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Ramatroban, a Thromboxane A2/TPr and PGD2/DPr2 receptor antagonist for Acute and Long haul COVID-19
Author: Ajay Gupta, MD
From: “Gupta, Ajay” <ajayg1@hs.uci.edu> Date: Wednesday, July 7, 2021 at 1:10 PM To: Aviva Lev-Ari <AvivaLev-Ari@alum.berkeley.edu> Cc: “Dr. Saul Yedgar” <saulye@ekmd.huji.ac.il> Subject: Ramatroban, a Thromboxane A2/TPr and PGD2/DPr2 receptor antagonist for Acute and Long haul COVID-19
While corticosteroids may have a role in about 5% of hospitalized patients who have the cytokine storm, currently there is no effective treatment for mild or moderate COVID and long haul COVID. Massive increase in respiratory and plasma thromboxane A2 (TxA2) plays a key role in thromboinflammation and microvascular thrombosis, while an increase in respiratory and plasma PGD2 potentially suppresses innate interferon response, and acquired Th1 anti-viral response, while promoting a maladaptive type 2, anti-helminthic like immune response. Ramatroban is a potent dual receptor antagonist of Thromboxane A2/TPr and PGD2/DPr2 that has been used in Japan for the treatment of allergic rhinitis for past 20 years (Baynas®, Bayer Japan). We first disclosed use of ramatroban for COVID in a provisional patent application filed on 31st March, 2020; followed by the publication Gupta et al, J Mol Genet Med, 2020
Several experts, as outlined below in yellow highlighted text, have supported the idea of using ramatroban as an anti-thrombotic and immunomodulator in COVID-19.
1. Prof. Louis Flamand, Nicolas Flamand, Eric Boilard Laval Univ. Quebec, Canada: There is a lipid-mediator storm in COVID-19 characterized by massive increases in thromboxane A2 and PGD2 in the lungs and plasma. “Blocking the deleterious effects of PGD2 and TxA2 with the dual DPr2/TPr antagonist Ramatroban might be beneficial in COVID-19Archambault et al, FASEB, June 2021, doi: https://doi.org/10.1096/fj.202100540R
2. Prof. Garret A FitzGerald, Univ. Of Pennsylvania, Member National Academy of Sciences.https://en.wikipedia.org/wiki/Garret_A._FitzGerald “In the current pandemic there may be utility in targeting eicosanoids with existing drugs. These approaches would likely be most effective early in the disease before the development of ARDS, where cytokines and chemokines dominate. Dexamethasone limits COX-2 expression and might diminish COVID-19 severity and mortality at least in part, by diminishing COX metabolites… Dexamethasone might improve severe COVID-19 by diminishing the prostaglandins / thromboxane storm in the lungs”. “Treatment with a PGD2/DPr2 inhibitor decreased viral load and improved morbidity by upregulating IFN-lambda expression. ….. Antagonism of the thromboxane receptor (TPr) prevents ARDS…. Early administration of well-tolerated TPr antagonists may limit progress to severe COVID-19 (Theken and FitzGerald, Science, 2021)
4. Prof. Simon Phipps, Univ. of Queensland, Brisbane Australia “It has been hypothesized that DP2 antagonists be repurposed as a novel immunotherapy for the treatment of COVID-19, and this may be appropriate in mild to moderate cases where Th1 immunity is impaired.” (Ullah et al, Mucosal Immunology, 2021)
5. Prof. Bruce D. Hammock, Distinguished Professor, Univ of California Davis, Member US National Academy of Sciences and National Academy of Inventors; April 25, 2021. https://www.entsoc.org/fellows/hammock “I find your idea of blocking specific thromboxane receptors in preventing or reducing some of the devastating co-morbidity of COVID-19 very compelling. … A DPr2 receptor blocker is conceptually attractive in offering the potential of effective therapy and low risk due to a high therapeutic index.” E mail dated April 25, 2021.(https://ajp.amjpathol.org/action/showPdf?pii=S0002-9440%2820%2930332-1 and http://ucanr.edu/sites/hammocklab/files/328012.pdf)
6. Ann E Eakin, PhD, Senior Scientific Officer, NIH-NIAID “very compelling data supporting potential benefits of ramatroban in both reducing viral load as well as modulating host responses” E Mail dated Nov 20, 2020
Ramatroban is expected to reduce lung fibrosis in COVID-19 and therefore diminish clinical manifestations of Long haul COVID. Pang et al, 2021 “examined the effect of Ramatroban, a clinical antagonist of both PGD2 and TXA2 receptors, on treating silicosis using a mouse model. The results showed that Ramatroban significantly alleviated silica-induced pulmonary inflammation, fibrosis, and cardiopulmonary dysfunction compared with the control group.” https://www.thno.org/v11p2381.htm
Unfortunately, the animal models of COVID-19 are harsh, lack microvascular thrombosis and immune perturbations characteristic of human disease. These models may be good for testing antivirals but not for testing immunomodulators or anti-thrombotics. There is highly positive anecdotal experience with use of ramatroban in moderately severe COVID-19 (https://www.researchsquare.com/article/rs-474882/v1
Reporter and Curator: Mr. Srinjoy Chakraborty (Junior Research Felllow) and Dr. Sudipta Saha, Ph.D.
