IL4 gene polymorphism and previous malaria experiences manipulate anti-Plasmodium falciparum antibody isotype profiles in complicated and uncomplicated malaria.

BACKGROUND: The IL4-590 gene polymorphism has been shown to be associated with elevated levels of anti-Plasmodium falciparum IgG antibodies and parasite intensity in the malaria protected Fulani of West Africa. This study aimed to investigate the possible impact of IL4-590C/T polymorphism on anti-P. falciparum IgG subclasses and IgE antibodies levels and the alteration of malaria severity in complicated and uncomplicated malaria patients with or without previous malaria experiences. METHODS: Anti-P.falciparum IgG subclasses and IgE antibodies in plasma of complicated and uncomplicated malaria patients with or without previous malaria experiences were analysed using ELISA. IL4-590 polymorphisms were genotyped using RFLP-PCR. Statistical analyses of the IgG subclass levels were done by Oneway ANOVA. Genotype differences were tested by Chi-squared test. RESULTS: The IL4-590T allele was significantly associated with anti-P. falciparum IgG3 antibody levels in patients with complicated (P = 0.031), but not with uncomplicated malaria (P = 0.622). Complicated malaria patients with previous malaria experiences carrying IL4-590TT genotype had significantly lower levels of anti-P. falciparum IgG3 (P = 0.0156), while uncomplicated malaria patients with previous malaria experiences carrying the same genotype had significantly higher levels (P = 0.0206) compared to their IL4-590 counterparts. The different anti-P. falciparum IgG1 and IgG3 levels among IL4 genotypes were observed. Complicated malaria patients with previous malaria experiences tended to have lower IgG3 levels in individuals carrying TT when compared to CT genotypes (P = 0.075). In contrast, complicated malaria patients without previous malaria experiences carrying CC genotype had significantly higher anti-P. falciparum IgG1 than those carrying either CT or TT genotypes (P = 0.004, P = 0.002, respectively). CONCLUSION: The results suggest that IL4-590C or T alleles participated differently in the regulation of anti-malarial antibody isotype profiles in primary and secondary malaria infection and, therefore, could play an important role in alteration of malaria severity.

Associations between the IL-4 -590 T allele and Plasmodium falciparum infection prevalence in asymptomatic Fulani of Mali.

In this study, we compared the genotype and allele frequencies of the IL-10 -1087 A/G and IL-4 -590 C/T single nucleotide polymorphisms in asymptomatic subjects of two sympatric ethnic tribes differing in susceptibility to malaria, the Fulani and the Dogon in Mali. The genotype data was correlated with ethnicity and malariometric indexes. A statistically significant inter-ethnic difference in allele and genotype frequency for both loci was noted (P<0.0001). Within the Fulani, the prevalence of Plasmodium falciparum infection, as detected by both microscopy and PCR, was associated with the IL-4 -590 T allele (P=0.005 and P=0.0005, respectively), whereas, no such associations were seen in the Dogon. Inter-ethnic differences in spleen rates, higher in the Fulani than the Dogon, were seen between T carriers (TT and CT) of both groups (P<0.0001). Parasite densities and number of concurrent clones did not vary between IL-4 genotypes within any of the studied groups. These results suggest an association between the IL-4 -590 T allele and P. falciparum prevalence within the Fulani but not the Dogon. No associations between IL-10 genotypes and studied malariometric indexes were observed in any of the two communities.

Relative levels of IL4 and IFN-gamma in complicated malaria: association with IL4 polymorphism and peripheral parasitemia.

Functional IL4-590 C/T polymorphisms and the relative amounts of IL4 and IFN-gamma were investigated in relation to severity of malaria in 110 and 169 Thai patients with complicated and uncomplicated malaria, respectively. The plasma IL4 and IFN-gamma levels were determined by ELISA and the IL4-590 C/T polymorphisms were genotyped. The IFN-gamma levels were significantly elevated in patients with complicated malaria in the initial stage of the disease before treatment compared to the levels found with uncomplicated malaria (231pg/ml versus 150pg/ml, p=0.0029), while the IL4 levels were significantly elevated 7 days after treatment (167pg/ml versus 81pg/ml, p=0.0003). Our study did not reveal any association between the IL4-590 C/T transition and the severity of malaria. However, a significant difference in the IL4 to IFN-gamma ratio between patients with complicated and uncomplicated malaria was observed only in patients with IL4-590 T allele homozygosity (geometric mean: 0.321 versus 0.613, p=0.0087 for TT allele). A significant inverse correlation between IL4 to IFN-gamma ratio and peripheral parasitemia was observed only in complicated malaria patients carrying TT genotype (r=-0.283, p=0.046). These results suggest that the IL4-590 C/T polymorphism may play a role in the balance between IL4 and IFN-gamma, as well as in the control of parasitemia, which in turn may alter the severity of malaria.

Different antibody- and cytokine-mediated responses to Plasmodium falciparum parasite in two sympatric ethnic tribes living in Mali.

