Basic and clinical breakthroughs!

*For medical professionals to read and reference Follow the footsteps of experts to see the frontier progress.
Looking back on 2021, although the world is still in the quagmire of the new crown pneumonia epidemic, this has not stopped the enthusiasm of experts in the field of rheumatism and immunity.
Academic experts and scholars have made great efforts, from basic research to clinical treatment, with frequent successes, and have achieved many research results in many fields of the discipline, which is exciting
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 On January 22-23, 2022, under the guidance of the Rheumatology and Immunology Branch of the Chinese Medical Association and sponsored by the medical community media, "Riding the Wind and Waves-2021 Annual Inventory of Rheumatology" was successfully held online
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Professor Yang Chengde, Department of Rheumatology and Immunology, Ruijin Hospital Affiliated to Shanghai Jiaotong University School of Medicine, shared the research progress of antiphospholipid syndrome (APS) in 2021 during the meeting
.

 A retrospective history of APS research APS is a non-inflammatory autoimmune disease clinically manifested by recurrent arteriovenous thrombosis, habitual abortion, and thrombocytopenia
.

High titers of anticardiolipin antibody (aCL), lupus anticoagulant (LA), and anti-β2 glycoprotein I (anti-β2GPⅠ) antibody can be detected in the serum of patients
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 APS can be divided into primary and secondary.
Secondary APS is commonly secondary to systemic lupus erythematosus (SLE), Sjögren's syndrome and other connective tissue diseases, of which SLE is the most common cause
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 The research on APS can be traced back to 1983.
Graham Hughes and other researchers first reported the correlation between syphilis serum false positive test (BFP-STS), LA and clinical manifestations of APS, and established an ELISA method to detect antiphospholipid antibody (aPL).
It is a major milestone event for APS
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 The disease was named anticardiolipin antibody syndrome in 1986 because high titers of aCL were found to be detectable in patients with recurrent arteriovenous thrombosis and habitual abortion in a group of studies
.

It was officially named APS in 1987, also known as Hughes syndrome
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 The second milestone was the discovery of aPL associated with thrombosis and recurrent miscarriage in 1990, targeting the target antigen β2GPI
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 The diagnosis of APS is both a key point and a difficult point.
The diagnosis method of APS is still following the 2006 Sydney classification criteria (Figure 1).
The diagnosis of APS must meet the following 1 clinical criteria (2 items in total) and 1 laboratory criteria (3 items in total)
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 Clinical criteria: Vascular embolism: One or more arteriovenous thrombosis in any tissue or organ
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Sick pregnancy: 1) 3 or more consecutive spontaneous abortions before 10 weeks of pregnancy; 2) 1 or more stillbirths after 10 weeks of pregnancy; 3) 1 or more eclampsia, preeclampsia and placental function Inhomogeneous symptoms
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 Laboratory criteria: At least 2 tests and at least 12 weeks apart
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LA positive; IgG and/or IgM aCL positive (ie >40GPL or MPL, or greater than 99%); anti-β2GP1 antibody positive
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 Figure 1: Sydney Classification Criteria for APS Diagnosis 2006 In addition to the recognized Sydney classification criteria for APS diagnosis described above, clinical manifestations outside the criteria are also associated with risk of aPL and thrombosis, and recognition of these can influence treatment decisions
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 First, for patients with clinical symptoms consistent with disease manifestations but negative laboratory tests, if serum markers outside the diagnostic criteria are detected, such as anti-phosphatidylserine prothrombin complex antibody (aPS/PT), anti-vimentin antibody (Anti-vimenti), platelet factor 4 (PF4), etc.
, can be called seronegative APS (SNAPS)
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Studies have found that if patients have positive aPL outside the two diagnostic criteria, such patients are more likely to have APS-related symptoms [1]
.

