Age-dependent impairment of functional helper T cell responses to immunodominant epitopes of Toxoplasma gondii antigens in congenitally infected individuals

A multimodality therapeutic application on Toxoplasma gondii encephalitis utilizing Spiramycin and 'de novo' Ferula asafetida in immunodeficient mice

This study investigated a 'de Novo' medicinal herb, Ferula asafetida (FA), against toxoplasma encephalitis either alone or combined with spiramycin (SP). Female Swiss-Webster mice (n = 72) were divided into three batches. Batch-I received no DMS to serve as an immunocompetent control, batch-II was immune-suppressed with the DMS (0.25 mg/g/day) for 14 days pre-infection, whilst batch-III was immune-suppressed with the DMS on the same day of infection. All experimental mice were inoculated with Toxoplasma gondii ME49 cysts (n = 75). Each batch was split into four subgroups: Mono-SP, mono-FA, combined drug (SP + FA), or neither. Therapies were administered on day zero of infection in batches (I and II) and 35 days post-infection in batch (III). Treatments lasted for 14 days, and mice were sacrificed 60 days post-infection. Histopathological changes, cysts load, and CD4 and CD8 T-cells were counted in brain tissues. The cyst-load count in mice receiving SP + FA was significantly (p < .0001) the least compared to the mono treatments in all protocols. Interestingly, the combined therapy demolished the T-cell subsets to zero in immunocompetent and immunocompromised infected mice. In conclusion, F. asafetida might be a powerfully natural, safe vehicle of SP in the digestive system and/or across the brain-blood barrier to control toxoplasmosis even through immunodeficient conditions.

Comparative Detection of Immunoglobulin Isotypes and Subclasses against Toxoplasma gondii Soluble Antigen in Serum and Colostrum Samples from Puerperal Women

Background: Toxoplasma gondii is an obligate intracellular parasite that can infect several species, including humans, and can cause severe damage to the fetus when the infection occurs during pregnancy. The environment and/or food contamination are critical to spreading the infection. Human milk is rich in nutrients and bioactive elements that provide growth and development of the immune system of the newborn. All isotypes of immunoglobulins are present in human colostrum and they are produced from systemic or local sources. Breastfeeding protects the infant against various pathogens, but there is no conclusive study to detect IgG subclasses in colostrum against T. gondii. Therefore, the aim of this study was to detect and evaluate the presence of antibody isotypes against T. gondii in paired samples of serum and colostrum. Methods: The study included 283 puerperal patients. ELISA (Enzyme-Linked Immunosorbent Assay) for detection of anti-T. gondii-specific IgM, IgA, and IgG isotypes and IgG1, IgG3, and IgG4 subclasses were conducted on paired samples of serum and colostrum. Results: It was found that 45.9%, 6.0%, and 2.1% of serum samples and 45.2%, 7.1%, and 2.1% of colostrum samples were positive for IgG, IgM, and IgA, respectively. Specific IgG1, IgG3, and IgG4 were positive, respectively, in 98.5%, 54.6%, and 44.6% of serum samples, in contrast with 56.9%, 78.5%, and 34.6% of colostrum samples. Thus, the predominant reactivity of IgG subclasses against T. gondii was IgG1 in serum and IgG3 in colostrum. The higher percentage of positive samples and higher levels of anti-T. gondii IgG3 antibodies were observed in colostrum, when compared to serum samples, suggesting a local production of this subclass. IgG3 and IgG1 subclasses presented different percentages of positivity in serum and colostrum. Only the IgG1 subclass showed a significant correlation between the levels of anti-T. gondii in serum and colostrum, suggesting that IgG1 in breast milk comes from a systemic source. IgG4 showed a similar percentage of positivity in both sample types, but no significant correlation was observed between their levels. Conclusion: Colostrum presents representative levels of IgM, IgA, IgG1, IgG3, and IgG4 antibodies specific to T. gondii. The detection of these antibodies presents the potential for diagnostic application of colostrum samples to better identify the diagnostic status of T. gondii infection, especially during the acute phase. In addition, breastfeeding can also be a possible source of protective antibodies for the newborn against toxoplasmosis, an anthropozoonosis maintained by environmental infection, which interferes in the public health of many countries.

