Medical Hypotheses 144 (2020) 110293

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Medical Hypotheses
journal homepage: www.elsevier.com/locate/mehy

Potential role of GcMAF in suppressing the severity of COVID-19-induced
immune responses: Lesson learned from HIV

T

Lucrezia Spaderaa, , Maria Spaderab⁎abDepartment of Otolaryngology-Head and Neck Surgery, Ospedale del Mare, Naples, Italy
Department of Anesthesiology and Intensive Care, San Giovanni Bosco Hospital, Naples, Italy

Introduction
Over the last six months, there have been increasing numbers ofreports that struggle to understand the pathogenesis of the coronavirus
disease 2019 (COVID-19) pandemic.
As of August 16, 2020, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for more than 21 294
000 infections and about 760 000 deaths worldwide [1], but the mechanisms of virus-induced host damage remain a mystery. Understanding the pathways behind viral pathogenicity just like cellular andtissue tropism, counteracting host defence processes and immunological responses are crucial to find new therapeutic strategies.
Based on clinical reports, it is noteworthy that COVID-19 causes various
degree of illness ranging from asymptomatic or milder symptomaticcases to severe lung injury or even multi-organ dysfunction with liverand kidney impairment [2–4]. Even in not severe patients, the heterogeneity of symptoms is consistent with the increasing evidence that
SARS-CoV-2 shows a broad tissue tropism, being able to attack almost
anything in the body [2–5]. To date, the most commonly investigatedhypothesis about the underlying mechanisms of multi-organ failure
may be summarized into three main targets: microcirculation dysfunction, overwhelming inflammation and abnormal coagulation [7].
Radiologic and laboratory findings as well as preliminary autopsy studies seem to support this hypothesis. The most common patterns seen
on chest CT were ground-glass opacity, interlobular septal thickening,
air bronchogram, bilateral patchy shadowing, crazy-paving pattern,
and thickening of the adjacent pleura, resembling an interstitial involvement in viral pneumonia [2,3,7,8]. Under the light of microscope,
the lungs revealed diffuse alveolar damage with formation of numerous
hyaline membranes, very patchy and sparse interstitial chronic inflammation composed mainly of lymphocytes, thrombi within a few
small pulmonary artery branches, congestion of alveolar septal capillaries, focal edema fluid, and macrophage infiltration within the airspaces [9–12]. The more significant laboratory abnormalities were
metabolic acidosis, lymphocytopenia, leukopenia, thrombocytopenia,
elevated levels of C-reactive protein (CRP), interleukin-6 (IL-6), lactate⁎

dehydrogenase (LDH) and D-dimer [2–7]. As firstly suggested by Huang
C et al. [4], the systemic cytokine storm could play a key role in thevirus-induced tissue damage. However, the question “what the link forthe overproduction of pro-inflammatory mediators and the immune
suppression, on the hand, and microvascular injury and thromboembolism, on the other, is”, remains unclear.
Being the knowledge of this issue very scarce, lessons learned fromother human pathogenic viruses, with specific reference to human immunodeficiency virus (HIV), could be diriment.
The hypothesis
Based on the aforementioned findings and on documented analogies
between SARS-CoV-2 and HIV [13], we hypothesized that the reduced
conversion activity of the Gc protein (human group-specific component(Gc)) into the macrophage activating factor (MAF) could have a keyrole in the dysregulate immune response induced by SARS-CoV-2, justlike for HIV infected patients [14,15]. If this hypothesis is correct, it
might help to set a valid strategy of immunotherapy also based on an
off-label use of GcMAF in critically ill COVID-19 patients.
GcMAF and COVID-19: a literature review with a focus on theevaluation of the hypothesis
Gc globulin, DBP and GcMAF: three in one
Serum Gc protein, also known as vitamin D-binding protein (DBP),
is a multifunctional protein present in plasma/serum at concentrationsof 300–600 mg/L [16]. It carries a trisaccharide consisting of N-acetylgalactosamine with dibranched galactose and sialic acid termini at
420 threonine residue [17]. Stepwise hydrolysis of Gc protein by the
inducible membranous β-galactosidase of stimulated B-lymphocytes,
and by the Neu-1 sialidase of T-lymphocytes converts it into the active
GcMAF [17–19]. On the contrary, deglycosilation of Gc protein by action of the enzyme alpha-N-acetylgalactosaminidase, named nagalase,secreted from HIV-infected cells leads to lack of macrophage activationand to immunosuppression, as a consequence [14,15]. It is remarkable

Corresponding author.
E-mail address: lucrezia.spadera@libero.it (L. Spadera).
URL: https://www.aslnapoli1centro.it/ospedale-del-mare (L. Spadera).

https://doi.org/10.1016/j.mehy.2020.110293
Received 18 May 2020; Received in revised form 20 August 2020; Accepted 18 September 2020
Available online 24 September 20200306-9877/ © 2020 Elsevier Ltd. All rights reserved.

