Chagas Disease Diagnostic Practices at Four Major Hospital Systems in California and Texas

BACKGROUND

Chagas disease (CD) is a parasitic disease that affects ∼300 000 people living in the United States. CD leads to cardiac and/or gastrointestinal disease in up to 30% of untreated people. However, end-organ damage can be prevented with early diagnosis and antiparasitic therapy.

METHODS

We reviewed electronic health records of patients who underwent testing for CD at four hospital systems in California and Texas between 2016 and 2020. Descriptive analyses were performed as a needs assessment for improving CD diagnosis.

RESULTS

In total, 470 patients were tested for CD. Cardiac indications made up more than half (60%) of all testing, and the most frequently cited cardiac condition was heart failure. Fewer than 1% of tests were ordered by obstetric and gynecologic services. Fewer than half (47%) of patients had confirmatory testing performed at the Centers for Disease Control and Prevention.

DISCUSSION

Four major hospitals systems in California and Texas demonstrated low overall rates of CD diagnostic testing, testing primarily among older patients with end-organ damage, and incomplete confirmatory testing. This suggests missed opportunities to diagnose CD in at-risk individuals early in the course of infection when antiparasitic treatment can reduce the risk of disease progression and prevent vertical transmission.

Infection of a Nylon Foil Orbital Implant Due to Fusarium brachygibbosum and Lomentospora prolificans After Intranasal Methamphetamine Use

The authors describe a case of nylon foil implant infection caused by Fusarium brachygibbosum , and Lomentospora prolificans following medial orbital wall fracture repair in the setting of postoperative nasal methamphetamine use. A 61-year-old male presented with OS pain and swelling after a physical assault on his face. A CT of maxillofacial bones without contrast showed a moderately comminuted fracture of the medial wall of the left orbit with depression of fracture fragments into the left ethmoid air cells. Six days after repair of the medial wall fracture, the patient returned with a new onset headache, OS pain, and swelling to the left medial canthal area. He reported snorting methamphetamine approximately 48 hours before his current presentation. CT imaging showed fat stranding and soft tissue density in the extraconal space adjacent to the left medial rectus muscle and chronic fracture deformity of lamina papyracea with approximately 4 mm of medial displacement of the fracture fragments. The patient showed little clinical improvement after 48 hours of intravenous antibiotics, which led to the removal of the nylon foil implant by a left orbitotomy. Intraoperative tissue cultures grew coagulase-negative Staphylococcus , F. brachygibbosum , and Lomentospora (Scedosporium) prolificans . The patient was subsequently transitioned to oral clindamycin 600 mg three times daily and voriconazole 200 mg two times daily. To the authors' knowledge, this is the first case report to document an association between snorted methamphetamine and a fungal infection of an orbital implant.

DIAGNÓSTICO DE LEUCEMIA MIELOMONOCÍTICA CRÔNICA EM PACIENTE COM INFECÇÃO PELO NOVO CORONAVÍRUS: RELATO DE CASO

Discussão

PRIMO DIAGNÓSTICO DE LEUCEMIA MIELOIDE AGUDA EM VIGÊNCIA DE SÍNDROME DA ANGUSTIA RESPIRATÓRIA GRAVE POR COVID-19

Instituição

Objetivos

Material e métodos

Discussão

Conclusão

Auranofin Resistance in Toxoplasma gondii Decreases the Accumulation of Reactive Oxygen Species but Does Not Target Parasite Thioredoxin Reductase

Auranofin, a reprofiled FDA-approved drug originally designed to treat rheumatoid arthritis, has emerged as a promising anti-parasitic drug. It induces the accumulation of reactive oxygen species (ROS) in parasites, including Toxoplasma gondii. We generated auranofin resistant T. gondii lines through chemical mutagenesis to identify the molecular target of this drug. Resistant clones were confirmed with a competition assay using wild-type T. gondii expressing yellow fluorescence protein (YFP) as a reference strain. The predicted auranofin target, thioredoxin reductase, was not mutated in any of our resistant lines. Subsequent whole genomic sequencing analysis (WGS) did not reveal a consensus resistance locus, although many have point mutations in genes encoding redox-relevant proteins such as superoxide dismutase (TgSOD2) and ribonucleotide reductase. We investigated the SOD2 L201P mutation and found that it was not sufficient to confer resistance when introduced into wild-type parasites. Resistant clones accumulated less ROS than their wild type counterparts. Our results demonstrate that resistance to auranofin in T. gondii enhances its ability to abate oxidative stress through diverse mechanisms. This evidence supports a hypothesized mechanism of auranofin anti-parasitic activity as disruption of redox homeostasis.

