Targeting C-Reactive Protein by Selective Apheresis in Humans: Pros and Cons.

C-reactive protein (CRP), the prototype human acute phase protein, may be causally involved in various human diseases. As CRP has appeared much earlier in evolution than antibodies and nonetheless partly utilizes the same biological structures, it is likely that CRP has been the first antibody-like molecule in the evolution of the immune system. Like antibodies, CRP may cause autoimmune reactions in a variety of human pathologies. Consequently, therapeutic targeting of CRP may be of utmost interest in human medicine. Over the past two decades, however, pharmacological targeting of CRP has turned out to be extremely difficult. Currently, the easiest, most effective and clinically safest method to target CRP in humans may be the specific extracorporeal removal of CRP by selective apheresis. The latter has recently shown promising therapeutic effects, especially in acute myocardial infarction and COVID-19 pneumonia. This review summarizes the pros and cons of applying this novel technology to patients suffering from various diseases, with a focus on its use in cardiovascular medicine.

Special Issue "C-Reactive Protein and Cardiovascular Disease: Clinical Aspects".

This Special Issue focuses on the clinical relevance of C-reactive protein [...].

Targeting C-Reactive Protein by Selective Apheresis in Humans: Pros and Cons

C-reactive protein (CRP), the prototype human acute phase protein, may be causally involved in various human diseases. As CRP has appeared much earlier in evolution than antibodies and nonetheless partly utilizes the same biological structures, it is likely that CRP has been the first antibody-like molecule in the evolution of the immune system. Like antibodies, CRP may cause autoimmune reactions in a variety of human pathologies. Consequently, therapeutic targeting of CRP may be of utmost interest in human medicine. Over the past two decades, however, pharmacological targeting of CRP has turned out to be extremely difficult. Currently, the easiest, most effective and clinically safest method to target CRP in humans may be the specific extracorporeal removal of CRP by selective apheresis. The latter has recently shown promising therapeutic effects, especially in acute myocardial infarction and COVID-19 pneumonia. This review summarizes the pros and cons of applying this novel technology to patients suffering from various diseases, with a focus on its use in cardiovascular medicine.

[CRP apheresis in acute myocardial infarction and COVID-19]. / CRP-Apherese bei akutem Myokardinfarkt bzw. COVID-19.

C­reactive protein (CRP) is the best-known acute phase protein. In humans, inflammation and infection are usually accompanied by an increase in CRP levels in the blood, which is why CRP is an important biomarker in daily clinical routine. CRP can mediate the initiation of phagocytosis by labeling damaged cells. This labeling leads to activation of the classical complement pathway (up to C4) and ends in the elimination of pathogens or reversibly damaged or dead cells. This seems to make sense in case of an external wound of the body. However, in the case of "internal wounds" (e.g., myocardial infarction, stroke), CRP induces tissue damage to potentially regenerable tissue by cell labeling, which has corresponding deleterious effects on cardiac and brain tissue or function. The described labeling of ischemic but potentially regenerable cells by CRP apparently also occurs in coronavirus disease 2019 (COVID-19). Parts of the lung become ischemic due to intra-alveolar edema and hemorrhage, and this is accompanied by a dramatic increase in CRP. Use of selective immunoadsorption of CRP from blood plasma ("CRP apheresis") to rapidly and efficiently lower the fulminant CRP load in the body fills this pharmacotherapeutic gap. With CRP apheresis, it is possible for the first time to remove this pathological molecule quickly and efficiently in clinical practice.

Case Report: C-Reactive Protein Apheresis in a Patient With COVID-19 and Fulminant CRP Increase.

