Toxoplasma gondii protects from IgE sensitization and induces Th1/Th2 immune profile

Toxoplasma gondii (T gondii) infection has been associated with protection against allergy and autoimmune diseases. We investigated the effects of T gondii infection on cytokine and antibody responses in atopic and nonatopic Brazilian subjects. We have measured in whole-blood cultures, Th1 (IFN-γ and IL-12), Th2 (IL-5) and regulatory cytokine IL-10 in blood cells unstimulated and stimulated with pokeweed mitogen or T gondii soluble tachyzoites antigen (STAg) or Dermatophagoides pteronyssinus antigen. A significant negative association was found between high levels of anti-dust mite IgE and T gondii seropositivity (OR = 0.46; 95%CI = 0.25-0.85). STAg stimulation induced a mixed profile of Th1 and Th2 cytokines (IFN-γ, IL-12 and IL-5) in Tg-positive atopic individuals compared with Tg-negative atopic individuals (P < .0001, P = .033 and P = .003, respectively). In contrast, IL-10 production was not different between these groups. No association was found between T gondii infection and asthma. We hypothesized that the protective effect on atopy might be related to the strong Th1 immune response to T gondii found on the seropositive subjects. From our knowledge, this is the first study to investigate the association between atopy and T gondii infection in Brazilian subjects, analysing the cellular immune responses.

Genetic diversity of Toxoplasma gondii isolates obtained from free-living wild birds rescued in Southeastern Brazil

Recent studies carried out in Brazil have shown that strains from the same Toxoplasma gondii genotype can infect humans, domestic animals (dogs and cats) and animals slaughtered for human consumption (pigs, sheep, goats, and chickens), suggesting a common infection route. However, little is known about the importance of free-living wild birds within this epidemiological context. The objective of this work was to isolate, genotype, and evaluate the virulence for mice of new isolates of T. gondii obtained from free-living wild birds from the state of Minas Gerais, Southeastern Brazil. From August 2016 to June 2017, T. gondii was isolated from the hearts and brains collected from 6 out of 45 free-living wild birds, namely, a roadside hawk (Rupornis magnirostris), a campo flicker (Colaptes campestris), a southern caracara (Caracara plancus) and a tropical screech-owl (Megascops choliba), all rescued in Belo Horizonte. One isolate was obtained from a toco toucan (Ramphastos toco), rescued in Cristiano Otoni, and another was obtained from southern caracara, rescued in Santa Luzia. Five different genotypes were identified by PCR-RFLP. A unique genotype was shared in two different isolates obtained from a southern caracara and a toco toucan. This genotype has never been previously described in any other host or place. Three isolates were classified as of intermediary virulence and three isolates as avirulent for mice. The combined analysis of alleles ROP18/ROP5 (a serine/threonine kinase, and a polymorphic pseudokinase, respectively) was effective in determining the virulence of five of all the isolates with the exception of that from R. magnirostris. Atypical isolates of T. gondii obtained from free-living wild birds rescued in the state of Minas Gerais share the same genotypes of strains that infect humans, domestic animals, and animals slaughtered for human consumption.

Association of ROP18 and ROP5 was efficient as a marker of virulence in atypical isolates of Toxoplasma gondii obtained from pigs and goats in Piauí, Brazil

Recent studies indicate that proteins GRA15, ROP5, ROP16, ROP17, and ROP18 of Toxoplasma gondii are involved in the process of interaction, cellular invasion, and immune response of the host. Among these proteins, alleles of the polymorphic ROP18 and ROP5 seem to be directly associated with T. gondii virulence in mice. The purpose of this work was to isolate and genotype T. gondii from pig, goat, and sheep slaughtered for human consumption in the state of Piauí, Northeastern Brazil and relate the variability of genes that express virulence proteins of the parasite to virulence in mice. T. gondii was isolated from 16 pigs and 9 goats. The parasite was not isolated from sheep samples. Eleven different genotypes were identified using PCR-RFLP. A unique genotype not yet described in any other host and or anywhere else was common to three pig isolates. Eighteen isolates (72%) were characterized as avirulent, four (16%) as intermediate virulence and three (12%) as virulent to mice. The combined analysis of ROP18 and ROP5 in the isolates studied in Piauí, showed four different allele associations: 4/3 (virulent strains), 3/3, 3/1, and 2/3 (avirulent strains). The association 2/3 was not previously described in the literature. Our results indicated that GRA15, ROP16, and ROP17 alleles were not associated with T. gondii virulence in mice. Pigs and goats raised and slaughtered for human consumption in the state of Piauí are infected with isolates of T. gondii presenting different genotypes. We concluded that the virulence protein ROP18, analyzed alone or in combination with ROP5, was effective in determining virulence for mice for the new isolates of T. gondii.

