Prevalence of Salivary IgA Reacting with SARS-CoV-2 among Japanese People Unexposed to the Virus

While the COVID-19 pandemic caused by SARS-CoV-2 has posed a threat to public health as the number of cases and COVID-19-related deaths are increasing worldwide, the incidence of the virus infection are extremely low in Japan compared with many other countries. To explore the reason for this strange phenomenon, we hypothesized the high prevalence of natural secretory IgA in saliva as mucosal IgA reacting with SARS-CoV-2, and thus surveyed the positivity for, as well as levels of, such reactive salivary IgA in a cohort of Japanese people of a wide range of age. The major findings were that 95/180 (52.78 %) of overall individuals who had not been exposed to SARS-CoV-2 were positive for salivary IgA with the levels ranging from 0.002 to 3.272 ng/ml, and that there may be a negative trend in positivity for salivary IgA according to age. These results suggest a role of mucosal IgA in host defense against SARS-CoV-2 infection.

A Comparative Quantitative Assessment of Salivary Iga and Alpha Amylase in Caries Free and Caries Active Children

Objectives: The aim of the study was to assess the salivary IgA (immunoglobulin A) and alpha amylase levels in the unstimulated whole saliva samples of caries-free and caries-active children and correlate it with the caries status and age. Study design: The salivary IgA and amylase was investigated in 100 children in the range of 8–12 years divided in two groups, control group (DMFT and/or deft = 0) and study group (DMFT/deft score ≥5). The salivary IgA was measured using kit based on two-site sandwich enzyme immunoassay principle and amylase was estimated using the vitro amyl slides. Results :The mean salivary IgA and amylase levels in the saliva of the children in the control group was found to be significantly increased (p=.001 and p=.014 respectively) whereas the relationship between salivary IgA and amylase levels in the saliva of the children was found to be insignificant with the age (p=.392 and p=.306 respectively). Conclusions: The results indicated that salivary IgA and amylase levels in saliva increased significantly in caries free children and the level of salivary IgA and alpha amylase has no significant relation with the age of the children.

Impact of the harsh Antarctic environment on mucosal immunity

Mucosal immunity of Indian Antarctic personnel was analysed during the 34th Indian Scientific Expedition to Antarctica (ISEA) by ship voyage. Serum and salivary IgA, IgA1 and IgA2 levels along with salivary cortisol and TGF-β were quantified by enzyme-linked immunosorbent assay. Samples were collected at three different time points (T1, T2 and T3) during the expedition. Serum and salivary IgA, IgA1 and IgA2 concentrations incrementally increased towards the end of the expedition as compared to the beginning of the expedition. Salivary IgA and TGF-β levels were significantly altered during the expedition. Levels of IgA1 (P = 0.0007) and IgA2 (P = 0.0135) increased significantly at T3 as compared to T1. Additionally, significant changes in serum IgA were observed, with peak levels at T3 (P = 0.0015) and T2 (P < 0.001). However, the level of serum IgA2 was also significantly altered at T3 (P < 0.05) and T2 (P = 0.0006) in comparison with T1. The exact cause of the changes in serum and salivary IgA, IgA1, IgA2 and TGF-β levels during the summer expedition are unknown; however, the changes are evident in mucosal immunity.

Development and validation of an enzyme immunoassay for detection and quantification of SARS-CoV-2 salivary IgA and IgG

Oral fluids offer a non-invasive sampling method for the detection of antibodies. Quantification of IgA and IgG antibodies in saliva allows studies of the mucosal and systemic immune response after natural infection or vaccination. We developed and validated an enzyme immunoassay (EIA) to detect and quantify salivary IgA and IgG antibodies against the prefusion-stabilized form of the SARS-CoV-2 spike protein. Normalization against total antibody isotype was performed to account for specimen differences, such as collection time and sample volume. Saliva samples collected from 187 SARS-CoV-2 confirmed cases enrolled in 2 cohorts and 373 pre-pandemic saliva samples were tested. The sensitivity of both EIAs was high (IgA: 95.5%; IgG: 89.7%) without compromising specificity (IgA: 99%; IgG: 97%). No cross reactivity with seasonal coronaviruses was observed. The limit of detection for SARS-CoV-2 salivary IgA and IgG assays were 1.98 ng/mL and 0.30 ng/mL, respectively. Salivary IgA and IgG antibodies were detected earlier in patients with mild COVID-19 symptoms than in severe cases. However, severe cases showed higher salivary antibody titers than those with a mild infection. Salivary IgA titers quickly decreased after 6 weeks in mild cases but remained detectable until at least week 10 in severe cases. Salivary IgG titers remained high for all patients, regardless of disease severity. In conclusion, EIAs for both IgA and IgG had high specificity and sensitivity for the confirmation of current or recent SARS-CoV-2 infections and evaluation of the IgA and IgG immune response.

Relationship between Training Load Management and Immunoglobulin A to Avoid Immunosuppression after Soccer Training and Competition: A Theoretical Framework Based on COVID-19 for Athletes’ Healthcare

Immunoglobulin A (IgA), which is the main effector against upper respiratory tract viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been related to training load management. The aim of this systematic review was to establish the relationship between training load and salivary IgA based on current evidence in order to avoid immunosuppression after exercise and players´ vulnerability to virus contagion. A systematic review of relevant articles was carried out using two electronic databases (PubMed and Web of Science) until 19 May 2021. From a total of 127 studies initially found, 23 were included in the qualitative synthesis. These studies were clustered depending on stress level. The salivary IgA was analysed considering soccer-specific treadmill exercise and repeated sprint drills (n = 5), matches (n = 7), and during certain periods during the season or pre-season (n = 11). Repeated sprint ability tests and treadmill exercises are suitable exercises for the first steps on return to play periods yet still maintain social distance. A rest or moderate training sessions (technical/tactical) are suggested after official matches to ensure 16–18 h to recover IgA levels, while periods with multiple matches per week with limited recovery time should be avoided. Weekly training load should assume a small increment (<10%) to ensure IgA immune responses, especially, during the post coronavirus disease 2019 (COVID-19) season.

