Antigenic variation is/are seen in-: (A) Treponema pallidum, (B) Neisseria, (C) Corynebacterium, (D) All
Answer is B. Ans. is 'b' i.e., Neisseria Antigenic variation It is the process by which an infectious oganism alters its surface proteins in order to evade a host immune response. . Antigenic variation not only enables immune evasion but also allows pathogens to cause reinfection as they are not recognised by the host's immune response . . Antigenic variation enables viruses to cross the species barrier,(eg. H5Nlvirus "jumping" from birds to then infect humans). . Antigenic variation in bacteria is best demonstrate by: species of the genus Neisseria ( most notably, Neisseria meningitidis and Neisseria gonorrhoeae, the gonococcus);Borrelia recurrentis; species of the genus Streptococcus and the Mycoplasma. . Antigenic variation in viruses is best demonstrated by : by HIV ( Human Immunodeficiency Virus); Influenza virus and Hepatitis virus, rhinoviruses and enteroviruses. . Antigenic variation in protozoa is best demonstrated by : species of the genus Plasmodium ( responsible for causing malaria) and the trypanosomes ( Trypanosoma cruzi which causes Chagas disease and T. bruzi gambiense and T. bruzi rhodesiense which both cause African sleeping sickness).