Medical Hypotheses 144 (2020) 110293

L. Spadera and M. Spaderathat nagalase was demonstrated to be an intrinsic component not onlyof the envelope glycoproteins gp120 and gp160 of HIV but also of thehemagglutinin (HE) of influenza virus [15,20] and even produced byneoplastic cells [21–23]. Indeed, flu-like symptoms with serum nagalase activity similar to the influenza acute state were reported in theearly stage of HIV-infection, so that the serum enzyme activity may be
detectable at all phases of HIV-infection [14,15]. Similarly, most
COVID-19 patients complained of flu-like symptoms in the early stagesof the disease [2–5].

reported that 71.4% of the non survivors of COVID-19 matched thegrade of overt‐DIC according to the International Society on Thrombosis and Haemostasis (ISTH) diagnostic criteria for DIC.
Murine models deficient in DBP showed lung damage caused byactin polymerization, developing severe acute lung inflammation with
vascular leakage, hemorrhage and thickening of the vascular wall after
actin injection [38]. Interestingly, the lung was the only organ thatshowed inflammatory injury after intravenous actin injection. The observed lung inflammation was consistent with alterations to lung microvascular endothelial cells. Indeed, when lung endothelial cells were
exposed to DBP-actin complexes in vitro showed enhanced cell death[38]. Reduced levels of DBP were even observed in sepsis and organ
dysfunction of trauma patients as well as complete depletion of free
DBP in those affected by septic shock [33,34]. These data could provide
support for pathogenic explanations of cellular and tissue damage by
SARS-CoV-2 and, at the same time, for the therapeutic use of DBP tobind extracellular actin and counteract microcirculatory alterations.
Whereas DBP also binds free fatty acids, it was shown that the administration of GcMAF complexed with oleic acid (OA) via nebulisationor subcutaneous injection led to rapid decrease of blood pressure andincrease in splenic blood flow, as a result of a verisimilar synergistic NO
release by OA-GcMAF-activated alveolar and splenic macrophages [31].
Severe or critically ill COVID-19 patients developed clinical typicalmanifestations of shock, even in the absence of overt hypotension [7].
Furthermore, it was found that GcMAF can inhibit the angiogenesis
induced by pro-inflammatory prostaglandin E1 [39], which serves rolesin the promotion of vascular endothelial growth factor (VEGF) expression [40]. A key role of VEGF in acute lung injury and ARDS was
confirmed [41].