The Alteration of Salivary Immunoglobulin A in Autism Spectrum Disorders

Objectives: Autism spectrum disorders (ASD) are neurodevelopmental disorders with changes in the gut and oral microbiota. Based on the intimate relationship between the oral microbiota and oral mucosal immunity, this study aimed to investigate changes in salivary immunoglobulin A (IgA) level in ASD and the underlying mechanism for any such changes.Methods: We recruited 36 children diagnosed with ASD and 35 normally developing children and measured their salivary IgA content using enzyme-linked immunosorbent assay (ELISA). The valproate (VPA) -treated ASD mouse model was established by prenatal exposure to valproate and mouse salivary IgA content was also quantified by ELISA. The submandibular glands of VPA and control mice were isolated and analyzed using qRT-PCR, immunofluorescence staining, and flow cytometry. ASD-related Streptococci were co-incubated with the human salivary gland (HSG) cell line, and western blotting was used to detect the levels of relevant proteins.Results: We found that salivary IgA content was significantly decreased in patients with ASD and had a significant ASD diagnostic value. The salivary IgA content also decreased in VPA mice and was significantly correlated with autistic-like behaviors among them. The mRNA and protein levels of the polymeric immunoglobulin receptor (Pigr) were downregulated in the submandibular glands of VPA mice and the Pigr mRNA level was positively correlated with mouse salivary IgA content. HSG cells treated with ASD-related Streptococci had reduced PIGR protein level.Conclusion: Therefore, protective IgA levels were reduced in the saliva of individuals with ASD, which correlated with the bacteria-induced downregulation of Pigr in salivary glands. This study suggests a new direction for ASD diagnosis and prevention of oral diseases in ASD cohorts and provides evidence for the ASD mucosal immunophenotype in the oral cavity.

Persisting Salivary IgG against SARS-CoV-2 at 9 Months After Mild COVID-19: A Complementary Approach to Population Surveys

Background: Declining humoral immunity in COVID-19 patients and possibility of reinfections has raised concern. Mucosal immunity particularly salivary antibodies could be short-lived. However, long-term studies are sparse. Methods: Using a multiplex bead-based array platform, we investigated antibodies specific to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins in 256 saliva samples from convalescent patients 1-9 months after symptomatic COVID-19 (n=74, Cohort 1), undiagnosed individuals with self-reported questionnaires (n=147, Cohort 2), and individuals sampled pre-pandemic time (n= 35, Cohort 3). Results: Salivary IgG antibody responses in Cohort 1 (mainly mild COVID-19) were detectable up to 9 month recovery, with high correlations between spike and nucleocapsid specificity. At 9 months, IgG remained in saliva in majority as seen in blood serology. Salivary IgA was rarely detected at this timepoint. In Cohort 2, salivary IgG and IgA responses were significantly associated with recent history of COVID-19 like symptoms. Salivary IgG also tolerated temperature and detergent pre-treatments. Conclusions: Unlike SARS-CoV-2 salivary IgA that appeared short-lived, the specific IgG in saliva appears stable even after mild COVID-19 as noted for blood serology. The non-invasive saliva-based SARS-Cov-2 antibody testing with self-collection at homes may thus serve as a complementary alternative to conventional blood serology.

Immune status, well-being and gut microbiota in military supplemented with synbiotic ice cream and submitted to field training: a randomised clinical trial

Strenuous physical activity, sleep deprivation, and psychological stress are common features of military field training. This study aimed to evaluate the effects of supplementation with a synbiotic ice cream on salivary IgA, gastrointestinal symptoms, well-being indicators, and gut microbiota in young military participants undergoing field training. Sixty-five military completed the study: one group was supplemented for 30 days with synbiotic ice cream containing: 2.1x108 CFU/g for L. acidophilus LA-5 and 2.7x109 CFU/g for B. animalis BB-12 and 2.3g of inulin in the 60g of ice cream at manufacture, and the other with a placebo ice cream. Volunteers were evaluated at pre-supplementation (baseline), post-supplementation, and after a five-day military training. Bifidobacterium and Lactobacillus genera were measured in stool samples and both showed a higher differential abundance post-supplementation and training. Salivary IgA and gastrointestinal symptoms decreased at post-training in both groups (p<0.05; main effect of time); however, supplementation with synbiotic did not mitigate this effect. Tenseness and sleepiness were decreased in the synbiotic-treated group, but not in the placebo group at post-military training (p=0.01 and p=0.009, respectively; group x time effect). The other well-being indicators were not affected by the synbiotic supplementation. In conclusion, 30 days of synbiotic ice cream supplementation containing inulin, L. acidophilus LA-5, and B. animalis BB-12 favourably modulated gut microbiota and improved tenseness and sleepiness in healthy young military undergoing a 5-day field training. These improvements may be relevant to this population as they may influence the decision-making process in an environment of high physical and psychological stress.