Antigenic Variation Sample Clauses
The Antigenic Variation clause defines the process by which an organism, typically a pathogen, alters its surface proteins to evade detection by the host's immune system. In practice, this clause applies to biological agreements or research protocols, specifying how changes in antigenic properties are identified, monitored, or reported during the course of a study. Its core function is to address the challenge of immune evasion, ensuring that parties are aware of and can respond to changes in pathogen behavior that may impact research outcomes or therapeutic effectiveness.
Antigenic Variation mirabilis encodes two nearly identical flagellins, ▇▇▇▇ and flaB. A third putative flagellin is encoded elsewhere on the chromosome. Despite the close proximity of the two loci, ▇▇▇▇ is transcribed monocistronically, and flaB transcript is scarce in wild-type cells. ▇▇▇▇ is the major flagellin, as ▇▇▇▇ mutants are non-motile and do not synthesize flagellin while flaB mutants exhibit wild-type motility. Mutants of ▇▇▇▇ frequently revert to motile cells with a flagellum that is antigenically distinct from wild-type (89). These mutants have hybrid FlaAB flagellin created by deletions in both loci that place the active ▇▇▇▇ promoter and the 5’coding region of ▇▇▇▇ with homologous and previously silent regions of flaB (90). Later, it was shown P. mirabilis populations are naturally heterogeneous in flagellar composition, with 1.0–1.5% of the population expressing hybrid flaAB transcript (91). Flagellin rearrangements confer advantages in different environments; bacteria with hybrid FlaAB flagella are more motile in environments with high salinity and extreme pH, while bacteria with ▇▇▇▇ flagella are more motile in low salt conditions (92). Recovery of swimmer and swarmer cells from the murine urinary tract illustrated different hybrid flagellins are formed during infection. All recovered FlaAB proteins were the result of splicing before the antigenically exposed domain of the flagellin molecule. This would result in exposure of different antigenic sites on the surface of the bacterium (90), and both flagellin proteins are capable of generating a humoral response (61). Overall, the ability of P. mirabilis to undergo flagellin rearrangements promotes survival in various environments and may help the bacteria evade the immune response during UTI.