The role of GcMAF as a multifunctional immune modulator and possible
implications in Covid-19.
It is now well known that DBP Gc-globulin plays a crucial role inimmune system regulation as a primary defense against infections[14–20]. In addition to the storage and transport of active vitamin D3,
GcMAF’s effects include macrophage modulation, osteoclast activation,
facilitation of neutrophil chemotaxis mediated by C5 derived peptide,superoxide activity, scavenging of circulating G-actin, anti-angiogenetic
and anti-tumor properties [24–28]. Thus, this multifunctional protein,released into the blood stream, acts as a systemic immune modulator
without pro-inflammatory activities. This means that any function impairment of Gc-globulin could result in a state of both immunosuppression and uncontrolled inflammation, just like in severe
COVID-19. Interestingly, HIV viremia was associated with higher levelof biomarkers of inflammation (measured by IL-6), monocyte activation(soluble CD14), and coagulation (D-dimer), leading to increased mortality, as compared with uninfected people [29]. Meanwhile, in COVID19 patients, in addition to the reduced peripheral lymphocyte counts,
mainly CD4+ T and CD8+ T cells, there were found significant highlevels of pro-inflammatory cytokines and chemokines [2–7]. Indeed,
GcMAF is not only a simple potent activator for macrophages, but more
specifically is able to turn macrophage activity on at the sites of infection/inflammation and then to induce their apoptosis by upregulating caspase activity via the p38 and JNK1/2 pathways when nolonger needed [30]. Post-mortem lung observations of patients died of
COVID-19 showed the presence of mononuclear cells and macrophages
infiltrating air spaces by autopsy [9–12].
With regards to the anti-oxidant properties, it was assessed that
GcMAF promotes the superoxide generating capacity of activatedmacrophages and the production of nitric oxide (NO) [31]. An article
by Nozik-Grayck et al. [32] pertinently and interestingly showed thatthe expression of extracellular superoxide dismutase (EC-SOD) mRNAand protein is cell- and tissue-specific and is prominent in lung, heart,
blood vessels, placenta and kidney. In particular, high levels of EC-SOD
are present in lung macrophages, alveolar type II cells, fibroblasts,
vascular smooth muscle cells, and endothelial cells. EC-SOD limits
oxidative stress and preserves NO bioactivity, thus protecting against anumber of lung and cardiovascular diseases [32]. Even though only in aminority of cases, COVID-19 may progress to life-threatening complications, including respiratory failure, acute cardiac injury, acute kidney
injury, septic shock, disseminated intra-vascular coagulation (DIC), andmulti-organ dysfunction [2–5]. Hypoxemia was found to be associatedwith interstitial pneumonia and, in 10% to 20% of cases, developed into
acute respiratory distress syndrome (ARDS) [2–5].
In this connection, it was documented that ARDS as well as organ
dysfunction and septic shock is characterized by actin release which is
involved in microvascular impairment [33,34].
DBP has an additional function in binding monomeric globular (G)actin with high affinity. Thereby, rapidly removing polymeric actin fibrils from the blood stream, it prevents actin polymers from clogging
the micro vessels not unlike fibrinogen/fibrin and consequently platelet
aggregation and micro thrombi formation [26,35]. What we postulated
could also explain hypercoagulability with elevated concentrations ofD-dimer, fibrin degradation products increase, PT and aPTT prolongation, observed in COVID-19 patients [36,37]. Tang N et al. [37]Explaining the clinical heterogeneity of Covid-19 with DBP polymorphisms,
estrogens and vitamin D
Reflecting the fact that clinical features and severity of symptoms
vary widely between and within each COVID-19 patient, with older
males more likely to be affected and in a more severe manner [42], wesought to relate it with some special feature of DBP. Several studies
showed that the polymorphisms of DBP were associated with susceptibility or resistance to disease states including chronic obstructive
pulmonary disease [43,44]. Moreover, whereas androgens were notfound to have any effect on circulating levels of DBP, exposure to highlevels of estrogens increased them by up to 50%, suggesting a potential
protective role of estrogens against COVID-19 [28]. On the other hand,in relation to vitamin D status, advanced age was recognized as one of
the major risk factors for vitamin D deficiency [45]. Animal-based
studies also demonstrated that deficiencies in both dietary protein- andenergy-intake decreased the concentration of DBP in the circulation[46]. These data seem to be in line with the growing evidence thatvitamin D supplementation could reduce the risk of COVID-19 infections and deaths [47–49].
Towards the application of GcMAF as immunotherapy: from cancer to
SARS-CoV-2 infection
To date, a pharmaceutical grade GcMAF agent that can be administered to patients with COVID-19 is not developed yet, but, as our
hypothesis suggests that GcMAF, an activator of macrophage, a key
player of innate immunity, may be effective in suppressing the severityof COVID-19-induced immune responses, it would be advisable toproceed in this way.
In the GcMAF development timeline, there have been three major
types of GcMAF until now: purified (i.e. first-generation) GcMAF, serum(i.e. second-generation) GcMAF, and oral colostrum MAF (i.e. thirdgeneration GcMAF).
The first-generation GcMAF is produced from Gc protein isolated
from human serum by an artificial enzymatic method using an affinity2Medical Hypotheses 144 (2020) 110293