[Peptide phage display in biotechnology and biomedicine]

To date peptide phage display is one of the most common combinatorial methods used for identifying specific peptide ligands. Phage display peptide libraries containing billions different clones successfully used for selection of ligands with high affinity and selectivity toward wide range of targets including individual proteins, bacteria, viruses, spores, different kind of cancer cells and variety of nonorganic targets (metals, alloys, semiconductors etc.) Success of using filamentous phage in phage display technologies relays on the robustness of phage particles and a possibility to genetically modify its DNA to construct new phage variants with novel properties. In this review we are discussing characteristics of the most known non-commercial peptide phage display libraries of different formats (landscape libraries in particular) and their successful applications in several fields of biotechnology and biomedicine: discovery of peptides with diagnostic values against different pathogens, discovery and using of peptides recognizing cancer cells, trends in using of phage display technologies in human interactome studies, application of phage display technologies in construction of novel nano materials.

Early detection of Toxoplasma gondii infection by using a interferon gamma release assay: A review

Antibody-based serological tests are currently the most common diagnostic methods for detection of Toxoplasma gondii; however, these tests bear several limitations. Recently, Interferon-gamma release assay (IGRA), a T-cell-based test, was introduced as an in vitro test for detection of T. gondii infection. Few studies have investigated the potential role of cell immunity in diagnosis of toxoplasmosis. IGRA accurately distinguished infected from uninfected individuals, showing strong lymphocyte activation after in vitro stimulation with T. gondii antigens, even during the first days of life. IGRA is an easy-operation and low-cost method to measure cell mediated immunity against T. gondii. The results of this review underline the importance of evaluating cellular immunity to establish an early diagnosis particularly for congenital toxoplasmosis. Therefore, ELISA-based IGRA holds the potential to become a useful diagnostic tool for early detection of T. gondii infection.

Evaluation of colostrum as an alternative biological sample for the diagnosis of human congenital toxoplasmosis

Background

Toxoplasmosis is a zoonosis caused by Toxoplasma gondii, an intracellular protozoan parasite able to infect a wide range of hosts, including humans. Congenital infection can cause severe damage to the fetus. Thus, it is important to detect antibodies against the parasite to confirm clinical manifestations. Considering that all immunoglobulin isotypes may be present in biological samples from newborns and their mothers, this study aimed to evaluate the ability to diagnose recent toxoplasmosis by using colostrum, as an alternative noninvasive way to obtain biological samples, as well as to determine correlation rates between antibodies from serum samples to detect IgG, IgM and IgA isotypes against T. gondii.

Methods

A total of 289 puerperal women from Clinical Hospital of Federal University of Uberlândia (mean age: 24.8 years, range: 14 – 43 years) took part in this study. Serum and colostrum samples from these patients were analyzed using ELISA and immunoblotting assays for soluble antigens from T. gondii.

Results

ELISA immunoassays with serum samples showed reactivity in 47.0, 6.9 and 2.8 % of samples to anti-T. gondii IgG, IgM and IgA, respectively, in comparison with colostrum samples, which showed reactivity in 46.0, 7.9 and 2.8 % of samples to the same isotypes. Also, significant correlation rates of anti-T. gondii antibody levels between serum and colostrum samples were observed. Interestingly, reactivity to IgM and/or IgA in colostrum and/or serum confirmed clinical manifestations of congenital toxoplasmosis in three newborns. Immunoblotting assays showed that it is possible to detect IgG, IgM and IgA antibodies against various antigens of T. gondii in serum and colostrum samples. IgG antibodies in serum and colostrum samples recognized more antigenic fractions than IgM and IgA antibodies. Serum IgG detected more antigenic fractions than IgG antibodies present in the colostrum of the same patient. In contrast, specific IgA present in colostrum recognized a higher number of antigens than IgA present in serum samples of the same patient.

Conclusions

Overall, the results show that it is important to investigate the occurrence of congenital toxoplasmosis, even at puerperal period. Furthermore, this study demonstrates that T. gondii-specific IgG, IgM and IgA antibodies in serum and colostrum samples from puerperal women may be detected with a significant correlation, suggesting that colostrum may also be used as an alternative biological sample to efficiently diagnose recent human toxoplasmosis.

