C7 complement deficiency in an Israeli Arab village

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.

Genetic bases of C7 deficiency: systematic review and report of a novel deletion determining functional hemizygosity

Primary complement system (C) deficiencies are rare but notably associated with an increased risk of infections, autoimmunity, or immune disorders. Patients with terminal pathway C-deficiency have a 1,000- to 10,000-fold-higher risk of Neisseria meningitidis infections and should be therefore promptly identified to minimize the likelihood of further infections and to favor vaccination. In this paper, we performed a systematic review about clinical and genetic patterns of C7 deficiency starting from the case of a ten-year old boy infected by Neisseria meningitidis B and with clinical presentation suggestive of reduced C activity. Functional assay via Wieslab ELISA Kit confirmed a reduction in total C activity of the classical (0.6% activity), lectin (0.2% activity) and alternative (0.1% activity) pathways. Western blot analysis revealed the absence of C7 in patient serum. Sanger sequencing of genomic DNA extracted from peripheral blood of the patient allowed the identification of two pathogenetic variants in the C7 gene: the already well-characterized missense mutation G379R and a novel heterozygous deletion of three nucleotides located at the 3'UTR (c.*99_*101delTCT). This mutation resulted in an instability of the mRNA; thus, only the allele containing the missense mutation was expressed, making the proband a functional hemizygote for the expression of the mutated C7 allele.

Pediatric allergy and immunology in Israel

After the geographic and sociodemographic settings as well as the health care in Israel are briefly described, the scope of pediatric allergy and immunology in Israel is presented. This includes specific disorders commonly encountered, the environment that induces symptoms, the specialists who treat them, and the common challenges of patients, parents, doctors, and allied health personnel who collaborate to manage the maladies and patient care. Allergies usually affect some overall 15-20% of the pediatric population. The main allergens are inhaled, ingested, or injected (insects stings). Generally, the incidence of the various allergens affecting children in Israel, is similar to other parts of the Western world. Owing to the high consanguinity rate in the Israeli population, the prevalence of the various immunodeficiency conditions (in the adaptive as well as the innate system) is higher than that reported worldwide. Pediatric allergists/immunologists also treat autoimmune disorders affecting the pediatric group. Pediatric allergy and clinical immunology are not separate specialties. The 25 specialists who treat children with allergic/immunologic diseases have undergone a basic training in Pediatrics. They also received an additional 2-yr training in allergy and clinical immunology and then have to pass the board examinations. They work mainly in pediatric allergy units, in several hospitals that are affiliated to the five medical schools in the country. Aside from clinical work, most of the centers are also heavily involved in clinical and basic research in allergy and immunology.

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Hereditary complement C7 deficiency in nine families: Subtotal C7 deficiency revisited

Deficiencies in terminal complement components, including the component C7, are uncommon and associated with an increased risk of recurrent systemic neisserial infection. A total of 22 molecular defects have been reported in the C7 gene with both complete (C7Q0) and subtotal (C7SD) C7 deficiencies. In this study we report the molecular basis of nine new cases of C7 deficiencies that were characterized by exon-specific sequence analysis. Seven different C7 gene mutations were identified corresponding to small deletions (n=2), splice site changes (n=1) and single base pair substitutions leading to nonsense (n=1) or missense (n=3) mutations. Altogether, three changes of the C7 gene (G357R, R499S and 5' splice donor site of intron 16) account for half of the molecular defects which emphasize that a restricted number of molecular abnormalities are involved in this deficiency. We identified two patients with combined C7Q0/C7SD(R499S) and established the C7SD(R499S) frequency at about 1% in normal Caucasian population. We demonstrated that C7(R499S) mutant protein is retained in the endoplasmic reticulum whereas the wild-type C7 is located in the Golgi apparatus. Our results provide evidence that R499S represents a loss-of-function polymorphism of C7 due to a defective folding of the protein.

Two Mutations of the C7 Gene, c.1424G > A and c.281-1G > T, in Two Korean Families

Complement C7 deficiency is associated with increased susceptibility to meningococcal infection. The genetic alterations of C7 deficiency are known to be sporadic and heterogeneous worldwide. We investigated molecular basis of C7 deficiency in two unrelated Korean families, in which the index cases suffered from meningococcal meningitis. Exon-specific PCR and direct sequencing of the C7 gene revealed two different mutations: c.1424G > A and c.281-1G > T. In family 1, index case and her brother revealed a homozygous mis-sense mutation (c.1424G > A), a novel mutation, which results in the change of cysteine to tyrosine (C475Y) in exon 10. Index case in family 2 was found to be a homozygote carrying point mutation at the 3' splice acceptor site of intron 3 (c.281-1G > T), which was previously reported in a Korean C7-deficient subject.

