Phenotypical changes in peripheral NK cells and their impact on the clinical outcomes of patients with severe pandemic influenza A(H1N1)

NK cells are crucial antiviral effectors. However, their role against emerging respiratory pathogens has not been extensively addressed in humans. Here, we characterized the phenotype of peripheral NK cells in patients with severe pandemic influenza A(H1N1) and age- and sex-matched healthy controls (HC) using an extended panel of flow cytometry antibodies against markers of activation, cytotoxicity, cytokine production, immune memory, and surface receptors. Enrolled patients were grouped according to their clinical outcome (survival vs. death). The study included 42 influenza patients (73% men) with a median age of 48 years, from which eight (26%) died during the follow-up period. All patients were admitted to the intensive care unit and required mechanical ventilation. Individuals with influenza differentiated from HC by reduced numbers of total, CD56bright, CD56dimCD16+, CD27+ memory-like, NKp46+, and perforin+ NK cell subpopulations, but increased CD69+ NK cells. Notably, lower percentages of CD27+ memory-like NK cells correlated with increased alkaline phosphatase levels, a readout of lung damage in patients with acute respiratory distress syndrome. Strikingly, a higher expression of the senescence marker CD57 in CD27+ memory-like NK cells and expansion of double-positive CD27+CD57+ NK cells was characteristic of deceased influenza patients, but not survivors. Finally, despite being reduced in the overall influenza group with respect to HC, increased percentages of IFN-γ+ NK cells distinguished death vs. survival outcomes. Collectively, our results demonstrate that alterations in the phenotype of NK cells influence with the progression and outcomes of patients with severe pandemic influenza A(H1N1) infection. Supported by grants from CONACyT (FORDECyT/10SE/2020/05/14-06, FORDECyT/10SE/2020/05/14-07) and SECTEI CDMX (SECTEI/050/2020) to JZ. JAR-N received a scholarship from CONACyT (CVU-1097402) for achieving her M.S.