Evolving characteristics of toxoplasmosis in patients infected with human immunodeficiency virus-1: clinical course and Toxoplasma gondii-specific immune responses

Genome-wide and targeted CRISPR screens identify RNF213 as a mediator of interferon gamma-dependent pathogen restriction in human cells

To define cellular immunity to the intracellular pathogen Toxoplasma gondii, we performed a genome-wide CRISPR loss-of-function screen to identify genes important for (interferon gamma) IFN-γ-dependent growth restriction. We revealed a role for the tumor suppressor NF2/Merlin for maximum induction of Interferon Stimulated Genes (ISG), which are positively regulated by the transcription factor IRF-1. We then performed an ISG-targeted CRISPR screen that identified the host E3 ubiquitin ligase RNF213 as necessary for IFN-γ-mediated control of T. gondii in multiple human cell types. RNF213 was also important for control of bacterial (Mycobacterium tuberculosis) and viral (Vesicular Stomatitis Virus) pathogens in human cells. RNF213-mediated ubiquitination of the parasitophorous vacuole membrane (PVM) led to growth restriction of T. gondii in response to IFN-γ. Moreover, overexpression of RNF213 in naive cells also impaired growth of T. gondii. Surprisingly, growth inhibition did not require the autophagy protein ATG5, indicating that RNF213 initiates restriction independent of a previously described noncanonical autophagy pathway. Mutational analysis revealed that the ATPase domain of RNF213 was required for its recruitment to the PVM, while loss of a critical histidine in the RZ finger domain resulted in partial reduction of recruitment to the PVM and complete loss of ubiquitination. Both RNF213 mutants lost the ability to restrict growth of T. gondii, indicating that both recruitment and ubiquitination are required. Collectively, our findings establish RNF213 as a critical component of cell-autonomous immunity that is both necessary and sufficient for control of intracellular pathogens in human cells.

The determinants regulating Toxoplasma gondii bradyzoite development

Toxoplasma gondii is an obligate intracellular zoonotic pathogen capable of infecting almost all cells of warm-blooded vertebrates. In intermediate hosts, this parasite reproduces asexually in two forms, the tachyzoite form during acute infection that proliferates rapidly and the bradyzoite form during chronic infection that grows slowly. Depending on the growth condition, the two forms can interconvert. The conversion of tachyzoites to bradyzoites is critical for T. gondii transmission, and the reactivation of persistent bradyzoites in intermediate hosts may lead to symptomatic toxoplasmosis. However, the mechanisms that control bradyzoite differentiation have not been well studied. Here, we review recent advances in the study of bradyzoite biology and stage conversion, aiming to highlight the determinants associated with bradyzoite development and provide insights to design better strategies for controlling toxoplasmosis.

Anti-Toxoplasmic Immunoglobulin G Quantitation Correlates with Immunovirological Parameters of HIV-Infected Cameroonians

BACKGROUND

Toxoplasmosis is still a neglected common opportunistic infection in immunocompromised individuals, who are mainly people living with HIV (PLHIV) in whom reactivation of toxoplasmosis may occur with advanced HIV conditions in resource-limited settings (RLS).

OBJECTIVE

The objective was to assess the correlation between anti-toxoplasmic immunoglobulin G (anti-Toxo IgG) concentration and the immuno-virological status of PLHIV.

METHODS

A cross-sectional study was conducted in the year 2018 among 100 PLHIV aged ≥18 years in Yaounde-Cameroon. For each participant, anti-Toxo IgG, CD4-T lymphocytes, and plasma viral load (PVL) were measured using ELISA, flow cytometry, and real-time PCR, respectively.

RESULTS

Overall, 56% of the participants were seropositive for anti-Toxo IgG, while 33% were negative and 11% were equivocal. All (n=19) those with PVL>1000 copies/mL were seropositive to anti-Toxo IgG versus 52.85% (37/70) with PVL<1000 copies/mL; p<0.0001. Interestingly, all (n=11) those with severe immunodeficiency (T-CD4<200 cells/μL) were positive to anti-Toxo IgG versus 57.69% (45/78) with T-CD4>200 cells/μL; p<0.0001. Most importantly, PVL and anti- Toxo IgG concentration were positively correlated (r = 0.54; p<0.0001), while T-CD4 and anti- Toxo IgG concentration were negatively correlated (r = - 0.70; p<0.0001). Adjusting age, gender, immune status, and virological profile in logistic regression shows that only immune status was independently associated with the serological status of toxoplasmosis (p=0.0004).

