Vitreous fluorophotometric recordings in HIV infection

Bacillus cereus induces permeability of an in vitro blood-retina barrier

Most Bacillus cereus toxin production is controlled by the quorum-sensing-dependent, pleiotropic global regulator plcR, which contributes to the organism's virulence in the eye. The purpose of this study was to analyze the effects of B. cereus infection and plcR-regulated toxins on the barrier function of retinal pigment epithelium (RPE) cells, the primary cells of the blood-retina barrier. Human ARPE-19 cells were apically inoculated with wild-type or quorum-sensing-deficient B. cereus, and cytotoxicity was analyzed. plcR-regulated toxins were not required for B. cereus-induced RPE cytotoxicity, but these toxins did increase the rate of cell death, primarily by necrosis. B. cereus infection of polarized RPE cell monolayers resulted in increased barrier permeability, independent of plcR-regulated toxins. Loss of both occludin and ZO-1 expression occurred by 8 h postinfection, but alterations in tight junctions appeared to precede cytotoxicity. Of the several proinflammatory cytokines analyzed, only interleukin-6 was produced in response to B. cereus infection. These results demonstrate the deleterious effects of B. cereus infection on RPE barrier function and suggest that plcR-regulated toxins may not contribute significantly to RPE barrier permeability during infection.

Bacterial endophthalmitis: therapeutic challenges and host-pathogen interactions

Endophthalmitis is an infection of the posterior segment of the eye that frequently results in loss of vision. This devastating result occurs despite prompt and often aggressive therapeutic and surgical intervention. Over the past decade, research has centered on determining the bacterial and host factors involved in this potentially blinding disease. The initial focus on the bacterial factors responsible for intraocular virulence has recently expanded into analysis the inflammatory response to infection, including the molecular and cellular interactions between the pathogen and host. This review discusses the epidemiology and therapeutic challenges posed by endophthalmitis, as well as recent findings from the analysis of interactions between the host and pathogen. Based on these findings, a model for the pathogenesis of endophthalmitis is presented. A more comprehensive understanding of the molecular and cellular interactions taking place between pathogen and host during endophthalmitis will expose possible therapeutic targets designed to arrest the infection and prevent vision loss.

Intraocular crystals in HIV-related hypergammaglobulinemia

PURPOSE

To describe the occurrence of bilateral iris and retinal crystals in a patient with benign HIV-related gammopathy.

DESIGN

Observational case report.

METHODS

A 45-year-old HIV-positive male with a known, benign hypergammaglobulinemia was referred for routine ophthalmic assessment because of right ophthalmic zoster.

RESULTS

Ophthalmoscopic examination revealed the presence of bilateral, multiple, refractile iris and macular crystals. No other signs of uveitis or stigmata of HIV were found.

CONCLUSION

Intraocular crystals are a rare finding, usually seen in chronic uveitis with or without hypergammaglobulinemia. This finding has not been previously described in non-inflamed eyes, nor as an ocular manifestation of HIV. We hypothesize that HIV-related disruption of the blood-aqueous and blood-retinal barriers allows intraocular immunoglobulin deposition in patients with hypergammaglobulinemia.

Permeability of the blood-retinal barrier in healthy humans. European Concerted Action on Ocular Fluorometry

BACKGROUND

The aim of this study was to compare the inward permeability of the blood-retinal barrier in healthy subjects from six European cities.

METHODS

Seventy-two healthy subjects (age 20-70 years) were selected. At 30 min and 60 min after fluorescein injection, fluorescein mass in vitreous was calculated from the concentrations measured along the optical axis of the eye. Non-protein-bound fluorescein (NPBF) concentrations were measured in plasma prepared from blood samples taken 7, 15 and 55 min after injection. Blood-retinal barrier permeability (PBRB) was calculated from the vitreous fluorescein mass and the time integral of NPBF and was corrected for the autofluorescence of ocular tissue and for lenticular light transmittance.

RESULTS

Mean PBRB values +/- SD (nm.s-1) were 2.07 +/- 0.54 (Coimbra), 2.01 +/- 0.43 (Frankfurt), 2.24 +/- 0.50 (Ghent), 2.37 +/- 0.56 (Herlev), 1.89 +/- 0.44 (Leiden) and 1.74 +/- 0.38 (Porto). Differences between centers were not significant (P > 0.35). Measurements were reproducible and independent of the time after fluorescein injection (P > 0.50). A PBRB higher than 3.16 nm.s-1 or a value which had increased by 32% was considered abnormal (P < 0.05).

