How influenza a causes ‘‘epidemics and pandemics’’ among the population: novel targets for anti-influenza molecules

Influenza or flu is a contagious respiratory disease of birds, human& many other mammals and it is caused by influenza viruses. The flu viruses are of three types A, B and C but only type A is mainly found to cause severe epidemics and pandemics among human population. This is because the influenza A virus is serologically having several different subtypes based on combination between their surface antigens known as Hemagglutinin (HA) and Neuraminidase (NA), which are 18 and 11 in number respectively [1,2]. This serological variation is thought to enable the virus to undergo a constant antigenic variation to evade host immune system by using different mechanisms and as a result new strains with partially or completely changed surface antigens will develop which cannot be recognized by the pre-existing immunity against the older strains, either leading to a seasonal epidemic or spread more extensively causing a rare pandemic [1]. Different kind of drugs and compounds with antiviral activities have been described at different stages and targets of viral life cycle, especially at the attachment and entry targets (e.g. HA, NA, and M2 inhibitors). This is; however, the emergence of drug resistance has been reported due to continuous antigenic variations at those targets. Therefore, other alternative targets of viral cycle are thought to be essential to control the viral replication and pandemic infections, and more recently nuclear export of NP is found to be an effective and alternative target for development of anti-influenza a compounds. Several compounds are described to be effective against this target and most common examples are leptomycin B, Verdinixor, RK424, DP2392-E10...etc.