Antigenic variation refers to the observation that different isolates of a single virus species may show variable cross-reactivity when tested with a standard serum.
What is the purpose of antigenic variation?
Antigenic variation not only enables the pathogen to avoid the immune response in its current host, but also allows re-infection of previously infected hosts. Immunity to re-infection is based on recognition of the antigens carried by the pathogen, which are remembered by the acquired immune response.
Is antigenic variation mutation?
Antigenic variation in microbes is created via two general types of mechanisms, genetic and epigenetic. Genetic events (mutation and recombination) change the DNA sequence of an antigen encoding gene or its regulatory elements, thereby altering either the level of expression or the amino acid sequence of its product.
Which are mechanisms of antigenic variation?
Antigens undergo variations in two ways: (1) through DNA alterations introduced by errors in DNA (or RNA) replication or repair, recombination between nonidentical genes, and reassortment of gene segments and (2) through programmed variations that are also called phase variations, multiphasic antigenic variations, true …
What is antigenic variation BBC Bitesize?
However some pathogens have the ability to alter their antigens. As a result, memory cells do not detect the altered antigens and are no longer effective against the pathogen. This is called antigenic variation.
What is the difference between antigenic and phase variation?
The key difference between antigenic and phase variation is that antigenic variation is the mechanism that refers to the expression of antigenically distinct proteins, carbohydrate or lipids on their surfaces while phase variation is the high frequency reversible on and off switching of phenotype expression.
What are antigenic properties?
The term “antigenic properties” is used to describe the antibody or immune response triggered by the antigens on a particular virus. “Antigenic characterization” refers to the analysis of a virus’ antigenic properties to help assess how related it is to another virus.
What is the difference between antigenic drift and antigenic shift?
Antigenic drift vs. shift. Antigenic drift creates influenza viruses with slightly modified antigens, while antigenic shift generates viruses with entirely new antigens (shown in red).
What is the process of antigenic drift?
Antigenic drift is a natural process whereby mutations (mistakes) occur during replication in the genes encoding antigens that produce alterations in the way they appear to the immune system (antigenic changes) (Figure 1).
What causes antigenic drift to occur in viral infections?
Infectious Diseases Antigenic drift: A subtle change in the surface glycoprotein (either hemagglutinin or neuraminidase) caused by a point mutation or deletion in the viral gene. This results in a new strain that requires yearly reformulation of the seasonal influenza vaccine.
Does gonorrhea have antigenic variation?
Neisseria gonorrhoeae, the bacterium responsible for the sexually transmitted infection gonorrhea, achieves this in part by changing the sequence of the major subunit of the type IV pilus in a process termed pilin antigenic variation (Av).
Which of the following pathogens undergoes antigenic variation to avoid immune defenses?
Which of the following pathogens undergoes antigenic variation to avoid immune defenses? Answer c.Plasmodium undergoes antigenic variation to avoid immune defenses.
Do Leukocidins destroy neutrophils?
~Leukocidins destroy neutrophils. ~Kinase destroys fibrin clots. ~Hyaluronidase breaks down substances between cells.
Does T cruzi undergo antigenic variation?
There is no evidence that T.cruzi adopts this type of antigenic variation. Instead, the entire T. cruzi population simultaneously exposes a variety of antigenic surface proteins, such as mucins, trans-sialidase, and MASPs, encoded by highly polymorphic multigene families (22, 80, 82, 129, 130).
What structures could be antigenic in a bacteria?
In the case of a bacterial antigen, we are referring to surface proteins, lipopolysaccharides, and peptidoglycans on the bacterial cell wall; these structures help bacteria invade other organisms by gaining access between epithelial cells.
What is antigenic variability A level biology?
Antigenic variation is one of the ways by which an infectious agent evades a host immune response. For example, a pathogenic bacterium could alter its surface proteins and carbohydrates so as to circumvent the immune response of the host.
What are antigens ks3?
The parts of a virus that make us sick are called antigens. Antigens trigger an immune response in the body. One of the key ways that our immune system fights the virus is by making something called antibodies. Antibodies are proteins made by our white blood cells, and they attack the virus.
How do lymphocytes work BBC Bitesize?
Lymphocytes are another type of white blood cell. They recognise proteins on the surface of pathogens called antigens . Lymphocytes detect that both the proteins and pathogens are foreign, not naturally occurring within your body and produce antibodies . This can take a few days, during which time you may feel ill.
What is the mechanism of phase variation?
Phase variation is the mechanism by which many of these different phenotypes are produced. This mutationally generated phenotype switch is reversible and inheritable.
How do phase variable genes undergo variation?
Genes can phase-vary through a number of genetic mechanisms [1] (Figure 1), including variation in the length of hypermutable simple DNA sequence repeat (SSR) tracts, recombination-mediated shuffling between expressed and silent loci, promoter inversions, and by epigenetic mechanisms [1,18].
What is antigenic variation in trypanosomes?
Trypanosome persistence in the mammal is due to antigenic variation, which involves changes in the identity of the variant surface glycoprotein (VSG) that forms a dense cell surface coat to shield invariant surface antigens from immune recognition.
What molecules are antigenic?
An antigen is a molecule that initiates the production of an antibody and causes an immune response. Antigens are typically proteins, peptides, or polysaccharides. Lipids and nucleic acids can combine with those molecules to form more complex antigens, like lipopolysaccharide, a potent bacterial toxin.
How would you define antigenicity and antigenic properties?
Antigenicity is the capacity of a chemical structure (either an antigen or hapten) to bind specifically with a group of certain products that have adaptive immunity: T cell receptors or antibodies (a.k.a. B cell receptors).
What is the meaning of antigenic determinant?
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The epitope is the specific piece of the antigen to which an antibody binds. The part of an antibody that binds to the epitope is called a paratope.
What is the best example of an antigenic shift?
An example of a pandemic resulting from antigenic shift was the 1918-19 outbreak of Spanish Influenza. This strain was originally the H1N1 avian flu, however antigenic shift allowed the viral infection to jump from pigs to humans, resulting in a large pandemic which killed over 40 million people.
What happens during antigenic shift?
Antigenic shift is the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains.
When does antigenic shift occur?
Antigenic shift occurs when a nonhuman influenza virus directly infects human hosts or when a new virus is generated by genetic reassortment between nonhuman and human influenza viruses. The segmented genome of influenza viruses facilitates reassortment events.
What enzyme is responsible for antigenic drift?
The hemagglutinin (H) and neuraminidase (N) undergo small changes in structure called antigenic drift on a yearly basis, which allows the virus to partially evade humans’ past immune response and cause yearly epidemics. Larger changes in the H and N, called antigenic shift, occur infrequently.
Is antigenic shift recombination?
Antigenic shift: A sudden shift in the antigenicity of a virus resulting from the recombination of the genomes of two viral strains. Antigenic shift is seen only with influenza A viruses.
What is an antigenic shift biology?
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.
Graduated from ENSAT (national agronomic school of Toulouse) in plant sciences in 2018, I pursued a CIFRE doctorate under contract with Sun’Agri and INRAE in Avignon between 2019 and 2022. My thesis aimed to study dynamic agrivoltaic systems, in my case in arboriculture. I love to write and share science related Stuff Here on my Website. I am currently continuing at Sun’Agri as an R&D engineer.