title: Regulatory monocytes in helminth infections: insights from the modulation during human hookworm infection.
abstract: While the macrophage polarization is well characterized in helminth infections, the natural heterogeneity of monocytes with multiple cell phenotypes might influence the outcome of neglected diseases, such hookworm infection. Here, we report the profile of monocytes in human hookworm infections as a model to study the regulatory subpopulation of monocytes in helminth infections.
  
  
  
  Blood samples were collected from 19 Necator americanus-infected individuals and 13 healthy individuals. Peripheral blood mononuclear cells (PBMCs) were isolated, and immunophenotyping was conducted by flow cytometry. The expressions of genes encoding human nitric oxide synthase (iNOS), interleukin 4 (IL-4), arginase-1 (Arg-1) and glyceraldehyde 3-phosphate dehydrogenase were quantified by qPCR. Plasma levels of IL-4 were determined by sandwich ELISA. Unpaired t-tests or Mann-Whitney tests were used depending on the data distribution.
  
  
  
  Hookworm infected individuals (HWI) showed a significant increase in the number of monocytes/mm3(555.2 ± 191.0) compared to that of the non-infected (NI) individuals (120.4 ± 44.7) (p < 0.0001). While the frequencies of CD14+IL-10+and CD14+IL-12+cells were significantly reduced in the HWI compared to NI group (p = 0.0289 and p < 0.0001, respectively), the ratio between IL-10/IL-12 producing monocytes was significantly elevated in HWI (p = 0.0004), indicating the potential regulatory activity of these cells. Measurement of IL-4 levels and gene expression of IL-4 and Arg-1 (highly expressed in alternatively activated macrophages) revealed no significant differences between the NI and HWI groups. Interestingly, individuals from the HWI group had higher expression of the iNOS gene (associated with a regulatory profile) (20.27 ± 2.97) compared to the NI group (11.28 ± 1.18, p = 0.0409). Finally, individuals from the HWI group had a significantly higher frequency of CD206+CD23+IL-10+(7.57 ± 1.96) cells compared to individuals from the NI group (0.35 ± 0.09) (p < 0.001), suggesting that activated monocytes are a potential source of regulatory cytokines during hookworm infection.
  
  
  
  Natural hookworm infection induces a high frequency of circulating monocytes that present a regulatory profile and promote the downmodulation of the proinflammatory response, which may contribute to prolonged survival of the parasite in the host.
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Lívia Silva Araújo
authors.initials: LS
authors.lastname: Passos
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Pedro Henrique
authors.initials: PH
authors.lastname: Gazzinelli-Guimarães
authors.affiliation: Departament off Biochemistry and Cell Biology, Universidade Federal de Viçosa (UFV), Viçosa, Brazil.
authors.forename: Tiago Antônio de
authors.initials: TA
authors.lastname: Oliveira Mendes
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Ana Clara Gazzinelli
authors.initials: AC
authors.lastname: Guimarães
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Denise da
authors.initials: DD
authors.lastname: Silveira Lemos
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Natasha Delaqua
authors.initials: ND
authors.lastname: Ricci
authors.affiliation: Department of General Pathology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Gonçalves
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Daniella Castanheira
authors.initials: DC
authors.lastname: Bartholomeu
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Ricardo Toshio
authors.initials: RT
authors.lastname: Fujiwara
authors.affiliation: Department of Parasitology, Laboratory of Immunology and Genomics of Parasites, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil. llbueno@icb.ufmg.br.
authors.forename: Lilian Lacerda
authors.initials: LL
authors.lastname: Bueno
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D001119:Arginase / Q000235:genetics; D016207:Cytokines / Q000378:metabolism; D005260:Female; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D006725:Hookworm Infections / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D016753:Interleukin-10 / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D010446:Peptide Fragments / Q000235:genetics
chemical_list: D016207:Cytokines; C508609:IL10 protein, human; C508598:IL4 protein, human; D010446:Peptide Fragments; D016753:Interleukin-10; C068142:glyceraldehyde 3-phosphate dehydrogenase (304-313); D018664:Interleukin-12; D015847:Interleukin-4; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; C574619:ARG1 protein, human; D001119:Arginase