Severe dengue (SD) is a major cause of morbidity and mortality impacting approximately 5 million out of 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.

The prevalence of Chagas disease has decreased, non-vectorial transmission through blood transfusions and organ transplantation has gained importance in recent years.

Background Dengue fever and COVID-19 co-infection constitute a significant public health concern in Latin America, becoming a clinical challenge to distinguish these two entities in early stages of the disease. Clinical outcomes of coinfected hospitalized patients have not been well established. Methods A cross-sectional study was conducted. We included suspected patients diagnosed with COVID-19/dengue co-infection admitted at Hospital Fundación Valle del Lili, Cali – Colombia, from March 2020 to March 2021. All dengue patients had positive NS1 and/or IgM dengue antibodies. SARS-CoV-2 infection was confirmed by RT-PCR or antigen rapid test from nasopharyngeal swab. Laboratory and clinical data were recollected from the clinical laboratory database, clinical charts, and institutional COVID-19 registry. Results A total of 90 COVID-19 patients were included. 72 patients were confirmed only with COVID-19, and 18 with dengue co-infection. Most patients were male: 46 (63.9%) vs. 13 (72.2%). None of these study patients were vaccinated against COVID-19 or dengue. The median time from symptoms onset and the diagnosis was five days, and fever was the most common symptom for both groups. There were significant differences between COVID-19 patients and coinfected patients regarding presence of dyspnea (22.2% vs. 61.1%; p=0.003), desaturation (13.4% vs. 53.3%; p=0.002) and a higher neutrophil/lymphocyte ratio (NLR) (3.84 vs. 5.59; p = 0.038). The co-infection was associated with a worse presentation of the COVID-19 infection (p=0.002), an increased requirement of initial supplemental oxygen therapy (p=0.007), mechanical ventilation (p=0.0004), ICU management at the admission (p=0.002), and ICU final management (p=0.002). Overall mortality in patients with co-infection was 44.4% vs. 6.9% in only COVID-19 infected patients (p< 0.001). Conclusion Despite the pandemic era, the possibility of co-infection of these two entities must be considered. Admitted coinfected patients were associated with worse clinical outcomes and higher mortality. According to our results, patients with co-infection present with severe respiratory symptoms and an elevated NLR. The impact of the Covid 19 vaccination on this coinfection is unknown. Disclosures Olga Agudelo, n/a, Fundación valle del lili: Board Member.

Background Cytomegalovirus (CMV) infection is a significant disease in immunocompromised patients, particularly transplant patients. The wide use of antivirals for prophylaxis and treatment has decreased the incidence and impact of this disease. Although, this exposure can lead to mutations in CMV UL54 and UL97 genes, which are associated with antiviral resistance. Little is known of the frequency of these mutations in Latin America, despite an increase in the transplant population. Methods We performed a prospective observational study. Patients with suspected CMV resistance based on the persistence of CMV DNAemia despite treatment were included from April to December 2019 in Fundación Valle del Lili. The blood samples were processed for DNA extraction, amplification, and sequencing for molecular characterization of (UL97) and (UL54) genes. Laboratory and clinical data were recollected from the clinical laboratory database and clinical charts. Results We enrolled 50 patients with CMV DNAemia, 32 amplified for gene sequencing. The median age was 31.7 years old, and 46.8% were males. 65.6% had a stem cell transplant, and 28.1% had a solid organ transplant. Only 65.2% had previous antiviral exposure. 93.7% manifested with CMV DNAemia alone, and 6.2% had CMV disease, hepatitis, and colitis. According to our findings, 56.2% had only UL54 mutations, 6.25% had only UL97 mutations, and 37.5% had both. The mutations associated with antiviral resistance were D605E and A594V for UL97 and A692S for UL54. The most common UL97 polymorphisms were V355A and F396L, while for UL54 were N898D, N685S, and S655L. On day 14 of treatment, 21.8% (7/32) had treatment failure. No canonic resistance mutations were found. 15.6% (5/32) of patients died; none had UL97 mutations, two had UL54 mutations associated with antiviral resistance, and three had polymorphisms of this gene. Conclusion Our study is the first one performed in Colombia. Although resistance was low, it was present in a few patients and related to mortality. It is important to study this evolving resistance as the use of antivirals increases in the transplant population in Latin America. Disclosures Olga Agudelo, n/a, Fundación valle del lili: Board Member.

Background Thrombocytopenia is a marker of severity in dengue, and its resolution predicts clinical improvement. The objective was to evaluate mean platelet volume (MPV) trajectories as a predictor of platelet count (PC) recovery in dengue patients. Methods An observational, longitudinal and analytical study was conducted at Fundación Valle del Lili (Cali, Colombia). Patients diagnosed with dengue during 2016–2020 were included. The association between PC and the covariates was evaluated using simple linear, quadratic and non-parametric spline smoothing regression models. A longitudinal linear mixed model was adjusted and then validated for PC measurements. Results A total of 71 patients were included. The median age was 27 y, 38.5% were women and half had dengue with warning signs. A statistically significant PC decrease was observed when MPV was 13.87 fL and 4.46 d from the onset of symptoms, while PC displayed a significant constant increase with neutrophils count. Then, PC recovery was achieved with an MPV of 13.58 fL, 4.5 d from the onset of symptoms and a minimum neutrophils count of 150 μL. Conclusion MPV may be a predictor of PC recovery in dengue patients. PC recovery is expected when a patient has an MPV of 13.58 fL, an onset time of 4.5 d and a neutrophils count of 150 μL.