Genotyping of Toxoplasma gondii Directly from Human and Animal Biological Samples: From Partial Genotypes to a New Genotype

Genotyping of Toxoplasma gondii is traditionally performed using DNA obtained from tachyzoites after isolation by bioassay in mice. In this study, genotyping of T. gondii was performed by multiplex nested polymerase chain reaction restriction fragment length polymorphism (Mn-PCR-RFLP) in DNA obtained from the lungs of experimentally infected mice, the hearts of naturally infected free-range chickens, and human blood samples of newborns with congenital toxoplasmosis. The efficiency of Mn-PCR varied according to the marker. We obtained complete genotypes of all of the mice lung samples. In chickens, total or partial genotyping was performed on all of the 15 samples. Two complete genotypes were obtained, including one identified for the first time, and another previously described in different hosts including dogs, cats, and humans. In blood from infants, partial genotypes were obtained in 8 of the 12 samples. Mouse bioassay is the most efficient method to obtain DNA from T. gondii , but direct tissue genotyping enhances the likelihood of obtaining molecular information on T. gondii and is an effective tool as a complement to isolation in mice. In this study, we genotyped Toxoplasma gondii directly from human (blood samples of newborns with congenital toxoplasmosis) and free-range chickens (hearts) by Mn-PCR-RFLP. We present partial and complete genotypes and provide technical and scientific information about T. gondii genotyping methods.

Overlapping Toxoplasma gondii genotypes circulating in domestic animals and humans in Southeastern Brazil

Although several Toxoplasma gondii genotyping studies have been performed in Brazil, studies of isolates from animals in the state of Minas Gerais are rare. The objective of this study was to conduct a genotypic characterization of T. gondii isolates obtained from dogs, free-range chickens, and humans in Minas Gerais and to verify whether the T. gondii genotypes circulating in domestic animals correspond to the genotypes detected in humans. Genetic variability was assessed by restricted fragment length polymorphism at 11 loci (SAG1, 5′+3′SAG2, SAG2 alt, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). Twelve different genotypes were identified among the 24 isolates studied, including 8 previously identified genotypes and 4 new genotypes. The genetic relationship of the 24 T. gondii isolates, together with the genotypes previously described from 24 human newborns with congenital toxoplasmosis, revealed a high degree of similarity among the genotypes circulating in humans and animals in Minas Gerais. The most common genotypes among these species were BrII, BrIII, ToxoDB #108, and ToxoDB #206. Restricted fragment length polymorphism at the CS3 locus of these 48 isolates showed that the majority of isolates presented alleles I (50%) or II (27%). Isolates harboring allele III at the CS3 locus presented low virulence for mice, whereas those harboring alleles I or II presented higher virulence. These results confirm the utility of marker CS3 for predicting the virulence of Brazilian isolates of T. gondii in mice. No association was found between the allele type and clinical manifestations of human congenital toxoplasmosis. This is the first report of T. gondii genotyping that verifies the overlapping genotypes of T. gondii from humans and animals in the same geographic region of Brazil. Our results suggest that there is a common source of infection to the species studied, most likely oocysts contaminating the environment.

Immunosuppression with cyclophosphamide favors reinfection with recombinant Toxoplasma gondii strains

The aim of this study was to verify the effect of immunosuppression by cyclophosphamide (Cy) on susceptibility of BALB/c mice subjected to challenge with recombinant strains of Toxoplasma gondii. Animals were prime infected with the D8 (recombinant I/III) or the ME49 (type II) non-virulent strains, weekly immunosuppressed with Cy and challenged with the CH3 or EGS virulent strains (I/III). Parasites recovered from surviving mice were submitted to PCR-RFLP analysis to confirm co-infection. Prime-infection with the D8 strain conferred more protection against challenge with the CH3 and EGS strains when compared with ME49 prime infection. Cy treatment caused significant leukopenia in the infected mice, what probably favors reinfection after challenge. Reinfection was associated with increased levels of IgA. Otherwise, Cy-treated mice presented significantly lower IgA levels after challenge, suggesting involvement of this immunoglobulin on protection against reinfection. In conclusion, BALB/c mice susceptibility to reinfection by T. gondii is related to genetic differences among the strains used for primary and challenge infections. Alteration of the host’s immune integrity by Cy probably compromises the protection previously established by primary infection.

