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From the Department of Ophthalmology, University of Pittsburgh School of Medicine, Pennsylvania.
| Abstract |
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METHODS. According to two protocols, 20 rabbits were inoculated in both eyes with Ad5 topically to study adenovirus replication, and 20 rabbits were inoculated in both eyes topically and intrastromally to study the formation of subepithelial infiltrates. Animals were randomized to four masked treatment groups: group I, 0.5% cidofovir + artificial tears; group II, 0.5% cidofovir + 0.5% ketorolac tromethamine; group III, 0.5% cidofovir + 0.1% diclofenac sodium; and group IV, control + artificial tears. Cidofovir and control were administered to both eyes twice daily for 7 days, and artificial tears, ketorolac, and diclofenac four times daily for 14 days. Eyes were cultured on days 0, 1, 3, 4, 5, 7, 9, 11, and 14.
RESULTS. Compared with the control group, all cidofovir-treated groups demonstrated significant antiviral effects on adenovirus replication. There were no differences in adenovirus replication among the cidofovir-treated groups (I, II, and III), nor were there any differences among all groups (IIV) in the formation of subepithelial infiltrates.
CONCLUSIONS. Concurrent treatment of ketorolac or diclofenac with cidofovir did not diminish its antiviral inhibitory activity on adenovirus replication, nor did it prevent the formation of subepithelial infiltrates in the rabbit model.
| Introduction |
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Cidofovir, (S-HPMPC), is a broad-spectrum antiviral agent with significant in vitro inhibitory activity against a number of DNA viruses (human cytomegalovirus [CMV], herpes simplex virus [HSV]-1 and -2, varicella-zoster virus, and adenoviruses).2 Previous prevention and treatment studies have shown that topical administration of cidofovir significantly reduces ocular viral titers, and the duration of viral shedding in the Ad5/New Zealand White rabbit ocular model3 4 5 6 and in the HSV-1/New Zealand White rabbit keratitis model.7 8 9 Cidofovir is currently FDA approved for the systemic treatment of CMV retinitis in patients with acquired immune deficiency syndrome (AIDS).
The role of topical anti-inflammatory agents in the treatment of adenoviral ocular infections remains controversial. The routine clinical use of topical corticosteroids is generally discouraged by most authorities.1 In experimental studies, topical 1% prednisolone acetate significantly enhanced Ad5 replication and prolonged Ad5 shedding,10 and the antiviral inhibitory activity of topical cidofovir was eliminated by local immunosuppression induced by 1% prednisolone acetate during concomitant therapy in the Ad5/New Zealand White rabbit ocular model.11
Nonsteroidal anti-inflammatory drugs (NSAIDs) are an important category of anti-inflammatory agent currently available for ophthalmic use. Topical NSAIDs have been shown to relieve symptoms of acute allergic conjunctivitis12 and to reduce inflammation associated with alkali burns of the cornea, herpetic uveitis, and ocular trauma.13 They have been shown to reduce postoperative inflammation after cataract14 15 and refractive surgery.16 Their value as local analgesics to reduce corneal sensitivity17 18 after traumatic abrasions19 and excimer laser refractive procedures has led to widespread use.20 Recently, topical NSAIDs have been implicated in a few cases with serious side effects (corneal melting and perforation) after cataract surgery,21 but no serious side effects have been reported after nonsurgical topical therapy.
