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Proinflammatory elements mediated through metabolic pathways related to obesity and increased cellular senescence in CD57 expression in CD8+ T cells are associated with postacute sequelae of COVID-19 (PASC), according to a Mexican study. The researchers followed a Mexican cohort of 102 patients 3 months and 6 months after acute SARS-CoV-2 infection.
The study’s principal investigator was Diana Gómez-Martín, MD, PhD, of the Department of Immunology and Rheumatology at the Salvador Zubirán National Institute of Medical Sciences and Nutrition in Mexico City. She told Medscape Spanish Edition that follow-up of the patients began with the objective of understanding the determinative clinical, genetic, metabolic, and immunological factors in the progression of the acute disease. However, clinical aspects associated with PASC developed in the selected cohort. As a result, the study was extended, and the clinical, metabolic, and immunologic conditions in this single-center Mexican cohort were evaluated 3 months 6 months after the onset of infection.
Gómez-Martín explained that the immune senescence in CD57 of CD8+ T cells is one of the best-known findings of the present study. If it is confirmed in future studies, it could have important implications. “Its main implication is the possibility of better understanding the physiopathology of the clinical aspects associated with postacute sequelae of COVID-19, potentially being used for early detection and to provide follow-up aimed at patients, in addition to eventually developing targeted therapeutic strategies such as immunometabolism regulation, in certain populations.”
Patients With PASC
The study was conducted from August 2020 to August 2021. Investigators recruited 102 patients (median age, 50.5 years; 55% were women) at the Mexico City Temporary Unit with a confirmed diagnosis of SARS-CoV-2. Of the patients, 44% had mild or moderate COVID-19, 30% had severe cases, and 26% patients had critical cases. The most frequent comorbidities were obesity (44%), hypertension (24%), and type 2 diabetes (24%). The authors used a questionnaire to assess the presence of symptoms during follow-up. They analyzed immunologic variables at the time of recruitment, as well as levels of cytokines, immunoglobulin G against SARS-CoV-2, and neutrophil extracellular traps (NETs) at 1, 3, and 6 months. At 6 months’ follow-up, 12.7% of the cohort had symptoms compatible with PASC, which was defined for the study as the presence and report of three or more symptoms at 6 months’ follow-up.
As in similar studies, the authors found that female gender, remaining in intensive care, and having had more symptoms and greater titers of anti-SARS-CoV-2 antibodies during the acute infection were associated with the development of clinical aspects associated with PASC. Patients who had the disease at 6 months had increased serum levels of interleukin-1α (6.21 pg/mL vs 2.21 pg/mL), granulocyte colony-stimulating factor (55.08 pg/mL vs 14.68 pg/mL), and interferon γ-induced protein 10 (2309.40 pg/mL vs 780 pg/mL). Also, there was a trend toward an increase in serum concentration of interleukin-1β, interleukin-6, and interferon-γ.
Patients whose condition met the definition of persistent PASC had increased expression of CD57 in CD8+ T cells (42,714 arbitrary units vs 28,506) 6 months after the acute infection. The authors reported that there was no association between the persistence of PASC and the baseline amount of NETs, TRIM63, and anticellular antibodies. Nor was there an association between PASC and the titers of anti-SARS-CoV-2 antibodies at baseline and 1 month after COVID-19 diagnosis. Nonetheless, patients with persistent PASC had higher titers of anti-SARS-CoV-2 IgGs 3 months after the onset of COVID-19.
On the basis of previous data, the researchers aimed to construct a preliminary explanatory model to address the clinical and immunologic features associated with persistent PASC 6 months after SARS-CoV-2 infection. In the univariate analysis, the variables associated with the diagnosis of persistent PASC were the serum levels of granulocyte colony-stimulating factor (odds ratio [OR], 1.01), macrophage inflammatory protein 1-α (OR, 1.13), interferon γ-induced protein 10 (OR, 1.00), interleukin-6 (OR, 1.03), the expression of CD57 in CD8+ T cells (OR, 1.00), and the titers of anti-SARS-CoV-2 IgG at 1 month (OR, 1.45).
Patients with a diagnosis of clinical aspects associated with PASC at 6 months were characterized by certain predisposing factors, such as obesity, greater levels of macrophage inflammatory protein-1α and interferon γ-induced protein 10 in peripheral blood, greater expression of the senescence CD57 marker in CD8+ T lymphocytes, and persistent symptoms at 3 months.
Using these parameters to construct a predictive model after 3 months, the authors found a sensitivity of 97.7%, specificity of 53.8%, positive predictive value of 93.5%, and a negative predictive value of 77.7% for the diagnosis of clinical aspects associated with PASC at 6 months.
One of the researchers who participated in the study was Luis Martínez-Juárez, MD, MPH, DrPH. He is on the operative solutions team at the Carlos Slim Foundation. Martínez-Juárez pointed out that one of the contributions of this study was that it specifically examined the Mexican population. He noted, “According to the findings, obesity is not only a comorbidity associated with more severe progressions during acute COVID-19 disease, but also, through inflammation parameters, such as interleukin-6, interferon γ-induced protein 10, and macrophage inflammatory protein-1α, it’s involved in the development of clinical aspects related to postacute sequelae of COVID-19.”
Gómez-Martín added that finding proinflammatory and obesity parameters in the patients could potentially support the hypothesis of the persistence of virus fragments in adipose tissue as possibly involved in clinical aspects associated with PASC, as some groups have reported in the medical literature.
Angélica Cuapio, MD, DrMed, an immunologist and senior investigator at the Karolinska Institute in Stockholm, Sweden, who did not participate in the study, told Medscape Spanish Edition that the authors’ findings on the sustained increase of the CD57 marker in CD8+ lymphocytes are of notable interest. They may be associated with senescence states or cellular aging, or with a stage of chronic viral infections. Therefore, Cuapio argued, it would have been valuable to include cellular markers of the innate system, such as natural killer cells, since in various infections, an increase in CD57 in lymphocytes is accompanied by an almost proportional increase of this marker in natural killer cells.
“This information would help to determine more accurately if we are talking about a cellular senescence or more about a chronic infection in persistent COVID-19.” The finding is important, but future research is needed in this developing field.
Cuapio pointed out that the authors found an interesting elevation in interleukin-1α in patients with clinical aspects associated with PASC in a clinically well-characterized population in Mexico. “It is possible that this is a specific marker either of a specific population or location, or this could be an association with a humoral response. Despite the fact that this finding is new and unclear, it is worth investigating. This study is of great value for the scientific community because it’s one more piece in the complex puzzle of clinical aspects associated with postacute sequelae of COVID-19.”
Gómez-Martín noted that the main limitations of the study consist of its single-center design and the small patient sample. Martínez-Juárez added that the study did not consider reinfections. In future studies, it would be ideal to integrate other molecular assessments associated with various hypotheses of the physiopathology of clinical aspects associated with PASC, such as microbiota alteration, coagulation anomalies, endothelial damage, and dysfunctional neurologic signaling.