 In addition, the team of Professor Zeng Xiaofeng of Peking Union Medical College Hospital also conducted research on the same markers mentioned above, and also believed that aPL outside the diagnostic criteria has a certain specificity and sensitivity for the diagnosis of APS, and also has a certain value for the diagnosis of SNAPS.
2]
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 Figure 2: Distribution of positive SNAPS patients in ≥1 non-standard test positive for patients who met laboratory criteria for serological testing, but did not meet clinical classification criteria, but developed symptoms such as reticular cyanosis, valvular heart disease Patients with aPL-related symptoms such as thrombocytopenia are diagnosed as probable APS (probable APS)
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 Starting from basic research, in-depth exploration of the pathogenesis of APS The mechanism of APS thrombosis is mainly related to the activation of the vascular system cell components (platelets, vascular endothelial cells, neutrophils, monocytes) by antigen-antibody complexes [3]
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The mechanism of APS pathological pregnancy is related to aPL affecting permeable cells, leading to thrombosis, causing uteroplacental vascular obstruction, resulting in insufficient blood supply to the placenta, and ultimately leading to the occurrence of pathological pregnancy such as fetal ischemia, hypoxia, and miscarriage [4]
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 In this regard, Professor Yang Decheng introduced his team's experimental research on the pathogenicity of antibodies
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In this study, after purifying β2GPI by affinity chromatography, it was found that autologous carbohydrate components were significantly increased in malignant APS (CAPS)
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This study shows that the pathogenicity of anti-β2GPⅠ antibodies can be identified by the carbohydrate group [5]
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 In 2021, a blockbuster study on APS was published in the authoritative journal Science, and it was found that the cell surface receptor of aPL, activated endothelial cell protein c (EPCR), mediated the cellular internalization of aPL
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Binding of aPL to EPCR-lysobisphosphatidic acid (LBPA) leads to activation of coagulation and interferon-α (TNF-α) production in dendritic cells, which in turn leads to the production of more B1a cells, which are aPL , which further activates the EPCR receptor to produce aPL, which is the self-amplification mechanism of aPL [6]
.

The results of this study have also been validated clinically.
For example, over time, it can be observed that the antibody titers in aPL-positive patients are getting higher and higher
.

 Figure 3: The mechanism of pregnancy and thrombosis of APS The neutrophil extracellular sterilization network (NETs) is a special structure that neutrophils release the nuclear substance to the outside of the cell, which has bactericidal ability.
It also has important implications in pathogenesis
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 Compared with healthy controls, APS patients had higher numbers of low-density neutrophils and showed higher levels of activation
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Studies have reported that in APS patients with a higher risk of thrombosis, the concentration of NETs is positively correlated with activated protein C resistance [7]
.

This may reveal that NETs are involved in thrombosis and miscarriage by mediating the activity of protein
C.

 Defibrotide, a drug currently approved for the treatment of transplant-related veno-occlusive disease, inhibits aPL-stimulated neutrophils to produce NETs
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In addition, animal experiments also found that Defibrotide can inhibit aPL to accelerate the formation of venous thrombosis and NETs in mice with venous thromboembolism [8]
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 There are also two new findings on the pathogenic mechanism of aPL
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First, some studies have discovered a new pathway of aPL, that is, after aPL activates ApoER2, it further activates cells through the PP2A-C pathway, resulting in intrauterine eclampsia and miscarriage [9]
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 Another study on exosomes found that apolipoprotein H (APOH) (also known as β2GPⅠ) was higher in APS
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The researchers also induced miscarriages and stillbirths by infusing APOH into mice intravenously
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It can be seen that exosomes containing APOH are involved in the occurrence and development of aPL[10]
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 Keeping pace, committed to APS clinical research About APS clinical research, Professor Yang Chengde first introduced an article published by his team in Rheumatology
.

Primary APS patients without any central nervous system symptoms, or aPL carriers are more common clinically, and bilateral white matter hyperintensities can be seen in such patients during head MRI (Fig.
(Figure 4B), subacute cerebral infarction (Figure 4C), and multiple lacunar infarction (Figure 4D) and other abnormal symptoms [11]
.

 Figure 4: Magnetic resonance image of the patient's head Subsequently, Prof.
Chengde Yang conducted a cohort study, which included 28 aPL carriers and 44 APS patients
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The results showed that compared with the normal group, the subjects in the experimental group had a significantly higher rate of 4 kinds of neurological lesions, which may suggest that we need to strengthen the prevention of neurological lesions in APS patients in clinical practice
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 1.
New clinical markers The new clinical markers of APS have also made new progress
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 It has been reported that amyloid β1-40, a pro-inflammatory peptide associated with vasculitis, is a novel marker of endothelial dysfunction and atherothrombosis associated with APS [12]
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 In addition, the researchers identified two novel biomarkers in urine by mass spectrometry analysis, namely chemokine (CXCL12) and platelet-derived growth factor subunit B (PDGFB)
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It was subsequently found that compared with patients with abnormal pregnancy APS, the level of CXCL12 in the urine of patients with thrombotic APS was higher, and the level of BPDGFB in the urine of patients with abnormal pregnancy APS was higher [13]
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Growth differentiation factor-15 (GDF-15), a pro-inflammatory cytokine, is considered a potential biomarker of cardiovascular disease (CVD) risk in APS [14]
.

