Intraocular anti-Toxoplasma gondii IgA antibody production in patients with 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.

Infectious Uveitis in Horses and New Insights in Its Leptospiral Biofilm-Related Pathogenesis

Uveitis is a sight-threatening eye disease in equids known worldwide that leads to considerable pain and suffering. By far the most common type of uveitis in Germany and neighboring countries is classical equine recurrent uveitis (ERU), which is caused by chronic intraocular leptospiral infection and is the main cause of infectious uveitis in horses. Other infectious causes are extremely rare and are usually clinically distinguishable from ERU. ERU can be treated very effectively by vitreous cavity lavage (vitrectomy). For proper indications of this demanding surgery, it is necessary to differentiate ERU from other types of uveitis in which vitrectomy is not helpful. This can be conducted on the basis of anamnesis in combination with ophthalmologic findings and by aqueous humor examination. During vitrectomy, vitreous material is obtained. These vitreous samples have historically been used for numerous etiologic studies. In this way, a chronic intraocular leptospiral infection has been shown to be the cause of typical ERU and, among other findings, ERU has also been recognized as a biofilm infection, providing new insights into the pathogenesis of ERU and explaining some thus far unexplainable phenomena of ERU. ERU may not only have transmissible aspects to some types of uveitis in humans but may also serve as a model for a spontaneously occurring biofilm infection. Vitreous material obtained during therapeutically indicated vitrectomy can be used for further studies on in vivo biofilm formation, biofilm composition and possible therapeutic approaches.

When biology supports clinical diagnosis: review of techniques to diagnose ocular toxoplasmosis

Toxoplasmosis is a common infection whose worldwide prevalence is estimated at 30%, with large disparities across the world. Among infected subjects, the prevalence of ocular toxoplasmosis (OT) is, however, limited to about 2% in Europe and 17% in South America. In France, it is estimated that about 1 000 000 patients present either active OT or subsequent chorioretinal scars. Toxoplasmagondii is the first cause of posterior uveitis worldwide, responsible for retinochoroiditis, at times associated with anterior uveitis. To date, there is no consensus yet on how to diagnose OT, which is often based only on clinical presentation. Nevertheless, OT-associated symptoms are often atypical and misleading. Over the last 20 years, tremendous progress has been made in biological tools, enabling parasitologists to confirm the diagnosis in most suspected cases of OT. Using anterior chamber puncture, a safe and fast procedure, ophthalmologists sample aqueous humour for analysis using multiple techniques in order to reach high specificity and sensitivity in OT diagnosis. In this article, we present the different techniques available for the biological diagnosis of OT, along with their characteristics, and propose a diagnostic algorithm designed to select the best of these techniques if clinical examination is not sufficient to ascertain the diagnosis.

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.

Role of molecular diagnostics in ocular microbiology

Although microbial culture remains the gold standard for diagnosis of many ocular infections, the technique is limited by low yield, inability to detect certain organisms, and potentially long delays to results. DNA-based molecular diagnostic techniques use detection of specific nucleic acid sequences as evidence for presence of suspected pathogens. The polymerase chain reaction (PCR) is a powerful molecular biology technique that allows for detection of fewer than 10 copies of pathogen genome. Recent technical advances in PCR have permitted quantitation of pathogen load using quantitative PCR (qPCR), and have permitted multiplexing of primer sets. Use of pan-bacterial and pan-fungal primers for ribosomal DNA sequences has allowed diagnosis of bacterial and fungal infections using molecular techniques. In this review, we highlight recent advances in the application of PCR to the diagnosis of anterior segment and posterior segment ocular infectious diseases.

Pediatric uveitis: An update

Because of their varied spectrum of clinical presentation and difficulty in management, pediatric uveitis remains a challenge to the ophthalmologist. Variations in clinical presentation, difficulties in eye examination, extended burden of the inflammation over quality of life, limited treatment modalities, risk of amblyopia are the main challenges in the management of pediatric uveitis. Pediatric uveitis is a cause of significant ocular morbidity and severe vision loss is found in 25-33% of such cases. This article summarizes the common causes of uveitis in children with special approach to the evaluation and diagnosis of each clinical entity.

Laboratory support in the diagnosis of uveitis

Intraocular inflammations are still a diagnostic challenge for ophthalmologists. It is often difficult to make a precise etiological diagnosis in certain situations. Recently, there have been several advances in the investigations of uveitis, which has helped the ophthalmologists a lot in the management of such clinical conditions. A tailored approach to laboratory diagnosis of uveitic cases should be directed by the history, patient's symptoms and signs, and clinical examination. This review summarizes various modalities of laboratory investigations and their role in the diagnosis of uveitis.

