMASIGNAL (one step). Methods: Use was made of a panel of 80 well characterized serum samples and the Third WHO International Standard for hepatitis B virus nucleic acid amplification techniques. Determination was performed of assay characteristics such as clinical specificity, analytical specificity (cross-reactivity), linear range or linearity and accuracy, intra-assay precision and comparison with a reference assay. Results: Analytical and clinical specificity was 100 percent. Evaluation of linearity and accuracy with a WHO reference standard revealed that all the differences between the log10 of the value obtained and the reference value were lower than 0.5 log10 (r= 0.9977 and r2= 0.9954). The intra-assay variation coefficients obtained were low. Comparative evaluation with the commercial Artus HBV RG PCR kit showed a strong correlation (r= 0.8882). Conclusions: The assay HBV SUMASIGNAL (one step) is easy to conduct manually, fast and includes reagents for nucleic acid extraction. Based on the validity of the method for the use in mind, it may be recommended for incorporation into the diagnosis, surveillance and treatment of patients with chronic hepatitis B(AU)

Performance characteristics of a fast real-time PCR assay for hepatitis B virus DNA quantification.

Detection of hepatitis B virus (HBV) DNA is particularly important for detection of early acute and of occult HBV infection. On the other hand, HBV DNA detection and quantification are essential to diagnose and treat chronic HBV infection. In this study, we evaluated the performance of the real-time PCR SUMASIGNAL VHB (un paso) (Immunoassay Center, Cuba). The clinical and analytical specificity of the assay was 100%. Intra-assay and inter-assay coefficients of variation ranged from 0.50 to 2.53% and from 1.23 to 3.03%, respectively. A strong correlation (r=0.926; P<0.001) with the COBAS® AmpliPrep/COBAS® TaqMan® HBV Test, v2.0 (Roche Molecular Systems, Inc.) was obtained. The limit of detection using the third WHO international standard for HBV DNA was 377.47 IU/mL. The test was able to detect the most prevalent HBV genotypes (A-G) equally well. In conclusion, the SUMASIGNAL VHB (un paso) is a sensitive, specific, precise and accurate assay for the quantification of serum and plasma HBV DNA. Thus, this simple and fast real-time PCR test can be used as an aid in diagnosing an HBV infection and monitoring drug efficacy.

A simple, fast and inexpensive method for mutation scanning of CFTR gene.

BACKGROUND: Mutation scanning methods in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene may not distinguish between a Cystic Fibrosis (CF) causing mutation and a benign variant. We have developed a simple and fast method for scanning 14 selected CF-causing mutations which have high frequency in Latin America. METHODS: In a group of 35 samples coming from CF patients previously characterized and using two allele-specific real-time multiplex PCRs targeting wild-type and mutant alleles respectively, we detect the presence of mutations by analyzing the Ct variation. Twenty-five samples without mutations considered non-carrier samples, were also included in this study. High Resolution Melting Analysis (HRMA) was performed to confirm the result of the scanning method and in most cases allowed the genotype determination. RESULTS: The results validate this method for CF diagnosis. A least one CFTR gene mutation was detected in the samples of CF patients, as predicted by their ΔCt values. The ΔCt value also indicated the zygosity of the sample according to the distribution of CFTR gene mutations. In most cases, HRMA allowed the identification of the mutation(s), thereby confirming the efficiency of this scanning strategy. CONCLUSIONS: This strategy simplifies the detection of CF, reducing the analysis of 14 CF-causing mutations to two parallel reactions and making the procedure compatible with the analysis of a large number of samples. As the method is fast, inexpensive and highly reliable, it is advisable for scanning CFTR gene mutations in newborns, patients with a clinical suspicion of CF as well as in the preconception carrier screening.

HCV-specific immune responses induced by CIGB-230 in combination with IFN-α plus ribavirin.

