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A role for IL-15 and sMAdCAM in Covid19 associated cellular immune pathology
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  • Amit Kumar Singh,
  • Nandini Kasarpalkar,
  • Shilpa Bhowmick,
  • Gaurav Paradkar,
  • Mayur Talreja,
  • Karan Shah,
  • Abhishekh Tiwari,
  • Harsha Palav,
  • Snehal Kaginkar,
  • Rajiv Kulkarni,
  • Ashwini Patil,
  • Varsha Kalsurkar,
  • Sachee Agrawal,
  • Jayanthi Shastri,
  • Rajesh Dere,
  • Smita Mahale,
  • Ramesh Bharmal,
  • Vikrant Bhor,
  • Vainav Patel
Amit Kumar Singh
NIRRH
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Nandini Kasarpalkar
NIRRH
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Shilpa Bhowmick
NIRRH
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Gaurav Paradkar
NIRRH
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Mayur Talreja
NIRRH
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Karan Shah
NIRRH
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Abhishekh Tiwari
NIRRH
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Harsha Palav
NIRRH
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Snehal Kaginkar
NIRRH
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Rajiv Kulkarni
NIRRH
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Ashwini Patil
NIRRH
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Varsha Kalsurkar
NIRRH
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Sachee Agrawal
TN Medical College & BYL Nair Hospital, Mumbai
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Jayanthi Shastri
TN Medical College & BYL Nair Hospital, Mumbai
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Rajesh Dere
BKC COVID Jumbo Facility, Municipal Corporation of Greater Mumbai
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Smita Mahale
NIRRH
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Ramesh Bharmal
TN Medical College & BYL Nair Hospital, Mumbai
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Vikrant Bhor
NIRRH
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Vainav Patel
NIRRH

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Abstract

Immune cell dysregulation and lymphopenia characterize COVID-19 pathology in moderate to severe disease. While underlying inflammatory factors have been extensively studied, homeostatic and mucosal migratory signatures remain largely unexplored as causative factors. In this study we evaluated the association of circulating IL-6, soluble mucosal addressin cell adhesion molecule (sMAdCAM) and IL-15 with cellular dysfunction characterizing mild and hypoxemic stages of COVID-19. A cohort of SARS-CoV-2 infected individuals (n=125) at various stages of disease progression together with healthy controls (n=16) were recruited from COVID Care Centres (CCCs) across Mumbai, India. Multiparametric flow cytometry was used to perform in-depth immune subset characterization and to measure plasma IL-6 levels. sMAdCAM, IL-15 levels were quantified using ELISA. Distinct depletion profiles, with relative sparing of CD8 effector memory and CD4+ regulatory T cells were observed in hypoxemic disease within the lymphocyte compartment. An apparent increase in the frequency of intermediate monocytes characterized both mild as well as hypoxemic disease. IL-6 levels inversely correlated with those of sMAdCAM and both markers showed converse associations with observed lympho-depletion suggesting opposing roles in pathogenesis. Interestingly, IL-15, a key cytokine involved in lymphocyte activation and homeostasis, was detected in symptomatic individuals but not in healthy controls or asymptomatic cases. Further, negative association of plasma IL-15 with depleted T, B and NK subsets suggested a compensatory production of this cytokine in response to the profound lymphopenia. Finally, higher levels of plasma IL-15 and IL-6, but not sMAdCAM, were associated with longer duration of hospitalization.