Real-time polymerase chain reaction and intraocular antibody production for the diagnosis of viral versus toxoplasmic infectious posterior uveitis

PURPOSE

The aim of this work was to determine the diagnostic performance of real-time polymerase chain reaction (RT-PCR) and to assess intraocular specific antibody secretion (Goldmann-Witmer coefficient) on samples from patients with signs of posterior uveitis presumably of infectious origin and to target the use of these two biologic tests in the diagnostic of Toxoplasma/viral Herpesviridae posterior uveitis by the consideration of clinical behavior and delay of intraocular sampling.

METHODS

Aqueous humour and/or vitreous fluid were collected from patients suspected of having posterior uveitis of infectious origin at presentation (140 samples). The diagnosis was confirmed by quantification of antibodies with the Goldmann-Witmer coefficient (GWC) and for detection of Herpesviridae and Toxoplasma gondii genomes with RT-PCR. Forty-one patients had final diagnosis of uveitis of non-Toxoplasma/non-viral origin and 35 among them constituted the control group. The main outcome measures were sensitivity, specificity, and positive and negative predictive values (PPV and NPV).

RESULTS

When pre-intraocular testing indication was compared with final diagnosis, GWC was a more sensitive and specific method than RT-PCR, and was successful in detecting T. gondii, especially if the patient is immunocompetent and the testing is carried out later in the disease course, up to 15 months. For viral Herpesviridae uveitis, the sensitivity and PPV of PCR evaluation was higher than detected with GWC with respectively 46% compared with 20% for sensitivity and 85% versus 60% for PPV. In either viral retinitis or toxoplasmosis infection, RT-PCR results were positive from 24 h, although GWC was not significant until 1 week after the onset of signs. In toxoplasmosis patients, positive RT-PCR results were statistically correlated with the chorioretinitis area (more than three disc areas; p = 0.002), with the age older than 50 (p = 0.0034) and with a clinical anterior inflammation (Tyndall ≥1/2+) and panuveitis; (p = 0.0001).

CONCLUSIONS

For the diagnosis of viral or toxoplasmosis-associated intraocular inflammation, the usefulness of laboratory diagnosis tools (RT-PCR and GWC) depends on parameters other than the sensitivity of the tests. Certain patient characteristics such as the age of the patients, immune status, duration since the onset of symptoms, retinitis area, predominant site and extent of inflammation within the eye should orientate the rational for the choice of laboratory testing in analysis of intraocular fluids.

Toxoplasma retinochoroiditis in pregnancy: Using current evidence to inform management

Toxoplasma retinochoroiditis in pregnancy may create considerable patient anxiety and is a dilemma for the treating ophthalmologist. A case report highlighting this clinical issue is presented followed by a review of the literature. Consensus in relation to the management of toxoplasma retinochoroiditis in pregnancy is lacking and is discussed.

Polymerase chain reaction in intraocular inflammation

Polymerase chain reaction (PCR) is a technique involving enzymatic amplification of nucleic acid sequences in repeated cycles of denaturation, oligonucleotide annealing and DNA polymerase extension. It is a powerful molecular biologic tool that allows the rapid production of analytic quantities of DNA from small amounts of starting material. PCR can be performed on nearly any ocular specimen or biopsy. For diagnosis of uveitis, the obtained sample is usually an anterior chamber paracentesis or vitreous tap. PCR potentially is more sensitive than culture for detection of many organisms. By utilizing a secondary detection system in concert with the initial PCR reaction, perfect specificity can be assured. The initial application of PCR diagnostics to ophthalmic disease was in the detection of viral uveitis. PCR has also been implicated in studies of noninfectious uveitis. The most common application is HLA typing. A universal bacterial PCR can be very helpful for the diagnosis of bacterial endophthalmitis at an early stage of the disease.

Comparison of immunoblotting, calculation of the Goldmann-Witmer coefficient, and real-time PCR using aqueous humor samples for diagnosis of ocular toxoplasmosis

We compared three biological methods for the diagnosis of ocular toxoplasmosis (OT). Paired aqueous humor and serum samples from 34 patients with OT and from 76 patients with other ocular disorders were analyzed by three methods: immunoblotting or Western blotting (WB), the calculation of the Goldmann-Witmer coefficient (GWC), and PCR. WB and GWC each revealed the intraocular production of specific anti-Toxoplasma immunoglobulin G in 81% of samples (30 of 37). PCR detected toxoplasmic DNA in 38% of samples (13 of 34). Nine of the 13 PCR-positive patients were immunocompetent. Combining the techniques significantly improved the diagnostic sensitivity, to 92% for the GWC-WB combination, 90% for the WB-PCR combination, and 93% for the GWC-PCR combination. The combination of all three techniques improved the sensitivity to 97%.