Background: Plasma levels of C-reactive protein (CRP), induced by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) triggering COVID-19, can rise surprisingly high. The increase of the CRP concentration as well as a certain threshold concentration of CRP are indicative of clinical deterioration to artificial ventilation. In COVID-19, virus-induced lung injury and the subsequent massive onset of inflammation often drives pulmonary fibrosis. Fibrosis of the lung usually proceeds as sequela to a severe course of COVID-19 and its consequences only show months later. CRP-mediated complement- and macrophage activation is suspected to be the main driver of pulmonary fibrosis and subsequent organ failure in COVID-19. Recently, CRP apheresis was introduced to selectively remove CRP from human blood plasma. Case Report: A 53-year-old, SARS-CoV-2 positive, male patient with the risk factor diabetes type 2 was referred with dyspnea, fever and fulminant increase of CRP. The patient's lungs already showed a pattern enhancement as an early sign of incipient pneumonia. The oxygen saturation of the blood was ≤ 89%. CRP apheresis using the selective CRP adsorber (PentraSorb® CRP) was started immediately. CRP apheresis was performed via peripheral venous access on 4 successive days. CRP concentrations before CRP apheresis ranged from 47 to 133 mg/l. The removal of CRP was very effective with up to 79% depletion within one apheresis session and 1.2 to 2.14 plasma volumes were processed in each session. No apheresis-associated side effects were observed. It was at no point necessary to transfer the patient to the Intensive Care Unit or to intubate him due to respiratory failure. 10 days after the first positive SARS-CoV-2 test, CRP levels stayed below 20 mg/l and the patient no longer exhibited fever. Fourteen days after the first positive SARS-CoV-2 test, the lungs showed no sign of pneumonia on X-ray. Conclusion: This is the first report on CRP apheresis in an early COVID-19 patient with fulminant CRP increase. Despite a poor prognosis due to his diabetes and biomarker profile, the patient was not ventilated, and the onset of pneumonia was reverted.

Successful Treatment of a 39-Year-Old COVID-19 Patient with Respiratory Failure by Selective C-Reactive Protein Apheresis.

BACKGROUND High C-reactive protein (CRP) plasma levels in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are associated with poor prognosis. CRP, by activating the classical complement pathway and interacting with macrophages via Fc gamma receptors, can cause pulmonary inflammation with subsequent fibrosis. Recently, we have reported first-in-man CRP apheresis in a "high-risk" COVID-19 patient. Treatment was unfortunately clinically unsuccessful. Here, we report on successful CRP apheresis treatment in a "lower-risk" COVID-19 patient with respiratory failure. CASE REPORT A 39-year-old male patient suffering from fatigue, dyspnea, and fever for 4 days was referred to us. The patient had to be intubated. Polymerase chain reaction (PCR) analysis of a throat smear revealed SARS-CoV-2 infection. Mutation analysis revealed the VOC B. 1.1.7 variant. CRP levels were 79.2 mg/L and increased to 161.63 mg/L. Procalcitonin (PCT) levels were continuously normal (<0.5 ng/ml). Antibiotic therapy was started to avoid bacterial superinfection. CRP apheresis was performed once via central venous access. CRP levels declined from a maximum of 161.63 mg/L to 32.58 mg/L. No apheresis-associated adverse effects were observed. Subsequently, CRP plasma levels declined day by day and normalized on day 5. The patient was extubated on day 5 and discharged from the Intensive Care Unit (ICU) on day 6. A second low CRP peak (maximum 22.41 mg/L) on day 7 remained clinically inapparent. The patient was discharged in good clinical condition with a CRP level of 6.94 mg/L on day 8. CONCLUSIONS SARS-CoV-2 infection can induce an uncontrolled CRP-mediated autoimmune response of ancient immunity. In this patient, the autoimmune response was potently and successfully suppressed by early selective CRP apheresis.

C-Reactive Protein Triggers Cell Death in Ischemic Cells.

C-reactive protein (CRP) is the best-known acute phase protein. In humans, almost every type of inflammation is accompanied by an increase of CRP concentration. Until recently, the only known physiological function of CRP was the marking of cells to initiate their phagocytosis. This triggers the classical complement pathway up to C4, which helps to eliminate pathogens and dead cells. However, vital cells with reduced energy supply are also marked, which is useful in the case of a classical external wound because an important substrate for pathogens is disposed of, but is counterproductive at internal wounds (e.g., heart attack or stroke). This mechanism negatively affects clinical outcomes since it is established that CRP levels correlate with the prognosis of these indications. Here, we summarize what we can learn from a clinical study in which CRP was adsorbed from the bloodstream by CRP-apheresis. Recently, it was shown that CRP can have a direct effect on blood pressure in rabbits. This is interesting in regard to patients with high inflammation, as they often become tachycardic and need catecholamines. These two physiological effects of CRP apparently also occur in COVID-19. Parts of the lung become ischemic due to intra-alveolar edema and hemorrhage and in parallel CRP increases dramatically, hence it is assumed that CRP is also involved in this ischemic condition. It is meanwhile considered that most of the damage in COVID-19 is caused by the immune system. The high amounts of CRP could have an additional influence on blood pressure in severe COVID-19.

Complement Activation in Kidneys of Patients With COVID-19.

