Studies with the monkey-intra-nuclear-inclusion-agent (MINIA) and foamy-agent derived from spontaneously degenerating monkey kidney cultures. I. Isolation and tissue culture behavior of the agents and identification of MINIA as closely related to measles virus.

Abstract

1. MINIA and foamy-agent are both agents which have been unmasked by the routine procedure of culturing trypsinized monkey kidney tissue. MINIA occurred in 17%, foamy-agent in 57% of the 99 monkey kidney-cell batches prepared from individual and pooled rhesus and/or cynomolgus monkey kidneys over a period of 18 months. 2. MINIA produces identical cytopathic changes in monkey kidney cultures as does measles virus. The difficulties involved in differentiating the cytopathogenic effect of MINIA from the one produced by the foamyagent in unstained and early fixed and stained preparation of monkey kidney tissue are stressed since a superficial similarity exists in the cytopathic capacity of the foamy-agent and the degenerative effects produced by MINIA and measles virus. 3. Twelve strains of MINIA and 10 strains of foamy-agent recovered from spontaneously degenerating monkey kidney cultures were isolated in human kidney, human amniotic membrane and rabbit kidney cultures. It was found that MINIA could be propagated in HAM but not in rabbit kidney, as was true for human measles virus strains, whereas serial propagation of foamy-agent was possible in the latter but not in HAM. 4. The tissue culture behavior of 8 MINIA strains and 8 foamy-agent strains was investigated. All MINIA strains were found to be indistinguishable between their 1st and 25th HAM passage with respect to their cytopathic capacity and infectivity and identical with the tissue culture behavior of human measles virus. All foamy-agent strains studied were similar in their behavior and distinct from the cytopathic properties of MINIA and measles virus. 5. The difference in tissue response of HAM and rabbit kidney tissue to infection with MINIA and foamy-agent as well as cross-neutralization and cross-complement fixation technic were utilized for the identification of the agents. 6. The immunological properties of 8 MINIA strains investigated were indistinguishable and identical with those of human measles virus. All foamy-agent strains studied were immunologically related to each other and distinct from MINIA and measles virus.