Congenital toxoplasmosis: priorities for further health promotion action

Toxoplasmosis is a disease of considerable public health impact. As the transmission, occurrence and phenotype of this disease are influenced in a complex way by host genetics, immunity, behaviour and by the agent characteristics, prevention will not be simple. This article aimed to review studies defining seroprevalence of and characteristic sociodemographic, biological and lifestyle risk factors for Toxoplasma gondii infection in pregnant women, to evaluate screening and educational programmes, and to assemble recommendations for combating toxoplasmosis in populations at risk. Electronic databases were searched, using a specific search strategy, from 1975 to 2007. There is a high prevalence of T. gondii antibodies in pregnant women worldwide, with some geographic discrepancies attributed to climatic conditions, local food customs, hygiene, lifestyle and cultural differences. The main risk factors for toxoplasmosis in pregnant women are unsanitary feeding habits, poor immune system, contact with cats, contact with soil, pregnancy, number of births, older age, race, travelling outside the country, drinking beverages prepared with unboiled water, consumption of municipal or uncontrolled (well/spring) water and T. gondii strain virulence. Knowledge of these risk factors helps to identify priorities for further epidemiological work and defines effective preventive measures along five main themes of action: information and health education; screening of pregnant women and infants; limiting harm from risk behaviour; treatment of cases found to be at risk; and vaccination.

[Ocular toxoplasmosis]

Toxoplasmosis is a parasitic zoonosis which occurs worldwide and is an important cause of blindness. The infection is naturally acquired by the ingestion of oocysts excreted by infected cats or by ingestion of tissue cysts in undercooked or raw meat. Primary infection during pregnancy may result in a congenital infection. Toxoplasmic retinochoroiditis is the most common cause of posterior uveitis in immunocompetent patients. Depending on the patient's age, ocular symptoms vary presenting with reduced visual acuity, strabismus, and nystagmus in young children - in adults decreased vision and floaters are most frequently reported. Active toxoplasmic retinochoroiditis typically presents as grey-white retinal necrosis with choroiditis, vasculitis and vitritis. However, atypical presentations including neuroretinitis, papillitis, Fuchs-like anterior uveitis, scleritis and acute retinal necrosis have been described. The diagnosis is based on clinical findings and can be supported by the detection of antibodies and Toxoplasma gondii DNA. Toxoplasmosis therapy includes antimicrobial drugs and corticosteroids. There are several regimens with different drug combinations including, among others, pyrimethamine, sulfadiazine, clindamycin, and trimethoprim-sulfamethoxazol. The prognosis for ocular toxoplasmosis is favorable in immunocompetent individuals, as long as the central macula is not directly involved. The present article reviews the epidemiology, pathogenesis, clinical presentation and management of toxoplasmic retinochoroiditis.

Polymerase chain reaction and Goldmann-Witmer coefficient analysis are complimentary for the diagnosis of infectious uveitis

PURPOSE

To determine the relative contribution of the analysis of intraocular antibody production and the polymerase chain reaction (PCR) in aqueous humor (AH) to the diagnosis of infectious uveitis.

DESIGN

Retrospective case-control study.

METHODS

Paired AH and serum samples from 230 patients suspected of infectious uveitis were examined for intraocular antibody production against herpes simplex virus (HSV), varicella zoster virus (VZV), and Toxoplasma gondii by calculating the Goldmann-Witmer coefficient (GWC). In addition, AH samples were investigated by real-time PCR to determine the presence of microbial DNA.

RESULTS

Positive results were obtained in 54 cases (23%): 13 HSV (24%), 16 VZV (30%), and 25 T gondii (46%). Of these, 23 (43%) were positive for both GWC and PCR, 26 (48%) only for GWC, and 5 (9%) only for PCR. With PCR as the sole diagnostic approach, a correct diagnosis of the infectious etiology would have been missed in 34% of cases for the herpes viruses and in 64% for T gondii. Analysis of the relationship between a positive laboratory diagnosis and the time of sampling after onset of ocular disease demonstrated that intraocular antibody production was found throughout the course of the diseases. Viral DNA was more readily detected early in infection. In contrast, T gondii nucleic acid was not detected until 3 weeks after onset of ocular disease.

CONCLUSIONS

Analysis of intraocular antibody production contributed considerably to the etiological diagnosis of infectious uveitis, most notably of ocular toxoplasmosis early after onset of disease. Therefore, both PCR and GWC determination might be performed for comprehensive diagnosis of intraocular infections.

