Researchers analyse a blood sample in a laboratory. Credit: Getty Images

A study reveals that serum samples from SARS-CoV-2-infected patients can neutralise dengue virus antigen and protect against dengue1. Exposure to SARS-CoV-2 between 2019 and 2021 has been shown to cause less severe dengue symptoms, with no death in dengue-endemic regions in India and elsewhere.

These findings will help provide accurate diagnosis and proper management of the individual and co-infection cases of these two viral diseases, says a team at the CSIR-Indian Institute of Chemical Biology in Kolkata.

Several months into the pandemic, highly endemic dengue regions were relatively less affected by COVID-19 severity and mortality. This phenomenon intrigued scientists, who did blood tests to find any cross-reaction between pre-pandemic dengue virus serum samples and SARS-CoV-2 antigen.

Next, the team, led by virologist Subhajit Biswas, analysed serum samples of 52 COVID-19 patients. About 90% of the samples contained a detectable amount of SARS-CoV-2 antibodies. They found that about 89% of the COVID-19 seropositive cases, including many with no history of dengue exposure, cross-reacted with dengue virus antigen in strip tests.

The researchers found that serum samples from COVID-19 patients also restricted the entry of dengue virus serotype 1 into host cells significantly.

In molecular docking studies, dengue virus antibodies bound to a few critical amino acids in the SARS-CoV-2 spike protein, disrupting its binding to a receptor of host cells. These antibodies also cross-reacted with the spike protein in strip tests.

This indicates that a partial immunity against COVID-19 may possibly exist in dengue-endemic regions, the researchers note.