L. Spadera and M. Spaderacolumn modified with 25-hydroxy-vitamin D3 [50].
The second-generation GcMAF is prepared from degalactosylated/desialylated human serum without isolation of Gc protein using vitamin
D affinity chromatography, leading to a higher concentration, stability
and activity of the final GcMAF, without the risk of cross-contamination
between different serum samples [51]. In addition, the second-generation GcMAF has been shown to have increasing activity of macrophages, superoxide radical generation, anti-angiogenetic effects, andantitumor effects.
In 2014, Saisei Mirai clinics (cell processing center, clinic in Kobe,
Osaka and Tokyo), in collaboration with Tokushima University, developed a new form of GcMAF made from bovine colostrum [52]. Colostrum MAF has the advantage that it can be orally administered,namely, in an acid-resistant enteric capsule to activate macrophages in
the gut-associated lymphoid tissue (GALT) [53]. This is considered tobe the largest macrophage pool in the body playing a very importantrole in maintaining and regulating mucosal immunity [53]. Macrophages in the gastrointestinal mucosa also could modulate the respiratory tract mucosal immunity through immune regulation, the socalled “gut-lung axis”. Additionally, colostrum MAF is administered as apowder in the mouth to activate macrophages in the lymphoid tissue ofthe Waldeyer's tonsillar ring. In this regard, it is remarkable that Angiotensin Converting Enzyme 2 (ACE2), an Entry Receptor for SARSCoV-2, was found to be highly expressed in gastrointestinal epithelial
cells, providing a prerequisite for SARS-CoV-2 infection [54]. On thisbase, if we consider GcMAF as an off-label immunomodulating agent
for the treatment of COVID-19, oral administration should be preferred
to all the other ones.
Although the administration of GcMAF is a yet an unapproved
therapy, data from previous studies and clinical practice reported its
effectiveness in the treatment of many pathologies such as HIV infection [55] and other infectious diseases [53], some types of cancer[56–60], juvenile osteopetrosis [61], immunological (systemic erythematous lupus) [62] and neurological (multiple sclerosis, autism)
diseases [57,63,64]. In the same conditions, it was found an inverse
correlation between the MAF precursor activity and serum levels ofnagalase (reference ranges from 0,32 to 0,65–0,95 nM/min/ng),
therefore showing to be other than pathogenicity or cancer biomarkers,
also good prognosticators of illness and response to therapy [54–64].
However, it’s clear that only well-designed clinical trials will be able
to properly evaluate the therapeutic use of GcMAF.
The main targets of the pharmacologic approaches to COVID-19,
especially for the complicated cases, are addressed to modulate theimmune system and counteract the overwhelming inflammation.
Notably, the mechanisms we have hypothesized about the possible
pathogenesis of the cell and tissue damage induced by SARS-CoV-2
seem to provide a common denominator in explaining the effects ofmost drugs currently considered for the treatment of COVID-19: theseinclude antivirals (i.e. remdesivir, lopinavir/ritonavir, darunavir, cobicistat) and immunomodulating and/or anti-inflammatory drugs[65,66].
In particular, based on their antiviral activity [67], chloroquine andhydroxychloroquine, initially conceived as antimalarial therapeutics,
were proposed to treat patients hospitalized with COVID-19, better if
associated to azithromycin, showing promising efficacy in “inhibiting
the exacerbation of pneumonia, improving lung imaging findings,
promoting a virus negative conversion and shortening the disease
course“ [68,69]. On the other hand, hydroxychloroquine is the cornerstone of medical therapy in lupus, where it acts as an immunomodulatory without immunosuppressive effects [70]. However, inlight of ongoing serious cardiac adverse events [71] and other serious
side effects, the known and potential benefits of chloroquine and hydroxychloroquine no longer outweigh the known and potential risks forthe authorized use in COVID-19 patients. In addition, the COVID-19
Treatment Guidelines Panel recommends against using hydroxychloroquine plus azithromycin for the treatment of COVID-19, except ina clinical trial [72].
Tocilizumab, an IL-6 antagonist, approved for the treatment ofrheumatoid arthritis and juvenile idiopathic arthritis, also had therapeutic application in critical COVID-19 patients, providing encouraging results [73]. However, the phase III clinical trial (COVACTA) [74]for evaluating tocilizumab in hospitalized patients with severe COVID19 pneumonia found no difference between tocilizumab versus placebo
in intensive care requirements or mortality. Therefore, there are insufficient data for the Panel to recommend either for or against the useof the IL-6 inhibitors for the treatment of COVID-19 [72].
The rationale basis for the use of monoclonal antibodies in patientsaffected by SARS-CoV-2 seems to lie in the so-called systemic cytokine
storm. Taking into account the key role of VEGF in enhancing angiogenesis in acute lung injury and ARDS [75], two trials, evaluating theefficacy of bevacizumab as VEGF antagonist in the treatment of COVID19 (BEST-PC and BEST-RCT), were started [76,77].
Possible consequences of the hypothesis and conclusionLess than two months after the declaration of pandemic state by theWorld Health Organization, every effort by the entire scientific community has been made to face this worldwide emergency of COVID-19
in the best possible way.
However, at the present days, the underlying mechanisms of pathophysiology remain unknown. Nowadays, although a number ofpreliminary clinical trials are underway and scientific evidence is
growing on this topic, neither specific drugs nor effective preventive
measures are yet available for the treatment of COVID-19. Anyway, it
seems we still have a great deal of work to find the “miracle care”.
However, due to the risk of serious drug-related adverse events, theimmunomodulatory and anti-inflammatory drugs currently used for
COVID-19, are still restricted to carefully selected and complicatedcases [71,78–81].
So, in sight of this, given its multifunctional properties, we believethat GcMAF could have a very important role in the pathophysiology oforgan damage induced by SARS-CoV-2, providing explanations which
are consistent with the clinical, radiological and histopathologicalfindings observed in patients with COVID-19.
Despite burgeoning data from case series of various pathologicalconditions demonstrated the potential clinical benefits of GcMAF as
above mentioned [55-64], no randomized controlled clinical trials
verifying these preliminary results have been made till now. So, there
are still unresolved controversies about the possibility of an its therapeutic application. To date, no other researcher has investigated thepossibility of a potential linkage between GcMAF and COVID-19.
However, in view of the immunomodulatory potential and the highsafety profile of GcMAF and because COVID-19 remains a life-threatening condition in many cases, despite currently recommended
therapies, we think it is worth explorating our hypothesis further by:- detecting the MAF precursor activity of serum Gc protein and serum
Nagalase activity in all COVID-19 patients;- providing in a short time, in addition to currently used drugs,
GcMAF to critically ill COVID-19 patients, requesting Institutional
Review Board (IRB) approval for compassionate use protocols on an
emergency basis;- confirming, in prospective randomized controlled clinical trials, theefficacy and the safety of the proposed treatment, in order to allow
the international scientific community to analyse the results andguide the future clinical practice.
According to the provided literature overview, we firmly believethat GcMAF deserves be tested as immune-therapeutic to increase
macrophages functionality for earlier SARS-CoV-2 viral control, protection against COVID-19 progression by limiting epithelial damage,control local inflammation and prevent from the hyperinflammatory3Medical Hypotheses 144 (2020) 110293