Two key cathepsins, TgCPB and TgCPL, are targeted by the vinyl sulfone inhibitor K11777 in in vitro and in vivo models of toxoplasmosis

Although toxoplasmosis is one of the most common parasitic infections worldwide, therapeutic options remain limited. Cathepsins, proteases that play key roles in the pathogenesis of toxoplasmosis and many other protozoan infections, are important potential therapeutic targets. Because both TgCPB and TgCPL play a role in T. gondii invasion, we evaluated the efficacy of the potent, irreversible vinyl sulfone inhibitor, K11777 (N-methyl-piperazine-Phe-homoPhe-vinylsulfone-phenyl). The inhibitor’s toxicity and pharmacokinetic profile have been well-studied because of its in vitro and in vivo activity against a number of parasites. We found that it inhibited both TgCPB (EC50 = 114 nM) and TgCPL (EC50 = 71 nM) in vitro. K11777 also inhibited invasion of human fibroblasts by RH tachyzoites by 71% (p = 0.003) and intracellular replication by >99% (p<0.0001). In vivo, a single dose of K11777 led to 100% survival of chicken embryos in an model of acute toxoplasmosis (p = 0.015 Cox regression analysis). Therefore, K11777 shows promise as a novel therapeutic agent in the treatment of toxoplasmosis, and may prove to be a broadly effective anti-parasitic agent.

Avaliação da Bromelina na Interface Adesiva Afetada por S.mutans

Este estudo avaliou a influência das propriedades antimicrobianas da bromelina contra microrganismos do biofilme oral (S. mutans) nos processos de resistência de união UTBS associada ao sistema adesivo Adper Single Bond 2 (SB). A atividade da bromelina como tratamento da superfície dentinária foi avaliada através do uso de soluções de 0,5% e 1% de bromelina como tratamento, associado ao condicionamento ácido. Os resultados foram comparados aos grupos sem tratamento da superfície dentinária (controle negativo) e aos grupos desproteinizados com hipoclorito de sódio a 10% (controle positivo). Nesta etapa foram utilizados 32 incisivos bovinos, que tiveram a dentina exposta. Restaurações com os tratamentos de superfície específicos, sistema adesivo e compósito foram confeccionadas. Em seguida, os conjuntos dente/restauração foram fatiados até a obtenção de palitos, que foram armazenados em água destilada por períodos de 24 horas ou imersos por 48h em solução com S. mutans. Após o período de imersão, foi realizado o ensaio de microtração. No teste de resistência de união, após 24h de estocagem, os tratamentos com as soluções de bromelina e NaOCl10% não apresentaram diferença estatística em relação ao grupo controle SB. Em relação às suas propriedades antimicrobianas, a bromelina 1% foi estatisticamente superior aos demais grupos após a submissão ao biofilme. O resultado obtido indica a bromelina como um material promissor para oferecer um melhor desempenho dos sistemas adesivos, permitindo a redução do desenvolvimento de cáries secundárias nas margens de restaurações.Palavras-chave: Adesão. Bromelina. Antimicrobiana.

