Terson Syndrome in Patients with Aneurysmal Subarachnoid Hemorrhage: A 10-Year Single-Center Experience

BACKGROUND

Terson syndrome (TS), an intraocular hemorrhage associated with aneurysmal subarachnoid hemorrhage (aSAH), occurs in up to 46% of all patients with subarachnoid hemorrhage. Despite its high incidence, TS is underrepresented in the literature, and patients with aSAH are sometimes not systematically evaluated for the presence of TS in clinical practice. This work aims to raise awareness of TS, reevaluate previous scientific findings, describe risk factors associated with the occurrence of TS, and present our local diagnostic and treatment concept.

METHODS

All patients with aSAH treated at our institution between October 2010 and May 2020 were included in this retrospective study. The frequency of ophthalmological screening by indirect funduscopy, as well as the results, was investigated. In addition, the collection and statistical analysis of epidemiological and clinical data was performed using χ2, Kruskal-Wallis, and analysis of variance testing; multivariate regression; and receiver operating characteristic analysis. The significance level was set at p < 0.05.

RESULTS

A total of 617 patients were treated for aSAH in our institution. Of these, 367 patients (59.5%) were ophthalmologically examined for the presence of TS. The rate of TS in the examined patients was 21.3% (n = 78). Patients with TS had significantly higher Fisher and World Federation of Neurosurgical Societies (WFNS) scores (p < 0.0001). Regression analyses showed WFNS grade (p = 0.003) and the occurrence of seizures (p = 0.002) as independent predictors of TS, as did receiver operating characteristic analyses, which had a significant area under the curve of 0.66 for the combination of WFNS grade and seizures. For 12 (15.4%) patients, the TS had to be surgically treated by pars plana vitrectomy in a total of 14 eyes, which resulted in significant improvement of visual function in all patients: mean preoperative best-corrected visual acuity was 0.03 (± 0.08) versus 0.76 (± 0.21) postoperatively (p < 0.001).

CONCLUSIONS

TS is a common complication in patients with aSAH, affecting approximately one in five patients. A higher WFNS grade and the occurrence of seizures are associated with TS; therefore, screening for TS should be performed in these patients.

Case Report: Acute Vision Loss in a Young Returning Traveler with Dengue Fever

Ocular complications are rare in patients with dengue fever, but may cause permanent loss of vision. We present the case of a 29-year-old German woman who developed severe acute vision loss because of dengue-associated maculopathy after traveling to Vietnam and Cambodia. Initially, the optical coherence tomography showed detachment of the retinal pigment epithelium, a central shift in the retinal pigmentation and intraretinal cysts. The patient was hospitalized and treated with a short course of intravenous prednisolone. Vision improved, and the patient showed full recovery at 9 months after the onset. This case highlights the importance of awareness and adequate management for ocular involvement in patients with dengue fever, including travelers.

Prevalence of Signs and Symptoms of Pseudotumor Cerebri Syndrome Before and After Transsphenoidal Surgery for Cushing's Disease - A Prospective Consecutive Case Series

INTRODUCTION

Pseudotumor cerebri syndrome (PTCS) has anecdotally been described after successful treatment of Cushing's disease (CD), but the prevalence following transsphenoidal surgery has not been determined so far in a prospective study.

PATIENTS AND METHODS

41 consecutive adult CD patients were prospectively screened for signs and symptoms of PTCS, headache-related impairment, and ophthalmological features associated with intracranial pressure elevation before surgery and at follow-up (mean 4 months).

RESULTS

Biochemical remission was achieved in 36 of 41 (87.8%) patients after surgery. The most frequent preoperative complaints were visual acuity impairment (19 cases; 46.3%), headache (13 cases; 31.7%), and ear noise (9 cases; 22.0%). A significant reduction of visual disturbances was seen at follow-up. Overall, CD patients presented with fairly low headache-related emotional and functional restrictions before and after surgery. One of 34 (2.9%) patients with sufficient ophthalmological follow-up showed new-onset papilledema combined with temporary worsening of visual acuity and scotoma.

