COVID-19 Vaccine: Universal Broad Spectrum Vaccine Approach Might Not Be Feasible As Study Shows Coronaviruses Do Not Readily Induce Cross-Protective Antibody Responses
Source: COVID-19 Vaccine May 19, 2020 4 years, 7 months, 4 days, 7 hours, 19 minutes ago
COVID-19 Vaccine: Researchers from University Of Hong Kong say that although individuals infected with either severe acute respiratory syndrome coronavirus (SARS-CoV) or SARS-CoV-2 produce antibodies that bind to the other coronavirus, the cross-reactive antibodies are not cross protective, at least in cell-culture experiments.
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The research has implications that most vaccine developers trying to develop broad spectrum vaccine that can also have efficacy against a brand range of coronaviruses might be pursuing a strategy that could be futile.
Also it remains unclear whether such antibodies offer cross protection in the human body or potentiate disease. The researchers suggest that more research is needed to identify parts of the virus that are critical for inducing a cross-protective immune response.
Co-senior study author Dr Chris Mok of the University of Hong Kong told Thailand Medical News, "Since coronavirus outbreaks are likely to continue to pose global health risks in the future, the possibility of developing a cross-protective vaccine against multiple coronaviruses has been considered. Our findings, albeit limited at present, would suggest that broadly cross-neutralizing antibodies to coronaviruses might not be commonly produced by the human immune repertoire. Moving forward, monoclonal antibody discovery and characterization will be crucial to the development of a SARS-CoV-2 vaccine in the short-term, as well as a cross-protective coronavirus vaccine in the long term."
Between 2002 to 2003, more than 8,000 people globally became ill with the severe acute respiratory syndrome (SARS), resulting in more than 700 deaths.
The coronavirus virus responsible for this outbreak, known as SARS-CoV, shares approximately 80% of its genomic nucleotide sequence identity with that of SARS-CoV-2, which causes the COVID-19 disease. The two coronaviruses also enter and infect cells the same way. During this process, the receptor-binding domain (RBD) of the spike (S) protein, which is located on the surface of the coronavirus, binds to a human cell receptor called angiotensin-converting enzyme 2, triggering viral fusion with the host cell.
Previous studies have shown that protective antibodies against SARS-CoV bind to the RBD. But relatively little is known about the antibody response induced by SARS-CoV-2 infection. It is also unclear how infection with SARS-CoV influences the antibody response against SARS-CoV-2, and vice versa. Gaining insight into these questions could guide the development of an effective vaccine for SARS-CoV-2 and shed light on whether such a vaccine would also cross-protect against similar viruses.
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Dr Malik Peiris also from the University of Hong Kong and a member of the research team said, "There are related viruses still circulating in bats, and it is unclear
whether any of these may also threaten human health in future," "As such, whether infection by one of these viruses cross-protects against another is an important question."
To further procure more relevant data, the researchers analyzed blood samples collected from 15 SARS-CoV-2-infected patients in Hong Kong between 2 and 22 days after the onset of symptoms. Compared to blood samples from healthy controls, the five samples collected from patients 11 days after symptom onset or later had antibodies capable of binding to the RBD and other parts of the S protein on both SARS-CoV-2 and SARS-CoV.
The study team also analyzed blood samples collected from seven patients 3 to 6 months after infection with SARS-CoV. Compared to blood samples from healthy controls, those collected from patients had antibodies capable of binding to the RBD and other parts of the S protein on SARS-CoV-2. Taken together, these findings show that infection with one coronavirus induces the production of antibodies that can bind to both RBD and non-RBD regions of the S protein on the other coronavirus.
Utilizing cell-culture experiments, the team next tested whether infection with SARS-CoV-2 induces SARS-CoV-2-specific neutralizing antibodies, which protect host cells by preventing the virus from interacting with them. All 11 blood samples collected 12 days or later after the onset of symptoms had neutralizing antibodies against SARS-CoV-2.
However only one blood sample had cross-neutralizing antibodies against SARS-CoV, and this response was very weak. Similarly, five blood samples from patients infected with SARS-CoV had neutralizing antibodies against this virus, but none could cross-neutralize SARS-CoV-2. Additional experiments in mice supported the findings from patients.
At the moment, the clinical implications remain unclear. One possibility is that cross-reactive, non-neutralizing antibodies offer cross protection against viruses in the body, even though they don't protect cultured cells. This phenomenon has been observed for other types of viruses.
On the other hand, non-neutralizing antibodies against SARS-CoV-2 could enhance viral entry into cells and viral replication through a process called antibody-dependent enhancement of infection, which has been previously reported for SARS-CoV.
Co-senior study author Dr Ian Wilson from the Scripps Research Institute commented, "Whether antibody-dependent enhancement plays a role in SARS-CoV-2 infection needs to be carefully examined in the future. Addressing this question will be critical for developing a safe and effective universal coronavirus vaccine."
The research is published in the journal
Cell Reports.
https://www.cell.com/cell-reports/pdf/S2211-1247(20)30702-6.pdf?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2211124720307026%3Fshowall%3Dtrue
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