Lacrimal secretory IgA in active posterior uveitis induced by Toxoplasma gondii

It is quite difficult to diagnose active toxoplasmosis in patients with ocular toxoplasmosis. Active posterior uveitis presumably due to Toxoplasma gondii infection (APUPT) is seldom produced during a prime-infection; hence most patients do not show high IgM antibodies. High levels of IgA have been described in active toxoplasmosis. The purpose of this study was to investigate possible association between APUPT and the specific anti-parasite sIgA in tears. The study was carried out as case-control. Tears of 25 clinically confirmed APUPT patients and 50 healthy control subjects were analyzed. All were IgG seropositive. Specific sIgA was determined by ELISA assay using T. gondii RH strain crude extract. Anti-T. gondii sIgA was found in 84% of the cases and in 22% of the control subjects. The intensity of the reaction was higher in APUPT cases (P = 0.007). There was strong association between APUPT patients and lacrimal sIgA (odds-ratio 18.61, P = 0.0001). ELISA test sensitivity was 84% and specificity 78%. Our data suggest that anti-T.gondii secretory IgA found in tears may become an important marker for active ocular toxoplasmosis.

Determinants of immunodiagnostic success in human ocular toxoplasmosis

Ocular toxoplasmosis is a local manifestation of systemic infection in which Toxoplasma spreads into the eye, affecting mainly the posterior segment of the eye. Reactivation of the initial retinal condition presumably results from the rupture of quiescent parasitic cysts lying adjacent to pre-existing scars and may secondarily involve the choroid (leading to retinochoroiditis). Although the molecular mechanisms underlying host-parasite interaction are largely unknown, toxoplasmic retinochoroiditis usually remains a local event, and does not necessarily evoke a detectable systemic immune response. Local immunotolerance mechanisms may likewise confound attempts to confirm the clinical diagnosis by serology. Aqueous humour may be analysed for the presence of parasite DNA or of specific antibodies, but the DNA burden therein is low, and a more definite confirmation would require risky puncturing of the vitreous. Laboratory confirmation of the diagnosis is also frustrated by marked individual differences in the time elapsing between the onset of clinical symptoms and the activation of specific antibody production, resulting in a high proportion of false negative results. Whether a delay in the onset of local specific antibody production reflects immunotolerance in cases of congenital - but not obviously in those of acquired - infection remains an open question, but it could account for a relatively low confirmation rate in laboratory tests for local antibody production. Against this background, current diagnostic strategies need to be re-evaluated with a view to future improvements.

Pesquisa de anticorpos anti Toxoplasma gondii em fluidos intra-oculares (humor vítreo e humor aquoso) de pacientes com toxoplasmose ocular, na cidade de Belém, PA

Foi realizada pesquisa de anticorpos IgG, IgM e IgA anti-Toxoplasma gondii no soro e fluidos intra-oculares (humor aquoso e vítreo) de pacientes com toxoplasmose ocular. A partir dos resultados obtidos verificou-se que anticorpos IgG e IgA intraocular anti-Toxoplasma gondii podem vir a ser importantes marcadores no diagnóstico de toxoplasmose ocular.

Aqueous humor and serum immunoblotting for immunoglobulin types G, A, M, and E in cases of human ocular toxoplasmosis

The purpose of this study was to compare the local and systemic Toxoplasma-specific humoral immune responses in individuals with ocular toxoplasmosis (OT). To this end, paired aqueous humor and serum samples from 46 individuals with active OT and from 30 individuals without inflammatory eye disease (controls) were analyzed by immunoblotting for anti-Toxoplasma immunoglobulin G (IgG), IgA, IgM, and IgE directed against 20- to 120-kDa antigens. The presence in the aqueous humor of a unique band, or of at least three bands that were at least three times more intense in aqueous humor than in serum, was taken as evidence of local antibody production. IgG bands were detected in 98% of the aqueous humor samples, while IgA bands were detected in 76%, IgM bands were detected in 8%, and IgE bands were not detected in any. Evidence of local production of specific antibodies was found in 32 cases (70%) (IgG in 23 [50%]; IgA in 16 [35%]). In 10 instances (22%), routine laboratory tests were not indicative of OT. In 14 cases (30%), no local antibody production was detected by immunoblotting; 3 of these cases yielded evidence of local antibody production according to the Goldmann-Witmer coefficient. Local antibody production was revealed for 7 of the 30 controls (23%). Hence, the sensitivity of immunoblotting for IgG and IgA is 70%, and the specificity is 77%. We conclude that immunoblotting for local specific IgG and IgA supports the clinical diagnosis of OT in 70% of cases. In 22% of these, the diagnosis is not confirmed by other laboratory tests. Hence, immunoblotting increases the sensitivity of routine laboratory tests and should be considered for samples that register negative by such tests.

