Mucosal COVID-19 vaccines: Risks, benefits and control of the pandemic

Based on mucosal immunization to promote both mucosal and systemic immune responses, next-generation coronavirus disease 2019 (COVID-19) vaccines would be administered intranasally or orally. The goal of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines is to provide adequate immune protection and avoid severe disease and death. Mucosal vaccine candidates for COVID-19 including vector vaccines, recombinant subunit vaccines and live attenuated vaccines are under development. Furthermore, subunit protein vac-cines and virus-vectored vaccines have made substantial progress in preclinical and clinical settings, resulting in SARS-CoV-2 intranasal vaccines based on the previously successfully used nasal vaccines. Additional to their ability to trigger stable, protective immune responses at the sites of pathogenic infection, the development of ‘specific’ mucosal vaccines targeting coronavirus antigens could be an excellent option for preventing future pandemics. However, their efficacy and safety should be confirmed.

Acute kidney injury and electrolyte disorders in COVID-19

Acute kidney injury (AKI) and electrolyte disorders are important complications of hospitalized coronavirus disease 2019 (COVID-19) patients. AKI is thought to occur due to multiple pathophysiological mechanisms, such as multiple organ dysfunction (mainly cardiac and respiratory), direct viral entry in the renal tubules, and cytokine release syndrome. AKI is present in approximately one in every ten hospitalized COVID-19 patients. The incidence rates of AKI increase in patients who are admitted to the intensive care unit (ICU), with levels higher than 50%. Additionally, renal replacement therapy (RRT) is used in 7% of all AKI cases, but in nearly 20% of patients admitted to an ICU. COVID-19 patients with AKI are considered moderate-to-severe cases and are managed with multiple interdisciplinary conducts. AKI acts as a risk factor for mortality in severe acute respiratory syndrome coronavirus 2 infection, especially when RRT is needed. Electrolyte disorders are also common manifestations in hospitalized COVID-19 patients, mainly hyponatremia, hypokalemia, and hypocalcemia. Hyponatremia occurs due to a combination of syndrome of inappropriate secretion of antidiuretic hormone and gastrointestinal fluid loss from vomiting and diarrhea. When it comes to hypokalemia, its mechanism is not fully understood but may derive from hyperaldosteronism due to renin angiotensin aldosterone system overstimulation and gastrointestinal fluid loss as well. The clinical features of hypokalemia in COVID-19 are similar to those in other conditions. Hypocalcemia is the most common electrolyte disorder in COVID-19 and seems to occur because of vitamin D deficiency and parathyroid imbalance. It is also highly associated with longer hospital and ICU stay.

Manifestations of COVID-19 infection in children with malignancy: A single-center experience in Jordan

BACKGROUND

The coronavirus disease 2019 (COVID-19) has been the cause of a global health crisis since the end of 2019. All countries are following the guidelines and re-commendations released by the World Health Organization to decrease the spread of the disease. Children account for only 3%-5% of COVID-19 cases. Few data are available regarding the clinical course, disease severity, and mode of treatment in children with malignancy and COVID-19.

AIM

To evaluate the treatment plan and outcome of children with malignancy who contracted COVID-19.

METHODS

A retrospective study of the medical files of patients with malignancy who contracted COVID-19 between July 2020 and June 2021 was performed. The following data were reviewed for all patients: primary disease, laboratory data, admission ward, clinical status upon admission, disease course, treatment plan, and outcome. Eligible patients were those with malignancy who tested positive for COVID-19 by reverse transcription polymerase chain reaction.

RESULTS

A total of 40 patients who had malignancy contracted COVID-19 from July 1, 2020 to June 1, 2021. Their primary diseases were as follows: 34 patients (85%) had hematological malignancies (30 had acute lymphoblastic leukemia, 2 had acute myeloblastic leukemia, and 2 had Hodgkin lymphoma), whereas 6 patients (15%) had solid tumors (2 had neuroblastoma, 2 had rhabdomyosarcoma, and 2 had central nervous system tumors). Twelve patients (30%) did not need hospitalization and underwent home isolation only, whereas twenty-eight patients (70%) required hospitalization (26 patients were admitted in the COVID-19 ward and 2 were admitted in the pediatric intensive care unit).

CONCLUSION

COVID-19 with malignancy in the pediatric age group has a benign course and does not increase the risk of having severe infection compared to other children.

