There are two different mechanisms by which influenza viruses might evolve: (1) Because the RNA genome of influenza viruses is segmented, new strains can suddenly be produced by reassortment, as happens, for example, during antigenic shift, creating new pandemic strains. (2) New viruses evolve ...
抗原性漂移(antigenic drift),主要是由于编码血凝素(HA)或神经氨酸酶(NA)蛋白基因的一系列点突变,导致了H或N蛋白分子上抗原位点氨基酸的替换与同一亚型内HA和NA基因发生点突变有关,属量变,可引起中、小型流行。二、抗原性转变 抗原性转变(antigenic shift),是指当细胞感染两种不同亚型的流感病毒时,病毒基因组的节...
二、抗原性变异(Antigenic variation)--重点 1.Antigenic drift Minor Change, Same Subtype Associated with Epidemics This is happening in the 2003-2004 season 2.Antigenic shift change in H, N, or both leading to new subtype [e.g., in1957type A (H2N2) appeared, replacing type A (H1N1)] ha...
Influenza流行性感冒 流行性感冒 “一种由不断变异的病毒导致的不变的疾病”“一种无国界的疾病”“一种传染性强，传播速度快的疾病”病原体 •分型•结构•抵抗力•命名•抗原变异 病原学 80-120nm 人流感病毒模式图 具有抗原性和亚型特异性 （核糖核蛋白）根据核蛋白质的抗原性分为3型甲（A）乙（...
In order to prevent human-infectingbird fluviruses from mutating into more dangerous subtypes,public healthauthorities try to limit the viral “reservoir” whereantigenic shiftmay take place by ordering the destruction of infectedpoultryflocks.
Less frequently, however, new and particularly virulent strains of influenza arise, which cause worldwide pandemics that are accompanied by greatly increased death tolls. These strains occur because of the phenomenon known asantigenic shift, in which humans are infected with avian influenza viruses or...
Antigenic shift refers to the emergence of a novel influenza virus in humans, due to direct introduction of an avian strain or to a new strain produced by recombination and reassortment of two different influenza viruses. Antigenic shift results in dramatic changes in the antigenic composition of ...
Figure 2. An example of influenza antigenic shift and drift Influenza type A viruses undergo two major kinds of changes. One is a series of mutations that occurs over time and causes a gradual evolution of the virus. This is called antigenic "drift." The other kind of change is an abrupt...
Furthermore, it also has high potential to cause pandemics, owing to the generation of novel subtypes, especially in animal reservoirs, following the gene reassortments between different influenza viruses (antigenic shift) (Medina and Garcia-Sastre 2011; Tscherne and Garcia-Sastre 2011). Such new ...
基因组自发的点突变聚集到一定程度时,即引起抗原性漂移(antigenicdrift)。这种在较小程度上发生的基因变异,每年或每几年均在甲型或乙型流感病毒中频繁发生。若两种不同亚型毒株感染细胞,使其基因组发生重组,则可引起抗原性转变(antigenic shift) ,导致新血清型的出现。 HA及NA的各自变异不断组合成新的变异株, 当...