Coronavirus disease 2019 (COVID-19), which is caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has emerged as a serious global health issue with high transmission rates affecting millions of people worldwide. The SARS-CoV-2 is known to damage cells in the respiratory system, thus causing viral pneumonia. The novel SARS-CoV-2 is a close relative to the previously identified severe acute respiratory syndrome-coronavirus (SARS-CoV) and Middle East respiratory syndrome-coronavirus (MERS-CoV) which affected several people in 2002 and 2012, respectively. Ever since the outbreak of covid-19, several reports have poured in about the impact of Covid-19 on pregnancy. A few studies have highlighted the impact of the viral infection in pregnant women and how they are more susceptible to the infection because of the various physiological changes of the cardiopulmonary and immune systems during pregnancy. It is known that SARS-CoV and MERS-CoV diseases have influenced the fatality rate among pregnant women. However, there are limited studies on the impact of the novel corona virus on the course and outcome of pregnancy.
Figure: commonly observed clinical symptoms of COVID-19 in the general population: Fever and cough, along with dyspnoea, diarrhoea, and malaise are the most commonly observed symptoms in pregnant women, which is similar to that observed in the normal population.
The WHO and the Indian Council of Medical Research (ICMR) have proposed detailed guidelines for treating pregnant women; these guidelines must be strictly followed by the pregnant individual and their families. According to the guidelines issued by the ICMR, the risk of pregnant women contracting the virus to that of the general population. However, the immune system and the body’s response to a viral infection is altered during pregnancy. This may result in the manifestation of more severe symptoms. The ICMR guidelines also state that the reported cases of COVID-19 pneumonia in pregnancy are milder and with good recovery. However, by observing the trends of the other coronavirus infection (SARS, MERS), the risks to the mother appear to increase in particular during the last trimester of pregnancy. Cases of preterm birth in women with COVID-19 have been mentioned in a few case report, but it is unclear whether the preterm birth was always iatrogenic, or whether some were spontaneous. Pregnant women with heart disease are at highest risk of acquiring the infection, which is similar to that observed in the normal population. Most importantly, the ICMR guidelines highlights the impact of the coronavirus epidemic on the mental health of pregnant women. It mentions that the since the pandemic has begun, there has been an increase in the risk of perinatal anxiety and depression, as well as domestic violence. It is critically important that support for women and families is strengthened as far as possible; that women are asked about mental health at every contact.
With the available literature available on the impact of SARS and MERS on reproductive outcome, it has been mentioned that SARS infection did increase the risk of miscarriage, preterm birth and, intrauterine foetal growth restriction. However, the same has not been demonstrated in early reports from COVID-19 infection in pregnancy. According to a study that included 8200 participants conducted by the centre for disease control and prevention, pregnant women may be at a higher risk of acquiring severe infection and need for ICU admissions as compared to their non-pregnant counterparts. However, a detailed and thorough study involving a larger proportion of the population is needed today.
Start Quote from European Medicines Agency document
Meeting highlights from the Pharmacovigilance Risk Assessment Committee (PRAC) 3-6 May 2021
News 07/05/2021
This month EMA’s safety committee (PRAC) reviewed a number of safety signals related to COVID-19 vaccines. The evaluation of safety signals is a routine part of pharmacovigilance and is essential to ensuring that regulatory authorities have a comprehensive knowledge of a medicine’s benefits and risks.
