Ocular toxoplasmosis in patients with the acquired immunodeficiency syndrome

Long-Term Low-Dose Pyrimethamine Use for the Prevention of Ocular Toxoplasmosis Recurrences: A Cohort Study

PURPOSE

To describe the effect of long-term, low-dose pyrimethamine for the prevention of ocular toxoplasmosis (OT) recurrences.

METHODS

Sixty-three consecutive patients with inactive ocular toxoplasmosis and positive toxoplasma IgG serology were included. Pyrimethamine (25 mg) + folinic acid (15 mg) were administered every other day (three times weekly) for 12 months. Eighteen patients received the treatment for an additional six months as part of an extension study.

RESULTS

Thirty-eight patients (60.3%, n = 63) were female; 38 (60.3%) had a previous history of recurrence and 37 (58.7%) had active OT within the preceding 12 months. Three (4.8%) patients had unilateral recurrences at 8, 12 and 18 months after starting intermittent pyrimethamine treatment. Five patients (7.9%) were discontinued due to hematological, renal and hepatic changes. Treatment was considered successful in 42 patients (84%).

CONCLUSION

Long-term, low-dose pyrimethamine can be considered as a treatment option for the prevention of ocular toxoplasmosis recurrence in selected patients, with only a few, mild and reversible systemic adverse events.

The Role of Corticosteroids and Immunomodulatory Therapy in the Management of Infectious Uveitis

PURPOSE

The index review aims to provide an update on the role of corticosteroids and steroid-sparing immunomodulatory therapy (IMT) in managing patients with infectious uveitis.

METHOD

Narrative literature review.

RESULTS

Corticosteroids and immunomodulatory therapy (IMT) focus on the host defense system instead of the pathogen, adjusting exaggerated inflammatory reactions to reduce potential harm to ocular tissues. Systemic or local corticosteroids are primarily selected as adjunctive medication for infectious uveitis. Concomitant corticosteroids have also been used in cases of paradoxical worsening in ocular tuberculosis and immune recovery uveitis in cytomegalovirus (CMV) retinitis. While there is no well-established evidence to support the use of IMT in infectious uveitis, it is occasionally used in clinical settings to treat persistent inflammation following resolution of infection such as cases of ocular tuberculosis and ocular syphilis where an insufficient response is observed with corticosteroids.

CONCLUSION

There is no consensus on the position of immunomodulatory therapy in the management of infectious uveitis with different etiologies. The index review provides an overview of available adjunctive corticosteroids and IMT options to assist clinicians in managing such disease entities more efficiently.

Association Between Ocular Trauma and Activation of Ocular Toxoplasmosis

PURPOSE

To evaluate the association between ocular trauma and activation of ocular toxoplasmosis.

METHODS

Retrospective review of 686 patients with ocular toxoplasmosis and its association with trauma to the eye or the head within 1 week of activation.

RESULTS

Ten patients with a history of trauma and activation of ocular toxoplasmosis were detected (10/686; 1.45%). Nine patients showed a primary focus of retinitis without a previous scar and one patient had a recurrent form of ocular toxoplasmosis. From these 10 patients, Toxoplasma IgG was positive in eight of them. The median age of the patients was 35.8 years-old (range 17 to 65).

CONCLUSIONS

These cases suggest that trauma can be associated with activation of retinal bradyzoite cysts in ocular toxoplasmosis.

Effective factors in the pathogenesis of Toxoplasmagondii

Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite in humans and animals. It infects about 30 % of the human population worldwide and causes potentially fatal diseases in immunocompromised hosts and neonates. For this study, five English-language databases (ScienceDirect, ProQuest, Web of Science, PubMed, and Scopus) and the internet search engine Google Scholar were searched. This review was accomplished to draw a global perspective of what is known about the pathogenesis of T. gondii and various factors affecting it. Virulence and immune responses can influence the mechanisms of parasite pathogenesis and these factors are in turn influenced by other factors. In addition to the host's genetic background, the type of Toxoplasma strain, the routes of transmission of infection, the number of passages, and different phases of parasite life affect virulence. The identification of virulence factors of the parasite could provide promising insights into the pathogenesis of this parasite. The results of this study can be an incentive to conduct more intensive research to design and develop new anti-Toxoplasma agents (drugs and vaccines) to treat or prevent this infection. In addition, further studies are needed to better understand the key agents in the pathogenesis of T. gondii.

Active toxoplasma chorioretinitis in immunocompromised patients: a case series

Toxoplasma chorioretinitis (TC) can exhibit atypical features in immunocompromised patients including bilaterality, extensive spread, multifocal presentation, large areas of retinal necrosis without adjacent retinal scarring, and diffuse necrotizing retinitis resembling the viral retinitis that may cause confusion in the differential diagnosis. The aim of this study was to present the clinical features of four eyes of three immunocompromised patients with active toxoplasma chorioretinitis. Two of the patients were female and one, male. Two patients had hematological malignancies and the remaining patient was under adalimumab treatment for ankylosing spondylitis. Visual complaints began 10 days to four months prior to TC diagnosis. All four eyes had mild-to-moderate anterior chamber cells together with severe vitritis on slit-lamp examination while there were solitary chorioretinitis lesions on fundoscopy. Despite all patients were negative for anti-toxoplasma immunoglobulin M, all were positive for immunoglobulin G. All three patients were successfully treated with a combined treatment of systemic and intravitreal anti-toxoplasmic drugs. Clinicians should be cautious for the possible toxoplasma chorioretinitis besides the other infectious entities when a new uveitis episode is detected in an immunosuppressed patient in order to avoid misdiagnosis and thereby wrong treatment.

Ocular Toxoplasmosis

INTRODUCTION

Ocular toxoplasmosis is the leading cause of posterior uveitis worldwide, affecting individuals acrossdifferent age groups. The key to reducing vision loss includes prompt diagnosis and treatment. However, despite the prevalence of ocular toxoplasmosis, there has been little consensus regarding its pathophysiology,clinical features, diagnosis, and especially management.

METHODS

The data sources were literature reviews, including Pub Med and Medline databases. Search terms included toxoplasmosis, retinitis, vasculitis, vitritis, uveitis alone or in combination with, serum, aqueous, vitreous eye, ocular and review.

RESULTS

In this review paper, we have sought to provide an overview of the pathophysiology, epidemiology, and clinical features of the disease, both based on current literature and our own clinical experience. We have also discussed the use of serology, ocular fluid, and ophthalmic investigations that could further facilitate the diagnosis of ocular toxoplasmosis.Different management strategies have been reported worldwide, including newer approaches such as local therapy.

