Neutralizing Antibody Responses Elicited by Inactivated Whole Virus and Genetic Vaccines against Dominant SARS-CoV-2 Variants during the Four Epidemic Peaks of COVID-19 in Colombia.

Several SARS-CoV-2 variants of concern (VOC) and interest (VOI) co-circulate in Colombia, and determining the neutralizing antibody (nAb) responses is useful to improve the efficacy of COVID-19 vaccination programs. Thus, nAb responses against SARS-CoV-2 isolates from the lineages B.1.111, P.1 (Gamma), B.1.621 (Mu), AY.25.1 (Delta), and BA.1 (Omicron), were evaluated in serum samples from immunologically naïve individuals between 9 and 13 weeks after receiving complete regimens of CoronaVac, BNT162b2, ChAdOx1, or Ad26.COV2.S, using microneutralization assays. An overall reduction of the nAb responses against Mu, Delta, and Omicron, relative to B.1.111 and Gamma was observed in sera from vaccinated individuals with BNT162b2, ChAdOx1, and Ad26.COV2.S. The seropositivity rate elicited by all the vaccines against B.1.111 and Gamma was 100%, while for Mu, Delta, and Omicron ranged between 32 to 87%, 65 to 96%, and 41 to 96%, respectively, depending on the vaccine tested. The significant reductions in the nAb responses against the last three dominant SARS-CoV-2 lineages in Colombia indicate that booster doses should be administered following complete vaccination schemes to increase the nAb titers against emerging SARS-CoV-2 lineages.

Clinical outcomes associated with Mu variant infection during the third epidemic peak of COVID-19 in Colombia.

BACKGROUND: The higher number of cases and deaths caused by COVID-19 in Colombia occurred during the third epidemic peak, where the Mu variant was associated with 50% of the cases. OBJECTIVE: To evaluate the association between the clinical outcome of COVID-19 with health conditions and SARS-CoV-2 lineages. METHODS: In this study, clinical metadata and SARS-CoV-2 lineages from 535 patients with different degrees of COVID-19 severity were obtained after the SARS-CoV-2 genomic surveillance in Colombia. Then, the associations between these variables were determined using a multidimensional unfolding analysis. RESULTS: Asymptomatic, symptomatic, severe, and deceased outcomes represented 15.2%, 29.7%, 7.3%, and 47.8% of the cases, respectively. Males tend to develop more serious COVID-19, and severe or fatal outcomes were typically observed in patients aged >60 years with comorbidities, including chronic obstructive pulmonary disease, heart disease, kidney disease, obesity, asthma, and smoking history. The SARS-CoV-2 Mu and Gamma variants dominated the third epidemic peak and accounted for most fatal cases with odd ratio values of 128.2 (CI 53.0-310.1) and 18.6 (CI 8.294-41.917). CONCLUSION: This study shows the high impact of SARS-CoV-2 lineages with higher prevalence on public health and the importance of monitoring COVID-19 risk factors to control the associated mortality.

Seroprevalence of anti-SARS-CoV-2 antibodies in Colombia, 2020: A population-based study.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to cause very high morbidity and mortality throughout Latin American countries. However, few population-based seroprevalence surveys have been conducted to quantify attack rates and characterize drivers of transmission. METHODS: We conducted a population-based cross-sectional study to assess the seroprevalence of antibodies against SARS-CoV-2 in ten cities in Colombia between September and December 2020. The study involved multi-stage cluster sampling at each city. Participants provided a serum sample and answered a demographic and risk factor questionnaire. Prior infection by SARS-CoV-2 was ascertained using the "SARS-CoV-2 Total (COV2T) Advia Centaur - Siemens" chemiluminescence assay. FINDINGS: A total of 17863 participants from 7320 households participated in the study. Seroprevalence varied substantially between cities, ranging from 26% (95%CI 23-29 %) in Medellín to 68% (95%CI 62-74 %) in Guapi. There were no differences in seroprevalence by sex, but seropositivity was higher in certain ethnic groups. There was substantial heterogeneity in seroprevalence within cities, driven to a large extent by a strong association between socioeconomic stratum and seropositivity. INTERPRETATION: Colombia has been one of the Latin American countries most affected by the COVID-19 pandemic. This study documented very high attack rates in several Colombian cities by the end of 2020 and identified key drivers of heterogeneities including ethnicity and socioeconomic stratum. Few studies of seroprevalence of SARS-CoV-2 have been conducted in Latin America, and therefore this study contributes to the fundamental understanding of the pandemic in the region. FUNDING: The study was sponsored by, Ministerio de Ciencia y Tecnología e Innovación -CT361/2020, Ministerio de Salud y Protección Social, Fundación Universitaria del Norte, Imperial College of London, Universidad Nacional de Colombia (Sede Medellín), Universidad de Córdoba, California University, Unidad Nacional de Gestión del Riesgo, Centro de Atención y Diagnóstico de Enfermedades Infecciosas -CDI-, Centro Internacional de Entrenamiento e Investigaciones Médicas -CIDEIM-, Departamento Administrativo Nacional de Estadística - DANE, Fondo Nacional de Turismo -FONTUR-, Secretarías de Salud Departamentales, Distritales y Municipales and Instituto Nacional de Salud.

