As scientists around the world race to develop a vaccine against COVID-19, one hurdle that stands in their way is the possibility that antibodies against SARS-CoV-2 end up worsening the disease instead of eradicating its target. Called antibody-dependent enhancement (ADE), this phenomenon has been observed for other viral diseases such as dengue.
The issue with SARS-CoV-2 is that its similarity to other human coronaviruses circulating in the population means that pre-existing antibodies to these ‘common cold’ viruses could drive ADE. For this reason, ADE has been hypothesized as one possible explanation of why some COVID-19 cases are more severe than others.
“If and when the SARS-CoV-2 vaccines are licensed, these may initially protect against SARS-CoV-2 infections, but we don’t know if they may predispose people to more severe infections via ADE with any of the seasonal coronavirus infections,“ said study co-author Hong Kai Lee of A*STAR’s Singapore Immunology Network (SIgN).
Driven by this concern, Lee and a team of international collaborators compared the seasonal peaks of common human coronaviruses with that of influenza A and B, using data from diagnostic laboratories from various countries. “Setting influenza incidence as the baseline for comparison will help guide vaccination strategies once the yearly mutation rates of the novel coronavirus are established,” he said.
The study found that in temperate countries such as Canada or the UK, coronavirus infections typically peak either slightly before or simultaneously with the influenza A and B peaks. In contrast, there was no consistent relationship between the influenza A, influenza B and coronavirus peaks in Singapore.
“If there is a predictable seasonality for coronaviruses which differs from the SARS-CoV-2 seasonality, you could try to vaccinate against SARS-CoV-2 when seasonal coronaviruses are not circulating,” Lee explained. In the case of Singapore, where coronaviruses are found to be circulating all year round, the vaccines also need to be available all year round. Policymakers thus may consider the significant challenges for future SARS-CoV-2 vaccine procurement, stock maintenance and administration, he added.
“Ideally, we want to first develop accurate and reliable serology assays for each of the four seasonal coronaviruses, OC43, 229E, NL63 and HKU1,” Lee said. Patients with COVID-19 can then be screened to determine if there is any correlation between antibodies against other coronaviruses and disease severity, and ultimately answer the question of whether ADE occurs in COVID-19 as it does for diseases like dengue and respiratory syncytial virus.
The A*STAR-affiliated researcher contributing to this research is from the Singapore Immunology Network (SIgN).