Multiplex Antibody Analysis of IgM, IgA and IgG to SARS-CoV-2 in Saliva and Serum From Infected Children and Their Close Contacts

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.

Saliva antibody-fingerprint of reactivated latent viruses after mild/asymptomatic COVID-19 is unique in patients with myalgic-encephalomyelitis/chronic fatigue syndrome

“…Similar antibody levels in adult non-infected persons were also observed by Dobano et al. ( 30 ). RBD antibodies of IgG, IgM, IgA classes, were released locally onto the oral mucosa, as detected by antibody ‘fingerprinting’ in saliva in both cohorts: 42/95 (44%) of ME/CFS donors were RBD IgG + vs. 28/110 (25%) of HDs ( Figure 1B ).…”

“…For patients with ME/CFS, due to the presence of frequent flu-like symptoms, we could not draw any conclusions regarding COVID-19-related symptoms and relied on blood and saliva antibody levels for the definition of an asymptomatic/unknown infection. It is increasingly realized that local mucosal-innate immunity presents with a distinct signature, including interferon activity, and has important roles in SARS-CoV-2 defense ( 30 , 31 ).…”

Immunological memory to SARS‐CoV‐2 infection and COVID‐19 vaccines

“…The most dramatic example of this is the human papillomavirus (HPV) vaccine, which provides 99% protective immunity in the vaginal tract, even though the vaccine is a conventional intramuscular immunization and elicits circulating IgG. For SARS‐CoV‐2 previously infected individuals, the titers of circulating IgG correlate with saliva IgG, 56 , 190 , 197 and the correlation was sustained over a period of 9 months. 56 Correlation between circulating IgA and saliva IgA in previously infected individuals was also substantial over a 9‐month period.…”

One-Step Quantification of anti-Covid-19 Antibodies via Dual Affinity Ratiometric Quenching Assays

“…Saliva, on the other hand, offers a more viable route toward quantitative evaluation of SARS-CoV-2 infection: of special interest is the ability to quantify specific immunoglobulins raised against the virus and found in saliva to evaluate the nonspecific, innate immune response of the patient . While the salivary IgG and IgM concentrations are lower than their serum counterparts, the distribution and antigen specificity in the two fluids is rather similar . The presence of salivary IgM and IgG targeting the nucleoprotein (N-CoV-2) and spike protein receptor binding domain (RBD) has been described in patients after symptom onset, providing evidence that saliva can be used to assess the antibody response to coronavirus infections …”