C5 complement deficiency in a Saudi family, molecular characterization of mutation and literature review

Subcutaneous zilucoplan: Evaluation of reproductive toxicology

To further understand the safety profile of zilucoplan, reproductive toxicology studies in non-human primates (NHPs) were performed, including a male fertility study and a combined embryo-foetal development (EFD) and enhanced pre- and postnatal development (ePPND) study. Human transplacental transfer of zilucoplan was examined in an ex vivo human placental perfusion model of foetal exposure during pregnancy. By comparison with the positive control, a low transfer rate of 0.5 % was observed with a target blood zilucoplan concentration that mimics the therapeutic dose of 0.3 mg/kg used in clinical trials in patients with generalised myasthenia gravis. In each in vivo study, daily subcutaneous zilucoplan 1.0, 2.0 or 4.0 mg/kg or vehicle control were randomly assigned. Six male cynomolgus monkeys/group received treatment for 13 weeks (male fertility), 4 females/group received treatment for 80 days (EFD) and 16 females/group received treatment from gestation day 20 to delivery (∼140 days, ePPND). Developmental, reproductive and toxicokinetic effects were analysed. No zilucoplan-related reproductive effects were observed in the male fertility study. There were no effects on pregnancy outcome, number of viable foetuses or foetal development in the combined EFD/ePPND study. Overall pregnancy loss (including stillbirths and death during birth) was 25.0 % (4/16) in the control group compared with 37.5 % (6/16) in the zilucoplan-treated groups and was within the published range of pregnancy loss in cynomolgus monkeys. These reproductive toxicity studies demonstrate no adverse effect of zilucoplan on male fertility or maternal or embryo-foetal outcomes, and no pre- or postnatal toxicity in NHPs receiving daily zilucoplan. Data from the ex vivo placental transfer model and the lack of effect of FcRn-mediated transfer on zilucoplan suggest that placental transfer is low.

Investigation of Association of Complement 5 Genetic Polymorphisms with Sepsis and Sepsis-Induced Inflammatory Responses

Background

Complement 5 (C5) and C5a production play a pivotal role in the pathophysiology of sepsis. Strong evidence demonstrates an association of C5 gene polymorphisms with various inflammatory diseases. However, no current studies have explored the clinical relevance of C5 polymorphisms in sepsis.

Methods

Two C5 gene polymorphisms, rs17611 and rs2269067, were identified by genotyping in 636 sepsis patients and 753 controls in a Han Chinese population. C5 gene expression was detected via quantitative real-time PCR. C5a and proinflammatory cytokine production was measured by enzyme-linked immunosorbent assay. An Annexin V apoptosis assay was performed to assess cell apoptosis.

Results

Our results showed significantly lower frequencies of rs2269067 GC/CC genotypes or C allele in sepsis patients than healthy controls. The frequencies of rs17611 CC/CT genotypes or C allele were significantly overrepresented in both the septic shock and non-survivor subgroups. Patients with this sepsis-associated high-risk rs17611 C allele exhibited a significant increase in C5a, TNF-α and IL-6 production. However, no significant difference in C5a and downstream proinflammatory cytokine production was observed among patients with different rs2269067 genotypes. In addition, in vitro experiments showed an effect of recombinant C5a on enhancing LPS-stimulated IL-1β, IL-6 and TNF-α production and cell apoptosis in THP-1 monocytes.

Conclusion

The rs2269067 polymorphism conferred protection against sepsis susceptibility. The rs17611 polymorphism was associated with increased C5a production, which ultimately potentiated the secretion of downstream proinflammatory cytokines and conferred susceptibility to sepsis progression and poor prognosis.

Meningococcaemia causing necrotizing cellulitis associated with acquired complement deficiency after gastric bypass surgery: a case report

Background

Neisseria meningitidis has rarely been described as an agent of necrotic soft tissue infection.

Case presentation

We report a case of a septic shock with necrotizing cellulitis due to Neisseria meningitidis serogroup W, treated by urgent extensive surgical debridement followed by skin grafts. The invasive meningococcal disease occurred together with a complement deficiency, possibly acquired after bypass surgery that took place 1 year before.

Conclusions

Necrotic tissue infections should be considered part of the invasive meningococcal diseases spectrum and should prompt clinicians to look for complement deficiencies. Gastric bypass surgery associated malnutrition may be implicated but further verification is needed.

Invasive Meningococcal Disease Unraveling a Novel Mutation in the C5 Gene in a Portuguese Family

Although bacterial meningitis is a rare presentation of a congenital immunodeficiency, invasive meningococcal disease is classically associated with complement deficiencies. We report a patient from a consanguineous kindred presenting with an invasive meningococcal disease caused by serogroup B meningococcus that revealed an underlying C5 deficiency caused by a novel mutation in the C5 gene.

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

Complement C5 deficiency (C5D) is a rare primary immunodeficiency associated with recurrent infections, particularly meningitis, by Neisseria species. To date, studies to elucidate the molecular basis of hereditary C5D have included fewer than 40 families, and most C5 mutations (13 of 17) have been found in single families. However, the recently described C5 p.A252T mutation is reported to be associated with approximately 7% of meningococcal disease cases in South Africa. This finding raises the question of whether the mutation may be prevalent in other parts of Africa or other continental regions. The aim of this study was to investigate the prevalence of C5 p.A252T in Africa and other regions and discuss the implications for prophylaxis against meningococcal disease. In total, 2710 samples from healthy donors within various populations worldwide were analysed by quantitative polymerase chain reaction (qPCR) assay to detect the C5 p.A252T mutation. Eleven samples were found to be heterozygous for p.A252T, and nine of these samples were from sub-Saharan African populations (allele frequency 0·94%). Interestingly, two other heterozygous samples were from individuals in populations outside Africa (Israel and Pakistan). These findings, together with data from genomic variation databases, indicate a 0·5-2% prevalence of the C5 p.A252T mutation in heterozygosity in sub-Saharan Africa. Therefore, this mutation may have a relevant role in meningococcal disease susceptibility in this geographical area.

