Tick-borne encephalitis virus NS1 glycoprotein during acute and persistentinfection of cells

Tick-borne encephalitis virus (TBEV) was propagated in porcine embryo kidne y (PS) cells until 38 h whereas human kidney (RH) cells maintained the viru s persistence during at least 2 months. One of possible reasons of flavivir us chronic infection might be abnormal NS1 gene expression. Immunoblotting with monoclonal antibodies (MAbs) revealed the similarity of the intracellu lar and secreted NS1 nonstructural glycoprotein size and linear antigenic d eterminants in both the infected cell lines. However, according to the comp etitive binding of MAbs with the TBEV NS1 extracellular glycoprotein, its c ontiguous epitopes differed for acute or persistent infection. To map the T BEV NS1 glycoprotein antigenic determinants its recombinant analogues were used. All the studied MAbs could bind with the full-length NS1 recombinant protein. Deletion of the TBEV NS1 gene internal region resulted in defectiv e NS1d1 protein without the region between 269 and 333 a.a. Lack of NS1d1 b inding with 20B4 MAb and diminished binding with 22H8 and 17C3 MAbs permitt ed to map their antigenic determinants within or nearby deleted region, res pectively. Interaction of other MAbs with the NS1 and NS1d1 recombinant pro teins did not differ, suggesting that their epitopes were located in the re gion of N-terminal 268 a.a. or C-terminal 19 a.a. of the TBEV NS1 protein. The second NS1d2 truncated protein contained the first N-terminal 33 a.a. o f the TBEV NS1 protein and was able to bind with 29Gd9 MAb. Taken together the data stand for the differences in the N-terminal structure of the TBEV NS1 multimers secreted from the acute and persistent infected cells whereas the intracellular and secreted monomer processing was the same. Tl-le modi fied NS1 protein oligomers in the RH cellular lane might slow virus replica tion and could result in the TBEV persistence. (C) 2001 Elsevier Science B. V. All rights reserved.