Polymorphisms in the RNASE3 Gene Are Associated with Susceptibility to Cerebral Malaria in Ghanaian Children

Abstract

BackgroundCerebral malaria (CM) is the most severe outcome of Plasmodium falciparum infection and a major cause of death in children from 2 to 4 years of age. A hospital based study in Ghana showed that P. falciparum induces eosinophilia and found a significantly higher serum level of eosinophil cationic protein (ECP) in CM patients than in uncomplicated malaria (UM) and severe malaria anemia (SA) patients. Single nucleotide polymorphisms (SNPs) have been described in the ECP encoding-gene (RNASE3) of which the c.371G>C polymorphism (rs2073342) results in an arginine to threonine amino acid substitution p.R124T in the polypeptide and abolishes the cytotoxicity of ECP. The present study aimed to investigate the potential association between polymorphisms in RNASE3 and CM.Methodology/Principal FindingsThe RNASE3 gene and flanking regions were sequenced in 206 Ghanaian children enrolled in a hospital based malaria study. An association study was carried out to assess the significance of five SNPs in CM (n = 45) and SA (n = 56) cases, respectively. The two severe case groups (CM and SA) were compared with the non-severe control group comprising children suffering from UM (n = 105). The 371G allele was significantly associated with CM (p = 0.00945, OR = 2.29, 95% CI = 1.22–4.32) but not with SA. Linkage disequilibrium analysis demonstrated significant linkage between three SNPs and the haplotype combination 371G/*16G/*94A was strongly associated with susceptibility to CM (p = 0.000913, OR = 4.14, 95% CI = 1.79–9.56), thus, defining a risk haplotype. The RNASE3 371GG genotype was found to be under frequency-dependent selection.Conclusions/SignificanceThe 371G allele of RNASE3 is associated with susceptibility to CM and forms part of a risk associated haplotype GGA defined by the markers: rs2073342 (G-allele), rs2233860 (G-allele) and rs8019343 (A-allele) respectively. Collectively, these results suggest a hitherto unrecognized role for eosinophils in CM pathogenesis.

Structural determinants of the eosinophil cationic protein antimicrobial activity

“…A severe pathology is attributed to the protein neurotoxicity, which causes cerebral malaria, a major cause of children ' s death at an early stage. The natural variant (Arg97Thr), which reduces the protein cytotoxicity ), seems to have been selected in the Ghana population exposed to malaria infection, as a mechanism to avoid the protein severe neurotoxic side effects (Adu et al , 2011 ). A similar scenario was reported for Schistosoma infection, a common helminth parasite in tropical areas.…”

“…In fact, the proteolytic processing is used extensively in immunology cascade events. A local cleavage can release the active peptides in the infection area in the same manner as cecropin is released from cathelicidins expressed in neutrophils (Zanetti et al , 1995 ;Burton and Steel , 2009 ), lactoferricin is derived from the N-terminus (Krieg et al , 1998 ;Clark et al , 2003 ); Tyr33 nitration (Ulrich et al , 2008 ) Host defense against viral infections; chemotaxis for dendritic cells (Rosenberg , 2008a ) RNase 3 (tested against several Gram-negative and -positive species (Torrent et al , 2009b(Torrent et al , , 2011b Arg97/Thr (related to asthma propensity and disease-induced pathologies) (Eriksson et al, 2007a;Adu et al , 2011 ) Gly103Arg 3 potential N-glycosylation sites; 10 purifi ed variants of N-linked glycosylated forms (Eriksson et al , 2007b ); N-glycosylation processed upon secretion by activated eosinophils (Woschnagg et al , 2009 );…”

Haplotype of RNASE 3 polymorphisms is associated with severe malaria in an Indian population

“…In addition, another study demonstrated that ECP can suppress the growth of Pf in in vitro [ 22 ]. Above findings led to several genetic studies of the RNASE 3 gene in African populations [ 19 , 20 ], which all showed an association between RNASE 3 polymorphisms (+ 371C > G and + 499G > C) and SM [ 19 , 20 ], further confirming its role in severity of the disease. The minor allele frequencies of + 371C > G and + 499G > C polymorphisms were more than 0.20 in African populations [ 19 , 20 ].…”

“…Similarly, among host genes, polymorphisms in intercellular adhesion molecule 1 (ICAM-1), cluster of differentiation 36 (CD36), tumor necrosis factor-alpha (TNF-α), Interferon-gamma (IFN-γ), interleukin-1β, complement receptor-1 (CR-1), ATP binding cassette subfamily B member 1 (ABCB1) and adenosine A2a receptor (ADORA2A) have linked to the development of SM [ 9 – 16 ]. Ribonuclease 3 ( RNASE 3 ), which encodes eosinophil cationic protein (ECP), an important protein produced by eosinophils during inflammation and infection [ 17 , 18 ], was found to increase susceptibility to SM [ 19 – 22 ]. Indeed, SM patients had higher ECP levels and hypereosinophilia compared to UM patients [ 21 ].…”

Eosinophil Cationic Protein: Overview of Biological and Genetic Features

“…Furthermore, an in vitro study has demonstrated that ECP could inhibit P. falciparum growth in a dose-dependent manner (Waters et al, 1987). Based on the evidence that ECP might be important in the control of P. falciparum infection, but may also play a role in CM pathogenesis, Adu et al (2011) investigated the association between polymorphisms in RNASE3 and susceptibility to CM in a hospital-based malaria study involving CM, SA, and UM patients. During the analysis of the c.371G.C polymorphism [rs2073342; 434(G > C)], results showed that the 371G allele was associated with susceptibility to CM and forms part of a risk-associated haplotype GGA defined by the markers: rs2073342 (G-allele), rs2233860 (G-allele), and rs8019343 (Aallele), respectively.…”