Approximately 5 million dengue virus–infected patients progress to a potentially life-threatening severe dengue (SD) infection annually. To identify the immune features and temporal dynamics underlying SD progression, we performed deep immune profiling by mass cytometry of PBMCs collected longitudinally from SD progressors (SDp) and uncomplicated dengue (D) patients. While D is characterized by early activation of innate immune responses, in SDp there is rapid expansion and activation of IgG-secreting plasma cells and memory and regulatory T cells. Concurrently, SDp, particularly children, demonstrate increased proinflammatory NK cells, inadequate expansion of CD16 ⁺ monocytes, and high expression of the FcγR CD64 on myeloid cells, yet a signature of diminished antigen presentation. Syndrome-specific determinants include suppressed dendritic cell abundance in shock/hemorrhage versus enriched plasma cell expansion in organ impairment. This study reveals uncoordinated immune responses in SDp and provides insights into SD pathogenesis in humans with potential implications for prediction and treatment.

Respiratory syncytial virus (RSV) and rhinovirus (RV) are major causes of acute respiratory infections (ARIs) worldwide. The circulation of both RSV and RV was notably altered during the COVID-19 pandemic. This study analyzed the epidemiological and molecular characteristics of RSV and RV in Santander, Colombia, during the pandemic period (PP, 2020–2021) and the post-pandemic period (PPP, 2023–2024). A total of 921 respiratory samples from patients with ARIs were screened for RSV-A/B and RV. Sequences of the RSV attachment glycoprotein (G) gene and the RV VP4–VP2 region were analyzed in positive samples. Epidemiological and clinical characteristics of the study population were also assessed. RSV was not detected during PP, whereas RV was detected in 4.8% of samples. During PPP, RSV-A, RSV-B, and RV were detected in 5.6%, 4.4%, and 28.0% of samples, respectively. RSV infections were mainly identified in children, while RV was detected across all age groups. RSV-A sequences grouped within seven A.D-derived lineages (A.D.1.5, A.D.1.7, A.D.1.8, A.D.3.2, A.D.3.3, A.D.5.1, A.D.5.2), whereas RSV-B sequences clustered within the B.D.E.1 lineage. RV showed a higher number of detected genotypes during the PPP than during the PP. The genotypic characterization performed in this study provides new insight into the molecular epidemiology of RSV and RV in Santander, Colombia, during PP and PPP, and represents, to our knowledge, the first regional description of RSV lineages and RV genotypes across these periods.

Severe dengue (SD) is a major cause of morbidity and mortality impacting approximately 5 million of the 400 million people infected with dengue virus (DENV) annually. To define DENV target cells and immunological hallmarks of SD progression in children’s blood, we integrated virus-inclusive single cell RNA-Seq 2 (viscRNA-Seq 2) with functional assays. Beyond myeloid cells, in natural infection, B cells harbor replicating DENV capable of infecting permissive cells. Alterations in cell type abundance, gene and protein expression and secretion, and cell-cell communications point towards increased migration and inflammation in SD progressors (SDp). Concurrently, antigen presenting cells from SDp demonstrate intact uptake, yet impaired interferon responses and antigen presentation, in part DENV-modulated. Increased activation, regulation, and exhaustion of effector responses and expansion of HLA-DR-expressing, possibly compensatory, adaptive-like NK cells also characterize SDp. These findings reveal DENV target cells in the human blood and provide insight into SD pathogenesis beyond antibody-mediated enhancement.

Introducción: Las infecciones respiratorias agudas (IRA) causadas por virus respiratorios constituyen una fuente importante de morbilidad y mortalidad en el mundo. Nos propusimos determinar la prevalencia de virus respiratorios en pacientes con sospecha de infección por SARS-CoV-2 y explorar la asociación entre coinfección de SARS-CoV-2 con otros virus respiratorios con la gravedad de la enfermedad respiratoria aguda. Métodos: Estudio de corte transversal, se analizaron hisopados de pacientes con síntomas sugestivos de COVID-19 en Santander, Colombia. Se seleccionaron muestras positivas y negativas para SARS-CoV-2 mediante un muestreo probabilístico proporcional. La detección de 15 virus se realizó mediante RT-qPCR en hisopados almacenados a -80°C. Se tomaron datos clínicos y epidemiológicos de las fichas epidemiológicas remitidas junto con la muestra respiratoria, para establecer la condición de gravedad (hospitalización o muerte por IRA). Resultados: Se incluyeron 600 hisopados colectados entre abril del 2020 y noviembre del 2021. La mediana de edad de los pacientes fue 55,0 años [RIC: 34,0] y el 58,5% fueron hombres. La prevalencia de rinovirus y adenovirus C fue de 4,7% y 0,3%, respectivamente. La prevalencia de coinfección de SARS-CoV-2 con rinovirus y adenovirus C fue de 3,3% (IC95%: 1,7-5,5) y 0,3% (IC95%: 0,0-1,4), respectivamente. Al momento de la toma de muestras, el 30,2 % correspondía a pacientes ambulatorios, el 59,8 % a pacientes hospitalizados y el 10,0 % a casos fatales. Se observó una diferencia en el reporte de comorbilidades entre los casos y controles (61,0 % vs. 46,5 %; p = 0,012). No se encontró asociación entre coinfección y la gravedad de la enfermedad (OR: 1,01; IC95%: 0,33 - 3,10), ajustando por edad, sexo, seguridad social y comorbilidades. Conclusiones: Durante el periodo epidémico la circulación de otros virus respiratorios fue baja. No observamos una asociación entre coinfección y gravedad de la enfermedad en las muestras evaluadas.

Cutaneous Leishmaniasis (CL) is a tropical disease endemic in many regions of Latin America. Its clinical diagnosis is often supported by histopathological analysis of skin biopsies; however, parasite detection by microscopy can be challenging, particularly in chronic or pauciparasitic lesions, leading to inconclusive results. Objective: This study aimed to evaluate the utility of polymerase chain reaction (PCR) as a confirmatory diagnostic tool for CL in formalin-fixed, paraffin-embedded (FFPE) biopsies with inconclusive histopathology. Methods: We analyzed 16 FFPE skin biopsy samples from patients with clinical suspicion of CL. All cases underwent routine histopathological evaluation using hematoxylin and eosin staining and were classified as inconclusive. DNA was extracted and PCR was performed, targeting the ITS1 and miniexon regions of Leishmania spp. Results: PCR successfully amplified Leishmania DNA in 8 (50%) out of 16 samples when both targets were utilized, confirming infection. These findings highlight the additional benefits of molecular tools in cases with inconclusive histopathology, thereby enhancing diagnostic accuracy and enabling species-level identification in certain instances. Conclusions: PCR proved to be a valuable diagnostic complement to histopathology in clinically and histologically suspected cases of CL without visible parasites. Its implementation may improve diagnostic accuracy and timely treatment in endemic areas.