The Fulani are known to be less susceptible to Plasmodium falciparum malaria infections and to have lower parasitaemia despite living under similar malaria transmission intensity compared with other ethnic tribes. The aim of the present study was to examine whether the Fulani were more polarised towards Th2 as reflected by higher numbers of malaria-specific IL-4- and IL-10-producing cells and lower numbers of IFN-gamma- and IL-12-producing cells as compared to their neighbour ethnic tribe, the Dogon of Mali. Total IgE and both anti-malaria IgE and IgG antibodies were measured by ELISA and the numbers of IL-4-, IFN-gamma-, IL-10- and IL-12-producing cells were enumerated using enzyme-linked ImmunoSpot assay (ELISPOT). Numbers of parasite clones were detected by polymerase chain reaction (PCR). The study was performed outside the transmission period and all individuals included were asymptomatic. The results revealed that the Fulani were less parasitised, had fewer circulating parasite clones in their blood, had significantly higher anti-malaria IgG and IgE antibodies and higher proportions of malaria-specific IL-4- and IFN-gamma-producing cells compared to the Dogon. The higher antigen-specific production of IL-4 among the Fulani was statistically significant both before and after adjustment for level of spontaneous cytokine production, while greater IFN-gamma production only attained statistical significance after adjustment for spontaneous levels. Taken together, the association of higher anti-malarial IgE and IgG antibodies and increased numbers of specific IL-4- and IFN-gamma-producing cells compared to the ethnic sympatric tribe, the Dogon, may assist in explaining the lower susceptibility to malaria observed in the Fulani.

A potential role of interleukin 18 in severe falciparum malaria.

Interleukin-18 (IL-18) is a potent proinflammatory cytokine that induces interferon-gamma (IFN-gamma) production from Th1 cells, NK cells and activated macrophages, particularly in the presence of IL-12. However, it is also shown that without help from IL-12, IL-18 is capable of inducing IL-4 and IL-13 production in T cells, NK cells, mast cells and basophils, and that administration of IL-18 in conjunction with an allergen increases serum IgE levels. In order to clarify the role of IL-18 in disease severity of falciparum malaria, we have examined serum levels of IL-18, IFN-gamma, and IgE for 96 patients with falciparum malaria [Trans. R. Soc. Trop. Med. Hyg. 97, 236-241]. Results suggested that IL-18 plays a key role in inducing severe malaria through a pathway of elevating IFN-gamma, rather than its IgE inducing activity. Based on these results, the role of IL-18 in severe falciparum malaria will be discussed in this review.

Involvement of interleukin-18 in severe Plasmodium falciparum malaria.

Serum levels of interleukin-18 (IL-18), interferon-gamma (IFN-gamma), and immunoglobulin E (IgE) were determined for 96 patients with Plasmodium falciparum malaria admitted to hospital, Bangkok, Thailand in the period 1998-2000. The patients were divided into 3 groups, i.e. uncomplicated, severe and cerebral malaria according to WHO criteria (2000). Elevation of IL-18 levels was observed in all 3 groups, with a tendency for higher levels in cases with severe malaria throughout the course of the disease. Moreover, there was a significant correlation between IL-18 levels and the extent of parasitaemia among patients with severe malaria. However, IL-18 levels decreased more significantly in patients with cerebral malaria compared with the other groups in the late stage of the disease. Elevated levels of IFN-gamma were also observed in all groups of patients, especially in those with severe or cerebral malaria, and the levels in patients with cerebral malaria remained significantly higher than in those with uncomplicated malaria during days 4-7 post-treatment, suggesting the involvement of IFN-gamma in disease severity. Meanwhile, no significant difference was observed in IgE levels between the severe and uncomplicated groups of patients with helminth infection, although IgE levels were significantly higher in helminth-infected patients than uninfected patients. These results suggest that IL-18 plays a key role in inducing severe malaria through another pathway, such as elevation of IFN-gamma, rather than its IgE inducing activity.

Cytokine and chemokine responses in a cerebral malaria-susceptible or -resistant strain of mice to Plasmodium berghei ANKA infection: early chemokine expression in the brain.

A comparative study was carried out on cytokine and chemokine responses in a cerebral malaria (CM)-susceptible or -resistant strain of mice (C57BL/6 or BALB/c respectively) in Plasmodium berghei ANKA infection. C57BL/6 mice died by 10 days after infection when parasitemia was approximately 15-20% with cerebral symptoms, while BALB/c mice survived until week 3 after infection. Although both strains showed T(h)1-skewed responses on day 4 after infection, significantly higher levels of IFN-gamma, tumor necrosis factor (TNF)-alpha and NO were observed during the course of the infection in BALB/c, suggesting that T(h)1 responses are involved in the resistance. Interestingly, in the brain, both strains expressed IFN-inducible protein of 10 kDa (IP-10) and monocyte chemotactic protein (MCP)-1 genes as early as at 24 h post-infection, whereas some differences were observed between both strains thereafter, i.e. enhanced expression of RANTES in C57BL/6, and of IFN-gamma and TNF-alpha in BALB/c respectively. Moreover, the expression of IP-10 and MCP-1 genes in KT-5, an astrocyte cell line, was induced in vitro upon stimulation with a crude antigen of malaria parasites. These results suggest that the direct involvement of brain parenchymal cells takes place in response to plasmodial infection, providing a new aspect to analyze possible mechanisms of CM. This is the first report on the chemokine expression in neuroglial cells in response to malaria infection.