CD4+ T cells in the pathogenesis of murine ocular toxoplasmosis

The role of CD4(+) T cells in the pathogenesis of ocular toxoplasmosis was investigated in murine models utilizing inbred C57BL/6 mice deficient either in CD4(+), CD8(+), or B cells (microMT). Severe necrosis and inflammation with replicating parasites were observed in the eyes of control mice after primary ocular infection, and near-normal histology with few tachyzoites was observed in the eyes of mice immunized intraperitoneally with the avirulent ts-4 strain followed by intraocular challenge with the RH strain of Toxoplasma gondii. In contrast, mild inflammation without evidence of necrosis associated with increased parasite burdens were observed in the eyes of CD4 knockout (KO) mice after both primary ocular infection and challenge with RH tachyzoites. CD8 KO mice, as well as microMT mice, demonstrated increased ocular necrosis in response to either primary ocular infection or challenge. The parasite burden was increased in the eyes of both CD8 KO and microMT mice in which the parasite load was even higher. As expected, there were no increases in the levels of immunoglobulin G in serum or aqueous humor in microMT mice, and there was no increase in the levels of gamma interferon and tumor necrosis factor alpha in the sera of CD4 KO mice after both infection and challenge. These results suggest that the ocular inflammatory response to the parasite is mediated primarily by the CD4(+)-T-cell response. CD8(+) T cells and B cells may play an important role in limiting tachyzoite proliferation in the eyes. Mice deficient in CD8(+) CD4(+) T cells or B cells exhibit diminished vaccine-induced resistance and increased ocular parasite burden after challenge.

Use of fluorescence resonance energy transfer hybridization probes to evaluate quantitative real-time PCR for diagnosis of ocular toxoplasmosis

Toxoplasma gondii infection is an important cause of chorioretinitis in Europe and the United States. Ophthalmological examination and a good clinical response to adequate therapy mainly support ocular toxoplasmosis diagnosis. However, clinical diagnostic may be difficult in some atypical cases. In these cases, laboratory confirmation, based on detection of local specific antibodies and parasite DNA by conventional PCR, is therefore important to confirm the disease etiology. More recently, real-time PCR has been developed to improve prenatal congenital toxoplasmosis diagnosis. We therefore examined the diagnostic value of quantitative real-time PCR for the detection of T. gondii in aqueous humor samples, associated with quantification of human beta-globin to control sample quantitative quality, by using a double fluorescence resonance energy transfer hybridization probes system with a double fluorescence reading. Of the 23 the clinically toxoplasmosis suspect patients, 22 showed serological evidence of exposure to Toxoplasma; one had a serological profile indicative of active infection. The analysis of paired aqueous humor and serum samples revealed an intraocular antibody production in 9 of 23 cases (39.1%). The quantitative real-time PCR revealed positive and high parasite numbers and high Toxoplasma/human genome ratios in three cases. Furthermore, PCR was the only positive confirmatory test in two cases (11.1%). None of the patients included in the control group (n = 7) had evidence of either local specific antibody production or T. gondii DNA detection, suggesting a good relative assay specificity. On the whole, quantitative real-time PCR appears to be useful for diagnosing atypical ocular toxoplasmosis presentations.

Usefulness of immunoblotting and Goldmann-Witmer coefficient for biological diagnosis of toxoplasmic retinochoroiditis

Toxoplasmosis is a frequent cause of retinochoroiditis. Although the diagnosis relies mainly on ophthalmological examination, biological approaches are particularly useful in patients with atypical lesions. In a prospective study to determine the value of immunoblotting and immune load calculation in the diagnosis of active toxoplasmic retinochoroiditis, aqueous humor samples from 21 patients with retinochoroiditis and 5 control patients with cataracts were tested. Immune load was calculated on the basis of intraocular antibody production. The immune load ratio between aqueous humor and serum (Goldmann-Witmer coefficient) was significant (i.e. >2) in 9 of the 17 (53%) patients with retrospectively documented toxoplasmic retinochoroiditis. Immunoblotting suggested local antibody production in 10 of 17 (59%) patients. The combination of the two techniques gave a sensitivity of 71% (12/17). Both techniques were negative in the four patients in whom the final diagnosis of toxoplasmic retinochoroiditis was negative and in the five patients with cataracts. These results confirm the value of combining these two techniques. Moreover, immunoblotting has the advantages of being easy to perform and of requiring a very small sample.

Ocular manifestations of toxoplasmosis

PURPOSE OF REVIEW

The concepts of toxoplasmosis and its ocular manifestations in humans have thoroughly changed in the past 3 years. This review addresses new epidemiologic data, specifically the occurrence of ocular disease in postnatal infections, and puts the changed views on the frequency and pathogenesis of toxoplasmic ocular manifestations into historical perspective.

RECENT FINDINGS

Newly described clinical presentations are discussed together with their recent diagnostic possibilities. The new data on congenital or postnatal acquisition of infection and their importance for ocular involvement are presented as well as the high prevalence of 79% of recurrent disease in ocular toxoplasmosis, which cannot be prevented by short-term treatments. Recently published analyses of literature showed, unexpectedly, the lack of efficacy of short-term treatments for ocular disease as well as of the long-term prenatal treatments on fetal transmission rate and the severity of congenital disease.

SUMMARY

The recent guidelines for treatment are included together with the up-to-date recommendations for the treatment of ocular toxoplasmosis in the immunosuppressed host.

