The primary objective of this study is to establish differences in susceptibility to SARS CoV-2 infection among health care workers (HCW) highly exposed to patients with COVID-19 diagnosis. To ascertain this issue, we evaluated: - Changes in receptor polymorphism (ACE2 and CD26 receptor study. - SARS-CoV-2 CD4/CD8 T cell response (CTL) - Different KIR phenotypes
Only 24% of health care workers (HCW) had developed inmunological response to SARS CoV-2
infection in one centre attending thousands of COVID-19 patients, and with shorteness of
personal protective equipments. Our hypothesis is that this relatively low number of infected
HCW could be secondary to:
1. Differences in susceptibility to infection mediated by changes in viral receptors. Thus,
it is important to characterize and genotyping the main receptor for SARS-CoV-2, ACE2,
and other related receptor, such as CD26.
2. Increased cellular immune response, offering cross-immunity against SARS CoV-2 infection
by previous exposure to other coronavirus or respiratory pathogens. A specific CD4/CD8 T
cell response to viral peptides could respond this question
3. Specific KIR phenotypes (Killer Immunoglobulin-like Receptors): Natural killer cells
(NK) response to alterations of class I HLA molecules presented in infected cells. An
increase in class I HLA expression could lead to an increase in NK activation by
increasing its ability to produce IFN-gamma.
Diagnostic Test: Susceptibility to infection
ACE2 and CD26 receptor study: After genomic DNA extraction and quantification using a NanoDrop-1000, 14 ACE2 SNPs (rs1978124, rs2048683, rs2074192, rs2106809, rs2285666, rs233575, rs4240157, rs4646142, rs4646155, rs4646156, rs4646188, rs4830542, rs6632677, and rs879922) will be studied. In addition, one CD26 (DPP4) SNP (rs7608798) will be analysed (qualitative measure).
SARS-CoV-2 CD4/CD8 T cell response: SARS-CoV-2 peptides (Prot-S, Pros-N and Port-M) will be used to activate CD4 and CD8 T cells. Cytokines released, such as IFNg, TNFa, IL4, IL17A, and IL2, from each cell subset will be measured by flow cytometry (quantitative measure).
KIR characterization: Characterization of the presence of 14 genes plus 2 pseudogenes of KIR gene family (qualitative genotyping) by PCR, mRNA expression profiling (quantitative measures) by RT-PCR, and phenotyping of human NK cells analyzing different KIR receptors (quantitative measure) by flow cytometry, will be analyzed.
Other Name: KIR measurements
Inclusion criteria
- HCW older than 18 years
- Highly exposed to COVID-19 according to the definition
- Negative (cases) or positive (controls) serology against SARS-CoV-2 infection
Exclusion criteria
- Presence of any disease / treatment which could alter the susceptibility (corticoid
therapy, chemotherapy, monoclonal antibodies)
- Pregnancy
High exposure definition: direct and continued care of COVID-19 diagnosed patients for 2
weeks or more, without aerosol- generating procedures, with inappropriate personal
protective equipment (PPE), or unprotected exposure to patients with COVID-19 during
aerosol-generating procedures.
The definition of appropriate PPE was based on previous recommendations. The absence of any
part of the PPE constituted an unprotected exposure. We defined the following as
aerosol-generating procedures: airway suction, application of a high-flow O2 instrument,
bronchoscopy, endotracheal intubation, tracheostomy, nebulizer treatment, sputum induction,
positive pressure ventilation, manual ventilation and cardiopulmonary resuscitation.
Hospital Ramon y Cajal
Madrid, Spain
Jose L Casado, MD, PhD, Principal Investigator
Ramon y Cajal Physician