Transcription of HERV-W elements in response to virus infection. Relative levels of transcripts containing HERV-W gag sequence in uninfected human dermal fibroblasts (control) and in such cells 24 hours after infection with 0.5 MOI of influenza A virus (WSN, A). Frequency distributions of Tm categories of transcripts containing HERV-W gag elements in uninfected (control) and infected (WSN) human dermal fibroblasts (B). Relative levels of transcripts 3' of HERV-W proviral elements (U3+) (n = 7), pseudoelements (U3-) (n = 7) and solo LTRs (n = 4) in control and in influenza A/WSN/33 virus infected cells. Levels of all transcripts were normalized to expression-levels of their corresponding genes by pair-wise subtractions of the Ct-values obtained for assays in the flanking exons with those obtained from assays 3' of the intronic element (C). Statistical significance is indicated by *= p < 0.05, **= p < 0.01.