L. Spadera and M. Spadera

immune response. For this purpose, we planned a Phase-II interventional clinical trial evaluating the effectiveness and safety of Oral immunotherapy with Third Generation GcMAF in hospitalized patientswith COVID-19 pneumonia (COral-MAF1 Trial) at the “Ospedale delMare” Hospital, Naples, Italy. For the time being, we are waiting forclinical trial approval by local ethics Committee.
In conclusion, even though our hypothesis might be not fully correct, we still wanted to give our own contribution to the research on
COVID-19 pandemic which had the only underserved merit to give all
humans across the world a common goal.
So, as we still see life from a rosy perspective from this small Italian
hospital facing the sea, our last thought and gratitude are for all the
researchers and health care professionals which are committed to theforefront of the war against SARS-CoV-2.

1996;56:2827–31.
[22] Saburi E, Tavakol-Afshari J, Biglari S, et al. Is α-N-acetylgalactosaminidase the key
to curing cancer? A mini-review and hypothesis. J BUON. 2017 NovDec;22(6):1372-1377.
[23] Saburi E, Saburi A, Ghanei M. Promising role for Gc-MAF in cancer immunotherapy:
from bench to bedside. Caspian J Intern Med. 2017 Fall;8(4):228-238.
[24] Nagasawa H, Uto Y, Sasaki H, et al. Anticancer Res. Gc protein (vitamin D-binding
protein): Gc genotyping and GcMAF precursor activity. 2005 NovDec;25(6A):3689-95.
[25] Ruggiero M, Reinwald H, Pacini S. Is chondroitin sulfate responsible for the biological effects attributed to the GC protein-derived Macrophage Activating Factor(GcMAF)? Med Hypotheses 2016;94:126–31.
[26] Van Baelen H, Bouillon R, De Moor P. Vitamin D-binding protein (Gc-globulin)binds actin. J Biol Chem 1980;255(6):2270–2.
[27] Kanda S, Mochizuki Y, Miyata Y, et al. Effects of vitamin D(3)-binding proteinderived macrophage activating factor (GcMAF) on angiogenesis. J Natl Cancer Inst
2002;94(17):1311–9.
[28] Haddad JG. Plasma vitamin D-binding protein (Gc-globulin): multiple tasks. J
Steroid Biochem Mol Biol. 1995 Jun;53(1-6):579-82. Review.
[29] So-Armah KA, Tate JP, Chang C-C, et al. Do biomarkers of inflammation, monocyte
activation, and altered coagulation explain excess mortality between HIV infected
and uninfected people? J Acquir Immune Defic Syndr. 2016;72(2):206–13.
[30] Gumireddy K, Reddy CD, Swamy N. Mitogen-activated protein kinase pathway
mediates DBP-maf-induced apoptosis in RAW 264.7 macrophages. J Cell Biochem
2003;90(1):87–96.
[31] Ruggiero M, Ward E, Smith R, et al. Oleic acid, deglycosylated vitamin D-binding
protein, nitric oxide: a molecular triad made lethal to cancer. Anticancer Res
2014;34(7):3569–78.
[32] Nozik-Grayck E, Suliman HB, Piantadosi CA. Extracellular superoxide dismutase.
Int J Biochem Cell Biol 2005;37(12):2466–71. Epub 2005 Jul 21.
[33] Dahl B, Schiødt FV, Ott P, et al. Plasma concentration of Gc-globulin is associatedwith organ dysfunction and sepsis after injury. Crit Care Med 2003;31(1):152–6.
[34] Lee WM, Galbraith RM. The extracellular actin-scavenger system and actin toxicity.
N Engl J Med 1992;326(20):1335–41.
[35] Vasconcellos CA, Lind SE. Coordinated inhibition of actin-induced platelet aggregation by plasma gelsolin and vitamin D-binding protein. Blood
