COVID-19: Coronavirus immunity without antibodies? The plot thickens

I recently wrote about a paper showing robust T helper cell reactivity to SARS-CoV-2 in a group of recovered patients as well as the tantalizing finding that 40-60% of unexposed individuals (samples obtained 2015-18) showed cross-reactivity to SARS-CoV-2, suggesting that exposure to circulating coronaviruses responsible for the common cold could be protective against SARS-CoV-2.

Meanwhile, I just came across a paper published on May 8th that seems to throw cold water onto the aforementioned findings…but still offers some good news.

The bad news: These authors found that individuals exposed to the original SARS virus during the 2002-04 epidemic showed no cross-neutralization of SARS-CoV-2…which is surprising, since the original SARS virus is believed to be SARS-CoV-2’s closest cousin.

The good news: Such patients showed robust neutralization of the original SARS virus even as much as 17 years after initial infection, giving us every reason to think that immunity against SARS-CoV-2 will be equally long-lasting.

From the abstract:

“…our data demonstrated that there is no detectable cross-neutralization by SARS patient sera against SARS-CoV-2. We also found that there are significant levels of neutralizing antibodies in recovered SARS patients 9–17 years after initial infection. These findings will be of significant use in guiding the development of serologic tests, formulating convalescent plasma therapy strategies, and assessing the longevity of protective immunity for SARS-related coronaviruses in general as well as vaccine efficacy.”

There is definitely a major discrepancy between the two papers; if common cold viruses spur robust cross-reactivity to SARS-CoV-2 peptides, then it seems completely implausible that the first SARS virus wouldn’t do the same. As with so much else regarding the pandemic, these results are characteristic of the highly uncertain, often contradictory findings in the deluge of published research. For all we know, there could some other factor at play that makes exposure to endemic coronaviruses protective but not exposure to SARS. Time will tell.


[1] Anderson DE, Tan CW, Chia WN, et al. Lack of cross-neutralization by SARS patient sera towards SARS-CoV-2. Emerging Microbes & Infections. 2020;9(1):900-902. doi:10.1080/22221751.2020.1761267

 

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