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Interferon (IFN)-specific autoantibodies have been implicated in severe coronavirus disease 2019 (COVID-19) and have been proposed as a potential driver of the persistent symptoms characterizing "long COVID," a type of postacute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We report that only 2 of 215 participants with convalescent SARS-CoV-2 infection tested over 394 time points, including 121 people experiencing long COVID symptoms, had detectable IFN-α2 antibodies. Both had been hospitalized during the acute phase of the infection. These data suggest that persistent anti-IFN antibodies, although a potential driver of severe COVID-19, are unlikely to contribute to long COVID symptoms in the postacute phase of the infection.

Background. During the ongoing COVID-19 pandemic and in the season of rising incidence of other respiratory infections, it is relevant to use preventive measures of non-specific prophylaxis. Synthetic peptides are widely considered as a tool. The representative of this group is the synthetic analogue of thymus regulatory peptides Thymogen, which has been used in Russia for more than 20 years in the treatment of acute and chronic infection diseases.The aim of the study. To evaluate the effect of Thymogen, a dosed nasal spray, on induced parameters of the immune system during prophylactic use in healthy volunteers.Materials and methods. Twenty healthy volunteers received Thymogen nasal dosed spray (JSC “Cytomed”, Russia) at a dose of 25 μg twice a day for 10 days. A comparative assessment of immunological parameters was carried out in dynamics: before the start of therapy, on days 6 and 11 of taking the drug and 14 days after the end of the course. Clinical observation was carried out from day 1 to day 11, registration of adverse events – the entire period of the study for 24 days. The first day was considered the day the drug was started.Results. In the course of the work, according to the data of immunological examination, a statistically significant increase in the virus-induced production of interferon alpha (INF-α) by a culture of peripheral blood cells was revealed. The growth rate was recorded on day 11 of taking Thymogen and persisted for 14 days after the end of the course. Significant differences in the dynamics of bactericidal and phagocytic activity of neutrophils, serum α- and γ-interferon were not obtained.Conclusion. The use of Thymogen spray at a dose of 25 μg for 10 days was safe and contributed to a significant induction of interferon-alpha in response to exposure to a viral pathogen, which allows us to recommend the drug for prophylactic use during the period of rising incidence of acute respiratory diseases.