CONCLUSION

In Cameroon, about half of PLHIV might be seropositive to anti-Toxo IgG, with decreasing immunity appearing as a risk of toxoplasmosis relapse. Thus, in the context of immunodeficiency, routine quantification of anti-Toxo IgG would alleviate the programmatic burden of this opportunistic infection in RLS with the generalized HIV epidemic.

Development of a risk scoring system for prognostication in HIV-related toxoplasma encephalitis

BACKGROUND

This study aims to evaluate specific risk factors influencing prognosis of HIV-infected patients with toxoplasma encephalitis (TE) in order to develop a prognostic risk scoring system for them.

METHODS

This is a six-center retrospective study of hospitalized HIV/TE patients. Data including six-week mortality after diagnosis, baseline characteristics, clinical features, laboratory tests and radiological characteristics of eligible patients were assimilated for risk model establishing.

RESULTS

In this study, the six-week mortality among 94 retrospective cases was 11.7% (11/94). Seven specific risk factors, viz. time from symptom onset to presentation, fever, dizziness, CD4+ T-cell counts, memory deficits, patchy brain lesions, and disorders of consciousness were calculated to be statistically associated with mortality. A criterion value of '9' was selected as the optimal cut-off value of the established model. The AUC of the ROC curve of this scoring model was 0.976 (p < 0.001). The sensitivity and specificity of the risk scoring model was 100.0 and 86.9%, respectively, which were 81.8 and 94.1% of this scoring model in the verification cohort, respectively.

CONCLUSIONS

The developed scoring system was established with simple risk factors, which also allows expeditious implementation of accurate prognostication, and appropriate therapeutic interventions in HIV-infected patients with TE.

Targeted therapies for autoimmune/idiopathic nonmalignant diseases: risk and management of opportunistic infections

INTRODUCTION

The management of patients affected by autoimmune/idiopathic diseases has been revolutionized by the development of targeted therapies (TT). However, the use of TT is complicated by several adverse events, like opportunistic infections (OIs). The potential of TT to predispose to OIs mainly depends on the site of action; nevertheless, such associations are far from being deterministic, because many factors could increase the infection risk.

AREAS COVERED

The impact on the infective risk of different TT used for autoimmune/idiopathic diseases is far from being completely understood. Indeed, many post-marketing reports documented severe or unexpected infections in patients treated with TT that did not emerge during registrative trials. In this review, the authors attempt to provide an easy and practical update about the 'infectious' safety of TT and examine the management strategies of OIs and other infections more frequently observed in the course of treatment with TT.

EXPERT OPINION

The authors suggest to precisely schedule the clinical management of these subjects, both to prevent and eventually treat promptly the TT-related infectious complications. A coordinated approach should be implemented from different medical specialties to improve the overall understanding of safety of TT and, in general, the management of opportunistic infections in immune-compromised hosts.

Secretory Microneme Proteins Induce T-Cell Recall Responses in Mice Chronically Infected with Toxoplasma gondii

Current diagnosis of toxoplasmosis relies almost exclusively on antibody detection, and while detection of IgG provides a useful estimate of prior infection, it does not alone indicate immune status. In contrast, detection of IFN-γ responses to T. gondii antigens has been used to monitor immune responsiveness in HIV-infected patients, thus providing valuable predictions about the potential for disease reactivation. However, specific T. gondii antigens that can be used in assays to detect cellular immunity remain largely undefined. In this study, we examined the diagnostic potential of microneme antigens of T. gondii using IFN-γ detection assays. Our findings demonstrate that MIC antigens (MIC1, MIC3, MIC4, and MIC6) elicit IFN-γ responses from memory T cells in chronically infected mice. Monitoring IFN-γ production by T cells stimulated with MIC antigens provided high sensitivity and specificity for detection of T. gondii infection in mice. Taken together, these studies suggest that microneme antigens might be useful as an adjunct to serological testing to monitor immune status during infection.

