Shedding of infectious SARS-CoV-2 in two asymptomatic children.

Asymptomatic infections with SARS-CoV-2 are associated with viral transmission and have a key role in the propagation of the pandemic. Understanding viral shedding during asymptomatic infections is critical. Unfortunately, data on asymptomatic SARS-CoV-2 infection in children is extremely limited. To determine the presence of viral viable shedding, we prospectively followed two healthy children of a family where both parents developed mild COVID-19 (April 2021). SARS-CoV-2 detection was made by RT-PCR and virus isolation by cell culture from saliva samples. Positive samples were sequenced to identify variants of SARS-CoV-2. Serum samples were evaluated to determine the presence of antibodies using a single enzyme-linked immunosorbent assay (ELISA, COVIDAR IgG). Both children were SARS-CoV-2 positive and asymptomatic. In addition, the virus grew in cell culture from saliva samples. Furthermore, one child showed viable SARS-CoV-2 for at least 17 days after the onset symptoms from his father. The recommended isolation period for asymptomatic contacts during the acquisition of data had been established for 10 days; however, this child remained with viable virus beyond that period. The positive samples from both children were consistent with B.1.1.28.1 lineage (Gamma). In both asymptomatic children, anti-Spike IgG was detected. Asymptomatic children may represent a source of infection that should not be underestimated during this pandemic.

Las infecciones asintomáticas por SARS-CoV-2 están asociadas a la transmisión viral y tienen un papel clave en la propagación de la pandemia. Comprender la excreción viral durante las infecciones asintomáticas es fundamental. Desafortunadamente, los datos sobre la infección asintomática por SARS-CoV-2 en niños son extremadamente limitados. Para determinar la presencia de excreción de virus viable, se siguió prospectivamente a dos niños sanos de una familia en la que ambos padres desarrollaron COVID-19 leve (abril 2021). La detección de SARS-CoV-2 se realizó por RT-PCR y el aislamiento del virus por cultivo celular a partir de muestras de saliva. Las muestras positivas se secuenciaron para identificar variantes de SARS-CoV-2. En las muestras de suero se determinó la presencia de anticuerpos utilizando un ensayo de ELISA (COVIDAR IgG). Ambos niños fueron positivos para SARS-CoV-2 y asintomáticos. Además, el virus creció en cultivos celulares a partir de muestras de saliva. Uno de los niños mantuvo SARS-CoV-2 viables durante al menos 17 días después de la aparición de los síntomas de su padre. El período de aislamiento recomendado para contactos asintomáticos durante la adquisición de datos se había establecido en 10 días, sin embargo, este niño permaneció con virus viable más allá de ese período. Las muestras positivas de estos niños correspondieron al linaje B.1.1.28.1 (Gamma). En ambos niños asintomáticos se detectó anticuerpos IgG anti-Spike. Concluimos que los niños asintomáticos pueden representar una fuente de infección que no debe subestimarse durante esta pandemia.

Humoral response and neutralising capacity at 6 months post-vaccination against COVID-19 among institutionalised older adults in Argentina

The COVID-19 pandemic has particularly affected older adults residing in nursing homes, resulting in high rates of hospitalisation and death. Here, we evaluated the longitudinal humoral response and neutralising capacity in plasma samples of volunteers vaccinated with different platforms (Sputnik V, BBIBP-CorV, and AZD1222). A cohort of 851 participants, mean age 83 (60-103 years), from the province of Buenos Aires, Argentina were included. Sequential plasma samples were taken at different time points after vaccination. After completing the vaccination schedule, infection-naïve volunteers who received either Sputnik V or AZD1222 exhibited significantly higher specific anti-Spike IgG titers than those who received BBIBP-CorV. Strong correlation between anti-Spike IgG titers and neutralising activity levels was evidenced at all times studied (rho=0.7 a 0.9). Previous exposure to SARS-CoV-2 and age <80 years were both associated with higher specific antibody levels. No differences in neutralising capacity were observed for the infection-naïve participants in either gender or age group. Similar to anti-Spike IgG titers, neutralising capacity decreased 3 to 9-fold at 6 months after initial vaccination for all platforms. Neutralising capacity against Omicron was between 10-58 fold lower compared to ancestral B.1 for all vaccine platforms at 21 days post dose 2 and 180 days post dose 1. This work provides evidence about the humoral response and neutralising capacity elicited by vaccination of a vulnerable elderly population. This data could be useful for pandemic management in defining public health policies, highlighting the need to apply reinforcements after a complete vaccination schedule.

Antibody response against SARS-CoV-2 variants of concern in children infected with pre-Omicron variants: An observational cohort study.

