Persistent Circulating Severe Acute Respiratory Syndrome Coronavirus 2 Spike Is Associated With Post-acute Coronavirus Disease 2019 Sequelae

Assessing the Impact of Post-COVID Clinics on 6-Month Health Care Utilization for Patients With Long COVID: A Single-Center Experience

Objective

To assess the impact of post-COVID clinics by examining the association between their early usage and downstream health care utilization.

Patients and Methods

In a case-control study spanning data from March 11, 2020 to June 1, 2023, patients with Long COVID were identified from a major health system using diagnosis codes. The Fast, Large-Scale Almost Matching Exactly algorithm was used to match patients who presented early to post-COVID clinics with patients with Long COVID who did not attend such clinics. Matching was performed on demographic characteristics, acute COVID severity, comorbidities, diagnosis date, and vaccination, to reduce confounders for the comparison of the health care utilization and mortality between cohorts.

Results

When exactly matching on all 46 features, the algorithm yielded 2814 matched patients, of whom 692 (24.6%; 66.6% females; mean [SD] age, 48.8 [14.5] years) were seen in post-COVID clinics within the first 6 months and 2122 (75.4%; 64.1% females; mean [SD] age, 49.7 [15.2] years) who were not. The average treatment effect (95% CI) of early post-COVID clinic usage was -0.60 (-0.83 to -0.39) on inpatient visits, -0.19 (-0.26 to -0.11) on emergency department visits, 7.62 (6.96-8.56) on outpatient visits, -$3467 (-$6267 to -$754) on estimated costs, and -0.006 (-0.010 to -0.003) on mortality.

Conclusion

Early usage of post-COVID clinics by patients with Long COVID is associated with not only fewer downstream inpatient stays, emergency department visits, estimated costs, and reduced mortality within the first 6 months but also greater outpatient utilization. Results suggest early post-COVID clinic involvement shifts care to outpatient settings, potentially reducing costs and mortality.

NETosis: A key player in autoimmunity, COVID-19, and long COVID

NETosis, the process through which neutrophils release neutrophil extracellular traps (NETs), has emerged as a crucial mechanism in host defense and the pathogenesis of autoimmune responses. During the SARS-CoV-2 pandemic, this process received significant attention due to the central role of neutrophil recruitment and activation in infection control. However, elevated neutrophil levels and dysregulated NET formation have been linked to coagulopathy and endothelial damage, correlating with disease severity and poor prognosis in COVID-19. Moreover, it is known that SARS-CoV-2 can induce persistent low-grade systemic inflammation, known as long COVID, although the underlying causes remain unclear. It has been increasingly acknowledged that excessive NETosis and NET generation contribute to further pathophysiological abnormalities following SARS-CoV-2 infection. This review provides an updated overview of the role of NETosis in autoimmune diseases, but also the relationship between COVID-19 and long COVID with autoimmunity (e.g., latent and overt autoimmunity, molecular mimicry, epitope spreading) and NETosis (e.g., immune responses, NET markers). Finally, we discuss potential therapeutic strategies targeting dysregulated NETosis to mitigate the severe complications of COVID-19 and long COVID.

Targeting the SARS-CoV-2 reservoir in long COVID

There are no approved treatments for post-COVID-19 condition (also known as long COVID), a debilitating disease state following SARS-CoV-2 infection that is estimated to affect tens of millions of people. A growing body of evidence shows that SARS-CoV-2 can persist for months or years following COVID-19 in a subset of individuals, with this reservoir potentially driving long-COVID symptoms or sequelae. There is, therefore, an urgent need for clinical trials targeting persistent SARS-CoV-2, and several trials of antivirals or monoclonal antibodies for long COVID are underway. However, because mechanisms of SARS-CoV-2 persistence are not yet fully understood, such studies require important considerations related to the mechanism of action of candidate therapeutics, participant selection, duration of treatment, standardisation of reservoir-associated biomarkers and measurables, optimal outcome assessments, and potential combination approaches. In addition, patient subgroups might respond to some interventions or combinations of interventions, making post-hoc analyses crucial. Here, we outline these and other key considerations, with the goal of informing the design, implementation, and interpretation of trials in this rapidly growing field. Our recommendations are informed by knowledge gained from trials targeting the HIV reservoir, hepatitis C, and other RNA viruses, as well as precision oncology, which share many of the same hurdles facing long-COVID trials.

The PAX LC Trial: A Decentralized, Phase 2, Randomized, Double-Blind Study of Nirmatrelvir/Ritonavir Compared with Placebo/Ritonavir for Long COVID

BACKGROUND

Individuals with long COVID lack evidence-based treatments and have difficulty participating in traditional site-based trials. Our digital, decentralized trial investigates the efficacy and safety of nirmatrelvir/ritonavir, targeting viral persistence as a potential cause of long COVID.

METHODS

The PAX LC trial (NCT05668091) is a Phase 2, 1:1 randomized, double-blind, superiority, placebo-controlled trial in 100 community-dwelling, highly symptomatic adult participants with long COVID residing in the 48 contiguous US states to determine the efficacy, safety, and tolerability of 15 days of nirmatrelvir/ritonavir compared with placebo/ritonavir. Participants are recruited via patient groups, cultural ambassadors, and social media platforms. Medical records are reviewed through a platform facilitating participant-mediated data acquisition from electronic health records nationwide. During the drug treatment, participants complete daily digital diaries using a web-based application. Blood draws for eligibility and safety assessments are conducted at or near participants' homes. The study drug is shipped directly to participants' homes. The primary endpoint is the PROMIS-29 Physical Health Summary Score difference between baseline and Day 28, evaluated by a mixed model repeated measure analysis. Secondary endpoints include PROMIS-29 (Mental Health Summary Score and all items), Modified GSQ-30 with supplemental symptoms questionnaire, COVID Core Outcome Measures for Recovery, EQ-5D-5L (Utility Score and all items), PGIS 1 and 2, PGIC 1 and 2, and healthcare utilization. The trial incorporates immunophenotyping to identify long COVID biomarkers and treatment responders.

CONCLUSION

The PAX LC trial uses a novel decentralized design and a participant-centric approach to test a 15-day regimen of nirmatrelvir/ritonavir for long COVID.

Critical appraisal of: "expression of SARS-CoV-2 spike protein in cerebral arteries: implications for hemorrhagic stroke post-mRNA vaccination"

This correspondence offers a critical appraisal of the study by Ota et al. on the expression of SARS-CoV-2 spike protein in cerebral arteries following mRNA vaccination. While the original study contributes to understanding potential neurological sequelae post-vaccination, we identify several methodological limitations. Chief concerns include the absence of a control group, reliance on negative nucleocapsid staining to exclude prior infection, a small and unbalanced sample size, lack of lesionspecific tissue analysis, and unconfirmed RNA detection techniques. These issues collectively undermine causal inferences regarding vaccine-related spike protein persistence. We recommend methodological refinements for future studies, including matched controls, serial serological testing, tissue validation protocols, and robust subgroup stratification.

Multidisciplinary collaborative guidance on the assessment and treatment of patients with Long COVID: A compendium statement

BACKGROUND

In 2021, the American Academy of Physical Medicine and Rehabilitation established the Multi-Disciplinary Post-Acute Sequelae of SARS-CoV-2 Infection Collaborative to provide guidance from established Long COVID clinics for the evaluation and management of Long COVID. The collaborative previously published eight Long COVID consensus guidance statements using a primarily symptom-based approach. However, Long COVID symptoms most often do not occur in isolation.

AIMS

This compendium aims to equip clinicians with an efficient, up-to-date clinical resource for evaluating and managing adults experiencing Long COVID symptoms. The primary intended audience includes physiatrists, primary care physicians, and other clinicians who provide first-line assessment and management of Long COVID symptoms, especially in settings where subspecialty care is not readily available. This compendium provides a holistic framework for assessment and management, symptom-specific considerations, and updates on prevalence, health equity, disability considerations, pathophysiology, and emerging evidence regarding treatments under investigation. Because Long COVID closely resembles other infection-associated chronic conditions (IACCs) such as myalgic encephalomyelitis/chronic fatigue syndrome, the guidance in this compendium may also be helpful for clinicians managing these related conditions.

METHODS

Guidance in this compendium was developed by the collaborative's established modified Delphi approach. The collaborative is a multidisciplinary group whose members include physiatrists, primary care physicians, pulmonologists, cardiologists, psychiatrists, neuropsychologists, neurologists, occupational therapists, physical therapists, speech and language pathologists, patients, and government representatives. Over 40 Long COVID centers are represented in the collaborative.

RESULTS

Long COVID is defined by the National Academies of Sciences, Engineering, and Medicine as "an IACC that occurs after SARS-CoV-2 infection and is present for at least 3 months as a continuous, relapsing and remitting, or progressive disease state that affects one or more organ systems." The current global prevalence of Long COVID is estimated to be 6%. Higher prevalence has been identified among female gender, certain racial and ethnic groups, and individuals who live in nonurban areas. However, anyone can develop Long COVID after being infected with the SARS-CoV-2 virus. Long COVID can present as a wide variety of symptom clusters. The most common symptoms include exaggerated fatigue and diminished energy windows, postexertional malaise (PEM)/postexertional symptom exacerbation (PESE), cognitive impairment (brain fog), dysautonomia, pain/myalgias, and smell and taste alterations. Holistic assessment should include a traditional history, physical examination, and additional diagnostic testing, as indicated. A positive COVID-19 test during acute SARS-CoV-2 infection is not required to diagnose Long COVID, and currently, there is no single laboratory finding that is definitively diagnostic for confirming or ruling out the diagnosis of Long COVID. A basic laboratory assessment is recommended for all patients with possible Long COVID, and consideration for additional labs and diagnostic procedures is guided by the patient's specific symptoms. Current management strategies focus on symptom-based supportive care. Critical considerations include energy conservation strategies and addressing comorbidities and modifiable risk factors. Additionally, (1) it is essential to validate the patient's experience and provide reassurance that their symptoms are being taken seriously because many patients have had their symptoms dismissed by loved ones and clinicians; (2) physical activity recommendations must be carefully tailored to the patient's current activity tolerance because overly intense activity can trigger PEM/PESE and worsened muscle damage; and (3) treatment recommendations should be delivered with humility because there are many persistent unknowns related to Long COVID. To date, there are limited data to guide medication management specifically in the context of Long COVID. As such, medication use generally follows standard practice regarding indications and dosing, with extra attention to prioritize (1) patient preference via shared decision-making and (2) cautious use of medications that may improve some symptoms (eg, cognitive/attention impairment) but may worsen other symptoms (eg, PEM/PESE). Numerous clinical trials are investigating additional treatments. The return-to-work process for individuals with Long COVID can be challenging because symptoms can fluctuate, vary in nature, affect multiple functional areas (eg, physical and cognitive), and often manifest as an "invisible disability" that may not be readily acknowledged by employers or coworkers. Clinicians can help patients return to work by identifying suitable workplace accommodations and resources, providing necessary documentation, and recommending occupational or vocational therapy when needed. If these efforts are unsuccessful and work significantly worsens Long COVID symptoms or impedes recovery, applying for disability may be warranted. Long COVID is recognized as a potential disability under the Americans with Disabilities Act.

