The invention provides methods and compositions for alleviating the symptoms of neuropathic conditions with a pharmaceutical composition including an effective amount of anti-glutamic acid decarboxylase antibodies. A purge gas system may include an input beam optics housing, a collection optics housing and a gas purge manifold. The additive containing a sulfur-solidifying agent that forms a solid sulfate upon the reaction with sulfur in the fuel due to combustion, is injected into the common rail from a tank due to a pump, and is supplied into the combustion chamber through the injector together with the fuel.