Ocular toxoplasmosis: a global reassessment. Part I: epidemiology and course of disease

PURPOSE

To update clinical information about ocular toxoplasmosis. Part I reviews information about prevalence of disease, sources of infection, relation of ocular disease to time of Toxoplasma gondii infection (congenital vs. postnatally acquired), and course of disease.

DESIGN

Literature review.

METHODS

Selected articles from the medical literature, information from recent scientific meetings, and the author's personal experiences were reviewed critically in preparation for the LX Edward Jackson Memorial Lecture.

RESULTS

The prevalence of T. gondii infection varies geographically and increases with age; in the United States, the overall proportion is 22.5%. The proportion of infected individuals in the United States who have had episodes of ocular toxoplasmosis is unknown, but may be approximately 2%. Prevalence of ocular involvement is substantially greater in other parts of the world, including southern Brazil. In addition to undercooked meat and unwashed vegetables, drinking water contaminated with oocysts may be an important source of infection in some settings. In contrast to traditional teaching, evidence suggests that most individuals with ocular toxoplasmosis were infected postnatally. Ocular lesions may first develop many years after T. gondii infection. The risk of recurrent ocular disease appears to be greater during the first year after an episode of toxoplasmic retinochoroiditis than during subsequent years.

CONCLUSIONS

Reassessment of older publications in the light of recent observations provides a richer understanding of ocular toxoplasmosis, although knowledge about the disease remains incomplete. A better understanding of the clinical characteristics and course of ocular toxoplasmosis will have important implications for developing more effective prevention and treatment strategies.

Cme review: polymerase chain reaction diagnostics for posterior segment disease

The polymerase chain reaction (PCR) is a powerful molecular biologic technique that permits detection and identification of infinitesimal quantities of DNA. It is well suited to the diagnosis of infectious posterior segment ocular inflammatory disease. In this review, the basic biochemistry of PCR, indications for its use, strengths and limitations to the technique, and examples of clinical application of PCR to posterior segment disease will be discussed. Emerging uses of PCR in linking pathogen to disease will also be outlined. After completion of this article, the reader will be able to describe the basic biochemistry and practical application of PCR in the diagnosis of posterior segment inflammatory disease, list the indications, advantages, and disadvantages of the technique, and outline the application of PCR diagnostics to individual differential diagnoses.

Diagnosis of toxoplasmic retinochoroiditis with atypical clinical features

PURPOSE

To determine the value of aqueous humor analysis for confirming the diagnosis of ocular toxoplasmosis in patients who present with atypical clinical features and to relate the results of local antibody production and polymerase chain reaction (PCR) with the extent of active retinitis and the immune status of the patient.

DESIGN

Retrospective case series.

METHODS

Sixty-seven consecutive patients with retinitis or retinochoroiditis that was clinically consistent with atypical ocular toxoplasmosis underwent diagnostic anterior chamber paracentesis and serological studies. The aqueous humor was analyzed both by PCR to detect Toxoplasma gondii B1 gene and by the Goldman-Witmer coefficient to determine levels of local anti-T. gondii antibody production.

RESULTS

In nine of the 67 cases, PCR was positive for T. gondii; seven of these were negative for local antibody production. All nine patients had illnesses associated with immunosuppression or advanced old age and all had active retinitis with a mean area of 11.5 disk areas (DA). Twenty-five of the remaining 58 cases were positive for local antibody production. These 25 had a mean area of active retinitis measuring 2.6 DA, and 24 of these patients were immunocompetent. All 34 cases with laboratory evidence of ocular toxoplasmosis diagnosed by either method responded to anti-T. gondii agents. The remaining 33 were negative for T. gondii infection by these two methods; some had laboratory evidence of other infections.

CONCLUSIONS

Although in the present study, the sensitivity and specificity of the aqueous humor PCR and Goldman-Witmer coefficient could not be ascertained in the laboratory diagnosis of toxoplasmic retinochoroiditis, the PCR method appears to confirm the diagnosis in immunocompromised individuals with large atypical foci of retinitis. Conversely, determination of local antibody production may be appropriate for proper diagnosis in immunocompetent individuals presenting with small foci of retinitis.

Ocular toxoplasmosis after the fifth decade

PURPOSE

To describe the clinical features in patients presenting with ocular toxoplasmosis after the fifth decade and to analyze laboratory findings in comparison to uveitis history and clinical data.

DESIGN

Prospective consecutive observational case series.

METHODS

A prospective clinical analysis of 27 consecutive patients older than 50 years of age with primary or recurrent ocular toxoplasmosis was performed during a period of 8 years. These cases account for 12% of all ocular toxoplasmosis cases irrespective of age indexed in our institution during the same period. Paired serum and aqueous humor samples were tested for anti-Toxoplasma gondii IgG, IgM, and IgA antibodies. The presence of T. gondii DNA in aqueous humor was determined by polymerase chain reaction followed by DNA hydridization method.

