Download A microscopic study of herpes simplex virus retinopathy in mice.

A Microscopic Study of Herpes Simplex Virus
Retinopothy in Mice
Gary N. Holland, Birgirro I. Togni, Odeon C. Driones, and Chandler R. Dawson
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. Invest Ophthalmol Vis Sci 28:1181-1190, 1987
the contralateral eye is due to the presence of viral
infection.2"4 Many studies of this model have focused
on the route by which virus spreads from the inoculated to the noninoculated eye; evidence suggests a
neural route of viral transmission, either through
axoplasmic transport5 or cell-to-cell spread involving
the neuroglia.6 Whether virus crosses to the contralateral side at the optic chiasm or elsewhere within the
central nervous system remains a subject of controversy. Recent investigations have used the model to
study immune responses to intraocular herpetic infections.7 Retinal infection results in severe, fullthickness necrosis, but little is known about the structural events occurring during retinal destruction.
In this study, retinal disease following anterior
chamber inoculation of HSV in one eye was investigated further by light and electron microscopy to
study the early morphologic changes that occur in the
retina and the distribution of virus-infected cells.
Continued investigation of this model may provide
insights into pathogenesis of HSV retinopathy in
humans.
In 1924, von Szily demonstrated that inoculation
of herpes simplex virus (HSV) into a ciliary body
dialysis cleft of one eye in rabbits leads to uveitis and
retinopathy in the contralateral, noninoculated eye.1
Disease is also produced in the contralateral eye when
virus is inoculated into the anterior chamber or vitreous body.2 A similar phenomenon can be demonstrated in mice.3
Originally intended for use in the study of sympathetic ophthalmia, the von Szily model and its modifications have subsequently been used by numerous
investigators as a tool for the study of herpetic eye
disease. It has been established that retinal disease in
From the Francis I. Proctor Foundation for Research in Ophthalmology, University of California, San Francisco, California.
Dr. Holland is currently at the Jules Stein Eye Institute, UCLA
Medical Center, Los Angeles, California.
Presented in part at the Annual Meeting of the Association for
Research in Vision and Ophthalmology, Sarasota, Florida, April
30, 1984.
Supported in part by grant EY-03917 from the National Institutes of Health. Dr. Holland was the recipient of a Heed Foundation Fellowship.
Submitted for publication: May 7, 1986.
Reprint requests: Chandler R. Dawson, MD, Francis I. Proctor
Foundation, S-315, University of California, San Francisco, CA
94143.
Materials and Methods
Eighty-six adult ICR outbred white mice of both
sexes were studied. Mice were obtained from Simon-
1181
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
1182
Vol. 28
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / July 1987
Table 1. Disease characteristics*
Days poslinoculation
Day 2
Day 4
Day 6
N
Presence of virus in the AC
Presence of virus in the retina
Inflammation in the AC
Inflammation in the retina
Retinal destruction
3+
0
3+
1+
0
0
0
0
0
0
3+
2+
3+
2+
2+
* 0 = not present. 1+ = mild in degree, few in number, or characteristic
present in minority of specimens. 2+ = moderate in degree or number, or
characteristic present in majority of specimens. 3+ = severe in degree, many in
sen Laboratories (Gilroy, CA). Pools of RE strain
HSV type I were propagated in Vero cells and stored
at-70°Cin 1-ml aliquots.
Prior to virus inoculation, mice were anesthetized
with a 0.02 ml intramuscular injection of a 1:1 mixture of xylazine (20 mg/ml) and ketamine (100
mg/ml). A 27-gauge needle was used to make an incision at the limbus of the left eye of each mouse
under microscopic visualization. A glass micropipette was placed through the limbal incision and 103
plaque-forming units (PFU) of virus in 1 ix\ were introduced into the anterior chamber through a pipette
attached to a Hamilton syringe. Following inoculation, the pipette was removed slowly to minimize
leakage of fluid from the eye.
Animals were examined serially with a portable slit
lamp for changes in corneal clarity, keratic precipitates, anterior chamber inflammation and hemorrhage, synechiae formation, and periocular inflammation. Retinas were not examined clinically.