CONCLUSION

A better understanding of critical aspects of ocular toxoplasmosis will hopefully lead to reduced morbidity, including blindness associated with this condition.

Association of Proton Pump Inhibitor/Histamine-2 Blocker Use and Ocular Toxoplasmosis: Findings from a Large US National Database

OBJECTIVE

To test the hypothesis that the use of proton pump inhibitors (PPIs) is associated with an increased risk of being diagnosed with toxoplasmic retinochoroiditis.

DESIGN

Retrospective, matched case-control study using data from 2000 to 2020.

PARTICIPANTS

Patients with ocular toxoplasmosis and controls were matched 5:1 for age, sex, and race, with the eligibility date ± 3 months from the index date of exposed match. Patients aged < 18 years with congenital toxoplasmosis, having < 2 years in the insurance plan before the index date, and without ≥ 1 visit to an eyecare provider before the index date were excluded from the study.

METHODS

Patients with ocular toxoplasmosis were identified using the International Classification of Diseases, Ninth Revision and International Classification of Diseases, Tenth Revision codes, and PPI use or diseases highly associated with PPIs were identified using national drug codes from an administrative medical claims database.

MAIN OUTCOME MEASURES

The primary outcome was defined as having a prescription for a PPI or histamine-2 (H2) blocker. Multivariable logistic regression analyses were performed, controlling for demographic and systemic health variables.

RESULTS

A total of 4069 cases and 19 177 controls met the eligibility criteria. Of the 4069 patients with ocular toxoplasmosis, 989 (24.3%) were on PPI/H2 blockers compared with 3763 of 19 177 (19.2%) controls. The adjusted logistic regression model demonstrated 1.28 greater odds of PPI/H2 blocker use in cases of ocular toxoplasmosis than matched controls (95% confidence interval, 1.17-1.40; P < 0.001).

CONCLUSIONS

Proton pump inhibitor/H2 blocker exposure was associated with an increased risk of being diagnosed with ocular toxoplasmosis, corroborating findings from a prior case series.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Posterior segment findings by spectral-domain optical coherence tomography and clinical associations in active toxoplasmic retinochoroiditis

Toxoplasmic retinochoroiditis is a common, potentially blinding parasitic infection. We sought to define the spectrum and frequency of signs of active toxoplasmic retinochoroiditis by spectral domain optical coherence tomography (SD-OCT), and to identify clinical associations. Ninety eyes of 90 individuals presenting consecutively to a tertiary referral uveitis service with active toxoplasmic retinochoroiditis and gradable SD-OCT scans were evaluated prospectively. SD-OCT features were collated, and associations with lesion location, primary versus recurrent episode, serological status, human immunodeficiency virus infection and best-corrected Snellen visual acuity were explored. Active toxoplasmic retinochoroiditis presented with thickened (65%) and hyperreflective (61%) retina, choroidal thickening (55%) and hyporeflectivity (61%), hyperreflective vitreous dots (80%) and deposits (36%), and posterior hyaloid thickening (35%) on SD-OCT. Most signs occurred with similar frequency across clinical groups. Retinal hyporeflectivity (17%) was significantly associated with a visual acuity of 20/200 or worse at resolution. Our observations demonstrate that active toxoplasmic retinochoroiditis has diverse SD-OCT signs and that none are universally present. Retinal hyporeflectivity—suggesting liquefactive necrosis—predicts poor visual outcome.

Ocular toxoplasmosis: a review of the current diagnostic and therapeutic approaches

PURPOSE

This review aims to summarize the current knowledge concerning the clinical features, diagnostic work-up and therapeutic approach of ocular toxoplasmosis focusing mainly on the postnatally acquired form of the disease.

METHODS

A meticulous literature search was performed in the PubMed database. A supplementary search was made in Google Scholar to complete the collected items.

RESULTS

Ocular toxoplasmosis is one of the most frequent infectious etiologies of posterior uveitis. It typically presents with retinochoroiditis. Setting an accurate diagnosis depends to a considerable degree on detecting characteristic clinical characteristics. In addition to the evaluation of clinical features, the diagnosis of toxoplasmosis relies at a large degree on serologic testing. The detection of the parasite DNA in the aqueous or vitreous humor can provide evidence for a definitive diagnosis. The current mainstay for the treatment, if necessary, is the use of oral antibiotic with systemic corticosteroids. Recent evidence suggests other therapeutic approaches, such as intravitreal antibiotics can be used.

CONCLUSION

Recent developments in the diagnostic and therapeutic approach have contributed to preventing or limiting vision loss of patients suffering from ocular toxoplasmosis. Further studies are required to provide a better understanding of epidemiology, pathogenesis, diagnosis, and treatment with a significant impact on the management of this challenging clinical entity.

Punctate Inner Retinal Toxoplasmosis: Case Series and Review of Literature

PURPOSE

To describe clinical and multimodal imaging characteristics of punctate inner retinal toxoplasmosis (PIRT) as an atypical presentation of ocular toxoplasmosis (OT).

METHODS

Retrospective review of OT cases with PIRT lesions and review of the literature. We describe five cases (6 eyes).

RESULTS

PIRT lesions were seen adjacent to active/healed toxoplasma retinochoroiditis. The appearance of PIRT was creamy yellowish-white, inner retinal, punctate, and sub-centimetric lesions. The depth of these lesions on optical coherence tomography was till the outer plexiform layer. Co-existing punctate outer retinal toxoplasmosis (PORT) was found in three eyes and recurrent retinochoroiditis in three. The fate of PIRT was resolution with minimal retinal thinning or progression to a full-thickness retinochoroiditis.

CONCLUSION

PIRT was noted in association with typical toxoplasma retinochoroiditis and PORT lesions, and had equal chances of resolution or progression to full-thickness lesions.

Classification Criteria for Toxoplasmic Retinitis

PURPOSE

To determine classification criteria for toxoplasmic retinitis.

DESIGN

Machine learning of cases with toxoplasmic retinitis and 4 other infectious posterior uveitides / panuveitides.

METHODS

Cases of infectious posterior uveitides / panuveitides were collected in an informatics-designed preliminary database, and a final database was constructed of cases achieving supermajority agreement on diagnosis, using formal consensus techniques. Cases were split into a training set and a validation set. Machine learning using multinomial logistic regression was used on the training set to determine a parsimonious set of criteria that minimized the misclassification rate among the infectious posterior uveitides / panuveitides. The resulting criteria were evaluated on the validation set.