Spontaneous cystogenesis in vitro of a Brazilian strain of Toxoplasma gondii

Conversion of Toxoplasma gondii tachyzoites to the bradyzoite stage and tissue cyst formation in the life cycle of the parasite have crucial roles in the establishment of chronic toxoplasmosis. In this work we investigated the in vitro cystogenesis and behavior of the EGS strain, isolated from human amniotic fluid. We observed that tachyzoites of the EGS strain converted to intracellular cysts spontaneously in LLC-MK2 epithelial cells, HSFS fibroblasts and C6 glial cell lineage. The peak of conversion occurred in the LLC-MK2 cells after 4days of infection, when 72.3±15.9 of the infected cells contained DBA positive cysts. Using specific markers against bradyzoite, tachyzoite and cyst wall components, we confirmed stage conversion and distinguished immature from mature cysts. It was also observed that the deposition of cyst wall components occurred before the total conversion of parasites. Transmission electron microscopy confirmed the fully conversion of parasites presenting the typical characteristics of bradyzoites as the posterior position of the nucleus and the presence of amylopectin granules. A thick cyst wall was also detected. Besides, the scanning microscopy revealed that the intracyst matrix tubules were shorter than those from the parasitophorous vacuole intravacuolar network and were immersed in a granular electron dense material. The EGS strain spontaneously forms high burden of cysts in cell culture without artificial stress conditions, and constitutes a useful tool to study this stage of the T. gondii life cycle.

Susceptibility to re-infection in C57BL/6 mice with recombinant strains of Toxoplasma gondii

This work reports results of re-infection of BALB/c and C57BL/6 mice with different recombinant strains of Toxoplasma gondii. Mice were prime-infected with the non-virulent D8 strain and challenged with virulent strains. PCR-RFLP of cS10-A6 genetic marker of T. gondii demonstrated that BALB/c mice were re-infected with the EGS strain, while C57BL/6 mice were re-infected with the EGS and CH3 strains. Levels of IFN-γ and IL-10 after D8 prime-infection were lower in C57BL/6 than in BALB/c mice. Brain inflammation after D8 prime-infection was more intense in C57BL/6 than in BALB/c mice. It was shown that re-infection depends on mice lineage and genotype of the strain used in the challenge.

Congenital toxoplasmosis from a chronically infected woman with reactivation of retinochoroiditis during pregnancy

OBJECTIVE

To report a rare case of congenital toxoplasmosis from an immunocompetent mother with chronic infection who had reactivation of ocular disease during pregnancy.

DESCRIPTION

The newborn was asymptomatic at birth and identified by neonatal screening (IgM anti-Toxoplasma gondii in dried blood) among other 190 infants with congenital toxoplasmosis during a 7-month period. His mother had had a non-treated episode of reactivation of toxoplasmic retinochoroiditis during pregnancy, with stable IgG titers and negative IgM results. Results of IgM and IgG in the newborn's serum, as well as IgG immunoblotting were positive and active retinochoroidal lesions were detected in his peripheral retina. The neonate was treated with sulfadiazine, pyrimethamine and folinic acid. At 14 months of life, the child remained asymptomatic, with regression of retinochoroidal lesions and persistence of IgG.

COMMENTS

It is possible that systematic neonatal screening in areas with high prevalence of infection may identify these cases.