Prolonged SARS-CoV-2 nucleic acid conversion time in military personnel outbreaks with presence of specific IgG antibodies.

Coronavirus disease 2019 (COVID-19) is transmitted person-to-person mainly by close contact or droplets from respiratory tract. However, the actual time of viral shedding is still uncertain as well as the different routes of transmission. We aimed to characterize RNA shedding from nasopharyngeal and rectal samples in prolonged cases of mild COVID-19 in young male soldiers. Seventy patients from three different military locations were monitored after recommending to follow more strict isolation measures to prevent the spread of the virus. Then, nasopharyngeal, rectal, and blood samples were taken. SARS-CoV-2 RNA was detected by RT-PCR and specific antibodies by chemiluminescent immunoassays. The median nucleic acid conversion time (NACT) was 60 days (IQR: 7-85 days). Rectal swabs were taken in 60 % of patients. Seven patients (10 %) were positive in nasopharyngeal and rectal swabs, and five (7.14 %) remained positive in rectal swabs, but negative in nasopharyngeal samples. Four patients (5.71 %) that had been discharged, were positive again after 15 days. No significant difference was found in nucleic acid conversion time between age groups nor clinical classification. Maintaining distancing among different positive patients is essential as a possible re-exposure to the virus could cause a longer nucleic acid conversion time in SARS-COV-2 infections.

Low Neutralizing Antibody Titers against the Mu Variant of SARS-CoV-2 in 31 BNT162b2 Vaccinated Individuals in Colombia.

Global surveillance programs for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are showing the emergence of variants with mutations in the spike protein. Genomic and laboratory surveillance are important to determine if these variants may be more infectious or less susceptible to antiviral treatments and vaccine-induced antibodies. Three of the most predominant SARS-CoV-2 variants in Colombia during the epidemiological peaks of 2021 were isolated: Mu, a variant of interest; Gamma, a variant of concern; B.1.111, which lacks genetic markers associated with greater virulence. Microneutralization assays were performed by incubating 120 mean tissue culture infectious doses (TCID50) of each SARS-CoV-2 isolate with five two-fold serial dilutions of sera from 31 BNT162b2-vaccinated volunteers. The mean neutralization titer (MN50) was calculated by the Reed-Muench method. At the end of August, Mu represented 49% of coronavirus disease 2019 (COVID-19) cases in Colombia, followed by 25% of Gamma. In contrast, B.1.111 became almost undetectable. The evaluation of neutralizing antibodies suggests that patients vaccinated with BNT162b2 generate neutralizing antibody titers against the Mu variant at significantly lower concentrations relative to B.1.111 and Gamma. This study shows the importance of continuing surveillance programs of emerging variants, as well as the need to evaluate the neutralizing antibody response induced by other vaccines.

Reduced levels of convalescent neutralizing antibodies against SARS-CoV-2 B.1+L249S+E484K lineage.

The E484K mutation at the SARS-CoV-2 Spike protein emerged independently in different variants around the world and has been widely associated with immune escape from neutralizing antibodies generated during previous infection or vaccination. In this work, the B.1 + L249S+E484K lineage was isolated along with A.1, B.1.420, and B.1.111 SARS-CoV-2 lineages without the E484K mutation and the neutralizing titer of convalescent sera was compared using microneutralization assays. While no significant differences in the neutralizing antibody titers were found between A.1 and B.lineages without the E484K mutation, the neutralizing titers against B.1 + L249S+E484K were 1.5, 1.9, 2.1, and 1.3-fold lower than against A.1, B.1.420, B.1.111-I, and B.1.111-II, respectively. However, molecular epidemiological data indicate that there is no increase in the transmissibility rate associated with this new lineage. This study supports the capability of new variants with the E484K mutation to be resistant to neutralization by humoral immunity, and therefore the need to intensify surveillance programs to determine if these lineages represent a risk for public health.

