Kida H, Ito T, Yasuda J, Shimizu Y, Itakura C, Shortridge K F, Kawaoka Y, Webster R G
Department of Veterinary Hygiene and Microbiology, School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
J Gen Virol. 1994 Sep;75 ( Pt 9):2183-8. doi: 10.1099/0022-1317-75-9-2183.
Pandemic strains of influenza A virus arise by genetic reassortment between avian and human viruses. Pigs have been suggested to generate such reassortants as intermediate hosts. In order for pigs to serve as 'mixing vessels' in genetic reassortment events, they must be susceptible to both human and avian influenza viruses. The ability of avian influenza viruses to replicate in pigs, however, has not been examined comprehensively. In this study, we assessed the growth potential of 42 strains of influenza virus in pigs. Of these, 38 were avian strains, including 27 with non-human-type haemagglutinins (HA; H4 to H13). At least one strain of each HA subtype replicated in the respiratory tract of pigs for 5 to 7 days to a level equivalent to that of swine and human viruses. These results indicate that avian influenza viruses with or without non-human-type HAs can be transmitted to pigs, thus raising the possibility of introduction of their genes into humans. Sera from pigs infected with avian viruses showed high titres of antibodies in ELISA and neutralization tests, but did not inhibit haemagglutination of homologous viruses, cautioning against the use of haemagglutination-inhibition tests to identify pigs infected with avian influenza viruses. Co-infection of pigs with a swine virus and with an avian virus unable to replicate in this animal generated reassortant viruses, whose polymerase and HA genes were entirely of avian origin, that could be passaged in pigs. This finding indicates that even avian viruses that do not replicate in pigs can contribute genes in the generation of reassortants.
甲型流感病毒的大流行毒株通过禽源病毒和人流感病毒之间的基因重配产生。有观点认为猪作为中间宿主产生了这种重配病毒。为了使猪在基因重配事件中充当“混合器”，它们必须对人流感病毒和禽流感病毒都易感。然而，禽流感病毒在猪体内复制的能力尚未得到全面研究。在本研究中，我们评估了42株流感病毒在猪体内的生长潜力。其中38株为禽源毒株，包括27株具有非人类型血凝素（HA；H4至H13）的毒株。每个HA亚型至少有一个毒株在猪的呼吸道中复制5至7天，达到与猪源和人源病毒相当的水平。这些结果表明，无论有无非人类型HA的禽流感病毒都可传播给猪，从而增加了其基因引入人类的可能性。感染禽流感病毒的猪的血清在ELISA和中和试验中显示出高滴度抗体，但不抑制同源病毒的血凝，这警示了不能用血凝抑制试验来鉴定感染禽流感病毒的猪。猪同时感染一种猪源病毒和一种不能在猪体内复制的禽流感病毒产生了重配病毒，其聚合酶和HA基因完全来源于禽类，且能在猪体内传代。这一发现表明，即使不能在猪体内复制的禽流感病毒也能在重配病毒的产生中贡献基因。
