A role for T-cell exhaustion in Long COVID-19 and severe outcomes for several categories of COVID-19 patients

Current landscape of long COVID clinical trials

Long COVID was reported as a multi-systemic condition after the infection of SARS-CoV-2, and more than 65 million people are suffering from this disease. It has been noted that around 10% of severe SARS-CoV-2 infected individuals are suffering from the enduring effects of long COVID. The symptoms of long COVID have also been noted in several mild or asymptomatic SARS-CoV-2 infected individuals. While limited reports on clinical trials investigating new therapeutics for long COVID exist, there is an abundance of scattered information available regarding these trials. This review explores the extensive literature search, and complete clinical trial database search to map the current status of long COVID clinical trials worldwide. The study listed about 110 long COVID clinical trials. In addition to conducting extensive long COVID clinical trials, we have comprehensively presented an overview of the condition, its symptoms, notable manifestations, associated clinical trials, the unique challenges it poses, and our recommendations for addressing long COVID.

Effect of SARS-CoV-2 and Toxoplasma gondii co-infection on IFN-γ and TNF-α expression and its impact on disease severity

The symptomatology of COVID-19 is dependent on the immune status and the cytokine response of the host. The cytokine level of the host is influenced by the presence of chronic persistent or latent infections with co-pathogens. Parasitic diseases are known to induce host immune-modulation which may impact the response to co-infection. Toxoplasmosis is a widespread protozoal infection that remains quiescent in its latent form to be re-activated during states of immune depression. Clinical data on the relation between toxoplasmosis and COVID-19 cytokine profile and symptomatology are still insufficient. Seventy-nine subjects were included in this study. Patients were diagnosed with COVID-19 by PCR. Serological testing for toxoplasmosis was performed by the detection of anti-Toxoplasma IgG antibodies, in addition to IgG avidity testing. IFN-γ and TNF-α levels were determined by RT-PCR. Among patients diagnosed with COVID-19, 67.1% were seronegative for anti-Toxoplasma IgG, while 32.9% were seropositive. High avidity was found in 10 cases (40% of seropositive cases), 4 of whom required ICU administration, while low avidity was found in 15 cases (60%), 7 of which were administered to the ICU. TNF-α and INF-γ levels were significantly higher in COVID-19 patients than in healthy control subjects. No significant association was found between the seroprevalence of toxoplasmosis and the presence of COVID-19 and its severity. Cytokines were significantly higher in both seropositive and seronegative COVID-19 patients than in their control counterparts. The high prevalence of toxoplasmosis merits further exploration of its relation to COVID-19 by mass studies.

Genetic diversity and seroprevalence of Toxoplasma gondii in COVID‑19 patients; a first case-control study in Iran

BACKGROUND

Toxoplasmosis is a serious or life-threatening disease in immunosuppressed patients and pregnant women. This study examined the likely association between Toxoplasma gondii infection and COVID-19 patients with moderate illness.

METHODS

Seventy blood samples were collected from patients at the Health Reference Laboratory of Tabriz, Northwest Iran from April 2021 to September 2021. In addition, 70 healthy subjects of the same age (37 ± 15 years) and sex distribution were ethnically matched. Sera samples were examined for the detection of anti-Toxoplasma antibodies using ELISA. Nested-PCR targets were amplified based on the B1 and GRA6 genes. GRA6 amplicons were subjected to sequencing and phylogenetic analysis.

RESULTS

The seroprevalence of toxoplasmosis based on IgG titer was 35.7% in the COVID‑19 patients and 27.1% in the control group, representing not to be associated with the Toxoplasma seropositivity in COVID‑19 patients (P = 0.18) compared to healthy subjects. Anti-T. gondii IgM was not found in any of the patients and healthy individuals. According to PCR amplification of the B1 and GRA6 genes, the frequency of T. gondii in COVID-19 patients was 14.2% (10/70). However, no T. gondii infection was detected in the healthy group. The CD4+T cell count was relatively lower in toxoplasmosis-infected patients (430-450 cells/mm3) than in control group (500-1500 cells/mm3). High genetic diversity (Hd: 0.710) of the type I strain of T. gondii was characterized in the patients. Present results showed that consumption of raw vegetables and close contact with stray cats can increase the transmission of T. gondii to COVID-19 patients (P < 0.01).

