The clinical signs of COVID-19 range greatly, from moderate to severe cases of atypical pneumonia, with some developing acute respiratory distress syndrome (ARDS), which frequently necessitates invasive mechanical ventilation and is the major cause of mortality. The severity of the respiratory disease caused by SARS-CoV-2 is thought to be largely owing to an increased immunological response to the virus and CCS[5, 30–33].
Oxidative stress is a feature of COVID-19 disease, which is connected to the CSS seen in the patients with severe COVID-19[34, 35]. Selenium is essential to boost immunity, lower oxidative stress and prevent viral infections, resulting in amelioration of severe diseases[18]. As a result, selenium supplementation can be used as a supportive treatment for COVID-19 infection, and various researches have therefore looked into justification for randomized, controlled trials of selenium supplementation in the disease caused by SARS-CoV-2[18, 36, 37].
On the other hand, iron is a vital trace element both for humans and virus including coronaviruses. Numerous studies have shown that iron is necessary for viral infections and appears to be critical for the replication of SARS-CoV and MERS-CoV as well[38]. In viral infections, changes occur in the body's iron metabolism aiming to seize iron and limit the virus access to this vital metal. However, these events, which are centered on proinflammatory cytokines including IL-6, lead to altered iron metabolism and increased oxidative stress via the Fenton reaction, which results in ferroptosis and the continuation of oxidative harm to biomolecules that finally damage the organs in the body[39, 40] .
In fact, inflammation, oxidative stress and altered iron homeostasis are inextricably connected at a systemic level[41]. This viewpoint emphasizes the possible role of altered iron homeostasis as well as its potential significance in COVID-19 pathogenesis and management strategies[42, 43]. Surprisingly, in the natural immunity of the body, there are iron chelators whose antiviral effects are proved in numerous studies. Lactoferrin (Lf) is a widely distributed glycoprotein generated by a variety of mucosal epithelial cells and is an important component of the natural immunity. This protein has the ability to chelate iron and its antiviral capacity is demonstrated in previous studies[44], and even several researches have discussed its potential for antiviral therapy in COVID-19 patients.
As a result, in view of the vital role of this element for hemoglobin synthesis and other physiological processes, iron chelation therapy can be used as a strategy for managing iron dis-homeostasis with the aim of iron redistribution and sequestration to make iron inaccessible to viruses, while preventing its excretion. It should be noted that the existing iron chelators have many limitations making them incapable of such smart therapeutic behavior. Amongst the existing chelators, deferiprone has shown higher capability to redistribute iron in various experiments [45, 46]. However, although the existing iron chelators have demonstrated promising impacts on viral diseases - mostly in vitro & rarely clinical studies - they are not yet nominated as serious operational candidates for the treatment of viral diseases due to their side effects & structural limitations. These limitations are to such an extent - even in their specific field of application (i.e., iron excretion in diseases caused by iron overload) - that there is a serious need for safer & more efficient chelators[47].
In the previous studies, we reported the successful effects of BCc1 nanochelating-based iron chelator in animal and clinical studies. This nanomedicine increased the survival and quality of life of metastatic and non-metastatic gastric cancer patients without any side effects[21, 48] and showed nephroprotective and antioxidative effects in the animal model of chronic kidney disease[22]
Given the proved impact of iron and selenium on the antiviral performance of the immune system and in light of the results of the previously reported study on BCc1 nanomedicine, the safety and immunomodulatory effect of the combination of BCc1 and selenium-containing Hep-S nanomedicines on hospitalized COVID-19 patients were evaluated in the current study.
The results showed that adding the combination therapy of BCc1 and Hep-S nanomedicines to the standard treatment regimen of hospitalized COVID-19 patients had no negative effect on their hematological characteristics. As explained in the results section, the characteristics linked to the physiological function of iron, such as hemoglobin, red blood cell count and hematocrit, were assessed in this study, and the results showed that despite the iron chelating property of BCc1, the combination therapy of BCc1 and Hep-S had no negative impact on the indices. The results of this study were in line with the results of the study on gastric cancer patients conducted by Hafizi et al., demonstrating that the 18-month consumption of BCc1 nanomedicine had no negative effect on hematological indices compared to the placebo group[21] .
