ADJUVANT EFFECT OF LOW-DOSE INTERLEUKIN-2 ON ANTIBODY-RESPONSE TO INFLUENZA-VIRUS VACCINATION IN HEALTHY ELDERLY SUBJECTS

It is well known that immune efficiency is frequently deteriorated in elderly people. The age-diminished antibody response to T-cell dependent antigens, such as influenza virus antigens, may explain the low protection offered by influenza vaccination in the elderly population. To investigate the 'possibility of increasing the antibody response to influenza virus vaccinations, we have conducted a nursing home-based study on the efficacy of IL-2. Seventy-five institutionalized elderly subjects (82 +/- 8 years) were enrolled in the study in the course of winter season 1998-1992. Thirty-nine subjects were treated with three subcutaneous daily injections of interleukin-2 (IL-2, 1 x 10(6) I.U./day) before vaccination and their antibody response was compared to that of 36 aged people receiving the vaccine only. An increased antibody response against influenza virus was present in vaccine plus IL-2 treated subjects (P < 0.001) but not in subjects treated with vaccine only. The number of protected subjects 45 days after vaccination was increased only in the IL-2-treated group (P = 0.045). The low-dose of IL-2 administered and the short-term treatment allowed a good tolerance to the IL-2 injection. In conclusion, the low-dose IL-2 treatment represents an effective means of inducing antibody response to influenza virus antigens in elderly subjects without appreciable toxicity.