CONCLUSION

To contribute to the overall health and well-being for all patients, Long COVID care should be delivered in a holistic manner that acknowledges challenges faced by the patient and uncertainties in the field. For more detailed information on assessment and management of specific Long COVID symptoms, readers can reference the collaborative's symptom-specific consensus guidance statements.

Vaccination rate and symptoms of long COVID among dental teams in Germany

Although COVID-19 is no longer a global public health threat, its consequences persist, with long COVID affecting at least 10% of patients and manifesting in various organ systems. National and international health agencies promoted vaccination to enhance population immunity, prioritizing healthcare personnel due to their high occupational risk. In a previous study, we found that the risk of SARS-CoV-2 transmission among dental teams in Germany was not higher than in the general population. This follow-up investigation aims to assess the vaccination status and the prevalence and severity of long COVID symptoms among dental teams in Germany. As part of a follow-up investigation involving the original cohort, 267 team members from 186 German dental practices previously included in the initial study completed an online questionnaire. The questionnaire covered three topics: (1) vaccination status, (2) confirmed COVID-19 diagnosis, and (3) self-reported long COVID symptoms. One hundred and seventy-two dentists (64.4%), 74 dental assistants (27.7%) and 21 dental hygienists (7.9%) completed the questionnaire. In total, 245 participants (91.8%) were at least once vaccinated. A COVID-19 infection after January 1st 2021 was reported by 146 (54.7%) participants, of which 33 participants (22.6%) suffered from long COVID symptoms. Our results showed lower vaccination rates among dental auxiliary personnel compared to dentists (95.9% vs. 84.2%). Individuals with long COVID symptoms were more often dental assistants (48.5% vs. 29.2%) or dental hygienists (15.2% vs. 8.0%) than dentists (36.4% vs. 62.8%) compared to the group not reporting long COVID symptoms (p = 0.025). In addition, it is unlikely that dental healthcare personnel are more prone to experiencing more severe symptoms compared to the general population. Vaccination against SARS-CoV-2 is likely to help against symptoms of long COVID.

The immunopathogenesis of SARS-CoV-2 infection: Overview of lessons learned in the first 5 years

This review provides a broad overview of lessons learned in the five years since COVID-19 was identified. It is a bimodal disease, starting with an initially virus-driven phase, followed by resolution or ensuing inappropriate immune activation causing severe inflammation that is no longer strictly virus dependent. Humoral immunity is beneficial for preventing or attenuating the early stage, without benefit once the later stage begins. Neutralizing antibodies elicited by natural infection or vaccination are short-lived and highly vulnerable to viral sequence variation. By contrast, cellular immunity, particularly the CD8+ T cell arm, has a role in preventing or attenuating severe disease, is far less susceptible to viral variation, and is longer-lived than antibodies. Finally, an ill-defined phenomenon of prolonged symptoms after acute infection, termed "long COVID," is poorly understood but may involve various immunologic defects that are hyperactivating or immunosuppressive. Remaining issues include needing to better understand the immune dysregulation of severe disease to allow more tailored therapeutic interventions, developing antibody strategies that cope with the viral spike sequence variability, prolonging vaccine efficacy, and unraveling the mechanisms of long COVID to design therapeutic approaches.

A multidisciplinary review of long COVID to address the challenges in diagnosis and updated management guidelines

Long COVID has emerged as a significant challenge since the COVID-19 pandemic, which was declared as an outbreak in March 2020, marked by diverse symptoms and prolonged duration of disease. Defined by the WHO as symptoms persisting or emerging for at least two months post-SARS-CoV-2 infection without an alternative cause, its prevalence varies globally, with estimates of 10-20% in Europe, 7.3% in the USA, and 3.0% in the UK. The condition's etiology remains unclear, involving factors, such as renin-angiotensin system overactivation, persistent viral reservoirs, immune dysregulation, and autoantibodies. Reactivated viruses, like EBV and HSV-6, alongside epigenetic alterations, exacerbate mitochondrial dysfunction and energy imbalance. Emerging evidence links SARS-CoV-2 to chromatin and gut microbiome changes, further influencing long-term health impacts. Diagnosis of long COVID requires detailed systemic evaluation through medical history and physical examination. Management is highly individualized, focusing mainly on the patient's symptoms and affected systems. A multidisciplinary approach is essential, integrating diverse perspectives to address systemic manifestations, underlying mechanisms, and therapeutic strategies. Enhanced understanding of long COVID's pathophysiology and clinical features is critical to improving patient outcomes and quality of life. With a growing number of cases expected globally, advancing research and disseminating knowledge on long COVID remain vital for developing effective diagnostic and management frameworks, ultimately supporting better care for affected individuals.

Adult Outpatients with Long COVID Infected with SARS-CoV-2 Omicron Variant. Part 1: Oral Microbiota Alterations

BACKGROUND

Many individuals experience long COVID after SARS-CoV-2 infection. As microbiota can influence health, it may change with COVID-19. This study investigated differences in oral microbiota between COVID-19 patients with and without long COVID.

METHODS

Based on a prospective follow-up investigation, this nested case-control study evaluated the differences in oral microbiota in individuals with and without long COVID (Symptomatic and Asymptomatic groups), which were assessed by 16S rRNA sequencing on tongue coating samples. A predictive model was established using machine learning based on specific differential microbial communities.

RESULTS

One-hundred-and-eight patients were included (n=54 Symptomatic group). The Symptomatic group had higher Alpha diversity indices (observed_otus, Chao1, Shannon, and Simpson indices), differences in microbial composition (Beta diversity), and microbial dysbiosis with increased diversity and relative abundance of pathogenic bacteria. Marker bacteria (c__Campylobacterota, o__Coriobacteriales, o__Pseudomonadales, and o__Campylobacterales) were associated with long COVID by linear discriminant analysis effect size and receiver operating characteristic curves (AUC 0.821).

CONCLUSION

There were distinct variations in oral microbiota between COVID-19 patients with and without long COVID. Changes in oral microbiota may indicate long COVID.

Kidney Function Following COVID-19 in Children and Adolescents

Importance

It remains unclear whether children and adolescents with SARS-CoV-2 infection are at heightened risk for long-term kidney complications.

Objective

To investigate whether SARS-CoV-2 infection is associated with an increased risk of postacute kidney outcomes among pediatric patients, including those with preexisting kidney disease or acute kidney injury (AKI).

Design, Setting, and Participants

This retrospective cohort study used data from 19 health institutions in the National Institutes of Health Researching COVID to Enhance Recovery (RECOVER) initiative from March 1, 2020, to May 1, 2023 (follow-up ≤2 years completed December 1, 2024; index date cutoff, December 1, 2022). Participants included children and adolescents (aged <21 years) with at least 1 baseline visit (24 months to 7 days before the index date) and at least 1 follow-up visit (28 to 179 days after the index date).

Exposures

SARS-CoV-2 infection, determined by positive laboratory test results (polymerase chain reaction, antigen, or serologic) or relevant clinical diagnoses. A comparison group included children with documented negative test results and no history of SARS-CoV-2 infection.

Main Outcomes and Measures

Outcomes included new-onset chronic kidney disease (CKD) stage 2 or higher or CKD stage 3 or higher among those without preexisting CKD; composite kidney events (≥50% decline in estimated glomerular filtration rate [eGFR], eGFR ≤15 mL/min/1.73 m2, dialysis, transplant, or end-stage kidney disease diagnosis), and at least 30%, 40%, or 50% eGFR decline among those with preexisting CKD or acute-phase AKI. Hazard ratios (HRs) were estimated using Cox proportional hazards regression models with propensity score stratification.

Results

Among 1 900 146 pediatric patients (487 378 with and 1 412 768 without COVID-19), 969 937 (51.0%) were male, the mean (SD) age was 8.2 (6.2) years, and a range of comorbidities was represented. SARS-CoV-2 infection was associated with higher risk of new-onset CKD stage 2 or higher (HR, 1.17; 95% CI, 1.12-1.22) and CKD stage 3 or higher (HR, 1.35; 95% CI, 1.13-1.62). In those with preexisting CKD, COVID-19 was associated with an increased risk of composite kidney events (HR, 1.15; 95% CI, 1.04-1.27) at 28 to 179 days. Children with acute-phase AKI had elevated HRs (1.29; 95% CI, 1.21-1.38) at 90 to 179 days for composite outcomes.

Conclusions and Relevance

In this large US cohort study of children and adolescents, SARS-CoV-2 infection was associated with a higher risk of adverse postacute kidney outcomes, particularly among those with preexisting CKD or AKI, suggesting the need for vigilant long-term monitoring.

