Effects of long-term acyclovir chemosuppression on serum IgG antibody to herpes simplex virus

Patients with severe or frequent recurrent genital herpes simplex virus (HSV) infection can be managed either by treating each recurrence with acyclovir or by suppressing recurrences with daily administration of the drug. To determine the effects of long-term acyclovir therapy on the immune response to HSV, we studied the change in IgG antibody concentration to HSV in 46 individuals with recurrent genital HSV-2 infection who received acyclovir for 1 year, Twenty-seven subjects received daily acyclovir chemosuppression, while 19 subjects received daily placebo (with acyclovir administered intermittently only during recurrences). Immunoglobulin G (IgG) antibody to HSV was determined before medication began, at completion of 1 year of therapy, and 22 weeks following the first untreated HSV recurrence. Daily acyclovir chemosuppression for 1 year reduced mean IgG antibody concentration by 10% from baseline values (P less than 0.01), whereas in patients receiving intermittent therapy no significant decline was observed. In both groups, however, the first untreated recurrence produced a rise in mean antibody concentrations. We conclude that prolonged daily acyclovir chemosuppression reduces humoral immunity to HSV, but antibody concentrations increase following the first untreated recurrence.