RESULTS

Although similar in age, two groups were distinguished clinically: 12 patients (44%) presented with usual forms of retinochoroiditis (mean +/- SD, 1.6 +/- 0.5 disk areas [DA] in size); 15 patients (56%) presented with atypical lesions, greater than 3 DA in size (mean +/- SD, 5.0 +/- 2.0 DA). The second group showed a higher rate of complications (P =.028) and a poorer visual outcome (P =.015). Twenty-four patients (89%) had intraocular IgG production, 17 (63%) had intraocular IgA production, 3 (11%) had intraocular IgM production, and 12 (44%) had a positive T. gondii DNA detection.

CONCLUSIONS

After the fifth decade, ocular toxoplasmosis remains an important cause of posterior uveitis. The combination of antibody detection by immunocapture tests with T. gondii DNA detection, both in aqueous humor, allowed the diagnosis of toxoplasmic infection in the atypical cases with large ocular lesions.

Applications of the polymerase chain reaction to diagnosis of ophthalmic disease

The polymerase chain reaction (PCR) is a powerful molecular biologic technique for the analysis of very small amounts of DNA. This technique has found increasing use in the past 10 years for the detection of pathogenic organisms associated with many forms of ocular inflammatory and infectious disease. PCR has shown utility in the diagnosis of viral uveitis, infectious endophthalmitis, and parasitic eye disease. The strengths and weaknesses of this diagnostic technique are discussed. Additionally, uses of PCR in linking known pathogens to disease, and to discovering novel pathogens, are addressed.

Herpes simplex virus type 2 as a cause of acute retinal necrosis syndrome in young patients

PURPOSE

To determine the causative virus in acute retinal necrosis (ARN) syndrome in a series of patients by calculation of modified Witmer coefficients.

DESIGN

Noncomparative case series.

PARTICIPANTS

Ten patients with ARN syndrome from four medical centers.

METHODS

Aqueous samples, vitreous samples, or both were collected prospectively during surgery from patients with a clinical diagnosis of ARN syndrome. Serologic measures of intraocular and serum antibodies to potentially causative viruses were measured by enzyme-linked immunosorbent assay.

MAIN OUTCOME MEASURES

Modified Witmer coefficients (immunoglobulin G and immunoglobulin A) for herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), varicella zoster virus (VZV), and cytomegalovirus (CMV), as well as adenovirus type 2, were calculated from aqueous or vitreous samples, or both.

RESULTS

Intraocular antibody measurements were strongly suggestive of a single diagnosis in 9 of 10 patients tested. Modified Witmer coefficients demonstrated intraocular antibody production to HSV in five patients and antibodies to VZV in four patients, and the measurement was inconclusive in one patient. No patients were positive for adenovirus or CMV. Strain-specific antibody titers demonstrated that all HSV-positive patients were reactive only to HSV-2. Herpes simplex virus type 2 was found predominantly in younger patients with ARN syndrome (mean age, 21.2 +/- 10 years; range, 17-39 years), whereas VZV was more commonly seen in older patients (mean age, 40.8 +/- 12.2 years; range, 29-58 years; P = 0.033). Immunoglobulin A testing confirmed immunoglobulin G testing in all patients examined.

CONCLUSIONS

Although VZV is thought to be the most common cause of ARN syndrome, HSV-2 is an important cause of ARN syndrome, particularly in younger patients. Because infection with HSV-2 has important medical ramifications, these results suggest that determination of a causal agent should be considered in some cases of ARN syndrome.

Toxoplasmosis in a patient with non-Hodgkin's lymphoma: the need for a good differential diagnosis

Toxoplasma gondii is an obligate intracellular parasite responsible for toxoplasmosis. Congenital and acquired forms of the disease have now been reported. In immunocompromised patients, the disease entity may resemble other diseases. Presented for discussion is an interesting case of acquired toxoplasmosis in an immunocompromised patient with several confounding factors necessitating a good differential diagnosis list. Also provided is a comprehensive review of toxoplasmosis diagnosis and management.

