In the paper, researchers correlated patient symptoms with in-depth profiling of blood cells and plasma components throughout COVID-19 infection to identify factors associated with the development of PASC. PASC, the technical long COVID, is a range of new, returning, or ongoing health problems people can experience four or more weeks following infection. The authors followed 309 patients from initial clinical diagnosis to early-stage recovery from acute disease, spanning up to two to three months post-diagnosis, as well as 457 control patients.

Using IsoPlexis' single-cell functional proteomics platform, the researchers were able to identify correlations between the enhanced presence of certain polyfunctional immune cell types and the presentation of inflammation associated with PASC:

• Increased frequency of "supervillain" T-cell subsets (CD4+ and CD8+ T cells) is positively associated with certain PASC symptoms/conditions, or endotypes, and disease severity at convalescence.
• Similarly, the presence of "supervillain" monocytes in convalescent patients compared to healthy subjects is correlated with all of the major PASC endotypes, indicating the impact of monocytes on sustained inflammation at convalescence.
• Natural killer cells in PASC endotypes played less of an active role in convalescence inflammation of PASC.

IsoPlexis' single-cell functional proteomics provided a unique assessment to dissect the functional impacts of different cell types across multiple time points and the interplay between innate and adaptive immune responses that contributed to effector functions or inflammation in PASC.

This study follows a previously published Immunity paper, where IsoPlexis' platform identified mechanisms of inflammation in moderate to severe cases of COVID-19.