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Summary: Diagnostic tests for toxoplasmosis are based on serological techniques due to their high sensitivity. Some IgG subclasses are related to clinical outcome in the congenital form. In this work, we determined the levels of IgG, IgA, IgG1, IgG2, IgG3 and IgG4 anti‐Toxoplasma gondii antibodies in paired saliva and serum samples from 91 women by indirect ELISA using a crude extract of the RH strain. The levels of IgA, IgG2, IgG3 and IgG4 antibodies and, to a lesser extent, IgG1 did not correlate between saliva and serum, that is, most cases that were positive for one Ig class in a sample were negative or very low in the other, and vice versa. We also observed that most samples of saliva that were positive for one IgG subclass were also positive for at least 2 of the other 3; this contrasted with findings in serum, wherein each person was positive almost exclusively for one subclass, as demonstrated before by us and other researchers. Although these findings are disappointing for the use in diagnosis, the richer response in saliva might indicate local exposure to T. gondii antigens without systemic infection; thus, saliva might be reflecting a local (protective?) response against this protozoan. [ABSTRACT FROM AUTHOR]

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.

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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

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.

Toxoplasma gondii is the etiological agent of toxoplasmosis. Mother-to-child transmission of this parasite can occur during pregnancy. Newborns with congenital toxoplasmosis may develop central nervous system impairment, with severity ranging from subclinical manifestations to death. A proinflammatory/regulated specific immune profile is crucial in the defense against the parasite; nevertheless, its role in the infected pregnant women and the congenitally infected offspring has been poorly explored, and there is still no consensus about its relation to parasite vertical transmission or to severity and dissemination in the congenitally infected newborns. This work aimed to characterize these relations by means of principal component and principal factor analyses. For this purpose, we determined the specific production of the four immunoglobulin G antibody subclasses, cytokines, and lymphocyte proliferation in the T. gondii- infected pregnant women-10 who transmitted the infection to their offspring and seven who did not-as well as in 11 newborns congenitally infected and grouped according to disease severity (five mild and six moderate/severe) and dissemination (four local and seven disseminated). We found that the immune response of nontransmitter women differed from that of the transmitters, the latter having a stronger proinflammatory response, supporting a previous report. We also found that newborns who developed moderate/severe disease presented higher levels of lymphocyte proliferation, particularly of CD8 + and CD19 + cells, a high proportion of tumor necrosis factor α producers, and reduced expression of the immune modulator transforming growth factor β, as opposed to children who developed mild clinical complications. Our results suggest that a distinctive, not regulated, proinflammatory immune response might favor T. gondii vertical transmission and the development of severe clinical manifestations in congenitally infected newborns., (Copyright © 2020 Gómez-Chávez, Cañedo-Solares, Ortiz-Alegría, Flores-García, Figueroa-Damián, Luna-Pastén, Gómez-Toscano, López-Candiani, Arce-Estrada, Bonilla-Ríos, Mora-González, García-Ruiz and Correa.)

Toxoplasmosis is a parasitic zoonosis distributed worldwide, caused by the ingestion of contaminated water/food with the parasite Toxoplasma gondii . If a pregnant woman is infected with this parasite, it may be transmitted to the fetus and produce ocular, neurological, or systemic damage with variable severity. The strength and profile of mother's immune response have been suggested as important factors involved in vertical transmission rate and severity of clinical outcome in the congenitally infected fetus. The aim of this work was to evaluate a possible relation between the mother's immune response during pregnancy and congenital transmission to the fetus. We obtained peripheral blood from T. gondii infected pregnant woman and tested it for anti T. gondii (IgG1, IgG2, IgG3, IgG4, and IgA) in serum. Peripheral blood mononuclear cells (PBMCs) were isolated to analyze the in vitro effect of soluble T. gondii antigens on proliferation and production of cytokines. We found that IgG2-4 and IgA antibodies and lymphocytes proliferation, especially CD4 + , CD8 + , and CD19 + were positive in a higher proportion of cases in transmitter than in non-transmitter women. Furthermore, IgG2-3 and IgA anti- Toxoplasma antibody levels were higher in those mothers who transmitted the infection than in those who did not. Interestingly, a higher proportion of positive cases to IFN-γ and negatives to the immunoregulatory cytokine TGF-β, were related to T. gondii vertical transmission. Our descriptive results are consistent with the paradoxical previous observations in murine models of congenital toxoplasmosis, which suggest that an increased immune response that protects the mothers from a disseminated or severe disease, and should protect the fetus from infection, is positively related to parasite transmission.

