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Long-COVID and Its Complications

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Pathology, Diagnostics, and Therapeutics".

Deadline for manuscript submissions: 4 December 2025 | Viewed by 20776

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Guest Editor
Institute of Immunology and Physiology of the Ural Branch of the RAS, 620000 Ekaterinburg, Russia
Interests: psychosomatic disorders; PTSD; immunology; cardiology; stress; pediatric dentistry; oncology; inflammation
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Special Issue Information

Dear Colleagues,

Long COVID, a persistent multisystem condition following COVID-19 infection, poses significant challenges for medical practitioners and researchers. Despite the growing number of affected individuals, the mechanisms underlying long COVID's pathophysiology remain unclear. While organ damage from the acute infection phase likely accounts for some symptoms, specific long-lasting inflammatory mechanisms have also been proposed.

This Special Issue aims to explore the enigmatic pathophysiological mechanisms of long COVID, focusing on different levels of the relationship between the nervous and immune systems and analyzing broader categories that may offer insights into potential therapeutic interventions. Researchers are invited to contribute their work on diverse aspects of long COVID to advance our understanding and management of this challenging condition.

Key Points:

  • Immunological dysregulation: investigating the immune system's role in long COVID, including acquired immune deficiency, auto-immunity, and potential persistent viral presence;
  • Persistent inflammatory processes: addressing the potential mechanisms of organ damage from the acute infection phase and investigating persistent inflammatory processes as contributors to long COVID;
  • Neurological aspects of the pathogenesis of long COVID associated with an imbalance in the action of various neurotransmitters and inflammatory mediators in the central nervous system;
  • The relationship between disturbances of the gut microbiome, gut barrier function and blood-brain barrier dysfunction in the pathogenesis of long COVID;
  • Molecular mechanisms of dysfunction of the limbic–reticular–hypothalamic complex and the hypothalamic–pituitary–adrenal axis in the manifestations of long COVID and its complications;
  • Autonomic nervous system dysfunction: Investigating autonomic nervous system damage as a possible explanation for various long COVID symptoms, even without clear evidence of organ damage;
  • Multisystem nature of long COVID: the role of comorbidities and low-grade chronic systemic inflammation in the development of multiple organ dysfunction as manifestations of post-COVID syndrome.

Led by Dr. Alexey Sarapultsev and assisted by our Topical Advisory Panel Member Dr. Zhan Zhang (Emory University School of Medicine), this Special Issue seeks to consolidate research on these broader mechanisms underlying long COVID, offering a comprehensive understanding of the condition's complexities and paving the way for potential therapeutic avenues. Researchers are invited to contribute their work on these topics to advance our comprehension and management of this challenging condition.

Dr. Alexey Sarapultsev
Guest Editor

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Keywords

  • acquired immune deficiency
  • auto-immunity
  • blood–brain barrier dysfunction
  • complication
  • COVID-19
  • gut microbiome
  • hypothalamic–pituitary–adrenal axis
  • immune dysfunction
  • long COVID
  • multisystem dysfunction
  • neurological complications
  • SARS-CoV-2
  • systemic inflammation

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Published Papers (5 papers)

