AGE-RELATED DEVELOPMENT OF HUMAN-MEMORY T-HELPER AND B-CELL RESPONSESTOWARD PARAINFLUENZA VIRUS TYPE-1

Human parainfluenza-1 virus (hPIV-1) infections are a major cause of r espiratory illness in young children. While children and adults are ea ch susceptible to hPIV-1 infection, the clinical symptoms in adults ar e mild and hospitalizations are rare. One explanation for the differen ces in disease severity is that immune memory responses are simply inf erior in children as compared to adults and cannot counter virus growt h. Alternatively, it has been suggested that immune (particularly T-he lper (T-H) cell) responses toward respiratory viruses are superior in children versus older individuals, and that these responses contribute to, rather than protect from, disease symptoms. As a test of these po ssibilities, we analyzed hPIV-1-specific T-helper (T-H) and B-cell mem ory responses among individuals of various ages, including children ho spitalized with hPIV-1-induced croup. Experiments revealed: (t) hPIV-1 -specific B-cell and class-II restricted T-H-cell proliferative respon ses were present in all tested adults. (2) T-H-cells responded to inte rnal viral proteins as well as to the external glycoprotein, hemagglut inin-neuraminidase. (3) Immune responses were highly cross-reactive wi th Sendai virus. (4) Memory B-cell and T-H-cell responses were extreme ly poor in young children, inclusive of children tested upon hospital entry for hPIV-1-induced croup, In total, results did not support the theory that naturally induced hPIV-specific memory responses cause res piratory illness. Rather, results showed a correlation between memory and a good clinical outcome and highlighted Sendai virus as a strong c andidate for an hPIV-1 vaccine. (C) 1994 Academic Press, Inc.