Antigenic drift and shift contribute to annual vaccinations to prevent influenza because they contribute to the virus changing and mutating and appearing different to our immune system. Antigenic shift has been studied most extensively in. This image is a derivative work of the following images. Antigenic shift is the molecular alteration of an antigen so that the human immune system can no. Not to be confused with antigenic drift, antigenic variation, or genetic drift. Much less frequent than antigenic drift occurring only in influenza a, it involves a profound change in the virus with. Antigenic shift is contrasted with antigenic drift, which is the natural mutation over time of known strains of influenza or other things, in a more general sense which may lead to a loss of immunity, or in vaccine mismatch. Antigenic shift, genetic alteration occurring in an infectious agent that causes a dramatic change in a protein called an antigen, which stimulates the production of antibodies by the immune systems of humans and other animals. Differences between antigenic shift and antigenic drift. In some cases, a 50% change occurs in the hemagglutinin structure.
Antigenic drift produces new virus strains that may not be recognized by the bodys immune system. Antigenic shift since infection with only a single virus is required, and the random mutations happen as the virus replicates in the infected persons cells. Whereas antigenic drift affects all strains of influenza, antigenic shift only affects influenza a, as it has. Antigenic shift and antigenic drift are two types of genetic variations that occur in influenza virus. Antigenic drift involves amino acid changes in antigenic regions of influenza proteins, facilitating escape from existing immunity. Antigenic shift pandemic potential equence of first viruses available april 1 35 cases to date. Each years flu vaccine contains three flu strains two a. The challenge of antigenic drift influenza continues to have a major worldwide impact, resulting in considerable human suffering and economic burden. H2 ha, the hong kong flu epidemicof 1968 was caused by viruses. Antigenic shift is a specific case of reassortment or viral shift that confers a phenotypic change.
Key difference antigenic drift vs antigenic shift the antigenic structures of the influenza virus change its shape to a new shape which cannot be recognized by the antibodies. When the viruses mutate, they shift to create a new subtype that is different from any seen in humans before. Antigenic shift, direct transfer and reassortment youtube. Antigenic shift, which is seen only with influenza a viruses, results from. Antigenic drift in the neuraminidase and hemagglutinin proteins correctly identify antigenic drift versus antigenic shift, as well as the factors or events that contribute to antigenic shift. Antigenic drift is a minor change in the virus but the slightest change or mutation makes our antibodies that our body created the year before make it look like a new virus. Predicting the mutating distribution at antigenic sites of. Niaid illustration of potential influenza genetic reassortment. One is a sequence of mutations that occur over time and causes a slow development of the virus. As i mentioned before, influenza a viruses can undergo antigenic drift as well as antigenic shift.
Antigenic shift is less frequent than antigenic drift. Antigenic drift definition of antigenic drift by medical. Shift can result in a new influenza a subtype in humans. Influenza viruses undergo antigenic evolution through antigenic drift and shift in their surface glycoproteins. The way by which i remember which one, antigenic drift or shift, causes which changes, is as follows. This shift typically occurs when a human flu virus crosses with a flu virus that usually affects animals such as birds or pigs. Although influenza viruses are changing by antigenic drift all the time, antigenic shift happens only occasionally. Seasonal and immediate mutations that enable influenza to escape immunity.
Antigenic drift vs antigenic shift technology networks. Mutations of the influenza virus lead to antigenic changes that cause recurrent epidemics and vaccine resistance. Explain how this activity models antigenic variation. This has forced frequent updates of vaccine antigens to ensure that the somewhat narrowly focused vaccineinduced immune responses defend against circulating strains. Pdf modeling influenza antigenic shift and drift with lego bricks. The mutational antigenic drift involves continuous genetic change of. Drift and shift influenza viruses can change in two different ways. Birds are the natural hosts for the flu, so they are infected first before infecting any other animals.
Pdf the concepts of antigenic shift and drift could be found in almost every microbiology and virology syllabus, usually taught in the context of. These are small changes in the virus that happen continually over time. Antigenic drift can have one simple effect on vaccination policy. This results in a new strain that requires yearly reformulation of the seasonal influenza vaccine. Influenza vaccine outmaneuvering antigenic shift and drift.