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Research

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16 pages, 1453 KiB  
Article
LEF1-AS1 Deregulation in the Peripheral Blood of Patients with Persistent Post-COVID Symptoms
by Alisia Madè, Santiago Nicolas Piella, Marco Ranucci, Carlo Gaetano, Laura Valentina Renna, Rosanna Cardani, Gaia Spinetti, Valentina Milani and Fabio Martelli
Int. J. Mol. Sci. 2025, 26(10), 4806; https://doi.org/10.3390/ijms26104806 - 17 May 2025
Viewed by 104
Abstract
Long COVID denotes the persistence of symptoms after acute SARS-CoV-2 infection lasting for at least two months without another identifiable cause. Affecting an estimated 15% of COVID-19 patients, long COVID manifests in a wide range of symptoms. Despite extensive research on its one-year [...] Read more.
Long COVID denotes the persistence of symptoms after acute SARS-CoV-2 infection lasting for at least two months without another identifiable cause. Affecting an estimated 15% of COVID-19 patients, long COVID manifests in a wide range of symptoms. Despite extensive research on its one-year effects, limited data exist beyond 12 months. Due to the different manifestations of long COVID, its diagnosis can be challenging. Identifying potential mechanistic contributors and biomarkers would be highly valuable. Recent studies have highlighted the potential of noncoding RNAs (ncRNAs) as biomarkers for disease stratification in COVID-19. Specifically, we have recently identified miR-144-3p and a subset of lncRNAs as candidates for assessing disease severity and outcomes in COVID-19. This nested case–control study extends such investigations to 98 long COVID patients recruited 18 months after hospitalization, exploring the relationship between circulating ncRNA expression and persistent symptoms. While miR-144-3p, HCG18, and lncCEACAM21 expression did not differ between symptomatic and asymptomatic patients, LEF1-AS1 was downregulated in the peripheral blood mononuclear cells (PBMCs) of symptomatic patients. Of note, multiple LEF1-AS1 isoforms and LEF1 sense transcript levels were reduced and negatively correlated with relevant clinical markers. While further studies are needed, our discoveries offer new perspectives on the diagnosis and management of persistent long COVID. Full article
(This article belongs to the Special Issue Long-COVID and Its Complications)
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22 pages, 358 KiB  
Article
Association of Vitamin D Supplementation with Glutathione Peroxidase (GPx) Activity, Interleukine-6 (IL-6) Levels, and Anxiety and Depression Scores in Patients with Post-COVID-19 Condition
by Iván Ignacio-Mejía, Cindy Bandala, José Francisco González-Zamora, Leslie Chavez-Galan, Ivette Buendia-Roldan, Karina Pérez-Torres, María Zobeida Rodríguez-Díaz, Denilson Xipe Pacheco-Tobón, Saray Quintero-Fabián, Marco Antonio Vargas-Hernández, Humberto Carrasco-Vargas, Ramcés Falfán-Valencia, Gloria Pérez-Rubio, Kevin Alexis Hernández-Lara, Saúl Gómez-Manzo, Daniel Ortega-Cuellar, Fredy Ignacio-Mejía and Noemí Cárdenas-Rodríguez
Int. J. Mol. Sci. 2025, 26(10), 4582; https://doi.org/10.3390/ijms26104582 - 10 May 2025
Viewed by 341
Abstract
Coronavirus disease 2019 (COVID-19) presents with various symptoms, and some patients develop post-COVID-19 condition (PCC). Vitamin D has shown therapeutic potential in COVID-19 and may offer benefits for PCC. The aim of this study was to evaluate the differences associated with two supplementation [...] Read more.
Coronavirus disease 2019 (COVID-19) presents with various symptoms, and some patients develop post-COVID-19 condition (PCC). Vitamin D has shown therapeutic potential in COVID-19 and may offer benefits for PCC. The aim of this study was to evaluate the differences associated with two supplementation strategies (bolus and daily) on interleukin-6 (IL-6) levels, glutathione peroxidase (GPx) activity, and clinical outcomes in PCC patients, regardless of whether target 25 (OH) D levels reached the ideal range. We conducted a self-controlled study in which 54 participants with PCC were supplemented with vitamin D3 (n = 28 bolus and n = 26 daily) for 2 months. Blood samples were collected to measure IL-6 levels and GPx activity using spectrophotometric methods. The Hospital Anxiety and Depression Scale (HADS) was used to assess mental function. Both bolus and daily vitamin D supplementation were significantly associated with increased GPx activity and decreased IL-6 levels. Daily supplementation was additionally associated with a significant reduction in anxiety and depression scores. However, neither regimen was associated with improvements in cough, dyspnea, or fatigue. These findings suggest a potential association between vitamin D supplementation and improvements in antioxidant and neuropsychiatric parameters in PCC, possibly mediated by its immunomodulatory and antioxidant properties. Further placebo-controlled trials are warranted to determine whether these observed associations reflect causal relationships. Full article
(This article belongs to the Special Issue Long-COVID and Its Complications)
26 pages, 2827 KiB  
Article
Revealing the Hidden Impacts: Insights into Biological Aging and Long-Term Effects in Pauci- and Asymptomatic COVID-19 Healthcare Workers
by Manuela Campisi, Luana Cannella, Anna Bordin, Angelo Moretto, Maria Luisa Scapellato, Paola Mason, Filippo Liviero, Sofia Pavanello and on behalf of Occupational Medicine Working Group
Int. J. Mol. Sci. 2024, 25(15), 8056; https://doi.org/10.3390/ijms25158056 - 24 Jul 2024
Cited by 2 | Viewed by 8331
Abstract
This study explores the role of inflammation and oxidative stress, hallmarks of COVID-19, in accelerating cellular biological aging. We investigated early molecular markers—DNA methylation age (DNAmAge) and telomere length (TL)—in blood leukocytes, nasal cells (NCs), and induced sputum (IS) one year post-infection in [...] Read more.
This study explores the role of inflammation and oxidative stress, hallmarks of COVID-19, in accelerating cellular biological aging. We investigated early molecular markers—DNA methylation age (DNAmAge) and telomere length (TL)—in blood leukocytes, nasal cells (NCs), and induced sputum (IS) one year post-infection in pauci- and asymptomatic healthcare workers (HCWs) infected during the first pandemic wave (February–May 2020), compared to COPD patients, model for “aged lung”. Data from questionnaires, Work Ability Index (WAI), blood analyses, autonomic cardiac balance assessments, heart rate variability (HRV), and pulmonary function tests were collected. Elevated leukocyte DNAmAge significantly correlated with advancing age, male sex, daytime work, and an aged phenotype characterized by chronic diseases, elevated LDL and glycemia levels, medications affecting HRV, and declines in lung function, WAI, lymphocyte count, hemoglobin levels, and HRV (p < 0.05). Increasing age, LDL levels, job positions involving intensive patient contact, and higher leukocyte counts collectively contributed to shortened leukocyte TL (p < 0.05). Notably, HCWs exhibited accelerated biological aging in IS cells compared to both blood leukocytes (p ≤ 0.05) and NCs (p < 0.001) and were biologically older than COPD patients (p < 0.05). These findings suggest the need to monitor aging in pauci- and asymptomatic COVID-19 survivors, who represent the majority of the general population. Full article
(This article belongs to the Special Issue Long-COVID and Its Complications)
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Review

