High heterogeneity, mixed infections and new genotypes in human congenital toxoplasmosis cases in the mega-metropolis of Central Mexico

Genotyping of Toxoplasma gondii in domestic animals from Campeche, México, reveals virulent genotypes and a recombinant ROP5 allele

Toxoplasma gondii has at least 318 genotypes distributed worldwide, and tropical regions usually have greater genetic diversity. Campeche is a state located in the southeastern region of México and has favourable climate conditions for the replication and dissemination of this protozoan, similar to those in South American countries where broad genetic diversity has been described. Thus, in this study, 4 T. gondii isolates were obtained from tissues of stray dogs and free-range chickens in Campeche, México, and were genotyped by Mn-PCR-RFLP with 10 typing markers (SAG1, altSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico) and 5 virulence markers (CS3, ROP16, ROP17, ROP18 and ROP5) to provide new information about the distribution and virulence prediction of T. gondii genotypes. Two isolates of T. gondii genotype #116 and 2 of genotype #38 were obtained from stray dogs and chickens, respectively. The parasite load found in these species was between <50 and more than 35 000 tachyzoites per mg of tissue. Virulence marker genotyping revealed a recombinant 1&3 ROP5 RFLP pattern in 2 ToxoDB #116 isolates with no prediction of virulence in a murine model, while in the 2 ToxoDB #38 isolates, the ROP18/ROP5 combination predicted high virulence. Considering all the typed markers, there is a predominance of type I and III alleles, as constantly reported for the isolates characterized in various regions of México. It is crucial to determine their phenotype to corroborate the genetic virulence profile of the T. gondii isolates obtained in this study.

Genotyping of toxoplasma gondii isolates from México reveals non-archetypal and potentially virulent strains for mice

Genotyping and virulence studies of Toxoplasma gondii are essential to investigate the pathogenesis of strains circulating worldwide. In this study, eight T. gondii isolates obtained from a congenitally infected newborn, a calf, two cats, three dogs, and a wallaby from five states of México were genotyped by Mn-PCR-RFLP with 11 typing markers (SAG1, SAG2 5'3', alt. SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico), five virulence markers (CS3, ROP16, ROP17, ROP18 and ROP5), 15 microsatellite markers (TUB-2, W35, TgM-A, B18, B17, M33, IV.1, XI.1, M48, M102, N60, N82, AA, N61, N83), and sequencing. A phylogenetic network was built to determine the relationship between Mexican isolates and those reported worldwide. Six different genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), ToxoDB #8, #10, #28 (n = 3), #48, #116, and #282. Genotyping by microsatellite analysis differentiated the three PCR-RFLP genotype #28 isolates into two strains, revealing a total of seven microsatellite genotypes. Three different allele combinations of ROP18/ROP5 virulence markers were also found, 3/3, 1/1, and 4/1. The last two combinations are predicted to be highly virulent in the murine model. According to the phylogenetic network, the T. gondii strains studied here are related to archetypal strains I and III, but none are related to the strains previously reported in México. The genotypes identified in this study in different species of animals demonstrate the great genetic diversity of T. gondii in México. The ToxoDB-PCR-RFLP #28 genotype was found in three isolates from different hosts and states. Additionally, four of the isolates are predicted to be highly virulent in mice. The next step will be to perform in vitro and in vivo assays to determine the phenotype of these T. gondii isolates in murine models.

Maternal anti-Toxoplasma gondii antibodies IgG2, IgG3 and IgG1 are markers of vertical transmission and clinical evolution of toxoplasmosis in the offspring

Toxoplasma gondii can be transmitted vertically during pregnancy and may cause neurological, ocular, and even systemic damage to the offspring. Congenital toxoplasmosis (CT) can be diagnosed during gestation and/or after birth in the postnatal period. The timely diagnosis is highly relevant for efficient clinical management. The most common laboratory methods for diagnosing CT are based on Toxoplasma-specific humoral immune responses. However, these methods are of low sensitivity or specificity. In a previous study with a small number of cases, the comparison of anti-T. gondii IgG subclasses between mothers and their offspring showed promising results for CT diagnosis and prognosis. Thus, in this work, we analyzed specific IgG subclasses and IgA in 40 T. gondii-infected mothers and their children, of which 27 were congenitally infected and 13 uninfected. A higher frequency of anti-Toxoplasma IgG2, IgG3, IgG4, and IgA antibodies was observed in mothers and congenitally infected offspring. Of these, IgG2 or IgG3 were statistically the most conspicuous. In the CT group, maternal IgG3 antibodies were significantly associated with severe disease of the infants and IgG1 and IgG3 with disseminated disease. The results support that maternal anti-T. gondii IgG3, IgG2 and IgG1 are markers of congenital transmission and severity/spread of disease in the offspring.

