Comparison between the binding site of streptococcal monoclonal antibody 10F5 and IgG2 subtype controls in the heart of the Lewis rat

Access to thesis permanently restricted to Ball State community only.Autoantibodies generated against M proteins can cause post-streptococcal disorders such as Rheumatic Fever. A severe complication of rheumatic fever is rheumatic heart disease which may involve both cardiomyopathy and valvulitis. Rheumatic fever has been associated with the class I M protein epitope of Group A streptococcus (GAS). This epitope can be recognized by monoclonal antibodies (mAbs) 10B6 and 10F5. Previously, we demonstrated binding of streptococcal mAb10F5 in the heart tissue (apex, atria, and valves) of Lewis rats as compared to anti-myosin binding. To determine if mAb10F5 binding in the heart is due to virulence of the antibody or antibody subtype, rats were injected with control IgG2 antibodies and euthanized after 24, 48, or 72 hrs. Hearts were harvested and immunofluorescence was used to analyze the hearts. The immunofluorescence intensities for IgG2b were compared to mAb10F5 using previously acquired data. Control IgG2b rats showed significantly less immunofluorescence intensities in the heart regions than mAb10F5 injected rats at the 48 and 72 hr time points. These findings reaffirm mAb10F5 as an anti-cardiac antibody thatbinds heart tissue due its own virulence. To differentiate between the two IgG subtypes, binding intensities of IgG2a were compared to the binding intensities of IgG2b. The binding intensities of IgG2a increased with time. This finding was supported by previous work in our laboratory suggesting IgG2a remained in the bloodstream longer than the IgG2b.Department of Physiology and Health ScienceThesis (M.S.