HUMORAL AND CELLULAR IMMUNE-RESPONSE TO INFLUENZA-VIRUS VACCINATION IN AGED HUMANS

Aging is characterized by an increased susceptibility to infectious di seases; influenza virus infection, which is easily managed by an intac t immune system, represents a life-threatening disease in aged subject s. We studied 18 healthy aged subjects (>65 years of age), vaccinated yearly with conventional anti-influenza vaccine, and 9 healthy young v olunteers (mean age 26 years), without previous anti-influenza vaccina tion, who were vaccinated with the conventional trivalent 1990 anti-in fluenza preparation. Six out of the 18 aged individuals received a sec ond boost of the same vaccine about 4 months later In all subjects, we analyzed the humoral response to type A and B influenza viruses and t he influenza type A virus-specific CTL generation. Among the elderly p opulation with a single vaccination, 6 and 5 subjects seroconverted ag ainst type A and type B influenza virus respectively. Young subjects s eroconverted in 5 cases against type A, and in 5 cases against type B influenza virus. Seroconversion took place after the second vaccinatio n in only one subject, and the antibody production was type A specific . Influenza type A virus-specific CTL activity was significantly lower in aged subjects, compared with the values observed in the young volu nteers (p=0.017). The second vaccination partially restored this immun ological impairment. These data clearly demonstrate that the elderly d o not have the same ability as younger subjects to mount an antibody r esponse, and generate influenza type A virus-specific CTL after conven tional anti-influenza vaccination. Moreover, a double anti-influenza v accination generates CTL activity levels comparable to young subjects, although it does not seem to substantially modify the antibody produc tion.