A new test developed by the Howard Hughes Medical Institute (HHMI) can test for both past and current infections by analyzing a single drop of patient blood. The researchers consider the method superior to existing techniques, which only search for a single virus at a time.
The method, know as VirScan (Systematic viral epitope scanning), provides an unbiased approach to patient testing. The technique works by screening blood samples for antibodies that fight against any of the 206 virus species that infect humans, and since the body continues to produces those antibodies for many years, it is able to detect both current and past infections.
To target virus cells in the bloodstream, antibodies search for features in peptides on the surface of the virus, known as epitopes. VirScan works by luring all present antibodies into binding with epitope-displaying peptides – something that requires a way of exposing blood samples to a huge number of known virus strains.
To that end, the team worked to synthesize in excess of 93,000 short pieces of viral protein-encoded DNA, and introduced them to bacteria-infection viruses known as bacteriophage. The technique results in a bacteriophage group that displays peptides of more than 1,000 known human virus strains.
Mixing the bacteriophage with the blood sample caused all present antibodies to bind with their target epitopes on the peptides. Scientists then stripped away everything but the antibody and bacteriophage pairs, sequencing the DNA of the latter to identify which viruses the patient's immune system had come into contact with.
The team estimates that it would take up to three days to process 100 samples using the method, but it's optimistic those numbers will improve with further development. The cost of an individual test is estimated at US$25.
So far, the team has used VirScan to screen the blood of 569 people in the US, South Africa, Peru and Thailand. The findings revealed that, on average, each patient had antibodies for around 10 different species of virus, with residents of the US having fewer than those in the other countries included in the study.
They also found that blood samples from patients infected with HIV showed a larger number of antibodies for different viruses than those without HIV.
Furthermore, the results revealed that different patients' immune systems had very similar responses to specific viruses, recognizing the same amino acids in viral peptides. It's thought that this could have significant implications on our understanding of how the immune system functions.
The findings of the study are detailed in the journal Science.
You can take a look at the video below to see VirScan lead developer Stephen Elledge discussing the new method.
Source: HHMI
