Immunity, parasites, genetics and sex hormones: contributors to mild inflammatory responses in COVID-19?

The Potential Nexus between Helminths and SARS-CoV-2 Infection: A Literature Review

Chronic helminth infections (CHIs) can induce immunological tolerance through the upregulation of regulatory T cells. In coronavirus disease 2019 (COVID-19), abnormal adaptive immune response and exaggerated immune response may cause immune-mediated tissue damage. Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) and CHIs establish complicated immune interactions due to SARS-CoV-2-induced immunological stimulation and CHIs-induced immunological tolerance. However, COVID-19 severity in patients with CHIs is mild, as immune-suppressive anti-inflammatory cytokines counterbalance the risk of cytokine storm. Since CHIs have immunomodulatory effects, therefore, this narrative review aimed to clarify how CHIs modulate the immunoinflammatory response in SARS-CoV-2 infection. CHIs, through helminth-derived molecules, may suppress SARS-CoV-2 entry and associated hyperinflammation through attenuation of the inflammatory signaling pathway. In addition, CHIs may reduce the COVID-19 severity by reducing the SARS-CoV-2 entry points in the initial phase and immunomodulation in the late phase of the disease by suppressing the release of pro-inflammatory cytokines. In conclusion, CHIs may reduce the severity of SARS-CoV-2 infection by reducing hyperinflammation and exaggerated immune response. Thus, retrospective and prospective studies are recommended in this regard.

Prevalence and factors associated with COVID-19 vaccine acceptance in Zambia: a web-based cross-sectional study

Introduction

vaccinations against COVID-19 have been instituted to contain the pandemic. However, information about the acceptability of COVID-19 vaccines in Zambia is lacking. Therefore, the study assessed the prevalence and factors associated with COVID-19 vaccine acceptance among the general population in Zambia.

Methods

this was an online questionnaire-based cross-sectional study conducted from 13^th April to 21^st May 2021. We included adult Zambians who had access to Facebook and WhatsApp. A multivariable logistic regression model was fitted to determine factors influencing vaccine acceptability. Data were analysed using Stata version 16.1.

Results

of the 677 participants, only 33.4% (n = 226) would accept the vaccine if made available to them. In multivariable regression analysis, respondents who were older than 41 years compared to the 18 to 23 years age group (aOR: 2.77, 95% CI: 1.03-7.48), those who agreed (aOR; 22.85, 95% CI: 11.49-45.49) or did not know (aOR; 3.73, 95% CI: 2.29-6.07) compared to those who disagreed that the COVID-19 vaccine passed through all the necessary stages to ensure its safety and effectiveness, and those who were aware (aOR; 11.13, 95% CI: 5.31-23.35) compared to those who were not aware that the COVID-19 vaccine reduces virus transmission, were more likely to accept the vaccine. Conversely, entrepreneurs compared to government employees (aOR; 0.24, 95% CI: 0.07-0.79) were less likely to accept vaccination.

Conclusion

awareness of the COVID-19 vaccine was high despite low acceptability levels. These findings are significant as they highlight the need to develop strategies for improving vaccine acceptability in Zambia.

SARS-CoV-2 and helminth co-infections, and environmental pollution exposure: An epidemiological and immunological perspective

Soil-transmitted helminths infect billions of people globally, particularly those residing in low- and middle-income regions with poor environmental sanitation and high levels of air and water pollution. Helminths display potent immunomodulatory activity by activating T helper type 2 (Th2) anti-inflammatory and Th3 regulatory immune responses. The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the virus that causes Coronavirus disease 2019 (COVID-19), can exacerbate Th1/Th17 pro-inflammatory cytokine production in humans, leading to a cytokine storm. Air pollutants (particulate matter, oxygen radicals, hydrocarbons and volatile organic compounds) and water pollutants (metals and organic chemicals) can also intensify Th1/Th17 immune response and could exacerbate SARS-CoV-2 related respiratory distress and failure. The present review focused on the epidemiology of SARS-CoV-2, helminths and fine particulate matter 2.5 µm or less in diameter (PM2.5) air pollution exposure in helminth endemic regions, the possible immunomodulatory activity of helminths against SARS-CoV-2 hyper-inflammatory immune response, and whether air and water pollutants can further exacerbate SARS-CoV-2 related cytokine storm and in the process hinder helminths immunomodulatory functionality. Helminth Th2/Th3 immune response is associated with reductions in lung inflammation and damage, and decreased expression levels of angiotensin-converting enzyme 2 (ACE2) receptors (SARS-CoV-2 uses the ACE2 receptors to infect cells and associated with extensive lung damage). However, air pollutants are associated with overexpression of ACE2 receptors in the epithelial cell surface of the respiratory tract and exhaustion of Th2 immune response. Helminth-induced immunosuppression activity reduces vaccination efficacy, and diminishes vital Th1 cytokine production immune responses that are crucial for combating early stage infections. This could be reversed by continuous air pollution exposure which is known to intensify Th1 pro-inflammatory cytokine production to a point where the immunosuppressive activities of helminths could be hindered. Again, suppressed activities of helminths can also be disadvantageous against SARS-CoV-2 inflammatory response. This "yin and yang" approach seems complex and requires more understanding. Further studies are warranted in a cohort of SARS-CoV-2 infected individuals residing in helminths and air pollution endemic regions to offer more insights, and to impact mass periodic deworming programmes and environmental health policies.

