Genetic variation of FcγRIIa induces higher uptake of Leishmania infantum and modulates cytokine production by adherent mononuclear cells in vitro.

Introduction: Single nucleotide variations (SNVs) are specific genetic variations that commonly occur in a population and often do not manifest phenotypically. However, depending on their location and the type of nucleotide exchanged, an SNV can alter or inhibit the function of the gene in which it occurs. Immunoglobulin G (IgG) receptor genes have exhibited several polymorphisms, including rs1801274, which is found in the FcgRIIa gene. The replacement of A with T results in a Histidine (H) to Arginine (R) substitution, altering the affinity of the IgG receptor for IgG subtypes and C-reactive protein (CRP). In this study, we analyzed rs1801274 and its functional implications concerning L. Infantum uptake and cytokine production. Methods: We genotyped 201 individuals from an endemic area for visceral leishmaniasis to assess the presence of rs1801274 using Taqman probes for a candidate gene study. Additionally, we included seventy individuals from a non-endemic area for a functional study. Subsequently, we isolated and cultivated one-week adherent mononuclear cells (AMCs) derived from the peripheral blood of participants residing in the non-endemic region in the presence of L. infantum promastigotes, with and without antigen-specific IgG and/or CRP. We analyzed the rate of phagocytosis and the production of nitric oxide (NO), tumor necrosis factor (TNF)-a, interleukin (IL)-10, IL-12 p70, IL-1b, IL- 6, and IL-8 in the culture supernatants. Results and discussion: In participants from the endemic region, the A/G (H/R isoform) heterozygous genotype was significantly associated with susceptibility to the disease. Furthermore, SNVs induced a change in the phagocytosis rate in an opsonin-dependent manner. Opsonization with IgG increased the production of IL-10, TNF-a, and IL-6 in AMCs with the H/R isoform, followed by a decrease in NO production. The results presented here suggest that the rs1801274 polymorphism is linked to a higher susceptibility to visceral leishmaniasis.

Infection with Leishmania (Leishmania) infantum of 0 to 18-Month-old children living in a visceral leishmaniasis-endemic area in Brazil.

The diagnosis of Leishmania (Leishmania) infantum infection in children from birth may serve as a reference for the early identification of cases that would progress to classical visceral leishmaniasis (VL) in endemic areas. This study prospectively evaluated newborns of mothers living in the municipality of Paracatu, Minas Gerais, Brazil. The infants were followed up at 6-month intervals by clinical examination, serological tests (immunofluorescence [IIF] and enzyme-linked immunosorbent assay with rK39 [ELISA-rK39]) and polymerase chain reaction (PCR) until they had completed 18 months of age. A total of 166 pregnant women were included to evaluate the possible transfer of antibodies or even congenital transmission. Twenty-two of the women tested positive by IIF, four by ELISA-rK39, and one by PCR. Three infants of the 25 women with some positive test results were also positive in the first test (one by IIF, one by ELISA-rK39, and the third by ELISA-rK39 and PCR). One hundred and sixty infants were included in the study; of these, 43 had at least one positive sample over time. However, agreement between tests was low. Follow-up of children with a positive result in the tests studied revealed no progression to classical disease within a period of 18 months. In contrast, two children with negative IIF, PCR, and ELISA-rK39 results developed classical VL at 9 and 12 months of age. In conclusion, a positive test result was variable and sometimes temporary and agreement between tests was low. Therefore, the early diagnosis of Leishmania infection was not associated with the early identification of cases that would progress to classical VL in the endemic area studied.

Association between the lymphotoxin-alpha gene polymorphism and chagasic cardiopathy.

Lymphotoxin-alpha (LT-alpha or LTA) is an inflammatory cytokine that is involved in the organization and maintenance of the inflammatory process and in the arrangement of cells at the site of inflammation. These features suggest an important role in the development of chronic Chagas' disease, especially the cardiac form. The objective of this study was to evaluate LT-alpha genetics and its biological role in chronic Chagas' disease. A total of 284 subjects were studied. The LT-alpha single-nucleotide polymorphism (+252) was analyzed by the polymerase chain reaction-restriction fragment length polymorphism and expression by enzyme-linked immunosorbent assay in culture supernatants and in individual T lymphocytes by flow cytometry. The risk of developing the cardiac form was 2.8 times higher among carriers of genotype GG and 2.4 times among carriers of genotype GA when compared to subjects carrying genotype AA. Seropositive subjects carrying the G allele produced significantly higher levels of LT-alpha. The cytokine was mainly expressed by CD8(+) T lymphocytes in the absence of any stimulus and after stimulation with the Trypanosoma cruzi antigen. This study provides genetic and biological evidence for an important role of LT-alpha in the development of the cardiac form of Chagas' disease.

Genetic and functional role of TNF-alpha in the development Trypanosoma cruzi infection.

TNF-alpha plays an important role in trypanocidal mechanisms and is related to tissue injury. This cytokine has been detected in the heart of human chagasic patients where it is associated with tissue damage. This study investigated whether TNF-alpha levels and the presence of genetic polymorphisms are associated with the presence of T. cruzi infection and/or with the development of the cardiac form in chronic chagasic patients. Genomic DNA of 300 subjects from an endemic area was extracted and analyzed by PCR using specific primers. TNF-alpha was assayed in culture supernatants by ELISA. An association was observed between the absence of the TNF-238A allele and negative serology. Furthermore, seropositive individuals carrying the TNF-238A allele produced significantly higher TNF-alpha levels without stimulation (p=0.04) and after stimulation with LPS (p=0.007) and T. cruzi antigens (p=0.004). The present results suggest that the polymorphism at position -238 influences susceptibility to infection and that this allele is associated with higher TNF-alpha production in seropositive individuals.