Characterization of the emerging B.1.621 variant of interest of SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genetic diversity has the potential to impact the virus transmissibility and the escape from natural infection- or vaccine-elicited neutralizing antibodies. Here, representative samples from circulating SARS-CoV-2 in Colombia between January and April 2021, were processed for genome sequencing and lineage determination following the nanopore amplicon ARTIC network protocol and PANGOLIN pipeline. This strategy allowed us to identify the emergence of the B.1.621 lineage, considered a variant of interest (VOI) with the accumulation of several substitutions affecting the Spike protein, including the amino acid changes I95I, Y144T, Y145S and the insertion 146 N in the N-terminal domain, R346K, E484K and N501Y in the Receptor binding Domain (RBD) and P681H in the S1/S2 cleavage site of the Spike protein. The rapid increase in frequency and fixation in a relatively short time in Magdalena, Atlantico, Bolivar, Bogotá D.C, and Santander that were near the theoretical herd immunity suggests an epidemiologic impact. Further studies will be required to assess the biological and epidemiologic roles of the substitution pattern found in the B.1.621 lineage.

Novel Highly Divergent SARS-CoV-2 Lineage With the Spike Substitutions L249S and E484K.

COVID-19 pandemics has led to genetic diversification of SARS-CoV-2 and the appearance of variants with potential impact in transmissibility and viral escape from acquired immunity. We report a new and highly divergent lineage containing 21 distinctive mutations (10 non-synonymous, eight synonymous, and three substitutions in non-coding regions). The amino acid changes L249S and E484K located at the CTD and RBD of the Spike protein could be of special interest due to their potential biological role in the virus-host relationship. Further studies are required for monitoring the epidemiologic impact of this new lineage.

SARS-CoV-2 and RT-PCR in asymptomatic patients: Results of a cohort of workers at El Dorado International Airport in Bogotá, 2020

Resumen Introducción. La pandemia de COVID-19 ha ocasionado cerca de 25 millones de casos en el mundo. Se ha descrito que los pacientes asintomáticos pueden ser fuentes de transmisión. Sin embargo, es difícil detectarlos y no es claro su papel en la dinámica de transmisión del virus, lo que obstaculiza la implementación de estrategias para la prevención. Objetivo. Describir el comportamiento de la infección asintomática por SARS-CoV-2 en una cohorte de trabajadores del Aeropuerto Internacional El Dorado "Luis Carlos Galán Sarmiento" de Bogotá, Colombia. Materiales y métodos. Se diseñó una cohorte prospectiva de trabajadores del Aeropuerto El Dorado. El seguimiento se inició en junio de 2020 con una encuesta a cada trabajador para caracterizar sus condiciones de salud y trabajo. Cada 21 días se tomó una muestra de hisopado nasofaríngeo para detectar la presencia del SARS-CoV-2 mediante reacción en cadena de la polimerasa con transcriptasa inversa (RT-PCR). Se analizó el comportamiento del umbral del ciclo (cycle threshold) de los genes ORFlab y N según el día de seguimiento. Resultados. En los primeros tres seguimientos de la cohorte se encontró una incidencia de la infección por SARS-CoV-2 del 16,51 %. La proporción de contactos positivos fue del 14,08 %. La mediana del umbral del ciclo fue de 33,53. Conclusión. Se determinaron las características de la infección asintomática por el SARS-CoV-2 en una cohorte de trabajadores. La detección de infectados asintomáticos sigue siendo un reto para los sistemas de vigilancia epidemiológica. Introduction: The 2019 coronavirus pandemic (COVID-19) has caused around 25 million cases worldwide. Asymptomatic patients have been described as potential sources of transmission. However, there are difficulties to detect them and to establish their role in the dynamics of virus transmission, which hinders the implementation of prevention strategies. Objective: To describe the behavior of asymptomatic SARS-CoV-2 virus infection in a cohort of workers at the El Dorado "Luis Carlos Galán Sarmiento" International Airport in Bogotá, Colombia. Materials and methods: A prospective cohort of 212 workers from the El Dorado airport was designed. The follow-up began in June, 2020. A survey was used to characterize health and work conditions. Every 21 day, a nasopharyngeal swab was taken to identify the presence of SARS-CoV-2 using RT-PCR. We analyzed the behavior of the cycle threshold (ORFlab and N genes) according to the day of follow-up. Results: In the first three follow-ups of the cohort, we found an incidence of SARS-CoV-2 infection of 16.51%. The proportion of positive contacts was 14.08%. The median threshold for cycle threshold was 33.53. Conclusion: We characterized the asymptomatic SARS-CoV-2 infection in a cohort of workers. The identification of asymptomatic infected persons continues to be a challenge for epidemiological surveillance systems.

