15 September 2008

New H5N1 virus Clade 2.3.4 (‘Fujian-like lineage’) avail= able for vaccine development

During the past week the World Health Organization (WHO) posted on their avian influenza “vaccines and an= tivirals” website that a new recombinan= t H5N1 avian influenza virus has been developed from a Clade<= /span> 2.3.4 isolate named A/duck/Laos/3295/2006. The WHO stated that it is available under a Materials Transfer Agreement (MTA). = This new recombinant vaccine virus was developed by a laboratory at the US Food = and Drug Administration (FDA/CBER).

Currently, the only US FDA-licensed H5N1 vaccine is base= d on a clade 1 virus isolate. Most human infections today are no longer due to clade 1 H5N1 viruses. Instead, mo= st human infections are due to Clade 2 viruses, ei= ther clade 2.1 (found primarily in Indonesia), clade 2.2 (“Qinghai lineage’), or clade 2.3.

Although some degree of cross-clade= protection may occur with certain H5N1 vaccines, the degree of protection m= ay not be as high as with the clade (or subclade) of H5N1 that is used to make a given vaccin= e. Thus, at this point in time it appears quite reasonable to develop H5N1 vaccines against all of the major clades (Clade 1 and 2) and subclades (e.g. Clade 2.1, 2.2., 2.3). In this regard the availability of= this recombinant clade 2.3.4 (‘Fujian-like lineage’) H5N1 vaccine virus represents progress.

The subclade 2.3.4 has also formerly been referred to as a ‘Fujian-like lineage’ H5N1 virus. The WHO reference for this nomenclature equivalence is listed on their avian influenza website in a document from August 2007 titled “Towards a unified nomenclature system for the highly pathogenic H5N1 avian influenza virus”. See www.who.int/csr/disease/avian_influenza /guidelines/nomenclature/en/ibndex.html

H5N1 highly pathogenic avian influenza infection of duck= s in Laos has continued, with the most recent report to posted on the OIE website (www.oie.int) on September 14, 2008. Two out= breaks were reported in ducklings in Nambok and Xay (the latter was traced to a duckling from the the Nambok outbreak). The ducklings in Nambok were in a small commercial = unit within a village with backyard poultry. The WHO website lists two humans wi= th laboratory-confirmed H5N1 virus infections in Laos, both of which occurred = in 2007. Worldwide, the WHO currently reports 387 human H5N1 virus infections, with 245 fatalities (63% case fatality rate).

Comments would be welcome by e-mail regarding the Materi= als Transfer Agreement (MTA) iss= ue(s) and whether a difference exists regarding MTA<= /st1:stockticker> requirements for H5N1 viruses of animal versus human sources.

Daniel R. Lucey, MD, MPH

EROne Institutes, Washington Hospital Center

Adjunct Professor of Microbiology and Immunology

Geo= rgetown University Medical<= /st1:PlaceName> Center=

Was= hington, D.C.

e-mail: DRL23@Georgetown.edu

website for this posting: www.BePast.= org