PRAC concludes review of signal of facial swelling with COVID-19 vaccine Comirnaty
PRAC has recommended a change to Comirnaty’s product information. After reviewing all the available evidence, including cases reported to the European database for suspected side effects (EudraVigilance) and data from the scientific literature, PRAC considered that there is at least a reasonable possibility of a causal association between the vaccine and the reported cases of facial swelling in people with a history of injections with dermal fillers (soft, gel-like substances injected under the skin). Therefore, PRAC concluded that facial swelling in people with a history of injections with dermal fillers should be included as a side effect in section 4.8 of the summary of product characteristics (SmPC) and in section 4 of the patient information leaflet (PIL) for Comirnaty. The benefit-risk balance of the vaccine remains unchanged.
PRAC concludes review of unusual blood clots with low blood platelets1 with Janssen’s COVID-19 vaccine
PRAC has now concluded its review of COVID-19 Vaccine Janssen and confirmed, as previously communicated, that the benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects. In finalising the review, the Committee recommended on 20 April further refinement of the warning about thrombosis (formation of blood clots in the vessels) with thrombocytopenia (low blood platelets) syndrome, which was listed previously in the product information for COVID-19 Vaccine Janssen. The product information will now also include advice that patients who are diagnosed with thrombocytopenia within three weeks of vaccination should be actively investigated for signs of thrombosis. Similarly, patients who present with thromboembolism within three weeks of vaccination should be evaluated for thrombocytopenia. Lastly, thrombosis with thrombocytopenia syndrome will be added as an ‘important identified risk’ in the risk management plan for the vaccine. Furthermore, the marketing authorisation holder will provide a plan to further study the possible underlying mechanisms for these very rare events.
PRAC continues to closely review Comirnaty and COVID-19 Vaccine Moderna for unusual blood clots with low blood platelets2
The PRAC is closely monitoring whether mRNA vaccines might also be linked to cases of rare, unusual blood clots with low blood platelets, a side effect that has been reported in Vaxzevria and COVID-19 vaccine Janssen. Following a review of reports of suspected side effects, the PRAC considers at this stage that there is no safety signal for the mRNA vaccines. Only few cases of blood clots with low blood platelets have been reported. When seen in the context of the exposure of people to the mRNA vaccines, these numbers are extremely low, and their frequency is lower than the one occurring in people who have not been vaccinated. In addition, these cases do not seem to present the specific clinical pattern observed with Vaxzevria and COVID-19 Vaccine Janssen. Overall, the current evidence does not suggest a causal relation.
EMA will continue to monitor this issue closely and communicate further if necessary.
Topics of interests from enhanced monitoring of COVID-19 vaccines
Enhanced safety monitoring in the form of pandemic summary safety reports is one of the commitments required from the marketing authorisation holders in the context of the conditional marketing authorisation. Marketing authorisation holders are required to submit pandemic summary safety reports to EMA on a monthly basis. These reports are reviewed by the PRAC and any areaof concern further investigated, if needed.
PRAC assessing reports of Guillain-Barre syndrome with AstraZeneca’s Covid-19 vaccine
As part of the review of the regular pandemic summary safety reports for Vaxzevria, AstraZeneca’s Covid-19 vaccine, the PRAC is analysing data provided by the marketing authorisation holder on cases of Guillain-Barre syndrome (GBS) reported following vaccination. GBS is an immune system disorder that causes nerve inflammation and can result in pain, numbness, muscle weakness and difficulty walking. GBS was identified during the marketing authorisation process as a possible adverse event requiring specific safety monitoring activities. PRAC has requested the marketing authorisation holder to provide further detailed data, including an analysis of all the reported cases in the context of the next pandemic summary safety report.
PRAC will continue its review and will communicate further when new information becomes available.
PRAC assessing reports of myocarditis with Comirnaty and COVID-19 Vaccine Moderna
EMA is aware of cases of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the membrane around the heart) mainly reported following vaccination with Comirnaty. There is no indication at the moment that these cases are due to the vaccine. However, PRAC has requested the marketing authorisation holder to provide further detailed data, including an analysis of the events according to age and gender, in the context of the next pandemic summary safety report and will consider if any other regulatory action is needed. Additionally, the PRAC has requested the marketing authorisation holder for COVID-19 Vaccine Moderna– also an mRNA vaccine – to monitor similar cases with their vaccine and to also provide a detailed analysis of the events in the context of the next pandemic summary safety report. EMA will communicate further when new information becomes available.