 2.
What is the progress of APS treatment? In terms of treatment, Professor Yang Chengde's team used rituximab injection to treat 6 cases of thrombotic APS patients, and found that the antibody level of the patients decreased significantly, and there was no recurrence during the follow-up process.
It shows that rituximab injection has certain clinical value in the treatment of refractory thrombotic APS[15]
.

 In addition, studies have revealed that discontinuation of oral anticoagulants may be safe in SLE patients with persistent seronegative aPL [16]; another study of novel targeted anticoagulants included 115 subjects The patients were treated with targeted anticoagulant drugs and conventional anticoagulant drug warfarin respectively, and the results showed that the therapeutic effect of warfarin was better, and the application of targeted anticoagulant drugs in APS needs further research to prove [17]
.

 3.
Pay attention to the progress of the prognosis of APS One study conducted a group study on the prognosis of APS
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Group A included 61 subjects with secondary APS; group B included 56 subjects with cardiovascular risk and arterial thrombosis; and group C included 61 subjects with 3 aPL-positive thrombus
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 Follow-up studies have shown that compared with other groups, group B has higher thrombotic events and mortality, which suggests that patients with cardiovascular risk and arterial thrombosis need to be vigilant in treatment [18]
.

 Figure 5: Event-free survival rate of 3 groups during follow-up A study that observed the prognosis of APS patients for 38 years found that APS patients with persistent moderate to low thrombocytopenia may have a worse prognosis [19]
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In addition, the incidence of complications in patients with APS is equal to or higher than that in patients with rheumatoid arthritis (RA), and it is necessary to improve the prevention awareness of cardiovascular and depression in patients with APS [20]
.

 It's hammered! The risk of thrombosis increases after the new crown virus.
After the new crown virus hit the world on a large scale, the rheumatism and immunity team of Peking Union Medical College Hospital took the lead in reporting in the New England Journal of Medicine the discovery of higher aPL titers in the serum of patients with severe new crown virus infection.
It is speculated that This may be related to thrombosis in patients [21]
.

After further large sample study, it was found that the infection rate of severe new coronavirus and the positive rate of aPL were positively correlated [22]
.

 Table 1: Relationship between ACL IgG and disease severity, platelet count, and anticoagulation requirements.
A study of non-standard aPL found that patients had elevated antiprothrombin antibody (aPT) titers after 2019-nCoV infection [ 23]
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Lipid-bound aPL has been detected in patients with 2019-nCoV infection, and these patients with detected antibodies are more likely to develop severe disease
.

Isolation of lipid-bound aPL in patients induces proinflammatory and prothrombotic responses in monocytes and endothelial cells in vitro, while promoting thrombosis in mice [24]
.

 The researchers used affinity chromatography to purify aPL in patients with 2019-nCoV, and further studied the model in which aPL promotes thrombosis and induces abortion in vitro.
It has been confirmed that aCL derived from new coronary pneumonia is pathogenic [25]
.

 Two back-to-back studies, published in the New England Journal of Medicine in 2021, found that some patients experienced symptoms of blood clots and thrombocytopenia after receiving the Oxford AstraZeneca Covid-19 vaccine, due to the development of anti-PF4 in patients after vaccination - Autoantibodies to heparin complexes [26]
.

The antibody can activate platelets and lead to thrombosis.
After platelet activation, more PF4 will be released, forming a vicious circle
.

 In January this year, Prof.
Chengde Yang's research team studied the changes in aPL levels related to thrombus before and after vaccination with the new crown vaccine, and found that after vaccination with inactivated vaccines, the levels of aPL, anti-β2GP1 antibodies, anti-PS/PT antibodies and other antibodies were not obvious.
Added [27]
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Large follow-up studies lasting six months also showed no increased risk of thrombosis
.

It can be seen that China's inactivated new crown vaccine has a small risk of thrombosis and is relatively safe
.

 Figure 6: Summary of changes in thrombosis-related aPL levels before and after vaccination with the inactivated COVID-19 vaccine in China.
APS is a type of non-inflammatory autoimmune disease that occurs frequently in women.
It is gradually clear, but the diagnosis of APS is still a difficult problem
.

 In 2021, there will be many major advances in basic research related to APS: the self-amplification mechanism of aPL has been discovered; NETs may participate in the formation of thrombosis and the occurrence of abortion by mediating the activity of protein
C.

 Clinical studies are also fruitful: prevention of neurological lesions in APS patients needs to be strengthened in clinical practice; rituximab has certain clinical value in the treatment of refractory thrombotic APS; warfarin is more effective in APS than targeted anticoagulants.
The application effect is better
.

