Histological Distirbution Of Inlfuenza A Virus Sialoreceptors HA In A Range Tissues Of Dogs, Raccoon Dogs, Blue Foxes And Minks

Influenza A virus, a member of the genus Orthomyxovirus. Influenza A is one of the mostimportant infectious diseases of humans and is responsible for recurrent seasonal diseaseepidemics. A crucial feature in the ecology and epidemiology of in fluenza virus isinterspecies transmission. The emergence of new virus subtypes and their interspeciestransmission is of great concern. Measures to counteract their spread are vital for preventingin fluenza epidemics and pandemics. One of the basic mechanisms of interspeciestransmission of influenza virus is direct transfer of an essentially unaltered virus from onespecies to another, however, some factors restrict this transfer. In particular, the presence orabsence of host species–specific influenza virus binding receptors in the upper and lowerrespiratory tracts serves to prevent such cross-species or zoonotic transmission. Influenza Aviruses have been isolated from a variety of animals, including humans, pigs, horses, cats,dogs, raccoon dogs, blue foxes and minks, sea mammals, poultry, wild ducks, and othermigrating waterfowl. Among these animals, wild waterfowl serve as the reservoir from whichall influenza viruses are thought to have emerged. The causative viruses of the1957Asian and1968Hong Kong pandemics are in fact reassortants between human and avianinfluenzaviruses. Cell-surface-receptor binding by influenza viruses is a key determinant oftheir transmissibility, both from avian and animal species to humans as well as from human tohuman. HA binds specifically to cell surface sialic acid (SA) as a receptor when IVs infecttarget cells. For example, avian influenza virus (AIV) preferentially binds to sialic acidα2,3-galactose linkages (Sia α2,3-Gal), while human influenza virus (HIV) preferentiallyrecognizes sialic acid α2,6-galactose linkages (Sia α2,6-Gal). Consequently, a crucial hurdlethat IVs need to overcome when crossing a species barrier is the acquisition of the ability toutilize alternate host cell receptors (Ito,2000). To understand the mechanism of interspeciestransmission, it is important to clarify the histological distribution of IV sialoreceptors inanimals. At present, detailed information on the distribution of IV receptors in dogs, raccoon dogs, blue foxes and minks is lacking. Therefore, we have examined in detail the anatomicaldistribution of IV receptors in key organs of the four species, using lectin histochemistry. As aresult, both receptors were present in the relevant tissues from the four species. But there wasclear different presence of Sia α2-6Gal and Sia α2-3Gal receptors in a range of tissues fromdogs, raccoon dogs, blue foxes and minks. The major difference in the relative distribution ofSia α2-3Gal and Sia α2-6Gal receptors was along the respiratory tract. Both receptors weredominantly present in the dog respiratory tract and digestive tract. Sia α2-3Gal wassignificantly present in raccoon dogs respiratory tract. But SA α2,6Gal was significantlypresent in digestive tract. High levels of SA α2,3-Gal receptors but slightly SA α2,6-Gal isexpression in blue fox respiratory tract and digestive tract. And Sia α2-6Gal is the mainreceptor type in the mink respiratory tract. It implied that these organs may be potentialtargets for different IVs. The data provided the necessary basis for these animals to play apotential role in interspecies transmission, or to serve as an intermediate host for generation ofreassortant viruses with pandemic potential for human beings.