Most patients who became critically ill following infection with COVID-19 develop severe acute respiratory syndrome (SARS) attributed to a maladaptive or inadequate immune response. The complement system is an important component of the innate immune system that is involved in the opsonization of viruses but also in triggering further immune cell responses. Complement activation was seen in plasma adsorber material that clogged during the treatment of critically ill patients with COVID-19. Apart from the lung, the kidney is the second most common organ affected by COVID-19. Using immunohistochemistry for complement factors C1q, MASP-2, C3c, C3d, C4d, and C5b-9 we investigated the involvement of the complement system in six kidney biopsies with acute kidney failure in different clinical settings and three kidneys from autopsy material of patients with COVID-19. Renal tissue was analyzed for signs of renal injury by detection of thrombus formation using CD61, endothelial cell rarefaction using the marker E-26 transformation specific-related gene (ERG-) and proliferation using proliferating cell nuclear antigen (PCNA)-staining. SARS-CoV-2 was detected by in situ hybridization and immunohistochemistry. Biopsies from patients with hemolytic uremic syndrome (HUS, n = 5), severe acute tubular injury (ATI, n = 7), zero biopsies with disseminated intravascular coagulation (DIC, n = 7) and 1 year protocol biopsies from renal transplants (Ctrl, n = 7) served as controls. In the material clogging plasma adsorbers used for extracorporeal therapy of patients with COVID-19 C3 was the dominant protein but collectin 11 and MASP-2 were also identified. SARS-CoV-2 was sporadically present in varying numbers in some biopsies from patients with COVID-19. The highest frequency of CD61-positive platelets was found in peritubular capillaries and arteries of COVID-19 infected renal specimens as compared to all controls. Apart from COVID-19 specimens, MASP-2 was detected in glomeruli with DIC and ATI. In contrast, the classical pathway (i.e. C1q) was hardly seen in COVID-19 biopsies. Both C3 cleavage products C3c and C3d were strongly detected in renal arteries but also occurs in glomerular capillaries of COVID-19 biopsies, while tubular C3d was stronger than C3c in biopsies from COVID-19 patients. The membrane attack complex C5b-9, demonstrating terminal pathway activation, was predominantly deposited in COVID-19 biopsies in peritubular capillaries, renal arterioles, and tubular basement membrane with similar or even higher frequency compared to controls. In conclusion, various complement pathways were activated in COVID-19 kidneys, the lectin pathway mainly in peritubular capillaries and in part the classical pathway in renal arteries whereas the alternative pathway seem to be crucial for tubular complement activation. Therefore, activation of the complement system might be involved in the worsening of renal injury. Complement inhibition might thus be a promising treatment option to prevent deregulated activation and subsequent collateral tissue injury.

First-in-Man: Case Report of Selective C-Reactive Protein Apheresis in a Patient with SARS-CoV-2 Infection.

BACKGROUND C-reactive protein (CRP) plasma levels in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel viral disease, are surprisingly high. Pulmonary inflammation with subsequent fibrosis in SARS-CoV-2 infection is strongly accelerated. Recently, we have developed CRP apheresis to selectively remove CRP from human plasma. CRP may contribute to organ failure and pulmonary fibrosis in SARS-CoV-2 infection by CRP-mediated complement and macrophage activation. CASE REPORT A 72-year-old male patient at high risk was referred with dyspnea and fever. Polymerase chain reaction analysis of throat smear revealed SARS-CoV-2 infection. CRP levels were ~200 mg/L. Two days after admission, CRP apheresis using the selective CRP adsorber (PentraSorb® CRP) was started. CRP apheresis was performed via peripheral venous access on days 2, 3, 4, and 5. Following a 2-day interruption, it was done via central venous access on days 7 and 8. Three days after admission the patient was transferred to the intensive care unit and intubated due to respiratory failure. Plasma CRP levels decreased by ~50% with peripheral (processed blood plasma ≤6000 mL) and by ~75% with central venous access (processed blood plasma ≤8000 mL), respectively. No apheresis-associated side effects were observed. After the 2-day interruption in apheresis, CRP levels rapidly re-increased (>400 mg/L) and the patient developed laboratory signs of multi-organ failure. When CRP apheresis was restarted, CRP levels and creatinine kinases (CK/CK-MB) declined again. Serum creatinine remained constant. Unfortunately, the patient died of respiratory failure on day 9 after admission. CONCLUSIONS This is the first report on CRP apheresis in a SARS-CoV-2 patient. SARS-CoV-2 may cause multi-organ failure in part by inducing an excessive CRP-mediated autoimmune response of the ancient innate immune system.