Corneal changes in nine-banded armadillos with leprosy.

Leprosy is the third leading cause of blindness worldwide; however, little is known about the ocular changes that occur during the disease process. We have studied the eyes of two nine-banded armadillos with experimental Mycobacterium leprae infection by light and electron microscopy. Both animals had been inoculated intracutaneously, one 5 years and the other 2 years previously. Light microscopy revealed invasion by acid-fast bacilli which were seen in keratocytes and mononuclear phagocytes in all layers of the corneal stroma. In both animals, large macrophage granulomas were observed in the deep stroma, which was vascularized. Acid-fast bacilli were also were found in macrophages and vascular endothelial cells. By electron microscopy, numerous bacilli were found in the keratocytes, macrophages, and Schwann cells of myelinated and unmyelinated axons, and in the endothelial cells of blood vessels. The localization of M. leprae and the presence of inflammatory cells in the ocular tissue of both animals suggest that the bacilli reach the eye by the neural and/or vascular route. One animal showed much more extensive disease and bacillary yield than the other, indicating that ocular involvement may be independent of the generalized infection. Further studies of early ocular involvement in the armadillo and other animals could help to clarify the pathogenesis of this potentially blinding infection.

A microscopic study of herpes simplex virus retinopathy in mice.

ICR white mice were inoculated with herpes simplex virus (HSV) type I in the anterior chamber of one eye. Animals were killed at intervals of 2, 4, 6, 8, and 10 days and both eyes were obtained for light and electron microscopic study of retinal changes. HSV retinopathy developed in 42 (91%) of 46 inoculated eyes. Fourteen (88%) of sixteen noninoculated eyes examined after the sixth postinoculation day developed HSV retinopathy. The earliest signs of retinopathy in the inoculated eye were peripheral retinal vasculitis and inflammatory cells throughout the nerve fiber layer on day 2. No virus was found in retinal tissue until day 4, at which time disruption of outer retinal layers (outer nuclear layer and layer of rods and cones) was observed in the peripheral retina. The earliest signs of retinopathy in the noninoculated eye were isolated foci of outer retinal disruption in the posterior retina on day 6. The inflammation accompanying early retinal changes of HSV retinopathy were more severe in the inoculated eye. Electron microscopy of both eyes revealed viral particles in the inner nuclear and ganglion cell layers at the time of outer retinal disruption, but viral particles were seen only rarely in the outer retinal layers at this stage. Early disruption of normal retinal architecture may be due to infection and destruction of Muller cells. The retinopathy progressed in both eyes to total destruction of the retina by day 10. Viral infection of the retinal pigment epithelium occurred, but viral particles were seen only rarely in the underlying choroid. This model may be useful for the study of HSV retinopathy in humans.

Identifying HSV infected neurons after ocular inoculation.

ICR mice were inoculated intracamerally with McKrae strain herpes simplex virus (HSV) followed by intraperitoneal injection with 3H-thymidine. Infected mice were sacrificed after 3 or 4 days and the eyes, trigeminal ganglia (TG) and superior cervical ganglia (SCG) were embedded in glycol methacrylate, sectioned, and dipped for autoradiography. Light microscopy revealed silver grain labeling over neurons in the ipsilateral retina, TG and SCG of infected animals. No labeling of neurons was noted in the contralateral TG or SCG. Since the DNA of mature neurons does not replicate, we interpret these labeled neurons to represent cells with active replication of HSV. This technique allows the study of HSV infection of the nervous system with excellent tissue preservation. Furthermore, it may be used to distinguish those neurons with intrinsic viral synthesis from those harboring virus synthesized at a distant site with subsequent intracellular spread.

Surface features of the conjunctiva and cornea.

Guinea pig corneal and conjunctival surfaces were examined by transmission electron microscopy and cytochemistry. Some specimens of cornea and conjunctiva were examined morphologically; others were stained with ruthenium red or tannic acid before examination to enhance the detection of glycoproteins at cell surfaces. The epithelia were covered by microvilli and on the cornea also by microplicae. These surface projections were the shortest (150 nm) over the central cornea, and became progressively longer (approximately 300 nm) over the tarsal and fornical conjunctiva. There was a filamentous cell coat (glycocalyx) on the microvilli and microplicae that was best demonstrated in specimens stained with tannic acid. The glycocalyx extended approximately 300 nm from the tips and lateral surfaces of the microvilli and microplicae. Although there were slight local variations in its thickness, the maximum thickness of the cell coat was uniform over the cornea and conjunctiva. Heavy deposits at the cell surface after ruthenium red staining indicated that the cell coat contained many highly charged polyanions. The density of the ruthenium red stain obscured the fine structure of the filaments in the cell coat. The glycocalyx forms a scaffolding that is believed to bind mucus, with its content of immunoglobulins, by weak chemical interactions to the epithelial surface. Therefore, the microvilli, microplicae, and glycocalyx that were demonstrated in this study provide the structural framework that supports and binds a complex of related factors, including tears, mucus, and immunoglobulins, that have the common function of protecting the eye.

