2.2.4. Control viruses and plasmid DNA for the viral qPCR assays
Human adenovirus type 35 (HAdV35) and norovirus genogroup
II type 13 (NoV GGII.13) stocks were kindly donated by Dr. A. Allard
of the University of Umeå (Sweden) and were used as positive
process controls. On each sampling day, an extra sample was
collected and spiked with HAdV35 (105 viral particles/mL) as a
process control for flocculation, NA extraction and DNA quantification.
The NoV GGII.13 genome was also extracted from each
sample as a positive control for nucleic acid extraction and RNA
quantification (104 genome copies in each reaction of 5 mL).
Plasmid DNAwas used as a positive control and as a quantitative
standard. The hexon region (8961 bp) and the whole genome
(5130 bp) of HAdV41 and JCPyV Mad1, respectively, were cloned
into pBR322. To reduce the possibility of DNA contamination in the
laboratory, 10 mg of plasmid DNA was linearised with BamHI for
HAdV and NruI for JCPyV (Promega, Madison, WI) and the reaction
products were purified and quantified. The capsid protein region of
NoV GGII.13 cloned into the pTrueBlue®-Pvu II vector (kindly
donated by Dr. J. Vinje, CDC, Atlanta) was used as a qRT-PCR standard.
A total of 10 mg of this construct was linearised with XhoI
(Promega) to prevent contamination. Serial dilutions ranging from
100 to 105 molecules per 5 or 10 mL for RNA or DNA virus qPCR,
respectively, were performed with TE buffer. Standard dilutions
were distributed into tubes and stored at 80 C until use. Specific
primers and hydrolysis probes are described in Table 1. UltraPure™
DNase/RNase-Free distilledwaterwas used as a negative control for
the NA extraction and qPCR assays.