Microneme (MIC) proteins play important roles in the recognition, adhesion, and invasion of host cells by Toxoplasma gondii. Previous studies have shown that MIC proteins are highly immunogenic in the mouse and recognized by human serum antibodies. Here we report that T. gondii antigens MIC1, MIC3, MIC4, and MIC6 were capable of inducing memory responses leading to production of gamma interferon (IFN-γ) by T cells from T. gondii-infected mice. Production of IFN-γ was demonstrated using enzyme-linked immunosorbent spot (ELISPOT) assay and also intracellular cytokine staining. All four MIC antigens displayed very high sensitivity (100%) and specificity (86 to 100%) for detecting chronic infection. Interestingly, IFN-γ was produced by both CD4⁺ and CD8⁺ T cells in BALB/c mice but primarily by CD4⁺ T cells in C57BL/6 mice. Phenotypic characterization of IFN-γ-producing CD4⁺ and CD8⁺ T cells in BALB/c mice and CD4⁺ T cells in C57BL/6 mice revealed effector memory T cells (CD44^hi CD62L^lo) as the predominant cells that contributed to IFN-γ production in response to MIC antigens. Effector memory responses were seen in mice of different major histocompatibility complex class II (MHC-II) haplotypes, suggesting that MIC antigens contain epitopes that are broadly recognized.

IMPORTANCE Current diagnosis of toxoplasmosis relies almost exclusively on antibody detection, and while detection of IgG provides a useful estimate of prior infection, it does not alone indicate immune status. In contrast, detection of IFN-γ responses to T. gondii antigens has been used to monitor immune responsiveness in HIV-infected patients, thus providing valuable predictions about the potential for disease reactivation. However, specific T. gondii antigens that can be used in assays to detect cellular immunity remain largely undefined. In this study, we examined the diagnostic potential of microneme antigens of T. gondii using IFN-γ detection assays. Our findings demonstrate that MIC antigens (MIC1, MIC3, MIC4, and MIC6) elicit IFN-γ responses from memory T cells in chronically infected mice. Monitoring IFN-γ production by T cells stimulated with MIC antigens provided high sensitivity and specificity for detection of T. gondii infection in mice. Taken together, these studies suggest that microneme antigens might be useful as an adjunct to serological testing to monitor immune status during infection.

Quality of life and handgrip strength of HIV patients diagnosed with neurotoxoplasmosis

Abstract HIV / AIDS epidemic continues to be a major public health problem, and when there is poor adherence to treatment, patients become susceptible to other infections such as toxoplasmosis. The aim of this study was to evaluate the handgrip strength and quality of life of HIV infected patients diagnosed with neurotoxoplasmosis. A cross-sectional study was conducted with 40 HIV-infected patients, with and without diagnosis of neuroxoplasmosis.Sociodemographic and clinical profile information was collected, and handgrip strength and quality of life were evaluated. Almost all patients of both groups used antiretroviral therapy. In the handgrip strength evaluation, no statistical difference was observed for the right and left hand between groups with and without neurotoxoplasmosis (p> 0.05). However, the classifica-1 Federal University of Pará. Gradution of inadequate handgrip strength in the neurotoxoplasmosis group was significantly higher.ate Program in Tropical Diseases. In the quality of life domain, it was observed that financial concern had lower scores in the Belém, PA. Brazil. group with neurotoxoplasmosis (p = 0.0379). It was observed that neurotoxoplasmosis showedno association with epidemiological, clinical, handgrip strength and quality of life variables.2 State University of Pará. Center However, patients with neurotoxoplasmosis showed a trend towards lower muscle strength.

Parasitic and fungal infections

Parasitic infections of the central nervous system (CNS) comprise a plethora of infectious agents leading to a multitude of different disease courses and thus diagnostic and therapeutic challenges. The prevalence of different pathogens is basically dependent on geographic and ethnic backgrounds, its infectious route frequently involving a third party, such as flies or domestic animals. The present review focuses on cerebral malaria due to Plasmodium falciparum infection, and Toxoplasma gondii encephalitis. Fungi produce a large variety of inflammatory conditions of the CNS with a variegated spectrum of signs and symptoms, which may involve the meninges and the brain parenchyma, where they produce cerebritis or abscesses and granulomatous lesions, respectively. Fungal CNS lesions are increasingly prevalent and diagnostically relevant due to increasing numbers of human immunodeficiency virus-positive patients, increasing numbers of patients reaching old age suffering from malignant tumors or decreased immunity, and finally the increasing use of established and new immunosuppressive treatments, which increase the susceptibility of patients to develop invasive mycoses. Fungi appear with characteristic morphotypes comprising hyphae, yeasts, and pseudohyphae. The mode by which fungi penetrate into the CNS, and the host/immune requirements are incompletely understood and remain a challenge for research.