CONCLUSION

PBRB values were similar in all centers. The results demonstrate that this is a highly sensitive and reliable method for measuring the permeability of the blood-retinal barrier.

Elevation of laser flare photometry in patients with cytomegalovirus retinitis and AIDS

PURPOSE

To investigate an alteration of the blood-ocular barriers by laser flare photometry in patients with acquired immunodeficiency syndrome (AIDS) diagnosed with cytomegalovirus retinitis.

METHODS

Serial laser flare photometry measurements from 31 eyes of 31 patients with AIDS and newly diagnosed cytomegalovirus retinitis were compared with measurements from 31 control patients with AIDS but without documented eye disease. Location and extent of retinitis, presence of visual symptoms, and CD4 lymphocyte counts were also compared with laser flare photometry readings.

RESULTS

Laser flare readings (mean +/- SE) were significantly higher in eyes with (13.0 +/- 1.5 photon counts per msec) than without cytomegalovirus retinitis (4.9 +/- 0.3 photon counts per msec) (P < .001). Lesions within the arcade vessels resulted in significantly higher laser flare photometry readings (17.3 +/- 2.5 photon counts per msec) compared with peripheral retinitis (9.8 +/- 1.5 photon counts per msec) (P = .01). A significant correlation was found between area of involvement of peripheral retinitis and laser flare photometry readings (P = .008). Readings in patients without cytomegalovirus retinitis increased significantly 10 months after the first measurement (9.5 +/- 1.9 photon counts per msec) (P = .04). Readings in patients with cytomegalovirus remained elevated 3 months after successful treatment of retinitis (12.3 +/- 2.3 photon counts per msec) (P = .6).

CONCLUSIONS

Laser flare photometry readings are significantly elevated in eyes with cytomegalovirus retinitis, suggesting a breakdown of the blood-ocular barriers. Increasing laser flare photometry readings over time in patients without known ocular disease suggests that HIV infection may cause progressive breakdown of the blood-ocular barrier.

Evidence for breaches of the retinal vasculature in acquired immune deficiency syndrome angiopathy. A fluorescent microsphere study

PURPOSE

The author studied the retinal vasculature in patients with acquired immune deficiency syndrome (AIDS) by infusion of microspheres impregnated with fluorescent dye.

METHODS

Experimental study of the structural integrity of the retinal microvasculature in 14 autopsy patients with AIDS was compared with age- and gender-matched control retinas.

MATERIALS

Fourteen autopsy eyes from patients with AIDS, eight autopsy eyes from immunosuppressed control patients, and four autopsy eyes from nonimmunosuppressed control patients were studied.

EXPERIMENTAL METHOD

The central retinal arteries of autopsy eyes were perfused with fluorescent microspheres of 10 and 200 nm in diameter. The retinas were dissected from the eyes and viewed by fluorescence microscopy.

RESULTS

Vascular breaches permeable to 200-nm microspheres were discovered in eyes from patients with AIDS. Ruptured microaneurysms were identified at the center of retinal hemorrhages in 7 of 14 eyes from patients with AIDS and 5 of 8 immunosuppressed control eyes. Leakage around microaneurysms occurred even in the absence of hemorrhage and were more frequent in eyes from patients with AIDS (11/14) than in control eyes (3/12). Cotton wool patches were surrounded by tortuous retinal vessels and microaneurysms.

CONCLUSIONS

Ruptured microaneurysms are a frequent cause of retinal hemorrhage in immunosuppressed patients. Breaches in microaneurysms occur even in the absence of hemorrhage. These breaches are often at least 200 nm in diameter, a size that is permissive to capsids and virions of cytomegalovirus (CMV). Ruptured and/or leaky microaneurysms are potential sources of CMV permeation of the blood-retinal barrier. Breaches of the retinal microvasculature are not specific to patients with AIDS and occur frequently in other immunosuppressed patients.

Effect of vitreous fluidity on the measurement of blood-retinal barrier permeability using contrast-enhanced MRI

Breakdown of the blood-retinal barrier (BRB), frequently an early clinical sign in retinopathy, can be accurately determined using contrast-enhanced MRI. However, increased vitreous fluidity with age and disease may affect the accuracy of the MRI method. We compared the permeability surface area product per area of leaky retina in eyes with normal vitreous (5.42 +/- 0.48 x 10(-4) cm/min, mean +/- SEM, n = 5) to the contralateral gas-compressed vitrectomized eyes (5.41 +/- 0.54 x 10(-4) cm/min, n = 5). The effect of vitrectomy was not significant (P = 0.325) using a Wilcoxon matched pairs signed rank test on the signed differences of the PS' values.