Prediction of disease severity in neuromyelitis optica by the levels of interleukin (IL)-6 produced during remission phase

T helper type 17 (Th17) cytokines have been implicated in the pathogenesis of neuromyelitis optica (NMO). As humanized anti-interleukin (IL)-6R (tocilizumab) immunoglobulin (Ig)G has been used as disease-modifying therapy for NMO, the objective of our study was to investigate the role of endogenous IL-6 on NMO-derived CD4(+) T cell behaviour. High production of IL-6, IL-17 and IL-21 by CD4(+) T-cells was detected in NMO patients. Further, IL-21 and IL-6 levels were related directly to the level of neurological disabilities. The addition of anti-IL-6R IgG not only reduced directly the production of these cytokines, but also almost abolished the ability of activated autologous monocytes in enhancing IL-6, IL-17 and IL-21 release by CD4(+) T cells. In contrast, the production of IL-10 was amplified in those cell cultures. Further, anti-IL-6R monoclonal antibodies (mAb) also potentiated the ability of glucocorticoid in reducing Th17 cytokines. Finally, the in-vivo and in-vitro IL-6 levels were significantly higher among those patients who experienced clinical relapse during 2-year follow-up. In summary, our results suggest a deleterious role of IL-6 in NMO by favouring, at least in part, the expansion of corticoid-resistant Th17 cells.

New drug target in protozoan parasites: the role of thioredoxin reductase

Amebiasis causes approximately 70,000 deaths annually and is the third cause of death due to parasites worldwide. It is treated primarily with metronidazole, which has adverse side effects, is mutagenic and carcinogenic, and emergence of resistance is an increasing concern. Unfortunately, better therapeutic alternatives are lacking. Re-purposing of older FDA approved drugs is advantageous to drug discovery since safety and pharmacokinetic effects in humans are already known. In high throughput screening studies, we recently demonstrated that auranofin, a gold containing compound originally approved to treat rheumatoid arthritis, has activity against trophozoites of E. histolytica, the causative agent of amebiasis. Auranofin's anti-parasitic activity is attributed to its monovalent gold molecule that readily inhibits E. histolytica thioredoxin reductase. This anti-oxidant enzyme is the only thiol-dependent flavo-reductase present in E. histolytica. Auranofin has also shown promising activity against other protozoans of significant public health importance. Altogether, this evidence suggests that auranofin has the potential to become a broad spectrum alternative therapeutic agent for diseases with a large global burden.

Acute HIV infection presenting as fulminant meningoencephalitis with massive CSF viral replication

A 22-year-old man presented to the emergency department with 10 days of malaise, generalized rash, sore throat, oral ulcers, headache, nausea, and vomiting. On examination he had fever (101.5°F), hepatosplenomegaly, generalized maculopapular rash, and lymphadenopathy. He rapidly became obtunded, requiring intubation. Initial laboratory studies showed mild transaminitis, increased lactate dehydrogenase, and 4,600 leukocytes per μL with 61% bands and 18% lymphocytes. Bacterial and fungal blood cultures were negative as well as a rapid HIV test, additional serologies (including rapid plasma reagin and Treponema pallidum particle agglutination), quantitative PCRs (for viruses other than HIV), and urine and blood toxicology. CSF, on hospital day 4, showed a lymphocytic pleocytosis (total leukocytes: 100), high protein, borderline hypoglycorrhachia, and negative Gram stain and culture. Brain MRI revealed no meningeal enhancement or masses. EEG revealed no epileptiform activity. Flow cytometry on bone marrow biopsy and CSF found no evidence of malignancy; neither did an excisional lymph node biopsy (figure 1). An immunofluorescent assay test for HIV returned inconclusive and a Western blot detected HIV gp120/gp160 bands. Quantitative HIV RNA PCR was 1.4 × 10⁶ copies/mL in plasma and in CSF exceeded the upper limit of quantitation (10⁷ copies/mL) (figure 2).