Isolation and characterization of an early SARS-CoV-2 isolate from the 2020 epidemic in Medellín, Colombia

Resumen Introducción. El nuevo coronavirus causante de un brote de enfermedad respiratoria aguda en China en diciembre de 2019 se identificó como SARS-CoV-2. La enfermedad, denominada COVID-19, fue declarada pandemia por la Organización Mundial de la Salud (OMS). El primer caso de COVID-19 en Colombia se reportó el 6 de marzo de 2020;en este estudio se caracterizó un aislamiento temprano del virus SARS-CoV-2 de una muestra recolectada en abril de 2020. Objetivos. Describir y caracterizar una cepa temprana a partir de un aislamiento de SARS-CoV-2 durante la pandemia en Colombia. Materiales y métodos. Se obtuvo una muestra de un paciente con COVID-19 confirmada por qRT-PCR;la muestra fue inoculada en diferentes líneas celulares hasta la aparición del efecto citopático. Para confirmar la presencia de SARS-CoV-2 en el cultivo, se utilizó la qRT-PCR a partir de los sobrenadantes, la inmunofluorescencia indirecta (IFI) en células Vero-E6, así como microscopía electrónica y secuenciación de nueva generación (next-generation sequencing). Resultados. Se confirmó el aislamiento de SARS-CoV-2 en células Vero-E6 por la aparición del efecto citopático tres días después de la infección, así como mediante la qRT-PCR y la IFI positiva con suero de paciente convaleciente positivo para SARS-CoV-2. Además, en las imágenes de microscopía electrónica de trasmisión y de barrido de células infectadas se observaron estructuras compatibles con viriones de SARS-CoV-2. Por último, se obtuvo la secuencia completa del genoma, lo que permitió clasificar el aislamiento como linaje B.1.5. Conclusiones. La evidencia presentada en este artículo permite confirmar el primer aislamiento de SARS-CoV-2 en Colombia. Además, muestra que esta cepa se comporta en cultivo celular de manera similar a lo reportado en la literatura para otros aislamientos y que su composición genética está acorde con la variante predominante en el mundo. Finalmente, se resalta la importancia que tiene el aislamiento viral para la detección de anticuerpos, para la caracterización genotípica y fenotípica de la cepa y para probar compuestos con potencial antiviral. Introduction: SARS-CoV-2 has been identified as the new coronavirus causing an outbreak of acute respiratory disease in China in December, 2019. This disease, currently named COVID-19, has been declared as a pandemic by the World Health Organization (WHO). The first case of COVID-19 in Colombia was reported on March 6, 2020. Here we characterize an early SARS-CoV-2 isolate from the pandemic recovered in April, 2020. Objective: To describe the isolation and characterization of an early SARS-CoV-2 isolate from the epidemic in Colombia. Materials and methods: A nasopharyngeal specimen from a COVID-19 positive patient was inoculated on different cell lines. To confirm the presence of SARS-CoV-2 on cultures we used qRT-PCR, indirect immunofluorescence assay, transmission and scanning electron microscopy, and next-generation sequencing. Results: We determined the isolation of SARS-CoV-2 in Vero-E6 cells by the appearance of the cytopathic effect three days post-infection and confirmed it by the positive results in the qRT-PCR and the immunofluorescence with convalescent serum. Transmission and scanning electron microscopy images obtained from infected cells showed the presence of structures compatible with SARS-CoV-2. Finally, a complete genome sequence obtained by next-generation sequencing allowed classifying the isolate as B.1.5 lineage. Conclusion: The evidence presented in this article confirms the first isolation of SARS-CoV-2 in Colombia. In addition, it shows that this strain behaves in cell culture in a similar way to that reported in the literature for other isolates and that its genetic composition is consistent with the predominant variant in the world. Finally, points out the importance of viral isolation for the detection of neutralizing antibodies, for the genotypic and phenotypic characterization of the strain and for testing compounds with antiviral potential.

SARS-CoV-2 sequencing: The technological initiative to strengthen early warning systems for public health emergencies in Latin America and the Caribbean

