Complement factor 5 (C5) p.A252T mutation is prevalent in, but not restricted to, sub-Saharan Africa: implications for the susceptibility to meningococcal disease

The efficacy and safety of eculizumab in patients and the role of C5 polymorphisms

Eculizumab is an orphan drug with indications for extremely rare autoimmune disorders. It is primarily prescribed for use in patients with paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome; but is also highly effective in the treatment of myasthenia gravis, among others. By binding to the C5 protein in the complement system, eculizumab effectively inhibits cellular hemolysis and autoimmune reactions. Despite this effective treatment, some patients reported no improvement in symptoms. Genetic sequencing revealed three distinct C5 mutations in the non-responders and these polymorphisms appeared to be most prevalent among Japanese, Korean and African populations. Here, we present an overview of the current and potential future applications of eculizumab, as well as the disadvantages of eculizumab treatment in patients with C5 polymorphisms.

The Relationship between Complement Components C1R and C5 Gene Polymorphism and the Values of Blood Indices in Suckling Piglets

The main mechanism of innate immunity is the complement system. Its components include the protein products of the C1R and C5 genes, which are involved in the classical activation pathway as well as the inflammatory and cytolytic immune responses, respectively. The aim of this study was to determine the relationship between PCR-restriction fragment length polymorphism in C1R (726T > C) and C5 (1044A > C) genes, and the values of hematological and biochemical blood indices in suckling crossbred (Polish Large White × Polish Landrace × Duroc × Pietrain) piglets (n = 473), considering their age (younger, 21 ± 3 days, n = 274; older, 35 ± 3 days, n = 199) and health status. The frequencies of the C5 genotypes deviated from the Hardy-Weinberg expectations. Younger piglets, healthy piglets, piglets that deviated from physiological norms and older piglets with the C1R TT genotype all had lower white and red blood cell indices. In piglets with the C5 CC genotype, younger piglets, piglets that deviated from physiological norms and older piglets, a greater number and/or percentage of monocytes were recorded in the blood. Older piglets also showed an increase in the number of leukocytes and granulocytes, along with a tendency for a decrease in the percentage of lymphocytes in their blood. We concluded that a polymorphism in the C1R gene may exhibit a functional association or genetic linkage with other genes involved in the process of erythropoiesis. Furthermore the relationship between the C5 gene polymorphism and the number and/or percentage of monocytes in the blood may modify the body's defense abilities. Piglets with the CC genotype, having an increased number/proportion of these cells in their blood, probably display a weakened immune response to pathogens or a chronic stimulation of the immune system.

The first case report of complement component 7 deficiency in Qatar and a 10-year follow-up

Introduction

Neisseria meningitidis is a significant cause of bacterial meningitis and septicemia worldwide. Recurrent Neisseria meningitidis is frequently associated with terminal complement protein deficiency, including Complement component 7. This report discusses the first case of C7 deficiency in Qatar.

Case report

A 30-year-old Qatari man presented with a meningococcal infection, which was verified by a blood culture. He experienced two episodes of meningitis caused by an undetermined organism. His blood tests revealed low levels of CH50 and C7. His C7 gene testing revealed a homozygous mutation in exon 10 (c.1135G>C p.Gly379Arg), a mutation that has not been previously documented in Qatar. However, it has been observed in 1% of Moroccan-origin Israeli Jews who also exhibit C7 deficiency. Regular prophylactic quadrivalent vaccinations against types A, C, Y, and W-135 with azithromycin tabs were administered. Over the last 10 years of follow-up, he remained in good health, with no further meningitis episodes.

Conclusion

To our knowledge, this is the first confirmed case of C7 deficiency reported in the Arabian Gulf countries. Such rare diseases should be a public health priority. Awareness among medical practitioners and the community should help with early detection of C7 deficiency and the prevention of its consequences.

Clinical and Genetic Spectrum of a Large Cohort With Total and Sub-total Complement Deficiencies

The complement system is crucial for defense against pathogens and the removal of dying cells or immune complexes. Thus, clinical indications for possible complete complement deficiencies include, among others, recurrent mild or serious bacterial infections as well as autoimmune diseases (AID). The diagnostic approach includes functional activity measurements of the classical (CH50) and alternative pathway (AP50) and the determination of the C3 and C4 levels, followed by the quantitative analysis of individual components or regulators. When biochemical analysis reveals the causal abnormality of the complement deficiency (CD), molecular mechanisms remains frequently undetermined. Here, using direct sequencing analysis of the coding region we report the pathogenic variants spectrum that underlie the total or subtotal complement deficiency in 212 patients. We identified 107 different hemizygous, homozygous, or compound heterozygous pathogenic variants in 14 complement genes [C1Qβ (n = 1), C1r (n = 3), C1s (n = 2), C2 (n = 12), C3 (n = 5), C5 (n = 12), C6 (n = 9), C7 (n = 17), C8 β (n = 7), C9 (n = 3), CFH (n = 7), CFI (n = 18), CFP (n = 10), CFD (n = 2)]. Molecular analysis identified 17 recurrent pathogenic variants in 6 genes (C2, CFH, C5, C6, C7, and C8). More than half of the pathogenic variants identified in unrelated patients were also found in healthy controls from the same geographic area. Our study confirms the strong association of meningococcal infections with terminal pathway deficiency and highlights the risk of pneumococcal and auto-immune diseases in the classical and alternative pathways. Results from this large genetic investigation provide evidence of a restricted number of molecular mechanisms leading to complement deficiency and describe the clinical potential adverse events of anti-complement therapy.

The utility of complement assays in clinical immunology: A comprehensive review

The multi-tasking organ liver, which is the major synthesis site of most serum proteins, supplies humoral components of the innate, - including proteins of the complement system; and, less intensely, also of the acquired immune system. In addition to hepatocyte origins, C1q, factor D, C3, C7 and other protein components of the complement system are produced at various body locations by monocytes/macrophages, lymphocytes, adipocytes, endometrium, enterocytes, keratinocytes and epithelial cells; but the contribution of these alternate sites to the total serum concentrations is slight. The two major exceptions are factor D, which cleaves factor B of the alternative pathway derived largely from adipocytes, and C7, derived largely from polymorphonuclear leukocytes and monocytes/macrophages. Whereas the functional meaning of the extrahepatic synthesis of factor D remains to be elucidated, the local contribution of C7 may up- or downregulate the complement attack. The liver, however, is not classified as part of the immune system but is rather seen as victim of autoimmune diseases, a point that needs apology. Recent histological and cell marker technologies now turn the hands to also conceive the liver as proactive autoimmune disease catalyst. Hosting non-hepatocytic cells, e.g. NK cells, macrophages, dendritic cells as well as T and B lymphocytes, the liver outreaches multiple sites of the immune system. Immunopharmacological follow up of liver transplant recipients teaches us on liver-based presence of ABH-glycan HLA phenotypes and complement mediated ischemia/regeneration processes. In clinical context, the adverse reactions of the complement system can now be curbed by specific drug therapy. This review extends on the involvement of the complement system in liver autoimmune diseases and should allow to direct therapeutic opportunities.