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34 pages, 1791 KiB  
Review
Exploring the Pathophysiology of Long COVID: The Central Role of Low-Grade Inflammation and Multisystem Involvement
by Evgenii Gusev and Alexey Sarapultsev
Int. J. Mol. Sci. 2024, 25(12), 6389; https://doi.org/10.3390/ijms25126389 - 9 Jun 2024
Cited by 9 | Viewed by 4114
Abstract
Long COVID (LC), also referred to as Post COVID-19 Condition, Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), and other terms, represents a complex multisystem disease persisting after the acute phase of COVID-19. Characterized by a myriad of symptoms across different organ systems, LC presents [...] Read more.
Long COVID (LC), also referred to as Post COVID-19 Condition, Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), and other terms, represents a complex multisystem disease persisting after the acute phase of COVID-19. Characterized by a myriad of symptoms across different organ systems, LC presents significant diagnostic and management challenges. Central to the disorder is the role of low-grade inflammation, a non-classical inflammatory response that contributes to the chronicity and diversity of symptoms observed. This review explores the pathophysiological underpinnings of LC, emphasizing the importance of low-grade inflammation as a core component. By delineating the pathogenetic relationships and clinical manifestations of LC, this article highlights the necessity for an integrated approach that employs both personalized medicine and standardized protocols aimed at mitigating long-term consequences. The insights gained not only enhance our understanding of LC but also inform the development of therapeutic strategies that could be applicable to other chronic conditions with similar pathophysiological features. Full article
(This article belongs to the Special Issue Long-COVID and Its Complications)
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15 pages, 635 KiB  
Review
The Microbiota in Long COVID
by Carmen Álvarez-Santacruz, Sylwia D. Tyrkalska and Sergio Candel
Int. J. Mol. Sci. 2024, 25(2), 1330; https://doi.org/10.3390/ijms25021330 - 22 Jan 2024
Cited by 19 | Viewed by 6699
Abstract
Interest in the coronavirus disease 2019 (COVID-19) has progressively decreased lately, mainly due to the great effectivity of vaccines. Furthermore, no new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants able to circumvent the protection of these vaccines, while presenting high transmissibility and/or [...] Read more.
Interest in the coronavirus disease 2019 (COVID-19) has progressively decreased lately, mainly due to the great effectivity of vaccines. Furthermore, no new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants able to circumvent the protection of these vaccines, while presenting high transmissibility and/or lethality, have appeared. However, long COVID has emerged as a huge threat to human health and economy globally. The human microbiota plays an important role in health and disease, participating in the modulation of innate and adaptive immune responses. Thus, multiple studies have found that the nasopharyngeal microbiota is altered in COVID-19 patients, with these changes associated with the onset and/or severity of the disease. Nevertheless, although dysbiosis has also been reported in long COVID patients, mainly in the gut, little is known about the possible involvement of the microbiota in the development of this disease. Therefore, in this work, we aim to fill this gap in the knowledge by discussing and comparing the most relevant studies that have been published in this field up to this point. Hence, we discuss that the relevance of long COVID has probably been underestimated, and that the available data suggest that the microbiota could be playing a pivotal role on the pathogenesis of the disease. Further research to elucidate the involvement of the microbiota in long COVID will be essential to explore new therapeutic strategies based on manipulation of the microbiota. Full article
(This article belongs to the Special Issue Long-COVID and Its Complications)
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