Detection of immunoglobulins specific to SARS-CoV-2 virus S-protein in mixed saliva

BACKGROUND: Since the beginning of the COVID-19 pandemic, scientists have been concerned about finding an effective alternative to blood-based diagnostics of antibodies to SARS-CoV-2. According to the results of numerous studies by domestic and foreign authors, saliva is a valuable diagnostic material. Mixed saliva implies the possibility of painless and non-invasive sampling and opens up great opportunities for diagnosing COVID-19 in vulnerable populations, such as children.

AIM: Development of a method for detecting immunoglobulins specific to the SARS-CoV-2 virus in saliva after infection with COVID-19 and vaccination.

MATERIALS AND METHODS: The study involved 43 people aged 20 to 67 years, divided into 3 groups: recovered from COVID-19; those who believe they have not had COVID-19; vaccinated with various drugs against COVID-19. Samples of unstimulated mixed saliva and capillary blood from a finger were obtained from each subject, which were subsequently examined by methods of qualitative and quantitative enzyme immunoassay.

RESULTS: A high level of correlation between the content of local IgG and IgA in saliva was demonstrated, while the relationship between the content of IgA in blood and saliva was shown to be of medium strength. A higher number of seropositive patients was demonstrated in the group vaccinated with vaccines against SARS-CoV-2, compared with those who recovered from COVID-19, which is consistent with the anamnesis data.

CONCLUSIONS: This work demonstrates and confirms that saliva in the oral fluid is a valuable diagnostic material for the study of local antibodies. The data obtained will allow the development of unique test systems for studying humoral immunity to the SARS-CoV-2 virus, which can become an alternative replacement for the usual determination of virus-specific immunoglobulins in the blood.