CONCLUSION

Our results suggest a very low frequency of signs and symptoms of PTCS after surgical treatment for CD in adults. This estimate is in line with previous outcomes from retrospective pediatric CD series. Further large-scale studies are needed to determine the actual prevalence of this condition following biochemical remission of CD.

Intraocular pressure during neurosurgical procedures in context of head position and loss of cerebrospinal fluid

OBJECTIVE

Perioperative visual loss (POVL) is a rare but serious complication in surgical disciplines, especially in spine surgery. The exact pathophysiology of POVL remains unclear, but elevated intraocular pressure (IOP) is known to be part of it. As POVL is rarely described in patients undergoing intracranial or intradural surgery, the aim of this study was to investigate the course of IOP during neurosurgical procedures with opening of the dura mater and loss of CSF.

METHODS

In this prospective, controlled trial, 64 patients fell into one of 4 groups of 16 patients each. Group A included patients undergoing spine surgery in the prone position, group B patients had intracranial procedures in the prone position, and group C patients were treated for intracranial pathologies in a modified lateral position with the head rotated. In groups A-C, the dura was opened during surgery. Group D patients underwent spine surgeries in the prone position with an intact dura. IOP was measured continuously pre-, peri-, and postoperatively.

RESULTS

In all groups, IOP decreased after induction of anesthesia and increased time dependently after final positioning for the operation. The maximum IOP in group A prior to opening of the dura was 28.6 ± 6.2 mm Hg and decreased to 23.44 ± 4.9 mm Hg directly after dura opening (p < 0.0007). This effect lasted for 30 minutes (23.5 ± 5.6 mm Hg, p = 0.0028); after 60 minutes IOP slowly increased again (24.5 ± 6.3 mm Hg, p = 0.15). In group B, the last measured IOP before CSF loss was 28.1 ± 5.0 mm Hg and decreased to 23.5 ± 6.1 mm Hg (p = 0.0039) after dura opening. A significant IOP decrease in group B lasted at 30 minutes (23.6 ± 6.0 mm Hg, p = 0.0039) and 60 minutes (23.7 ± 6.0 mm Hg, p = 0.0189). In group C, only the lower eye showed a decrease in IOP up to 60 minutes after loss of CSF (opening of dura, p = 0.0007; 30 minutes, p = 0.0477; 60 minutes, p = 0.0243). In group D (control group), IOP remained stable throughout the operation after the patient was prone.

CONCLUSIONS

This study is the first to demonstrate that opening of the dura with loss of CSF during neurosurgical procedures results in a decrease in IOP. This might explain why POVL predominantly occurs in spinal but rarely in intracranial procedures, offers new insight to the pathophysiology of POVL, and provides the basis for further research and treatment of POVL.German Clinical Trials Register (DRKS) no.: DRKS00007590 (drks.de).

Terson's syndrome - Pathophysiologic considerations of an underestimated concomitant disease in aneurysmal subarachnoid hemorrhage

Terson syndrome (TS) is a common and underestimated concomitant disease in patients suffering from subarachnoid hemorrhage (SAH). Aim of this study was to evaluate the influence of an initial unconsciousness and raised intracranial pressure (ICP) on the development of TS. We performed a retrospective analysis of 213 prospective collected SAH patients screened for TS to investigate the impact of an initial unconsciousness and raised ICP on the development of TS. A univariate analysis followed by a multivariate logistic regression model was performed to identify risk factors that are associated with TS. The findings are all discussed and correlated with the present pathophysiologic considerations of TS. The rate of TS in this study was 23.9%. A higher risk of TS in the univariate analysis was associated with a Glasgow Coma scale⩽7 (p=0.001), higher Hunt and Hess grade (p=0.001), Fisher grade IV (p=0.002), intracerebral hemorrhage (p=0.011), initial unconsciousness (p=0.013) and an ICP of ⩾25mmHg (p<0.001). An ICP of ⩾25mmHg was the only independent predictor for TS in the multivariate analysis (p=0.007). TS patients had a higher mortality (p=0.012) and a higher risk for a worse long-term outcome (p=0.002). Notable that 5 of 51 TS patients (9.8%) in this study developed TS with no raised ICP or initial unconsciousness. Terson syndrome is a common concomitant disease in SAH patients. The pathomechanism leading to TS is not exclusively related to raised ICP levels and/or unconsciousness. However, these factors may be associated with a high percentage of TS.