CONCLUSIONS

The current study revealed that T. gondii type I infection is unequivocally circulating among the COVID-19 patients in Tabriz; However, no significant association was observed between the occurrence of Toxoplasma and the severity of COVID-19. To make more accurate health decisions, multicenter investigations with a larger sample size of different ethnic groups of the Iranian population are needed.

Clinical and Immunological Impacts of Latent Toxoplasmosis on COVID-19 Patients

Background Parasites are well-known immune-modulators. They inhibit some aspects of the immune system to ensure persistence inside the host for a long time; meanwhile, they stimulate other immune aspects to assure the survival of the host. Wide variations in the severity of coronavirus disease 2019 (COVID-19) among developed and developing countries were reported during the COVID-19 pandemic. Parasitic infections, including Toxoplasma gondii (T. gondii), were claimed to contribute to such variations. Methods To explore a possible relationship between latent toxoplasmosis and COVID-19 severity, our study included 44 blood samples from moderate/severe COVID-19 patients, who were admitted to Mansoura University Hospitals, Egypt, during the pandemic. Patients' sera were screened for Toxoplasma IgG antibodies using ELISA (Roche Diagnostics, Indianapolis, USA), and the gene expression of important immune markers (iNOS, arginase-1, IFN-γ, TNF-α, IL-6, IL-10, and TGF-β) was checked using real-time quantitative PCR. Clinical and laboratory data were obtained from the patients' medical records. Results Toxoplasma IgG antibodies were detected in 33 (75%) of patients. None of the studied clinical or laboratory parameters showed any significant changes in relation to toxoplasmosis seroprevalence. Further classification of the patients according to COVID-19 severity and Toxoplasma seroprevalence did not reveal any changes related to toxoplasmosis as well. Conclusion Our study indicates that latent toxoplasmosis has no effect on the severity of COVID-19.

Impact of P-selectin-PSGL-1 Axis on Platelet-Endothelium-Leukocyte Interactions in Fatal COVID-19

In critically ill patients infected with SARS-CoV-2, early leukocyte recruitment to the respiratory system was found to be orchestrated by leukocyte trafficking molecules accompanied by massive secretion of proinflammatory cytokines and hypercoagulability. Our study aimed to explore the interplay between leukocyte activation and pulmonary endothelium in different disease stages of fatal COVID-19. Our study comprised 10 COVID-19 postmortem lung specimens and 20 control lung samples (5 acute respiratory distress syndrome, 2 viral pneumonia, 3 bacterial pneumonia, and 10 normal), which were stained for antigens representing the different steps of leukocyte migration: E-selectin, P-selectin, PSGL-1, ICAM1, VCAM1, and CD11b. Image analysis software QuPath was used for quantification of positive leukocytes (PSGL-1 and CD11b) and endothelium (E-selectin, P-selectin, ICAM1, VCAM1). Expression of IL-6 and IL-1β was quantified by RT-qPCR. Expression of P-selectin and PSGL-1 was strongly increased in the COVID-19 cohort compared with all control groups (COVID-19:Controls, 17:23, P < .0001; COVID-19:Controls, 2:75, P < .0001, respectively). Importantly, P-selectin was found in endothelial cells and associated with aggregates of activated platelets adherent to the endothelial surface in COVID-19 cases. In addition, PSGL-1 staining disclosed positive perivascular leukocyte cuffs, reflecting capillaritis. Moreover, CD11b showed a strongly increased positivity in COVID-19 compared with all controls (COVID-19:Controls, 2:89; P = .0002), indicating a proinflammatory immune microenvironment. Of note, CD11b exhibited distinct staining patterns at different stages of COVID-19 disease. Only in cases with very short disease course, high levels of IL-1β and IL-6 mRNA were observed in lung tissue. The striking upregulation of PSGL-1 and P-selectin reflects the activation of this receptor-ligand pair in COVID-19, increasing the efficiency of initial leukocyte recruitment, thus promoting tissue damage and immunothrombosis. Our results show that endothelial activation and unbalanced leukocyte migration play a central role in COVID-19 involving the P-selectin-PSGL-1 axis.