How Can Elispot Add Information to Improve Knowledge on Tropical Diseases?

Elispot has been used as an important tool for detecting immune cells' products and functions and has facilitated the understanding of host-pathogen interaction. Despite the incredible diversity of possibilities, two main approaches have been developed: the immunopathogenesis and diagnosis/prognosis of infectious diseases as well as cancer research. Much has been described on the topics of allergy, autoimmune diseases, and HIV-Aids, however, Elispot can also be applied to other infectious diseases, mainly leishmaniasis, malaria, some viruses, helminths and mycosis usually classified as tropical diseases. The comprehension of the function, concentration and diversity of the immune response in the infectious disease is pointed out as crucial to the development of infection or disease in humans and animals. In this review we will describe the knowledge already obtained using Elispot as a method for accessing the profile of immune response as well as the recent advances in information about host-pathogen interaction in order to better understand the clinical outcome of a group of tropical and neglected diseases.

Incidence, presentation and outcome of toxoplasmosis in HIV infected in the combination antiretroviral therapy era

BACKGROUND

HIV-associated incidence and prognosis of cerebral toxoplasmosis (CTX) is not well established during later years.

METHODS

From the Danish HIV Cohort Study, we identified 6325 HIV-infected individuals. We assessed incidence, mortality, predictive and prognostic factors of CTX during the pre-combination antiretroviral therapy (pre-cART; 1995-1996) and cART-era (1997-2014). Adjusted incidence rate ratios (aIRR), mortality rate ratios (aMRR) and 95% confidence intervals (CI) were assessed using Poisson regression analysis.

RESULTS

CTX IR was 1.17/1000 PYR (95% CI 0.93-1.47). We observed no change in CTX-risk in the first year after HIV-diagnosis, but a substantial reduction in mortality in the first 3 months after CTX diagnosis when comparing the cART-era to the pre-cART-era; {(aIRR: 0.79; 95% CI: 0.37-1.72) (aMRR: 0.15; 95% CI: 0.06-0.38)}. For individuals surviving the first year after HIV-diagnosis or the first 3 months after CTX-diagnosis, IRR and MRR had declined to minimal levels {(aIRR: 0.06; 95% CI: 0.03-0.10); (aMRR: 0.02; 95% CI: 0.01-0.05)}. Three years after CTX-diagnosis 30% of the patients still had neurological deficits.

CONCLUSION

Although, CTX remains an important cause of morbidity and mortality in the cART-era, with high prevalence of neurological sequelae, incidence and mortality has largely declined, especially among those surviving the first year after diagnosis.

Cerebral toxoplasmosis mimicking subacute meningitis in HIV-infected patients; a cohort study from Indonesia

BACKGROUND

HIV-associated subacute meningitis is mostly caused by tuberculosis or cryptococcosis, but often no etiology can be established. In the absence of CT or MRI of the brain, toxoplasmosis is generally not considered as part of the differential diagnosis.

METHODOLOGY/PRINCIPAL FINDINGS

We performed cerebrospinal fluid real time PCR and serological testing for Toxoplasma gondii in archived samples from a well-characterized cohort of 64 HIV-infected patients presenting with subacute meningitis in a referral hospital in Indonesia. Neuroradiology was only available for 6 patients. At time of presentation, patients mostly had newly diagnosed and advanced HIV infection (median CD4 count 22 cells/mL), with only 17.2% taking ART, and 9.4% PJP-prophylaxis. CSF PCR for T. Gondii was positive in 21 patients (32.8%). Circulating toxoplasma IgG was present in 77.2% of patients tested, including all in whom the PCR of CSF was positive for T. Gondii. Clinically, in the absence of neuroradiology, toxoplasmosis was difficult to distinguish from tuberculosis or cryptococcal meningitis, although CSF abnormalities were less pronounced. Mortality among patients with a positive CSF T. Gondii PCR was 81%, 2.16-fold higher (95% CI 1.04-4.47) compared to those with a negative PCR.