Diagnosis of Toxoplasma gondii infection after allogeneic stem cell transplant can be difficult and requires intensive scrutiny

Infectious complications remain a major problem after allogeneic hematopoietic stem cell transplant (HSCT). Specifically Toxoplasma gondii infection is a life-threatening condition in immunocompromised patients. In order to highlight the difficulties in obtaining an early and definitive diagnosis, we report three cases of toxoplasmosis after HSCT for hematologic malignancies: two cases of T. gondii retinochoroiditis, and one case of encephalitis. All patients had unrelated donors and received antithymocyte globulin; none had received trimethoprim/sulfamethoxazole prophylaxis. Toxoplasmosis occurred early post-transplant and diagnosis was obtained by real-time PCR. In one case, the correct diagnosis could only be established by PCR analysis of a retinal biopsy specimen. Rapid diagnosis--by invasive approaches--and an immediate onset of antiparasite treatment are crucial to avoid disseminated and often lethal Toxoplasma infections in the post-transplant period. Post-transplant prevention strategies and treatment to control advanced infection in this setting are discussed.

[Incidence of ocular manifestations in patients with histologically confirmed systemic sarcoidosis]

BACKGROUND

Intraocular findings in sarcoidosis were described by US studies with 35 % anterior uveitis, 25 % posterior uveitis and 20 - 30 % for late complications in case of first presentation. We report on the spectrum and diagnostic possibilities in 38 German patients.

PATIENTS AND METHODS

38 patients (68 eyes) aged 11 - 58 years (average 42.7 y), who suffered of intraocular manifestations in histological confirmed systemic sarcoidosis (1987 - 1997), were completely evaluated retrospectively. For additional diagnostic tools fluorescein angiography, optical coherence tomography, nuclear magnetic resonance tomography and measurements of angiotensin-converting enzyme, lysozyme and calcium in serum were performed.

RESULTS

15 patients (22 eyes = 32.4 %) had anterior uveitis: granulomatous keratouveitis (10 eyes), granulomas of the iris (6), granulomas of the trabecular meshwork (3) and 22 patients (42 eyes = 61.8 %) an intermediate and posterior uveitis: granulomatous perivasculitis (18 eyes), cystoid maculopathy (8), pars planitis (6), neuroretinitis (4), optic neuritis (3), choroiditis (3). Late complications in case of first presentation were found in 22 patients (39 eyes = 57.4 %): posterior synechiae 14 x, secondary glaucoma 10 x, cataracta complicata 8 x, optic atrophy 6 x, intraocular calcification 1 x.

CONCLUSION

Compared to previous studies with heterogeneous ethnic composition, intraocular inflammations with confirmed sarcoidosis in German patients show more than 60 % involvement of the posterior segment. We may speculate on the reasons for these discrepancies as being due to ethnic reasons, age and long-term follow-up. In case of typical ocular signs of sarcoidosis, treatment should be started immediately even without histological confirmation. In some cases histological confirmation is successful 8 years after first presentation.

Treatment of retinal arterial occlusion with local fibrinolysis using recombinant tissue plasminogen activator

OBJECTIVE

Retinal arterial occlusion is one of the most dramatic problems faced by ophthalmologists because of its sudden onset and the severe consequences it may have on the visual system. In this study, local intra-arterial fibrinolysis (LIF) using recombinant tissue plasminogen activator (rTPA) as a new technique for the treatment of retinal arterial occlusion was investigated.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Strict inclusion and exclusion criteria were used to select patients for treatment. Fifty-three patients with central retinal artery occlusion (n = 46) or branch retinal arterial occlusion (n = 7) were enrolled.

