The Spanish influenza virus: Treats to the portrait after 100 years

The purpose of the study was to compare molecular characteristics of genes and proteins of pandemic influenza strains and find features of the 1918 Spanish influenza virus. Computer analysis has shown that the genes of the Spanish influenza virus in contrast to other pandemic strains contain optimal quantity of long complementary sequences that allow to obtain a supramolecular assembly of 8 virus RNA in according to a model ensuring selective packing of one copy of each virus RNA by the only possible scheme and high transmission to induce infection by single virions. Other pandemic strains contain redundant or insufficient quantity of complementary sequences that allow an assembly of its genome by means of some models including a stochastic one and occurrence of virions with incomplete genome, that is influenza virusts can exist primarily as a swarm of complementation-dependent semi-infectious virions. Analysis of an HA gene of the Spanish influenza virus found out exclusion from its translation code four triplets (CGG, CGA, CGC и CGU) coding arginine. This exclusion is observed in all the HlNl strains isolated during 100 years. Coding arginine in an HA gene of HlNl strains is provided by only triplets AGG and AGA. A NP gene of the Spanish influenza virus in contrast to other pandemics strains is avian-like and its NP protein is characterized by elevated quantity of arginine and decreased quantity of lysine that is considered as viral adaptation to avian body temperature. Prevalence of arginine provides more high positive charge for the Spanish influenza NP protein and its more powerful interaction with RNA and consequently more high thermal stability of the its RNP in comparison with the RNP of other pandemic strains. Potential consequence of existence of the avian-like NP in the Spanish influenza virus could be its high pathogenicity as infection fever creates optimal temperature for virus replication. These new data obtained by computer analysis of genomes in the Spanish influenza virus and other pandemic strains (altogether information about its proteins) can potentially be used to track pre-pandemic strains among circulating influenza A viruses and detect the formation of a possible trajectory of pandemic alert. © Saint Petersburg Pasteur Institute. All rights reserved