The role of MHC haplotypes H2d/H2b in mouse resistance/susceptibility to cyst formation is influenced by the lineage of infective Toxoplasma gondii strain

Toxoplasma gondii strains displaying the Type I/III genotype are associated with acquired ocular toxoplasmosis in humans. Here, we used a mice model to characterize some immunological mechanisms involved in host resistance to infection with such strains. We have chosen the Type I/III strains D8, G2 and P-Br, which cause a chronic infection in mice that resembles human toxoplamosis. Mice deficient of molecules MyD88, IFN-gamma, and IL-12 were susceptible to all three parasite strains. This finding indicates the importance of innate mechanisms in controlling infection. On the other hand, MHC haplotype did not influenced resistance/susceptibility; since mice lineages displaying a same genetic background but different MHC haplotypes (H2b or H2d) developed similar mortality and cyst numbers after infection with those strains. In contrast, the C57BL/6 genetic background, and not MHC haplotype, was critical for development of intestinal inflammation caused by any of the studied strains. Finally, regarding effector mechanisms, we observed that B and CD8+ T lymphocytes controlled survival,whereas the inducible nitric oxide synthase influenced cyst numbers in brains of mice infected with Type I/III strains. These findings are relevant to further understanding of the immunologic mechanisms involved in host protection and pathogenesis during infection with T. gondii.

Ocular toxoplasmosis signs in mice embryo

Ocular toxoplasmosis is present in 20% of infected immunocompetent individuals. Toxoplasmosis is the most common cause of posterior uveitis in immunocompetent subjects and congenital toxoplasmosis transmission was the first parasite to be linked to human lesions in the eye. An experimental model for congenital ocular toxoplasmosis was developed in C57BL/6 mice with the purpose to evaluate Toxoplasma induced ocular pathology during fetal life. Toxoplasma gondii, ME-49 strain, was used to infect pregnant females. Histological analysis of pre-natal fetal eyes from infected female mice, did not show parasite infestation, however, alterations were observed in the outer nuclear layer (ONL) and in the inner nuclear layers (INL) of the retina. Edema was also observed, characterized by the increase of interstitial spaces forming lacunae between the ONL and INL cells and a net of vessels associated with an intense inflammatory infiltrate. These histological observations suggest that ocular lesions are not delayed manifestations of toxoplasmosis. The eye was affected in the initial phase of disease, and these alterations were of similar nature as those observed in mice at later stages of infection.

Characterization ofToxoplasma gondiifrom domestic animals from Minas Gerais, Brazil

In an attempt to isolate and characterize Toxoplasma gondii from the State of Minas Gerais, Brazil, musculature samples from 72 pigs, 25 dogs, 28 free-range chickens and 50 chickens produced in industrialized farms were collected. Antibodies to T. gondii have not been detected in pigs, but were found in nine (40.9 %) out of 22 dogs, and in 15 (53.6 %) of 28 free range chickens. T. gondii was not isolated from pigs and industrialized chickens, but from eight dogs and 11 free range chickens. In order to determine T. gondii virulence, female BALB/c mice were inoculated with 10(3), 10(2), 10(1) and 10(0) tachyzoites of the 19 isolates. The strains RH (virulent) and ME49 (non-virulent) were used as references. Isolates were divided into three groups according to the virulence phenotype: five isolates were classified into virulent in mice, one into non-virulent and 13 into intermediate virulent. Nested-PCR of T. gondii SAG2 locus amplified DNA from 21 out of 22 DNA samples directly extracted from heart of free range chickens. These samples were genotyped through a PCR-RFLP assay. Seventeen (80.9 %) were classified into type I; one (4.8 %) into type III and three (14.3 %) into type I or II.

Toxoplasma gondii: in vitro and in vivo activities of the hydroxynaphthoquinone 2-hydroxy-3-(1'-propen-3-phenyl)-1,4-naphthoquinone alone or combined with sulfadiazine

The compound 2-hydroxy-3-(1'-propen-3-phenyl)-1,4-naphthoquinone (PHNQ6) was evaluated for activity against Toxoplasma gondii, alone or combined with sulfadiazine. Treatment with PHNQ6 combined with sulfadiazine protected at least 70 and 90% of mice infected with RH and EGS strains, respectively. Mice were treated with PHNQ6 (50 mg/kg/day) alone or combined with sulfadiazine (40 mg/L) 30 days after infection with P strain. The number of brain cysts was lower in mice treated with PHNQ6 alone or combined with sulfadiazine compared to that in control mice. Degenerated bradyzoites were observed in animals treated with PHNQ6. Infectivity of bradyzoites treated with PHNQ6 alone or combined with sulfadiazine was inhibited after in vitro incubation.

