Isotype, during acute, early infection115,116. During the convalescent period at the end of 2? weeks of antibiotic treatment, 70?0 of patients have seroreactivity, still usually of the IgM isotype. However, after 4? weeks of untreated infection, virtually 100 of patients have IgG antibody responses. In patients with acute Lyme neuroborreliosis, especially those with meningitis, intrathecal antib