HIV-1 inhibits autophagy in bystander macrophage/monocytic cells through Src-Akt and STAT3

Autophagy is a homeostatic mechanism of lysosomal degradation. Defective autophagy has been linked to various disorders such as impaired control of pathogens and neurodegeneration. Autophagy is regulated by a complex array of signaling pathways that act upstream of autophagy proteins. Little is known about the role of altered regulatory signaling in disorders associated with defective autophagy. In particular, it is not known if pathogens inhibit autophagy by modulation of upstream regulatory pathways. Cells infected with HIV-1 blocked rapamycin-induced autophagy and CD40-induced autophagic killing of Toxoplasma gondii in bystander (non-HIV-1 infected) macrophage/monocytic cells. Blockade of autophagy was dependent on Src-Akt and STAT3 triggered by HIV-1 Tat and IL-10. Neutralization of the upstream receptors VEGFR, beta-integrin or CXCR4, as well as of HIV-1 Tat or IL-10 restored autophagy in macrophage/monocytic cells exposed to HIV-1-infected cells. Defective autophagic killing of T. gondii was detected in monocyte-derived macrophages from a subset of HIV-1(+) patients. This defect was also reverted by neutralization of Tat or IL-10. These studies revealed that a pathogen can impair autophagy in non-infected cells by activating counter-regulatory pathways. The fact that pharmacologic manipulation of cell signaling restored autophagy in cells exposed to HIV-1-infected cells raises the possibility of therapeutic manipulation of cell signaling to restore autophagy in HIV-1 infection.

Seizures in patients with systemic lupus erythematosus: data from LUMINA, a multiethnic cohort (LUMINA LIV)

OBJECTIVE

To examine the predictors of time-to-seizure occurrence and their impact on damage accrual and mortality in LUMINA, a multiethnic (Hispanic, African American and Caucasian) cohort of patients with systemic lupus erythematosus.

METHODS

Seizures were defined as per the American College of Rheumatology (ARC) nomenclature and case definitions for neuropsychiatric lupus syndromes. Factors associated with time-to-seizure occurrence occurring at or after diagnosis (TD) of systemic lupus erythematosus were examined by univariable and multivariable Cox proportional hazard regression analyses. The impact of seizures on damage accrual and mortality was also examined by multivariable analyses after adjusting for variables known to affect these outcomes.

RESULTS

A total of 600 patients were included in these analyses. Of them, 40 (6.7%) developed seizures at or after TD; by multivariable analyses, disease activity and younger age were independent predictors of a shorter time-to-seizure occurrence (HR = 1.10 and 1.04; 95% CI 1.04 to 1.15 and 1.00 to 1.08, p = 0.0004 and 0.0304, respectively) whereas mucocutaneous involvement (HR = 0.34, 95% CI 0.16 to 0.41, p = 0.0039) and hydroxychloroquine use (HR = 0.35, 95% CI 0.15 to 0.80, p = 0.0131) were independent predictors of a longer time-to-seizure occurrence. Seizures were an independent contributor to damage accrual but not to mortality.

CONCLUSIONS

Seizures tend to occur early in the course of systemic lupus erythematosus, and contribute to damage accrual. Younger age and disease activity are independent predictors of a shorter time-to-seizure occurrence; antimalarials appear to have a protective role in seizure occurrence.

CD40-TRAF6 and autophagy-dependent anti-microbial activity in macrophages

A fundamental question in host-pathogen interaction is to determine if the immune system activates fusion with the lysosomes to eradicate pathogens. We recently reported that this task is accomplished by the interaction between CD40 expressed on macrophages and CD154 expressed on activated CD4+ T cells. CD40 stimulation of macrophages induces vacuole-lysosome fusion through autophagy and results in killing of the obligate intracellular pathogen Toxoplasma gondii. This response is independent of IFN-gamma, STAT1 and p47 GTPases. We now report that vacuole-lysosome fusion is dependent on synergy between TRAF6 signaling downstream of CD40 and TNF-alpha. These studies identified a new paradigm by which T cells eradicate an intracellular pathogen within macrophages.

Systemic lupus erythematosus in a multiethnic US cohort: XLIII. The significance of thrombocytopenia as a prognostic factor

OBJECTIVE

To examine the clinical correlates of thrombocytopenia and the value of thrombocytopenia as a predictor of disease activity, damage accrual, and mortality in patients with systemic lupus erythematosus (SLE).

METHODS

SLE patients participating in a longitudinal multiethnic cohort were studied. Thrombocytopenia was defined as a platelet count <100,000/mm(3) at or before enrollment (baseline). Patients were categorized by the presence and absence of thrombocytopenia. The impact of thrombocytopenia as well as severe thrombocytopenia (platelet count <50,000/mm(3)) on disease activity, damage accrual, and mortality was examined by multivariable analyses.