AIM: To analyze hepatitis C virus (HCV)-specific immune responses in chronically infected patients under triple therapy with interferon-α (IFN-α) plus ribavirin and CIGB-230. METHODS: CIGB-230 was administered in different schedules with respect to IFN-α plus ribavirin therapy. Paired serum and peripheral blood mononuclear cells (PBMC) samples from baseline and end of treatment were analyzed. The HCV-specific humoral response was tested by enzyme-linked immunosorbent assay, neutralizing antibodies were evaluated by cell culture HCV neutralization assays, PBMC proliferation was assayed by carboxyfluorescein succinimidyl ester staining and IFN-γ secretion was assessed by enzyme-linked immunospot. Data on virological and histological response and their association with immune variables are also provided. RESULTS: From week 12 to week 48, all groups of patients showed a significant reduction in mean leukocyte counts. Statistically significant reductions in antibody titers were frequent, but only individuals immunized with CIGB-230 as early add-on treatment sustained the core-IgG response, and the neutralizing antibody response was enhanced only in patients receiving CIGB-230. Cell-mediated immune responses also tended to decline, but significant reductions in IFN-γ secretion and total absence of core-specific lymphoproliferation were exclusive of the control group. Only CIGB-230-immunized individuals showed de novo induced lymphoproliferative responses against the structural antigens. Importantly, it was demonstrated that the quality of the CIGB-230-induced immune response depended on the number of doses and timing of administration in relation to the antiviral therapy. Specifically, the administration of 6 doses of CIGB-230 as late add-on to therapy increased the neutralizing antibody activity and the de novo core-specific IFN-γ secretion, both of which were associated with the sustained virological response. CONCLUSION: CIGB-230, combined with IFN-α-based therapy, modifies the immune response in chronic patients. The study provides evidence for the design of more effective therapeutic vaccine interventions against HCV.

Generation of HIV-1 and Internal Control Transcripts as Standards for an In-House Quantitative Competitive RT-PCR Assay to Determine HIV-1 Viral Load.

Human immunodeficiency virus type-1 (HIV-1) viral load is useful for monitoring disease progression in HIV-infected individuals. We generated RNA standards of HIV-1 and internal control (IC) by in vitro transcription and evaluated its performance in a quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay. HIV-1 and IC standards were obtained at high RNA concentrations, without DNA contamination. When these transcripts were included as standards in a qRT-PCR assay, it was obtained a good accuracy (±0.5 log(10) unit of the expected results) in the quantification of the HIV-1 RNA international standard and controls. The lower limit detection achieved using these standards was 511.0 IU/mL. A high correlation (r = 0.925) was obtained between the in-house qRT-PCR assay and the NucliSens easyQ HIV-1 test (bioMerieux) for HIV-1 RNA quantitation with clinical samples (N = 14). HIV-1 and IC RNA transcripts, generated in this study, proved to be useful as standards in an in-house qRT-PCR assay for determination of HIV-1 viral load.

Long-term conservation of HCV RNA at 4 degrees C using a new RNA stabilizing solution.

Protecting RNA from degradation, whilst maintaining its biological activity, is essential in molecular biology. However, RNA is very sensitive to degradation by ribonucleases, especially at temperatures above 0 degrees C. The stability of RNA was examined at 4 degrees C and -20 degrees C, in a new stabilizing solution consisting of a low-molarity mixture of chaotropic agents guanidinium and ammonium thiocyanate, a buffer for pH stabilization, phenol, and yeast RNA. Two substrates were tested for storage: RNA in human plasma positive for hepatitis C virus (HCV) and naked RNA (purified from HCV positive human plasma or transcribed in vitro). Stability was followed by viral load estimation, using an in-house competitive RT-PCR assay. Naked RNA purified from human plasma positive for HCV was stable at 4 degrees C for at least 24 months. An RNA standard transcribed in vitro was still viable after 36 months of storage at 4 degrees C. Human plasma dilutions positive for HCV were stable for at least 5 months in this solution when stored at 4 degrees C. It was concluded that the described stabilizing solution ensures long-term stability on naked RNA at 4 degrees C, and ideal for the storage of RNA controls and standards for molecular diagnosis, the solution may be used for preserving clinical samples prior to transport to a clinical laboratory.

Scaling up in vitro transcription synthesis of RNA standards for competitive quantitative RT-PCR: looking for bigger yields.

