Detection of T cell memory to measles virus in experimentally infected rhesus macaques by cytokine flow cytometry.

A low, average frequency (0.61%) of measles virus (MV)-specific CD4 and CD8+ T cells was detected in rhesus monkeys experimentally infected with or vaccinated against MV. Both IFN-gamma and TNF-alpha positive T cells were visualized by flow cytometry. However, the conditions of short-term culture and stimulation to detect MV-specific T cells required significant modifications from a previously established method that reliably detects T cells in rhesus monkeys persistently infected with SIV. Both whole viral antigen and short synthetic peptide pools were an adequate antigenic stimulus. MV-specific T cells were detectable up to 11 years after exposure to the virus, although we cannot rule out possible subclinical re-exposure of the monkeys to vaccine virus during this time. Thus, flow cytometric methods can permit mechanistic studies of antigen-specific memory T cell dynamics following an acute viral infection in a primate model.