Assessing required SARS-CoV-2 blanket testing rates for possible control of the outbreak in the epicentre Lusaka province of Zambia with consideration for asymptomatic individuals: A simple mathematical modelling study

INTRODUCTION

The novel Coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), in Africa is characterised by a more substantial proportion of asymptomatic (or mildly symptomatic) individuals thought to be playing a role in the spread of the infection. The exact proportion and degree of infectiousness of asymptomatic individuals remains unclear. Studies however indicate that their management is crucial for control of SARS-CoV-2 transmission.

METHODOLOGY

We developed a simplified deterministic susceptible-exposed-infectious-removed (SEIR) mathematical model to assess the effect of active isolation of SARS-CoV-2 infected but asymptomatic individuals through blanket testing for control of the outbreak in Lusaka Province of Zambia. Here we modelled two scenarios; (1) assuming asymptomatic individuals comprised 70% of all COVID-19 cases and (2) asymptomatic individuals comprised only 50% of the cases. For contrast, the model was assessed first under the assumption that asymptomatic individuals are equally as infectious as symptomatic individuals and then secondly, and more likely, assuming asymptomatic individuals are only half as infectious as symptomatic individuals.

RESULTS

For the model assuming 70% asymptomatic cases, a minimum sustained daily blanket testing rate of ≥ 7911 tests/100000 population was sufficient to control the outbreak if asymptomatic individuals are only half as infectious while if equal infectiousness was assumed then a testing rate of ≥ 10028 tests/ 100000 population would be required. For 50% asymptomatic, minimum blanket testing rates of ≥ 4540 tests/ 100000 population was sufficient to control the outbreak at both assumed levels of infectiousness for asymptomatic individuals relative to symptomatic individuals.

DISCUSSION AND CONCLUSION

Our model predicts that active isolation of COVID-19 cases, including asymptomatic individuals, through blanket testing can be used as a possible measure for the control of the SARS-Cov-2 transmission in Lusaka, Zambia, but it would come at a high cost.

Old friends meet a new foe: A potential role for immune-priming parasites in mitigating COVID-19 morbidity and mortality

The novel virus, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and the associated Coronavirus Disease 2019 (COVID-19) represent a pathogen to which human beings have limited to no evolved immune response. The most severe symptoms are associated with overactive inflammatory immune responses, leading to a cytokine storm, tissue damage, and death, if not balanced and controlled. Hypotheses within Evolutionary Medicine, including the Hygiene/Old Friends Hypothesis, provide an important lens through which to understand and possibly control this overactive immune response. In this article, we explore the role that infection with soil-transmitted helminths (STHs; i.e. intestinal parasitic worms) may play in dampening SARS-CoV-2 symptoms and mitigating the worst COVID-19 outcomes. Specifically, STHs stimulate the immunosuppressive and regulatory T-helper 2 (TH2) branch of the immune system, which decreases ACE2-receptor expression (i.e. receptors SARS-CoV-2 uses to infect host cells), balances the inflammatory TH1/TH17 branches of the immune system triggered by SARS-CoV-2 infection, and reduces inflammation through the release of anti-inflammatory/regulatory cytokines. Because STHs are common and affect the most vulnerable and marginalized members of society, it is especially important to consider how these parasites may impact COVID-19 outcomes. Areas experiencing endemic STH infections are often characterized by a lack of preventative infrastructure and medical care, which may further exacerbate risk of SARS-CoV-2 infection and COVID-19 development. For this reason, we also explore biocultural factors that contribute to disease outcomes for both SARS-CoV-2 and STH infections. Biocultural and Evolutionary Medicine perspectives on COVID-19 are crucial for understanding the global impact of the disease. Lay summary: An evolutionary perspective is required to understand the global impact and various presentations of COVID-19. We consider how coinfection with soil-transmitted helminths (common parasitic worms that coevolved with humans) may suppress inflammatory immune activity, thereby potentially reducing COVID-19 disease severity. Structural and lifestyle factors shaping coinfection patterns are also discussed.

Risk perception, public health interventions, and Covid-19 pandemic control in sub-saharan Africa

Coronavirus disease 2019 (COVID 19) has had serious social, economic, and health effects globally. The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2), which was first announced in December 2019 has resulted in more than 24 million infections. There is paucity of knowledge on the role of risk perception in the adoption of public health interventions needed to control the spread of COVID 19 infections within communities. This was a scoping review and documents how risk perception may be a major challenge for populations to adopt and implement different behavioral changes recommended to curtail the spread COVID- 19 pandemic in sub-Saharan Africa; and seeks to proffer solutions on how the identified challenges can be addressed drawing from lessons learnt from previous epidemics within the region. Database search of Google Scholar, PubMed, Research Gate among others were performed using related keywords to identify relevant journals and lists of primary articles. Culture, religious beliefs and poverty may influence how populations respond to infectious disease outbreaks. Risk strategies that focus only on biomedical approaches to control the COVID-19 pandemic may not mobilize the needed behavioral change. Lessons learnt from HIV and Ebola epidemics showed that involvement of communities could help transform weak adoption of public health measures when measures were framed in the relevant cultural context. An understanding of the factors influencing risk perception is needed to design appropriate risk communication strategies. Community engagement and reliance on local communication networks could promote mutual trust and increase the uptake of public-health interventions.