1Thrombosis with thrombocytopenia syndrome 2Thrombosis with thrombocytopenia syndrome
Scientists have recognized human genes that fight against the SARS-CoV-2 viral infection. The information about genes and their function can help to control infection and aids the understanding of crucial factors that causes severe infection. These novel genes are related to interferons, the frontline fighter in our body’s defense system and provide options for therapeutic strategies.
Sumit K. Chanda, Ph.D., professor and director of the Immunity and Pathogenesis Program at Sanford Burnham Prebys reported in the article that they focused on better understanding of the cellular response and downstream mechanism in cells to SARS-CoV-2, including the factors which causes strong or weak response to viral infection. He is the lead author of the study and explained that in this study they have gained new insights into how the human cells are exploited by invading virus and are still working towards finding any weak point of virus to develop new antivirals against SARS-CoV-2.
With the surge of pandemic, researchers and scientists found that in severe cases of COVID-19, the response of interferons to SARS-CoV-2 viral infection is low. This information led Chanda and other collaborators to search for interferon-stimulated genes (ISGs), are genes in human which are triggered by interferons and play important role in confining COVID-19 infection by controlling their viral replication in host.
The investigators have developed laboratory experiments to identify ISGs based on the previous knowledge gathered by the outbreak of SARS-CoV-1 from 2002-2004 which was similar to COVID-19 pandemic caused by SARS-CoV-2 virus.
The article reports that Chanda mentioned “we found that 65 ISGs controlled SAR-CoV-2 infection, including some that inhibited the virus’ ability to enter cells, some that suppressed manufacture of the RNA that is the virus’s lifeblood, and a cluster of genes that inhibited assembly of the virus.” They also found an interesting fact about ISGs that some of these genes revealed control over unrelated viruses, such as HIV, West Nile and seasonal flu.
Laura Martin-Sancho, Ph.D., a senior postdoctoral associate in the Chanda lab and first author of the study reported in the article that they identified 8 different ISGs that blocked the replication of both SARS-CoV-1 and CoV-2 in the subcellular compartments responsible for packaging of proteins, which provide option to exploit these vulnerable sites to restrict infection. They are further investigating whether the genetic variability within the ISGs is associated with COVID-19 severity.
The next step for researchers will be investigating and observing the biology of variants of SARS-CoV-2 that are evolving and affecting vaccine efficacy. Martin-Sancho mentioned that their lab has already started gathering all the possible variants for further investigation.
“It’s vitally important that we don’t take our foot off the pedal of basic research efforts now that vaccines are helping control the pandemic,” reported in the article by Chanda.
“We’ve come so far so fast because of investment in fundamental research at Sanford Burnham Prebys and elsewhere, and our continued efforts will be especially important when, not if, another viral outbreak occurs,” concluded Chanda.
Why wait for more info? A new case of cerebral sinus venus thrombosis was reported in a 25 year old man who became critically ill from a cerebral hemorrhage. And for women age 20-50, CSVT occurred in 1 in 13,000, or 4-15X higher than background.
UPDATED on 4/14/2021
How UK doctor linked rare blood-clotting to AstraZeneca Covid jab
We have put together the following mechanism for thrombosis including central vein sinus thrombosis as a complication of both J&J and the AstraZeneca vaccines. This unifying mechanism explains the predilection of cerebral veins and higher risk in younger women. Please share your thoughts on the proposed mechanism.
We have submitted the attached manuscript to SSRN. Sharing this promptly considering the public health significance.
Thanks
Figure 1. AstraZeneca or Janssen COVID-19 vaccine induced thromboinflammation and cerebral venous sinus thrombosis (CVST)-Proposed Mechanisms: Adenovirus carrier delivers SARS-CoV-2 DNA encoding the Spike (S) protein to the lung megakaryocytes via the coxsackie-adenovirus receptor (CAR). Spike protein induces COX-2 expression in megakaryocytes leading to megakaryocyte activation, biogenesis of activated platelets that express COX-2 and generate thromboxane A2 (TxA2). Cerebral vein sinus endothelial cells express podoplanin, a natural ligand for CLEC2 receptors on platelets. Platelets traversing through the cerebral vein sinuses would be further activated by TxA2 dependent podoplanin-CLEC2 signaling, leading to release of extracellular vesicles, thereby promoting CLEC5A and TLR2 mediated neutrophil activation, thromboinflammation, CVST, and thromboembolism in other vascular beds. Young age and female gender are associated with increased TxA2 generation and platelet activation respectively, and hence increased risk of thromboembolic complications following vaccination.
