BACKGROUND:Relapsing fever (RF) spirochetes are notable for multiphasic antigenic variation of polymorphic outer membrane lipoproteins. a phenomenon responsible for immune evasion. An additional role in tissue localization is suggested by the finding that isogenic serotypes 1 (Bt1) and 2 (Bt2) of the RF spirochete Borrelia turicatae. which differ only in the Vsp they express. https://www.chiggate.com/satisfyer-pro-penguin-next-generation-on-sale/