Long-term observation of neutralization antibody after enterovirus 70 infection.

There is the need for more information on the persistence of the immune response to enterovirus 70 (EV70) infection. In August 1984, an outbreak of acute hemorrhagic conjunctivitis occurred at a nursing home in Sapporo, Japan. During the subsequent 7 years, we have monitored the neutralization antibody of EV70 in 13 patients with acute hemorrhagic conjunctivitis and 15 persons with subclinical EV70 infection among the 108 persons in the nursing home. During the first one to two years, the neutralization antibody in 6 of the 28 subjects (21.4%) decreased to less than 1:8. Seven years later, the neutralization antibody had decreased to less than 1:8 in 92% of the subjects. There was an individual difference in the level of neutralization antibody titer against EV70. However, overall the antibody levels markedly decreased every year. It is important to remember that the neutralization antibody titer of EV70 decreases with the passage of time. Consequently, most of the patients who had acute hemorrhagic conjunctivitis will not have resistance against reinfection 7 years after the initial infection.