Effect of microbial immunomodulants on the course of LCMV infection in old mice with thymus involution.

Old mice with thymus involution were treated intraperitoneally with a live vaccine containing a mesogenic strain of attenuated Newcastle Disease Virus or with Mannozym (M, 1% zymosan suspension). One day after the treatments mice were infected with lymphocytic choriomeningitis virus (LCMV) intracerebrally. The fatal course of the consequent LCMV infection was stimulated by each of the pretreatments, indicating that the cellular immune response was stimulated. The results are compared with results of experiments carried out on suckling, young adult and old mice in similar experimental systems. The authors' previous publication suggesting that the direction and degree of the immunomodulant effect may be influenced by the actual age-dependent condition of the lymphoid system, have been confirmed.