Best regards,
Ajay
Ajay Gupta, M.B.,B.S., M.D.
Clinical Professor,
Division of Nephrology, Hypertension and Kidney Transplantation
University of California Irvine
President & CSO, KARE Biosciences (www.karebio.com)
Title: SARS-CoV-2 vaccination induced thrombosis: Is chemoprophylaxis with antiplatelet agents warranted?
Guest Authors:
Kate Chander Chiang1
Ajay Gupta, MBBS, MD1,2
Affiliations
(1) KARE Biosciences, Orange, CA 92869
(2) Department of Medicine, University of California Irvine (UCI) School of Medicine, Orange, CA 92868
*Corresponding author:
Ajay Gupta, MBBS, MD
Clinical Professor of Medicine,
Division of Nephrology, Hypertension and Kidney Transplantation
University of California Irvine (UCI) School of Medicine,
Orange, CA 92868
Tel: +1 (562) 412-6259
E-mail: ajayg1@hs.uci.edu
Word Count
Abstract: 359
Main Body: 1,648
Funding: No funding was required.
Conflict of Interest: AG and KCC have filed a patent for use of Ramatroban as an anti-thrombotic and immune modulator in SARS-CoV-2 infection. The patents have been licensed to KARE Biosciences. KCC is an employee of KARE Biosciences.
Author Contributions: AG and KCC conceptualized, created the framework, wrote and reviewed the manuscript.
The COVID-19 vaccines, Vaxzevria® (AstraZeneca) and the Janssen vaccine (Johnson & Johnson) are highly effective but associated with rare thrombotic complications. These vaccines are comprised of recombinant, replication incompetent, chimpanzee adenoviral vectors encoding the Spike (S) glycoprotein of SARS-CoV-2. The adenovirus vector infects epithelial cells expressing the coxsackievirus and adenovirus receptor (CAR). The S glycoprotein of SARS-CoV-2 is expressed locally stimulating neutralizing antibody and cellular immune responses, which protect against COVID-19. The immune responses are highly effective in preventing symptomatic disease in adults irrespective of age, gender or ethnicity. However, both vaccines have been associated with thromboembolic events including cerebral venous sinus thrombosis (CVST). Megakaryocytes also express CAR, leading us to postulate adenovirus vector uptake and expression of spike glycoprotein by megakaryocytes. Spike glycoprotein induces expression of cyclooxygenase -2 (COX-2), leading to generation of thromboxane A2 (TxA2). TxA2 promotes megakaryocyte activation, biogenesis of activated platelets and thereby increased thrombogenicity. Cerebral vein sinus endothelial cells express podoplanin, a natural ligand for CLEC2 receptors on platelets. Platelets traversing through the cerebral vein sinuses would be further activated by TxA2 dependent podoplanin-CLEC2 signaling, leading to CVST. The mechanisms proposed are consistent with the following clinical observations. First, a massive increase in TxA2 generation promotes platelet activation and thromboinflammation in COVID-19 patients. Second, TxA2 generation and platelet activation is increased in healthy women compared to men, and in younger mice compared to older mice; and, younger age and female gender appear to be associated with increased risk of thromboembolism as a complication of adenoviral vector based COVID-19 vaccine. The roll out of both AstraZeneca and Janssen vaccines has been halted for adults under 30-60 years of age in many countries. We propose that antiplatelet agents targeting TxA2 receptor signaling should be considered for chemoprophylaxis when administering the adenovirus based COVID-19 vaccines to adults under 30-60 years of age. In many Asian and African countries, only adenovirus-based COVID-19 vaccines are available at present. A short course of an antiplatelet agent such as aspirin could allow millions to avail of the benefits of the AstraZeneca and Janssen COVID-19 vaccines which could be otherwise either denied to them or put them at undue risk of thromboembolic complications.
