Before conducting experiments in the main chemistry laboratory, we first tested our ability to recover and detect viral nucleic acid
from glass slides using our clinical PCR assays and known positive samples in the controlled environment of a biosafety cabinet in our virology laboratory.
This extraction technology has successfully been evaluated to screen for viral nucleic acids
in routine blood donations.
Therefore, we investigated the suitability of this separation technology, which had successfully been evaluated for the extraction of viral nucleic acids
in routine blood donation screening, for serum and plasma samples (3,4).
Tissue specimens from only 3 of the 16 patients were available for testing, which was a major laboratory limitation in the investigation, particularly for detecting viral nucleic acid
by PCR assays.
Today, the main advantages of these assays are great sensitivity (measuring as few as 50 copies/mL of plasma), ease of use for quantification, and early detection of viral nucleic acid
in the peripheral blood before an antibody response develops, an application that has proven to be especially important in screening of human blood products.
With an oligonucleotide probe specific for USUV, ISH showed presence of viral nucleic acid
in the cytoplasm of neurons in a distribution pattern closely matching IHC (Figure 1, C and F).
Specific applications in which the use of ultrahigh-sensitivity immuno-PCR techniques have been proposed include prion protein detection, in which there is no nucleic acid associated with the infectious agent, and the detection of viral antigens in blood bank screening applications, in which there can be very little viral nucleic acid
present at certain stages of the infection.
Detection of viral nucleic acid
is not equivalent to isolating a virus.