INTERVENTION

For a maximum of 3 hours, 10- to 20-mg rTPA per hour in 50-ml sodium chloride was infused transfemorally by catheterization of the ophthalmic artery with a variable stiffness microcatheter.

MAIN OUTCOME MEASURES

The best-corrected visual acuity for distance by an 18-line logarithmic table was measured on admission, at 24 hours, and at 3 months after intervention.

RESULTS

At 3 months, visual acuity had improved in 35 (66%) of 53 patients. Twenty-five (47.2%) patients showed an improvement of more than 2 lines, and in 10 (18.8%) patients, improvements of 1 to 2 lines were observed. No change in visual acuity occurred in 12 (22.6%) patients, and in 6 (11.3%) patients, the visual acuity deteriorated. The mean occlusion time was 14 hours (range, 3-50 hours). No statistically significant correlation was found between occlusion time and visual outcome (P > 0.22). In two patients, a temporary slight hemiplegia was observed during catheterization, and in one patient, a hypertensive crisis after LIF treatment was observed.

CONCLUSIONS

The high success rate of LIF using rTPA in patients suffering from retinal arterial occlusion is supposedly due to a causal effect of rTPA on primary platelet-fibrin emboli and secondary thrombi. The local fibrinolytic therapy with rTPA involves little risk for patients selected by strict inclusion and exclusion criteria. It may be used for the treatment of retinal arterial occlusion even later than 8 hours after the acute visual loss. However, a successful outcome of the therapy depends on the prompt referral by well-informed ophthalmologists; a speedy execution of all internal, neurologic, and ophthalmologic diagnostic measures; and a prompt therapy.

Coincidence of cytomegalovirus retinitis and central retinal vein occlusion in a patient with hemophilia B and AIDS

A 37-year-old man with hemophilia B, acquired immunodeficiency syndrome, and a unilateral cytomegalovirus retinitis developed a central retinal vein occlusion. This vascular complication occurred despite effective antiviral drug treatment with improvement of the fundus and despite decreased blood coagulability due to hemophilia B. Additional analyses of thrombophilic parameters did not reveal hints of systemic thrombophilia, suggesting that toxic and inflammatory effects of cytomegalovirus itself were responsible for the ophthalmologic aggravation.

[Intraocular pseudotumor in an AIDS patient. Block excision, differential diagnosis, histology]

BACKGROUND

Intraocular pseudotumors are a rare event in Aids patients and often pose diagnostic problems.

CASE REPORT

A 37-year-old patient who had had HIV seroconversion for 7 years was seen to developed progressively growing, multiple, disseminated, subretinal lesions OD > OS, accompanied by exudative retinal detachment and iritis. Since all etiological laboratory diagnostic efforts to detect an infectious, noninfectious and neoplastic systemic lesion failed, a diagnostic and curative therapeutic chorioretinal excisional biopsy specimen of the largest of the tumors (3 x 3 x 2 mm) was taken. The histological work-up demonstrated granulation tissue similar to an intraocular pseudotumor without signs of infection, malignancy or reactive lymphoid hyperplasia. This finding resulted in systemic corticosteroid treatment with complete resolution of the lesions in both eyes and no recurrences.

CONCLUSIONS

An invasive diagnostic procedure in patients suffering from lesions of unknown cause resulting in the institution of an appropriate medical treatment may be beneficial for the integrity and vision of the respective eye.