COVID-19 disease is caused by a novel positive-strand RNA coronavirus (SARS-CoV-2), which belongs to the Coronaviridae family, along with the severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS) coronaviruses.1 The genome of these viruses encodes several non-structural and structural proteins, including spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins.2 The majority of the vaccines for COVID-19 that employ administration of viral antigens or viral gene sequences aim to induce neutralizing antibodies against the viral spike protein (S), preventing uptake through the ACE2 receptor, and thereby blocking infection.3
The Janssen COVID-19 vaccine (Johnson & Johnson) is comprised of a recombinant, replication- incompetent Ad26 vector, encoding a stabilized variant of the SARS-CoV-2 Spike (S) protein. The ChAdOx1 nCoV-19 vaccine (AZD1222, Vaxzevria®) was developed at Oxford University and consists of a replication-deficient chimpanzee adenoviral vector ChAdOx1, encoding the S protein.4 In US Phase III trials, Vaxzevria has been demonstrated to have 79% efficacy at preventing symptomatic COVID-19, and 100% efficacy against severe or critical disease and hospitalization, with comparable efficacy across ethnicity, gender and age.5 However, Vaxzevria has been associated with thrombotic and embolic events including disseminated intravascular coagulation (DIC) and cerebral venous sinus thrombosis (CVST), occurring within 14 days after vaccination, mostly in people under 55 years of age, the majority of whom have been women.6 Data from Europe suggests that the event rate for thromboembolic events may be about 10 per million vaccinated. Antibodies to platelet factor 4/heparin complexes have been recently reported in a few patients.7 However, the significance of this finding remains to be established. As of April 12, 2021, about 6.8 million doses of the Janssen vaccine have been administered in the U.S.8 CDC and FDA are reviewing data involving six reported U.S. cases of CVST in combination with thrombocytopenia.8 All six cases occurred among women between the ages of 18 and 48, and symptoms occurred 6 to 13 days after vaccination.8
SARS-CoV-2 is known to cause thromboinflammation leading to thrombotic microangiopathy, pulmonary thrombosis, pedal acro-ischemia (“COVID-toes”), arterial clots, strokes, cardiomyopathy, coronary and systemic vasculitis, deep venous thrombosis, pulmonary embolism, and microvascular thrombosis in renal, cardiac and brain vasculature.9-14 Cerebral venous sinus thrombosis (CVST) has also been reported in COVID-19 patients.15 Amongst 34,331 hospitalized COVID-19 patients, CVST was diagnosed in 28.16 In a multicenter, multinational, cross sectional, retrospective study of 8 patients diagnosed with CVST and COVID-19, seven were women.17 In another series of 41 patients with COVID-19 and CVST, the average age was about 50 years (SD, 16.5 years).17 The pathobiology of thrombotic events associated with the AstraZeneca vaccine should be viewed in the context of mechanisms underlying thromboinflammation that complicates SARS-CoV-2 infection and COVID-19 disease.
A. Role of COX-2 and thromboxane A2 in thromboinflammation complicating adenovirus based COVID-19 vaccine encoding the Spike protein of SARS-CoV-2
Thromboinflammation in COVID-19 seems to be primarily caused by endothelial, platelet and neutrophil activation, platelet-neutrophil aggregates and release of neutrophil extracellular traps (NETs).13,18 Platelet activation in COVID-19 is fueled by a lipid storm characterized by massive increases in thromboxane A2 (TxA2) levels in the blood and bronchoalveolar lavage fluid.19,20 Cyclooxygenase (COX) enzymes catalyze the first step in the biosynthesis of TxA2 from arachidonic acid, and COX-2 expression is induced by the spike (S) protein of coronaviruses.21 We postulate that an aberrant increase in TxA2 generation induced by the spike protein expression from the AstraZeneca vaccine leads to thromboinflammation, thromboembolism and CVST. 4
The support for the above proposed mechanism comes from the following observations. First, when mice of different age groups were infected with SARS-CoV virus, the generation of TxA2 was markedly increased in younger mice compared to middle aged mice.22 Furthermore, in children with asymptomatic or mildly symptomatic SARS-CoV-2 infection, microvascular thrombosis and thrombotic microangiopathy occur early in infection.20 These observations are consistent with the higher risk for thrombosis in adults under 60 years of age, compared with the older age group.6,7 Second, platelets from female mice are much more reactive than from male mice.23 Furthermore, TxA2 generation, TxA2-platelet interaction and activation is increased in women compared to men.24,25 These observations are consistent with disproportionately increased risk of thrombosis in women following AstraZeneca and Janssen COVID-19 vaccines.
