Abstract
COVID-19 affects children to a lesser extent than adults but they can still get infected and transmit SARS-CoV-2 to their contacts. Field deployable non-invasive sensitive diagnostic techniques are needed to evaluate the infectivity dynamics of SARS-CoV-2 in pediatric populations and guide public health interventions, particularly if this population is not fully vaccinated. We evaluated the utility of high-throughput Luminex assays to quantify saliva IgM, IgA and IgG antibodies against five SARS-CoV-2 spike (S) and nucleocapsid (N) antigens in a contacts and infectivity longitudinal study in 122 individuals (52 children and 70 adults). We compared saliva versus serum/plasma samples in infected children and adults diagnosed by weekly RT-PCR over 35 days (n=62), and those who consistently tested negative over the same follow up period (n=60), in the Summer of 2020 in Barcelona, Spain. Saliva antibody levels in SARS-CoV-2 RT-PCR positive individuals were significantly higher than in negative individuals and correlated with those measured in sera/plasmas. Asymptomatic infected individuals had higher levels of anti-S IgG than symptomatic individuals, suggesting a protective anti-disease role for antibodies. Higher anti-S IgG and IgM levels in serum/plasma and saliva, respectively, in infected children compared to infected adults could also be related to stronger clinical immunity in them. Among infected children, males had higher levels of saliva IgG to N and RBD than females. Despite overall correlation, individual clustering analysis suggested that responses that may not be detected in blood could be patent in saliva, and vice versa.In conclusion, measurement of SARS-CoV-2-specific saliva antibodies should be considered as a complementary non-invasive assay to serum/plasma to determine COVID-19 prevalence and transmission in pediatric populations before and after vaccination campaigns.
Highlights
Since the start of the COVID-19 pandemic, it has become apparent that pediatric populations are less affected than adult or older populations [1, 2], studies have found children and adults to be infected to a similar low degree [3]
We compared the levels of IgM, IgA and IgG antibodies to five SARS-CoV-2 antigens in saliva and serum/ plasma samples from RT-PCR positive and negative individuals
The magnitude of antibody responses was substantially lower in saliva than serum/plasma samples despite being measured at a higher concentration
Summary
Since the start of the COVID-19 pandemic, it has become apparent that pediatric populations are less affected than adult or older populations [1, 2], studies have found children and adults to be infected to a similar low degree [3]. Clinical presentation of SARS-CoV-2 infection is milder in children, with more proportion of asymptomatic cases [1, 4–6]. One hypothesis for this lower severity of COVID-19 is the protective effect that antibodies from human coronaviruses of the common cold (HCoV), which are more prevalent in children, could exert on SARS-CoV-2 control, considering cross-reactivity between them [7, 8]. Children could be harboring lower viral loads, in part due to the lower expression of ACE2, receptor of the coronavirus [9]. This implies that highly sensitive techniques might be required for its accurate diagnosis. Having field deployable diagnostic tools to monitor infectivity dynamics in school-like environments is very relevant from the public health perspective
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