CD8+ T-cell PET/CT Imaging in COVID-19 Patients

Overview

A subset of patients diagnosed with severe acute respiratory syndrome (SARS)-CoV2 infection present with lymphopenia. The degree of lymphopenia, and in particular reduced cluster of differentiation (CD)8+ T-cell numbers, is correlated with clinical deterioration and intensive care unit (ICU) admission. The underlying reasons for lymphopenia in coronavirus disease (COVID)-19 is currently unclear, We aim to assess differences in the in vivo distribution of CD8+ T-cells in patients with proven SARS-CoV2 presenting with lymphopenia or with normal lymphocyte counts, using Zirconium-89 (\[89Zr\])Df-IAB22M2C positron emission tomography (PET) imaging.

Rationale: A subset of patients diagnosed with SARS-CoV2 infection present with lymphopenia. The degree of lymphopenia, and in particular reduced CD8+ T-cell numbers, is strongly correlated with clinical deterioration and ICU admission . The underlying reasons for lymphopenia in COVID-19 is currently unclear, but several hypotheses have been put forward; 1) sequestration of CD8+ T-cells in peripheral tissues (e.g. lung) either during the effector phase of their lifespan or passively by local chemotactic signals, 2) accelerated maturation and apoptosis either induced by storm of inflammatory cytokines or direct infection or 3) resulting from decreased lymphopoiesis induced by reduced levels of stem cell factor. The lack of data on in vivo distribution of CD8+ T-cells hampers a more thorough understanding of this critical prognostic factor. Aim: We aim to assess differences in the in vivo distribution of CD8+ T-cells in patients with proven SARS-CoV2 presenting with lymphopenia or with normal lymphocyte counts, using \[89Zr\]Df-IAB22M2C PET/CT imaging. Study design: This is a prospective, observational non-randomized pilot study in 20 patients with microbiologically proven SARS-CoV2 infection. All patients will undergo a whole body \[89Zr\]Df-IAB22M2C PET/CT scan. Study population: Twenty patients ≥50 years of age with proven COVID-19, who are admitted to the ward will be included, patients will be stratified according to lymphocyte counts on admission to ensure an even distribution: presenting with lymphopenia (\<1.0 x10e9/L) (n=10) and with lymphocyte numbers within normal range (1.0 - 3.5 x10e9/L) (n=10). Study procedure: All patients will undergo a \[89Zr\]Df-IAB22M2C PET/CT scan 21-27 hours post intravenous injection of 1.5mg protein dose labelled with 37 megabecquerel (MBq) (1 mCi) 89Zr; and one additional blood sample at the day of scanning. Primary study objective: The primary objective of this study is to assess differences in the in vivo distribution of CD8+ T-cells in patients with proven SARS-CoV-2 presenting with lymphopenia or with normal lymphocyte counts, using \[89Zr\]Df-IAB22M2C PET/CT imaging. Secondary study objectives: 1. To assess the spatial correlation between \[89Zr\]Df-IAB22M2C uptake and abnormal findings on routine contrast-enhanced CT scan of the chest 2. To assess the correlation between in vivo biodistribution of \[89Zr\]Df-IAB22M2C and concurrent flowcytometric phenotypic and quantitative assessment of lymphocyte populations 3. To explore the correlation between in vivo biodistribution of \[89Zr\]Df-IAB22M2C and clinical course of disease