The adenoviral vector ChAdOx1, containing nCoV-19 spike protein gene, infects host cells through the coxsackievirus and adenovirus receptor (CAR).26 CAR-dependent cell entry of the viral vector allows insertion of the SARS-CoV-2 spike protein gene and expression of Spike protein by host cells (Figure 1). CAR is primarily expressed on epithelial tight junctions.27 CAR expression has also been reported in platelets,28 and since platelets are anucleate cells CAR expression by megakaryocytes can be inferred. Therefore, AstraZeneca and Janssen vaccines would be expected to induce expression of Spike protein in megakaryocytes and platelets (Figure 1).
Spike protein of coronaviruses in known to induce COX-2 gene expression.21,29 COX-2 expression is induced during normal human megakaryopoiesis and characterizes newly formed platelets.30 While in healthy controls <10% of circulating platelets express COX-2, in patients with high platelet generation, up to 60% of platelets express COX-2.30 Generation of TxA2 by platelets is markedly suppressed by COX-2 inhibition in patients with increased megakaryopoiesis versus healthy subjects.30 Therefore, we postulate that expression of Spike protein induces COX-2 expression and generation of thromboxane A2 by megakaryocytes. TxA2 promotes biogenesis of activated platelets expressing COX-2. Platelet TxA2 generation leads to platelet activation and aggregation, and thereby thromboinflammation (Figure 1).
Extravascular spaces of the lungs comprise populations of mature and immature megakaryocytes that originate from the bone marrow, such that lungs are a major site of platelet biogenesis, accounting for approximately 50% of total platelet production or about 10 million platelets per hour.31 More than 1 million extravascular megakaryocytes have been observed in each lung of transplant mice.31 Following intramuscular injection of the AstraZeneca and Janssen vaccines, the adenovirus vector will traverse the veins and lymphatics to be delivered to the pulmonary circulation thereby exposing lung megakaryocytes in the first pass. Interestingly, under thrombocytopenic conditions, haematopoietic progenitors migrate out of the lung to repopulate the bone marrow and completely reconstitute blood platelet counts.31
B. Predilection of cerebral venous sinuses for thrombosis following vaccination
Recent studies have demonstrated that arterial, venous and sinusoidal endothelial cells in the brain uniquely express markers of the lymphatic endothelium including podoplanin.32 Podoplanin serves as a ligand for CLEC2 receptors on platelets.33 Thromboxane A2 dependent CLEC2 signaling leads to platelet activation (Figure 1), while a TxA2 receptor antagonist nearly abolish CLEC2 signaling and platelet activation.33 TxA2 dependent CLEC2 signaling promotes release of exosomes and microvesicles from platelets, leading to activation of CLEC5A and TLR2 receptors respectively on neutrophils, neutrophil activation and release of neutrophil extracellular traps (NETs) (Figure 1).34 Neutrophil activation, more than platelet activation, is associated with thrombotic complications in COVID-19.13,18,35 As proposed above, the expression of podoplanin, a unique molecular signature of cerebral endothelial cells, may be responsible for the predilection of brain vascular bed to thromboinflammation and CVST as a complication of COVID-19 vaccines. 5
C. Chemoprophylaxis with antiplatelet agents
In animal models of endotoxin mediated endothelial injury and thromboinflammation, antagonism of TxA2 signaling prevents ARDS, reduces myocardial damage and increases survival.36-38
Considering the key role played by platelets in thromboinflammation, we propose consideration of antiplatelet agents, either aspirin or TxA2 receptor antagonists, as chemoprophylactic agents when the AstraZeneca vaccine is administered to adults between 18 and 60 years of age.39 High bleeding risk because of another medical condition or medication would be contraindications to use of antiplatelet agents.39 Medical conditions that increase bleeding risk include previous gastrointestinal bleeding, peptic ulcer disease, blood clotting problems, and kidney disease.39 Medications that increase bleeding risk include nonsteroidal anti-inflammatory drugs, steroids, and other anticoagulants or anti-platelet agents.39 Aspirin appears to be safe in COVID-19. In a retrospective observational study in hospitalized patients with COVID-19, low-dose aspirin was found to be effective in reducing morbidity and mortality; and was not associated with any safety issues including major bleeding.40 Therefore, aspirin is likely to be safe as an adjunct to COVID-19 vaccines even in the event of a subsequent infection with SARS-CoV-2 virus.
