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.

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.

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.

Selective Apheresis of C-Reactive Protein for Treatment of Indications with Elevated CRP Concentrations.

Almost every kind of inflammation in the human body is accompanied by rising C-reactive protein (CRP) concentrations. This can include bacterial and viral infection, chronic inflammation and so-called sterile inflammation triggered by (internal) acute tissue injury. CRP is part of the ancient humoral immune response and secreted into the circulation by the liver upon respective stimuli. Its main immunological functions are the opsonization of biological particles (bacteria and dead or dying cells) for their clearance by macrophages and the activation of the classical complement pathway. This not only helps to eliminate pathogens and dead cells, which is very useful in any case, but unfortunately also to remove only slightly damaged or inactive human cells that may potentially regenerate with more CRP-free time. CRP action severely aggravates the extent of tissue damage during the acute phase response after an acute injury and therefore negatively affects clinical outcome. CRP is therefore a promising therapeutic target to rescue energy-deprived tissue either caused by ischemic injury (e.g., myocardial infarction and stroke) or by an overcompensating immune reaction occurring in acute inflammation (e.g., pancreatitis) or systemic inflammatory response syndrome (SIRS; e.g., after transplantation or surgery). Selective CRP apheresis can remove circulating CRP safely and efficiently. We explain the pathophysiological reasoning behind therapeutic CRP apheresis and summarize the broad span of indications in which its application could be beneficial with a focus on ischemic stroke as well as the results of this therapeutic approach after myocardial infarction.

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.