Intrauterine Infection of the Rhesus Monkey with Mumps Virns: Abbreviated Viral Replication in the Immature Fetus as an Explanation for Split Immunologic Recognition After Birth

Abstract

Experimental, intravenous mumps-virus infection of the pregnant Rhesus monkey during the first third of gestation is characterized by the replication of virus in fetal and placental tissues for only one week. The most likely explanation for the disappearance of virus after this brief period is the transplacental distribution of maternal 7S neutralizing antibody to the infected fetal tissues. Pregnant monkeys developed both delayed hypersensitivity and neutralizing antibody to mumps virus after experimental infection. Four infant monkeys, successful full-term progeny of gestational infection, demonstrated delayed hypersensitivity to mumps virus but no antibody. Subsequent skin testing of these infants at a time when passively acquired maternal antibody had disappeared evoked either a low level of antibody or a transient titer in some monkeys. The split immunologic recognition of intrauterine mumps-virus infection by the infant monkey (i.e., delayed hypersensitivity without neutralizing antibody) represents the ontogenetic expression of the phylogenetic development of the immune response. This may occur because the immunologically immature monkey fetus is exposed to the antigen of mumps virus too briefly and subsequently responds with only cellular immunity, the primitive response of sophisticated species and the only response of primitive species.