1989, "Heat Capacities and Volumes of Some Polybasic
Carboxylic Acids in Water at 298.
Compound 48/80 and other polybasic
compounds are shown to activate G proteins (20,21).
This evidence suggests that the polybasic
HA cleavage site was acquired progressively through multiple mutations within the avian species in a subclade of the A(H7N9) viruses.
hemagglutinin (HA) cleavage site sequence RNSPLRERRRKR*GLF indicated a highly pathogenic phenotype.
The HA cleavage site showed polybasic
properties RNSPLRERRRKR*GLFGAIA, confirming the high pathogenicity of the virus.
This process showed the polybasic
cleavage site PLRERRRKR/ GLF from multiple bird swab and tissue samples from each shed.
The amino acid sequence of the HA1/HA2-connecting peptide of HA is a major determinant of pathogenicity in terrestrial poultry, and the pathogenicity of highly pathogenic subtype H5N1 and H7N3 viruses is influenced by the presence of a polybasic
cleavage site in the connecting peptide (32).
The virus's hemagglutinin (HA) cleavage site had the polybasic
amino acid sequence PQRERRRKRGLF, which is characteristic of HPAIVs (22).
9 * PB, polybasic
protein; 008, A/duck/eastern China/008/2008(H5N5); 108, A/duck/eastern China/108/2008(H5N1); 031, A/duck/eastern China/031/2009(H5N5); 909, A/duck/eastern China/909/2009(H5N1); 013, A/duck/Yangzhou/013/2008(H6N5); PA, polymerase acidic protein; HA, hemagglutinin; NP, nucelocapsid protein; NA, neuraminidase; M, matrix protein; NS, nonstructural protein.
The respiratory tract of poultry and gastrointestinal tract of waterfowl are replication sites for AIVs, and poultry are incubators for the progression of low-pathogenicity avian influenza (LPAI) virus into highly pathogenic avian influenza (HPAI) virus (4-6), usually through the acquisition of polybasic
amino acids at the HA cleavage site.
We found that the H cleavage site of the selected influenza subtype H5N1 isolates (determined from the Veterinary Laboratory Agency) contained polybasic
amino acids, which are characteristic of HPAI A viruses (Table 2).
Because highly pathogenic influenza (H5N1) subtypes may kill embryonated eggs, use of viruses that are no longer pathogenic, such as H5 (which lacks the polybasic
cleavage site), to reduce the virulence of influenza (H5N1) vaccine strains so that these can be efficiently propagated in eggs for vaccine production is feasible (10).