Resumen La pandemia de COVID-19 causada por el SARS-CoV-2 es un problema de salud pública sin precedentes en los últimos 100 años, así como la respuesta centrada en la caracterización genómica del SARS-CoV-2 prácticamente en todas las regiones del planeta. Esta pandemia surgió durante la era de la epidemiología genómica impulsada por los continuos avances en la secuenciación de próxima generación. Desde su reciente aparición, la epidemiología genómica permitió la identificación precisa de nuevos linajes o especies de agentes patógenos y la reconstrucción de su variabilidad genética en tiempo real, lo que se hizo evidente en los brotes de influenza H1N1, MERS y SARS. Sin embargo, la escala global y descontrolada de esta pandemia ha generado una situación que obligó a utilizar de forma masiva herramientas de la epidemiología genómica como la rápida identificación del SARS-CoV-2 y el registro de nuevos linajes y su vigilancia activa en todo el mundo. Antes de la pandemia de COVID-19 la disponibilidad de datos genómicos de agentes patógenos circulantes en varios países de Latinoamérica y el Caribe era escasa o nula. Con la llegada del SARS-CoV-2 dicha situación cambió significativamente, aunque la cantidad de información disponible sigue siendo escasa y, en países como Colombia, Brasil, Argentina y Chile, la información genómica del SARS-CoV-2 provino principalmente de grupos de investigación en epidemiología genómica más que como producto de una política o programa de vigilancia en salud pública. Ello evidencia la necesidad de establecer políticas de salud pública orientadas a la implementación de la epidemiología genómica como herramienta para fortalecer los sistemas de vigilancia y alerta temprana frente a amenazas para la salud pública en la región. The COVID-19 pandemic caused by SARS-CoV-2 is a public health problem on a scale unprecedented in the last 100 years, as has been the response focused on the rapid genomic characterization of SARS-CoV-2 in virtually all regions of the planet. This pandemic emerged during the era of genomic epidemiology, a science fueled by continued advances in next-generation sequencing. Since its recent appearance, genomic epidemiology included the precise identification of new lineages or species of pathogens and the reconstruction of their genetic variability in real time, evidenced in past outbreaks of influenza H1N1, MERS, and SARS. However, the global and uncontrolled scale of this pandemic created a scenario where genomic epidemiology was put into practice en masse, from the rapid identification of SARS-CoV-2 to the registration of new lineages and their active surveillance throughout the world. Prior to the COVID-19 pandemic, the availability of genomic data on circulating pathogens in several Latin America and the Caribbean countries was scarce or nil. With the arrival of SARS-CoV-2, this scenario changed significantly, although the amount of available information remains scarce and, in countries such as Colombia, Brazil, Argentina, and Chile, the genomic information of SARS-CoV-2 was obtained mainly by research groups in genomic epidemiology rather than the product of a public health surveillance policy or program. This indicates the need to establish public health policies aimed at implementing genomic epidemiology as a tool to strengthen surveillance and early warning systems against threats to public health in the region.

Genomic Epidemiology of Severe Acute Respiratory Syndrome Coronavirus 2, Colombia.

Coronavirus disease (COVID-19) in Colombia was first diagnosed in a traveler arriving from Italy on February 26, 2020. However, limited data are available on the origins and number of introductions of COVID-19 into the country. We sequenced the causative agent of COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), from 43 clinical samples we collected, along with another 79 genome sequences available from Colombia. We investigated the emergence and importation routes for SARS-CoV-2 into Colombia by using epidemiologic, historical air travel, and phylogenetic observations. Our study provides evidence of multiple introductions, mostly from Europe, and documents >12 lineages. Phylogenetic findings validate the lineage diversity, support multiple importation events, and demonstrate the evolutionary relationship of epidemiologically linked transmission chains. Our results reconstruct the early evolutionary history of SARS-CoV-2 in Colombia and highlight the advantages of genome sequencing to complement COVID-19 outbreak investigations.

COVID-19 Infection Detection and Prevention by SARS-CoV-2 Active Antigens: A Synthetic Vaccine Approach.

COVID-19, a global pandemic causing to date more than 50 million cases and more than a million deaths, has to be controlled. SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) was identified as the causative agent. Controversy about this virus origin and infectious mechanism for adapting to humans remains a matter for discussion. Among all strategies for obtaining safe and potent vaccines, approaches based on attenuated-killed virus and non-replicating RNA viral vectors are demonstrating promising results. However, specificity of viral components targeted by human antibodies so far has not been demonstrated. A consistent strategy for obtaining functional-active antigens from SARS-CoV-2 specific ligands lead us to propose and test a number of synthetic components. From hundreds of starting sequences only fifteen fulfilled the design requirements and were produced as monomer and polymer forms and immuno-chemically tested. The design was based on worldwide representative reported virus genomes. A bioinformatics scheme by conventional methods and knowledge on MHC-I and II antigen processing mechanisms and HLA haplotype-restriction was performed including sensitive and resistant human populations to virus infection. Covid-19 patients' sera reactivity for synthetic SARS-CoV-2-designed components have proven a high recognition of specific molecules, as well as some evidence for a long-lasting humoral immune response.

Isolation and characterization of an early SARS-CoV-2 isolate from the 2020 epidemic in Medellín, Colombia / [Aislamiento y caracterización de una cepa temprana de SARS-CoV-2 durante la epidemia de 2020 en Medellín, Colombia].