Deep Phenotyping of Neurologic Postacute Sequelae of SARS-CoV-2 Infection

BACKGROUND AND OBJECTIVES

SARS-CoV-2 infection has been associated with a syndrome of long-term neurologic sequelae that is poorly characterized. We aimed to describe and characterize in-depth features of neurologic postacute sequelae of SARS-CoV-2 infection (neuro-PASC).

METHODS

Between October 2020 and April 2021, 12 participants were seen at the NIH Clinical Center under an observational study to characterize ongoing neurologic abnormalities after SARS-CoV-2 infection. Autonomic function and CSF immunophenotypic analysis were compared with healthy volunteers (HVs) without prior SARS-CoV-2 infection tested using the same methodology.

RESULTS

Participants were mostly female (83%), with a mean age of 45 ± 11 years. The median time of evaluation was 9 months after COVID-19 (range 3-12 months), and most (11/12, 92%) had a history of only a mild infection. The most common neuro-PASC symptoms were cognitive difficulties and fatigue, and there was evidence for mild cognitive impairment in half of the patients (MoCA score <26). The majority (83%) had a very disabling disease, with Karnofsky Performance Status ≤80. Smell testing demonstrated different degrees of microsmia in 8 participants (66%). Brain MRI scans were normal, except 1 patient with bilateral olfactory bulb hypoplasia that was likely congenital. CSF analysis showed evidence of unique intrathecal oligoclonal bands in 3 cases (25%). Immunophenotyping of CSF compared with HVs showed that patients with neuro-PASC had lower frequencies of effector memory phenotype both for CD4⁺ T cells (p < 0.0001) and for CD8⁺ T cells (p = 0.002), an increased frequency of antibody-secreting B cells (p = 0.009), and increased frequency of cells expressing immune checkpoint molecules. On autonomic testing, there was evidence for decreased baroreflex-cardiovagal gain (p = 0.009) and an increased peripheral resistance during tilt-table testing (p < 0.0001) compared with HVs, without excessive plasma catecholamine responses.

DISCUSSION

CSF immune dysregulation and neurocirculatory abnormalities after SARS-CoV-2 infection in the setting of disabling neuro-PASC call for further evaluation to confirm these changes and explore immunomodulatory treatments in the context of clinical trials.

The impact of HBV infection on clinical outcomes of COVID-19 patients: a systematic review and meta-analysis

The impact of hepatitis B virus (HBV) infection on clinical outcomes of coronavirus disease 2019 (COVID-19) remains unclear. The aim of this study is to explore this impact. For this systematic review and meta-analysis, we searched PubMed, Web of Science, Embase, Cochrane library, China National Knowledge Infrastructure (CKNI), China Science and Technology Journal Database (VIP), and Wan Fang database for articles between 1 January 2020 and 1 February 2023. We used the Newcastle-Ottawa Quality Assessment to evaluate the study's quality. A random-effects meta-analysis was performed utilising the rates of severe/critical illness and death in COVID-19 patients with and without HBV infection. Eighteen studies with a total of 40,502 participants met the inclusion criteria. The meta-analysis showed that compared to those without HBV infection, COVID-19 patients with HBV were at increased risk of mortality (OR = 1.65, I2 = 58%, and 95% CI 1.08-2.53) and severity (OR = 1.90, I2 = 44%, and 95% CI 1.62-2.24). The region and gender may influence the outcomes of COVID-19 patients with HBV infection, but it requires more global data to confirm. In conclusion, HBV infection is significantly linked to an increased risk of severity and mortality in COVID-19.