Anti-Toxoplasma gondii IgM Long Persistence: What Are the Underlying Mechanisms?

Diagnosis of Toxoplasma gondii acute infection was first attempted by detection of specific IgM antibodies, as for other infectious diseases. However, it was noted that this immunoglobulin declines slowly and may last for months or even years. Apart from the diagnostic problem imposed on clinical management, this phenomenon called our attention due to the underlying phenomena that may be causing it. We performed a systematic comparison of reports studying IgM antibody kinetics, and the data from the papers were used to construct comparative plots and other graph types. It became clear that this phenomenon is quite generalized, and it may also occur in animals. Moreover, this is not a technical issue, although some tests make more evident the prolonged IgM decay than others. We further investigated biological reasons for its occurrence, i.e., infection dynamics (micro-reactivation–encystment, reinfection and reactivation), parasite strain relevance, as well as host innate, natural B cell responses and Ig class-switch problems inflicted by the parasite. The outcomes of these inquiries are presented and discussed herein.

Can cloning and sequencing help to genotype positive Toxoplasma gondii clinical samples? Results and validation using SAG3 as a model

Genotyping of T. gondii in human cases is relevant to understand the transmission patterns and epidemiology of this parasitosis. However, this genetic characterization can be hampered by the difficulty of isolating the parasite from mild or asymptomatic cases and by the detection efficiency of molecular assays such as the multilocus nested-polymerase chain reaction-restriction fragment length polymorphism (Mn-PCR-RLFP). To propose an alternative for the genotyping of positive clinical samples of T. gondii with a low amount of the parasite DNA mixed within the host DNA or mixed infections, we carried out this study to validate the sequences of the SAG3 gene of T. gondii obtained after two rounds of amplification cloned into a bacterial model, thereby achieving the separation and identification of more than one genotype of T. gondii. Also, the detection limit of the parasite DNA and the fidelity of the reagents used in the nested PCR-RFLP in artificial clinical samples by sequencing were determined. T. gondii DNA was detected from 6.25 ng of DNA and 200 parasites/mL of blood. The fidelity of the AmpliTaq Gold™ polymerase after 65 cycles of amplification was 100%. Denaturation of the products obtained after two rounds of nested PCR amplification showed no evidence of chimera or artifact production. The cloning efficiency was 97.5% (39/40 clones), and none of the experiments produced recombinant sequences. Thus, the generation of chimeras with this methodology could be ruled out. Genotyping of clinical samples is important because there is no strain selection bias, as can occur in the bioassay (where more virulent strains can be selected over nonvirulent strains), and therefore, mixed infections can be detected through cloning and sequencing. Furthermore, these two techniques could be useful tools to genotype weak amplicons of any T. gondii gene obtained during nested PCR.

SAG3 Toxoplasma gondii cloning reveals unexpected fivefold infection in the blood of feral cats in the Mexican Caribbean

Background

Currently, more than 300 genotypes of Toxoplasma gondii (T. gondii) have been described throughout the world, demonstrating its wide genetic diversity. The SAG3 locus is one of the genes included in the genotyping panel of this parasite. It is associated with its virulence since it participates during the invasion process of the host cells. Therefore, cloning, sequencing, and bioinformatic analysis were used to deepen the understanding of the SAG3 locus genetic diversity of T. gondii in blood samples from feral cats.

Results

Six different SAG3 sequences were detected, five of which were detected in one feline. Three sequences were first reported here; one of them was an intragenic recombinant. In the cladogram, four out of ten SAG3 sequences did not share nodes with others reported worldwide.

Conclusions

Cloning and sequencing of samples with more than one restriction pattern by PCR-RFLP were very helpful tools to demonstrate the presence of more than three genotypes of T. gondii in the blood of feral cats from southeastern Mexico. This suggests a potential mixed infection of multiple T. gondii strains and high genetic diversity of the parasites in felines in this tropical region of Mexico.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03129-9.