Management of SARS-CoV-2 infection is a major challenge in patients with lymphoid malignancies: Warrants a clear therapeutic strategy

Patients with lymphoid malignancies are at a higher risk of coronavirus disease 2019 (COVID-19) infection due to their immunocompromised state and results in higher mortality rates in these patients. Anti-CD 20 therapy is one of the leading causes of immunosuppression that worsens in COVID-19 cases. COVID-19 vaccines, on the other hand, appear to be less beneficial to these patients. App-ropriate treatment and recommendations are required for these COVID-19 patients with lymphoid malignancies.

Cautious optimism in anticipation of hepatitis B curative therapies

Despite relative effectiveness of current hepatitis B therapies, there is still no curative agents available. The new emerging approaches hold promise to achieve cure and loss of hepatitis B surface antigen. Studies or clinical trials investigating new therapies remain small and either focus on patients with low viral load and without hepatotoxic injury or patients with hepatitis D co-infection, which makes it challenging to assess their effectiveness and side effect profile in hepatitis B population.

COVID-19 presenting with persistent hiccup and myocardial infarction in a peritoneal dialysis patient: A case report

BACKGROUND

Persistent hiccups, lasting more than 48 h, have been described as an atypical presentation of coronavirus disease 19 (COVID-19) in the general population. To the best of our knowledge, this is the first report of persistent hiccups and non-ST elevation myocardial injury (NSTEMI) as an atypical presentation of COVID-19 in a peritoneal dialysis (PD) patient.

CASE SUMMARY

A 70-year old man, who had been on PD for 3 years with a history of ischemic heart failure and reduced ejection fraction, presented for a scheduled radionuclide myocardial scan. Upon arrival, he complained of anorexia, nausea for 5 d, and unremitting hiccups for the previous 48 h. Clinical and laboratory examinations revealed an NSTEMI plus a positive nasopharyngeal reverse transcriptase polymerase chain reaction testing for severe acute respiratory syndrome coronavirus 2. COVID-19 lung involvement was mild and was resolved without specific treatment. Myocardial injury was managed by coronary catheterization and stenting, while hiccups responded only to baclofen per os.

CONCLUSION

Persistent hiccups and NSTEMI can be atypical presentations of COVID-19 in peritoneal dialysis patients, which may be due to involvement of the central nervous system and myocardial injuries.

Air leaks in COVID-19

Coronavirus disease 2019 (COVID-19) continues to create havoc and may present with myriad complications involving many organ systems. However, the respiratory system bears the maximum brunt of the disease and continues to be most commonly affected. There is a high incidence of air leaks in patients with COVID-19, leading to acute worsening of clinical condition. The air leaks may develop independently of the severity of disease or positive pressure ventilation and even in the absence of any traditional risk factors like smoking and un-derlying lung disease. The exact pathophysiology of air leaks with COVID-19 remains unclear, but multiple factors may play a role in their development. A significant proportion of air leaks may be asymptomatic; hence, a high index of suspicion should be exercised for enabling early diagnosis to prevent further deterioration as it is associated with high morbidity and mortality. These air leaks may even develop weeks to months after the disease onset, leading to acute deterioration in the post-COVID period. Conservative management with close monitoring may suffice for many patients but most of the patients with pneumothorax may require intercostal drainage with only a few requiring surgical interventions for persistent air leaks.

“Heart failure in COVID-19 patients: Critical care experience”: A letter to the editor

Coronavirus disease 2019 (COVID-19) is associated with poor cardiovascular outcomes in patients with heart failure (HF) of all categories of ejection fraction (EF), but mainly in patients with HF with reduced EF. Moreover, cardiac transplant patients exhibit worse cardiovascular prognosis, high mortality, and more admissions to the intensive care unit. In general, COVID-19 seems to de-teriorate the clinical status of HF and favors the development of acute respiratory distress syndrome and multiorgan failure, especially in the presence of cardiovascular comorbidities such as diabetes mellitus, kidney dysfunction, and older age. COVID-19 may induce new-onset HF with complex mechanisms that involve myocardial injury. Indeed, myocardial injury comprises a large category of detrimental effects for the myocardium, such as myocardial infarction type 1 or type 2, Takotsubo cardiomyopathy, microvascular dysfunction and myocarditis, which are not easily distinguished by HF. The pathophysiologic mechanisms mainly involve direct myocardial damage by severe acute respiratory syndrome coronavirus 2, cytokine storm, hypercoagulation, inflammation, and endothelial dysfunction. The proper management of patients with COVID-19 involves careful patient evaluation and ongoing monitoring for complications such as HF.

