Volume 80, no. 7, p. 3438-3444, 2006. Page 3440: Retrospectively, we found that the Friend virus (FV) stock that we used for our studies was contaminated with lactate dehydrogenase-elevating virus (LDV). LDV is a very rapidly replicating RNA virus of the Arterivirus family and is known as a strong inducer of type I interferon (IFN) responses (R. Evans and V. Riley, J. Gen. Virol. 3:449-452, 1968). New experiments revealed that the IFN-α and IFN-β plasma concentrations shown in Fig. 2 were induced by the contaminating LDV but not by FV. FV without LDV did not induce type I IFN responses in plasma that were measurable by ELISA. However, IFN-α mRNA expression could be detected in splenocytes of FV-infected mice at 72 h postinfection, which is in line with the spleen being the primary organ of FV replication. Thus, Fig. 2 should appear as shown below.
FIG. 2.
mRNA levels for IFN-α in splenocytes. (B10.A × A.BY)F1 mice were infected with FV, and splenocytes were isolated at the indicated time points postinfection. Levels of IFN-α transcripts were determined by quantitative real-time PCR. The primers used correspond to the regions of IFN-α genes that are conserved in all subtypes (G. Gautier, M. Humbert, F. Deauvieau, M. Scuiller, J. Hiscott, E. E. Bates, G. Trinchieri, C. Caux, P. Garrone, J. Exp. Med. 201:1435-1446, 2005; Table I). The housekeeping gene beta-actin was amplified from each sample to normalize the template concentration and was used as an internal standard. Each sample was run in duplicate. Three mice per group were analyzed. The means and standard deviations are shown by a bar.
The published findings from our studies with the knockout mice and the IFN therapy experiments were not affected by the LDV contamination.