RESULTS

Eight hundred three cases of infectious posterior uveitides / panuveitides, including 174 cases of toxoplasmic retinitis, were evaluated by machine learning. Key criteria for toxoplasmic retinitis included focal or paucifocal necrotizing retinitis and either positive polymerase chain reaction assay for Toxoplasma gondii from an intraocular specimen or the characteristic clinical picture of a round or oval retinitis lesion proximal to a hyperpigmented and/or atrophic chorioretinal scar. Overall accuracy for infectious posterior uveitides / panuveitides was 92.1% in the training set and 93.3% (95% confidence interval 88.2, 96.3) in the validation set. The misclassification rates for toxoplasmic retinitis were 8.2% in the training set and 10% in the validation set.

CONCLUSIONS

The criteria for toxoplasmic retinitis had a low misclassification rate and seemed to perform sufficiently well for use in clinical and translational research.

Expanded Spectrum of Optical Coherence Tomography Findings in Patients with Ocular Toxoplasmosis

Purpose: To describe the optical coherence tomography (OCT) findings of toxoplasmic retinochoroiditis at different stages of activity.Methods: Observational case series.Results: A total of 32 eyes of 31 patients were included; 43 sets of OCT were reviewed. A total of 14 lesions were classified as active, 13 as partially active, and 16 as inactive. All active lesions demonstrated increased retinal thickness and reflectivity with blurring of details of retinal layers. Choroidal granuloma was detected in eight (61.5%) and serous retinal detachment in nine (64%). In partially active lesions, sustained thickening and/or attachment of posterior hyaloid face with fine epiretinal membrane was the hallmark. Scarified lesions showed decreased retinal and choroidal thickness starting from the periphery. Characteristic signs for decreased activity of a lesion seen in majority of both partially active and inactive lesions were RPE changes and retina-RPE approximation. We called this unique feature 'hourglass configuration'.Conclusion: Features in OCT are helpful to specify and monitor the activity of toxoplasmic retinochoroiditis.

Pathophysiology of ocular toxoplasmosis: Facts and open questions

Infections with the protozoan parasite Toxoplasma gondii are frequent, but one of its main consequences, ocular toxoplasmosis (OT), remains poorly understood. While its clinical description has recently attracted more attention and publications, the underlying pathophysiological mechanisms are only sparsely elucidated, which is partly due to the inherent difficulties to establish relevant animal models. Furthermore, the particularities of the ocular environment explain why the abundant knowledge on systemic toxoplasmosis cannot be just transferred to the ocular situation. However, studies undertaken in mouse models have revealed a central role of interferon gamma (IFNγ) and, more surprisingly, interleukin 17 (IL17), in ocular pathology and parasite control. These studies also show the importance of the genetic background of the infective Toxoplasma strain. Indeed, infections due to exotic strains show a completely different pathophysiology, which translates in a different clinical outcome. These elements should lead to more individualized therapy. Furthermore, the recent advance in understanding the immune response during OT paved the way to new research leads, involving immune pathways poorly studied in this particular setting, such as type I and type III interferons. In any case, deeper knowledge of the mechanisms of this pathology is needed to establish new, more targeted treatment schemes.

Clinical, Socio-economic and Environmental Factors Related with Recurrences in Ocular Toxoplasmosis in Quindío, Colombia

PURPOSE

To identify the sociodemographic, clinical, and environmental factors associated with recurrences in ocular toxoplasmosis (OT).

METHODS

Retrospective analysis of clinical records of patients who consulted in the Health Centre at Universidad del Quindío between 2004 and 2017. Patients with retinochoroiditis due to Toxoplasma gondii infection and follow up >12 months were included. Comparisons were made with a recurrence index adjusted for months of follow up. For the statistical analysis, the Kruskal-Wallis test and analysis of variance (ANOVA) tests were performed in Epi Info 7.2 and SPSS 14.0. A statistical significance is shown if p ≤ 0.05.

RESULTS

A total of 58 patients were included, with median age of 28 years (range 1-61) and 55.1% were women. The median of recurrences was 1.4 (range 0.6-16.6). High recurrence index was present in 43.1% of the patients. A higher size of lesions was observed in low socioeconomic groups (p = .016) and patients with congenital infection had more bilateral compromise (p = .002). Intake of boiled water was related to a lower recurrence index (p = .04).

CONCLUSIONS

Low socioeconomic level was associated with bigger lesions and congenital infection was related with higher frequency of bilateral OT. Finally, intake of boiled water is related to a lower recurrence index of OT.

Human immunodeficiency virus and intraocular inflammation in the era of highly active anti retroviral therapy - An update

Intraocular inflammation in patients with human immunodeficiency virus (HIV) infection is commonly due to infectious uveitis. Ocular lesions due to opportunistic infections (OI) are the most common and have been described extensively in the pre highly active antiretroviral therapy (HAART) era. Many eye lesions were classified as acquired immunodeficiency syndrome (AIDS) defining illnesses. HAART-associated improvement in immunity of the individual has changed the pattern of incidence of these hitherto reported known lesions leading to a marked reduction in the occurrence of ocular OI. Newer ocular lesions and newer ocular manifestations of known agents have been noted. Immune recovery uveitis (IRU), the new menace, which occurs as part of immune recovery inflammatory syndrome (IRIS) in the eye, can present with significant ocular inflammation and can pose a diagnostic and therapeutic challenge. Balancing the treatment of inflammation with the risk of reactivation of OI is a task by itself. Ocular involvement in the HAART era can be due to the adverse effects of some systemic drugs used in the management of HIV/AIDS. Drug-associated retinal toxicity and other ocular side effects are being increasingly reported. In this review, we discuss the ocular manifestations in HIV patients and its varied presentations following the introduction of HAART, drug-associated lesions, and the current treatment guidelines.

