Suckling Mouse Cataract Agent (SMCA) in Mice

Abstract

Summary Dams inoculated with SMCA as newborn mice subsequently confer complete protection against SMCA-induced cataract on their progeny. Several aspects of this “protection” were studied. The virus dose required to cause an infection resulting in protection of 100% of progeny was ≥104.0, similar to the dose required for maximal cataract induction. Foster nursing experiments in which litters were exchanged between SMCA-infected and normal dams revealed that complete protection against SMCA-induced cataract could be conferred by milk alone. The role of placentally acquired immunity was not clearly determined. A variety of mouse-lethal viruses were compared antigenically with SMCA by parallel titration in suckling mice born to SMCA-infected and normal dams. By this means the tick-borne virus isolate GT-48 was shown to be antigenically related to SMCA. This antigenic cross was shown to be reciprocal. No antigenic relationship was detected between SMCA and Powassan, Silverwater, Colorado tick fever, Sindbis, rabies, vesicular stomatitis, lymphocytic choriomeningitis, herpes simplex or pseudorabies viruses. As a further means of comparison with SMCA, the ability of several viruses to infect the suckling mouse eye following intracerebral inoculation was determined. All viruses studied, including GT-48, Powassan, Silverwater, Sindbis, rabies, vesicular stomatitis, Coxsackie B-5, herpes simplex and vaccinia virus, consistently infected the eye. In several cases titers of virus in the eye approximated those found in the brain. Hence, SMCA is not unique in its ability to replicate in the eye of the suckling mouse.