General dynamics of the URT microbiome and microbial signs of recovery in COVID-19 patients.

COVID-19 is caused by an airborne virus, SARS-CoV-2. The upper respiratory tract (URT) is, therefore, the first system to endure the attack. Inhabited by an assemblage of microbial communities, a healthy URT wards off the invasion. However, once invaded, it becomes destabilised, which could be crucial to the establishment and progression of the infection. We examined 696 URT samples collected from 285 COVID-19 patients at three time-points throughout their hospital stay and 100 URT samples from 100 healthy controls. We used 16S ribosomal RNA sequencing to evaluate the abundance of various bacterial taxa, α-diversity, and ß-diversity of the URT microbiome. Ordinary least squares regression was used to establish associations between the variables, with age, sex, and antibiotics as covariates. The URT microbiome in the COVID-19 patients was distinctively different from that of healthy controls. In COVID-19 patients, the abundance of 16 genera was significantly reduced. A total of 47 genera were specific to patients, whereas only 2 were unique to controls. The URT samples collected at admission differed more from the control than from the samples collected at later stages of treatment. The following four genera originally depleted in the patients grew significantly by the end of treatment: Fusobacterium, Haemophilus, Neisseria, and Stenotrophomonas. Our findings strongly suggest that SARS-CoV-2 caused significant changes in the URT microbiome, including the emergence of numerous atypical taxa. These findings may indicate increased instability of the URT microbiome in COVID-19 patients. In the course of the treatment, the microbial composition of the URT of COVID-19 patients tended toward that of controls. These microbial changes may be interpreted as markers of recovery.

[The effect of recombinant tumor necrosis factor on antibody formation in mice immunized with a preparation of the outer membranes from Francisella tularensis]. / Vliianie rekombinantnogo faktora nekroza opukholi na antitelogenez u myshei, immunizirovannykh preparatom vneshnikh membran Francisella tularensis.

The influence of exogenic human recombinant tumor necrosis factor (TNF-alpha) on antibody production in mice immunized with the preparation of F.tularensis outer membranes (OM) was studied. TNF-alpha was injected into mice in doses of 0.001-10 I.U. before and simultaneously with the injection of the preparation of F.tularensis OM. The levels of tularemia antibodies, determined by ELISA techniques, and the number of antibody-producing cells (APC) were studied. The study revealed that recombinant TNF-alpha in the range of doses used in this investigation stimulated the formation of humoral immunity. The injection of TNF-alpha in a dose of 0.001 I.U. was found to produce the most pronounced effect on the level of tularemia antibodies and the number of antibody-producing cells. The use TNF-alpha as immunomodulator made it possible to decrease the dose of the preparation of F.tularensis OM introduced as immunogenic agent without essential changes in the number of splenic APC and in the level of tularemia antibodies.

[The characteristics of the antibody response of animals immunized with components of the surface structures of Francisella tularensis]. / Osobennosti antitel'nogo otveta u zhivotnykh, immunizirovannykh komponentami poverkhnostnykh struktur Francisella tularensis]

Antibody formation in animals immunized with one of the components of F. tularensis surface structures was studied. The time course of antibody formation in 20 hamadryas baboons was studied in the passive hemagglutination (PHA) test, microagglutination (MA) test, and indirect enzyme immunoassay, used for the determination of IgG, IgA and IgM antibodies. The character of antibody response in the animals immunized with components of F. tularensis surface structures (S-complex) and with live tularemia vaccine was compared. The study revealed that immunization with the S-complex induced the formation of antibodies detected by all three methods. Antibody formation to the S-complex was found to be dose-dependent. With the increase of the injected dose of the S-complex, antibody titers determined in the PHA test decreased and those determined in the MA test increased, which was seemingly due to the induction of antibodies differing in their isotypes. After immunization with the S-complex the levels of IgG antibodies were lower and the levels of IgM antibodies by day 28 after immunization higher than after the injection of live tularemia vaccine.

[The use of microdot immunoenzyme analysis with visual detection for the determination of tularemia antibodies]. / Ispol'zovanie mikrotochechnogo immunofermentnogo analiza s vizual'noi indikatsiei dlia opredeleniia tuliaremiinykh antitel.

The possibility of using the micropoint enzyme immunoassay (EIA) on a nitrocellulose membrane with the visual evaluation of results for the detection of tularemia IgG antibodies in hamadryas baboons at the postvaccinal period has been studied. The sensitivity of this assay has been compared with that of the passive hemagglutination (PHA) test, the microagglutination (MA) test and EIA with the spectrophotometric evaluation of results in plates. As shown in this study, EIA in the above-mentioned modification can be successfully used for the detection of tularemia antibodies in the blood serum. The sensitivity of micropoint EIA has proved to be not inferior to that of EIA in plates, while exceeding the sensitivity of the PHA test 10- to 20-fold and the sensitivity of the MA test 10- to 1,000-fold. This method is simple, reliable, highly sensitive, economic and requires no special equipment, which makes it highly promising for the diagnosis of tularemia and the evaluation of humoral immunity at the postvaccinal period.

[The efficacy of immunoenzyme assay in determining IgG in blood]. / Effektivnost' immunofermentnogo analiza dlia opredeleniia IgG v syvorotke krovi.

The efficacies of two methods for measuring human blood serum IgG, heterogenic enzyme immunoassay (EIA) and radial immunodiffusion in gel (RIG), are compared. The accuracy of both the methods was verified by the data of IgG spectrophotometry; IgG were isolated by ion exchange chromatography from human blood serum. The results of all the three methods were in high correlation: correlation coefficient of spectrophotometry and EIA data was 0.992, p less than 0.01; that of spectrophotometry and RIG data 0.975, p less than 0.01; that of RIG and EIA 0.888, p less than 0.01. Since EIA has some advantages over RIG (it is more rapid, sensitive, accurate, and the investigation may be automated), it is recommended for measuring human blood serum IgG in mass screenings.