[Secondary prevention of cytomegalovirus retinitis with ganciclovir]

The prophylaxis of cytomegalovirus retinitis reactivation is effective in reducing the risk of blindness and in prolonging the remission interval and time of survival if given daily throughout life. In this study, a newly developed therapeutic regimen with 3 infusions a week was compared to the conventional maintenance therapy of 5 infusions a week using the same total weekly dose. For this purpose, ten patients were given 10 mg ganciclovir/kg 3 times a week (group A), and 18 received 6 mg ganciclovir/kg once daily for 5 days a week (group B). Only patients with newly diagnosed retinitis were included in this study. Both groups were comparable regarding their general health and ocular state at the beginning of the study. Induction therapy for stabilization of retinitis had to be given for 17.1 and 16.7 days (P = 0.785). Visual acuity was 0.5 and 0.7, respectively, at the beginning (P = 0.128) and 0.5 each at the end of the study (P = 0.875). Fifty-six percent of both groups presented with central retinal involvement at the beginning, whereas it was 56 and 78%, respectively, at the end (P = 0.250). The retinitis was found to have progressed more than 0.5 papilla diameters (pd) after 63.8 and 64.0 days (P = 0.996) and more than 1 pd after 117.6 and 77.8 days (P = 0.350). New induction therapy had to be performed after 147.9 and 131.5 days, respectively (P = 0.598). The maintenance therapy had to be interrupted due to side effects for 1.4 and 8.3 days, respectively (P = 0.185). According to these results, the prophylaxis of retinitis reactivation with 3 x 10 mg ganciclovir/kg per week is as effective as the established one with 5 x 6 mg/kg per week and can thus be recommended for an improvement in the quality of life for the patients concerned. No problems with this therapy were noted.

S-antigen: preparation and characterization of site-specific monoclonal antibodies

Previous attempts to prepare monoclonal antibodies (MAbs) against S-antigen, a photoreceptor cell protein involved in the visual process and a potent autoantigen for the induction of experimental autoimmune uveitis (EAU), have yielded MAbs which define only carboxyl terminal epitopes. In this study we devised alternate strategies to prepare five MAbs directed to other regions of the molecule. MAbC10C10 and MAbH11-A2 were prepared against synthetic peptides known to be uveitopathogenic and they were selected for more detailed studies. MAbC10C10 was generated against synthetic peptide BSA281-302 which contains a predictive consensus sequence for defined T cell epitopes (GIALD) as well as a consensus sequence for GTP-binding proteins. One human adenosine deaminase synthetic peptide containing an extensive amino acid sequence homology to BSA281-302 was a potent inhibitor of MAbC10C10 binding in a competitive inhibition radioimmunoassay. MAbH11-A2 was generated against peptide BSA303-332 which also contains a uveitopathogenic site. The binding site of MAbH11-A2 was determined to be within amino acid positions 305 to 314 (NLASSTIIKE) in S-antigen. This binding site corresponded closely to the binding site of an affinity-purified rat polyclonal antibody raised to human S-antigen. MAb5C6.47 was isolated from a mouse hyperimmunized with bovine S-antigen and was specific for a highly conserved sequence near the amino terminus, amino acid residues 42 to 48 (DGVVLVD). Both MAbC10C10 and MAb5C.47 were useful in screening gt11 cDNA libraries expressing S-antigen polypeptides as fusion proteins. Our results demonstrate the feasibility of producing site-specific MAbs potentially useful in the study of T cell-mediated immune mechanisms in EAU as well as in the phototransduction of vision.