Studies have reported increase in the plasma levels of IL-6 and TNF-alpha in hospitalized COVID-19 patients[49]. The higher level of IL-6 concentration is closely related with the requirement for ventilatory assistance and the development of respiratory failure[50]. Suppressing this cytokine therefore results in managing clinical symptoms, shortening hospitalization period and decreasing need for oxygen therapy[51]. According to the CSS pathogenesis in COVID-19, immunomodulatory therapy can be a proper consideration in this disease[52]. Immunomodulatory medications, which operate by modifying or harnessing the immune responses, come with a number of disadvantages and side effects that can negatively impact patients' quality of life. Unwanted side effects, such as severe infections, cytokine release syndrome, anaphylaxis and hypersensitivity as well as immunogenicity, make developing novel and safer immunomodulatory structures difficult[53, 54].
Since IL-6 is a relevant cytokine in acute respiratory distress syndrome, the blockade of its receptor with tocilizumab (TCZ) in COVID-19 patients has been evaluated in numerous studies. Some showed the beneficial effect of this medicine on reducing mortality rate and hospitalization time[55], while several experiments showed its failure[56] and even did not support its use for the management of cytokine storm in COVID-19 patients[57]. Also, several studies reported that the incidence of infectious complications in patients receiving TCZ was higher than in patients receiving standard therapies[55].
In the present study, consuming the combination of BCc1 and Hep-S nanomedicines for 28 days reduced IL-6 cytokine significantly and could also reduce the numeral value of TNF-α. In addition, the comparison of the treatment and placebo groups showed that these two nanomedicines could decrease IL-6/IFN-γ ratio; the higher this ratio is, the more serious the CSS and damage to lungs will be[58]. Moreover, at the end of the treatment period, the percentage of NK cells in the treatment group was numerically lower, and the level of IgM antibody had a decreasing trend compared to the placebo. These results could be therefore attributed to the regulatory effect of the nanomedicines on the immune system to accelerate passing through acute inflammatory phase[59].
There was no significant difference between the treatment and placebo groups in terms of hospitalization period. As this study was conducted at the second peak of COVID-19 disease, the patients were discharged from the hospital as soon as their standard treatment period (remdesivir, etc.) was finished so that new COVID-19 patients could be admitted to the hospital. As a result of this, it was practically impossible to compare the hospitalization period of the patients in both groups. The results also showed that there were two death cases in the treatment group and three in the placebo.
Moreover, none of the observed clinical symptoms deteriorated in the treatment patients, and they also showed less need for oxygen therapy, leading to higher satisfaction in the treatment group compared to the placebo. Therefore, the combination therapy of BCc1 and Hep-S along with the standard protocol showed no adverse effects and yet had immunomodulatory impacts. One reason for the immunomodulatory effect of these two nanomedicines, without causing any side effects - abnormal changes in blood haemato- and biochemical parameters, negative clinical symptoms, etc. - during 28 days of consumption, is their smart impact on the metabolism of two vital elements of iron and selenium by benefiting from their unique high-tech structure.
Studies show that iron chelation exhibits antiviral and immunomodulatory effects in vitro[60] and in vivo, can attenuate ARDS and help control SARS-CoV-2[42]. In addition, there is a risk of selenium insufficiency in immunopathological conditions, and as a result of this, blood selenium levels are more likely to decline. According to studies, serum IL-6 concentrations are inversely linked to serum selenium[61, 62]. Selenium-deficient cells generate more IL-6 in human bronchial epithelial cell lines infected with influenza virus[63]. There is also evidence that selenium supplementation can reduce excessive cytokine production[64]. As selenium status influences SARS-CoV-2 infection–induced immunopathogeneses, maintaining optimal selenium intake seems vital. Furthermore, studies suggest that selenium status is related to mortality and cure rate of COVID-19 patients[65–68]. There has been evidence of rise in cure rate after selenium intake due mainly to the induction of optimal levels of production and activation of selenoprotein with various functions including antioxidative, anti-inflammatory, immunomodulatory and cellular redox homeostasis maintenance, which help combat COVID-19 pathophysiological events[36].
The previous studies on nanochelating-based structures have evaluated and proved the immunomodulatory effects of these structures. In an animal model of multiple sclerosis as an autoimmune disorder, Fakharzadeh et al. showed that MSc1 nanochelating-based iron chelator could prompt therapeutic behavior, improve the disabling features of experimental autoimmune encephalomyelitis and decrease lymphocyte infiltration in central nervous system[23]. In another study, selenium and zinc-containing DIBc metal organic framework demonstrated antidiabetic effects and lowered TNF-α level efficiently[69] .
Thus, it seems that the nanochelating technology has presented a new generation of immunomodulators with unique structures that do not suffer from limitations such adverse reactions.