BACKGROUND: Despite that pediatric COVID-19 is usually asymptomatic or mild, SARS-CoV-2 infection typically results in the development of an antibody response. Contradictory observations have been reported when the antibody response of children and adults were compared in terms of strength, specificity and perdurability. METHODS: This observational study includes three cohorts infected with SARS-CoV-2 between March 2020-July 2021: unvaccinated infected children (n=115), unvaccinated infected adults (n=62), and vaccinated infected children (n=76). Plasma anti-spike IgG antibodies and neutralising activity against Wuhan, Delta and Omicron variants after 7-17 months post-infection were analysed. FINDINGS: More than 95% of unvaccinated infected children and adults remained seropositive when evaluated at 382-491 and 386-420 days after infection, respectively. Anti-spike IgG titers and plasma neutralising activity against Wuhan, Delta and Omicron variants were higher in children compared to adults. No differences were found when unvaccinated infected children were stratified by age, gender or presence/absence of symptoms in the acute phase of SARS-CoV-2 infection, but a slight decrease in the antibody response was observed in those with comorbidities. Vaccination of previously infected children with two doses of the inactivated BBIBP-CorV or the mRNA vaccines, BNT162b2 and/or mRNA-1273, further increased anti-spike IgG titers and neutralising activity against Wuhan, Delta and Omicron variants. INTERPRETATION: Unvaccinated infected children mount a more potent and sustained antibody response compared with adults, which is significantly increased after vaccination. Further studies including not only the analysis of the immune response but also the effectiveness to prevent reinfections by the different Omicron lineages are required to optimise vaccination strategy in children. FUNDING: National Agency for Scientific and Technological Promotion from Argentina (PICTO-COVID-SECUELAS-00007 and PMO-BID-PICT2018-2548).

Omicron Breakthrough Infection After Heterologous Prime-Boost Vaccination Induces a Vigorous Antibody Response.

Infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant is usually asymptomatic or mild and appears to be poorly immunogenic at least in unvaccinated individuals. Here, we found that health care workers vaccinated with 2 doses of Sputnik V and a booster dose of ChAdOx1 mount a vigorous neutralizing-antibody response after Omicron breakthrough infection.

Platelets modulate CD4+ T-cell function in COVID-19 through a PD-L1 dependent mechanism.

Severe COVID-19 is associated with a systemic inflammatory response and progressive CD4+ T-cell lymphopenia and dysfunction. We evaluated whether platelets might contribute to CD4+ T-cell dysfunction in COVID-19. We observed a high frequency of CD4+ T cell-platelet aggregates in COVID-19 inpatients that inversely correlated with lymphocyte counts. Platelets from COVID-19 inpatients but not from healthy donors (HD) inhibited the upregulation of CD25 expression and tumour necrosis factor (TNF)-α production by CD4+ T cells. In addition, interferon (IFN)-γ production was increased by platelets from HD but not from COVID-19 inpatients. A high expression of PD-L1 was found in platelets from COVID-19 patients to be inversely correlated with IFN-γ production by activated CD4+ T cells cocultured with platelets. We also found that a PD-L1-blocking antibody significantly restored platelets' ability to stimulate IFN-γ production by CD4+ T cells. Our study suggests that platelets might contribute to disease progression in COVID-19 not only by promoting thrombotic and inflammatory events, but also by affecting CD4+ T cells functionality.

Longitudinal Study after Sputnik V Vaccination Shows Durable SARS-CoV-2 Neutralizing Antibodies and Reduced Viral Variant Escape to Neutralization over Time.

Recent studies have shown a temporal increase in the neutralizing antibody potency and breadth to SARS-CoV-2 variants in coronavirus disease 2019 (COVID-19) convalescent individuals. Here, we examined longitudinal antibody responses and viral neutralizing capacity to the B.1 lineage virus (Wuhan related), to variants of concern (VOC; Alpha, Beta, Gamma, and Delta), and to a local variant of interest (VOI; Lambda) in volunteers receiving the Sputnik V vaccine in Argentina. Longitudinal serum samples (N = 536) collected from 118 volunteers obtained between January and October 2021 were used. The analysis indicates that while anti-spike IgG levels significantly wane over time, the neutralizing capacity for the Wuhan-related lineages of SARS-CoV-2 and VOC is maintained within 6 months of vaccination. In addition, an improved antibody cross-neutralizing ability for circulating variants of concern (Beta and Gamma) was observed over time postvaccination. The viral variants that displayed higher escape to neutralizing antibodies with respect to the original virus (Beta and Gamma variants) were the ones showing the largest increase in susceptibility to neutralization over time after vaccination. Our observations indicate that serum neutralizing antibodies are maintained for at least 6 months and show a reduction of VOC escape to neutralizing antibodies over time after vaccination. IMPORTANCE Vaccines have been produced in record time for SARS-CoV-2, offering the possibility of halting the global pandemic. However, inequalities in vaccine accessibility in different regions of the world create a need to increase international cooperation. Sputnik V is a recombinant adenovirus-based vaccine that has been widely used in Argentina and other developing countries, but limited information is available about its elicited immune responses. Here, we examined longitudinal antibody levels and viral neutralizing capacity elicited by Sputnik V vaccination. Using a cohort of 118 volunteers, we found that while anti-spike antibodies wane over time, the neutralizing capacity to viral variants of concern and local variants of interest is maintained within 4 months of vaccination. In addition, we observed an increased cross-neutralization activity over time for the Beta and Gamma variants. This study provides valuable information about the immune response generated by a vaccine platform used in many parts of the world.