Pathogenesis of ocular toxoplasmosis

Ocular toxoplasmosis is a retinitis -almost always accompanied by vitritis and choroiditis- caused by intraocular infection with Toxoplasma gondii. Depending on retinal location, this condition may cause substantial vision impairment. T. gondii is an obligate intracellular protozoan parasite, with both sexual and asexual life cycles, and infection is typically contracted orally by consuming encysted bradyzoites in undercooked meat, or oocysts on unwashed garden produce or in contaminated water. Presently available anti-parasitic drugs cannot eliminate T. gondii from the body. In vitro studies using T. gondii tachyzoites, and human retinal cells and tissue have provided important insights into the pathogenesis of ocular toxoplasmosis. T. gondii may cross the vascular endothelium to access human retina by at least three routes: in leukocyte taxis; as a transmigrating tachyzoite; and after infecting endothelial cells. The parasite is capable of navigating the human neuroretina, gaining access to a range of cell populations. Retinal Müller glial cells are preferred initial host cells. T. gondii infection of the retinal pigment epithelial cells alters the secretion of growth factors and induces proliferation of adjacent uninfected epithelial cells. This increases susceptibility of the cells to parasite infection, and may be the basis of the characteristic hyperpigmented toxoplasmic retinal lesion. Infected epithelial cells also generate a vigorous immunologic response, and influence the activity of leukocytes that infiltrate the retina. A range of T. gondii genotypes are associated with human ocular toxoplasmosis, and individual immunogenetics -including polymorphisms in genes encoding innate immune receptors, human leukocyte antigens and cytokines- impacts the clinical manifestations. Research into basic pathogenic mechanisms of ocular toxoplasmosis highlights the importance of prevention and suggests new biological drug targets for established disease.

Management of Intraocular Infections in HIV

Purpose: Overview of treatment options for the most common intraocular opportunistic infections in patients with acquired immunodeficiency syndrome (AIDS), including ocular syphilis, ocular tuberculosis, toxoplasmic chorioretinitis, and viral retinitis. Method: Narrative Review. Results: Despite the huge advances in the development of combined antiretroviral therapy (cART) for the management of patients with human immunodeficiency virus (HIV) infection, opportunistic infections still represent a significant diagnostic dilemma and cause of ocular morbidity in patients with HIV. Conclusion: Although the treatment of intraocular infections in patients with AIDS may be challenging, prompt assessment of the clinical features and appropriate aggressive management of the underlying etiology are critical to avoid life and vision threatening.

Disease of the Year 2019: Ocular Toxoplasmosis in HIV-infected Patients

Ocular toxoplasmosis (OT) may be an initial manifestation of acquired immunodeficiency syndrome (AIDS) in human immunodeficiency virus (HIV)-infected patients. OT has different clinical manifestations and can mimic other intraocular infections. Clinical findings may show single or multifocal retinochoroidal lesions or panuveitis. Atypical presentations are associated with extensive uni- or bilateral areas of retinal necrosis. OT lesions not associated with preexisting retinochoroidal scars are usually due to acquired rather than congenital infection. When CD4+ T cell counts are <100 c/uL, vitritis is frequently mild. Isolated anterior uveitis has been reported in single cases. Positive immunoglobulin M (IgM) antibodies are rare but their presence can support the diagnosis. As atypical presentations of OT are common, anterior chamber puncture for multiplex polymerase chain reaction amplification of infectious DNA should be considered, as early diagnosis and treatment can prevent massive tissue destruction and preserve vision. This review provides an overview of OT in HIV-infected patients.

Challenges in Treating Intraocular Inflammation in HIV Patients

Purpose: To describe the challenges faced by uveitis specialists when managing human immunodeficiency virus (HIV) -infected patients diagnosed with ocular opportunistic infections. Methods: Narrative Review Results: Management of opportunistic ocular infections in HIV-infected subjects still represents a diagnostic and therapeutic challenge. Atypical and aggressive clinical features can often mislead the correct diagnosis, leading to a delay in therapy and thus, a poor clinical outcome. The reliability of standard serological tests may be affected by the immune system response, further contributing to the diagnostic challenge. Life-long monitoring and long-term antimicrobial maintenance are necessary to avoid recurrences and disease dissemination. Conclusions: A multidisciplinary approach is needed to achieve the best standard of care for HIV patients with ocular opportunistic infections.

Molecular Basis of The Retinal Pigment Epithelial Changes That Characterize The Ocular Lesion in Toxoplasmosis

When a person becomes infected with Toxoplasma gondii, ocular toxoplasmosis is the most common clinical presentation. The medical literature describes retinitis with surrounding hyperpigmentation secondary to proliferative changes in the retinal pigment epithelium, which is sufficiently characteristic that investigation often is not needed to make the diagnosis. We aimed to establish the frequency of “typical” ocular toxoplasmosis and delineate its molecular basis. Among 263 patients presenting consecutively with ocular toxoplasmosis to Ribeirão Preto General Hospital in Brazil, where T. gondii infection is endemic, 94.2% of 345 eyes had retinal hyperpigmentation. In ARPE-19 and primary human retinal pigment epithelial cell monolayers exposed to minimal numbers of T. gondii tachyzoites, the proliferation marker–KI-67–was increased in uninfected cells, which also were rendered more susceptible to infection. RT-qPCR and ELISA detected increased expression of vascular endothelial growth factor A (VEGF) and insulin-like growth factor (IGF)1, and decreased expression of thrombospondin (TSP)1 by infected cells. Blockade of VEGF and IGF1—or supplementation of TSP1—reversed the proliferation phenotype in uninfected cells. Our findings confirm that hyperpigmentation is a characteristic feature of retinitis in ocular toxoplasmosis, and demonstrate that T. gondii-infected human retinal pigment epithelial cells secrete VEGF and IGF1, and reduce production of TSP1, to promote proliferation of adjacent uninfected cells and create this disease-specific appearance.

Comparison of immunoblotting (IgA and IgG) and the Goldmann-Witmer coefficient for diagnosis of ocular toxoplasmosis in immunocompetent patients

BACKGROUND

Ocular toxoplasmosis (OT) is a common cause of posterior uveitis worldwide. The diagnosis of OT is based on clinical findings, but in most cases, laboratory tests are required to confirm the aetiology, especially when other diseases are suspected. The aim of this study was to evaluate which methods, between the Goldmann-Witmer coefficient (GWC) and immunoblotting (IB) with both IgG and IgA, in aqueous humour (AH) samples, can be the most sensitive to diagnose OT, in current practice, especially in the first three weeks.

METHODS

Retrospectively reviewed records of 87 consecutive patients who had underwent AH and serum sample, 42 patients with suspected OT and 45 patients with suspected other ocular inflammatory diseases. All samples were analysed by both GWC and IB.

RESULTS

The GWC was significant in 47.6% of patients presenting with suspected OT. The intraocular production of specific antibody anti-Toxoplasma gondii IgG and IgA was revealed by IB in 71.4% of samples. The combination of these two methods increased the sensitivity to 76.2%. Based on the interval between symptom onset and paracentesis, IB had a greater sensitivity than GWC when sample of AH was taken in the first three weeks (64.7% vs 23.5%, P=0.039), while the difference between the sensitivity of IB and GWC was less important in cases with an interval >3 weeks (76% vs 64% P=0.625).

