The release of reactive oxygen intermediates (ROI) constitutes part of the innate immune responses against pathogens . During malaria, ROI production can contribute to both faster parasite clearance and more severe disease, especially anaemia [2, 3]. Furthermore, ROI are involved in cell signalling pathways . In autoimmune diseases such as Multiple Sclerosis (MS), ROI have been implicated as mediators for demyelination and axonal damage [5, 6], and enhanced respiratory burst activity has been detected in leukocytes of MS patients compared to control individuals .
One of the key enzymes leading to production of ROI is the leukocyte NADPH oxidase, consisting of several subunits, which are membrane-bound or located in the cytosol. Loss-of-function-mutations within the genes of these subunits lead to the development of chronic granulomatous disease (CGD) . Genetic variation in components of the leukocyte NADPH oxidase may, therefore, influence disease susceptibility to and disease course of parasitic infection and autoimmune disease. The length of a TA-repeat in the promoter region of the leukocyte NADPH oxidase subunit gp91phox is associated with severity of malaria . A single nucleotide polymorphism (SNP) in the subunit neutrophil cytosolic factor (NCF) 4 (p40phox) has been shown to be associated with antibody-negative arthritis . Susceptibility to animal models of autoimmune diseases such as collagen-induced arthritis (CIA), experimental autoimmune neuritis (EAN) and experimental autoimmune encephalomyelitis (EAE) is influenced by genetic variation of Ncf1 (p47phox), another NADPH-oxidase subunit [11, 12]. An intrinsic lower ROI release was associated with increased susceptibility to arthritis in rats . Recently it was shown that transgenic expression of ncf1 in macrophages can suppress autoimmune T cell responses in mice .
A mutation in human NCF1 accounts for about 25% of all CGD cases. Unlike the heterogeneous CGD-causing mutations in other leukocyte NADPH oxidase subunits, about 95% of the cases are attributed to a NCF1 mutation carry a common dinucleotide deletion (ΔGT) in exon 2, leading to a frameshift and premature stop codon. This phenomenon is explained by the existence of two pseudogenes of NCF-1 (ΨNCF1), located in the same genomic region on chromosome 7q11.23 . Two types of these pseudogenes have been described: type I ΨNCF1 contains the GT deletion (ΔGT) while the more recently described type II ΨNCF1 does not . It is, therefore, possible that type II ΨNCF1 might be translated into functional protein similar to the NCF1 gene. In healthy individuals (non-CGD, non-carrier) the prevalence of type I and II ΨNCF1 can be determined by the ΔGT/GTGT ratio. Heyworth et al found among 53 healthy individuals 44 with a ratio of 2:1 (reflecting two type I ΨNCF1 genes per NCF1 gene), seven with a ratio of 1:1 (reflecting heterozygosity for a haplotype containing each one type I and type II ΨNCF1) and two with a ratio of 1:2 (possibly reflecting homozygosity for a haplotype containing each one type I and type II ΨNCF1) .
Whether the ΔGT/GTGT ratio has functional significance in terms of individual NCF1 expression, ROI production or susceptibility to infectious or autoimmune diseases is currently unknown. This study evaluates whether NCF1 ΔGT/GTGT ratios are associated with severity of Plasmodium falciparum malaria or individual ROI production in Gabonese children suffering from malaria. In order to search for a possible association with autoimmune diseases, a case-control association study in MS patients from Germany and Poland was conducted.