Does hypersialylation compensate the functional Alpha1-AntiTrypsin (A1AT) deficiency in all critically ill patients?

Alpha-1 antitrypsin (A1AT) is the major circulating serine protease inhibitor. Hypersialylated glycoforms (HSG) are produced to boost A1AT anti-inflammatory and anti-protease properties. Their occurrence and prognostic impact outside severe COVID-19 or community-acquired pneumonia are unknown. Our aim was to clarify the occurrence of A1AT functional deficiency and HSG in patients admitted into intensive care unit (ICU) for any cause. A1AT and elastase inhibitory capacity (EIC) were measured in serum. Functional A1AT deficiency was defined by a measured EIC/calculated EIC Ratio ≤0.85. HSG were identified by isoelectrofocusing and quantified by gel densitometry. A total of 248 serum samples was analyzed, 173 from COVID-19 and 75 from non COVID-19 patients. A functional A1AT deficiency occurred 3-fold more frequently in non-COVID-19 than in COVID-19 patients: 18.7 % vs 6.9 % and was not associated with more frequent S/Z deficient alleles. Functional deficiency was also more frequent in deceased than alive patients in COVID-19 group. M0 and M1 HSG of A1AT occurred in around half of patients but the relative proportion of M1 significantly increased in deceased vs alive patients only in the non-COVID-19 group explaining the absence of worsening of the functional deficiency. In conclusion, our study shows that a functional A1AT deficiency is more frequently observed in patients admitted to the ICU for a cause unrelated to COVID-19, as well as in those with an unfavorable evolution. Among the latter, only those admitted for non-COVID-19 tried to compensate the functional deficiency by increasing the proportion of M1 HSG of A1AT.