2024-05-21-世界卫生组织-Genetic_and_antigenic_characteristics_of_clade_2.3.4.4b_A_H5N1_viruses_identified_in_dairy_cattle_in_the_United_States_of_America_4页_253kb

Genetic and Antigenic Characteristics of Clade 2.3.4.4b A(H5N1) Viruses in US Dairy Cattle

• Background: Clade 2.3.4.4b A(H5N1) viruses, previously identified in birds, have spread to mammals, including US dairy cattle. Genetic analysis of 225 cattle virus sequences revealed high frequency of amino acid changes in the hemagglutinin (HA), with 100% of viruses showing changes at positions 104, 115, 127, 156, 195, 236, 272, 285, 320, 321, 336, 356, 407, 452, 494, 452, 511, 523, 528, and 531 relative to reference strains.

• Antigenic Findings: All cattle viruses were well recognized by ferret antisera against existing candidate vaccine viruses (CVVs) such as IDCDC-RG71A and IDCDC-RG78A. However, a specific change (A156T) in antigenic site B was detected in 4% of viruses, which may reduce reactivity to some CVVs but is inhibited by the IDCDC-RG80A CVV, containing the same change. Additional changes were rare and not widespread.

• Comparison to CVVs: The virus from a Texas dairy worker was closely related to circulating CVVs, with four major HA changes compared to IDCDC-RG71A and two compared to IDCDC-RG78A, all not in major epitopes. Antigenic tests showed good cross-reactivity with multiple CVVs.

• Implications: Based on current data, no new CVVs are recommended for pandemic preparedness. Clinical studies on vaccines derived from CVVs are ongoing to inform human vaccine use if needed due to public health risks.