Introduction: SARS-CoV-2 has been identified as the new coronavirus causing an outbreak of acute respiratory disease in China in December, 2019. This disease, currently named COVID-19, has been declared as a pandemic by the World Health Organization (WHO). The first case of COVID-19 in Colombia was reported on March 6, 2020. Here we characterize an early SARS-CoV-2 isolate from the pandemic recovered in April, 2020. Objective: To describe the isolation and characterization of an early SARS-CoV-2 isolate from the epidemic in Colombia. Materials and methods: A nasopharyngeal specimen from a COVID-19 positive patient was inoculated on different cell lines. To confirm the presence of SARS-CoV-2 on cultures we used qRT-PCR, indirect immunofluorescence assay, transmission and scanning electron microscopy, and next-generation sequencing. Results: We determined the isolation of SARS-CoV-2 in Vero-E6 cells by the appearance of the cytopathic effect three days post-infection and confirmed it by the positive results in the qRT-PCR and the immunofluorescence with convalescent serum. Transmission and scanning electron microscopy images obtained from infected cells showed the presence of structures compatible with SARS-CoV-2. Finally, a complete genome sequence obtained by next-generation sequencing allowed classifying the isolate as B.1.5 lineage. Conclusion: The evidence presented in this article confirms the first isolation of SARSCoV-2 in Colombia. In addition, it shows that this strain behaves in cell culture in a similar way to that reported in the literature for other isolates and that its genetic composition is consistent with the predominant variant in the world. Finally, points out the importance of viral isolation for the detection of neutralizing antibodies, for the genotypic and phenotypic characterization of the strain and for testing compounds with antiviral potential.

Introducción. El nuevo coronavirus causante de un brote de enfermedad respiratoria aguda en China en diciembre de 2019 se identificó como SARS-CoV-2. La enfermedad, denominada COVID-19, fue declarada pandemia por la Organización Mundial de la Salud (OMS). El primer caso de COVID-19 en Colombia se reportó el 6 de marzo de 2020; en este estudio se caracterizó un aislamiento temprano del virus SARS-CoV-2 de una muestra ecolectada en abril de 2020. Objetivos. Describir y caracterizar una cepa temprana a partir de un aislamiento de SARSCoV-2 durante la pandemia en Colombia. Materiales y métodos. Se obtuvo una muestra de un paciente con COVID-19 confirmada por qRT-PCR; la muestra fue inoculada en diferentes líneas celulares hasta la aparición del efecto citopático. Para confirmar la presencia de SARS-CoV-2 en el cultivo, se utilizó la qRT-PCR a partir de los sobrenadantes, la inmunofluorescencia indirecta (IFI) en células Vero-E6, así como microscopía electrónica y secuenciación de nueva generación (nextgeneration sequencing). Resultados. Se confirmó el aislamiento de SARS-CoV-2 en células Vero-E6 por la aparición del efecto citopático tres días después de la infección, así como mediante la qRT-PCR y la IFI positiva con suero de paciente convaleciente positivo para SARS-CoV-2. Además, en las imágenes de microscopía electrónica de trasmisión y de barrido de células infectadas se observaron estructuras compatibles con viriones de SARS-CoV-2. Por último, se obtuvo la secuencia completa del genoma, lo que permitió clasificar el aislamiento como linaje B.1.5. Conclusiones. La evidencia presentada en este artículo permite confirmar el primer aislamiento de SARS-CoV-2 en Colombia. Además, muestra que esta cepa se comporta en cultivo celular de manera similar a lo reportado en la literatura para otros aislamientos y que su composición genética está acorde con la variante predominante en el mundo. Finalmente, se resalta la importancia que tiene el aislamiento viral para la detección de anticuerpos, para la caracterización genotípica y fenotípica de la cepa y para probar compuestos con potencial antiviral.

SARS-CoV-2 and RT-PCR in asymptomatic patients: Results of a cohort of workers at El Dorado International Airport in Bogotá, 2020 / [SARS-CoV-2 y RT-PCR en pacientes asintomáticos: resultados de una cohorte de trabajadores del Aeropuerto Internacional El Dorado de Bogotá, 2020].

