Pathogenic Connections in Post-COVID Conditions: What Do We Know in the Large Unknown? A Narrative Review

Host factors of SARS-CoV-2 in infection, pathogenesis, and long-term effects

SARS-CoV-2 is the causative virus of the devastating COVID-19 pandemic that results in an unparalleled global health and economic crisis. Despite unprecedented scientific efforts and therapeutic interventions, the fight against COVID-19 continues as the rapid emergence of different SARS-CoV-2 variants of concern and the increasing challenge of long COVID-19, raising a vast demand to understand the pathomechanisms of COVID-19 and its long-term sequelae and develop therapeutic strategies beyond the virus per se. Notably, in addition to the virus itself, the replication cycle of SARS-CoV-2 and clinical severity of COVID-19 is also governed by host factors. In this review, we therefore comprehensively overview the replication cycle and pathogenesis of SARS-CoV-2 from the perspective of host factors and host-virus interactions. We sequentially outline the pathological implications of molecular interactions between host factors and SARS-CoV-2 in multi-organ and multi-system long COVID-19, and summarize current therapeutic strategies and agents targeting host factors for treating these diseases. This knowledge would be key for the identification of new pathophysiological aspects and mechanisms, and the development of actionable therapeutic targets and strategies for tackling COVID-19 and its sequelae.

SARS-CoV-2-associated T-cell infiltration in the central nervous system

Objectives

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). Although an acute SARS-CoV-2 infection mainly presents with respiratory illness, neurologic symptoms and sequelae are increasingly recognised in the long-term treatment of COVID-19 patients. The pathophysiology and the neuropathogenesis behind neurologic complications of COVID-19 remain poorly understood, but mounting evidence points to endothelial dysfunction either directly caused by viral infection or indirectly by inflammatory cytokines, followed by a local immune response that may include virus-specific T cells. However, the type and role of central nervous system-infiltrating T cells in COVID-19 are complex and not fully understood.

Methods

We analysed distinct anatomical brain regions of patients who had deceased as a result of COVID-19-associated pneumonia or complications thereof and performed T cell receptor Vβ repertoire sequencing. Clonotypes were analysed for SARS-CoV-2 association using public TCR repertoire data.

Results

Our descriptive study demonstrates that SARS-CoV-2-associated T cells are found in almost all brain areas of patients with fatal COVID-19 courses. The olfactory bulb, medulla and cerebellum were brain regions showing the most SARS-CoV-2 specific sequence patterns. Neuropathological workup demonstrated primary CD8+ T-cell infiltration with a perivascular infiltration pattern.

Conclusion

Future research is needed to better define the relationship between T-cell infiltration and neurological symptoms and its long-term impact on patients' cognitive and mental health.

Long COVID Symptoms in Non-Hospitalised Patients: A Retrospective Study

INTRODUCTION

The COVID-19 pandemic has presented numerous challenges to healthcare systems. As the number of affected individuals continues to rise, it is crucial to find preventive, diagnostic, and therapeutic approaches. This study aims to describe different COVID-19 sequelae within a Primary Health Care population.

METHODS

A retrospective cohort study was conducted in adults diagnosed with COVID-19 from March 2020 to April 2022, excluding pregnant women, minors, nursing home residents, hospitalizations, and deaths. Data was gathered from surveillance records on the Trace COVID-19® platform, a pre-set original questionnaire (which included the Portuguese version of the World Health Organization's Quality of Life Assessment Instrument), and, if needed, patient electronic health records. Information on sociodemographic and clinical characteristics of acute COVID-19 was collected along with long COVID symptoms.

RESULTS

This study included 284 patients, aged 19 to 99 years old. The five most prevalent acute COVID-19 symptoms were fever (50.0%), tiredness (48.2%), myalgias (44.7%), dry cough (37.7%) and odynophagia (36.3%). Symptoms related to the neurological system (23.2%) and tiredness (22.9%) were the most prevalent in long COVID symptoms. Acute tiredness and arthralgia were associated with all long COVID outcomes. The associations between acute COVID-19 symptoms with long COVID outcomes were stronger for anosmia [OR = 5.07, 95% confidence interval (CI) 2.49 - 10.36, p < 0.001] on a neurological chapter, acute tiredness for long lasting tiredness (OR = 4.07, 95% CI 2.07 - 8.02, p = 0.041), fatigue for muscles and/or bones chapter (OR = 7.55, 95% CI 3.06 - 18.66, p < 0.001), tiredness on an endocrine/hormonal chapter (OR = 6.54, 95% CI 2.37 - 18.04, p < 0.001), dyspnea for respiratory symptoms (OR = 5.67, 95% CI 1.92 - 16.74, p = 0.002) and fever for stomach or intestine symptoms (OR = 8.06, 95% CI 2.55 - 25.47, p < 0.001). Almost all quality of life dimensions were negatively associated with the number of long COVID symptoms.

CONCLUSION

A higher number of acute symptoms, as well as the presence of specific COVID-19 symptoms were associated with reported symptoms ≥ 12 weeks after infection. In the studied population, an increased number of symptoms in both acute and long COVID had a significant negative impact on the perception of overall quality of life. The identification of these relationships could provide a new perspective for post-COVID care.

Diagnostic features of multiple organic system disorders associated with COVID-19 in a child of primary school age

   The advent of the COVID-19, specialists are increasingly encountering previously unknown pathological conditions in their practice. For some time, we have believed that COVID-19 in children is most often mild and asymptomatic. However, with the passage of time and the accumulation of the experience, it became obvious that the new infectious disease it will be quite severe in children. Differential diagnosis of multiple organ disorders in children during the COVID-19 pandemic should be primary carried out with the Multisystem Inflammatory Syndrome in Children, associated with COVID-19 (MIS-C), as well as Long-COVID-19. According to published data, the manifestations of these conditions are due to frequent lesions of the gastrointestinal tract (60–100 %), cardiovascular (80 %), nervous (29–58 %) and respiratory (21–65 %) systems. At present, there is no exact idea of these pathological conditions, the criteria for their diagnosis and the tactics of managing children, not only at the stage of diagnosis, but also at the stage of observation. The authors present a diagnostically complex clinical case describing the development of multiple organ damage in a 7-year-old child after contact with a mother who was sick with COVID-19. The data on the course features, the results of the examination and the difficulties of differential diagnosis of this case with other diseases with a similar clinic are summarized.