Long COVID: Pathophysiology, current concepts, and future directions

Long COVID, an umbrella term referring to a variety of symptoms and clinical presentations that emerges in a subset of patients after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, has a significant effect on quality of life and places a substantial burden on health care systems worldwide, straining financial and human resources. The pathophysiology of long COVID remains incompletely understood, though several hypotheses have been proposed to explain different aspects of this complex condition. SARS-CoV-2 persistence, direct organ damage, innate and adaptive immune system perturbation, autoimmunity, latent virus reactivation, endothelial dysfunction, and microbiome disturbances are among the most relevant avenues for elucidating the evolution, complexity, and mechanisms of long COVID. Active investigation regarding potential biomarkers for long COVID and its associated disease endotypes highlights the role of inflammatory mediators, immunophenotyping, and multiomics approaches. Further advances in understanding long COVID are needed to inform current and future therapeutics.

Immunogenicity and safety study of a single dose of SpikoGen® vaccine as a heterologous or homologous intramuscular booster following a primary course of mRNA, adenoviral vector or recombinant protein COVID-19 vaccine in ambulatory adults

BACKGROUND

SpikoGen® is a subunit recombinant Wuhan spike protein produced in insect cells and formulated with Advax-CpG55.2™ adjuvant. It is approved for adult and pediatric use in the Middle East. This study tested the safety and immunogenicity of SpikoGen® as a 3rd, 4th or 5th dose booster following a primary immunisation course of mRNA, adenovirus or SpikoGen® vaccine.

METHODS

The trial recruited participants who had received a previous doses of COVID-19 vaccine more than 3 months prior. Each received a single intramuscular booster dose of SpikoGen® vaccine. Spike and nuclear protein antibody levels were measured at 1 and 3 months post-booster, together with collection of data on SARS-CoV-2 breakthrough infections and symptoms of long COVID.

RESULTS

One-month post-booster, anti-spike IgG, sVNT, and pVNT levels were increased in all groups and there was ∼4-fold neutralizing antibodies against the heterologous Omicron BA.2 and BA.4/5 strains. The SpikoGen®-prime group had the highest levels of anti-spike IgG3, consistent with the Advax-CpG adjuvant driving IgG3 induction. There was no effect of age on the vaccine response. The booster dose was well tolerated with no vaccine-associated serious adverse events. Nine participants (9/74, 12.2 %) had a breakthrough SARS-CoV-2 infection between 2 weeks and 3 months post-booster. No long COVID was observed after breakthrough infections. Breakthrough infection was negatively correlated with baseline anti-nuclear protein IgG seropositivity.

CONCLUSION

A single SpikoGen® booster was well tolerated and stimulated cross- antibody responses against Omicron variants, regardless of the primary vaccine course received. With SARS-CoV-2 variants continuing to evolve, ongoing research is needed into optimum booster strategies.

CLINICALTRIALS

gov registration. NCT05542862.

Aptamer Paper-Based Fluorescent Sensor for Determination of SARS-CoV-2 Spike Protein

Point-of-care (POC) antigen detection plays a crucial role in curbing the spread of viruses. Paper-based fluorescence aptasensors are expected to offer a low-cost tool to meet the needs of decentralized POC diagnosis. Herein, we report on a fluorescent paper-based sensing system for detecting the SARS-CoV-2 spike protein. The sensing system was constructed by loading multi-layer Nb2C MXene nano-quenchers and carbon-dot-labeled aptamer (G-CDs@Apt) probes onto a mixed cellulose ester (MCE) paper substrate. On the Nb2C MXene/G-CDs@Apt sensing paper, abundant G-CDs@Apt probes were attached to the multilayer MXene nano-quenchers and kept in a fluorescence-off state, while recognition of the target detached the G-CDs@Apt probes formed the nano--quenchers, resulting in fluorescence recovery of the sensing paper. The developed paper-based sensor performed well in the one-step detection of the SARS-CoV-2 S1 protein with a detection limit of 0.067 ng/mL (0.335 pg/test). The assay exhibited good selectivity and anti-interference in the detection of the SARS-CoV-2 S1 protein in artificial saliva. Moreover, the paper-based aptasensor was successfully used to detect the SARS-CoV-2 S1 protein in actual environmental samples with recoveries of 90.87-100.55% and relative standard deviations of 1.52-3.41%. The proposed technology provides a cost-effective alternative to traditional antibody test strips for a wide range of POC diagnostic applications.

A review of post COVID syndrome pathophysiology, clinical presentation and management in children and young people

Post Covid Syndrome (PCS) is a complex multi-system disorder with a spectrum of presentations. Severity ranges from mild to very severe with variable duration of illness and recovery. This paper discusses the difficulties defining and describing PCS. We review the current understanding of PCS, epidemiology, and predisposing factors. We consider potential mechanisms including viral persistence, clotting dysfunction and immunity. We review presentation and diagnosis and finally consider management strategies including addressing symptom burden, rehabilitation, and novel therapies.

Long COVID - a critical disruption of cholinergic neurotransmission?

BACKGROUND

Following the COVID-19 pandemic, there are many chronically ill Long COVID (LC) patients with different symptoms of varying degrees of severity. The pathological pathways of LC remain unclear until recently and make identification of path mechanisms and exploration of therapeutic options an urgent challenge. There is an apparent relationship between LC symptoms and impaired cholinergic neurotransmission.

METHODS

This paper reviews the current literature on the effects of blocked nicotinic acetylcholine receptors (nAChRs) on the main affected organ and cell systems and contrasts this with the unblocking effects of the alkaloid nicotine. In addition, mechanisms are presented that could explain the previously unexplained phenomenon of post-vaccination syndrome (PVS). The fact that not only SARS-CoV-2 but numerous other viruses can bind to nAChRs is discussed under the assumption that numerous other post-viral diseases and autoimmune diseases (ADs) may also be due to impaired cholinergic transmission. We also present a case report that demonstrates changes in cholinergic transmission, specifically, the availability of α4β2 nAChRs by using (-)-[18F]Flubatine whole-body positron emission tomography (PET) imaging of cholinergic dysfunction in a LC patient along with a significant neurological improvement before and after low-dose transcutaneous nicotine (LDTN) administration. Lastly, a descriptive analysis and evaluation were conducted on the results of a survey involving 231 users of LDTN.

RESULTS

A substantial body of research has emerged that offers a compelling explanation for the phenomenon of LC, suggesting that it can be plausibly explained because of impaired nAChR function in the human body. Following a ten-day course of transcutaneous nicotine administration, no enduring neuropathological manifestations were observed in the patient. This observation was accompanied by a significant increase in the number of free ligand binding sites (LBS) of nAChRs, as determined by (-)-[18F]Flubatine PET imaging. The analysis of the survey shows that the majority of patients (73.5%) report a significant improvement in the symptoms of their LC/MEF/CFS disease as a result of LDTN.

CONCLUSIONS

In conclusion, based on current knowledge, LDTN appears to be a promising and safe procedure to relieve LC symptoms with no expected long-term harm.

Individualized Algorithm-Based Intermittent Hypoxia Improves Quality of Life in Patients Suffering from Long-Term Sequelae After COVID-19 Infection

Background/Objectives: Post-COVID-19 condition (PCC), also known as long COVID, has emerged as a recognized syndrome affecting millions of people worldwide, significantly impairing their quality of life. Currently, no effective therapeutic options are available to manage this condition. The objective of the present study was to evaluate the long-term effects of personalized, algorithm-based intermittent hypoxia-hyperoxia conditioning (IHHC) on quality of life and pain in patients with PCC. Methods: This open-label cohort study included 199 PCC patients, aged 11-87 years (female-to-male ratio: 67:33) and experiencing moderate-to-severe fatigue, between 1 January 2020 and 31 December 2023. Each patient received an algorithm-based treatment plan tailored to their demographics, symptom duration, and baseline pain (NRS) and quality of life (SF-36) scores. Patients received an average of six treatment sessions (range: 2-21), each consisting of intermittent hypoxic-hyperoxic cycles, with hypoxia (9-13% O2) lasting 3-8 min and hyperoxia (34-36% O2) lasting 1-3 min. The primary outcomes were changes in the NRS and SF-36 scores at the 6-week and 6-month follow-ups. Results: At the 6-week follow-up after treatment initiation, the SF-36 scores increased by 102 points (p < 0.001, 95% CI: 78.4-127), and this improvement persisted at the 6-month follow-up (Δ106, p < 0.001, 95% CI: 57.0-154). Pain was reduced by 28-32% at both follow-up time points, exceeding the clinically relevant threshold. Health transition scores indicated a patient-perceived improvement in health status. Conclusions: In this study, a personalized, algorithm-based IHHC alleviated pain and improved quality of life in patients suffering from persistent long-term sequelae after COVID-19 infection. The effects were sustained for up to six months. Further research is warranted to elucidate the mechanisms underlying IHHC's therapeutic effects in this patient population.

Interventions for Long COVID: A Narrative Review

Long COVID continues to impose a significant burden on COVID-19 survivors, presenting with diverse symptoms and clinical uncertainty. This review synthesized evidence from 97 studies, including 26 randomized controlled trials and 15 non-randomized comparative studies, which explored the effectiveness, comparative effectiveness, and potential risks of proposed interventions for managing common long COVID symptoms: fatigue, neurocognitive symptoms, anxiety, depression, and sleep issues. Our comprehensive analysis, encompassing English-language articles, gray literature, and feedback from 14 Key Informants (i.e., patients, caregivers, clinicians, payors, and researchers), reveals a persistently weak body of evidence, characterized by high imprecision and considerable uncertainty regarding the benefits and harms of the interventions. The studies examined a wide array of treatment categories, including multi-component rehabilitation, supplements, complementary treatments, prescription medications, and the COVID-19 vaccine. Key informants emphasized the critical need for establishing robust diagnostic criteria and utilizing functional outcomes while also highlighting significant barriers to care, including dismissive attitudes from healthcare providers, inadequate insurance coverage, and restricted access to specialty care. Given the evolving definitions of long COVID and the variable mechanisms of its management, our findings underscore the pressing need for further rigorous research to refine and validate effective treatment protocols. Until more definitive evidence is available, both clinicians and patients face substantial uncertainty in treatment decisions, with many resorting to self-treatment using costly and potentially ineffective options.