Early aqueous humor analysis in patients with human ocular toxoplasmosis

To evaluate the diagnostic sensitivity of a panel of laboratory tests for ocular toxoplasmosis performed at the time of presentation, paired samples of aqueous humor and serum were collected from 49 consecutive episodes of ocular toxoplasmosis with a clinical course of less than 3 weeks. Total immunoglobulin G (IgG) and Toxoplasma gondii-specific IgG, IgM, and IgA were quantified by enzyme-linked immunosorbent assay. The avidity of T. gondii-specific IgG was determined, and DNA extracted from aqueous humor was amplified for detection of a glycoprotein B gene sequence of T. gondii. The diagnosis was confirmed for 73% (36 of 49) of the patients; this rate rose to 79.5% if data from a later analysis of aqueous humor derived from five of the negative patients were included. The analysis of serum (detection of T. gondii-specific IgM and analysis of consecutive serum samples) alone did not contribute to the diagnosis. Calculation of local antibody production lacked diagnostic sensitivity when it was determined less than 3 weeks after the manifestation of clinical symptoms (28 of 49 patients [57%]), but this rose to 70% after an analysis of a second aqueous humor sample. The antibody avidity index attained diagnostic significance in only 8 of 43 instances (19%), and T. gondii DNA was amplified from no more than 6 of 39 (16%) aqueous humor samples. However, T. gondii-specific IgA was found within the aqueous humors of 11 of 43 patients (26%); measurement of the T. gondii-specific IgA level thus contributed substantially to the diagnostic sensitivity of the laboratory tests.

Ocular manifestations of systemic infections

Ocular involvement, mainly uveitis or retinochoroiditis, is common in various systemic diseases, such as endogenous endophthalmitis, Lyme disease, human T-cell lymphotropic virus type I infection, toxoplasmosis, and toxocariasis. Recent progress, especially in laboratory microbiologic testing, has enabled us to reliably diagnose many formerly idiopathic intraocular inflammatory diseases. A group of systemic infectious diseases, including those discussed here, are implicated as a body of emerging or re-emerging diseases that have appeared in the past two decades and are thought to have a close relation with global socioenvironmental changes. This paper discusses recent clinical and experimental studies of the most important systemic infectious diseases that affect the eye.

Serologic evaluation of patients with primary and recurrent ocular toxoplasmosis for evidence of recent infection

PURPOSE

To identify the frequency of recently acquired vs chronic systemic Toxoplasma gondii infections in patients with ocular toxoplasmosis.

METHODS

Serum samples from 22 patients with primary ocular toxoplasmosis (not from scars) and 42 patients with recurrent ocular toxoplasmosis were tested for the presence of anti-T. gondii IgM, IgG, and IgA antibodies and compared with samples from 24 patients with other causes of uveitis. Intraocular production of anti-T. gondii IgG and IgA, and the presence of T. gondii DNA was determined in patient s and control subjects from whom ocular fluid was available.

RESULTS

Serologic evidence of recently acquired infection was found for 11 (50%) of 22 patients with primary ocular toxoplasmosis and for one (2%) of 42 with recurrent ocular toxoplasmosis. In the uveitis control group, anti-T. gondii IgM antibodies could be detected in two (8%) of 24 patients, but anti-T. gondii IgA antibodies were not detectable. Patients with primary ocular toxoplasmosis and serologic markers of recently acquired systemic infection were significantly older than those with chronic infection (P = .008). Intraocular production of anti-T. gondii IgG was more frequently noted in patients with recurrent than primary ocular toxoplasmosis (81% vs 41%; P < .001), but intraocular T. gondii DNA was more frequently found in patients with primary ocular toxoplasmosis than in those with recurrent ocular toxoplasmosis (37% vs 4%; P < .01).

CONCLUSIONS

Primary ocular toxoplasmosis can be seen in either recently acquired or chronic T. gondii infection. Patients with ocular disease and recently acquired infection were older and more likely to have T. gondii DNA in intraocular fluids.

Intraocular inflammatory reactions without focal necrotizing retinochoroiditis in patients with acquired systemic toxoplasmosis

PURPOSE

To describe the occurrence of intraocular inflammatory reactions as the sole ophthalmic manifestation of acquired systemic toxoplasmosis.

METHODS

Review of medical records for 10 patients with uveitis and evidence of recent Toxoplasma gondii infection.

RESULTS

Patient ages ranged from 3 to 51 years. Ocular symptoms were present in each of eight adult patients. Inflammation was unilateral in nine patients; it manifested as vitreous humor cells and haze (10 patients), anterior chamber cells (seven patients), and retinal vasculitis (seven patients). No patient had necrotizing retinochoroiditis upon initial examination. Inflammation resolved in each of nine patients who had follow-up examinations. Foci of retinitis or inactive retinochoroidal scars were seen in four of these nine patients during follow-up examinations, at intervals of 2.0 weeks to 2.5 years after initial examination.

CONCLUSIONS

Retinal vasculitis and associated inflammatory reactions may be the only ophthalmic disorder during the early stages of a newly acquired T. gondii infection. Later development of retinitis or scars consistent with toxoplasmic retinochoroiditis in the same eyes suggests that the initial, isolated inflammation may be caused by the presence of parasites in retinal tissue. These cases may have implications for understanding the original source of retinal infection in patients who have recurrent toxoplasmic retinochoroiditis and for treatment of newly acquired T gondii infection.