Animals chosen randomly from survivors were
killed and their eyes were enucleated for microscopic
examination on postinoculation days 2, 4, 6, 8, and
10. Selection was not based on the presence or absence of clinically-apparent ocular or neurologic disease. Both eyes from a total of 46 animals were obtained.
Following enucleation the eyes were immediately
placed in 3% glutaraldehyde with 0.1% sodium cacodylate buffer at pH 7.4. Twenty-four hr later each eye
was bisected. One-half were dehydrated and embedded in DuPont-Sorrall resin (Fischer Scientific, Pittsburg, PA) for light microscopic examination. The remaining half were postfixed in 2% osmium tetroxide
in Palade's buffer, pH 7.4, for 2 hr, stained in Kellenberger's uranyl acetate, dehydrated in ethanol, and
embedded in araldite for electron microscopy.
All enucleated eyes were examined by light microscopy, in 2-jum sections stained with Giemsa stain or
Lee's stain (basic fuchsin and methylene blue). Se-
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
0
0
0
0
0
Day 8
N
N
3+
3+
3+
3+
3+
0
2+
1+
2+
2+
2+
2+
3+
3+
3+
0
3+
1+
2+
3+
number, or characteristic present in all specimens examined.
11 = inoculated eye.
% N = noninoculated eye.
lected ocular lesions were studied by electron microscopy, in thin sections cut on a Sorvall MT-5000 ultramicrotome (Research Manufacturing Corp., Tucson, AZ) and stained with uranyl acetate and lead
citrate. Specimens were examined on a Siemens 1A
electron microscope operating at 80 kv.
This study conformed to the ARVO Resolution on
the Use of Animals in Research.
Results
Table 1 summarizes the relative changes in various
disease characteristics observed microscopically in inoculated and noninoculated eyes through postinoculation day 8.
By day 2 all animals were found to have signs of
herpetic disease in the inoculated eye by slit-lamp
examination. Disease manifestations included periocular swelling, corneal clouding and infiltration, anterior chamber reaction, and posterior synechiae.
Light microscopic examination revealed numerous
inflammatory cells, primarily polymorphonuclear
leukocytes (PMN), and a proteinaceous exudate in
the anterior chamber. PMN also were present in the
iris and ciliary body and were adherent to the cornea,
and there was extensive loss of corneal endothelial
cells.
Twelve (92%) of thirteen inoculated eyes examined
by light microscopy on day 2 had retinal disease. Inflammatory cells were present in the nervefiberand
ganglion cell layers throughout the retina (Fig. 1).
Vasculitis, characterized by PMN infiltration of superficial retinal vessel walls, was present in the peripheral retina. By electron microscopy, HSV particles were identified in nuclei of iris and ciliary body
cells and in remaining corneal endothelial cells of
inoculated eyes. Despite the presence of inflammatory cells in the nerve fiber and ganglion cell layers,
examination of several eyes failed to reveal viral particles in the retina.
No. 7
HERPES SIMPLEX VIRUS RETINOPATHY IN MICE / Holland er ol.
There were no retinal changes or inflammatory
cells in noninoculated eyes examined on day 2.
On day 4, all inoculated eyes examined had anterior segment and retinal disease. Examination revealed PMN in corneal stroma, iris, ciliary body, and
anterior chamber. Numerous inflammatory cells,
primarily PMN, were present in the vitreous and in
the retina between the nerve fiber and outer plexiform layers; both posterior and peripheral retina were
involved. Occasional PMN were located in the outer
nuclear layer and photoreceptor (rod and cone) layer.
Vasculitis was noted in the peripheral retina, and foci
of outer nuclear layer disorganization were seen in
the peripheral retina. Nuclei from this layer had
moved into the photoreceptor layer, giving the appearance of photoreceptor layer "collapse." There
was nuclear enlargement with margination of chromatin in ganglion cells overlying these areas. By electron microscopy, HSV particles were identified in the
Fig. 2. Light micrograph of inoculated eye, day 6. Peripheral
retina shows extensive full thickness necrosis. Remaining ganglion
cells show margination of chromatin, characteristic of HSV-infected cells (black arrow). The choroid is thickened with inflammatory cells (white arrow) (X175).