Autoantibodies Against Ubiquitous and Confined Antigens in Patients With Ocular, Neuro-Ophthalmic and Congenital Cerebral Toxoplasmosis

Toxoplasma gondii infection can trigger autoreactivity by different mechanisms. In the case of ocular toxoplasmosis, disruption of the blood-retinal barrier may cause exposure of confined retinal antigens such as recoverin. Besides, cross-reactivity can be induced by molecular mimicry of parasite antigens like HSP70, which shares 76% identity with the human ortholog. Autoreactivity can be a determining factor of clinical manifestations in the eye and in the central nervous system. We performed a prospective observational study to determine the presence of autoantibodies against recoverin and HSP70 by indirect ELISA in the serum of 65 patients with ocular, neuro-ophthalmic and congenital cerebral toxoplasmosis. We found systemic autoantibodies against recoverin and HSP70 in 33.8% and 15.6% of individuals, respectively. The presence of autoantibodies in cases of OT may be related to the severity of clinical manifestations, while in cases with CNS involvement they may have a protective role. Unexpectedly, anti-recoverin antibodies were found in patients with cerebral involvement, without ocular toxoplasmosis; therefore, we analyzed and proved cross-reactivity between recoverin and a brain antigen, hippocalcin, so the immunological phenomenon occurring in one immune-privileged organ (e.g. the central nervous system) could affect the environment of another (egg. the eye).

Toxoplasma gondii infection in European mouflons (Ovis musimon) and captive wild felines from Puebla, México

The presence of Toxoplasma gondii in zoos is cause of alert because many susceptible species kept in captivity die of clinical toxoplasmosis. Moreover, excretion of T. gondii oocysts by infected captive wild felines into the facilities could pose a risk to workers. Herbivores in wild collections can serve as sentinels of local transmission, since they get infected by the consumption of oocysts present in ground or water. Both herbivores and felids may reveal the parasite variants which are circulating in the region. We determined the seroprevalence of T. gondii in European mouflons (n = 55) and wild felines (n = 15) from a private zoological collection located in the Eastern region of México, as well as the incidence in 41 of the mouflons using ELISA. The prevalence of T. gondii in mouflons was 14.5% (n = 55) and 17.1% (n = 41) in 2011 and 19.5% in 2012. The estimated incidence was 9.8%–12.2%. In wild felines the frequency was 80%. Four sero-positive animals (two mouflons and the two oldest African lions) were euthanized. Histopathology, conventional PCR (for B1 and SeqRep529 loci) and molecular characterization were carried out. All euthanized animals were positive to T. gondii by PCR. We identified a triple infection (I + II + III) in the brain of a mouflon. In conclusion, a high infective pressure of T. gondii in the collection was found, supported by changes in its prevalence in European mouflons. A high prevalence of infection in wild felines was determined. At least four genotypes of T. gondii are present in herbivores and carnivores, and one mouflon had a mixed infection.

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High infective pressure of T. gondii in mouflons and wild felines of a private collection in Puebla, Mexico.

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Four genotypes of T. gondii are present in herbivores and carnivores.

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A triple infection was found in one mouflon.

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First prospective cross-sectional study, not using serum banks.

Temporal expression of Toxoplasma stage-specific genes in brain tissue: coincidence with parasitological and histopathological findings in mice models

In the intermediate hosts, tachyzoites of T. gondii predominate in the acute stage while bradyzoites persist inside tissue cysts with the potential for reactivation. The two stages exhibit different metabolic and antigenic characters. The present study aimed to investigate temporal expression of Toxoplasma SAG1 and BAG1 genes in the brain tissue and the coincident parasitological and histopathological findings in mice models of toxoplasmosis. The study included group A: mice infected with RH strain and sacrificed 7 days post-infection (p.i.); group B: mice infected with RH strain and treated with sulfamethoxazole-trimethoprim (30 mg/kg/day and 150 mg/kg/day respectively) 24 h p.i. until sacrificed at days 5, 10, or 20 post-treatment; group C: mice infected with ME-49 strain and sacrificed at days 7, 27, 47, or 67 p.i; and group D: mice infected with ME-49 strain and received dexamethasone daily starting at day 68 p.i. and scarified at days 6 or 10 post-treatment. All mice were inspected daily for abnormal physical signs. Peritoneal exudate and brain homogenate were examined for detection of Toxoplasma stages. Brain sections were examined histopathologically. SAG1 and BAG1 gene expression was evaluated using reverse transcription real-time polymerase chain reaction and the ΔΔCt method. Results revealed that marked BAG1 upregulation is consistent with detection of Toxoplasma cysts and degenerative changes while predominance of tachyzoites and inflammatory infiltrate is compatible with SAG1 upregulation. The study sheds light on the potential for using stage-specific gene expression pattern as markers for evaluation of toxoplasmosis disease progression in clinical settings.