Enhancing in silico protein-based vaccine discovery for eukaryotic pathogens using predicted peptide-MHC binding and peptide conservation scores

Given thousands of proteins constituting a eukaryotic pathogen, the principal objective for a high-throughput in silico vaccine discovery pipeline is to select those proteins worthy of laboratory validation. Accurate prediction of T-cell epitopes on protein antigens is one crucial piece of evidence that would aid in this selection. Prediction of peptides recognised by T-cell receptors have to date proved to be of insufficient accuracy. The in silico approach is consequently reliant on an indirect method, which involves the prediction of peptides binding to major histocompatibility complex (MHC) molecules. There is no guarantee nevertheless that predicted peptide-MHC complexes will be presented by antigen-presenting cells and/or recognised by cognate T-cell receptors. The aim of this study was to determine if predicted peptide-MHC binding scores could provide contributing evidence to establish a protein's potential as a vaccine. Using T-Cell MHC class I binding prediction tools provided by the Immune Epitope Database and Analysis Resource, peptide binding affinity to 76 common MHC I alleles were predicted for 160 Toxoplasma gondii proteins: 75 taken from published studies represented proteins known or expected to induce T-cell immune responses and 85 considered less likely vaccine candidates. The results show there is no universal set of rules that can be applied directly to binding scores to distinguish a vaccine from a non-vaccine candidate. We present, however, two proposed strategies exploiting binding scores that provide supporting evidence that a protein is likely to induce a T-cell immune response-one using random forest (a machine learning algorithm) with a 72% sensitivity and 82.4% specificity and the other, using amino acid conservation scores with a 74.6% sensitivity and 70.5% specificity when applied to the 160 benchmark proteins. More importantly, the binding score strategies are valuable evidence contributors to the overall in silico vaccine discovery pool of evidence.

Congenital parasitic infections: a review

This review defines the concepts of maternal-fetal (congenital) and vertical transmissions (mother-to-child) of pathogens and specifies the human parasites susceptible to be congenitally transferred. It highlights the epidemiological features of this transmission mode for the three main congenital parasitic infections due to Toxoplasma gondii, Trypanosoma cruzi and Plasmodium sp. Information on the possible maternal-fetal routes of transmission, the placental responses to infection and timing of parasite transmission are synthesized and compared. The factors susceptible to be involved in parasite transmission and development of congenital parasitic diseases, such as the parasite genotypes, the maternal co-infections and parasitic load, the immunological features of pregnant women and the capacity of some fetuses/neonates to overcome their immunological immaturity to mount an immune response against the transmitted parasites are also discussed and compared. Analysis of clinical data indicates that parasitic congenital infections are often asymptomatic, whereas symptomatic newborns generally display non-specific symptoms. The long-term consequences of congenital infections are also mentioned, such as the imprinting of neonatal immune system and the possible trans-generational transmission. The detection of infection in pregnant women is mainly based on standard serological or parasitological investigations. Amniocentesis and cordocentesis can be used for the detection of some fetal infections. The neonatal infection can be assessed using parasitological, molecular or immunological methods; the place of PCR in such neonatal diagnosis is discussed. When such laboratory diagnosis is not possible at birth or in the first weeks of life, standard serological investigations can also be performed 8-10 months after birth, to avoid detection of maternal transmitted antibodies. The specific aspects of treatment of T. gondii, T. cruzi and Plasmodium congenital infections are mentioned. The possibilities of primary and secondary prophylaxes, as well as the available WHO corresponding recommendations are also presented.

Diagnostic approach to ocular toxoplasmosis

Toxoplasmic retinochoroiditis is deemed a local event, which may fail to evoke a detectable systemic immune response. A correct diagnosis of the disease is a necessary basis for estimating its clinical burden. This is not so difficult in a typical clinical picture. In atypical cases, further diagnostic efforts are to be installed. Although the aqueous humor may be analyzed for specific antibodies or the presence of parasitic DNA, the DNA burden therein is low, and in rare instances a confirmation would necessitate vitreous sampling. A laboratory confirmation of the diagnosis is frustrated by individual differences in the time elapsing between clinical symptoms and activation of specific antibody production, which may result in false negatives. In congenital ocular toxoplasmosis, a delay in the onset of specific local antibody production could reflect immune tolerance. Herein, the authors attempt to provide a simple and practicable algorithm for a clinically tailored diagnostic approach in atypical instances.