Identification of a multi-omics factor predictive of long COVID in the IMPACC study

Following SARS-CoV-2 infection, ∼10-35% of COVID-19 patients experience long COVID (LC), in which often debilitating symptoms persist for at least three months. Elucidating the biologic underpinnings of LC could identify therapeutic opportunities. We utilized machine learning methods on biologic analytes and patient reported outcome surveys provided over 12 months after hospital discharge from >500 hospitalized COVID-19 patients in the IMPACC cohort to identify a multi-omics "recovery factor". IMPACC participants who experienced LC had lower recovery factor scores compared to participants without LC. Biologic characterization revealed increased levels of plasma proteins associated with inflammation, elevated transcriptional signatures of heme metabolism, and decreased androgenic steroids in LC patients. The recovery factor was also associated with altered circulating immune cell frequencies. Notably, recovery factor scores were predictive of LC occurrence in patients as early as hospital admission, irrespective of acute disease severity. Thus, the recovery factor identifies patients at risk of LC early after SARS-CoV-2 infection and reveals LC biomarkers and potential treatment targets.

Preferential apical infection of Caco-2 intestinal cell monolayers by SARS-CoV-2 is associated with damage to cellular barrier integrity: Implications for the pathophysiology of COVID-19

SARS-CoV-2 can infect different organs, including the intestine. In an in vitro model of Caco-2 intestinal cell line, we previously found that SARS-CoV-2 modulates the ACE2 receptor expression and affects the expression of molecules involved in intercellular junctions. To further explore the possibility that the intestinal epithelium can serve as an alternative infection route for SARS-CoV-2, we used a model of polarized monolayers of Caco-2 cells (or co-cultures of two intestinal cell lines: Caco-2 and HT29) grown on the polycarbonate membrane of Transwell inserts, inoculated with the virus either in the upper or lower chamber of culture to determine the tropism of the virus for the apical or basolateral pole of these cells. In both polarized Caco-2 cell monolayers and co-culture Caco-2/HT29 cell monolayer, apical SARS-CoV-2 inoculation was found to be much more effective in establishing infection than basolateral inoculation. In addition, apical SARS-CoV-2 infection triggers monolayer degeneration, as shown by histological examination, measurement of trans-epithelial electrical resistance, and cell adhesion molecule expression. During apical infection, the infectious viruses reach the lower chamber, suggesting either a transcytosis mechanism from the apical side to the basolateral side of cells, a paracellular trafficking of the virus after damage to intercellular junctions in the epithelial barrier, or both. Taken together, these data indicate a preferential tropism of SARS-CoV-2 for the apical pole of the human intestinal tract and suggest that infection via the intestinal lumen leads to a systemic infection.

Serum Spike Protein Persistence Post COVID Is Not Associated with ME/CFS

Background/Objectives: According to the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC), an estimated 3-6% of people suffer from post-COVID condition or syndrome (PCS). A subset meets the diagnostic criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Studies have reported that SARS-CoV-2 proteins or RNA can persist after acute infection in serum or tissues, but their role in PCS is unclear. Methods: Here, SARS-CoV-2 spike protein was analyzed in the serum of 121 PCS patients with predominant fatigue and exertional intolerance, of whom 72 met diagnostic criteria for ME/CFS, 37 post-COVID recovered healthy controls, and 32 pre-pandemic healthy controls. Results: Spike protein was detected in the serum of 11% of recovered controls, 2% of PCS patients, and 14% of ME/CFS patients between 4 and 31 months after SARS-CoV-2 infection, but not in pre-pandemic samples. The occurrence and concentration of spike protein did not correlate with infection or vaccination timepoints. In ME/CFS patients, spike protein presence was not associated with the severity of symptoms or functional disability. In 5 out of 22 patients who under-went immunoglobulin depletion, spike protein levels were reduced or undetectable after treatment, indicating binding to immunoglobulins. Conclusions: In summary, this study identified serum spike protein in a subset of patients but found no association with ME/CFS.

Serotonergic psychedelics as potential therapeutics for post-COVID-19 syndrome (or Long COVID): A comprehensive review

RATIONALE

In our ongoing battle against the coronavirus 2019 (COVID-19) pandemic, a major challenge is the enduring symptoms that continue after acute infection. Also known as Long COVID, post-COVID-19 syndrome (PCS) often comes with debilitating symptoms like fatigue, disordered sleep, olfactory dysfunction, and cognitive issues ("brain fog"). Currently, there are no approved treatments for PCS. Recent research has uncovered that the severity of PCS is inversely linked to circulating serotonin levels, highlighting the potential of serotonin-modulating therapeutics for PCS. Therefore, we propose that serotonergic psychedelics, acting mainly via the 5-HT2A serotonin receptor, hold promise for treating PCS.

OBJECTIVES

Our review aims to elucidate potential mechanisms by which serotonergic psychedelics may alleviate the symptoms of PCS.

RESULTS

Potential mechanisms through which serotonergic psychedelics may alleviate PCS symptoms are discussed, with emphasis on their effects on inflammation, neuroplasticity, and gastrointestinal function. Additionally, this review explores the potential of serotonergic psychedelics in mitigating endothelial dysfunction, a pivotal aspect of PCS pathophysiology implicated in organ dysfunction. This review also examines the potential role of serotonergic psychedelics in alleviating specific PCS symptoms, which include olfactory dysfunction, cognitive impairment, sleep disturbances, and mental health challenges.

CONCLUSIONS

Emerging evidence suggests that serotonergic psychedelics may alleviate PCS symptoms. However, further high-quality research is needed to thoroughly assess their safety and efficacy in treating patients with PCS.

Intra-host variability of SARS-CoV-2: Patterns, causes and impact on COVID-19

Intra-host viral variability is related to pathogenicity, persistence, drug resistance, and the emergence of new clades. This work reviews the large amount of data on SARS-CoV-2 intra-host variability accumulated to date, addressing known and potential implications in COVID-19 and the emergence of VOCs and lineage-defining mutations. Topics covered include the distribution of intra-host polymorphisms across the genome, the corresponding mutational signatures, their patterns of emergence and extinction throughout infection, and the processes governing their abundance, frequency, and type (synonymous, nonsynonymous, indels, nonsense). Besides, evidence is reviewed that the virus can replicate and mutate in isolation at different anatomical compartments, which may imply that what we have learned from respiratory samples could be part of a broader picture.

Association of systemic inflammation and long-term dysfunction in COVID-19 patients: A prospective cohort

COVID-19 has significant long-term impacts, including a chronic syndrome known as long-COVID, characterized by persistent symptoms post-recovery. The inflammatory response during acute infection is hypothesized to influence long-term outcomes. This study aimed to identify inflammatory biomarkers predictive of functional outcomes one year after hospital discharge. A prospective cohort study was conducted with 213 COVID-19 patients admitted to ICUs in Southern Brazil between June and November 2020. After exclusions and follow-ups, 109 patients were evaluated for one-year post-discharge. Plasma levels of Th1 (TNF-α, INF-γ, IL-12), Th2 (IL-4, IL-5, IL-6, IL-10, IL-13), and Th17 (IL-17, IL-22) cytokines were measured. Functional outcomes in psychiatric, cognitive, general health, and health perception domains were assessed. Statistical analyses included multivariate regression, regularized partial correlation network analysis, and K-means clustering. We demonstrate that plasma levels of various cytokines, along with demographic and clinical characteristics, can predict four distinct domains of functional outcomes one year following hospital discharge due to COVID-19 and that an hyperinflammatory phenotype was associated with the occurrence of a worse in psychiatric, general health, and health perception domains. The network analysis highlighted complex interconnections among immune markers and clinical variables, elucidating their roles in long-term health. These findings support using biomarkers for patient stratification and indicate potential targets for therapeutic interventions.

Viral Burden and Illness Severity During Acute SARS-CoV-2 Infection Predict Persistent Long COVID Symptoms

Background

Long COVID is a common complication of infection with severe acute respiratory syndrome coronavirus 2, but the prevalence and predictors of the condition remain poorly characterized.

Methods

We prospectively studied adults (≥18 years) with acute coronavirus disease 2019 (COVID-19) presenting to an urban safety net hospital and associated clinics between July 2020 and December 2022. Logistic regression models were used to evaluate the association between baseline demographic, clinical, and laboratory characteristics with long COVID status, defined as symptoms persisting at least 9 months after acute disease. Among unrecovered participants, we describe the prevalence of individual symptoms.

Results

We enrolled 222 participants, 162 (73%) of whom had known recovery status by 9 months. Median age was 54 years, half (55%) were female, and the majority of participants (78%) had at least 1 comorbidity at the time of COVID-19 diagnosis. Based on acute illness characteristics, the adjusted odds ratio for long COVID was 3.0 (95% confidence interval [CI], 1.1-8.0) among those with detectable nucleocapsid antigen and 3.6 (95% CI, 1.2-11) for those who required supplemental oxygen. Of the 41% of participants with symptoms persisting at least 9 months, central nervous system and psychological symptoms were most commonly reported, with 57% reporting functional limitations due to their persistent symptoms.

Conclusions

The strong association with initial disease suggests a decreasing prevalence of long COVID as acute illnesses become milder. However, many contemporary patients still experience high viral burden with extended viral replication, even after vaccination. Our findings highlight the importance of properly characterizing long COVID as viral evolution shifts acute disease presentation.

