Saliva-based SARS-CoV-2 serology using at-home collection kits returned via mail

Viral infection and antiviral immunity in the oral cavity

Individual tissues have distinct antiviral properties garnered through various mechanisms, including physical characteristics, tissue-resident immune cells and commensal organisms. Although the oral mucosa has long been appreciated as a critical barrier tissue that is exposed to a continuous barrage of pathogens, many fundamental aspects of the antiviral immune response in this tissue remain unknown. Several viral pathogens, such as herpesviruses and human papillomaviruses, have been acknowledged both historically and at present for infections in the oral cavity that result in substantial clinical burden. However, recent viral outbreaks, including those with SARS-CoV-2 and mpox, featured oral symptoms even though these viruses are not generally considered oral pathogens. Ensuing studies have shown that the oral cavity is an important locale for viral infection and potential transmission of newly emergent or re-emergent pathogens, highlighting the need for an increased understanding of the mechanisms of antiviral immunity at this site. In this Review, we provide a broad overview of antiviral immune responses in the oral cavity and discuss common viral infections and their manifestations in the oral mucosa. In addition, we present current mouse models for the study of oral viral infections.

The omicron variant of SARS-CoV-2 drove broadly increased seroprevalence in a public university setting

Omicron is the comparatively most transmissible and contagious variant of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). We conducted a seroprevalence study from March 1-3, 2022, to investigate the seroprevalence of SARS-CoV-2 antibodies among individuals aged 18 years and older after the Omicron outbreak. The seroprevalence of anti-receptor binding domain (RBD) antibodies was found to be 96.3% (95% CI 95.2-97.2%) compared to 88.2% (95% CI 86.1-90%) in our previous serosurvey. For anti-nucleocapsid (NC) antibodies, the seroprevalence was 39.1% (95% CI 36.6-41.7%) compared to 19.7% (95% CI 17.5-22.2%) earlier. Individuals that experienced breakthrough infections exhibited the highest levels of anti-RBD antibodies. Additionally, saliva samples showed promise as a potential diagnostic biofluid for measuring antibody levels, as they exhibited a strong agreement with the data obtained from serum samples. The near doubling of anti-NC reactivity, a proxy for history of infection, reflects the contagiousness of the omicron variant, but may also have been influenced by a more relaxed approach to precautions in the spring of 2022. Serosurveys repeated at regular intervals monitor the trend of infections in the community, delineate the geographical spread of the infection, and may guide containment measures in communities, and prompt response to future outbreaks.

Applications of SARS-CoV-2 serological testing: impact of test performance, sample matrices, and patient characteristics

Laboratory testing has been a key tool in managing the SARS-CoV-2 global pandemic. While rapid antigen and PCR testing has proven useful for diagnosing acute SARS-CoV-2 infections, additional testing methods are required to understand the long-term impact of SARS-CoV-2 infections on immune response. Serological testing, a well-documented laboratory practice, measures the presence of antibodies in a sample to uncover information about host immunity. Although proposed applications of serological testing for clinical use have previously been limited, current research into SARS-CoV-2 has shown growing utility for serological methods in these settings. To name a few, serological testing has been used to identify patients with past infections and long-term active disease and to monitor vaccine efficacy. Test utility and result interpretation, however, are often complicated by factors that include poor test sensitivity early in infection, lack of immune response in some individuals, overlying infection and vaccination responses, lack of standardization of antibody titers/levels between instruments, unknown titers that confer immune protection, and large between-individual biological variation following infection or vaccination. Thus, the three major components of this review will examine (1) factors that affect serological test utility: test performance, testing matrices, seroprevalence concerns and viral variants, (2) patient factors that affect serological response: timing of sampling, age, sex, body mass index, immunosuppression and vaccination, and (3) informative applications of serological testing: identifying past infection, immune surveillance to guide health practices, and examination of protective immunity. SARS-CoV-2 serological testing should be beneficial for clinical care if it is implemented appropriately. However, as with other laboratory developed tests, use of SARS-CoV-2 serology as a testing modality warrants careful consideration of testing limitations and evaluation of its clinical utility.

Sensitive Serology Measurements in the Saliva of Individuals with COVID-19 Symptoms Using a Multiplexed Immunoassay

BACKGROUND

There are numerous benefits to performing salivary serology measurements for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen for coronavirus disease 2019 (COVID-19). Here, we used a sensitive multiplex serology assay to quantitate salivary IgG against 4 SARS-CoV-2 antigens: nucleocapsid, receptor-binding domain, spike, and N-terminal domain.

METHODS

We used single samples from 90 individuals with COVID-19 diagnosis collected at 0 to 42 days postsymptom onset (PSO) and from 15 uninfected control subjects. The infected individuals were segmented in 4 groups (0-7 days, 8-14 days, 15-21 days, and >21 days) based on days PSO, and values were compared to controls.

RESULTS

Compared to controls, infected individuals showed higher levels of antibodies against all antigens starting from 8 days PSO. When applying cut-offs with at least 93.3% specificity at every time interval segment, nucleocapsid protein serology had the best sensitivity at 0 to 7 days PSO (60% sensitivity [35.75% to 80.18%], ROC area under the curve [AUC] = 0.73, P = 0.034). Receptor-binding domain serology had the best sensitivity at 8 to 14 days PSO (83.33% sensitivity [66.44%-92.66%], ROC AUC = 0.90, P < 0.0001), and all assays except for N-terminal domain had 92% sensitivity (75.03%-98.58%) at >14 days PSO.

CONCLUSIONS

This study shows that our multiplexed immunoassay can distinguish infected from uninfected individuals and reliably (93.3% specificity) detect seroconversion (in 60% of infected individuals) as early as the first week PSO, using easy-to-collect saliva samples.