COVID-19 vaccination and myocarditis: A review of current literature

Vaccination for coronavirus disease 2019 (COVID-19) is a critical strategy in controlling the current pandemic of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). After widespread COVID-19 vaccine imple-mentation, isolated case reports about myocarditis as a potential adverse reaction started coming. As of November 12, 2021, Centers for Disease Control and Prevention (CDC) has reported 1793 cases of myocarditis or pericarditis among young people with age 12-29 years, most cases have been reported in the male adolescent age group after the second dose of mRNA COVID-19 vaccines. It is very important to monitor the safety standards and adverse reactions of vaccines to effectively implement the vaccination policies. The CDC and the United States Food and Drug Administration actively monitor vaccine-associated adverse reactions a well-known platform such as Vaccine Adverse Event Reporting System. CDC continues to recommend COVID-19 vaccines and booster doses for eligible individuals (age limit according to the type of vaccine) after careful consideration from risk-benefit assessment and favorable outcomes from vaccination. Mechanisms behind COVID-19 vaccine-induced myocarditis are not clear yet but several possibilities such as molecular mimicry between the spike protein of SARS-CoV-2 and self-antigens, immune response to mRNA, and activation of host immunological system, trigger of the pre-existing dysregulated immunological system have been documented in the literature. Overall, data suggests a good prognosis, especially in young patients. In this review article, we cover currently available data on COVID-19 vaccine-related myocarditis incidence, concerns, possible mechanisms of myocarditis, current treatment, and outcome trends, risk vs benefit assessment of COVID-19 vaccination in this current pandemic.

COVID-19 pandemic effects on the distribution of healthcare services in India: A systematic review

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic has brought fundamental changes to our problems and priorities, especially those related to the healthcare sector. India was one of the countries severely affected by the harsh consequences of the COVID-19 pandemic.

AIM

To understand the challenges faced by the healthcare system during a pandemic.

METHODS

The literature search for this review was conducted using PubMed, EMBASE, Scopus, Web of Science, and Google Scholar. We also used Reference Citation Analysis (RCA) to search and improve the results. We focused on the published scientific articles concerned with two major vital areas: (1) The Indian healthcare system; and (2) COVID-19 pandemic effects on the Indian healthcare system.

RESULTS

The Indian healthcare system was suffering even before the pandemic. The pandemic has further stretched the healthcare services in India. The main obstacle in the healthcare system was to combat the rising number of communicable as well as noncommunicable diseases. Besides the pandemic measures, there was a diversion of focus of the already established healthcare services away from the chronic conditions and vaccinations. The disruption of the vaccination services may have more severe short and long-term consequences than the pandemic’s adverse effects.

CONCLUSION

Severely restricted resources limited the interaction of the Indian healthcare system with the COVID-19 pandemic. Re-establishment of primary healthcare services, maternal and child health services, noncommunicable diseases programs, National Tuberculosis Elimination Program, etc. are important to prevent serious long-term consequences of this pandemic.

Chemsex and its risk factors associated with human immunodeficiency virus among men who have sex with men in Hong Kong

We were intrigued by Hanum et al, who published a study on the prevalence of human immunodeficiency virus (HIV) in homosexual, bisexual, and other men who have sex with men at sexual health clinics in England and the relationship between baseline variables and future HIV occurrence. Chemically-enhanced sexual experience (chemsex) is becoming a global phenomenon. There are increasing medical and academic concerns about chemsex, where substances are used to boost sexual satisfaction, which is prevalent in groups, especially among homosexuals. Lesbians, gays, bisexuals, transgenders, and queers have become increasingly visible, valued, and committed community. However, chemsex requires urgent attention.

SARS-CoV-2 Omicron variant (B.1.1.529): A concern with immune escape

Omicron, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant that is now spreading across the world, is the most altered version to emerge so far, with mutations comparable to changes reported in earlier variants of concern linked with increased transmissibility and partial resistance to vaccine-induced immunity. This article provides an overview of the SARS-CoV-2 variant Omicron (B.1.1.529) by reviewing the literature from major scientific databases. Although clear immunological and clinical data are not yet available, we extrapolated from what is known about mutations present in the Omicron variant of SARS-CoV-2 and offer preliminary indications on transmissibility, severity, and immune escape through existing research and databases.