RESULTS

A total of 616 patients were studied; 121 of the patients (20%) had thrombocytopenia, of whom 30 had severe thrombocytopenia. By univariable analyses, those with thrombocytopenia had more pulmonary, neurologic, renal, and hematologic involvement, worse disease activity and damage, and higher mortality rates. By multivariable analyses, thrombocytopenia was associated with higher disease activity over the disease course (P = 0.018), but not with the accrual of damage either at baseline (P = 0.543) or at the last visit (P = 0.086); however, severe thrombocytopenia was associated with damage accrual at the last visit (P = 0.020). When poverty was not included in the models, thrombocytopenia (<100,000/mm(3) or <50,000/mm(3)) was strongly associated with mortality (P < 0.001 for each comparison); however, the level of significance decreased some when poverty was included in the models.

CONCLUSION

Thrombocytopenia early in the course of SLE is indicative of more severe and active disease. Severe thrombocytopenia is an independent predictor of damage accrual at the last visit. Thrombocytopenia is also an independent predictor of mortality, albeit of a lesser magnitude than that predicted by poverty. Patients with thrombocytopenia need close monitoring for possible undesirable outcomes.

Accelerated damage accrual among men with systemic lupus erythematosus: XLIV. Results from a multiethnic US cohort

OBJECTIVE

To determine the impact of the patient's sex on the manifestations and outcome of systemic lupus erythematosus (SLE).

METHODS

We studied SLE patients who were ages 16 years or older and had a disease duration of < or =5 years at the time of enrollment in the LUpus in MInorities, NAture versus nurture cohort, a multiethnic cohort consisting of Hispanic, African American, and Caucasian patients. Socioeconomic/demographic, clinical, and serologic features, as well as disease activity (by the Systemic Lupus Activity Measure, Revised) and damage accrual (by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index) were compared between male and female patient groups. Multivariable analyses using male sex and damage accrual as dependent variables were then performed.

RESULTS

Sixty-three male SLE patients (10.2%) from all ethnic groups were included. The mean ages of the male and female patients were comparable. Factors that were either more frequent or tended to be more frequent among male SLE patients were Caucasian ethnicity, smoking, alcohol use, lupus anticoagulant (LAC) positivity, and renal involvement, whereas musculoskeletal involvement was less common. American College of Rheumatology criteria accrual time and disease duration were shorter in the male patients; damage was more common and of higher magnitude in this group. LAC positivity, shorter disease duration, and higher early damage scores were independently associated with male SLE. Male sex was a strong predictor of baseline damage, measured as a categorical variable (t-test = 2.357, beta-standardized coefficient 0.113; P = 0.019) or a continuous variable (hazard ratio 3.179 [95% confidence interval 1.999-5.056]; P < 0.001). Male sex was also positively associated with the development of damage over most of the course of the disease.

CONCLUSION

Poorer long-term prognosis among men with SLE appears to be decisively determined by their accelerated development of damage, particularly early in the course of the disease.

CD40 induces macrophage anti-Toxoplasma gondii activity by triggering autophagy-dependent fusion of pathogen-containing vacuoles and lysosomes

Many intracellular pathogens, including Toxoplasma gondii, survive within macrophages by residing in vacuoles that avoid fusion with lysosomes. It is important to determine whether cell-mediated immunity can trigger macrophage antimicrobial activity by rerouting these vacuoles to lysosomes. We report that CD40 stimulation of human and mouse macrophages infected with T. gondii resulted in fusion of parasitophorous vacuoles and late endosomes/lysosomes. Vacuole/lysosome fusion took place even when CD40 was ligated after the formation of parasitophorous vacuoles. Genetic and pharmacological approaches that impaired phosphoinositide-3-class 3 (PIK3C3), Rab7, vacuolar ATPase, and lysosomal enzymes revealed that vacuole/lysosome fusion mediated antimicrobial activity induced by CD40. Ligation of CD40 caused colocalization of parasitophorous vacuoles and LC3, a marker of autophagy, which is a process that controls lysosomal degradation. Vacuole/lysosome fusion and antimicrobial activity were shown to be dependent on autophagy. Thus, cell-mediated immunity through CD40 stimulation can reroute an intracellular pathogen to the lysosomal compartment, resulting in macrophage antimicrobial activity.