CONCLUSIONS/SIGNIFICANCE

Toxoplasmosis should be considered in HIV-infected patients with clinically suspected subacute meningitis in settings where neuroradiology is not available.

Toxoplasmosis

Toxoplasma gondii, an Apicomplexan, is a pathogic protozoan that can infect the central nervous system. Infection during pregnancy can result in a congenial infection with severe neurological sequelae. In immunocompromised individuals reactivation of latent neurological foci can result in encephalitis. Immunocompetent individuals infected with T. gondii are typically asymptomatic and maintain this infection for life. However, recent studies suggest that these asymptomatic infections may have effects on behavior and other physiological processes. Toxoplasma gondii infects approximately one-third of the world population, making it one of the most successful parasitic organisms. Cats and other felidae serve as the definite host producing oocysts, an environmentally resistant life cycle stage found in cat feces, which can transmit the infection when ingested orally. A wide variety of warm-blooded animals, including humans, can serve as the intermediate host in which tissue cysts (containing bradyzoites) develop. Transmission also occurs due to ingestion of the tissue cysts. There are three predominant clonal lineages, termed Types I, II and III, and an association with higher pathogenicity with the Type I strains in humans has emerged. This chapter presents a review of the biology of this infection including the life cycle, transmission, epidemiology, parasite strains, and the host immune response. The major clinical outcomes of congenital infection, chorioretinitis and encephalitis, and the possible association of infection of toxoplasmosis with neuropsychiatric disorders such as schizophrenia, are reviewed.

Toxoplasmic encephalitis in an AIDS cohort at Puerto Rico before and after highly active antiretroviral therapy (HAART)

Highly active antiretroviral therapy (HAART) significantly reduced the toxoplasmic encephalitis (TE) incidence in acquired immunodeficiency syndrome (AIDS) patients. The TE incidence and mortality were evaluated in an AIDS cohort followed in Puerto Rico before, during, and after HAART implementation in the Island. Of the 2,431 AIDS studied patients 10.9% had TE diagnosis, with an incidence density that decreased from 5.9/100 person-years to 1.1/100 person-years after HAART. Cox proportional hazard analysis showed substantial mortality reduction among TE cases who received HAART. No mortality reduction was seen in those cases who received TE prophylaxis. Although this study shows a TE incidence and mortality reduction in the AIDS cohort after HAART, the incidence was higher than those reported in the United States AIDS patients. Poor TE prophylaxis compliance might explain the lack of impact of this intervention. Strengthening the diagnostic and opportune TE diagnosis and prompt initiation of HAART in susceptible patients is important to control this opportunistic infection.

Cost-effectiveness analysis of raltegravir in treatment-experienced HIV type 1-infected patients in Spain

Raltegravir, a novel HIV-1 integrase inhibitor, has superior efficacy with optimized background treatment (OBT) vs. placebo + OBT in treatment-experienced HIV-1 patients. This study assessed the long-term cost effectiveness of raltegravir from a Spanish National Healthcare System perspective. A cohort-state-transition model was used to estimate clinical and economic outcomes associated with raltegravir + OBT vs. OBT alone. Subjects were stratified into health states according to HIV RNA level, CD4 count, and opportunistic infection (OI) history, and could transition into different health states over time based on projected long-term efficacy. Each health state was associated with a distinct treatment cost and utility (QoL) score. Model inputs for mortality, resource utilization, unit costs, OI risk, and long-term durability of viral suppression were obtained from clinical trials, published studies, and database analyses. Model outcomes were reported as incremental cost-effectiveness ratios (ICERs) in 2007 Euros per quality-adjusted life-year (euro/QALY) gained. Costs and QALYs were discounted at 6% per year based on Spanish cost-effectiveness guidelines. Extensive sensitivity analyses were conducted. Five years of treatment with raltegravir + OBT resulted in an additional 4.5 years of undiscounted life expectancy vs. OBT alone. The ICER of raltegravir + OBT vs. OBT alone was euro22,908/QALY and euro31,431/QALY for 3- and 5-year use, respectively. Lower ICERs were observed with lower discount rates (3%) for costs and benefits, lower raltegravir price (20%), and shorter treatment duration (3 years). ICER was also sensitive to analytical time horizon and alternative sources of QoL scores. In treatment-experienced Spanish patients, raltegravir was projected to provide survival benefits and be cost effective.