Systemic and ocular antibody responses to inactivated acute hemorrhagic conjunctivitis (AHC) virus; enterovirus 70 (EV70)

Abstract

Purpose: Evaluate the immune response in rabbits injected with EV70, the agent of acute hemorrhagic conjunctivitis (AHC) and AHC associated neuropathy. Methods: Rabbits were injected intramuscularly with uv-light inactivated EV70 isolate J670/71. Neutralizing activity against EV70 was quantified in serum and tear samples and the immunoglobulin (Ig) classes of the neutralizing activity in serum identified by sucrose gradient ultra-centrifugation. Adjuvant muramyl dipeptide (MDP) was applied topically to assess the role of ocular inflammation on levels of neutralizing antibody, proteins and Ig in tears. The protective effects of human and rabbit sera and interferon-a (IFN-a) against EV70 were compared in human conjunctival and lens cells. Results: Sera collected at 6 and 13 d contained 19S IgM anti-EV70 neutralizing antibody, while serum collected 21 d post injection contained 19S IgM and 7S IgG anti-EV70 neutralizing antibody. Low titers of anti-EV70 activity (=30 U/ml) were detected in tears of seropositive rabbits. MDPinduction of conjunctivitis in seropositive rabbits increased tear IgG concentration (3-fold) and anti-EV70 neutralizing antibody titers (=10-fold). The protective effect of the rabbit and human sera against EV70 infection in conjunctival, but not lens epithelial cells, was enhanced by the addition of IFN-a. Conclusions: Immunization with uv-light inactivated EV70 elicits a classical humoral immune response in rabbits. The protective activity of serum in EV70- infected human conjunctival cells, but not lens cells, was increased by IFN-a. Adjuvant MDPinduced conjunctivitis, increased bloodconjunctival barrier (BCB) permeability and anti-EV70 neutralizing activity in tear of seropositive rabbits. The results suggest immunization with inactivated EV70 could provide systemic as well as ocular protection during natural EV70 infection.