 The study also confirmed the pathogenicity of aCL derived from 2019-nCoV, indicating the need to strengthen the prevention and control of the epidemic
.

It is worth mentioning that China's inactivated new crown vaccine has a small risk of thrombosis and is relatively safe
.

References: [1] Kimon Stamatelopoulos, et al.
Clinical value of amyloid-beta1-40 as a marker of thrombo-inflammation in antiphospholipid syndrome.
Rheumatology.
[2] Xiaofeng Zeng, et al.
Evaluation of the Diagnostic Value of Non- criteria Antibodies for Antiphospholipid Syndrorome Patients in a Chinese Cohort,Frontiers in Immunology.
[3] Simantow,R,et al.
(1995).
Journal of Clinical Investigation 96(5):2211-2219.
[4] Nat Rev Rheumatol.
2011 Jun;7(6):330-9[5] Chengde Yang, et al.
Characteristics of purified anti-β2GPI IgG N-glycosylation associate with thrombotic, obstetric and catastrophic antiphospholipid syndrome.
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[6 ] Wolfram Ruf, et al.
Lipid presentation by the protein C receptor links coagulation with autoimmunity.
Science.
2021 March.
[7] Jason S.
knight MD, phD, et al.
Defibrotide inhibits antiphospholipid antibody-mediated NET formation and venous thrombosis.
Arthritis Rheumatology.
[8] Ingris Pabinger, et al.
Neutrophil subpopulations and their activation potential in patients with antiphospholipid syndrome and healthy individuals.
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[9] Denis Wahl, et al.
A new pro-thrombotic mechanism of neutrophil extracelular traps in antiphospholipid syndrome: impact on activated protein Cresistance.
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[10] Chieko MineophD, et al.
Protein Phosphatase 2A Activation Via ApoER2 in Trophoblasts Drives Preeclampsia in a Mouse Model of the Antiphospholipid syndrome.
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[11] Xiaoping wan, et al.
Exosome-Contained APOH Associated with Antiphospholipid Syndrome.
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[12] Chengde Yang, et al.
The high prevalence if abnormal magnetic resonance imaging findings in non-neuropsychiatric patients with persistently positive anti-phospholipid antibodies.
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[13] Chengde Yang, et al.
Urine Proteomics Differentiate Primary Thrombotic Antiphospholipid Syndrome From Obstetric Antiphospholipid Syndrome.
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[14] Chengde Yang,et al.
Rituximab in thrombotic primary antiphospholipid syndrome: a pilot study from a single centre in China.
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[15] Petros P.
Sfikakis, et al.
Growth differentiation factor 15 (GDF-15) as potential cardiovascular risk biomarker in antiphospholipid syndrome.
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[16] Fabrizio Conti, et al.
“Non-criteria antiphospholipid antibodies”: bridging the gap between seropositive and seronegative antiphospholipid syndrome, Rheumatology.
[17] Andrea Doria,et al.
Prevalence, outcome and management of patients with SLE and secondary antiphospholipid antibody syndrome after aPL seroconversion.
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[18] Gentian Denas,et al.
Trial of Rivaroxaban in AntiPhospholipid Syndrome (TRAPS):Two-year outcomes after the study closure .
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[19] Tatsuya Atsumi, et al.
Morbidity and mortality in antiphospholipid syndrome based on cluster analysis: a 10-year longitudinal cohort study.
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[20] Jose Pardos-Gea,et al.
Persistent thrombocytopenia predicts poor long- term survival in patients with antiphospholipidsyndrome: a 38-year follow-up study.
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[21] Lupus anticoagulant and abnormal coagulation texts in patients with covid-19, the new england journal of medicine.
[22] Marvin Fritzler, et al.
Anticardiolipin and other antiphospholipid antibodies in critically ill COVID-19 positive and negative patients, Rheumatic Diseases.
[23] Katrin BM, et al.
Anti-prothrombin autoantibodies enriched after infection with SARS-CoV-2 and influenced by strength of antibody response against SARS- CoV-2 proteins.
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[24] Karl J,et al.
Pathogenic lipid-binding antiphospholipid antibodies are associated with severity of COVID-19.
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[25] Jason S.
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Expert Profile Professor Yang Chengde Director of the Rheumatology Department of Shanghai Ruijin Hospital Vice Chairman of the Chinese Society of Rheumatology Vice Chairman of the Rheumatology Committee of the Chinese Medical Association Former Chairman of the Shanghai Rheumatology Association