CONCLUSION

IB seems to be more useful than the GWC if only one of these methods can be performed, especially during the first three weeks after symptom onset.

Experimental Toxoplasmosis in Rats Induced Orally with Eleven Strains of Toxoplasma gondii of Seven Genotypes: Tissue Tropism, Tissue Cyst Size, Neural Lesions, Tissue Cyst Rupture without Reactivation, and Ocular Lesions

BACKGROUND

The protozoan parasite Toxoplasma gondii is one of the most widely distributed and successful parasites. Toxoplasma gondii alters rodent behavior such that infected rodents reverse their fear of cat odor, and indeed are attracted rather than repelled by feline urine. The location of the parasite encysted in the brain may influence this behavior. However, most studies are based on the highly susceptible rodent, the mouse.

METHODOLOGY/PRINCIPAL FINDINGS

Latent toxoplasmosis was induced in rats (10 rats per T. gondii strains) of the same age, strain, and sex, after oral inoculation with oocysts (natural route and natural stage of infection) of 11 T. gondii strains of seven genotypes. Rats were euthanized at two months post inoculation (p.i.) to investigate whether the parasite genotype affects the distribution, location, tissue cyst size, or lesions. Tissue cysts were enumerated in different regions of the brains, both in histological sections as well in saline homogenates. Tissue cysts were found in all regions of the brain. The tissue cyst density in different brain regions varied extensively between rats with many regions highly infected in some animals. Overall, the colliculus was most highly infected although there was a large amount of variability. The cerebral cortex, thalamus, and cerebellum had higher tissue cyst densities and two strains exhibited tropism for the colliculus and olfactory bulb. Histologically, lesions were confined to the brain and eyes. Tissue cyst rupture was frequent with no clear evidence for reactivation of tachyzoites. Ocular lesions were found in 23 (25%) of 92 rat eyes at two months p.i. The predominant lesion was focal inflammation in the retina. Tissue cysts were seen in the sclera of one and in the optic nerve of two rats. The choroid was not affected. Only tissue cysts, not active tachyzoite infections, were detected. Tissue cysts were seen in histological sections of tongue of 20 rats but not in myocardium and leg muscle.

CONCLUSION/SIGNIFICANCE

This study reevaluated in depth the rat model of toxoplasmosis visualizing cyst rupture and clarified many aspects of the biology of the parasite useful for future investigations.

Ocular toxoplasmosis: background and evidence for an antibiotic prophylaxis

PURPOSE OF REVIEW

The purpose of this review was to provide an overview of current data on antibiotic prophylaxis in ocular toxoplasmosis.

RECENT FINDINGS

Studies showing the prophylactic effect of long-term antibiotics are discussed. Prophylaxis seems to be justified in patients with a high risk of recurrence because of antibiotic's potential side-effects. Therefore, predisposing factors leading to a higher risk of recurrence and the time period during which an antibiotic prophylaxis is most appropriate are reviewed. Finally, a patient-individualized treatment recommendation is summarized.

SUMMARY

In the current literature, two prospective, randomized case-control studies exist, which show the protective effect of an antibiotic prophylaxis. Hematologic, gastrointestinal and dermatologic complications are potential side-effects. Especially during the first year after suffering a recurrence, an antibiotic prophylaxis seems to be justified. The risk of a recurrence is inter alia influenced by the duration of the disease, the immune status of the host and the patient's age. Therefore, an antibiotic prophylaxis should be considered for patients who have recently been infected with ocular toxoplasmosis, for middle-aged and elderly patients and patients with a compromised immune system. This should be discussed with each patient individually, especially if the lesion is close to the macula.

Time patterns of recurrences and factors predisposing for a higher risk of recurrence of ocular toxoplasmosis

PURPOSE

To ascertain time patterns of recurrences and factors predisposing for a higher risk of recurrence of ocular toxoplasmosis.

METHODS

Retrospective observational case series with follow-up examination. Database of 4,381 patients with uveitis was used. Data of 84 patients with ocular toxoplasmosis (sample group) could be included.

RESULTS

Two hundred and eighty active lesions in the first affected eye were detected. The mean number of recurrences per year was 0.29 (standard deviation, 0.24). Median recurrence-free survival time was 2.52 years (95% confidence interval, 2.03-3.02 years). Risk of recurrence was highest in the first year after the most recent episode (26%) implying a decrease with increasing recurrence-free interval. The risk of recurrence decreased with the duration of disease (P < 0.001). Treatment of the first active lesion influenced the risk of recurrence (P = 0.048). Furthermore, the risk of recurrence was influenced by patient age at the time of the first active lesion (P = 0.021) and the most recent episode (P = 0.002).

CONCLUSION

A secondary antibiotic prophylaxis could be discussed 1) during the first year after an active lesion has occurred, especially in case of the first active lesion of ocular toxoplasmosis, and 2) in older patients, especially if primarily infected with Toxoplasma gondii at an older age.

[Extensive bilateral chorioretinitis revealing human immunodeficiency virus (HIV) infection]

Au cours de l'infection par le virus de l'immunodéficience humaine(VIH), Les atteintes oculaires sont polymorphes, pouvant compromettre le pronostic fonctionnel. Nous rapportons l'observation d'un patient présentant une choriorétinite infectieuse sévère révélant une infection par le VIH. Patient âgé de 35 ans avec antécédent de tuberculose pulmonaire en 2007, consulte pour BAV bilatérale progressive depuis 6 mois. Une acuité visuelle à compte les doigts au niveau de l'oeil droit et à mouvement des doigts au niveau de l'oeil gauche, avec présence de foyers choriorétiniens diffus visualisés au fond d'oeil et à l'angiographie. Les sérologies VIH, toxoplasmose et CMV sont positives. Le patient a été mis sous traitement anti-toxoplasmose (Sulfadiazine et pyriméthamine) et anti-CMV (Ganciclovir per os). L’évolution sous traitement a été marquée par une régression de la hyalite avec la persistance des foyers choriorétiniens évolutifs et une acuité visuelle réduite à perception lumineuse.

Risk of Recurrence of Preexisting Ocular Toxoplasmosis during Pregnancy

PURPOSE

Comparison between the risk of recurrence during pregnancy with nonpregnant periods in patients with ocular toxoplasmosis (OT).

