UK researchers are set to purposely re-infect a cohort of recovered COVID-19 patients in order to study how the immune system responds to a second encounter with SARS-CoV-2. This human challenge trial expands on an ongoing study deliberately infecting healthy subjects to test vaccine efficacy.
For much of 2020 researchers around the world debated whether or not deliberately infecting healthy young adults with SARS-CoV-2 was a useful or ethical way to study the virus. Late last year a large partnership between the UK government and several research groups agreed to commence these studies in early 2021.
The first phase began a couple of months ago, exposing a small group of young and healthy volunteers to the virus. This part of the study is homing in on the lowest dose of virus that consistently leads to the development of COVID-19. Once that has been determined the research will move onto broader experiments, including vaccine efficacy studies.
This new trial, led by researchers from the University of Oxford, is exploring a new question. How does the immune system respond when it encounters SARS-CoV-2 a second time?
The research spans two phases. The first phase is similar to the current phase of the other ongoing human challenge trial. A small cohort of young subjects who have previously recovered from COVID-19 will be recruited. In a custom-built quarantine facility they will be exposed to low doses of the virus in order to find the minimum dose that leads to viral replication regardless of symptoms.
The second phase will then recruit up to 64 young subjects also previously infected with the virus. They will be exposed to the minimum viral dose established in the first phase and then comprehensively monitored for at least 17 days.
“In phase two, we will explore two different things,” explains Helen McShane, chief investigator on the new trial. “First, we will define very carefully the baseline immune response in the volunteers, before we infect them. We will then infect them with the dose of virus chosen from the first study and measure how much virus we can detect after infection. We will then be able to understand what kind of immune responses protect against re-infection. Second, we will measure the immune response at several time points after infection so we can understand what immune response is generated by the virus.”
Chris Chiu, a researcher from Imperial College London working on the previously announced human challenge trial, says this new study, in conjunction with his work investigating preliminary infections, will offer valuable data.
“In particular, we will define how re-infection differs from a first infection with this virus, which may have important implications for how the pandemic is managed going forward as more people develop immunity,” says Chiu. “Furthermore, validating the immune markers that are associated with protection (which is one of the main aims of this program) is critically important for vaccine development and public health planning.”
Results from these human challenge trials are not likely to come until later in 2021. Last month the very first patients to take part in the experiment were safely released from quarantine.
Source: University of Oxford
