A macaque adherent cell line that expresses human CD4 is susceptible to SIV: utility for assessing neutralizing antibody.

A macaque CD4 + adherent cell line was generated by stable expression of the human CD4 gene in a rhesus macaque mammary tumor cell line, CMMT. The resulting cell line CMMT/CD4 expressed surface CD4 and was sensitive to infection by a wide range of isolates of simian immunodeficiency virus (SIV) of different subgroups, but was not susceptible to infection with HIV-1. The CMMT/CD4 cell line was used to develop a microassay for measurement of neutralizing antibody in plasma of SIV-infected or immunized animals. Single infected cells could be detected in a monolayer of CMMT/CD4 by immunoperoxidase and a 90% reduction in the number of positive cells was used as a measure of neutralizing activity of two-fold plasma dilutions. This assay had comparable sensitivity to methods based upon detecting a reduction in reverse transcriptase activity of SIV, reduction of viral antigen, or inhibition of cytopathic effect.