The major antigenic changes accorded with mutation occur in form of antigenic drift or antigenic shift. Antigenic drift occurs in ha and na, and is associated with seasonal epidemics. Describe how the activity could be modified to model antigenic shift, including the basis for your modification. Simulating antigenic drift and shift in influenza a core. As part of the hostpathogen arms race, viruses are continually evolving to evade the host immune response, be it from previous infection or. An example of a shift occurred in the spring of 2009, when a new h1n1 virus with a new combination of genes from american pigs, eurasian pigs, birds and humans emerged in people and quickly spread, causing a pandemic. Coronavirus and influenza a virus outline coronavirus background. If time allows, students can complete a form of the activity modified to demonstrate antigenic shift. Drift is a subtler process than shift and involves the accumulation of mutations within the antibodybinding sites in the hemagglutinin see figure, the. Antigenic drift is a kind of genetic variation in viruses, arising by the accumulation of mutations in the virus genes that code for virussurface proteins that host antibodies recognize. These mutations typically produce antigens to which only part of a population may be immune.
Working in small groups, students complete influenza antigenic drift activity 1. Antigenic drift important in 200708 season awisconsin67200 5like viruses 22%. One way influenza viruses change is called antigenic drift. Influenza b viruses on the other hands can only undergo antigenic drift same as any other virus can. It is a quick change of genes and is more complicated. Information from its description page there is shown below. The activity models the genetic processes underlying antigenic drift. For antigenic drift, i imagine slowly drifting in the sea, looking out, and sipping a cool drink. The processes of antigenic drift and shift have been briefly described earlier.
Antigenic drift is also known to occur in hiv human. Antigenic drift involves minor changes in the hemagglutinin ha and neuraminidase na, whereas antigenic shift involves major changes in these molecules resulting from replacement of. Drift mutations most commonly occur in the gene encoding the ha surface glycoprotein, which is the major target of neutralizing antibodies elicited as a result of vaccination andor natural infection. Antigenic shift is an abrupt, major change in an influenza a virus, resulting in new ha andor new ha and na proteins in influenza viruses that infect humans. The other type of change is a sudden change in the hemagglutinin andor the neuraminidase proteins. Antigenic drift in influenza virus h3 hemagglutinin from 1968 to 1980. Both surface antigens of the influenza a viruses undergo two types of variation. Antigenic shift is a more major change in the influenza virus. What is the role of antigenic shift in the pathogenesis of. Influenza has two ways to change one slow and one fast. Thus, infectious agents that have evolved through antigenic drift may cause potentially.
Antigenic shift definition of antigenic shift by medical. The process of antigenic shift by direct transfer and reassortment. Its that time of year again, when avoiding the flu is on everyones mind. Antigenic drift since random mutations occur more readily when only 1 virus is infecting a cell at a given time. Do your observations during the activity model antigenic drift. Antigenic shift and drift in influenza virus the flucausing virus, normally referred to as influenza virus undergoes the process of mutation. These are small changes or mutations in the genes of influenza. Antigenic shift is the process by which two or more different strains of a virus, or strains of two or. This results in a new strain of virus particles that is not effectively inhibited by. In a shift event, influenza genes between 2 strains are reassorted, presumably during coinfection of a. Influenza type a viruses go through two kinds of changes.
Neuraminidase nainhibiting antibody titers are a known correlate of immunity against influenza 8, 9, but antigenic drift of this antigen is not widely examined and the impact of an antigenic change on vaccine effectiveness has not been investigated. Antigenic drift of the pandemic 2009 ah1n1 influenza. Difference between antigenic drift and antigenic shift. This is really a special characteristic of influenza type a viruses. We analyzed the genomes of influenza ah3n2 and ah1n1pdm09 virus strains circulating in thailand between 2010 and 2014 and assessed how well the yearly vaccine strains recommended for the. The slow change is called drift the virus gradually accumulates individual mutations until its surface proteins are no longer recognized by our immune system the fast change is called shift different strains of influenza can exchange genetic material if they infect the same cell at the same time. Preventive measures would benefit greatly from the ability to predict the. Assessing antigenic drift of seasonal influenza ah3n2.