Cerebromicrovascular mechanisms contributing to long COVID: implications for neurocognitive health

Long COVID (also known as post-acute sequelae of SARS-CoV-2 infection [PASC] or post-COVID syndrome) is characterized by persistent symptoms that extend beyond the acute phase of SARS-CoV-2 infection, affecting approximately 10% to over 30% of those infected. It presents a significant clinical challenge, notably due to pronounced neurocognitive symptoms such as brain fog. The mechanisms underlying these effects are multifactorial, with mounting evidence pointing to a central role of cerebromicrovascular dysfunction. This review investigates key pathophysiological mechanisms contributing to cerebrovascular dysfunction in long COVID and their impacts on brain health. We discuss how endothelial tropism of SARS-CoV-2 and direct vascular infection trigger endothelial dysfunction, impaired neurovascular coupling, and blood-brain barrier disruption, resulting in compromised cerebral perfusion. Furthermore, the infection appears to induce mitochondrial dysfunction, enhancing oxidative stress and inflammation within cerebral endothelial cells. Autoantibody formation following infection also potentially exacerbates neurovascular injury, contributing to chronic vascular inflammation and ongoing blood-brain barrier compromise. These factors collectively contribute to the emergence of white matter hyperintensities, promote amyloid pathology, and may accelerate neurodegenerative processes, including Alzheimer's disease. This review also emphasizes the critical role of advanced imaging techniques in assessing cerebromicrovascular health and the need for targeted interventions to address these cerebrovascular complications. A deeper understanding of the cerebrovascular mechanisms of long COVID is essential to advance targeted treatments and mitigate its long-term neurocognitive consequences.

Prevalence and clinical relevance of viraemia in viral respiratory tract infections: a systematic review

In this Review, we analysed the prevalence of viraemia during infection with SARS-CoV-2 and other relevant respiratory viruses, including other human coronaviruses such as MERS-CoV and SARS-CoV, adenovirus, human metapneumovirus, human rhinovirus/enterovirus, influenza A and B virus, parainfluenza virus, and respiratory syncytial virus. First, a preliminary systematic search was conducted to identify articles published before May 23, 2024 that reported on viraemia during infection with respiratory viruses. The articles were then analysed for relevant terms to identify the prevalence of viraemia, its association with the disease severity and long-term consequences, and host responses. A total of 202 articles were included in the final study. The pooled prevalence of viraemia was 34% for SARS-CoV-2 and between 6% and 65% for other viruses. Association of viraemia with disease severity was extensively reported for SARS-CoV-2 and also for SARS-CoV, MERS-CoV, adenoviruses, rhinoviruses, respiratory syncytial virus, and influenza A(H1N1)pdm09 (albeit with low evidence). SARS-CoV-2 viraemia was linked to memory problems and worsened quality of life. Viraemia was associated with signatures denoting dysregulated host responses. In conclusion, the high prevalence of viraemia and its association with disease severity suggests that viraemia could be a relevant pathophysiological event with important translational implications in respiratory viral infections.

Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

A considerable number of patients who contracted SARS-CoV-2 are affected by persistent multi-systemic symptoms, referred to as Post-COVID Condition (PCC). Post-exertional malaise (PEM) has been recognized as one of the most frequent manifestations of PCC and is a diagnostic criterion of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Yet, its underlying pathomechanisms remain poorly elucidated.

PURPOSE AND METHODS

In this review, we describe current evidence indicating that key pathophysiological features of PCC and ME/CFS are involved in physical activity-induced PEM.

RESULTS

Upon physical activity, affected patients exhibit a reduced systemic oxygen extraction and oxidative phosphorylation capacity. Accumulating evidence suggests that these are mediated by dysfunctions in mitochondrial capacities and microcirculation that are maintained by latent immune activation, conjointly impairing peripheral bioenergetics. Aggravating deficits in tissue perfusion and oxygen utilization during activities cause exertional intolerance that are frequently accompanied by tachycardia, dyspnea, early cessation of activity and elicit downstream metabolic effects. The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.

Animal Models of Non-Respiratory, Post-Acute Sequelae of COVID-19

Post-acute sequelae of COVID-19 (PASC) are a diverse set of symptoms and syndromes driven by dysfunction of multiple organ systems that can persist for years and negatively impact the quality of life for millions of individuals. We currently lack specific therapeutics for patients with PASC, due in part to an incomplete understanding of its pathogenesis, especially for non-pulmonary sequelae. Here, we discuss three animal models that have been utilized to investigate PASC: non-human primates (NHPs), hamsters, and mice. We focus on neurological, gastrointestinal, and cardiovascular PASC and highlight advances in mechanistic insight that have been made using these animal models, as well as discussing the sequelae that warrant continued and intensive research.

Effect of immunoadsorption on clinical presentation and immune alterations in COVID-19-induced and/or aggravated ME/CFS

Autoantibodies (AABs) are currently being investigated as causative or aggravating factors during post-COVID. In this study, we analyze the effect of immunoadsorption therapy on symptom improvement and the relationship with immunological parameters in post-COVID patients exhibiting symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) induced or aggravated by an SARS-CoV-2 infection. This observational study includes 12 post-COVID patients exhibiting a predominance of ME/CFS symptoms alongside increased concentrations of autonomic nervous system receptor (ANSR) autoantibodies and neurological impairments. We found that following immunoadsorption therapy, the ANSR AABs were nearly eliminated from the patients' blood. The removal of immunoglobulin G antibodies was accompanied by a decrease of pro-inflammatory cytokines including interleukin (IL)-4, IL-2, IL-1β, tumor necrosis factor, and IL-17A serum levels, and a significant reduction of soluble spike protein. Notably, a strong positive correlation between pro-inflammatory cytokines and ASNR-AABs β1, β2, M3, and M4 was observed in spike protein-positive patients, whereas no such correlation was evident in spike protein-negative patients. Thirty days post-immunoadsorption therapy, patients exhibited notable improvement in neuropsychological function and a modest but statistically significant amelioration of hand grip strength was observed. However, neither self-reported symptoms nor scores on ME/CFS questionnaires showed a significant improvement and a rebound of the removed proteins occurring within a month.

Reduced Presence of SARS-CoV-2 microRNA-like Small RNA in the Serum of Patients with Post-Acute Sequelae SARS-CoV-2 Infection

The mechanisms underlying post-acute sequelae of SARS-CoV-2 infection (PASC) are a topic of debate. This study examined the presence of SARS-CoV-2 microRNA (miRNA)-like small RNAs in extracellular fluids and their potential link to PASC by using a quantitative stem-loop RT-PCR MiRNA assay. Initially, it was demonstrated that three previously identified SARS-CoV-2 miRNA-like small RNAs, specifically svRNA 1 and 2 and miR-07a, were significantly expressed in infected cells in vitro and released into the supernatant following infection by different SARS-CoV-2 variants. Then, the expression of three SARS-CoV-2 small RNAs was studied in both nasopharyngeal swabs (NPS) and sera from 24 patients at their initial COVID-19 diagnosis (T0) and in sera collected 91 to 193 days post-diagnosis (T1). Notably, 11 out of 24 patients (46%) reported PASC consequences. All NPS samples showed SARS-CoV-2 small RNA expression with an altered cytokine network during acute infection, but it did not correlate with PASC outcomes. Serum samples had similar small RNA statuses, though PASC patients, notably at T1, but not at T0, displayed reduced overall positivity compared to those without PASC. The host target expression of SARS-CoV-2 small RNAs was not significantly different between groups. This suggests a need for further research into SARS-CoV-2 small RNA and its role in viral behavior and PASC consequences.

Identification of an immunological signature of long COVID syndrome

Introduction

Acute COVID-19 infection causes significant alterations in the innate and adaptive immune systems. While most individuals recover naturally, some develop long COVID (LC) syndrome, marked by persistent or new symptoms weeks to months after SARS-CoV-2 infection. Despite its prevalence, there are no clinical tests to distinguish LC patients from those fully recovered. Understanding the immunological basis of LC is essential for improving diagnostic and treatment approaches.

Methods

We performed deep immunophenotyping and functional assays to examine the immunological profiles of LC patients, individuals with active COVID-19, recovered patients, and healthy donors. This analysis assessed both innate and adaptive immune features, identifying potential biomarkers for LC syndrome. A Binomial Generalized Linear Model (BGLM) was used to pinpoint immune features characterizing LC.

Results

COVID-19 patients exhibited depletion of innate immune cell subsets, including plasmacytoid and conventional dendritic cells, classical, non-classical, and intermediate monocytes, and monocyte-derived inflammatory dendritic cells. Elevated basal inflammation was observed in COVID-19 patients compared to LC patients, whose immune profiles were closer to those of healthy donors and recovered individuals. However, LC patients displayed persistent immune alterations, including reduced T cell subsets (CD4, CD8, Tregs) and switched memory B cells, similar to COVID-19 patients. Through BGLM, a unique adaptive immune signature for LC was identified, featuring memory CD8 and gd T cells with low proliferative capacity and diminished expression of activation and homing receptors.

Discussion

The findings highlight a unique immunological signature associated with LC syndrome, characterized by persistent adaptive immune dysregulation. While LC patients displayed recovery in innate immune profiles comparable to healthy and Recovered individuals, deficits in T cell and memory B cell populations were evident, differentiating LC from full recovery. These findings provide insights into LC pathogenesis and may support the development of diagnostic tools and targeted therapies.

Impact of extended-course oral nirmatrelvir/ritonavir in established Long COVID: a case series

BACKGROUND

Prior case series suggest that a 5-day course of oral Paxlovid (nirmatrelvir/ritonavir) benefits some people with Long COVID, within and/or outside of the context of an acute reinfection. To the best of our knowledge, there have been no prior case series of people with Long COVID who have attempted longer courses of nirmatrelvir/ritonavir.

METHODS

We documented a case series of 13 individuals with Long COVID who initiated extended courses (>5 days; range: 7.5-30 days) of oral nirmatrelvir/ritonavir outside (n = 11) of and within (n = 2) the context of an acute SARS-CoV-2 infection. Participants reported on symptoms and health experiences before, during, and after their use of nirmatrelvir/ritonavir.

RESULTS

Among those who take an extended course of nirmatrelvir/ritonavir outside of the context of an acute infection, some experience a meaningful reduction in symptoms, although not all benefits persist. Others experience no effect on symptoms. One participant stopped early due to intense stomach pain. For the two participants who took an extended course of nirmatrelvir/ritonavir within the context of an acute reinfection, both report eventually returning to their pre-re-infection baseline.