Fig. 1. Light micrograph of inoculated eye, day 2, shows polymorphonuclear leukocytes in the vitreous (open arrow) and
densely infiltrating the nerve fiber layer (white arrow) and ganglion
cell layer (black arrow). There are no alterations in the normal
architecture of the retina (X500).
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
peripheral retina. Virus was primarily located in the
ganglion and inner nuclear layers, and was found
only rarely in the outer nuclear layer and in retinal
pigment epithelium.
There was no light microscopic evidence of disease
in noninoculated eyes on day 4. Electron microscopic
examination of several specimens failed to reveal any
viral particles in retinal tissue.
By day 6 there was extensive disruption of normal
retinal architecture in inoculated eyes (Fig. 2). In
many specimens nuclear layers could no longer be
distinguished, and nuclei were found immediately
adjacent to the retinal pigment epithelium. HSV particles were identified throughout the retina (Fig. 3)
and in retinal pigment epithelial cells. There was a
marked inflammatory reaction in the choroid, but no
viral particles were found in choroidal tissue on examination of several specimens by electron microscopy.
1184
INVESTIGATIVE OPHTHALMOLOGY G VISUAL SCIENCE / July 1987
Vol. 28
Pig. 3. Inoculated eye. day 6. Ganglion cell with intranuclear viral particles (solid arrow) (X6.000). Insert shows viral particles from same
cell (XI 14.000). Adjacent vessels shows normal endothelium without viral infection (open arrow).
Ocular disease was observed first in noninoculated
eyes on day 6, when two (20%) often animals developed evidence of anterior chamber inflammation on
slit-lamp examination. Signs of anterior segment inflammation in noninoculated eyes were never as severe as those in inoculated eyes. Clinical examination
was found to accurately predict the presence or absence of inflammatory cells in anterior segment
structures on subsequent microscopic examination.
PMN were present in iris, ciliary body, and anterior
chamber, but there were no cellular changes on light
microscopy to suggest viral infection of these tissues,
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
and examination of several specimens failed to reveal
the presence of viral particles. No animal had anterior
segment inflammation without having retinopathy
on microscopic examination. Conversely, seven
(33%) of twenty-one animals subsequently found to
have retinopathy in the noninoculated eye had no
signs of anterior uveitis.
Seven (70%) of ten noninoculated eyes examined
by light microscopy had retinal changes on day 6.
Isolated foci of photoreceptor layer collapse and
outer nuclear layer disruption were seen in the posterior retina (Fig. 4). The inner nuclear and ganglion
No. 7
HERPES SIMPLEX VIRUS RETINOPATHY IN MICE / Holland er ol.
cell layers overlying these foci were intact, although
ganglion cell nuclei were enlarged with marginated
chromatin. A few PMN were present within the foci
of outer nuclear layer disruption, and in the nerve
fiber layer and vitreous overlying these foci. Viral
particles were present in nuclei of the ganglion and
inner nuclear layers (Figs. 5,6), and Muller cell nuclei
were infected in all specimens. Enveloped and naked
viral particles were present in the nerve fiber layer,
but viral particles were found only rarely in the outer
nuclear and photoreceptor layers in areas of photoreceptor layer collapse (Figs. 7,8).
By day 8 there was severe necrosis of the entire
retina in all inoculated eyes, and retinal cells could no
longer be identified. Inflammatory cells were present
in the necrotic retina and in the choroid. Virus was
identified only occasionally in necrotic retina by
electron microscopy. In one eye viral particles were
seen in a choroidal macrophage, but examination of
several other specimens failed to reveal virus in choroidal tissue.
