Computational Studies on the Truncation of N-terminal Fragment of OspA Antigen of Borrelia burgdorferi: Towards Designing a Second- Generation Vaccine Against Lyme Disease

Lyme disease is caused by the spirochete Borrelia burgdorferi which enters into the skin by feeding ticks, mainly Ixodes species. Spread of the pathogen into the blood results in various symptoms. Because some individuals do not show any symptom following the infection, it is very difficult to diagnose the infection caused by this spirochete. When a proper treatment is not provided, this infection subsequently evolves to severe neurologic, joint, skin and cardiac abnormalities. Outer surface protein A (OspA) from B. burgdorferi has been the considered for the development of vaccine against Lyme disease. Even though the native form of OspA antigen is an active vaccine, some side effects are associated with it. For instance musculoskeletal arthritis in humans and severe, destructive osteoarthropathy in hamsters are the major sides effects detected in vaccinated animals. C-terminal region of OspA antigen has been suggested to be used alone as a second generation vaccine because all anti-OspA antibodies responsible for blocking Borrelia bind to Cterminal region only. In the present study an attempt is made to truncate N-terminal region of OspA antigen followed by modeling the interaction between truncated homology modelled antigen with native antibody using in silico approaches. The 3D models of full length OspA antigen as well as of all its truncated forms have been predicted through homology modeling approach. Docking of homology remodelled structure onto the native antibody (1FJ1_AB) was successful. MD simulation for 10ns was used for calculating the binding free energy of four selected antigen-antibody models under explicit solvent conditions.