Efficacy of atovaquone and sulfadiazine in the treatment of mice infected withToxoplasma gondiistrains isolated in Brazil

The efficacy of atovaquone and sulfadiazine was examined alone or in combination for the treatment of mice infected with six Brazilian Toxoplasma gondii strains previously genotyped using the PCR-RFLP assays of the SAG2 gene, in addition to RH strain. Swiss mice were infected intraperitoneally with 10(2) tachyzoites from each strain of T. gondii and treated with 6.25, 12.5, 25 and 50 mg/Kg/day of atovaquone or 40, 80, 160 and 320 mg/Kg/day of sulfadiazine. In a second experiment, mice were treated with the association of previously determined doses of each drug. Treatment started 48 hours post-infection, and lasted 10 days. The susceptibility of T. gondii to atovaquone and to sulfadiazine was different according to the parasite strain. It was observed strains that are susceptible to atovaquone, and strains that are resistant to it. Type I strains were more susceptible to the activity of sulfadiazine and more resistant to atovaquone. Yet type III strains were susceptible to atovaquone and to sulfadiazine. Association of atovaquone and sulfadiazine presented a synergic effect in the treatment of mice infected with RH type I strain and an additive effect in the treatment of mice infected with one type I strain and with two type III strains.

A multihousehold study reveals a positive correlation between age, severity of ocular toxoplasmosis, and levels of glycoinositolphospholipid-specific immunoglobulin A

A cross-sectional household study involving 499 individuals was undertaken in an area of Minas Gerais state, Brazil, where infection with Toxoplasma gondii is endemic. Nearly 50% (n=247) of the sample had T. gondii-specific antibodies, even individuals in the 5-9-year-old age group. Approximately 12.5% (n=28) of a random subsample of participants who were positive for T. gondii antibodies had ocular lesions associated with T. gondii infection. The frequency of ocular toxoplasmosis increased significantly with age, with approximately 50% of individuals >60 years of age having lesions. The size of the ocular lesion correlated positively (r=0.85; P=.01) with the serum level of immunoglobulin A specific for tachyzoite-derived glycoinositolphospholipids. We found that sharing the same residence accounted for 30% of the variation in infectivity among residents in the sample, whereas age was the main risk factor for development of ocular toxoplasmosis in patients who were positive for T. gondii antibodies.

Role of cytokines and major histocompatibility complex restriction in mouse resistance to infection with a natural recombinant strain (type I-III) of Toxoplasma gondii

Herein we characterized various genetic markers and the biological behavior of a natural recombinant strain of Toxoplasma gondii (P-Br). From nine genetic markers analyzed, three (B1, ROP1, and SAG1) and three (cS10-A6, GRA6, and SAG3) markers belong to parasites from the type I and type III lineages, respectively. The SAG2 and L363 loci were shown to be type I-III chimera alleles. The cB2l-4 microsatellite marker showed a unique haplotype. The P-Br strain presented low virulence in the acute phase of infection and was cystogenic during the chronic infection. The interleukin 12/gamma interferon axis and inducible nitric oxide synthase were main determinants of resistance during the acute infection with the P-Br strain. As opposed to infection with the type II strain of T. gondii (ME-49), peroral infection with the P-Br strain led only to a light inflammatory infiltrate and no major lesions in the intestine of the C57BL/6 mice. In addition, the BALB/c (resistant to ME-49) and C57BL/6 (susceptible to ME-49) mice were shown, respectively, to be more susceptible and more resistant to cyst formation and toxoplasmic encephalitis when infected with the P-Br strain. Further, the C57BL/KsJ and DBA2/J congenic strains containing major histocompatibility complex (MHC) haplotype "d" were more resistant than the parental strains (C57BL/6 and DBA1/J), when infected with the ME-49 but not with the P-Br strain. Together, our results indicate that resistance to cyst formation and toxoplasmic encephalitis induced during infection with P-Br is not primarily controlled by the MHC haplotype d, as previously reported for type II strains of T. gondii.

