FIG. 3.

Limiting-dilution nested PCR analysis of splenocytes from MHV68.ORF73βla-infected mice during chronic infection. Single-copy sensitive limiting-dilution nested PCR analysis was performed on splenocytes harvested at 16, 28, 42, and 90 days postinoculation. Harvested cells were serially diluted 3-fold in a background of uninfected RAW264.7 murine macrophages, plated at 12 reactions per cell dilution, and then subjected to lysis followed by nested PCR specific for viral genome. The frequency of cells harboring viral DNA was determined at 63.2% (indicated by the horizontal line) using Poisson distribution (n = 3).