MOLECULAR CHARACTERIZATION OF HEMAGGLUTINATION DOMAINS ON THE FIBERS OF SUBGENUS-D ADENOVIRUSES

The adenovirus fiber mediates the agglutination of erythrocytes. Based on differential hemagglutinating properties, subgenus D adenoviruses can be subdivided into clusters DI, DII, and DIII. While subgenus DI a denoviruses agglutinate rat and human erythrocytes, DII adenoviruses s imply agglutinate rat erythrocytes and DIII adenoviruses display no or only weak rat erythrocyte agglutination. Amino acid sequence comparis ons revealed distinct domains on the fiber knob which could be involve d in hemagglutination. In order to localize and characterize the domai ns responsible for the interaction with rat and human erythrocytes, po tential hemagglutination domains of the adenovirus type 9 (Ad9) (subge nus DI) fiber knob were introduced into Ad17 (subgenus DII) and Ad28 ( subgenus DIII) fiber knobs by primer-directed mutagenesis. Furthermore , rat erythrocyte hemagglutination domains were also introduced into t he Ad3 (subgenus B) fiber knob, which only agglutinated monkey erythro cytes. Altogether, 27 chimeric and mutated fiber proteins were express ed in Escherichia coli and subsequently tested for hemagglutination ac tivity. The hemagglutination tests revealed that at least two domains can mediate the agglutination of rat erythrocytes. While one domain is located on the GH loop, the other domain extends from the C beta stra nd to the CD loop. The domain on the GH loop was partially conserved i n all adenoviruses showing an incomplete hemagglutination pattern with rat erythrocytes. The domains involved in the agglutination of human erythrocytes are located on the CD and HI loops of the subgenus DI fib er knob.