Predictors of post-partum damage accrual in systemic lupus erythematosus: data from LUMINA, a multiethnic US cohort (XXXVIII)

OBJECTIVE

To determine the impact of pregnancy on systemic lupus erythematosus (SLE) outcome.

METHODS

SLE patients, age >or=16 yrs, disease duration <or=5 yrs at enrolment in LUMINA, a multiethnic cohort (Hispanics, African-Americans and Caucasians), were studied. The first pregnancy after SLE diagnosis was examined. A good pregnancy outcome was a full-term delivery; an adverse outcome was a miscarriage, abortion, premature birth or stillbirth. Dependent variables were disease activity (Systemic Lupus Activity Measure-Revised, SLAM-R) and damage accrual [Systemic Lupus International Collaborating Clinics (SLICC) Damage Index, SDI]. Differences in these variables between the visit immediately prior to, and the first visit after, pregnancy and their relationship with pregnancy outcome were examined. Damage accrual due to pregnancy exposure was examined by a case-crossover design.

RESULTS

Sixty-three SLE women from all ethnic groups were included. The mean (S.D.) age and disease duration at pregnancy outcome were 27.6 (6.5) yrs and 18.3 (22.5) months, respectively. Adverse pregnancy outcomes occurred in 76.2% women. The SLAM-R and SDI scores were statistically different after pregnancy (P = 0.050 and P < 0.001, respectively); the SDI score was independent of pregnancy outcome but strongly associated with pregnancy duration (P = 0.006), disease activity (P = 0.001), damage prior to pregnancy (P < 0.001) and total disease duration (P = 0.039) by multivariable analyses. Exposure to pregnancy itself did not impact on damage accrual in the case-crossover analyses of 142 patients (17 pregnancy exposures) (OR = 1.25; 95% CI 0.336-4.655; P = 0.480).

CONCLUSIONS

Pregnancy duration, total disease duration, disease activity and damage immediately prior to pregnancy decisively impact on damage accrual after pregnancy in patients with SLE.

TNF receptor-associated factor 6-dependent CD40 signaling primes macrophages to acquire antimicrobial activity in response to TNF-alpha

IFN-gamma is considered an essential stimulus that allows macrophages to acquire activity against intracellular pathogens in response to a second signal such as TNF-alpha. However, protection against important pathogens can take place in the absence of IFN-gamma through mechanisms that are still dependent on TNF-alpha. Engagement of CD40 modulates antimicrobial activity in macrophages. However, it is not known whether CD40 can replace IFN-gamma as priming signal for induction of this response. We show that CD40 primes mouse macrophages to acquire antimicrobial activity in response to TNF-alpha. The effect of CD40 was not caused by modulation of IL-10 and TGF-beta production or TNFR expression and did not require IFN-alphabeta signaling. Induction of antimicrobial activity required cooperation between TNFR-associated factor 6-dependent CD40 signaling and TNFR2. These results support a paradigm where TNFR-associated factor 6 signaling downstream of CD40 alters the pattern of response of macrophages to TNF-alpha leading to induction of antimicrobial activity.