A poor and delayed anti-SARS-CoV2 IgG response is associated to severe COVID-19 in children.

BACKGROUND: Most children and youth develop mild or asymptomatic disease during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, a very small number of patients suffer severe Coronavirus induced disease 2019 (COVID-19). The reasons underlying these different outcomes remain unknown. METHODS: We analyzed three different cohorts: children with acute infection (n=550), convalescent children (n=138), and MIS-C (multisystem inflammatory syndrome in children, n=42). IgG and IgM antibodies to the spike protein of SARS-CoV-2, serum-neutralizing activity, plasma cytokine levels, and the frequency of circulating Follicular T helper cells (cTfh) and plasmablasts were analyzed by conventional methods. FINDINGS: Fifty-eight percent of the children in the acute phase of infection had no detectable antibodies at the time of sampling while a seronegative status was found in 25% and 12% of convalescent and MIS-C children, respectively. When children in the acute phase of the infection were stratified according disease severity, we found that contrasting with the response of children with asymptomatic, mild and moderate disease, children with severe COVID-19 did not develop any detectable response. A defective antibody response was also observed in the convalescent cohort for children with severe disease at the time of admission. This poor antibody response was associated to both, a low frequency of cTfh and a high plasma concentration of inflammatory cytokines. INTERPRETATION: A weak and delayed kinetic of antibody response to SARS-CoV-2 together with a systemic pro-inflammatory profile characterize pediatric severe COVID-19. Because comorbidities are highly prevalent in children with severe COVID-19, further studies are needed to clarify their contribution in the weak antibody response observed in severe disease. FUNDING: National Agency for Scientific and Technological Promotion from Argentina (IP-COVID-19-0277 and PMO-BID-PICT2018-2548).

AHR signaling is induced by infection with coronaviruses.

Coronavirus infection in humans is usually associated to respiratory tract illnesses, ranging in severity from mild to life-threatening respiratory failure. The aryl hydrocarbon receptor (AHR) was recently identified as a host factor for Zika and dengue viruses; AHR antagonists boost antiviral immunity, decrease viral titers and ameliorate Zika-induced pathology in vivo. Here we report that AHR is activated by infection with different coronaviruses, potentially impacting antiviral immunity and lung epithelial cells. Indeed, the analysis of single-cell RNA-seq from lung tissue detected increased expression of AHR and AHR transcriptional targets, suggesting AHR signaling activation in SARS-CoV-2-infected epithelial cells from COVID-19 patients. Moreover, we detected an association between AHR expression and viral load in SARS-CoV-2 infected patients. Finally, we found that the pharmacological inhibition of AHR suppressed the replication in vitro of one of the causative agents of the common cold, HCoV-229E, and the causative agent of the COVID-19 pandemic, SARS-CoV-2. Taken together, these findings suggest that AHR activation is a common strategy used by coronaviruses to evade antiviral immunity and promote viral replication, which may also contribute to lung pathology. Future studies should further evaluate the potential of AHR as a target for host-directed antiviral therapy.

Immunoglobulin G Immune Complexes May Contribute to Neutrophil Activation in the Course of Severe Coronavirus Disease 2019.

Severe coronavirus disease 2019 (COVID-19) is associated with an overactive inflammatory response mediated by macrophages. Here, we analyzed the phenotype and function of neutrophils in patients with COVID-19. We found that neutrophils from patients with severe COVID-19 express high levels of CD11b and CD66b, spontaneously produce CXCL8 and CCL2, and show a strong association with platelets. Production of CXCL8 correlated with plasma concentrations of lactate dehydrogenase and D-dimer. Whole blood assays revealed that neutrophils from patients with severe COVID-19 show a clear association with immunoglobulin G (IgG) immune complexes. Moreover, we found that sera from patients with severe disease contain high levels of immune complexes and activate neutrophils through a mechanism partially dependent on FcγRII (CD32). Interestingly, when integrated in immune complexes, anti-severe acute respiratory syndrome coronavirus 2 IgG antibodies from patients with severe COVID-19 displayed a higher proinflammatory profile compared with antibodies from patients with mild disease. Our study suggests that IgG immune complexes might promote the acquisition of an inflammatory signature by neutrophils, worsening the course of COVID-19.