SHORT SEQUENCES DEFINE GENETIC LINEAGES - PHYLOGENETIC ANALYSIS OF GROUP-A ROTAVIRUSES BASED ON PARTIAL SEQUENCES OF GENOME SEGMENT-4 AND SEGMENT-9

Genetic diversity in strains of human group A rotaviruses was analysed by phylogenetic methods, The study material comprised 109 serotype G1 or G4 rotavirus samples isolated in Finland during 1986-1990, Parts o f the coding regions of rotaviral genome segments 4 and 9, which encod e proteins with serotype specificity, the spike protein VP4 (9 serotyp e) and the outer capsid protein VP7 (G serotype), respectively, were s equenced, As determined by analysis of segment 4 sequences all G1 stra ins and all except one G4 strain showed P[8] specificity, the one bein g of P[6] specificity, The G1P[8] strains could be further differentia ted into four groups based on segment 9 sequences, while G4P[8] strain s formed only one group, Type P[8] (G1P[8] and G4P[8]) strains formed two main groups based on segment 4 sequences, suggesting free segregat ion of segment 4 between these G strains, Most global G1, G4 and 9[8] strains in GenBank/EMBL originating from the 1970s to the present co-c lustered with these groups, suggesting that the groups exist as relati vely stable lineages. No linear accumulation of nucleotide substitutio ns was detected in strains of one serotype during the study period, Al so, the deduced amino acids of the antigenic regions A, B and 6 of VP7 were nearly conserved within the phylogenetic lineages, Interestingly , only short amino acid sequences were necessary to divide the e-types correctly into phylogenetic lineages, These amino acid signature moti fs were located in aa 29-68 of VP7 and aa 121-135 of VP4 of the G1 and 9[8] lineages, respectively.