CD40 signaling in macrophages induces activity against an intracellular pathogen independently of gamma interferon and reactive nitrogen intermediates

Gamma interferon (IFN-gamma) is the major inducer of classical activation of macrophages. Classically activated mouse macrophages acquire antimicrobial activity that is largely dependent on the production of reactive nitrogen intermediates. However, protection against important intracellular pathogens can take place in the absence of IFN-gamma and nitric oxide synthase 2 (NOS2). Using Toxoplasma gondii as a model, we investigated if CD40 signaling generates mouse macrophages with effector function against an intracellular pathogen despite the absence of priming with IFN-gamma and lack of production of reactive nitrogen intermediates. CD40-stimulated macrophages acquired anti-T. gondii activity that was not inhibited by a neutralizing anti-IFN-gamma monoclonal antibody but was ablated by the neutralization of tumor necrosis factor alpha (TNF-alpha). Moreover, while the induction of anti-T. gondii activity in response to CD40 stimulation was unimpaired in macrophages from IFN-gamma(-/-) mice, macrophages from TNF receptor 1/2(-/-) mice failed to respond to CD40 engagement. In contrast to IFN-gamma-lipopolysaccharide, CD40 stimulation did not induce NOS2 expression and did not trigger production of reactive nitrogen intermediates. Neither N(G)-monomethyl-l-arginine nor diphenyleneiodonium chloride affected the induction of anti-T. gondii activity in response to CD40. Finally, macrophages from NOS2(-/-) mice acquired anti-T. gondii activity in response to CD40 stimulation that was similar to that of macrophages from wild-type mice. These results demonstrate that CD40 induces the antimicrobial activity of macrophages against an intracellular pathogen despite the lack of two central features of classically activated macrophages: priming with IFN-gamma and production of reactive nitrogen intermediates.

Pathogen‐Specific Induction of CD154 Is Impaired in CD4+T Cells from Human Immunodeficiency Virus–Infected Patients

The pathogenesis of immunodeficiency associated with human immunodeficiency virus (HIV) infection remains incompletely understood. CD154, a molecule that is expressed primarily on activated CD4(+) T cells, is pivotal for regulation of cell-mediated and humoral immunity and is crucial for control of many opportunistic infections. We investigated whether CD4(+) T cells from HIV-infected patients exhibit defective induction of CD154 in response to opportunistic pathogens. Incubation of purified human CD4(+) T cells with monocytes plus antigenic preparations of either Candida albicans, cytomegalovirus, or Toxoplasma gondii resulted in induction of CD154. Expression of CD154 in response to these pathogens was impaired in CD4(+) T cells from HIV-infected patients. This defect correlated with decreased production of interleukin (IL)-12 and interferon (IFN)-gamma in response to T. gondii. Recombinant CD154 partially restored secretion of IL-12 and IFN-gamma in response to T. gondii in cells from HIV-infected patients. Together, defective induction of CD154 is likely to contribute to impaired cell-mediated immunity against opportunistic pathogens in HIV-infected patients.

CD154 Activates Macrophage Antimicrobial Activity in the Absence of IFN-γ through a TNF-α-Dependent Mechanism

Protection against certain intracellular pathogens can take place in the absence of IFN-gamma through mechanisms dependent on TNF-alpha. In this regard, patients with partial defect in IFN-gamma receptor 1 are not susceptible to toxoplasmosis. Thus, we used a model of Toxoplasma gondii infection to investigate whether CD154 modulates IFN-gamma-independent mechanisms of host protection. Human monocyte-derived macrophages treated with recombinant CD154 exhibited increased anti-T. gondii activity. The number of tachyzoites per 100 macrophages at 20 h postinfection was lower in CD154-treated macrophages compared with controls. This was accompanied by a decrease in the percentage of infected cells in CD154-treated macrophages at 20 h compared with 1 h postinfection. CD154-bearing cells also induced antimicrobial activity in T. gondii-infected macrophages. CD154 enhanced macrophage anti-T. gondii activity independently of IFN-gamma. TNF-alpha mediated the effects of CD154 on macrophage anti-T. gondii activity. CD154 increased TNF-alpha production by T. gondii-infected macrophages, and neutralization of TNF-alpha inhibited the effect of CD154 on macrophage anti-T. gondii activity. These results demonstrate that CD154 triggers TNF-alpha-dependent antimicrobial activity in macrophages and suggest that CD154 regulates the mechanisms of host protection that take place when IFN-gamma signaling is deficient.