Severe acute respiratory syndrome coronavirus 2 infection: Role of interleukin-6 and the inflammatory cascade

Since December 2019, a novel coronavirus that represents a serious threat to human lives has emerged. There is still no definite treatment for severe cases of the disease caused by this virus, named coronavirus disease 2019 (COVID-19). One of the most considered treatment strategies targets the exaggerated immune regulator, and interleukin (IL)-6 is a crucial pro-inflammatory mediator. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cases show an elevated level of IL-6 related to disease severity. IL-6 activity can be inhibited by the following: IL-6 itself, IL-6 signaling pathways such as Janus kinase and signal transducer and activator of transcription (JAK-STAT), gp130, IL-6R, and downstream activated ILs, such as IL-17 and IL-6 cytokine. Currently, according to these studies and their results, IL-6 blockade with anti-IL-6 or its receptor antibodies such as tocilizumab in COVID-19 is beneficial in severe cases and may reduce the mortality rate. JAK-STAT inhibitors block the cytokine storm by inhibiting several crucial pro-inflammatory mediators such as TNF-α and IL-6 and have shown various results in clinical trials. IL-6 induces IL-17 secretion, and IL-17 is involved in the pathogenesis of inflammatory processes. Clinical trials of anti-IL-17 drugs are currently recruiting, and anti-gp130 antibody is preclinical. However, this agent has shown positive effects in inflammatory bowel disease clinical trials and could be tested for SARS-CoV-2. This study aimed to review the role of IL-6 in the cytokine storm and studies regarding IL-6 and blockade of its inflammatory pathways in COVID-19 to determine if any of these agents are beneficial for COVID-19 patients.

Educational, psychosocial, and clinical impact of SARS-CoV-2 (COVID-19) pandemic on medical students in the United States

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic altered education, exams, and residency applications for United States medical students.

AIM

To determine the specific impact of the pandemic on US medical students and its correlation to their anxiety levels.

METHODS

An 81-question survey was distributed via email, Facebook and social media groups using REDCap^TM. To investigate risk factors associated with elevated anxiety level, we dichotomized the 1-10 anxiety score into low (≤ 5) and high (≥ 6). This cut point represents the 25^th percentile. There were 90 (29%) shown as low anxiety and 219 (71%) as high anxiety. For descriptive analyses, we used contingency tables by anxiety categories for categorical measurements with chi square test, or mean ± STD for continuous measurements followed by t-test or Wilcoxson rank sum test depending on data normality. Least Absolute Shrinkage and Selection Operator was used to select important predictors for the final multivariate model. Hierarchical Poisson regression model was used to fit the final multivariate model by considering the nested data structure of students clustered within State.

RESULTS

397 medical students from 29 states were analyzed. Approximately half of respondents reported feeling depressed since the pandemic onset. 62% of participants rated 7 or higher out of 10 when asked about anxiety levels. Stressors correlated with higher anxiety scores included “concern about being unable to complete exams or rotations if contracting COVID-19” (RR 1.34; 95%CI: 1.05-1.72, P = 0.02) and the use of mental health services such as a “psychiatrist” (RR 1.18; 95%CI: 1.01-1.3, P = 0.04). However, those students living in cities that limited restaurant operations to exclusively takeout or delivery as the only measure of implementing social distancing (RR 0.64; 95%CI: 0.49-0.82, P < 0.01) and those who selected “does not apply” for financial assistance available if needed (RR 0.83; 95%CI: 0.66-0.98, P = 0.03) were less likely to have a high anxiety.

CONCLUSION

COVID-19 significantly impacted medical students in numerous ways. Medical student education and clinical readiness were reduced, and anxiety levels increased. It is vital that medical students receive support as they become physicians. Further research should be conducted on training medical students in telemedicine to better prepare students in the future for pandemic planning and virtual healthcare.

Omicron variant and change of electrostatic interactions between receptor binding domain of severe acute respiratory syndrome coronavirus 2 with the angiotensin-converting enzyme 2 receptor

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are currently a new hazard. Since the first appearance of classical SARS-CoV-2 in late 2019, pathogen genetic alterations have continued to occur, and some new hazardous forms have already emerged. The underlying pathophysiological process leading to clinical issue is molecular change caused by genetic mutation.

AIM

To determine the change in the interaction between receptor binding domain of omicron variant SARS-CoV-2 and the angiotensin-converting enzyme 2 (ACE2).

METHODS

The researchers investigated how alterations in the binding area of the SARS receptor CoV2 interacted electrostatically with the ACE2 receptor. In this report, three important coronavirus disease 2019 variants, beta, delta, and omicron, were investigated.

