RESUMEN
BackgroundViral shedding patterns and its correlation with the immune responses of mildly symptomatic COVID-19 patients are still poorly characterized. MethodsWe enrolled the first five COVID-19 patients quarantined in our institution; none received immunomodulatory treatment. We monitored shedding of viral RNA and infectious virus by RT-PCR and cell culture from the upper respiratory tract, and characterized the kinetics of systemic innate and adaptive immune responses. ResultsDespite mild clinical disease, high viral loads and shedding of infectious virus were observed from the respiratory tract, with isolation of infectious virus and prolonged positivity by PCR up to day 7 and 19 post onset of symptoms, respectively. Robust innate responses characterized by an increase in activated CD14+CD16+ monocytes and cytokine responses were observed as early as 2 days after symptoms onset. Cellular and humoral SARS-CoV-2 specific adaptive responses were detectable in all patients. ConclusionInfectious virus shedding was limited to the first week of symptom onset in mild cases. A strong innate response, characterized by the mobilization of activated monocytes during the first days of infection, as well as SARS-CoV-2 specific antibodies were detectable, even in patients with mild disease. SummaryWe describe viral and immune profiles of the first five SARS-CoV-2 patients in our institution, showing high viral loads and infectious viral shedding in early acute disease. Mild patients mount an innate response sufficient for viral control and specific immunity.
RESUMEN
Children are underrepresented in COVID-19 case numbers, with most pediatric cases exhibiting limited severity, and do not seem to be major drivers of transmission, unlike for other respiratory viruses. That said, SARS-CoV-2 infects children across all age groups, and despite the high proportion of mild or asymptomatic infections, it would be naive not to consider them as transmitters. To address this point we used cell culture to systematically assess the presence of cultivable SARS-CoV-2 in the upper respiratory tract in a cohort of our institutions first 23 symptomatic neonates, children and teenagers with COVID-19 diagnosed by RT-PCR. Median age was 12.0 years (interquartile range [IQR 3.8-14.5], range 7 days-15.9 yrs). Most patients had an upper respiratory tract infection (n=13), followed by fever without source and pneumonia (each, n=2). Samples were collected at a median of 2 days (IQR 1-3) after symptom onset. Median viral load (VL) at time of diagnosis was 3.0x106 copies/ml (mean 4,4x108, IQR 6.9x103-4.4x108) from a nasopharyngeal swab (NPS). SARS-CoV-2 virus isolation was successful in 12/23 (52%) children after inoculating VeroE6 cells with a NPS specimen. SARS-CoV-2 isolation was determined by the presence of a typical cytopathic effect (CPE) and increased viral RNA in the supernatant. SARS-CoV-2 replication in all positive isolates (12/12) was confirmed by a second passage using new VeroE6 cells. Virus isolation was successful from NPS from all age groups, with a median initial VL of 1.7x108 copies/ml (mean 7.9x108, IQR 4.7x106-1.0x109) (Figure 1). The youngest patient that SARS-CoV-2 was isolated from was a 7-day old neonate. No correlation between disease presentation and success of virus isolation was observed. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=148 SRC="FIGDIR/small/20076778v1_fig1.gif" ALT="Figure 1"> View larger version (13K): org.highwire.dtl.DTLVardef@1bba3e8org.highwire.dtl.DTLVardef@60051org.highwire.dtl.DTLVardef@1fecf15org.highwire.dtl.DTLVardef@1cd90a0_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Breakdown of SARS-CoV-2 initial viral load of nasopharyngeal swabs among culture-negative and culture-positive specimens The thick and thin horizontal bars represent the median viral load and the interquartile range, respectively. *: specimen collected outside institution, suggesting a longer time to freezing at -80{degrees}C; #: specimen with a duration between collection and freezing at -80{degrees}C around 48 hours. SARS-CoV-2: severe acute respiratory syndrome coronavirus 2 C_FIG Our data show that initial VLs at diagnosis in symptomatic children is comparable to those in adults, and that symptomatic children of all ages shed infectious virus in early acute illness. Infectious virus isolation success was largely comparable to that of adults, although two specimens yielded an isolate at a lower VL (1.2x104 and 1.4x105 copies/ml) than what was observed in adults. SARS-CoV-2 shedding patterns of culture competent virus in symptomatic children resemble those observed in adults. Therefore, transmission of SARS-CoV-2 from children is plausible. Considering the relatively low frequency of infected children at this time, biological or other unknown factors could reduce transmission in this population. Both large serological investigations and systematic surveillance of acute respiratory diseases are needed to understand the role of children in this new pandemic.