Antioxidant responses in bean (Phaseolus vulgaris) roots colonized by arbuscular mycorrhizal fungi

•  Degradation of reactive oxygen species in arbuscular mycorrhizas (AM) may be an efficient mechanism to attenuate the activation of plant defenses. Here, we evaluated the activities of superoxide dismutase (SOD), guaiacol-peroxidase (GPX) and catalase (CAT) in bean (Phaseolus vulgaris) mycorrhizal roots at different conditions and stages of symbiosis development. •  Bean plants were inoculated with Glomus clarum (Gc) or G. intraradices (Gi), under low (LP) and high P (HP) concentrations, and grown under glasshouse conditions. In a second experiment, bean seeds were treated with formononetin and inoculated with Gc under LP and HP conditions. The activities of SOD, GPX and CAT were evaluated. •  SOD was induced only in roots colonized by Gc, at a late stage of the symbiosis development under LP, and at an early stage under HP. GPX was induced in roots colonized by Gc at an early time point and suppressed later under LP. In general, CAT was induced in roots colonized by Gc under LP. CAT activities in roots were dependent on P and formononetin treatment. •  The possible roles of SOD, GPX and CAT in AM are discussed.

The capsular polysaccharides of Cryptococcus neoformans activate normal CD4(+) T cells in a dominant Th2 pattern

Capsular components of Cryptococcus neoformans induce several deleterious effects on T cells. However, it is unknown how the capsular components act on these lymphocytes. The present study characterized cellular and molecular events involved in immunoregulation of splenic CD4(+) T cells by C. neoformans capsular polysaccharides (CPSs). The results showed that CPSs induce proliferation of normal splenic CD4(+) T cells, but not of normal CD8(+) T or B lymphocytes. Such proliferation depended on physical contact between CPSs and viable splenic adherent cells (SAC) and CD40 ligand-induced intracellular signal transduction. The absence of lymphoproliferation after fixation of SAC with paraformaldehyde has discarded the hypothesis of a superantigen-like activation. The evaluation of a cytokine pattern produced by the responding CD4(+) T lymphocytes revealed that CPSs induce a dominant Th2 pattern, with high levels of IL-4 and IL-10 production and undetectable inflammatory cytokines, such as TNF-alpha and IFN-gamma. Blockade of CD40 ligand by relevant mAb down-regulated the CPS-induced anti-inflammatory cytokine production and abolished the enhancement of fungus growth in cocultures of SAC and CD4(+) T lymphocytes. Our findings suggest that CPSs induce proliferation and differentiation of normal CD4(+) T cells into a Th2 phenotype, which could favor parasite growth and thus important deleterious effects to the host.

Activation-induced T cell death exacerbates Trypanosoma cruzi replication in macrophages cocultured with CD4+ T lymphocytes from infected hosts

Activation-induced cell death (AICD) of CD4+ T lymphocytes was described in infection with Trypanosoma cruzi, but a role for AICD in modulating parasite spread in host cells has not been investigated. In this study, replication of T. cruzi in vitro in murine macrophage (Mphi) monolayers was investigated. Long term (5 to 13 day) replication of infective (trypomastigote) T. cruzi forms was blocked by supernatants from activated (anti-TCR) CD4+ T cells of infected mice or by rIFN-gamma. However, when CD4+ T cells from infected mice were cocultured with Mphi and activated by anti-TCR, marked exacerbation of trypomastigote growth in Mphi ensued. The deleterious effect required contact between T cells and infected Mphi. Both anti-Fas and TCR activation killed a proportion of CD4+ T cells. Ly-6 activation did not induce AICD and did not exacerbate parasite growth. However, Fas-mediated killing of T cells before Ly-6 activation led to exacerbated parasite growth. Although a minor population, Fas-susceptible cells were the major source of IFN-gamma production by activated T cells. Addition of a neutralizing anti-Fas ligand antibody blocked 50 to 60% of CD4+ T cell AICD and reduced trypomastigote growth in T/Mphi cocultures stimulated by anti-TCR. The results demonstrate that in CD4+ T cells from infected mice, the onset of AICD selectively ablates IFN-gamma production and up-regulates parasite replication in Mphi in vitro. These findings suggest a deleterious role for AICD in T. cruzi infection.