Introduction: The 2019 coronavirus pandemic (COVID-19) has caused around 25 million cases worldwide. Asymptomatic patients have been described as potential sources of transmission. However, there are difficulties to detect them and to establish their role in the dynamics of virus transmission, which hinders the implementation of prevention strategies. Objective: To describe the behavior of asymptomatic SARS-CoV-2 virus infection in a cohort of workers at the El Dorado "Luis Carlos Galán Sarmiento" International Airport in Bogotá, Colombia. Materials and methods: A prospective cohort of 212 workers from the El Dorado airport was designed. The follow-up began in June, 2020. A survey was used to characterize health and work conditions. Every 21 day, a nasopharyngeal swab was taken to identify the presence of SARS-CoV-2 using RT-PCR. We analyzed the behavior of the cycle threshold (ORF1ab and N genes) according to the day of follow-up. Results: In the first three follow-ups of the cohort, we found an incidence of SARS-CoV-2 infection of 16.51%. The proportion of positive contacts was 14.08%. The median threshold for cycle threshold was 33.53. Conclusion: We characterized the asymptomatic SARS-CoV-2 infection in a cohort of workers. The identification of asymptomatic infected persons continues to be a challenge for epidemiological surveillance systems.

Introducción. La pandemia de COVID-19 ha ocasionado cerca de 25 millones de casos en el mundo. Se ha descrito que los pacientes asintomáticos pueden ser fuentes de transmisión. Sin embargo, es difícil detectarlos y no es claro su papel en la dinámica de transmisión del virus, lo que obstaculiza la implementación de estrategias para la prevención. Objetivo. Describir el comportamiento de la infección asintomática por SARS-CoV-2 en una cohorte de trabajadores del Aeropuerto Internacional El Dorado "Luis Carlos Galán Sarmiento" de Bogotá, Colombia. Materiales y métodos. Se diseñó una cohorte prospectiva de trabajadores del Aeropuerto El Dorado. El seguimiento se inició en junio de 2020 con una encuesta a cada trabajador para caracterizar sus condiciones de salud y trabajo. Cada 21 días se tomó una muestra de hisopado nasofaríngeo para detectar la presencia del SARS-CoV-2 mediante reacción en cadena de la polimerasa con transcriptasa inversa (RT-PCR). Se analizó el comportamiento del umbral del ciclo (cycle threshold) de los genes ORF1ab y N según el día de seguimiento. Resultados. En los primeros tres seguimientos de la cohorte se encontró una incidencia de la infección por SARS-CoV-2 del 16,51 %. La proporción de contactos positivos fue del 14,08 %. La mediana del umbral del ciclo fue de 33,53. Conclusión. Se determinaron las características de la infección asintomática por el SARSCoV-2 en una cohorte de trabajadores. La detección de infectados asintomáticos sigue siendo un reto para los sistemas de vigilancia epidemiológica.

SARS-CoV-2 sequencing: The technological initiative to strengthen early warning systems for public health emergencies in Latin America and the Caribbean / [Secuenciación del SARS-CoV-2: la iniciativa tecnológica para fortalecer los sistemas de alerta temprana ante emergencias de salud pública en Latinoamérica y el Caribe].

The COVID-19 pandemic caused by SARS-CoV-2 is a public health problem on a scale unprecedented in the last 100 years, as has been the response focused on the rapid genomic characterization of SARS-CoV-2 in virtually all regions of the planet. This pandemic emerged during the era of genomic epidemiology, a science fueled by continued advances in next-generation sequencing. Since its recent appearance, genomic epidemiology included the precise identification of new lineages or species of pathogens and the reconstruction of their genetic variability in real time, evidenced in past outbreaks of influenza H1N1, MERS, and SARS. However, the global and uncontrolled scale of this pandemic created a scenario where genomic epidemiology was put into practice en masse, from the rapid identification of SARS-CoV-2 to the registration of new lineages and their active surveillance throughout the world. Prior to the COVID-19 pandemic, the availability of genomic data on circulating pathogens in several Latin America and the Caribbean countries was scarce or nil. With the arrival of SARS-CoV-2, this scenario changed significantly, although the amount of available information remains scarce and, in countries such as Colombia, Brazil, Argentina, and Chile, the genomic information of SARS-CoV-2 was obtained mainly by research groups in genomic epidemiology rather than the product of a public health surveillance policy or program. This indicates the need to establish public health policies aimed at implementing genomic epidemiology as a tool to strengthen surveillance and early warning systems against threats to public health in the region.