Novel Mutations Causing C5 Deficiency in Three North-African Families

The complement system plays a central role in defense to encapsulated bacteria through opsonization and membrane attack complex (MAC) dependent lysis. The three activation pathways (classical, lectin, and alternative) converge in the cleavage of C5, which initiates MAC formation and target lysis. C5 deficiency is associated to recurrent infections by Neisseria spp. In the present study, complement deficiency was suspected in three families of North-African origin after one episode of invasive meningitis due to a non-groupable and two uncommon Meningococcal serotypes (E29, Y). Activity of alternative and classical pathways of complement were markedly reduced and the measurement of terminal complement components revealed total C5 absence. C5 gene analysis revealed two novel mutations as causative of the deficiency: Family A propositus carried a homozygous deletion of two adenines in the exon 21 of C5 gene, resulting in a frameshift and a truncated protein (c.2607_2608del/p.Ser870ProfsX3 mutation). Families B and C probands carried the same homozygous deletion of three consecutive nucleotides (CAA) in exon 9 of the C5 gene, leading to the deletion of asparagine 320 (c.960_962del/p.Asn320del mutation). Family studies confirmed an autosomal recessive inheritance pattern. Although sharing the same geographical origin, families B and C were unrelated. This prompted us to investigate this mutation prevalence in a cohort of 768 North-African healthy individuals. We identified one heterozygous carrier of the p.Asn320del mutation (allelic frequency = 0.065 %), indicating that this mutation is present at low frequency in North-African population.

Eculizumab in Typical Hemolytic Uremic Syndrome (HUS) With Neurological Involvement

In typical hemolytic uremic syndrome (HUS) approximately 25% of patients show central nervous system (CNS) involvement often leading to serious long-term disabilities. We used the C5-complement inhibitor Eculizumab as rescue therapy. From 2011 to 2014, 11 children (median age 22 months, range 11-175) with enterohemorrhagic Escherichia coli-positive HUS requiring dialysis who had seizures (11/11) and/or were in a stupor or coma (10/11) were treated with Eculizumab. Two patients enrolled on the Safety and Efficacy Study of Eculizumab in Shiga-Toxin Producing E coli Hemolytic-Uremic Syndrome (STEC-HUS) each received 6 doses of Eculizumab, 3 patients 2 doses, and 6 patients 1 dose. Laboratory diagnostics of blood samples and magnetic resonance imaging (MRI) were performed as per center practice. Data were analyzed retrospectively. Cranial MRI was abnormal in 8 of 10 patients with findings in the basal ganglia and/or white matter. A 2-year-old boy with severe cardiac involvement and status epilepticus needed repeated cardio-pulmonary resuscitation and extracorporeal membrane oxygenation. He died 8 days after start of Eculizumab treatment. Two patients with hemorrhagic colitis and repeated seizures required artificial ventilation for 6 and 16 days, respectively. At the time of discharge, 1 patient showed severe neurological impairment and 1 mild neurological impairment. The 8 surviving patients experienced no further seizures after the first dose of Eculizumab. Three patients showed mild neurological impairment at discharge, whilst the remaining 5 showed no impairment. The platelets normalized 4 days (median) after the first dose of Eculizumab (range 0-20 days). The mean duration of dialysis after the first dose of Eculizumab was 14.1 ± 6.1 days. In children with typical HUS and CNS involvement early use of Eculizumab appears to improve neurological outcome. In severe HUS cases which progress rapidly with multiple organ involvement, late treatment with Eculizumab seems to show less benefit. We speculate that prophylactic Eculizumab therapy before development of neurological symptoms could be advantageous.

A complement C5 gene mutation, c.754G>A:p.A252T, is common in the Western Cape, South Africa and found to be homozygous in seven percent of Black African meningococcal disease cases

Patients with genetically determined deficiency of complement component 5 are usually diagnosed because of recurrent invasive Neisseria meningitidis infections. Approximately 40 individual cases have been diagnosed worldwide. Nevertheless, reports of the responsible genetic defects have been sporadic, and we know of no previous reports of C5 deficiency being associated with a number of independent meningococcal disease cases in particular communities. Here we describe C5 deficiency in seven unrelated Western Cape, South African families. Three different C5 mutations c.55C>T:p.Q19X, c.754G>A:p.A252T and c.4426C>T:p.R1476X were diagnosed in index cases from two families who had both presented with recurrent meningococcal disease. p.Q19X and p.R1476X have already been described in North American Black families and more recently p.Q19X in a Saudi family. However, p.A252T was only reported in SNP databases and was not associated with disease until the present study was undertaken in the Western Cape, South Africa. We tested for p.A252T in 140 patients presenting with meningococcal disease in the Cape Town area, and found seven individuals in five families who were homozygous for the mutation p.A252T. Very low serum C5 protein levels (0.1-4%) and correspondingly low in vitro functional activity were found in all homozygous individuals. Allele frequencies of p.A252T in the Black African and Cape Coloured communities were 3% and 0.66% and estimated homozygosities are 1/1100 and 1/22,500 respectively. In 2012 we reported association between p.A252T and meningococcal disease. Molecular modelling of p.A252T has indicated an area of molecular stress in the C5 molecule which may provide a mechanism for the very low level in the circulation. This report includes seven affected families indicating that C5D is not rare in South Africa.