CONCLUSIONS

Extended courses of nirmatrelvir/ritonavir may have meaningful benefits for some people with Long COVID but not others. We encourage researchers to study how and why nirmatrelvir/ritonavir benefits some and what course length is most effective, with the goal of informing clinical recommendations for using nirmatrelvir/ritonavir and/or other antivirals as a potential treatment for Long COVID.

Mitochondria and the Repurposing of Diabetes Drugs for Off-Label Health Benefits

This review describes our current understanding of the role of the mitochondria in the repurposing of the anti-diabetes drugs metformin, gliclazide, GLP-1 receptor agonists, and SGLT2 inhibitors for additional clinical benefits regarding unhealthy aging, long COVID, mental neurogenerative disorders, and obesity. Metformin, the most prominent of these diabetes drugs, has been called the "Drug of Miracles and Wonders," as clinical trials have found it to be beneficial for human patients suffering from these maladies. To promote viral replication in all infected human cells, SARS-CoV-2 stimulates the infected liver cells to produce glucose and to export it into the blood stream, which can cause diabetes in long COVID patients, and metformin, which reduces the levels of glucose in the blood, was shown to cut the incidence rate of long COVID in half for all patients recovering from SARS-CoV-2. Metformin leads to the phosphorylation of the AMP-activated protein kinase AMPK, which accelerates the import of glucose into cells via the glucose transporter GLUT4 and switches the cells to the starvation mode, counteracting the virus. Diabetes drugs also stimulate the unfolded protein response and thus mitophagy, which is beneficial for healthy aging and mental health. Diabetes drugs were also found to mimic exercise and help to reduce body weight.

Potential Biomarkers for Predicting the Risk of Developing Into Long COVID After COVID-19 Infection

BACKGROUND

Long COVID, a heterogeneous condition characterized by a range of physical and neuropsychiatric presentations, can be presented with a proportion of COVID-19-infected individuals.

METHODS

Transcriptomic data sets of those within gene expression profiles of COVID-19, long COVID, and healthy controls were retrieved from the GEO database. Differentially expressed genes (DEGs) falling under COVID-19 and long COVID were identified with R packages, and contemporaneously conducted module detection was performed with the Modular Pharmacology Platform (http://112.86.129.72:48081/). The integration of both DEGs and differentially expressed module-genes (DEMGs) regarding long COVID and COVID-19 was intersected by following Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA).

RESULTS

There were 11 and 62 differentially expressed modules, 1837 and 179 DEGs, as well as 103 and 508 DEMGs acquiring identified for both COVID-19 and long COVID, notably enriched in the immune-correlated signaling pathways. The immune infiltrating cells of long COVID and COVID-19 were comparatively and respectively assessed via CIBERSORT, ssGSEA, and xCell algorithms. Subsequently, the screening of hub genes involved employing the SVM-RFE, RF, XGBoost algorithms, and logistic regression analysis. Among the 67 candidate genes were processed with machine learning algorithms and logistic regression, a subgroup consisting of CEP55, CDCA2, MELK, and DEPDC1B, was at last identified as potential biomarkers for predicting the risk of the progression into long COVID after COVID-19 infections. The predicting performance of the potential biomarkers was quantified with a ROC value of 0.8762542, which proved the combination of potential biomarkers provided the highest performance.

CONCLUSIONS

In summary, we identified a subgroup of potential biomarkers for predicting the risk of the progression into long COVID after COVID-19 infection, which could be partly elucidation of the associated molecular mechanisms for long COVID.

Persistent symptoms and clinical findings in adults with post-acute sequelae of COVID-19/post-COVID-19 syndrome in the second year after acute infection: A population-based, nested case-control study

BACKGROUND

Self-reported health problems following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are common and often include relatively non-specific complaints such as fatigue, exertional dyspnoea, concentration or memory disturbance and sleep problems. The long-term prognosis of such post-acute sequelae of COVID-19/post-COVID-19 syndrome (PCS) is unknown, and data finding and correlating organ dysfunction and pathology with self-reported symptoms in patients with non-recovery from PCS is scarce. We wanted to describe clinical characteristics and diagnostic findings among patients with PCS persisting for >1 year and assessed risk factors for PCS persistence versus improvement.

METHODS AND FINDINGS

This nested population-based case-control study included subjects with PCS aged 18-65 years with (n = 982) and age- and sex-matched control subjects without PCS (n = 576) according to an earlier population-based questionnaire study (6-12 months after acute infection, phase 1) consenting to provide follow-up information and to undergo comprehensive outpatient assessment, including neurocognitive, cardiopulmonary exercise, and laboratory testing in four university health centres in southwestern Germany (phase 2, another 8.5 months [median, range 3-14 months] after phase 1). The mean age of the participants was 48 years, and 65% were female. At phase 2, 67.6% of the patients with PCS at phase 1 developed persistent PCS, whereas 78.5% of the recovered participants remained free of health problems related to PCS. Improvement among patients with earlier PCS was associated with mild acute index infection, previous full-time employment, educational status, and no specialist consultation and not attending a rehabilitation programme. The development of new symptoms related to PCS among participants initially recovered was associated with an intercurrent secondary SARS-CoV-2 infection and educational status. Patients with persistent PCS were less frequently never smokers (61.2% versus 75.7%), more often obese (30.2% versus 12.4%) with higher mean values for body mass index (BMI) and body fat, and had lower educational status (university entrance qualification 38.7% versus 61.5%) than participants with continued recovery. Fatigue/exhaustion, neurocognitive disturbance, chest symptoms/breathlessness and anxiety/depression/sleep problems remained the predominant symptom clusters. Exercise intolerance with post-exertional malaise (PEM) for >14 h and symptoms compatible with myalgic encephalomyelitis/chronic fatigue syndrome were reported by 35.6% and 11.6% of participants with persistent PCS patients, respectively. In analyses adjusted for sex-age class combinations, study centre and university entrance qualification, significant differences between participants with persistent PCS versus those with continued recovery were observed for performance in three different neurocognitive tests, scores for perceived stress, subjective cognitive disturbances, dysautonomia, depression and anxiety, sleep quality, fatigue and quality of life. In persistent PCS, handgrip strength (40.2 [95% confidence interval (CI) [39.4, 41.1]] versus 42.5 [95% CI [41.5, 43.6]] kg), maximal oxygen consumption (27.9 [95% CI [27.3, 28.4]] versus 31.0 [95% CI [30.3, 31.6]] ml/min/kg body weight) and ventilatory efficiency (minute ventilation/carbon dioxide production slope, 28.8 [95% CI [28.3, 29.2]] versus 27.1 [95% CI [26.6, 27.7]]) were significantly reduced relative to the control group of participants with continued recovery after adjustment for sex-age class combinations, study centre, education, BMI, smoking status and use of beta blocking agents. There were no differences in measures of systolic and diastolic cardiac function at rest, in the level of N-terminal brain natriuretic peptide blood levels or other laboratory measurements (including complement activity, markers of Epstein-Barr virus [EBV] reactivation, inflammatory and coagulation markers, serum levels of cortisol, adrenocorticotropic hormone and dehydroepiandrosterone sulfate). Screening for viral persistence (PCR in stool samples and SARS-CoV-2 spike antigen levels in plasma) in a subgroup of the patients with persistent PCS was negative. Sensitivity analyses (pre-existing illness/comorbidity, obesity, medical care of the index acute infection) revealed similar findings. Patients with persistent PCS and PEM reported more pain symptoms and had worse results in almost all tests. A limitation was that we had no objective information on exercise capacity and cognition before acute infection. In addition, we did not include patients unable to attend the outpatient clinic for whatever reason including severe illness, immobility or social deprivation or exclusion.

CONCLUSIONS

In this study, we observed that the majority of working age patients with PCS did not recover in the second year of their illness. Patterns of reported symptoms remained essentially similar, non-specific and dominated by fatigue, exercise intolerance and cognitive complaints. Despite objective signs of cognitive deficits and reduced exercise capacity, there was no major pathology in laboratory investigations, and our findings do not support viral persistence, EBV reactivation, adrenal insufficiency or increased complement turnover as pathophysiologically relevant for persistent PCS. A history of PEM was associated with more severe symptoms and more objective signs of disease and might help stratify cases for disease severity.

Neuroglial responses to bacterial, viral, and fungal neuroinfections

Evidence regarding the host's response to peripheral pathogens in humans abound, whereas studies on the pathogenesis of central nervous system-penetrating infections are relatively scarce. However, given the spate of epidemic and pandemic neuroinfections in the 21st century, the field has experienced a renewed interest lately. This chapter discusses a timely and exciting topic on the roles of glial cells, mainly microglia and astrocytes, in neuroinvasive infections. This chapter considered fungal, viral, and bacterial neuroinfections, X-raying their neuroinvasiveness, neurotropism, and neurovirulence before focusing on specific examples notable for each category, including Escherichia coli, Cryptococcus neoformans, and SARS-CoV-2. These infections are renowned worldwide for a high case-fatality rate, leaving many survivors with life-long morbidity and others with a bleak future neurologic prognosis. Importantly, the chapter discusses possible ways microglia and astrocytes are culpable in these infections and provides approaches by which they can be manipulated for therapeutic purposes, identifying viable research gaps in the process. Additionally, it offers a synopsis of ongoing works considering microglial selective targeting to attenuate the pathology, morbidity, and mortality associated with these neuroinfections. Considering that microglia and astrocytes are first responders in the central nervous system, targeting these glial cells could be the game changer in managing existing and emerging neuroinvasive infections.