1993;82(12):3648–57.
[36] Terpos E, Ntanasis-Stathopoulos I, Elalamy I, et al. Hematological findings andcomplications of COVID-19. Am J Hematol 2020.
[37] Tang N, Li D, Wang X, et al. Abnormal coagulation parameters are associated withpoor prognosis in patients with novel coronavirus pneumonia. J Thromb Haemost
2020;18(4):844–7.
[38] Ge L, Trujillo G, Miller EJ, et al. Circulating complexes of the vitamin D binding
protein with G-actin induce lung inflammation by targeting endothelial cells.
Immunobiology 2014;219(3):198–207.
[39] Pacini S, Morucci G, Punzi T, et al. Effect of paricalcitol and GcMAF on angiogenesis
and human peripheral blood mononuclear cell proliferation and signaling. J
Nephrol. 2012 Jul-Aug;25(4):577-81.
[40] Slevin M, Kumar P, Gaffney J, et al. Can angiogenesis be exploited to improve stroke
outcome? Mechanisms and therapeutic potential. Clin Sci (Lond) 2006;111:171–83.
[41] Barratt S, Medford AR, Millar AB. Vascular endothelial growth factor in acute lunginjury and acute respiratory distress syndrome. Respiration 2014;87(4):329–42.
https://doi.org/10.1159/000356034.
[42] Gausman J, Langer A. Sex and gender disparities in the COVID-19 pandemic. J
Womens Health (Larchmt) 2020;29(4):465–6.
[43] Chen H, Zhang L, He Z, et al. Vitamin D binding protein gene polymorphisms andchronic obstructive pulmonary disease: a meta-analysis. J Thorac Dis.
2015;7(8):1423–40.
[44] Stakisaitis D, Lesauskaitė V, Girdauskaitė M, et al. Investigation of vitamin Dbinding protein polymorphism impact on coronary artery disease and relationshipwith longevity: own data and a review. Int J Endocrinol 2016;2016:8347379.
[45] Lips P. Vitamin D physiology. Prog Biophys Mol Biol 2006;92(1):4–8.
[46] Laing CJ, Fraser DR. Changes with malnutrition in the concentration of plasma
vitamin D binding protein in growing rats. Br J Nutr 2002 Aug;88(2):133–9.
[47] Grant WB, Lahore H, McDonnell SL, et al. Evidence that vitamin D supplementation
could reduce risk of influenza and COVID-19 infections and deaths. Nutrients
2020;12(4).
[48] La Vignera S, Cannarella R, Condorelli RA. Sex-specific SARS-CoV-2 mortality:
among hormone-modulated ACE2 expression, risk of venous thromboembolism andhypovitaminosis D. Int J Mol Sci 2020;21(8).
[49] Caccialanza R, Laviano A, Lobascio F, et al. Early nutritional supplementation in
non-critically ill patients hospitalized for the 2019 novel coronavirus disease(COVID-19): Rationale and feasibility of a shared pragmatic protocol. Nutrition
2020;3:110835.
[50] Swamy N, Roy A, Chang R, et al. Affinity purification of human plasma vitamin Dbinding protein. Protein Expr Purif. 1995;6(2):185–8.
[51] Uto Y, Hori H, Kubo K, et al. GcMAF: our next-generation immunotherapy. Nature
2012;485:S67–70.
[52] Uto Y, Kawai T, Sasaki T, et al. Degalactosylated/desialylated bovine colostrum
induces macrophage phagocytic activity independently of inflammatory cytokine
production. Anticancer Res 2015;35:4487–92.
[53] Inui T, Kubo K, Kuchiike D, et al. Oral colostrum macrophage-activating factor forserious infection and chronic fatigue syndrome: three case reports. Anticancer Res.
2015;35:4545–9.
[54] https://www.ncbi.nlm.nih.gov/gene/59272.
[55] Yamamoto N, Ushijima N, Koga Y. Immunotherapy of HIV-infected patients with Gc

Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence the work reported in this paper.
References[1] World Health Organization. Coronavirus disease 2019 (COVID-19): situation report209. (https://www.who.int/docs/default-source/coronaviruse/situation-reports/
20200816-covid-19-sitrep-209.pdf?sfvrsn=5dde1ca2_2).
[2] Guan WJ, Ni ZY, Hu Y, et al. Clinical characteristics of coronavirus disease 2019 in
China. N Engl J Med 2020.
[3] Chen N, Zhou M, Dong X. Epidemiological and clinical characteristics of 99 cases of2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. Lancet.
2020 15-21 February; 395(10223): 507–513.
[4] Huang C, Wang Y, Li X. Clinical features of patients infected with 2019 novel
coronavirus in Wuhan, China. Lancet 2020;395(10223):497–506.
[5] Zhou M, Zhang X, Qu J. Coronavirus Disease 2019 (COVID-19): a clinical update.
Front Med 2020.
[6] Liu J, Li S, Liu J, et al. Longitudinal characteristics of lymphocyte responses andcytokine profiles in the peripheral blood of SARS-CoV-2 infected patients. medRxiv
2020; published online Feb 22.
[7] Li H, Zhang D, Xu J, et al. SARS-CoV-2 and viral sepsis: observations and hypotheses. Lancet 2020.
[8] Shi H, Han X, Jiang N, et al. Radiological findings from 81 patients with COVID-19
pneumonia in Wuhan, China: a descriptive study. Lancet Infect Dis.
2020;20(4):425–34.
[9] Barton LM, Duval EJ, Stroberg E. COVID-19 Autopsies, Oklahoma, USA. Am J Clin
Pathol. 2020 Apr 10. pii: aqaa062.
[10] Tian S, Hu W, Niu L, et al. Pulmonary pathology of early-phase 2019 novel coronavirus (COVID-19) pneumonia in two patients with lung cancer: special report. J
Thorac Oncol. 2020.
[11] Xu Z, Shi L, Wang Y. Pathological findings of COVID-19 associated with acute respiratory distress syndrome. Lancet Respir Med 2020.
[12] Tian S, Xiong Y, Liu H, et al. Pathological study of the 2019 novel coronavirus
disease (COVID-19) through post-mortem core biopsies. Mod Pathol 2020.
[13] Fung SY, Yuen KS, Ye ZW, et al. A tug-of-war between severe acute respiratory
syndrome coronavirus 2 and host antiviral defence: lessons from other pathogenic
viruses. Emerg Microbes Infect 2020;9(1):558–70.
[14] Yamamoto N, Naraparaju VR, Srinivasula SM. Structural modification of serum
vitamin D3-binding protein and immunosuppression in AIDS patients. AIDS Res
Hum Retroviruses 1995;11(11):1373–8.
[15] Yamamoto N. Pathogenic significance of alpha-N-acetylgalactosaminidase activity
found in the envelope glycoprotein gp160 of human immunodeficiency virus Type
1. AIDS Res Hum Retroviruses 2006;22(3):262–71.
[16] Kawakami M, Blum CB, Ramakrishnan R, et al. Turnover of the plasma binding
protein for vitamin D and its metabolites in normal human subjects. J Clin
Endocrinol Metab 1981;53(6):1110–6.
[17] Yamamoto N, Homma S. Vitamin D3 binding protein (group-specific component) isa precursor for the macrophage-activating signal factor from lysophosphatidylcholine -treated lymphocytes. Proc Natl Acad Sci USA 1991.
[18] Yamamoto N, Naraparaju VR. Vitamin D3-binding protein as a precursor for macrophage activating factor in the inflammation-primed macrophage activation cascade in rats. CellImmunol 1996;170(2):161–7.
[19] Yamamoto N, Kumashiro R, Yamamoto M, et al. Regulation of inflammation-primed
activation of macrophages by two serum factors, vitamin D3-binding protein andalbumin. Infect Immun 1993;61(12):5388–91.
[20] Yamamoto N, Urade M. Pathogenic significance of alpha-N-acetylgalactosaminidase
activity found in the hemagglutinin of influenza virus. Microbes Infect 2005
Apr;7(4):674–81.
[21] Yamamoto N, Naraparaju VR, Asbell SO. Deglyco-sylation of serum vitamin D3binding protein leads to immunosuppression in cancer patients. Cancer Res