Two novel mutations in the C7 gene in a Korean patient with complement C7 deficiency

Complement C7 deficiency is an autosomal recessive disorder well known to be associated with increased susceptibility to meningococcal infection and has mostly been reported in Caucasians. In the Korean population, no case of C7 deficiency has been reported to date. Recently we experienced an 11-yr-old girl with meningococcal meningitis who was diagnosed as having C7 deficiency based upon the undetectable serum C7 protein on radial immunodiffusion and the undetectable serum total and C7 hemolytic activities. To identify the genetic basis of the C7 deficiency of the patient, we performed a mutation analysis for the C7 gene and found two novel mutations; a point mutation at the 3' splice acceptor site of intron 4 (c.281-1G>T) and a large deletion mutation encompassing almost the whole C7 gene from exon 1 to exon 17 (c.1-?_2350+?del). A haplotype analysis showed that the large deletion mutation was inherited from the patient's father. To the best of our knowledge, this is the first confirmed case of C7 deficiency in Korea.

Complement component C7 deficiency in two Spanish families

Different genetic mutations have been described in complement component C7 deficiency, a molecular defect clinically associated with an increased susceptibility to neisserial recurrent infections. In this work we report the genetic basis of C7 deficiency in two different Spanish families (family 1 and family 2). In family 1, of Gypsy ethnical background, exon-specific polymerase chain reaction and sequencing revealed a not previously described single base deletion of nucleotide 1309 (exon 10) in the patient, as well as in her father, leading to a stop codon that causes the premature truncation of the C7 protein (K416 X 419). Additionally, the patient and her mother displayed a missense mutation at position 1135 (exon 9) located in the first nucleotide of the codon GGG (CGG), resulting in a change of amino acid (G357R). This mutation was firstly described in individuals of Moroccan Sephardic Jewish ancestry and has been also reported among Spaniards. In family 2, another novel mutation was found in homozygosity in two siblings; a two base-pair deletion of nucleotides 1922 and 1923 in exon 14 leading to the generation of a downstream stop codon causing the truncation of the C7 protein product (S620 X 630). Our results provide more evidence for the heterogeneous molecular basis of C7 deficiency as well as for the subsequent susceptibility to meningococcal disease, since different families carry different molecular defects. On the other hand, certain C7 defects appear to be prevalent in individuals from certain populations or living in defined geographical areas.

Molecular epidemiological analysis of the changing nature of a meningococcal outbreak following a vaccination campaign

A serogroup C meningococcal outbreak that occurred in an Israeli Arab village led to a massive vaccination campaign. During the subsequent 18 months, new cases of type B Neisseria meningitidis infection were revealed. To investigate the influence of vaccination on bacteriological epidemiology, bacteria were isolated from individuals at the outbreak location, patients with several additional other sporadic cases, and patients involved in another outbreak. Haploid bacterial genomic DNA was mixed with a consensus PCR product to form a heteroduplex state that enabled multilocus sequence typing (MLST) to be combined with denaturing high-performance liquid chromatography (DHPLC) for a novel high-throughput molecular typing method called MLST-DHPLC. A 100% correlation was found to exist between the sequencing by MLST alone and the MLST-DHPLC method. Independent molecular typing by repetitive extragenic palindromic PCR discriminated the neisserial clones as well as the MLST-DHPLC method did. The occurrence of type B N. meningitidis in the postvaccination period might be attributed to the selection pressure applied to the bacteria by vaccination, suggesting a possible unwarranted outcome of vaccination with the quadrivalent vaccine for control of a serogroup C meningococcal outbreak. This is the first time that DHPLC has been applied to the genotyping of bacteria, and it proved to be more efficient than MLST alone.

Chitotriosidase deficiency in survivors of Candida sepsis

The existence of chitotriosidase, a human chitinolytic enzyme, hydrolyzes artificial chitotrioside substrates, but its specific function in humans is unknown. The homologous chitinases have an anti-fungal action in plants. In patients with Gaucher disease, chitotriosidase activity is markedly elevated and is a marker for response to specific treatment. In all populations, 6% of individuals are enzyme deficient but completely healthy. It was hypothesized that chitotriosidase deficient persons may be more vulnerable to fungal infections. Thus, the objective of the study was to ascertain the prevalence of homozygosity for the mutation of chitotriosidase among survivors of Candida sepsis. The prevalence of homozygosity among survivors was similar to that in the normal population. Although the cohort is the largest of its kind, since only survivors were tested, further studies should include all patients with Candida sepsis for comparison of survival rates among deficient versus sufficient individuals, and thereby elucidate if this enzyme has an anti-fungal function in man. Several theories are considered to explain the results.