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Polymorphisms in Cytokine Gene do not Affects the Parasite Density in Plasmodium vivax Malaria in a Gold-Mining Area from Amazon Region

Tamirys Pina Simão 1 ; Rafaele Oliveira 2 ; Felipe B. Freitas 3 ; Pedro M. S. Ferreira 4 ; Darci R. Silva 4 ; Rogério G. Brandão 4 ; Shirley F. O. Nascimento 4 ; Sônia M. N. Rodrigues 4 ; Thais Hetierre Abreu Monteiro 5 ; Isabela C. O. Silva 6 ; Luana N. G. C. Lima 7 ; Ana Maria Revoredo Ventura 8 ; Martin J. Enk 7 ; Edivaldo H. C. Oliveira 7 ; Ricardo Luiz Dantas Machado 7
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Background: P. vivax is the most prevalent species in the Brazilian Amazon region. A growing body evidences indicates that the immunity is important in the outcome of P. vivax infection. Single-nucleotide polymorphisms (SNPs) in cytokine genes can alter the production of these proteins and consequently affect the parasite density, which has been recognized as an important factor in the outcome of malaria infection. Materials and Methods: We investigated whether SNPs in cytokine genes are associated with parasite density in 50 malaria patients and 79 healthy individuals from Itaituba, municipality situated on southwest of Pará state. Three SNPs, TNFA -308G/A (rs1800629), INFB +874T/A (rs2430561), IL6 -174G/C (rs1800795) and the haplotype IL10 -1082G/A (rs1800896), -819C/T (rs1800871) and -592C/A (rs1800872), were analyzed by PCR-SSP. The parasite density was determined by counting the number of parasite in 100 separate fields and converted to the number of parasites per microliter of blood assuming 8,000 leucocytes/ µL. The existence of association was determined by Mann-Whitney test, with level of significance of 0.05, using Graph-Pad Prism software, version 6.0. Results: Parasite density levels ranged from 30 to 60,000 parasites/ mm3 (10910.4 ± 14406.25) and all SNPs tested were in Hardy-Weinberg equilibrium. No significant association was found between the SNPs tested and parasite density. Conclusions: Due to the obvious importance of cytokine effects on malaria, studies that elucidate the complex host-parasite interaction may be useful for understood pathophysiology. In the present study, the SNPs in cytokine gene appear to have no effect on the parasite density, since no association was found. The inclusion of a larger number of samples may confirm this assertion and therefore may have been a limitation of the study.