Does Streptococcus pneumoniae use antigenic variation?
Antigenic Variation in Streptococcus pneumoniae PspC Promotes Immune Escape in the Presence of Variant-Specific Immunity.
Does malaria have antigenic variation?
An antigen on the surface of erythrocytes infected with mature asexual malaria parasites has been shown to undergo antigenic variation in two malaria species. The fundamental reasons for expression of these highly immunogenic antigens on the erythrocyte membrane remain obscure.
What causes antigenic variation of the malaria parasite?
In the human malaria parasite Plasmodium falciparum, this involves transcriptional switching among members of the var gene family, causing parasites with different antigenic and phenotypic characteristics to appear at different times within a population.
What is an example of antigenic variation?
Examples of random antigenic variation are those that occur in viruses such as the influenza virus and the human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS). The major antigenic components of these viruses are glycoproteins that make up their viral coat.
What benefits are there in variation for the microorganism?
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.
What is the difference between antigenic drift and antigenic shift?
Antigenic drift involves the accumulation of a series of minor genetic mutations. Antigenic shift involves “mixing” of genes from influenza viruses from different species. Pigs, birds, and humans.
What is malaria parasite antigen?
Plasmodium parasites express antigens at the surface of iRBC (61). These antigens are mainly encoded by multigene families such as the var (62), stevor (63), and rifins gene families (64, 65) for P. falciparum or the pir gene family for P. vivax, P. knowlesi, and the rodent malaria species (66).
What is a polymorphic antigen?
Third, the genes encoding blood group antigens are polymorphic so that some individuals of a species possess one form of the antigen and others another. This characteristic is the necessary condition for elicitation of immune response against the antigen which is commonly of the allogeneic type.
What is meant by antigenic shift?
Another type of change is called “antigenic shift.” Shift is an abrupt, major change in a flu A virus, resulting in new HA and/or new HA and NA proteins in flu viruses that infect humans. Antigenic shift can result in a new flu A subtype.
What causes an antigen to change?
Antigenic variation can occur by altering a variety of surface molecules including proteins and carbohydrates. Antigenic variation can result from gene conversion, site-specific DNA inversions, hypermutation, or recombination of sequence cassettes.
What causes variation in bacteria?
Any change in the genotype of a bacterium or its phenotype is known as variation. Genotypic variation can occur as a result of changes in the genes by way of mutation, loss or acquisition of new genetic elements. These variations are heritable.
How does antigenic variation evade the immune system?
Antigenic variation is a common mechanism of immune evasion in diverse pathogens. In a typical example, a pathogen with a given antigenic composition infects a population of hosts that respond by developing adaptive immune responses (antibodies and/or T cells).