An expansion ring for expanding the perimeter of a splice case end plate. At least one ground engaging wheel operatively attached to the frame for facilitating movement of the frame in a forward direction. In particular embodiments, the invention is directed to an isolated mutant pneumolysin protein, wherein the mutant PLY protein differs from the wild-type PLY protein of SEQ ID NO:1 presence of a mutation within the region of amino acids 144 to 161 of the wild type such that the toxicity of the mutant is reduced relative to that of the wild-type protein.