Selection of antibody epitopes in an immunopathogenic neural autoantigen

Results with two well-characterized self-antigens, cytochrome c and myelin basic protein, have led to differing opinions regarding the predominant specificities of autoantibodies, whether regions of sequence diversity or 'structurally inherent features' of a protein determine favored antigenic sites. To further examine this question, 16 antibody epitopes have been mapped on a highly immunopathogenic autoantigen, retinal S-antigen (S-Ag). The epitopes were characterized for: (1) sequence diversity and cross-reactivity on S-antigens from several species; (2) conformational dependency; and (3) probability of their occurrence on the surface of S-antigen. A single C-terminal region containing sequence diversity was most frequently recognized, but no evidence for recognition of any other regions of sequence diversity was found. Thirteen of 16 monoclonal antibodies raised to native S-Ag bound epitopes strongly predicted to be on the surface of S-antigen. Conversely, only one of six antibody preparations raised to peptides or affinity-purified on peptides was found to recognize an epitope predicted to be on the surface, suggesting a good correlation between specificity for conformation-dependent sites and surface probability based on the surface prediction algorithm. Three of these six antibodies which preferred denatured epitopes bound sites which overlapped or coincided with T cell sites; two of these T cell sites are immunopathogenic. The epitopes recognized on denatured antigen and peptides were similar whether the antibodies were elicited with intact human or bovine S-antigen or with cyanogen bromide-cleaved peptides. Our data suggests that in the case of S-antigen, structural features are more significant factors in epitope selection than sequence diversity.

Identification of the main immunogenic region of retinal S-antigen: subordinate influence of MHC, IGH, species or strain differences on the specificity of the antibody response

The factors which lead to selection of dominant antigenic sites concentrated in discreet regions of proteins and polypeptides are important to the development of antigen-specific immunotherapies for autoimmune diseases and for vaccine design. In this study, the main immunogenic regions of the immunopathogenic autoantigen, retinal S-antigen, have been identified by examination of the specificity of antibody responses of different species. Using cyanogen bromide and synthetic peptides in western blots and the ELISA, the specificities of antisera from rabbits, guinea pigs, rats and 19 inbred strains of mice were tested. All animals produced high titers of antibody to S-antigen with the exception of PL/J mice. Antibodies which bound epitopes contained in peptide CB46, a 46 amino acid-containing peptide located at the C-terminus of S-antigen, were dominant in all species and strains tested. The epitopes in CB46 were multiple, overlapping, and concentrated in a stretch of approximately 30 residues. Two overlapping synthetic peptides from that region substantially competed the anti-CB46 response of all animals. Antibodies which recognized peptide CB47, a 47 residue peptide from the N-terminus, comprised the next most common group. This epitope was similar in all mice and overlapped the epitope defined by rat antibodies. All anti-CB47 antibodies mapped to an 11 residue region of CB47. Eleven strains of mice did not respond to CB47 after one immunization with S-antigen; however, multiple immunizations readily converted all animals so tested to CB47 responders. Rabbits and guinea pigs exhibited very weak responses to CB47 following one immunization; multiple immunizations increased the response minimally. Rats produced a strong antibody response to peptide CB123, which contains the known uveitogenic sites, while very little activity to CB123 was raised in rabbits and guinea pigs. Only 3 murine strains, LP, LP.R3, and B10.R3-71, responded with antibodies to CB123 and the epitope was mapped to a 30 residue region which in rats also contains two distinct pathogenic sites and an antibody epitope. Only rats and rabbits made antibody to the CB35 peptide; the epitopes were contained within an 18 residue sequence. The results show that a main immunogenic region is located in S-antigen near the C-terminus and is independent of species or MHC. Less dominant, species and strain-dependent immunogenic regions were found in three other areas, i.e. peptides CB47, CB123 and CB35.