Biological and molecular characterization of Besnoitia akodoni n.sp. (Protozoa: Apicomplexa) from the rodent Akodon montensis in Brazil

The diversity among coccidian parasites of the genus Besnoitia is incompletely known. Of the eight currently described members of the genus, only B. jellisoni is known to parasitize a rodent host. Here, we propose a new name, Besnoitia akodoni, for the species initially isolated form the rodent Akodon montensis in Brazil. The tissue cysts of B. akodoni were up to 442 microm in diameter and bradyzoites were 8.4 x 1.4 microm in size. The bradyzoites contained enigmatic bodies, micronemes and rhoptries. Tachyzoites were 5.8 x 1.5 microm in size and they could be grown in vitro in bovine monocytes and African Green monkey cells where they divided by endodyogeny. Besnoitia akodoni was infective to laboratory-raised mice (Mus musculus) and gerbils (Meriones unguiculatus) but not to cats (Felis catus). Comparison of the conserved sequences of the small subunit rDNA clearly established the close relationship of B. akodoni with other members of the genus. However, sequences of the more variable first internal transcribed spacer portion of the ribosomal DNA repeat support its differentiation from the other species of the genus.

Activity of natural and synthetic naphthoquinones against Toxoplasma gondii, in vitro and in murine models of infection

The effect of 14 natural and synthetic naphthoquinones in the replication of Toxoplasma gondii was evaluated. In vitro studies were accomplished in cultures of 2C4 fibroblasts infected with RH-strain. Enzyme-linked immunosorbent assay was used to quantify parasite growth. For the studies in vivo, mice were infected with tachyzoites of the RH strain or cysts of the T. gondii EGS strain. In vitro, seven naphthoquinones demonstrated significant inhibition of intracellular T. gondii growth at concentrations of 1 and 5 micrograms/ml. Only three compounds were significantly protective when tested in animals: 2-hydroxy-3'-(3'-pentenyl)-1,4-naphthoquinone (PHNQ4), 2-hydroxy-3-(1'-vinylphenyl)-1,4-naphthoquinone (PHNQ5), and 2-hydroxy-3-(1'-propen-3'-phenyl)-1,4-naphthoquinone (PHNQ6). In animals infected with the EGS strain and treated with PHNQ4 (50 mg/kg/day orally), a 7-day prolongation of the time to death was observed. Treatment with 100 mg/kg/day orally or 50 mg/kg/day i.p. of PHNQ5 resulted in a 5-day and 16-day prolongation of the time to death, respectively. Treatment with 50 mg/kg/day orally or 50 mg/kg/day i.p. of PHNQ6 resulted in a 4-day prolongation of the time to death or up to 30 days after treatment, respectively. Our results suggest that the naphthoquinones may be important therapeutic agents for the treatment of toxoplasmosis.

Western blot analysis of the humoral response of dogs experimentally infected with Angiostrongylus vasorum (Baillet, 1866)

Seven cross-bred dogs were inoculated with Angiostrongylus vasorum and serum samples were analyzed using the enzyme-linked immunosorbent assay (ELISA) and Western blot (WB). ELISA detected specific antibodies anti-A. vasorum, from 14 to 28 days after inoculation (DAI) and persisted throughout the experiment. Using WB, the main antigens detected had molecular weight of approximately 115, 102, 86, 76, 69, 56, 41, 32, 28, 20-22 and 10kDa.

Avaliação parasitológica e sorológica de caprinos inoculados experimentalmente pelo Trypanosoma cruzi

A infecção experimental pelo Trypanosoma cruzi foi estudada em nove caprinos jovens. Os animais foram inoculados via intraperitoneal com 10³ tripomastigotas sangüíneos/Kg de peso com as cepas 147 (Grupo 1) e 229 (Grupo 2), isoladas de pacientes chagásicos crônicos de Bambuí, MG. Realizaram-se exames de sangue a fresco, xenodiagnóstico, hemocultura e sorologia (RIFI e ELISA). O período de acompanhamento da infecção variou de 7 a 30 meses. Pôde-se observar uma acentuada diferença no curso da infecção entre os dois grupos. Demonstrou-se pela primeira vez em caprinos experimentalmente inoculados com T. cruzi, o parasita através de exames de sangue a fresco e xenodiagnóstico no período agudo e pela hemocultura e xenodiagnóstico no período crônico da infecção chagásica. Os resultados sugerem que caprinos, em determinadas condições epidemiológicas, podem ser importantes no ciclo de transmissão silvestre e peridoméstico do T. cruzi, especialmente aqueles animais mais jovens.