Impact of COVID 19 on erectile function

Purpose: COVID-19, a novel infection, presented with several complications, including socioeconomical and reproductive health challenges such as erectile dysfunction (ED). The present review summarizes the available shreds of evidence on the impact of COVID-19 on ED.Materials and methods: All published peer-reviewed articles from the onset of the COVID-19 outbreak to date, relating to ED, were reviewed. Results: Available pieces of evidence that ED is a consequence of COVID-19 are convincing. COVID-19 and ED share common risk factors such as disruption of vascular integrity, cardiovascular disease (CVD), cytokine storm, diabetes, obesity, and chronic kidney disease (CKD). COVID-19 also induces impaired pulmonary haemodynamics, increased ang II, testicular damage and low serum testosterone, and reduced arginine-dependent NO bioavailability that promotes reactive oxygen species (ROS) generation and endothelial dysfunction, resulting in ED. In addition, COVID-19 triggers psychological/mental stress and suppresses testosterone-dependent dopamine concentration, which contributes to incident ED.Conclusions: In conclusion, COVID-19 exerts a detrimental effect on male reproductive function, including erectile function. This involves a cascade of events from multiple pathways. As the pandemic dwindles, identifying the long-term effects of COVID-19-induced ED, and proffering adequate and effective measures in militating against COVID-19-induced ED remains pertinent.

Concurrent infections of cells by two pathogens can enable a reactivation of the first pathogen and the second pathogen's accelerated T-cell exhaustion

When multiple intracellular pathogens, such as viruses, bacteria, fungi and protozoan parasites, infect the same host cell, they can help each other. A pathogen can substantially help another pathogen by disabling cellular immune defenses, using non-coding ribonucleic acids and/or pathogen proteins that target interferon-stimulated genes and other genes that express immune defense proteins. This can enable reactivation of a latent first pathogen and accelerate T-cell exhaustion and/or T-cell suppression regarding a second pathogen. In a worst-case scenario, accelerated T-cell exhaustion and/or T-cell suppression regarding the second pathogen can impair T-cell functionality and allow a first-time, immunologically novel second pathogen infection to escape all adaptive immune system defenses, including antibodies. The interactions of herpesviruses with concurrent intracellular pathogens in epithelial cells and B-cells, the interactions of the human immunodeficiency virus with Mycobacterium tuberculosis in macrophages and the interactions of Toxoplasma gondii with other pathogens in almost any type of animal cell are considered. The reactivation of latent pathogens and the acceleration of T-cell exhaustion for the second pathogen can explain several puzzling aspects of viral epidemics, such as COVID-19 and their unusual comorbidity mortality rates and post-infection symptoms.

Long COVID and the cardiovascular system - elucidating causes and cellular mechanisms in order to develop targeted diagnostic and therapeutic strategies: A joint Scientific Statement of the ESC Working Groups on Cellular Biology of the Heart and Myocardial & Pericardial Diseases

Long COVID has become a world-wide, non-communicable epidemic, caused by long-lasting multi-organ symptoms that endure for weeks or months after SARS-CoV-2 infection has already subsided. This scientific document aims to provide insight into the possible causes and therapeutic options available for the cardiovascular manifestations of long COVID. In addition to chronic fatigue, which is a common symptom of long COVID, patients may present with chest pain, ECG abnormalities, postural orthostatic tachycardia, or newly developed supraventricular or ventricular arrhythmias. Imaging of the heart and vessels has provided evidence of chronic, post-infectious peri-myocarditis with consequent left or right ventricular failure, arterial wall inflammation or micro-thrombosis in certain patient populations. Better understanding of the underlying cellular and molecular mechanisms of long COVID will aid in the development of effective treatment strategies for its cardiovascular manifestations. A number of mechanisms have been proposed, including those involving direct effects on the myocardium, micro-thrombotic damage to vessels or endothelium, or persistent inflammation. Unfortunately, existing circulating biomarkers, coagulation and inflammatory markers, are not highly predictive for either the presence or outcome of long COVID when measured 3 months after SARS-CoV-2 infection. Further studies are needed to understand underlying mechanisms, identify specific biomarkers and guide future preventive strategies or treatments to address long COVID and its cardiovascular sequelae.