4

Medical Hypotheses 144 (2020) 110293

L. Spadera and M. Spadera
protein-derived macrophage activating factor (GcMAF). J Med Virol. 2009
Jan;81(1):16-26. Retraction in: J Med Virol. 2014 Nov;86(11):1998.
[56] Yamamoto N, Suyama H. Immunotherapy for prostate cancer with Gc protein-derived macrophage-activating factor, GcMAF. Transl Oncol 2008;1:65–72.
[57] Thyer L, Ward E, Smith R, et al. Therapeutic effects of highly purified de-glycosylated GcMAF in the immunotherapy of patients with chronic diseases. Am J
Immunol 2013;9:78–84.
[58] Inui T, Kuchiike D, Kubo K, et al. Clinical experience of integrative cancer immunotherapy with GcMAF. Anticancer Res 2013;33:2917–9.
[59] Inui T, Makita K, Miura H, et al. Case report: A breast cancer patient treated with
GcMAF, sonodynamic therapy and hormone therapy. Anticancer Res
2014;34:4589–93.
[60] Chaiyasit K, Toshio I, Wiwanitkit V. The use of Gc protein-derived macrophageactivating factor for management of thyroid cancer. J Cancer Res Ther
2015;11:1041.
[61] Yamamoto N, Naraparaju VR, Orchard PJ. Defective lymphocyte glycosidases in themacrophage activation cascade of juvenile osteopetrosis. Blood 1996;88:1473–8.
[62] Yamamoto N, Naraparaju VR, Moore M, Brent LH. Deglycosylation of serum vitamin D3-binding protein by alpha-N-acetylgalactosaminidase detected in theplasma of patients with systemic lupus erythematosus. Clin Immunol
Immunopathol 1997;82:290–8.
[63] Inui T, Katsuura G, Kubo K, et al. Case report: GcMAF treatment in a patient withmultiple sclerosis. Anticancer Res 2016;36:3771–4.
[64] Bradstreet JJ, Vogelaar E, Thyer L. Initial observations of elevated alpha-N-acetylgalactosaminidase activity associated with autism and observed reductions from
Gc protein–macrophage activating factor injections. Autism Insights 2012;4:31.
[65] Scavone C, Brusco S, Bertini M. Current pharmacological treatments for COVID-19:
what's next? Br J Pharmacol 2020.
[66] Jean SS, Lee PI, Hsueh PR. Treatment options for COVID-19: the reality and challenges. J Microbiol Immunol Infect 2020;53(3):436–43.
[67] Inglot AD. Comparison of the antiviral activity in vitro of some non-steroidal antiinflammatory drugs. J Gen Virol 1969;4(2):203–14. https://doi.org/10.1099/00221317-4-2-203.
[68] Touret F, de Lamballerie X. Of chloroquine and COVID-19. Antiviral Res
2020;177:104762.

[69] Gao J, Tian Z, Yang X. Breakthrough: Chloroquine phosphate has shown apparent
efficacy in treatment of COVID-19 associated pneumonia in clinical studies. Biosci
Trends 2020;14(1):72–3.
[70] Jordan N, D’Cruz D. Current and emerging treatment options in the management oflupus. Immunotargets Ther 2016.
[71] Frisk-Holmberg M, Bergqvist Y, Englund U. Chloroquine intoxication. Br J Clin
Pharmacol 1983;15(4):502–3.
[72] https://files.covid19treatmentguidelines.nih.gov/guidelines/covid19treatmentguidelines.pdf.
[73] Oldfield V, Dhillon S, Plosker GL. Tocilizumab: a review of its use in the management of rheumatoid arthritis. Drugs 2009;69(5):609–32.
[74] ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US).
2020 Mar 25 – Identifier: NCT04320615, A Study to Evaluate the Safety andEfficacy of Tocilizumab in Patients With Severe COVID-19 Pneumonia (COVACTA).
(https://clinicaltrials.gov/ct2/show/NCT04320615).
[75] Wang Y, Fei D, Vanderlaan M, Song A. Biological activity of bevacizumab, a humanized anti-VEGF antibody in vitro. Angiogenesis.
[76] ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US).
2020 Feb 19 – Identifier NCT04275414, Bevacizumab in severe or critical patientswith Covid-19 pneumonia (BEST-CP). (https://clinicaltrials.gov/ct2/show/
NCT04275414).
[77] ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US).
2020 Mar 12 Identifier: NCT04305106, Bevacizumab in Severe or Critically Severe
Patients With COVID-19 Pneumonia-RCT (BEST-RCT). (https://clinicaltrials.gov/
ct2/show/NCT04305106).
[78] Yam JC, Kwok AK. Ocular toxicity of hydroxychloroquine. Hong Kong Med J
2006;12(4):294–304.
[79] Radbel J, Narayanan N, Bhatt PJ. Use of tocilizumab for COVID-19 infection-induced cytokine release syndrome: A cautionary case report. Chest. 2020 Apr 25. pii:
S0012-3692(20)30764-9.
[80] Rubel AR, Chong PL, Abdullah MS, et al. Letter to the Editor: Lipemic serum inpatients with COVID-19 undergoing treatment. J Med Virol 2020;28.
[81] Zhang S, Li L, Shen A. Rational use of tocilizumab in the treatment of novel coronavirus pneumonia. Clin Drug Investig 2020.

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