Lambda-display: a powerful tool for antigen discovery

Since its introduction in 1985, phage display technology has been successfully used in projects aimed at deciphering biological processes and isolating molecules of practical value in several applications. Bacteriophage lambda, representing a classical molecular cloning and expression system has also been exploited for generating large combinatorial libraries of small peptides and protein domains exposed on its capsid. More recently, lambda display has been consistently and successfully employed for domain mapping, antigen discovery and protein interaction studies or, more generally, in functional genomics. We show here the results obtained by the use of large libraries of cDNA and genomic DNA for the molecular dissection of the human B-cell response against complex pathogens, including protozoan parasites, bacteria and viruses. Moreover, by reviewing the experimental work performed in recent investigations we illustrate the potential of lambda display in the diagnostics field and for identifying antigens useful as targets for vaccine development.

Diagnosis of congenital toxoplasmosis by using a whole-blood gamma interferon release assay

Congenital toxoplasmosis in newborns is generally subclinical, but infected infants are at risk of developing ocular lesions. Diagnosis at birth relies mainly on serological tests. Cell-mediated immunity plays the major role in resistance to infection but is not routinely investigated for diagnostic purposes. Here, we describe a simple test based on the gamma interferon (IFN-gamma) response after stimulation of whole blood by crude parasitic antigens. One milliliter of heparinized blood was centrifuged; plasma was kept for routine serological tests, and pellets were resuspended in culture medium. After 24 h of culture in the presence of crude Toxoplasma gondii antigen, the cells were centrifuged and the supernatant was assayed for IFN-gamma. For 62 infants under 1 year of age born to mothers who were infected during pregnancy, the sensitivity and specificity of the test were 94% (with positive results for 16 of 17 infected infants) and 98% (with negative results for 44 of 45 uninfected infants), respectively. The false-negative result was for a treated baby who gave positive results after the withdrawal of treatment. The false positive was obtained for a 3-month-old baby. For a cohort of 124 congenitally infected patients between 1 and 30 years of age, the sensitivity of the assay was 100%. We present a simple test based on IFN-gamma secretion to assess cell-mediated immunity in toxoplasmosis. As only 1 ml of blood is required to investigate humoral and cellular immunity, our assay is well adapted for the study of congenital toxoplasmosis in infants. Using purified antigens or recombinant peptides may improve the test performance.

Protozoan and helminth infections in pregnancy. Short-term and long-term implications of transmission of infection from mother to foetus

This review of protozoan and helminth infections in pregnancy focuses on the impact on the immune response in the newborn infant to maternal infection. Studies of protozoan and helminth infections in pregnant women and in their offspring have shown that children exposed to antigens or microorganisms during pregnancy often have a reduced immune response to these infections. The most common finding is a reduced IFN gamma response to specific antigens regardless of specific infection studied. In some studies the impaired immune response disappeared before the age of one year, while in other studies the impaired immune response was present as much as two decades after birth. Data from chronic viral infections like Rubella, cytomegalovirus and hepatitis B also show that congenital or perinatal infections may result in a life-long inability to control the infections. Studies of both helminth and protozoan infections show that children exposed to antigens during gestation have a microorganism-specific impaired immune response which is characterized by reduced IFN-gamma and stimulation of responses to specific antigens.

Molecular dissection of the human B cell response against cytomegalovirus infection by lambda display

Human cytomegalovirus (HCMV), a ubiquitous herpesvirus, is the main cause of congenital abnormalities and mental retardation in newborns and is also responsible for severe life-threatening complications in immunocompromised individuals, including AIDS patients and transplant recipients. The disorders generated by cytomegalovirus are closely associated with the competence of the host immune system and both humoral and cell-mediated mechanisms are involved in the response to viral infection. To identify viral proteins recognized by host antibody responses, a cytomegalovirus genome library was created and displayed on lambda bacteriophage. The challenge of such a library with sera from individuals with congenital or acquired infection allowed the identification of a wide panel of recombinant bacteriophages carrying cytomegalovirus B cell epitopes. Epitope-containing fragments within the families of tegument proteins (pUL25, pUL32), structural proteins (pUL48, pUL56) and glycoproteins (pUL55) were identified. Moreover, library screening permitted isolation of phage clones carrying an antigenic region of an uncharacterized HCMV protein encoded by the UL71 open reading frame (ORF), highlighting the potential of lambda display technology in antigen and epitope discovery.