[MECHANISMS OF ATTENUATION OF COLD-ADAPTED STRAIN A/KRASNO- DAR/101/35/59 (H2N2)].

AIM: Study of mechanisms of attenuation of cold-adapted (ca) influenza virus strain A/ Krasnodar/101/35/59 (H2N2), associated with disruption of NS1 protein functions. MATERIALS AND METHODS: Study of interferonogenic activity of ca strain A/Krasnodar/101/35/59 (H2N2), its parent variant A/Krasnodar/101/59 (H2N2), virulent strain A/WSN/33 (H1N1) and a number of single gene and multiple gene reassortants between these strains, obtained using reverse genetics, was carried out. Study of dynamics of IFNß gene expression was carried out by using a methodical approach of RT-PCR in real time mode. RESULTS: Inclusion of PB-1 gene of ca strain A/ Krasnodar/101/35/59 (H2N2) with reversion to wild type into genome composition of virulent strain A/WSN/33 (H1N1) does not result in a sharp change of interferonogenic activity of the reassortant. At the same time, similar inclusion of PB-1 gene of ca strain resulted in an incredible growth of interferonogenic activity of the reassortant. On the other hand, inclusion of NP-gene of wild type strain A/Krasnodar/101/59 (H2N2) into genome composition of the wild type strain A/WSN/33 did not differ by effect on interferonogenicity of the reassortant from inclusion of NP-gene of ca strain. CONCLUSION: Both constellations of genes of parent variants and mutations localized in these genes could affect formation of attenuation phenotype of reassortants. The data obtained allow to assume possible mechanisms of attenuation of ca strains, associated with disruption.of NS gene function.

Detection of measles virus genome in blood leucocytes of patients with certain autoimmune diseases.

RNA isolated from lymphocytes of peripheral blood was dot-hybridized to a hybrid plasmid containing specific sequences for measles virus nucleocapsid protein. Viral RNA was detected in the lymphocytes of 28 of 34 (82%) patients with systemic lupus erythematosus (SLE) and of 40 of 68 (59%) patients with chronic glomerulonephritis (CGN), and was not detected in 29 control patients.

Pathomorphologic characterization of CNS damage in monkeys infected with persistent variant of measles virus vaccine strain L-16.

The lesions of CNS were examined in monkeys infected intracerebrally (i.c.) with a variant of measles virus vaccine strain L-16 isolated after prolonged persistence in human cell culture NEr-2. The persisting virus variant appeared pathogenic for monkeys. The changes which had developed in their CNS within 30 to 60 days post-infection (p.i.) were alike to acute measles encephalitis which was evidenced by giant cell formation at the injection site. Twenty-two months p.i. the chronic character of lesions was evident from the appearance of foci of neuron destruction. Based on morphologic findings it was suggested that strain L-16-H has acquired some properties characteristic of nonattenuated virus.

Non-infectious morphologically altered nucleocapsids of measles virus from persistently infected cells.

Persistent measles virus infection of human HEp-2 or L-41 cells was accompanied by pronounced structural and functional changes of isolated intracellular viral nucleocapsids (NCs). The bulk of persistent NCs possessed altered conformation and a "string-of-beads" appearance, contained substantial amounts of subgenomic size RNAs, exhibited reduced transcriptase activity in vitro and lacked infectivity on transfection of susceptible cells. Immunogold staining revealed negligible binding of anti-P protein monoclonal antibodies to the "string-of-beads" type NCs, thus suggesting their non-functional state.

Measles virus persistent infection: modification of the virus nucleocapsid protein.

The synthesis of intracellular measles virus proteins in persistently infected human cell cultures was studied. The virus-induced proteins were analysed after radioimmunoprecipitation by one- and two-dimensional polyacrylamide gel electrophoresis. The measles virus-induced nucleoprotein (NP) synthesized in persistently infected cells had a reduced binding capacity with measles virus antibodies (human convalescent serum) compared to the NP protein induced by the virus used to initiate the infection. In contrast, monospecific rabbit serum prepared against the original virus NP, or monoclonal anti-NP antibodies, precipitated NP proteins from acutely and persistently infected cells with equal efficiency. When the NP in acutely or persistently infected cells was labelled with either 14C- or 3H-amino acids and subjected to two-dimensional gel analysis, significant charge differences were observed between the virus proteins. When measles virus-infected cells were examined for virus protein synthesis at 40 degrees C, although no change was found in acutely infected cells, NP was not detected in the persistent infection.