Researchers have created what they say is a "one-stop shop" for diagnosing infections - a test that can determine an individual's complete viral history just by scanning a single drop of blood.
The test, called VirScan, was created by Stephen Elledge and colleagues from the Howard Hughes Medical Institute (HHMI).
Next, the team introduced the DNA sections to bacteriophages - viruses that invade bacterial cells and infect them. Each bacteriophage molded with a peptide, with the peptide displayed on the bacteriophage's surface.
Together, the bacteriophages show all protein sequences present in the more than 1,000 strains of human viruses currently known.
Explaining how VirScan identifies viruses in blood samples, the
researchers note that antiviral antibodies present in the blood
recognize unique characteristics known as epitopes, which are found in
peptides on the surface of each bacteriophage. When the bacteriophages
are combined with a blood sample, antibodies in the blood identify and
bind to these epitopes.
The researchers then collect these antibodies and dispose of everything except the bacteriophages they are attached to.
By conducting DNA sequencing on these bacteriophages, the team
is able to identify the peptides that the antibodies clung to, revealing
which viruses an individual's immune system has come across previously,
whether through infection or vaccination.
It is likely to take around 2-3 days for VirScan to analyze 100 blood
samples, according to Elledge, though he is confident that this
processing time can be increased the more the test is developed. It
would cost around $25 to analyze one blood sample.
The team found that each individual included in the study had an average
of 10 different viruses, with people in South Africa, Peru and Thailand
possessing antibodies against more viruses than those in the US.
In addition, they found that adults possessed antibodies against more
viruses than children, and individuals with HIV had antibodies to more
viruses than those without HIV.
Perhaps the most surprising finding, however, was that antibody
responses against certain viruses were found to be similar in each
individual; different people's antibodies recognized exactly the same
amino acids present in the peptides of specific viruses.
The researchers are confident that VirScan could be an effective
alternative to existing viral testing methods, which test for specific
viruses one by one.
As the test can determine an individual's viral history, the team
believes it offers the potential to uncover factors affecting health
that may have been overlooked. The test also provides the opportunity to
assess and compare viral infections in large populations, and it may
even have implications for vaccine design.
Their study, the researchers say, has helped them improve the accuracy
of VirScan, and they hope it will improve further with more research.
The approach used to create VirScan could also be applied to identify
other antibodies, the team notes, such as those involved in autoimmune
diseases, in which the immune system attacks the body's healthy tissues.
Test showed high sensitivity and specificity
The researchers tested VirScan on the blood samples of 569 people from
the US, South Africa, Thailand and Peru, all of whom were known to have
been infected with certain viruses, including human immunodeficiency
virus (HIV) and hepatitis C.
Overall, VirScan analyzed around 100 million possible interactions
between antibodies and epitopes from the blood samples, with the test
producing very accurate results, according to the team. Elledge says:
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