Because the acquisition of in vitro transcription kits, for production of RNA standards, might not be affordable for some small laboratories, the current work describes some alternatives to the commercial Promega protocols. Yields of tested reactions were all higher than the ones reported for the standard Riboprobe kit (1mug RNA/mug template, 1x) and the optimized variant for high yields (5-10x). They were also as good as the ones described for the high RNA production kit RiboMAX (10-20x), exceeding them in approximately 70% of reactions. Our best results, achieved in a 500-mul format, were three to five times higher than the ones reported for the Promega kit.

The usefulness of Umelosa hepatitis C vírus qualitative kit as supplemental test for confirmation of hepatitis C virus infection.

Forty voluntary blood donors from two different blood banks in Havana, Cuba, who were repeatedly reactive on the routine screening of antibodies to hepatitis C virus, by Umelisa HCV test, were analyzed for the presence of HCV RNA using a nested PCR assay of the HCV 5' untranslated region, Umelosa HCV qualitative. Sera from 45 patients of a specialized gastroenterology consultation, positive to Umelisa HCV, were also assayed with the Umelosa HCV qualitative, to establish their condition related to the presence of HCV RNA previously to the indication of a treatment or after three, six or twelve months of antiviral therapy. Serum HCV-RNA was detected in 21/40 (52.5%) donors who had repeatedly positive ELISA results, confirming the HCV infection for them. In specialized consultation HCV-RNA was detected by PCR analysis in 30/45 (66%) analyzed sera.

The usefulness of Umelosa hepatitis C vírus qualitative kit as supplemental test for confirmation of hepatitis C virus infection

Quarenta doadores de sangue voluntários de dois bancos de sangue em Havana, Cuba, repetidamente reativos ao exame de rotina para anticorpos contra o vírus da hepatite C, pelo teste Umelisa HCV, foram analisados para a presença de RNA HCV através de um ensaio de PCR da regiäo 5' näo-traduzida do HCV denominado Umelosa HCV qualitativo. Amostras de soro obtidas de 45 pacientes atendidos em consulta gastroenterológica especializada, positivos para Umelisa HCV, também foram avaliados através do Umelosa HCV qualitativo, para estabelecer sua condiçäo em relaçäo à presença de RNA HCV previamente à indicaçäo de um tratamento ou após três, seis ou doze meses de terapia anti-viral. O RNA HCV sérico foi detectado em 21/40 (52,5 por cento) doadores que haviam apresentado resultados ELISA positivos repetidos, confirmando a infecçäo por HCV. Nos pacientes atendidos em consulta especializada, o RNA HCV foi detectado por análise de PCR em 30/45 (66 por cento) amostras de soro analisadas.

Validation of a nested PCR assay UMELOSA HCV CUALITATIVO for the detection of Hepatitis C virus.

An analysis of the performance characteristics of the UMELOSA HCV CUALITATIVO assay for the detection of Hepatitis C virus (HCV) RNA in human serum or plasma is presented. This qualitative in vitro diagnostic test is performed in three steps: (a) extraction of viral RNA, (b) reverse transcription of target RNA to generate complementary DNA followed by a polymerase chain reaction assay coupled with a second round of amplification, and finally (c) fluorescent detection of the amplified DNA by hybridization in a solid phase of an ultramicroplate coated with a complementary to amplified DNA probe. Considering the assay as a limit test for the control of impurities, the following analytical performance parameters were evaluated: specificity, detection limit and robustness. A comparative evaluation of the clinical performance and detection limit of our kit and the commercial AMPLICOR HCV test, version 2.0, was also included in the validation protocol. The assay had a good specificity and did not cross-react with the non-HCV analyzed positive samples. The 95% detection limit was of 101.7IU/ml with 95% confidence interval from 81.0 to 162.8IU/ml. The UMELOSA HCV CUALITATIVO meets the minimal sensitivity requirements for a single unit blood testing of 5000 and 1250IU/ml, defined by the Paul-Ehrlich-Institute in Germany and the Food and Drug Administration in USA, respectively. Compared with the commercial AMPLICOR, the test gave identical results for all analyzed positive and negative samples. In robustness studies there was no cross-contamination between negative samples and these same samples spiked with 10000IU/ml of HCV-RNA.