RESULTS

According to this study, there was a change of electrostatic interactions between the receptor binding domain of SARS-CoV-2 with the ACE2 receptor due to each studied variant. The most change was detected in omicron variant followed by delta variant and beta variant.

CONCLUSION

Our results may support the clinical finding that the omicron variant is more transmissible than the wild type and other variants.

Impact of COVID-19 on mental health and emotional well-being of older adults

Older adults faced unique challenges in the pandemic due to their increased vulnerability to coronavirus disease 2019 (COVID-19) and its complications. Pandemic-related restrictions such as physical distancing, stay-at-home orders, lock-down, and mandatory face cover affected older adults in unique ways. Additionally, older adults experienced psychosocial concerns related to discrimination based on ageism and emotional distress from exposure to conflicting messages in the media. They experienced several forms of loss and associated grief and survivor guilt. Pandemic added to their loneliness and social isolation. Furthermore, older adults experienced the fear and anxiety related to COVID and the fear of contracting the disease and dying from it. Pandemic experience included events potential to generate the desire and capability for suicide. Several studies report varying symptoms such as loneliness, anxiety, and depression among older adults during the pandemic. However, during the initial months of the pandemic, there were reports on coping and resilience among this population. The impact of COVID-19 on older adults’ mental health may have long-term implications. This narrative review examines the impact of COVID-19 on older adults’ mental health and psychosocial wellbeing. Additionally, the review highlights various factors that affected their psychosocial wellbeing during the COVID-19 pandemic.

Rifampicin for COVID-19

Vaccinations for coronavirus disease-2019 (COVID-19) have begun more than a year before, yet without specific treatments available. Rifampicin, critically important for human medicine (World Health Organization’s list of essential medicines), may prove pharmacologically effective for treatment and chemoprophylaxis of healthcare personnel and those at higher risk. It has been known since 1969 that rifampicin has a direct selective antiviral effect on viruses which have their own RNA polymerase (severe acute respiratory syndrome coronavirus 2), like the main mechanism of action of remdesivir. This involves inhibition of late viral protein synthesis, the virion assembly, and the viral polymerase itself. This antiviral effect is dependent on the administration route, with local application resulting in higher drug concentrations at the site of viral replication. This would suggest also trying lung administration of rifampicin by nebulization to increase the drug’s concentration at infection sites while minimizing systemic side effects. Recent in silico studies with a computer-aided approach, found rifampicin among the most promising existing drugs that could be repurposed for the treatment of COVID-19.

Bacterial and fungal co-infection is a major barrier in COVID-19 patients: A specific management and therapeutic strategy is required

Microbial co-infections are another primary concern in patients with coronavirus disease 2019 (COVID-19), yet it is an untouched area among researchers. Preliminary data and systematic reviews only show the type of pathogens responsible for that, but its pathophysiology is still unknown. Studies show that these microbial co-infections are hospital-acquired/nosocomial infections, and patients admitted to intensive care units with invasive mechanical ventilation are highly susceptible to it. Patients with COVID-19 had elevated inflammatory cytokines and a weakened cell-mediated immune response, with lower CD4⁺ T and CD8⁺ T cell counts, indicating vulnerability to various co-infections. Despite this, there are only a few studies that recommend the management of co-infections.

Novel appearance of hyperglycemia/diabetes, associated with COVID-19

In a recent meta-analysis the prevalence of coronavirus disease 2019 (COVID-19)-associated hyperglycemia was 25%, and that of COVID-19-associated new-onset diabetes was 19%. An association between hyperglycemia or new-onset diabetes and COVID-19 has been suggested. In a recent relevant study of critically and non-critically ill patients with COVID-19, we found that indeed beta-cell function was compromised in critically ill patients with COVID-19 and that these patients showed a high glycemic gap. Nevertheless, one quarter of critically ill patients with no history of diabetes have stress hyperglycemia, a finding which could obscure the prevalence of hyperglycemia or new-onset diabetes that could be attributed to COVID-19 per se.