Molecular Detection and Genotyping of Toxoplasma gondii and Neospora caninum in Slaughtered Goats in Central China

Toxoplasma gondii and Neospora caninum infections can cause reproductive failure in animals, including goats, and toxoplasmosis is one of the most important foodborne diseases. However, information on the molecular prevalence and genetic characterization of T. gondii and N. caninum in the tissues of goats in China is limited. In this study, brain samples of 422 slaughtered goats were collected from slaughterhouses in Henan and Anhui provinces, Central China, and examined for the presence of T. gondii and N. caninum by nested polymerase chain reaction (PCR) based on B1 and NC5 genes, respectively. The prevalence of T. gondii and N. caninum DNA was 5.2% and 2.8%, respectively. No significant differences were found between the prevalences of two parasite infections and animal age, sex, and region (p > 0.05). Two of 22 T. gondii-positive samples were completely genotyped at 11 genetic markers (SAG1, [3' + 5'] SAG2, alternative SAG2 [alt. SAG2], SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) using PCR-restriction fragment length polymorphism, and were identified as genotype ToxoDB no. 225, which has not been previously reported in goats in any country worldwide. For N. caninum, two different sequences at the ITS1 region, three genotypes at the MS5 microsatellite locus, and one genotype at the MS8 locus were identified. This study showed that T. gondii and N. caninum are moderately prevalent in goats in Central China; however, it should be emphasized that T. gondii prevalence in goats poses a potential health threat for consumers in the investigated areas. To the best of our knowledge, this is the first report on the genetic characterization of N. caninum isolates from goats in China. Our results have important implications for a better understanding of the genetic diversity of these parasites in China.

Stray dogs in the tropical state of Chiapas, Mexico, harbour atypical and novel genotypes of Toxoplasma gondii

Genotyping of Toxoplasma gondii remains a relevant topic of study, since genotypes can be related to the presentation and severity of toxoplasmosis. To date, 292 restriction fragment length polymorphism genotypes have been described around the world. Serosurveys in southeastern Mexico have documented exposure in over 70% of people and certain animals. Recently, we have described new genotypes and mixed infections in feral cats from Quintana Roo. Thus, the aim of this study was to genotype T. gondii and to describe its genetic variability, from naturally infected stray dogs of Chiapas, which has different geographical and climatic conditions from those found at the Yucatan Peninsula and the other parts of the country. Eleven stray dogs were captured and bled to obtain DNA, and then they were euthanized to perform necropsies and to collect target tissues. Diagnosis of T. gondii was done by quantitative real-time PCR (qPCR) and endpoint PCR. Genotyping was carried out, amplifying 12 polymorphic markers and 15 microsatellites. Atypical SAG3 gene products were cloned and sequenced. All blood samples of dogs were positive to T. gondii DNA by PCR. Two isolates were obtained from pooled heart and diaphragm tissue of two dogs. Two complete PCR-RFLP genotypes were identified (type BrIII and #28). Four animals had mixed infections. A new RFLP atypical allele for the SAG3 marker was observed; cloning and sequencing analysis of this locus revealed mixed infection by a strain identical to GT1, and one type I × II intragenic recombinant. The microsatellite analysis revealed that both isolates are atypical. Thus, atypical new genotypes of T. gondii and mixed infections were found in dogs of Chiapas. The results found here and in genotyping studies in México suggest that the southeastern region favours wide genetic diversity of T. gondii and the possible presence of virulent genotypes such as those found in central and South America.

Testing New Peptides From Toxoplasma gondii SAG1, GRA6, and GRA7 for Serotyping: Better Definition Using GRA6 in Mother/Newborns Pairs With Risk of Congenital Transmission in Mexico