METHODS

Records of 40 women were retrospectively reviewed. The women were subdivided into either a pregnant group or a control group formed by nonpregnant women during follow-up. Comparable cases from the literature were added. Mean number of recurrences per year was compared.

RESULTS

Eleven women with pregnancies could be included. Six cases from the literature were added (total n = 17). Mean number of recurrences per year during versus not during pregnancy was 0.16 (SD 0.39) versus 0.32 (SD 0.30; p = 0.088), respectively. In the control group (n = 29) the mean number of recurrences per year (0.31; SD 0.27) was significantly higher when compared to cases during pregnant periods (p = 0.002).

CONCLUSION

Adding to published series, the presented data do not provide evidence for a relevant impact of pregnancy on recurrence behavior in OT.

Recurrence rates of ocular toxoplasmosis during pregnancy

PURPOSE

To investigate whether recurrence rates of ocular toxoplasmosis are higher during pregnancy in women of childbearing age.

DESIGN

Retrospective longitudinal cohort study.

METHODS

We reviewed medical records of all women seen at a university eye clinic (Utrecht, Netherlands) during episodes of active toxoplasmic retinochoroiditis that occurred while the women were of childbearing age (16-42 years). Each woman was sent a questionnaire requesting information regarding all pregnancies and episodes of ocular toxoplasmosis, whether or not episodes were observed at the eye clinic. Conditional fixed-effects Poisson regression was used to model incidence rate ratios of recurrence during pregnant versus nonpregnant intervals, adjusted for potential confounders, including age at time of active toxoplasmic retinochoroiditis and interval since last episode of active disease, which are known to influence risk for recurrence.

RESULTS

Questionnaires were returned by 50 (58%) of 86 women, 34 of whom had had 69 pregnancies during 584 person-years of study. There were 128 episodes of ocular toxoplasmosis during the study period (6 during pregnancy). First episodes of ocular toxoplasmosis occurred between ages 9.6 and 38.5 years. The youngest age at pregnancy was 16.1 years; the oldest age at childbirth was 40.9 years. The incidence-rate ratios for pregnant versus nonpregnant intervals were in the direction of lower recurrence rates during pregnancy, with point estimates of 0.54 and 0.75 under 2 different approaches, but the ratios were not significantly different from the null value (P values of 0.16 and 0.55).

CONCLUSIONS

Recurrence rates of ocular toxoplasmosis are probably not higher during pregnancy, in contrast to traditional beliefs.

Is reactivation of toxoplasmic retinochoroiditis associated to increased annual rainfall?

BACKGROUND

Reactivation of toxoplasmic retinochoroiditis is the most frequent form of uveitis in Misiones, Argentina. Fluctuations in the number of patients consulting with this type of uveitis were detected during the last decade. Since the province was consecutively exposed to rainy and dry periods over the last years, we decided to explore whether a relationship between reactivation of toxoplasmic retinochoroiditis and rain might be established according to the data registered during the 2004-2010 period.

RESULTS

The frequency of toxoplasmic reactivation episodes increases when precipitation increases (mostly in second and fourth trimesters of each year). Analysis of the independent variables demonstrates that precipitation is a significant predictor of the frequency of reactivation episodes. Although registered toxoplasmic reactivations were more frequent during the third trimester of the year, the association between the third trimester and the reactivation episodes did not reach statistical significance.

CONCLUSION

Prolonged and intense rainfall periods were significantly associated with the reactivation of toxoplasmic retinochoroiditis. Changes promoted by this climatic condition on both the parasite survival in the soil as well as a putative effect on the host immune response due to other comorbidities are discussed.

Evaluation of seroepidemiological toxoplasmosis in HIV/AIDS patients in the south of Brazil

Toxoplasmosis is considered one of the opportunistic infections for individuals with the Acquired Immunodeficiency Syndrome (AIDS), and is also a major cause of morbidity and mortality. The aim of this study was to evaluate the prevalence of neurotoxoplasmosis, ocular toxoplasmosis and antibodies for Toxoplasma gondii in HIV-positive patients attending the SAE (Specialized Assistance Service for HIV/AIDS), as well as to associate their serological profile with epidemiological and clinical data. A total of 250 patients participated in the study from December, 2009 to November, 2010. Serological analysis was performed using the indirect immunofluorescent technique; epidemiological data were gathered by a questionnaire, and clinical history was based on the analysis of medical charts. Prevalence of seropositivity was 80%, with history of neurotoxoplasmosis in 4.8% and of ocular toxoplasmosis in 1.6% of the patients. The Highly Active Antiretroviral Treatment (HAART) was not used by 32% of the patients, 18.4% of the patients had CD4+ T- lymphocyte count less than 200 cells/mm³ and 96.8% of them were not aware of the modes of disease transmission. These findings led us to conclude that the study population is at high risk of clinical toxoplasmosis, because of both reactivation of infection in the seropositive patients who do not make a regular use of HAART, and primo-infection in seronegative patients worsened by an unawareness of the modes of infection reported in this study.

Ocular toxoplasmosis II: clinical features, pathology and management

The term, ocular toxoplasmosis, refers to eye disease related to infection with the parasite, Toxoplasma gondii. Recurrent posterior uveitis is the typical form of this disease, characterized by unilateral, necrotizing retinitis with secondary choroiditis, occurring adjacent to a pigmented retinochoroidal scar and associated with retinal vasculitis and vitritis. Multiple atypical presentations are also described, and severe inflammation is observed in immunocompromised patients. Histopathological correlations demonstrate focal coagulative retinal necrosis, and early in the course of the disease, this inflammation is based in the inner retina. For typical ocular toxoplasmosis, a diagnosis is easily made on clinical examination. In atypical cases, ocular fluid testing to detect parasite DNA by polymerase chain reaction or to determine intraocular production of specific antibody may be extremely helpful for establishing aetiology. Given the high seroprevalence of toxoplasmosis in most communities, serological testing for T. gondii antibodies is generally not useful. Despite a lack of published evidence for effectiveness of current therapies, most ophthalmologists elect to treat patients with ocular toxoplasmosis that reduces or threatens to impact vision. Classic therapy consists of oral pyrimethamine and sulfadiazine, plus systemic corticosteroid. Substantial toxicity of this drug combination has spurred interest in alternative antimicrobials, as well as local forms of drug delivery. At this time, however, no therapeutic approach is curative of ocular toxoplasmosis.