Can aspirin influence the host immune response to the COVID-19 vaccines? This issue merits further investigation. When healthy adults > 65 years of age were given influenza vaccine and randomized to receive 300 mg aspirin or placebo on days 1, 2, 3, 5 and 7, the aspirin group showed 4-fold or greater rise in influenza specific antibodies.41 The risk-benefit analysis, based on above information, suggests that a one to three week course of low-dose aspirin merits consideration in order to prevent the thromboembolic events associated with the AstraZeneca vaccine.
SUMMARY
Thromboembolic disease including disseminated intravascular coagulation and cerebral venous sinus thrombosis have been reported in association with AstraZeneca and Janssen COVID-19 vaccines. Many countries have halted use of these vaccines either entirely or for adults under 30 to 60 years of age. European and North American countries generally have access to mRNA vaccines. However, in Asian and African countries the choices are limited to adenovirus based COVID-19 vaccines. The governments in such countries are forging ahead with vaccinating all adults, including those under 60 years of age, with Vaxzevria, Covishield (the version of Vaxzevria manufactured by the Serum Institute of India) or the Janssen vaccines. This has led to grave concern and anxiety amongst the citizens and medical professionals. Considering the profound global public health implications of limiting the use of these vaccines, it is critical to understand the pathobiology of vaccination induced thrombotic events in order to guide strategies aimed at prevention. In this regard, studies are urgently needed to examine lipid mediators and thromboxane A2 – platelet axis following vaccination with these vaccines, compared with mRNA vaccines. The risk-benefit analysis based on information presented here suggests that chemoprophylaxis using a short course of low-dose aspirin in adults under 60 years of age may be justified in conjunction with adenovirus based COVID-19 vaccines in order to prevent thromboembolic events and enhance safety. 6
Figure 1. AstraZeneca or Janssen COVID-19 vaccine induced thromboinflammation and cerebral venous sinus thrombosis (CVST)-Proposed Mechanisms: Adenovirus carrier delivers SARS-CoV-2 DNA encoding the Spike (S) protein to the lung megakaryocytes via the coxsackie-adenovirus receptor (CAR). Spike protein induces COX-2 expression in megakaryocytes leading to megakaryocyte activation, biogenesis of activated platelets that express COX-2 and generate thromboxane A2 (TxA2). Cerebral vein sinus endothelial cells express podoplanin, a natural ligand for CLEC2 receptors on platelets. Platelets traversing through the cerebral vein sinuses would be further activated by TxA2 dependent podoplanin-CLEC2 signaling, leading to release of extracellular vesicles, thereby promoting CLEC5A and TLR2 mediated neutrophil activation, thromboinflammation, CVST, and thromboembolism in other vascular beds. Young age and female gender are associated with increased TxA2 generation and platelet activation respectively, and hence increased risk of thromboembolic complications following vaccination.
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Subject: APRIL 13. 2021 – J&J Statement – Out of an abundance of caution, the CDC and FDA have recommended a pause in the use of our vaccine. ->> Are there relations between these FINDINGS?
Johnson & Johnson Statement on COVID-19 Vaccine
NEW BRUNSWICK, N.J., April 13, 2021– The safety and well-being of the people who use our products is our number one priority. We are aware of an extremely rare disorder involving people with blood clots in combination with low platelets in a small number of individuals who have received our COVID-19 vaccine. The United States Centers for Disease Control (CDC) and Food and Drug Administration (FDA) are reviewing data involving six reported U.S. cases out of more than 6.8 million doses administered. Out of an abundance of caution, the CDC and FDA have recommended a pause in the use of our vaccine.
In addition, we have been reviewing these cases with European health authorities. We have made the decision to proactively delay the rollout of our vaccine in Europe.
We have been working closely with medical experts and health authorities, and we strongly support the open communication of this information to healthcare professionals and the public.
The CDC and FDA have made information available about proper recognition and management due to the unique treatment required with this type of blood clot. The health authorities advise that people who have received our COVID-19 vaccine and develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their health care provider.
For more information on the Janssen COVID-19 vaccine, click here.
Please All send me your Expert Opinion on the relations between these FINDINGS?
Linking Thrombotic Thrombocytopenia to ChAdOx1 nCov-19 Vaccination, AstraZeneca | Leaders in Pharmaceutical Business Intelligence (LPBI) Group
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