Sustained Vascular Inflammatory Effects of SARS-CoV-2 Spike Protein on Human Endothelial Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been associated with systemic inflammation and vascular injury, which contribute to the development of acute respiratory syndrome (ARDS) and the mortality of COVID-19 infection. Moreover, multiorgan complications due to persistent endothelial dysfunction have been suspected as the cause of post-acute sequelae of SARS-CoV-2 infection. Therefore, elucidation of the vascular inflammatory effect of SARS-CoV-2 will increase our understanding of how endothelial cells (ECs) contribute to the short- and long-term consequences of SARS-CoV-2 infection. Here, we investigated the interaction of SARS-CoV-2 spike protein with human ECs from aortic (HAoEC) and pulmonary microvascular (HPMC) origins, cultured under physiological flow conditions. We showed that the SARS-CoV-2 spike protein triggers prolonged expression of cell adhesion markers in both ECs, similar to the effect of TNF-α. SARS-CoV-2 spike treatment also led to the release of various cytokines and chemokines observed in severe COVID-19 patients. Moreover, increased binding of leucocytes to the endothelial surface and a procoagulant state of the endothelium were observed. Transcriptomic profiles of SARS-CoV-2 spike-activated HPMC and HAoEC showed prolonged upregulation of genes and pathways associated with responses to virus, cytokine-mediated signaling, pattern recognition, as well as complement and coagulation pathways. Our findings support experimental and clinical observations of the vascular consequences of SARS-CoV-2 infection and highlight the importance of EC protection as one of the strategies to mitigate the severe effects as well as the possible post-acute complications of COVID-19 disease.

Diagnostic challenges of long COVID in children: a survey of pediatric health care providers' preferences and practices

Introduction

Given the challenges in diagnosing children with long COVID, we sought to explore diagnostic practices and preferences among clinicians.

Methods

A ten-question survey assessed pediatric providers' clinical decision making for identifying and evaluating long COVID in children. Of the 120 survey respondents, 84 (70%) were physicians, 31 (26%) nurse practitioners, and 5 (4%) physician assistants.

Results

The most common categories of symptoms identified as raising suspicion for long COVID in children included cardiopulmonary symptoms, selected by 119 (99%) of pediatric providers, and neurocognitive symptoms, selected by 118 (98%) of providers. However, there was more ambiguity on the primary feature of long COVID, with providers selecting a range of key symptoms. Of all physical exam findings, postural orthostatic tachycardia, was most suggestive of long COVID [identified by 49 (41%) of pediatric providers], whereas one-third of providers reported no specific identifiable exam finding.

Discussion

Pediatric providers report variable decision making in the clinical evaluation of long COVID, with patient demographics and clinical factors impacting whether a diagnosis of long COVID is considered. This variation in diagnosing pediatric long COVID reflects ambiguity in the definition of long COVID in children and the absence of clinical guidelines to support providers in the identification of disease and treatment. This study highlights an area of need for future clinical advances in pediatric long COVID.

Pediatric SARS-CoV-2 long term outcomes study (PECOS): cross sectional analysis at baseline

BACKGROUND

PECOS is an ongoing study aimed to characterize long-term outcomes following pediatric SARS-CoV-2 infection.

METHODS

This is a cross-sectional analysis of infected and uninfected cohorts at baseline. Participants (0-21 years) with laboratory-confirmed SARS-CoV-2 infection were enrolled as infected. Uninfected were defined as individuals without history or laboratory evidence of SARS-CoV-2 infection. Outcome measures included demographics, medical history, review of symptoms, physical exam, cardiopulmonary evaluation and validated psychological and developmental surveys. Primary outcomes were cohort comparisons for abnormalities on all measures.

RESULTS

654 participants (541 infected, 113 uninfected) completed baseline visits by June 30, 2023. Infected participants were more likely to report constitutional (OR: 2.24), HEENT (OR: 3.74); respiratory (OR: 2.41), or gastrointestinal (OR: 2.58) symptoms. Infected had worse scores in domains of Pain, Fatigue, Global Health, Physical and Cognitive functioning, Mobility and Sleep disturbances when compared to uninfected controls using Patient Reported Outcomes. Cardiopulmonary findings were similar among cohorts.

CONCLUSIONS

The first report of this ongoing longitudinal study demonstrates that infected participants were more likely to report symptoms compared to uninfected controls, which may affect performance and quality of life of these individuals. Longitudinal data will increase understanding of long-term effects of SARS-CoV-2 infection in children.

CLINICALTRIALS

gov Identifier: NCT04830852 IMPACT: This study establishes a large, diverse, prospective, longitudinal, multi-center cohort of children with history of SARS-CoV-2 infection compared to an uninfected cohort to be followed for 3 years. Cross-sectional cohort analysis at study entry showed infected participants were more likely to report constitutional, respiratory, and GI symptoms compared to uninfected controls. Infected participants were more likely to have significantly worse parent-reported performance in 6 of 10 Patient Reported Outcome Measures domains. Continued study of this cohort will help identify clinical sequelae of COVID-19, characterize the immune response to SARS-CoV-2 infection, and identify potential genetic/immunologic factors associated with long-term outcomes.

Interaction of HERVs with PAMPs in Dysregulation of Immune Response Cascade Upon SARS-CoV-2 Infections

Human endogenous retroviruses (HERVs) are genomic fragments integrated into human DNA from germline infections by exogenous retroviruses that threatened primates early in their evolution and are inherited vertically in the germline. So far, HERVs have been studied in the context of extensive immunopathogenic, neuropathogenic and even oncogenic effects within their host. In particular, in our paper, we elaborate on the aspects related to the possible correlation of transposable HERV elements' activation and SARS-CoV-2 spike protein's presence in cells of COVID-19 patients or upon COVID-19 vaccination with implications for natural and adaptive immunity. In particular, the release of cytokines TNF-α, IL-1β and IL-6 occurs in such cases and plays a notable role in sustaining chronic inflammation. Moreover, well-known interindividual variations of HERVs might partially account for the interpersonal variability of COVID-19 symptoms or unwanted events post-vaccination. Accordingly, further studies are required to clarify the SARS-CoV-2 spike protein's role in triggering HERVs.

Persistence of spike protein at the skull-meninges-brain axis may contribute to the neurological sequelae of COVID-19

SARS-CoV-2 infection is associated with long-lasting neurological symptoms, although the underlying mechanisms remain unclear. Using optical clearing and imaging, we observed the accumulation of SARS-CoV-2 spike protein in the skull-meninges-brain axis of human COVID-19 patients, persisting long after viral clearance. Further, biomarkers of neurodegeneration were elevated in the cerebrospinal fluid from long COVID patients, and proteomic analysis of human skull, meninges, and brain samples revealed dysregulated inflammatory pathways and neurodegeneration-associated changes. Similar distribution patterns of the spike protein were observed in SARS-CoV-2-infected mice. Injection of spike protein alone was sufficient to induce neuroinflammation, proteome changes in the skull-meninges-brain axis, anxiety-like behavior, and exacerbated outcomes in mouse models of stroke and traumatic brain injury. Vaccination reduced but did not eliminate spike protein accumulation after infection in mice. Our findings suggest persistent spike protein at the brain borders may contribute to lasting neurological sequelae of COVID-19.

Development of a prediction nomogram for IgG levels among asymptomatic or mild patients with COVID-19

Objective

COVID-19 has evolved into a seasonal coronavirus disease, characterized by prolonged infection duration and repeated infections, significantly increasing the risk of patients developing long COVID. Our research focused on the immune responses in asymptomatic and mild cases, particularly the critical factors influencing serum immunoglobulin G (IgG) levels and their predictive value.

Methods

We conducted a retrospective analysis on data from 1939 asymptomatic or mildly symptomatic COVID-19 patients hospitalized between September 2022 and June 2023. Spearman methods were used to test the correlation between serum IgG and age, immunoglobulin M (IgM), procalcitonin (PCT), interleukin-6 (IL-6), nucleic acid conversion time, and BMI. Univariate and multivariate logistic regression analyses identified independent key factors influencing serum IgG levels, which were integrated and visualized in a nomogram. Finally, receiver operating characteristic (ROC) curves were plotted to predict the model's diagnostic performance by calculating the AUC.

Results

Mild patients showed higher levels of IgG, IgM, and longer nucleic acid conversion times than asymptomatic patients, and a lower proportion of them had received ≥ 3 COVID-19 vaccine doses. Serum IgG was positively correlated with serum IgM and negatively correlated with age, PCT, IL-6, and BMI. Notably, it showed a moderate negative correlation with nucleic acid conversion time (r = -0.578, P < 0.001). Logistic regression results showed that younger age, lower IL-6 levels, ≥ 3 doses of vaccine, and no comorbidities were independent predictors of serum IgG levels ≥ 21.08 g/L. We used age, IL-6 levels, vaccine doses, and comorbidities to create a nomogram for predicting serum IgG levels, with the area under the ROC curve reaching 0.772.

Conclusion

Age, IL-6 levels, vaccination status, and comorbidities were independent predictors of serum IgG levels in asymptomatic or mild COVID-19 patients, facilitating risk stratification and clinical decision-making. Notably, receiving ≥3 doses of the COVID-19 vaccine was the most beneficial factor for elevated serum IgG levels.

Defining long COVID using a population-based SARS-CoV-2 survey in California

BACKGROUND

More than four years after the start of the COVID-19 pandemic, understanding of SARS-CoV-2 burden and post-acute sequela of COVID (PASC), or long COVID, continues to evolve. However, prevalence estimates are disparate and uncertain. Leveraging survey responses from a large serosurveillance study, we assess prevalence estimates using five different long COVID definitions among California residents.

METHODS

The California Department of Public Health (CDPH) conducted a cross-sectional survey that included questions about acute COVID-19 infection and recovery. A random selection of California households was invited to participate in a survey that included demographic information, clinical symptoms, and COVID-19 vaccination history. We assessed prevalence and predictors of long COVID among those previously testing positive for SARS-CoV-2 across different definitions using logistic regression.

FINDINGS

A total of 2883 participants were included in this analysis; the majority identified as female (62.5 %), and the median age was 39 years (interquartile range: 17-55 years). We found a significant difference in long COVID prevalence across definitions with the highest prevalence observed when participants were asked about incomplete recovery (20.9 %, 95 % confidence interval [CI]: 19.4-22.5) and the lowest prevalence was associated with severe long COVID affecting an estimated 4.9 % (95 % CI 4.1-5.7) of the participant population. Individuals that completed the primary vaccination series had significantly lower prevalence of long COVID compared to those that did not receive COVID vaccination.