CD73-generated adenosine facilitates Toxoplasma gondii differentiation to long-lived tissue cysts in the central nervous system

Toxoplasma gondii is an obligate intracellular protozoan pathogen that traffics to the central nervous system (CNS) following invasion of its host. In the CNS, T. gondii undergoes transformation from a rapidly dividing tachyzoite to a long-lived, slow-dividing bradyzoite contained within cysts. The role of extracellular adenosine in T. gondii pathogenesis has not been previously investigated. T. gondii uses host purines such as adenosine for its energy needs, as it is unable to make its own. Here, we show that CD73(-/-) mice, which lack the ability to generate extracellular adenosine, are protected from T. gondii chronic infection, with significantly fewer cysts and reduced susceptibility to reactivation of infection in the CNS independent of host effector function. Parasite dissemination to the brain was unimpaired in CD73(-/-) hosts, suggesting that the reduced cyst number is due to impaired parasite differentiation in the CNS. Confirming this, T. gondii tachyzoites formed fewer cysts following alkaline pH stress in astrocytes isolated from CD73(-/-) mice compared with wild type, and in fibroblasts treated with a CD73 inhibitor. Cyst formation was rescued in CD73(-/-) astrocytes supplemented with adenosine, but not with adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine. Furthermore, mice lacking adenosine receptors had no defect in cyst formation. Based on these findings, we conclude that CD73 expression promotes Toxoplasma bradyzoite differentiation and cyst formation by a mechanism dependent on the generation of adenosine, but independent of adenosine receptor signaling. Overall, these findings suggest that modulators of extracellular adenosine may be used to develop therapies aimed at defending against human toxoplasmosis.

Prevalence, clinical characteristics, and causes of vision loss in patients with ocular toxoplasmosis

PURPOSE

To describe the prevalence, demographics, clinical features, and contributors to vision loss at presentation in a large cohort of patients with ocular toxoplasmosis seen at a tertiary referral center in northern California.

METHODS

A retrospective review of the charts of 233 patients with ocular toxoplasmosis examined over 24 years.

RESULTS

Ocular toxoplasmosis was diagnosed in 233 (8.4%) of 2761 patients with uveitis. The mean age at presentation was 27.2 years. Patients with ocular toxoplasmosis were more likely to be young (p<0.01), male (p<0.001), and Latino (p<0.001) as compared with patients in the entire uveitis cohort. At presentation, 159 patients (68.2%) had active disease, which was unilateral in all but one. Among the 160 eyes with active disease, 145 (90.6%) presented with a focal retinochoroiditis, 57.2% of which had an adjacent retinochoroidal scar. Atypical presentations occurred in 11 patients (6.9%). Of eyes with active disease, the main contributors to vision loss at presentation were intraocular inflammation (74.8%) and macular involvement (24.3%), whereas in eyes with inactive lesions the main contributors to vision loss were macular scar formation (67.9%) and amblyopia (11.3%). Younger age was the single significant predictor of macular involvement.

CONCLUSIONS

Ocular toxoplasmosis is a common cause of uveitis. Our patients were more likely than general uveitis patients to be young, male, and Latino, often having emigrated from Mexico or Central or South America. The most common contributors to decreased vision in eyes with active lesions were inflammation and macular involvement, whereas in eyes with inactive lesions they were macular scar formation and amblyopia.

Therapy for ocular toxoplasmosis

PURPOSE

To review current evidence for the treatment of ocular toxoplasmosis (OT).

DESIGN

Narrative review and expert recommendations.

METHODS

Meta-analysis and selected original articles from the medical literature were reviewed critically. Expert recommendations were analyzed.

RESULTS

Numerous observational studies suggest a benefit of short-term antimicrobial therapy for toxoplasmic retinochoroiditis in immunocompetent patients, although its efficacy has not been proven in randomized clinical trials. A randomized clinical trial revealed that intermittent trimethoprim/sulfamethoxazole treatment could decrease the rate of recurrence in high-risk patients. Intravitreal injection of clindamycin and dexamethasone was an acceptable alternative to the classic treatment for OT in a randomized clinical trial.

CONCLUSIONS

Opinions about therapy differ and controversy remains about its type, efficacy, and length. Intravitreal therapy may be promising for OT. A recent description of the presence of parasitemia in patients with active and inactive ocular toxoplasmosis raises new questions that need to be explored.

Toxoplasmosis: a global threat

Toxoplasmosis, a disease described worldwide, which is caused by the protozoan Toxoplasma gondii, commonly involves the retina. The disease has a higher impact in immunocompromised individuals and in congenital infection because of the severity of central nervous system involvement. Although simple prophylactic measures could reduce transmission, T. gondii seroprevalence is still high, especially in South America. Educational campaigns and the development of new drugs to prevent primary infection could potentially reduce the burden of the disease.

Review for disease of the year: differential diagnosis of ocular toxoplasmosis

The diagnosis of ocular toxoplasmosis is mainly clinical, based in the presence of focal necrotizing retinochoroiditis often associated with a preexistent chorioretinal scar, and variable involvement of the vitreous, retinal blood vessels, optic nerve, and anterior segment of the eye. Recognition of this clinical spectrum of toxoplasmic retinochoroiditis is crucial, but other infectious, noninfectious, and neoplastic entities should also be considered in the differential diagnosis. Investigations such as serological tests, polymerase chain reaction of ocular fluids, and assessment of intraocular antibody synthesis are helpful in uncertain cases. This article provides an overview of the differential diagnosis of ocular toxoplasmosis, focusing on the most important entities to be considered and emphasizing distinctive features of each one of them in the clinical setting. Ocular toxoplasmosis has multiple clinical manifestations, which partially overlap with those of other entities and these should be carefully considered when making the differential diagnosis, particularly in less typical cases.