La pandemia de COVID-19 causada por el SARS-CoV-2 es un problema de salud pública sin precedentes en los últimos 100 años, así como la respuesta centrada en la caracterización genómica del SARS-CoV-2 prácticamente en todas las regiones del planeta. Esta pandemia surgió durante la era de la epidemiología genómica impulsada por los continuos avances en la secuenciación de próxima generación. Desde su reciente aparición, la epidemiología genómica permitió la identificación precisa de nuevos linajes o especies de agentes patógenos y la reconstrucción de su variabilidad genética en tiempo real, lo que se hizo evidente en los brotes de influenza H1N1, MERS y SARS. Sin embargo, la escala global y descontrolada de esta pandemia ha generado una situación que obligó a utilizar de forma masiva herramientas de la epidemiología genómica como la rápida identificación del SARS-CoV-2 y el registro de nuevos linajes y su vigilancia activa en todo el mundo. Antes de la pandemia de COVID-19 la disponibilidad e datos genómicos de agentes patógenos circulantes en varios países de Latinoamérica y el Caribe era escasa o nula. Con la llegada del SARS-CoV-2 dicha situación cambió significativamente, aunque la cantidad de información disponible sigue siendo escasa y, en países como Colombia, Brasil, Argentina y Chile, la información genómica del SARS-CoV-2 provino principalmente de grupos de investigación en epidemiología genómica más que como producto de una política o programa de vigilancia en salud pública.

Substitutions in Spike and Nucleocapsid proteins of SARS-CoV-2 circulating in South America.

SARS-CoV-2 is a new member of the genus Betacoronavirus, responsible for the COVID-19 pandemic. The virus crossed the species barrier and established in the human population taking advantage of the spike protein high affinity for the ACE receptor to infect the lower respiratory tract. The Nucleocapsid (N) and Spike (S) are highly immunogenic structural proteins and most commercial COVID-19 diagnostic assays target these proteins. In an unpredictable epidemic, it is essential to know about their genetic variability. The objective of this study was to describe the substitution frequency of the S and N proteins of SARS-CoV-2 in South America. A total of 504 amino acid and nucleotide sequences of the S and N proteins of SARS-CoV-2 from seven South American countries (Argentina, Brazil, Chile, Ecuador, Peru, Uruguay, and Colombia), reported as of June 3, and corresponding to samples collected between March and April 2020, were compared through substitution matrices using the Muscle algorithm. Forty-three sequences from 13 Colombian departments were obtained in this study using the Oxford Nanopore and Illumina MiSeq technologies, following the amplicon-based ARTIC network protocol. The substitutions D614G in S and R203K/G204R in N were the most frequent in South America, observed in 83% and 34% of the sequences respectively. Strikingly, genomes with the conserved position D614 were almost completely replaced by genomes with the G614 substitution between March to April 2020. A similar replacement pattern was observed with R203K/G204R although more marked in Chile, Argentina and Brazil, suggesting similar introduction history and/or control strategies of SARS-CoV-2 in these countries. It is necessary to continue with the genomic surveillance of S and N proteins during the SARS-CoV-2 pandemic as this information can be useful for developing vaccines, therapeutics and diagnostic tests.

Molecular analysis of several in-house rRT-PCR protocols for SARS-CoV-2 detection in the context of genetic variability of the virus in Colombia.

The COVID-19 pandemic caused by SARS-CoV-2 is a public health problem unprecedented in the recent history of humanity. Different in-house real-time RT-PCR (rRT-PCR) methods for SARS-CoV-2 diagnosis and the appearance of genomes with mutations in primer regions have been reported. Hence, whole-genome data from locally-circulating SARS-CoV-2 strains contribute to the knowledge of its global variability and the development and fine tuning of diagnostic protocols. To describe the genetic variability of Colombian SARS-CoV-2 genomes in hybridization regions of oligonucleotides of the main in-house methods for SARS-CoV-2 detection, RNA samples with confirmed SARS-CoV-2 molecular diagnosis were processed through next-generation sequencing. Primers/probes sequences from 13 target regions for SARS-CoV-2 detection suggested by 7 institutions and consolidated by WHO during the early stage of the pandemic were aligned with Muscle tool to assess the genetic variability potentially affecting their performance. Finally, the corresponding codon positions at the 3' end of each primer, the open reading frame inspection was identified for each gene/protein product. Complete SARS-CoV-2 genomes were obtained from 30 COVID-19 cases, representative of the current epidemiology in the country. Mismatches between at least one Colombian sequence and five oligonucleotides targeting the RdRP and N genes were observed. The 3' end of 4 primers aligned to the third codon position, showed high risk of nucleotide substitution and potential mismatches at this critical position. Genetic variability was detected in Colombian SARS-CoV-2 sequences in some of the primer/probe regions for in-house rRT-PCR diagnostic tests available at WHO COVID-19 technical guidelines; its impact on the performance and rates of false-negative results should be experimentally evaluated. The genomic surveillance of SARS-CoV-2 is highly recommended for the early identification of mutations in critical regions and to issue recommendations on specific diagnostic tests to ensure the coverage of locally-circulating genetic variants.