[Point mutations in tox promoter/operator and diphtheria toxin repressor (DTXR) gene associated with the level of toxin production by Corynebacterium diphtheriae strains isolated in Belarus].

DNA fragments 129 bp in length containing promoter region of the tox gene from 81 toxigenic strains Corynebacterium diphtheriae were analyzed using the SSCP (single strand conformational polymorphism). We found that only two strains had mutations; the strains also had highest levels of toxin production (over 5120 Vero CD50/ml). Other strains were characterized either as high-level toxin-producing (640-5120 Vero CD50/ml, 41 strains) or low-level toxin-producing (40-320 Vero CD50/ml, 38 strains). Nucleotide sequence analysis revealed single T to C mutations at positions -54 and -184 within -232 - +85 region of tox operon. The first mutation at the -184 position was mapped outside the tox promoter/operator, whereas the second substitution at the -54 position modified the 9-base-pair interrupted palindromic sequence of the tox promoter/operator from ATAATTAGG in the wild-type bacteriophage (to ACAATTAGG in strains with enhanced level of toxin production. Nucleotide sequence analysis of -76 - +681 region of diphtheria toxin repressor (dtxR) gene from 15 strains of C. diphtheriae revealed two missense mutations resulting in amino acid substitutions A 147 V; and L 214 I in the C-terminal region of the DtxR protein. Seven of these strains were identified as high-level toxin-producing and 4 strains, as low-level toxin-producing. In addition, one low-level toxin-producing strain was shown to contain a missense mutation leading to amino acid substitution I 221 T. Three strains, including two highest-level toxin producing strains contained no nucleotide substitutions, as well as the C7(-) strain. The 10 strains belonging to the Sankt-Peterburg and Rossija epidemic ribotypes as well as NCTC 13129 strain (etiologic agent of the diphtheria epidemic outbreak in the Eastern Europe) was shown to contain two mutations A 147 V and L 214 I in the C-terminal region of the DtxR protein.

[RNA-protein interactions in influenza virus A ribonucleoprotein detected by UV radiation]. / RNK-belkovye vzaimodeistviia v ribonukleoproteide virusa grippa A, vyiavliaemye pri UF-obluchenii.

RNA and protein interaction in the structure of influenza virus ribonucleoprotein (RNP) was studied by ultraviolet (UV) irradiation. After UV-irradiation of virion RNP for 1 hour only 6% of 3H-uridine-labeled RNA was found to go into the aqueous phase upon phenol-detergent extraction. Pretreatment of RNP with small doses of pancreatic RNase before RNA extraction slightly increased (up to 18%) the amount of RNA going into the aqueous phase. About 90% RNA was found after extraction in the aqueous phase in the nonirradiated material. As a result of UV-irradiation of RNP, RNA in RNP became more resistant to RNase: the residual acid-insoluble radioactivity was 21% whereas with nonirradiated RNP it was 3.2%. The results of the analysis of RNP labeled for protein in polyacrylamide gel and SDS-sucrose gradient after UV-irradiation and ribonuclease treatment indicate the formation of UV-induced linkages between RNA and NP protein.

[The immunological efficacy of one, two and three inoculations against diphtheria in adults]. / Immunologicheskaia éffektivnost' odnoi, dvukh i trekh privitok protiv difterii u vzroslykh.

The outbreak of diphtheria in the Republic of Belarus developed in the presence of a sharp deficiency of immunity among the population aged 35 years and over. In connection with a higher initial immunity level resulting from vaccination made in one injection the minimum antibody level (> or = 0.01 I.U./ml) was found in 79.7% of the examinees among the population under 35 years. For the age group of 35-60 years vaccination in one and two injections proved to be insufficiently effective (the minimum protective antibody titer was found, respectively, in 64.3% and 63.3% of the vaccinees). To achieve the full protection of this group of the population, vaccination in three injections was necessary; after that the minimum protective antibody titer was found in 90.7%, the protective antibody titer (0.1 I.U./ml) was found in 53.5% and the highly protective antibody titer (1.0 I.U./ml) was found in 11.6% of the examinees. The low level of highly protected persons among vaccinees receiving three injections was due to a low dose of diphtheria toxoid (2 Lf) in adsorbed DT-m vaccine with reduced antigen content.