Of seven surviving animals examined on day 8, five
(71%) had anterior segment disease in the noninoculated eye. All eyes examined by light microscopy had
retinal disease. There was extensive disruption of the
retina (Fig. 9), and nuclear layers could no longer be
distinguished in many sections. Scattered PMN were
present. Infiltrates were not as dense as in areas of
comparable disease severity in inoculated eyes, however, and there was little inflammation in the choroid. By electron microscopy viral particles were
identified throughout the retina and in the retinal
pigment epithelium.
The majority of animals developed encephalitis by
day 6. Few animals survived to day 10. Of nine surviving animals, six (67%) had ocular disease in inoculated eyes. Disease was bilateral in four (44%). Retinal
disease developed in the noninoculated eye, without
development of retinopathy in the inoculated eye, in
three (33%). In noninoculated eyes, the retina consisted of necrotic debris and scattered inflammatory
cells. Retinal pigment epithelium was swollen in
many areas, and Bruch's membrane remained intact.
Choroidal vessels were dilated and many PMN were
present in the choroid. By electron microscopy, occasional viral particles were present in the retina and
retinal pigment epithelium (Fig. 10), but no virus was
located in the choroid on examination of several
specimens.
Discussion
The von Szily model provides a reliable method for
the production of acute HSV retinopathy in animals.
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
1165
Fig. 4. Light micrograph of noninoculated eye, day 6. Disruption
of the outer nuclear layer with collapse of nuclei into the photoreceptor layer (white arrow) identifies an early focus of HSV retinopathy. Ganglion cells overlying the focus of collapse have marginated chromatin, characteristic of HSV infection (black arrow)
(X500).
The high incidence of infection and the consistency
of retinal findings make it an excellent model for the
study of early retinal disease.
In the study presented here, most animals developed retinopathy in both eyes. In other recent reports
of this model, however, retinopathy developed only
in contralateral (noninoculated) eyes.34-7 Animal
species and virus strain differences have been shown
to influence the severity and spectrum of herpetic
disease in mice.8'9 In this study the highly susceptible
ICR strain of mice may account in part for differences in retinal disease when compared with other
studies. Whittum-Hudson et al hypothesize that cellmediated immune mechanisms protect inoculated
1186
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / July 1987
Vol. 28
Fig. 5. Noninoculated eye, day 6, showing viral particles within ganglion cell (GC) nuclei (open arrow) and complete virions in the nerve
fiber layer (NFL) (solid arrows) (XI8,800). Insert shows viral particles from the same specimen (X58,OOO).
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
No. 7
1167
HERPES SIMPLEX VIRUS RETINOPATHY IN MICE / Holland er ol.
i*
Fig. 6. Noninoculated
eye, day 6. Angulated nucleus in the inner nuclear
layer, characteristic of
Muller cells, containing
viral particles (arrows)
(X 14,000).
eyes against retinopathy.7 In this study, sparing of the
retina in the inoculated eye was seen only among
animals surviving to day 10. In the genetically heterogeneous population of mice used, perhaps only those
animals most resistant to fatal infection were able to
mount an immune response that protected the retina.
This study concentrated on the early morphologic
events surrounding retinal infection with HSV. In
both eyes disruption of the outer nuclear and photoreceptor layers was the initial manifestation of retinal
infection; similar changes have been reported in the
retinas of rabbits given intravitreal inoculation
ofHSV."1
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
While the detection of HSV in tissues by transmission electron microscopy is a relatively insensitive
technique, it does provide precise information on the
types of cells infected. During the early stages of infection, virus was not detected where the retina still
retained its normal architecture. In areas where outer
nuclear layer disruption and photoreceptor layer collapse was observed, viral particles were found in all
layers of the retina. Muller cells and ganglion cells
were consistently infected, but cells in the outer retinal layers were rarely infected, despite extensive early
disruption of their normal architecture. The localization of virus in the inner retinal layers with sparing of
1188
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / July 1987
Vol. 28
Fig. 7 (/<'//). Noninoculated eye. day 6. Intranuclear viral particles are demonstrated in the outer nuclear layer (arrows) (XI 5.300). Virus in
the outer retina, as demonstrated here, is unusual.