INTERPRETATION

There were significant differences in the estimated prevalence of long COVID across different definitions. People who experience a severe initial COVID-19 infection should be considered at a higher probability for developing long COVID.

FUNDING

Centers for Disease Control and Prevention - Epidemiology and Laboratory Capacity.

Multi-Organ Spread and Intra-Host Diversity of SARS-CoV-2 Support Viral Persistence, Adaptation, and a Mechanism That Increases Evolvability

Intra-host diversity is an intricate phenomenon related to immune evasion, antiviral resistance, and evolutionary leaps along transmission chains. SARS-CoV-2 intra-host variation has been well-evidenced from respiratory samples. However, data on systemic dissemination and diversification are relatively scarce and come from immunologically impaired patients. Here, the presence and variability of SARS-CoV-2 were assessed among 71 tissue samples obtained from multiple organs including lung, intestine, heart, kidney, and liver from 15 autopsies with positive swabs and no records of immunocompromise. The virus was detected in most organs in the majority of autopsies. All organs presented intra-host single nucleotide variants (iSNVs) with low, moderate, and high abundances. The iSNV abundances observed within different organs indicate that the virus can mutate at one host site and subsequently spread to other parts of the body. In agreement with previous data from respiratory samples, our lung samples presented no more than 10 iSNVs each. But interestingly, when analyzing different organs we were able to detect between 11 and 45 iSNVs per case. Our results indicate that SARS-CoV-2 can replicate, and evolve in a compartmentalized manner, in different body sites, which agrees with the "viral reservoir" theory. We elaborate on how compartmentalized evolution in multiple organs may contribute to SARS-CoV-2 evolving so rapidly despite the virus having a proofreading mechanism.

The Intestine in Acute and Long COVID: Pathophysiological Insights and Key Lessons

Post-Acute Sequelae of SARS-CoV-2 infection (PASC), commonly known as Long COVID, represents a significant and complex health challenge with a wide range of symptoms affecting multiple organ systems. This review examines the emerging evidence suggesting a critical role of the gut and gut-brain axis in the pathophysiology of Long COVID. It explores how changes in the gut microbiome, disruption of gut barrier integrity, and the persistence of SARS-CoV-2 antigens within the gastrointestinal tract may contribute to the prolonged and varied symptoms seen in Long COVID, including chronic inflammation and neuropsychiatric disturbances. The review also summarizes key insights gained about Long COVID, highlighting its multifactorial nature, which involves immune dysregulation, microvascular damage, and autonomic nervous system dysfunction, with the gut playing a central role in these processes. While progress has been made in understanding these mechanisms, current evidence remains inconclusive. The challenges of establishing causality, standardizing research methodologies, and addressing individual variations in the microbiome are discussed, emphasizing the need for further longitudinal studies and more comprehensive approaches to enhance our understanding of these complex interactions. This review underscores the importance of personalized approaches in developing effective diagnostic and therapeutic strategies for Long COVID, while also acknowledging the significant gaps in our current understanding. Future research should aim to further unravel the complex interplay between the gut and Long COVID, ultimately improving outcomes for those affected by this condition.

Measurement of circulating viral antigens post-SARS-CoV-2 infection in a multicohort study

OBJECTIVES

To determine the proportion of individuals with detectable antigen in plasma or serum after SARS-CoV-2 infection and the association of antigen detection with postacute sequelae of COVID-19 (PASC) symptoms.

METHODS

Plasma and serum samples were collected from adults participating in four independent studies at different time points, ranging from several days up to 14 months post-SARS-CoV-2 infection. The primary outcome measure was to quantify SARS-CoV-2 antigens, including the S1 subunit of spike, full-length spike, and nucleocapsid, in participant samples. The presence of 34 commonly reported PASC symptoms during the postacute period was determined from participant surveys or chart reviews of electronic health records.

RESULTS

Of the 1569 samples analysed from 706 individuals infected with SARS-CoV-2, 21% (95% CI, 18-24%) were positive for either S1, spike, or nucleocapsid. Spike was predominantly detected, and the highest proportion of samples was spike positive (20%; 95% CI, 18-22%) between 4 and 7 months postinfection. In total, 578 participants (82%) reported at least one of the 34 PASC symptoms included in our analysis ≥1 month postinfection. Cardiopulmonary, musculoskeletal, and neurologic symptoms had the highest reported prevalence in over half of all participants, and among those participants, 43% (95% CI, 40-45%) on average were antigen-positive. Among the participants who reported no ongoing symptoms (128, 18%), antigen was detected in 28 participants (21%). The presence of antigen was associated with the presence of one or more PASC symptoms, adjusting for sex, age, time postinfection, and cohort (OR, 1.8; 95% CI, 1.4-2.2).

DISCUSSION

The findings of this multicohort study indicate that SARS-CoV-2 antigens can be detected in the blood of a substantial proportion of individuals up to 14 months after infection. While approximately one in five asymptomatic individuals was antigen-positive, roughly half of all individuals reporting ongoing cardiopulmonary, musculoskeletal, and neurologic symptoms were antigen-positive.

Post-acute sequelae of SARS-CoV-2 infection (Long COVID) in older adults

Long COVID, also known as PASC (post-acute sequelae of SARS-CoV-2), is a complex infection-associated chronic condition affecting tens of millions of people worldwide. Many aspects of this condition are incompletely understood. Among them is how this condition may manifest itself in older adults and how it might impact the older population. Here, we briefly review the current understanding of PASC in the adult population and examine what is known on its features with aging. Finally, we outline the major gaps and areas for research most germane to older adults.

The effect of pre-COVID and post-COVID vaccination on long COVID: A systematic review and meta-analysis

BACKGROUND

Long COVID affects millions of people and results in a substantial decrease in quality of life. Previous primary studies and reviews attempted to study the effect of vaccination against long COVID, but these studies varied in the cut-off time of long COVID. We adhered to the WHO's definition of long COVID and conducted a systematic review and meta-analysis on the effect of pre-COVID and post-COVID vaccination on long COVID.

METHODS

We obtained data from 13 databases up to 18 February 2024, including peer reviewed and preprint studies. Our inclusion criteria were: (1) long COVID definition as 3 months or beyond, (2) comparing long COVID symptoms between vaccinated and unvaccinated groups, (3) subjects received vaccinations either before or after infected with COVID, (4) the number of doses received by participants was specified. We extracted study characteristics and data and computed the summary odds ratio (OR) with the DerSimonian and Laird random effects model. We then performed subgroup analyses based on the main vaccine brand and long COVID assessment method. ROBINS-I framework was used for assessment of risk of bias and the GRADE approach was used for evaluating the certainty of evidence.

FINDINGS

We included data from 25 observational studies (n = 14,128,260) with no randomised controlled trials. One-dose pre-COVID vaccination did not have an effect on long COVID (number of studies = 10, summary OR = 1.01, 95% CI = 0.88-1.15, p-value = 0.896). Two-dose pre-COVID vaccination was associated with a 24% reduced odds of long COVID (number of studies = 15, summary OR = 0.76, 95% CI = 0.65-0.89, p-value = 0.001) and 4 symptoms (fatigue, headache, loss of smell, muscle pain) out of 10 symptoms analysed. The OR of three-dose pre-COVID vaccination against overall long COVID was statistically insignificant but was far away from 1 (number of studies = 3, summary OR = 0.31, 95% CI = 0.05-1.84, p-value = 0.198). One-dose post-COVID vaccination was associated with a 15% reduced odds of long COVID (number of studies = 5, summary OR = 0.85, 95% CI = 0.73-0.98, p-value = 0.024). The OR of two-dose post-COVID vaccination against long COVID was statistically insignificant but was far away from 1 (number of studies = 3, summary OR = 0.63, 95% CI = 0.38-1.03, p-value = 0.066).

INTERPRETATION

Our study suggests that 2-dose pre-COVID vaccination and 1-dose post-COVID vaccination are associated with a lower risk of long COVID. Since long COVID reduces quality of life substantially, vaccination could be a possible measure to maintain quality of life by partially protecting against long COVID.

Thymidine phosphorylase mediates SARS-CoV-2 spike protein enhanced thrombosis in K18-hACE2TG mice

INTRODUCTION

Thymidine phosphorylase (TYMP), which facilitates platelet activation and thrombosis, is significantly increased in COVID-19 patients. We hypothesize that TYMP mediates SARS-CoV-2 spike protein (SP)-induced thrombosis.

MATERIALS AND METHODS

Plasmids encoding wildtype SP or empty vector (p3.1) were transfected into COS-7 cells, and cell lysates were prepared as a reservoir for SP or p3.1 (control), respectively. K18-hACE2TG and K18-hACE2TG/Tymp-/- mice were treated with a single dose of SP or p3.1 by intraperitoneal injection and then subjected to thrombosis studies three days later. The role of SP on inflammatory signaling activation was assessed in BEAS-2B cells.

RESULTS

SARS-CoV-2 SP increased the expression of TYMP, resulting in the activation of STAT3 and NF-κB in BEAS-2B cells. A siRNA-mediated knockdown of TYMP attenuated SP-enhanced activation of STAT3. SP significantly promoted arterial thrombosis in K18-hACE2TG mice. SP-accelerated thrombosis was attenuated by inhibition or genetic ablation of TYMP. SP treatment did not influence ADP- or collagen-induced platelet aggregation but significantly increased platelet adhesion to fibrinogen. SP treatment also significantly shortened activated partial thromboplastin time, which was reversed and even prolonged by TYMP deficiency. Additionally, SP binds to platelet factor 4 (PF4) and TYMP. TYMP does not bind PF4 but enhances the formation of the SP/PF4 complex, which may augment the procoagulant and prothrombotic effect of PF4.

CONCLUSIONS

We conclude that SP is prothrombotic and upregulates TYMP expression, and TYMP inhibition or knockout mitigates SP-enhanced thrombosis. These findings suggest that inhibition of TYMP may be a novel therapeutic strategy for COVID-19-associated thrombosis.