Introduction: There are few articles on evaluation of Toxoplasma gondii serological tests. Besides, commercially available tests are not always useful and are expensive for studies in open population. The aim of this study was to evaluate in-house ELISA and western blot for IgG antibodies in a representative sample of people living in Mexico., Methodology: Three hundred and five serum samples were randomly selected from two national seroepidemiological survey banks; they were taken from men and women of all ages and from all areas of the country. ELISA cut-off was established using the mean plus three standard deviations of negative samples. Western blots were analysed by two experienced technicians and positivity was established according to the presence of at least three diagnostic bands. A commercial ELISA kit was used as a third test. Two reference standards were built up: one using concordant results of two assays leaving the evaluated test out and the other in which the evaluated test was included (IN) with at least two concordant results to define diagnosis., Results: the lowest values of diagnostic parameters were obtained with the OUT reference standards: in-house ELISA had 96.9% sensitivity, 62.1% specificity, 49.6% PPV, 98.1% NPV and 71.8% accuracy, while western blot presented 81.8%, 89.7%, 84.0%, 88.2% and 86.6% values and the best kappa coefficient (0.72-0.82)., Conclusions: The in-house ELISA is useful for screening people of Mexico, due to its high sensitivity, while western blot may be used to confirm diagnosis. These techniques might prove useful in other Latin American countries.

Toxoplasma gondii disseminates and causes congenital infection by invasion of the endothelial cells. The aim of this study was to analyze the ability of two strains to invade two endothelial cell types. Tachyzoites of the RH and ME49 strains were expanded in Balb/c and C57BL6-RAG2-/- mice, respectively. Tachyzoites were harvested from 72 h Vero cell cultures and incubated for 30 min to 4 h at 10:1 parasite/cell ratio in 24-well plates, containing monolayers of either HMEC-1 line or human umbilical cells (HUVECs). The number of infected cells and parasitic vacuoles per infected cell were counted in Wright stained slides. A slow increase in the proportion of infected cells occurred but varied according to cell type-parasite strain combination: ME49 tachyzoites invaded up to 63% HMEC-1 cells, while RH parasites infected up to 19% HUVECs. ME49 and RH tachyzoites invaded 49 and 46% HUVECs and HMEC-1 cells, respectively. Reinvasion and formation of new parasitophorous vacuoles of infected cells was more frequent than invasion of noninfected cells. The results support that the factors influencing invasion, and thus dissemination and vertical transmission, are parasite type, host cell type/subtype, and activation state. Interestingly, T. gondii virulence does not seem to relay on its invasion efficiency, but probably on replication speed.

Global warming has had serious implications on dispersion of infectious diseases like toxoplasmosis. Since the frequency of Toxoplasma gondii largely depends on climatic conditions, we studied its prevalence by means of 3599 samples of the National Health Survey 2000 (NHS-2000) and 2916 of the National Health and Nutrition Survey 2006 (NHNS-2006) serum banks, obtained from 1-98 year old subjects of both genders and all states of Mexico. Anti-T.gondii IgG antibodies were determined by ELISA and confirmed by western blot. Crude, epidemiologically weighted and diagnosis-performance-adjusted prevalence values were calculated. Seroprevalence changes were compared between both surveys and among regions (north, center and coast). Also, correlations between changes in temperature or humidity and those in prevalence were measured. National crude prevalence was 60.1% and 62.6% for NHS-2000 and NHNS-2006, respectively. Weighted and adjusted values were 62.5% and 40.0% for NHS-2000, and 63.7 and 43.1% for NHNS-2006. Coastal states and children presented the largest increases between surveys, while the center of the country showed a decrease. An apparently higher prevalence of T. gondii infection was observed in both surveys compared to that performed in 1987, while a geographical re-distribution was found from 2000 to 2006, with a positive correlation between temperature and frequency deltas in 21 states where prevalence increased., (Copyright © 2012 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.)

Toxoplasma gondii congenital transmission depends partially on parasite load and genotype. Both factors were examined in 4 mother/newborn pairs with perinatal infection acquired in central Mexico. Type I and type I-related strains were identified. These results add information regarding T. gondii strains prevailing in humans, although neither the genotype nor the load were related to vertical transmission or damage.

Anti-Toxoplasma gondii antibodies of all IgG subclasses were studied in mother/newborn pairs. IgG1 in the mothers and IgG3 in the newborns were related to offspring clinical problems; IgG2 and IgG3 in the babies were markers of vertical transmission, and IgG4 in mothers or children were associated to clinical problems. IgG subclasses may be markers of congenital infection or clinical outcome.

Congenital toxoplasmosis is an obstetric problem in Mexico, but its actual frequency is unknown. Using a network for screening of non-infectious disorders, we performed a pilot study to determine the frequency of IgM antibodies to Toxoplasma gondii in 1,003 infants (53.1% male, mean +/- SD age = 18.3 +/- 13.0 days, birth weight = 3.116 +/- 0.453 kg) in Mexico City from March to April 2003. Blood samples embedded in filter paper were assayed for IgM antibodies using a capture enzyme-linked immunosorbent assay and results were confirmed by Western blot. Two asymptomatic newborns, one of them premature, had IgM and IgG antibodies in a serum sample taken from both the infant and the mother and were clinically followed. Our data suggest a frequency of approximately two cases of congenital T. gondii infection per 1,000 newborns in Mexico City.