Fig. 8 (rijilu). Same eye as Fig. 7. Viral particle adjacent to photoreceptor (X83.000).
the outer layers was also observed by Pettit et al using
immunofluorescence.2 Studies in vitro by Politi et al
have shown a differential susceptibility of various retinal cells to HSV infection"; photoreceptor cells appeared to be resistant to infection in that study.
It is probable that the early disruption of the outer
nuclear and photoreceptor layers is caused by infection of Muller cells, the supporting neuroglia of the
retina.12 As with other central nervous system neuroglia, the entire surface of Muller cells appears to be
highly susceptible to HSV attachment and penetration. Neurons are susceptible only at the synaptic
endings, but are resistant on the perikaryon.13-14 It is
hypothesized that in this animal model, virus reaches
the retina via retrograde transport in axons of the
optic nerve to produce infection of ganglion cell nuclei. Virus released from ganglion cells is then taken
up by Muller cells, the destruction of which leads to
the early disruption of the outer retinal layers. Virus
can then spread throughout the retina to infect both
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
synaptic nerve endings and other contiguous Muller
cells.
Muller cell processes also form the inner and outer
limiting membranes of the retina. The internal limiting membrane would be the first retinal tissue encountered by virus diffusing posteriorly from the anterior chamber of inoculated eyes, thus explaining
early disruption of the peripheral retina.
Inoculated eyes consistently developed a greater inflammatory response than noninoculated eyes. In inoculated eyes. PMN were seen throughout the inner
layers of the retina preceding herpetic infection of
retinal cells. The lack of viral particles and the presence of peripheral retinal vasculitis suggests that the
early inflammatory response may have been produced by local spread of immune mediators from the
inflamed anterior segment. In contrast, noninoculated eyes developed a milder inflammatory reaction
only in areas of retinal disruption; nevertheless, retinal necrosis followed a similar course in both eyes. It
No. 7
HERPES SIMPLEX VIRUS RETINOPATHY IN MICE / Holland er ol.
is therefore likely that the inflammatory response did
not play a major role in retinal destruction in the
noninoculated eye.
The von Szily model may prove to be useful for the
study of human HSV retinopathy. Because it is free of
injection artifact, and because virus reaches the eye
by an endogenous route, the noninoculated eye may
be a useful model of HSV infection of the retina in
humans, which also results in severe retinal necrosis. l5~19 As in the mouse model, HSV has been
found more frequently in the inner layers of the retina and in the retinal pigment epithelium of these
human cases.1516 Cibis and Flynn found marginated
chromatin, inclusion bodies and virus particles primarily in the ganglion cell and inner nuclear layers of
an 18-month-old infant with HSV encephalitis.17 In
adult patients with HSV retinopathy, Minckler et al
observed that maximum necrosis occurred in the
inner retina,18 and Johnson and Wisotzkey found
Cowdry type A eosinophilic intranuclear inclusions
in ganglion cells, but few inclusions in outer retinal
layers.19 These findings are consistent with the observed distribution of HSV in this animal model. In
contrast to very early degeneration of photoreceptors
in this model, however, Minckler et al found areas of
photoreceptor layer preservation in their patient.18
Specimens of human HSV retinopathy have not been
examined during very early stages of disease; most
human tissue becomes available only after wide-
1189
*
•
•
•
Fig. 9. Light micrograph of noninoculated eye, day 8, showing
extensive disruption of retinal architecture. There is widespread
collapse of the outer nuclear layer into the photoreceptor layer.
Inner limiting membrane and nerve fiber layer cannot be identified. There is little choroidal infiltration (X500).
Fig. 10. Noninoculated eye, day 10. Intranuclear particles are seen in a retinal pigment epithelium (PE)cell. Bruch's membrane is intact (B).
No virus was seen on examination of the choroid (C) (XI 3,700).
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
1190
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / July 1987
spread destruction of the retina has occurred, which
emphasizes the need for an appropriate animal model
for research.