Too hard to die: Exercise training mediates specific and immediate SARS-CoV-2 protection

Several mechanisms may explain how exercise training mechanistically confers protection against coronavirus disease 2019 (COVID-19). Here we propose two new perspectives through which cardiorespiratory fitness may protect against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Physical exercise-activated adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling induces endothelial nitric oxide (NO) synthase (eNOS), increases NO bio-availability, and inhibits palmitoylation, leading to specific and immediate SARS-CoV-2 protection. AMPK signaling also induces angiotensin 1-7 release and enhances eNOS activation thus further mediating cardio- and reno-protection. Irisin, a myokine released from skeletal muscles during aerobic exercise, also participates in the AMPK/Akt-eNOS/NO pathway, protects mitochondrial functions in endothelial cells, and antagonizes renin angiotensin system proinflammatory action leading to reductions in genes associated with severe COVID-19 outcomes. Collectively, all the above findings point to the fact that increased AMPK and irisin activity through exercise training greatly benefits molecular processes that mediate specific, immediate, and delayed SARS-CoV-2 protection. Maintaining regular physical activity levels is a safe and affordable lifestyle strategy against the current and future pandemics and may also mitigate against obesity and cardiometabolic disease syndemics. Move more because a moving target is harder to kill.

Therapeutic potential of N-acetyl cysteine during COVID-19 epoch

N-acetyl cysteine (NAC) is a promising drug for prophylaxis and treatment of coronavirus disease 2019 (COVID-19) based on antioxidant and anti-inflammatory mechanisms. Further studies with cautious approach are needed to establish the benefits and risks before considering NAC as an adjuvant treatment for COVID-19.

COVID-19: A pluralistic and integrated approach for efficient management of the pandemic

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which triggered the ongoing pandemic, was first discovered in China in late 2019. SARS-CoV-2 is a respiratory virus responsible for coronavirus disease 2019 (COVID-19) that often manifests as a pneumonic syndrome. In the context of the pandemic, there are mixed views on the data provided by epidemiologists and the information collected by hospital clinicians about their patients. In addition, the literature reports a large proportion of patients free of pneumonia vs a small percentage of patients with severe pneumonia among confirmed COVID-19 cases. This raises the issue of the complexity of the work required to control or contain the pandemic. We believe that an integrative and pluralistic approach will help to put the analyses into perspective and reinforce collaboration and creativity in the fight against this major scourge. This paper proposes a comprehensive and integrative approach to COVID-19 research, prevention, control, and treatment to better address the pandemic. Thus, this literature review applies a pluralistic approach to fight the pandemic.

Chronic hepatitis B: New potential therapeutic drugs target

Chronic hepatitis B (CHB) infection remains the most causative agent of liver-related morbidity and mortality worldwide. It impacts nearly 300 million people. The current treatment for chronic infection with the hepatitis B virus (HBV) is complex and lacks a durable treatment response, especially hepatitis B surface antigen (HBsAg) loss, necessitating indefinite treatment in most CHB patients due to the persistence of HBV covalently closed circular DNA (cccDNA). New drugs that target distinct steps of the HBV life cycle have been investigated, which comprise inhibiting the entry of HBV into hepatocytes, disrupting or silencing HBV cccDNA, modulating nucleocapsid assembly, interfering HBV transcription, and inhibiting HBsAg release. The achievement of a functional cure or sustained HBsAg loss in CHB patients represents the following approach towards HBV eradication. This review will explore the up-to-date advances in the development of new direct-acting anti-HBV drugs. Hopefully, with the combination of the current antiviral drugs and the newly developed direct-acting antiviral drugs targeting the different steps of the HBV life cycle, the ultimate eradication of CHB infection will soon be achieved.

Role of vitamin D deficiency and comorbidities in COVID-19

Recent manuscripts described the incidence of vitamin D hypovitaminosis in coronavirus disease 2019 (COVID-19) patients. Vitamin D deficiency is also common in patients with comorbidities that are associated with a poor COVID-19 prognosis. In this letter, we review the literature regarding the association of comorbidities, vitamin D deficiency, and COVID-19.

Animal models for SARS-CoV-2 and SARS-CoV-1 pathogenesis, transmission and therapeutic evaluation

There is a critical need to develop animal models to alleviate vaccine and drug development difficulties against zoonotic viral infections. The coronavirus family, which includes severe acute respiratory syndrome coronavirus 1 and severe acute respiratory syndrome coronavirus 2, crossed the species barrier and infected humans, causing a global outbreak in the 21^st century. Because humans do not have pre-existing immunity against these viral infections and with ethics governing clinical trials, animal models are therefore being used in clinical studies to facilitate drug discovery and testing efficacy of vaccines. The ideal animal models should reflect the viral replication, clinical signs, and pathological responses observed in humans. Different animal species should be tested to establish an appropriate animal model to study the disease pathology, transmission and evaluation of novel vaccine and drug candidates to treat coronavirus disease 2019. In this context, the present review summarizes the recent progress in developing animal models for these two pathogenic viruses and highlights the utility of these models in studying SARS-associated coronavirus diseases.