An ophthalmologist survey-based study of the atypical presentations and current treatment practices of ocular toxoplasmosis in India

The last two decades have seen a paradigm shift in the understanding of ocular toxoplasmosis. Post-natally acquired infection with its atypical presentations, has emerged as a common form of the disease. We conducted a questionnaire-based survey to investigate the characteristics of atypical presentations and current treatment practices of ocular toxoplasmosis, in India. A written questionnaire was distributed to ophthalmologists at two major uveitis meetings, held in Hyderabad, India in January, 2009. It evaluated characteristics of atypical presentations of ocular toxoplasmosis and specific treatment-related issues in India. Of 37 respondents who completed the questionnaire, 28 (75.6%) found atypical presentations in less than one-fourth of ocular toxoplasmosis patients. Atypical presentations were mostly seen as primary retinitis lesion, and in healthy immuno-competent individuals. Most ophthalmologists (n = 28, 75.6%) thought viral retinitis to be the most common differential diagnosis for atypical ocular toxoplasmosis and relied on serological tests (n = 19, 51.3%) for the diagnosis. Twenty-three (62.1%) respondents treated all patients with active lesions. A diverse range of treatment regimens were used, trimethoprim-sulphamethoxazole combination being most common (n = 12, 32.4%). Corticosteroids were included in all regimens. Atypical presentations of ocular toxoplasmosis were identified by all ophthalmologists, participating in the survey, though not commonly by most. Treatment practices were diverse, reflecting the lack of consensus on this issue.

[Toxoplasmic chorioretinitis: positive PCR on vitreous with negative serology for Toxoplasma gondii]

Ocular recurrences of congenital toxoplasmosis usually occur during the first and second decades of life. At that time, serum levels of IgG against toxoplasmosis are almost always detectable because of the very high sensitivity of the test. The diagnosis is mainly supported by the ophthalmological examination and the good clinical response to treatment. In atypical cases, the Goldman-Witmer coefficient (GWC) on aqueous and polymerase chain reaction (PCR) on aqueous or vitreous is usually performed to substantiate the diagnosis. We report a case of recurrent macular chorioretinitis in a 13-year-old immunocompetent patient with a history of congenital toxoplasmosis whose repeated serologies remained negative or uncertain. However, the diagnosis of toxoplasmic chorioretinitis was supported by the detection of Toxoplasma gondii DNA by PCR analysis in a vitreous sample. Although the sensitivity of serology is very high, it is not perfect and there are false-negative results. In case of high clinical presumption in spite of a negative serology, PCR could be a helpful contribution to the diagnosis.

Pars plana vitrectomy in the treatment of severe complicated toxoplasmic retinochoroiditis

PURPOSE

To present the anatomic and functional results of pars plana vitrectomy performed in severe complicated toxoplasmic retinochoroiditis.

METHODS

Three patients, 2 women and 1 man aged 57, 22, and 57 years, are presented. The first patient was under immunosuppressive therapy for dermatomyositis and underwent diagnostic/therapeutic vitrectomy for severe toxoplasmic panuveitis with dense vitritis. The other 2 patients underwent vitrectomy for macula-off rhegmatogenous retinal detachment that developed after severe toxoplasmic panuveitis.

RESULT

Preoperative visual acuity was hand movement for the first 2 patients and 20/400 for the third. All patients received pars plana vitrectomy with epiretinal membrane peeling, laser photocoagulation, and SF6 gas tamponade. The second and third patients needed 5 and 3 additional operations, respectively, including extensive retinotomies and silicone-oil tamponade, for recurrent retinal detachment due to proliferative vitreoretinopathy. At the end of the follow-up period (11, 5, and 1 year, respectively), the retina was attached and visual acuity was 20/30 for the first patient but counting fingers for the other 2 patients.

CONCLUSIONS

Severe panuveitis and/or recurrent retinal detachment may develop in some cases of ocular toxoplasmosis, compromising the visual prognosis. Retinal detachment due to toxoplasmosis is generally complex, and long-acting tamponade with silicone oil should be contemplated for anatomic retinal reattachment.

[Ocular complications of HIV infection: experience of the Northern Excellence Pole of Morocco]

INTRODUCTION

HIV infection is associated with a wide variety of ophthalmic manifestations. The objective of this study was to identify the ocular complications of HIV/AIDS in Morocco.

MATERIAL AND METHODS

A retrospective study conducted in the internal medicine department of the Rabat Teaching Hospital between 1998 and 2008. All HIV-positive patients were retained for the study. Each patient had an exhaustive ocular examination.

RESULTS

Of 115 ophthalmologic examinations, 28 were abnormal. Twenty-seven patients had stage C HIV infection and one patient was in stage A. The ocular manifestations were: 21 cases of ocular HIV-related anomalies (microangiopathies), four cases of cytomegalovirus (CMV) retinitis, one case of toxoplasmosis chorioretinitis, one case of CMV retinitis associated with toxoplasmosis chorioretinitis, two cases of Cryptococcus neoformans infection, two cases of varicella-zoster virus (VZV) retinitis, and one case of conjunctival Kaposi sarcoma. The CD4 count average was of 86±91/mm(3). Twenty-six patients had a CD4 count lower than 200/mm(3). Progression was favorable in 85 % of the cases, with three cases of blindness: bilateral in a case of VZV retinitis and unilateral in two cases of CMV retinitis and toxoplasmosis chorioretinitis.

CONCLUSION

CMV infection is the main ocular opportunistic infection in our series. However, Highly Active Antiretroviral Treatment (HAART) may be the cause for the decline in the prevalence of ocular diseases and visual impairment in HIV/AIDS.

CXCL10 is required to maintain T-cell populations and to control parasite replication during chronic ocular toxoplasmosis

PURPOSE

Toxoplasma gondii is a major cause of ocular disease, which can lead to permanent vision loss in humans. T cells are critically involved in parasite control, but little is known about the molecules that promote T-cell trafficking and migration in the retina. Thus, the aim of this study was to image and dissect the T-cell response during chronic toxoplasmic retinochoroiditis.

METHODS

C57BL/6 mice were infected with the Me49 strain of T. gondii, and T cells that infiltrated the eye were analyzed by flow cytometry and imaged using multiphoton microscopy. IFN-γ, CXCL9, CXCL10, and CXCR3 mRNA levels were measured by real-time PCR. To investigate the role of CXCL10, mice were treated with anti-CXCL10 antibodies, and histopathology and immunohistochemistry were performed to monitor changes in pathology, cellular infiltration, and parasite burden in the eye.

RESULTS

Infection with T. gondii leads to the infiltration of highly activated motile T cells into the eye. These cells express CXCR3 and are capable of producing IFN-γ and TNF-α, and CD8+ T cells express granzyme B. The expression of CXCL9 and CXCL10 in the retina was significantly upregulated during chronic infection. Treatment of chronically infected mice with anti-CXCL10 antibodies led to decreases in the numbers of CD3+, CD4+, and CD8+ T cells and the amount of IFN-γ mRNA expression in the retina and an increase in replicating parasites and ocular pathology.

CONCLUSIONS

The maintenance of the T-cell response and the control of T. gondii in the eye during chronic infection is dependent on CXCL10.