Toxoplasma gondii variant influences clinical profile in human congenital and ocular toxoplasmosis. Parasite genotyping represents a challenge due to insufficient amount of genetic material of the protozoan in the host samples, and isolates are hard to obtain, especially from pediatric patients. An alternative is serotyping, which is based on the presence of specific antibodies against polymorphic proteins related to virulence; the more widely used are GRA6 and GRA7, but most works report cross reactions among the classical strains (I, II, and III). We designed new peptides of GRA6, GRA7, and SAG1 proteins, with more SNPs among the three clonal strains than those previously designed. This was done by identifying BcR and polymorphic epitopes by means of bioinformatics; then we designed peptides with linkers joining the specific regions and predicted their 3D structure. With the commercial molecules synthesized on the basis of these designs, we tested 86 serum samples from 42 mother/newborn pairs and two congenitally infected newborns, by indirect ELISA. We implemented a strategy to determine the serotype based on scatter plots and a mathematical formula, using ratios among reactivity indexes to peptides. We found low frequency of samples reactive to GRA7 and SAG1, and cross reactions between GRA6 serotypes I and III; we modified these later peptides and largely improved distinction among the three clonal strains. The chronicity of the infection negatively affected the reactivity index against the peptides. Serotyping both members of the mother/child pair improves the test, i.e., among 26% of them only one member was positive. Serotype I was the most frequent (38%), which was congruent with previous genotyping results in animals and humans of the same area. This serotype was significantly more frequent among mothers who transmitted the infection to their offspring than among those who did not (53 vs. 8%, p = 0.04) and related to disease dissemination in congenitally infected children, although non-significantly. In conclusion, serotyping using the improved GRA6 peptide triad is useful to serotype T. gondii in humans and could be implemented for clinical management and epidemiological studies, to provide information on the parasite type in specific areas.

Molecular genotyping and serological evaluation of Toxoplasma gondii in mothers and their spontaneous aborted fetuses in Southwest of Iran

BACKGROUND

Given the lack of routine screening and the high prevalence of toxoplasmosis in pregnant women in Iran, the current study aimed to find out the rate and features of Toxoplasma gondii infection in the spontaneously aborted human fetuses in Kohgiluyeh and Boyer-Ahmad Province, Southwestern Iran.

METHODS

This cross-sectional study was performed on 100 spontaneously aborted fetuses' tissues and their mother blood samples. The mothers' sera were evaluated for anti-Toxoplasma antibodies while their buffy coat and aborted fetuses tissues were evaluated for Toxoplasma DNA. PCR product at GRA6 locus was sequenced and phylogenetic analysis was done. Likewise, quantitative Real-Time PCR was performed to find out the parasite burdens in mothers buffy coat and fetuses tissues.

RESULTS

Using serological method, anti-Toxoplasma IgG and IgM antibodies were detected in 7 (7%) and 3 (3%) out of 100 sera from women with spontaneous abortion. Real-time PCR method detected T. gondii DNA in the buffy coat of one seronegative and 2 (out of 3) IgM seropositive cases. None of the samples from aborted fetuses were infected with T. gondii. BLAST and phylogenetic analysis showed that the sequenced isolates belonged to type I of T. gondii and two identified T. gondii isolates were taxonomically grouped into one clade.

CONCLUSION

Our findings revealed type I genotype of T. gondii in two mothers with spontaneous abortion, without fetus involvement. It is necessary to examine more aborted fetuses' samples from different geographical areas to determine the association between Toxoplasma genotype and abortion.

Mixed Toxoplasma gondii infection and new genotypes in feral cats of Quintana Roo, México

Toxoplasmosis is a zoonosis caused by Toxoplasma gondii that infects homeothermic animals, including humans. To date, as many as 287 genotypes have been described worldwide. Genetic characterization of the parasite is crucial because the parasite type can determine the presentation and severity of toxoplasmosis. Previously, we reported that the Yucatán Peninsula has a frequency of infection of over 70% in humans and other animals; moreover, there are seven species of felids, including domestic cats; thus, we hypothesized that this might be a region with a high diversity of the parasite. Nevertheless, no genotyping of this protozoan has been performed in this region. Thus, the aim of this study was to genotype T. gondii from naturally infected feral cats of Quintana Roo, within the Yucatán Peninsula, and to describe its genetic variability. Eleven feral cats were captured and bled to obtain the buffy coat; then, they were euthanized to collect target organs or tissues to extract DNA. Samples were processed by PCR for diagnosis, and ten polymorphic markers were genotyped by PCR-RFLP. Atypical GRA6 gene products were cloned and sequenced. Ten of the eleven cats were PCR positive for toxoplasmosis in blood; of these, seven had mixed infections. Also, two isolates were obtained from the heart and diaphragm of two animals. At least 23 different genotypes were detected, from which 18 are new worldwide. From the atypical GRA6 gene cloning and sequencing analysis, a mixed infection was discovered, due to one strain identical to GT1 and another to VAND. In conclusion, T. gondii genetic diversity in the region is high and different from that in other regions, with new genotypes exclusive to México and some others shared with USA and South America.