NK-Cell Exhaustion, B-Cell Exhaustion and T-Cell Exhaustion - the Differences and Similarities

T-cell exhaustion has been extensively researched, compared to B-cell exhaustion and NK-cell exhaustion, which have received considerably less attention; and there is less of a consensus on the precise definitions of NK-cell and B-cell exhaustion. NK-cell exhaustion, B-cell exhaustion and T-cell exhaustion are examples of lymphocyte exhaustion, and they have several differences and similarities. Lymphocyte exhaustion is also frequently confused with anergy, cellular senescence and suppression, because these conditions can have significant overlapping similarities with exhaustion. An additional source of confusion is due to the fact that lymphocyte exhaustion is not a binary state, but instead has a spectrum of severity induced by different levels and durations of continuous antigenic stimulation. Concurrent multiple types of lymphocyte exhaustion are possible, and this situation is henceforth called poly-lymphocyte exhaustion. Poly-lymphocyte exhaustion for the same cancer or pathogen would be especially dangerous. Since there are significant advantages for a pathogen by inducing poly-lymphocyte exhaustion in an immune system, there are pathogens with an evolved capability to induce poly-lymphocyte exhaustion. These pathogens may include certain manipulative viruses, bacteria, fungi and protozoan parasites.

The link between Toxoplasma gondii infections and higher mortality in COVID-19 patients having schizophrenia

A strong link between schizophrenia and a higher mortality rate from SARS-CoV-2 infections has been reported for schizophrenia patients, with a mortality odds ratio (OR) of 2.67 compared to normal patients, after adjustment of the OR for age, sex, race and extra risk factors. In addition, an extensive number of papers have reported a very strong link between schizophrenia and Toxoplasma gondii infections. A meta-analysis of 38 studies of links between schizophrenia and T. gondii antibody seroprevalence resulting from previous infections indicated that the likelihood of T. gondii infection in schizophrenia patients was 2.7 times higher than the general population. In other words, the meta-analysis indicated that schizophrenia patients had an odds ratio of 2.7 of T. gondii infection compared to the general population. This indicates that compared to the general population, schizophrenia patients have virtually the same odds ratio for having a T. gondii infection and for mortality from a COVID-19 infection. This suggests that T. gondii infections, directly or indirectly, have a relationship with higher mortality in COVID-19 patients having schizophrenia. This conclusion would also apply to the general population.

The role of polyspecific T-cell exhaustion in severe outcomes for COVID-19 patients having latent pathogen infections such as Toxoplasmagondii

Various categories of coronavirus disease 19 (COVID-19) patients have exhibited major mortality rate differences and symptoms. Some papers have recently explained these differences in mortality rates and symptoms as a consequence of this virus infection acting in synergy with one or more latent pathogen infections in some patients. A latent pathogen infection likely to be involved in millions of these patients is the protozoan parasite Toxoplasma gondii, which infects approximately one third of the global human population. However, other papers have concluded that latent protozoan parasite infections can reduce the severity of viral infections. The aims and purposes of this paper include providing explanations for the contradictions between these studies and introducing a significant new category of T-cell exhaustion. Latent pathogens can have different genetic strains with great differences in their effects on a second pathogen infection. Furthermore, depending on the timing and effectiveness of drug treatments, pathogen infections that become latent may or may not later induce immune cell dysfunctions, including T-cell exhaustion. Concurrent multiple pathogen T-cell exhaustion is herein called "polyspecific T-cell exhaustion."

l-Arginine and COVID-19: An Update

l-Arginine is involved in many different biological processes and recent reports indicate that it could also play a crucial role in the coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Herein, we present an updated systematic overview of the current evidence on the functional contribution of L-Arginine in COVID-19, describing its actions on endothelial cells and the immune system and discussing its potential as a therapeutic tool, emerged from recent clinical experimentations.