Stimulation of peroxidase by chlamydial infection: cytochemistry of guinea pig conjunctival epithelium.

Guinea pig inclusion conjunctivitis, a naturally occurring chlamydial disease of guinea pigs, resolves spontaneously after 3 to 4 weeks. The factors responsible for curbing the infection have not yet been specifically defined. Since Iwata (Invest. Ophthalmol. 15:297-301, 1976) reported cytochemical activity for peroxidase in the conjunctival epithelium of the normal rat, we undertook these studies to determine whether a similar activity exists in the guinea pig, and if so, whether it functions in the elimination of this Chlamydia psittaci infection. Tarsal conjunctivas of 14 normal guinea pigs, 34 infected ones, and 7 control guinea pigs (inoculated with yolk sac only) were excised and tested for peroxidase by the Graham and Karnovsky method (J. Histochem. Cytochem. 14:291-302, 1966). We found that peroxidase activity, virtually absent in normal animals, was intensely stimulated by the infection. This enzymatic activity appeared 2 days after inoculation of the conjunctiva with chlamydia and persisted for 6 to 7 weeks. The enzyme was localized in the rough endoplasmic reticulum and perinuclear cisternae of all layers of the conjunctival epithelium from the external surface to the basal lamina, including cells with no apparent inclusions as well as those heavily parasitized. Reaction in the Golgi complex was variable. No reaction, however, was ever evident in the chlamydial vacuoles or lysosomes, and the organisms continued to grow and multiply during peak enzymatic activity. We therefore concluded that the stimulated enzyme is apparently not directly responsible for the waning of the infection, but instead reflects an alteration of host metabolism that occurs as a consequence of the infection.

Herpesvirus in sensory and autonomic ganglia after eye infection.

In herpesvirus hominis (HVH) infections, virus harbored in the sensory ganglia is now thought to be the main source of recurrent infection at peripheral sites. Experimental HVH infection of the external eye in rabbits produces an acute infection and then latent infection of the trigeminal ganglion. In this study, acute infection of the automatic ganglia serving the eye (superior cervical and ciliary) as well as trigeminal ganglia occurred after HVH inoculation of rabbits' corneas with a herpes type 1 strain (RE). Latent virus infection was detected in the trigeminal ganglion of one of five animals tested six months after initial infection. Since the superior cervical and other autonomic ganglia serving the eye become infected during acute herpes simplex virus infection of the external eye in rabbits, it is possible that these ganglia are also sources of reinfection in recurrent herpetic disease of the eye. Following the initial eye disease with this virus strain, HVH shedding could not be demonstrated even after induction attempts by topically applied epinephrine or systemic use of cyclophosphamide. Thus, establishment of latent HVH infection in the ganglia and chronic shedding of virus into the external eye is not a constant feature of this animal model, but may depend on the specific strain of herpesvirus used.

Resistance to reinfection with a chlamydial agent (guinea pig inclusion conjunctivitis agent).

Although most chlamydial infections are chronic or recurrent, infection of the guinea pig's eye with guinea pig inclusion conjunctivitis (GPIC) agent induces a marked resistance to reinfection. To characterize this resistance to GPIC agent, we compared the disease and infection in previously infected guinea pigs with that in animals infected for the first time. In animals experiencing primary infection, even the lowest dose (10 egg-lethal doses [ELD50]) produced the disease and chlamydial inclusions in conjunctival smears, but the incubation period became progressively shorter with the highest inocula (10(4) and 10(5) ELD50). In animals with previous infection only these two highest inocula produced disease and infection, but the disease was short-lived, and replication of the agent was severely limited. The mechanism of this resistance may be due to secretory antibody in the tears, cellular immunity, or other local factors.

Herpes simplex eye infections: clinical manifestations, pathogenesis and management.

Herpes infection of the eye may be acquired as the patient's first exposure to the virus (primary infection) or as involvement of a new anatomical site (the eye) in a patient with previous HSV infection. In either case, patients with herpetic eye infection risk recurrent eye disease throughout their lives. The infective lesions of the corneal epithelium (dendritic and geographic ulcers) occasionally develop into noninfective indolent or trophic ulcers, particularly under the influence of cauterizing chemicals or corticosteroids. Inflammation of the corneal stroma may accompany herpetic epithelial lesions or occur independently. Stromal keratitis probably represents the host's immune response to viral antigens filtering down from epithelial lesions or from viral replication in stromal cells. The clinical manifestations of ocular HSV infection are reviewed, pathogenesis and possible pathways of the infection are analyzed, and some practical guidelines for management and prevention are presented.

Lattice corneal dystrophy.

The clinical and histologic aspects of 34 primary and six reoperative keratoplasties for lattice corneal dystrophy are evaluated. Surgical and postoperative complications were minimal and not considered specific for lattice corneal dystrophy. Visual results were highly favorable in a long-term evaluation. No lattice figures were seen to recur in any of the 34 primary or six reoperative grafts; however, opacities did occur in several grafts. Amyloid was definitely found in one reoperative graft specimen. A nonamyloid material was also found in the subepithelial and superficial stromal area in both the lattice dystrophy and reoperative specimens.