Key words: herpes simplex virus, mice, Muller cell, retinopathy, von Szily model
References
1. von Szily A: An experimental endogenous transmission of infection from bulbus to bulbus. Klin Monatsbl Augenheilkd
75:593, 1924.
2. Pettit TH, Kimura SJ, Uchida Y, and Peters H: Herpes simplex uveitis: An experimental study with the fluorescein-labeled antibody technique. Invest Ophthalmol 4:349, 1965.
3. Whittum JA, McCulley JP, Niederkorn JY, and Streilein JW:
Ocular disease induced in mice by anterior chamber inoculation of herpes simplex virus. Invest Ophthalmol Vis Sci
25:1065, 1984.
4. Atherton SS and Streilein JW: Insights into HSV-1 retinitis
from molecular virology: Evidence that virus spreads from
injected to uninjected eye via the central nervous system.
ARVO Abstracts. Invest Ophthalmol Vis Sci 25(Suppl):l 17,
1984.
5. Kristensson K, Ghetti B, and Wisniewski HM: Study on the
propagation of herpes simplex virus (type 2) into the brain after
intraocular injection. Brain Res 69:189, 1974.
6. Narang HK and Codd AA: Progression of herpes encephalitis
in rabbits following the intraocular injection of type 1 virus.
Neuropathol Appl Neurobiol 4:457, 1978.
7. Whittum-Hudson J, Farazdaghi M, and Prendergast RA: A
role for T lymphocytes in preventing experimental herpes
simplex virus type 1-induced retinitis. Invest Ophthalmol Vis
Sci 26:1524, 1985.
8. Stulting RD, Kindle JC, and Nahmias AJ: Patterns of herpes
Downloaded From: http://iovs.arvojournals.org/ on 06/11/2017
Vol. 28
simplex keratitis in inbred mice. Invest Ophthalmol Vis Sci
26:1360, 1985.
9. Daigle J, Chung H, Opremcak EM, and Foster CS: Strain
specific susceptibility to intracameral HSV-1 challenge in
inbred strains of mice. ARVO Abstracts. Invest Ophthalmol
VisSci27(Suppl):115, 1986.
10. Oh JO: Primary and secondary herpes simplex uveitis in rabbits. Surv Ophthalmol 21:178, 1976.
11. Politi LE, Adler R, and Whittum-Hudson J: Differential sensitivity of retinal neurons and photoreceptors to herpes simplex
infection. ARVO Abstracts Invest Ophthalmol Vis Sci
27(Suppl):125, 1986.
12. Hogan MJ, Alvarado JA, and Weddell JE: Histology of the
Human Eye. Philadelphia, WB Saunders Co, 1971, pp. 461-8.
13. Kennedy PGE, Clements GB, and Brown SM: Differential
susceptibility of human neural cell types in culture to infection
with herpes simplex virus. Brain 106:101, 1983.
14. Vahlne A, Nystrom B, Sandberg M, Hamberger A, and Lycke
E: Attachment of herpes simplex virus to neurons and glial
cells. J Gen Virol 40:359, 1978.
15. Pepose JS, Kreiger AE, Tomiyasu U, Cancilla PA, and Foos
RY: Immunocytologic localization of herpes simplex type 1
viral antigens in herpetic retinitis and encephalitis in an adult.
Ophthalmology 92:160, 1985.
16. Pepose JS, Hilborne LH, Cancilla PA, and Foos RY: Concurrent herpes simplex and cytomegalovirus retinitis and encephalitis in the acquired immune deficiency syndrome (AIDS).
Ophthalmology 91:1669, 1984.
17. Cibis CW, Flynn JT, and David GB: Herpes simplex retinitis.
Arch Ophthalmol 96:299, 1978.
18. Minckler DS, McLean EB, Shaw CM, and Hendrickson A:
Herpesvirus hominis encephalitis and retinitis. Arch Ophthalmol 94:89, 1976.
19. Johnson BL and Wisotzkey HM: Neuroretinitis associated
with herpes simplex encephalitis in an adult. Am J Ophthalmol
83:481, 1977.