Epitope mapping of bovine retinal S-antigen with monoclonal antibodies

We examined the binding of seven murine monoclonal antibodies raised to S-antigen, an immunopathogenic, 404 residue photoreceptor cell autoantigen which induces experimental autoimmune uveoretinitis. S-antigen has also been identified as arrestin, a protein involved in the regulation of phototransduction. One additional monoclonal antibody (C10C10), raised to a synthetic peptide (peptide N) corresponding to residues 281 to 302 in bovine S-antigen, was also studied. In preliminary studies we examined the specificity of the antibody response to bovine S-antigen in sera from Balb/c mice. Western blots of mouse sera on the cyanogen bromide digest of bovine S-antigen demonstrated that all animals produced antibody which recognized epitopes within the C-terminal cyanogen bromide peptide designated CB46. Mice of the H-2d haplotype, including the Balb/c strain often used to produce monoclonal antibodies, showed little activity to cyanogen bromide peptides other than CB46. Also, all seven of the monoclonals raised to S-antigen are specific for epitopes in the CB46 peptide. The epitopes recognized by the monoclonal antibodies could be grouped into four distinct sites defined by peptides AE-1 (A2G5), peptide AA (PDS-1), peptide 19-OV (A9C6), and peptide 199 (BDS-1,2,3 and 4). The mono-clonal antibody, C10C10, raised to peptide N recognizes an epitope in the N peptide and binds to a larger cyanogen bromide peptide designated CB123 as well as intact S-antigen. Fine mapping of these epitopes was done with various subpeptides. None of the antibodies bound the known immunopathogenic peptide, peptide M, which resides in CB123 although the C10C10 antibody binds a peptide adjacent to peptide M.

Assignment of several epitopes to cyanogen bromide peptides of bovine retinal S-antigen by immunoblotting with peptide-specific antibodies

Peptide fragments of bovine S-antigen, an immunopathogenic retinal autoantigen which mediates experimental autoimmune uveoretinitis, were produced by cyanogen bromide cleavage and used to study antibody-defined epitopes, primarily those defined by antibodies from Lewis rats immunized with the intact antigen or various peptide fragments purified from the digests by HPLC. Antibodies from the sera have been affinity-purified on several of the peptides and examined by western blot analysis and enzyme-linked immunosorbent assay on S-antigen, digests and purified fragments. By immunoblotting it could be shown that five of the purified peptides, CB46, CB47, CB67, CB74 and CB123 were immunogenic, eliciting antibodies which recognized the peptides to which they were prepared; all, except for CB67, elicited antibodies which also bound intact S-antigen. Two more peptides, CB14 and CB27 were not immunogenic and did not contain epitopes. An epitope was also found in CB35, a previously uncharacterized peptide. Using these procedures together with amino acid sequence and composition data, we have been able to determine the origins of the peptides which contain antibody epitopes, including those which we have previously determined to possess epitopes recognized by class II MHC-restricted T cell lines raised to S-antigen and several of the peptides. A T cell line specific for the non-uveitogenic CB47 peptide was unable to transfer the disease.

Preparation of overlapping peptides of bovine retinal S-antigen and their localization by immunoblotting with peptide-specific antibodies

Bovine retinal S-antigen was cleaved by three chemical cleavage procedures including o-iodosobenzoic acid (IBA), mile acid and cyanogen bromide. The resultant peptides were used to study antibody-defined epitopes. Treatment with IBA, which cleaves primarily at tryptophanyl peptide bonds, produced at least 4 major fragments and several minor fragments. The peptides have been identified by their migration on SDS-PAGE and tested for their immunoreactivity to several affinity-purified anti-CNBr-peptide antibodies and to affinity-purified anti-IBA peptide antibodies. The presence of a single tryptophan residue 194 residues from the amino-terminus should result in 2 fragments of approximately 23,000 and 26,000 molecular weight based on the known size of intact S-antigen. The additional fragmentation is due to the presence of acid labile bonds and cleavage at IBA-sensitive tyrosyl residues associated with a side reaction. Western immunoblots using affinity-purified antibodies against the various IBA and CNBr peptides have allowed location of these peptides within the intact molecule. Specifically, IBA23K and IBA21K are overlapping fragments on the carboxy end, mutally exclusive of all other peptides. IBA15K and IBA5.6K overlap, and IBA18K and IBA10K overlap within IBA26K which comprises the N-terminal half of S-Ag. Additionally, IBA10K contains an antibody epitope destroyed by CNBr cleavage of the methionyl residue between CB53 and CB56. Further characterization of these IBA peptides will expedite the location of possible additional uveitogenic epitopes in the amino-terminal half of S-Ag as well as epitopes lost by other peptide generating techniques.