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. 2002 Dec;76(23):12112–12122. doi: 10.1128/JVI.76.23.12112-12122.2002

FIG. 3.

FIG. 3.

The ecotropic virus component of the RL-MuLV mixture is NB-tropic. Supernatants from RL-MuLV-infected SC-1 cells were titrated simultaneously in Fv1nn (NIH 3T3) and Fv1bb (BALB 3T3) cells (titration 1). The XC plaque assay was used for quantitation, and extra plates of BALB 3T3 and NIH 3T3 cells were infected at the titration end point (10−3) to reserve for harvesting. Titers of the virus on both NIH 3T3 and BALB 3T3 cells were approximately equal. To increase the virus titers, the plates reserved at titration end points were passaged once and their supernatants were collected. These supernatants were titrated again on NIH 3T3 and BALB 3T3 cells, and extra plates of BALB 3T3 and NIH 3T3 cells infected at the titration end point (10−3) were reserved for harvesting (titration 2). Cells at titration end points were passaged once, and their supernatants were collected and used for titration in NIH 3T3 and BALB 3T3 cells again, with extra plates at the titration end point (10−3) saved for harvesting (titration 3). Titers are expressed as PFU per 0.2 ml. N/B, number of PFU in NIH 3T3 cells/number of PFU in BALB 3T3 cells.