Although no clinical studies have been performed to determine the effects of topical NSAIDs on the natural history of adenoviral ocular infections, experimental treatment with two topical NSAIDs (diclofenac sodium and ketorolac tromethamine) showed no stimulatory or inhibitory effect on adenoviral replication and no effect on the natural immune clearance of adenovirus from the eye.22 These NSAIDs also did not prevent the formation of subepithelial infiltrates in the Ad5/New Zealand White rabbit ocular model.22
The goal of the present study was to assess how topical NSAID (e.g., diclofenac sodium and ketorolac tromethamine) therapy would affect the established antiviral inhibitory activity of topical cidofovir and the formation of subepithelial infiltrates in the Ad5/New Zealand White rabbit ocular model. These results may support future clinical guidelines for the treatment of symptomatic adenoviral ocular infections with topical cidofovir and adjunct topical NSAIDs.
| Methods |
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A549 cells, epithelial-like cells derived from human lung carcinoma (CCL-185; American Type Culture Collection, Rockville, MD), were grown and maintained in Eagles minimum essential medium (MEM) with Earles salts, supplemented with 6% fetal bovine serum, 2.5 µg/ml amphotericin B, 100 U penicillin G, and 0.1 mg streptomycin per milliliter (Sigma, St. Louis, MO).
Experimental Drugs
Cidofovir (S-HPMPC,
[(S)-9-(3-hydroxy-2-phophonylmethoxypropyl)-cytosine]), was supplied
by Bausch & Lomb Pharmaceuticals (Tampa, FL) as a 0.5% solution.
Control eye drops for cidofovir consisted of the vehicle alone. The
NSAIDs, diclofenac sodium 0.1% (Voltaren Ophthalmic; CIBA Vision
Ophthalmics, Atlanta, GA) and ketorolac tromethamine 0.5% (Acular;
Allergan Pharmaceuticals, Irvine, CA) were purchased from the pharmacy
at the University of Pittsburgh Medical Center. Artificial tears (0.5%
carboxymethylcellulose [Sigma] in phosphate-buffered saline [PBS])
served as control drops for the NSAIDs.
Animals
Three to 4-lb female New Zealand White rabbits were obtained
from Myrtles Rabbitry, Thompson Station, TN. All animal studies
conformed to the ARVO Statement for the Use of Animals in Ophthalmic
and Vision Research. University of Pittsburgh Institutional Animal Care
and Use Committee (IACUC) approval was obtained, and
institutional guidelines regarding animal experimentation were
followed.
Assessment of Ad5 Replication with Topical Inoculation Only
This study was performed in duplicate, with 20 rabbits used per
experiment. After appropriate systemic anesthesia with 33 mg/kg
ketamine and 10 mg/kg xylazine and topical anesthesia with
proparacaine, the rabbits were inoculated with 50 µl (1.2 x
106 plaque-forming units [pfu]/eye) of Ad5
McEwen in both eyes after 12 cross-hatched strokes of a number 25
sterile needle.4
Twenty-four hours later, a total of 10
rabbits each from both experiments were randomly assigned to one of
four topical coded treatment groups: group I, 0.5% cidofovir +
artificial tears; group II, 0.5% cidofovir + 0.5% ketorolac
tromethamine; group III, 0.5% cidofovir + 0.1% diclofenac sodium;
group IV, control + artificial tears. Cidofovir and control were
administered to both eyes twice daily for 7 days and artificial tears,
ketorolac, and diclofenac four times daily for 14 days. Drops were
administered at least 1 hour apart with cidofovir given first and
fourth in the 6-drop regimen on days 1 through 7. Ocular swabbing to
recover adenovirus from the tear film and corneal and conjunctival
surfaces was performed on days 0, 1, 3, 4, 5, 7, 9, 11, and 14 after
inoculation and frozen at -70°C pending plaque assay.
Assessment of Ad5-Induced Subepithelial Infiltrates with Topical
and Intrastromal Inoculation
To study the effects of concurrent therapy with diclofenac
sodium and ketorolac tromethamine and cidofovir on the formation of
subepithelial corneal infiltrates, a second inoculation technique was
needed (i.e., topical and intrastromal inoculation of adenovirus). This
technique produces a reliable and reproducible number of subepithelial
corneal infiltrates for grading. In contrast, the technique of topical
inoculation alone, although excellent for titer studies, does not
consistently produce a reliable number of subepithelial corneal
infiltrates for grading.4
10
11
22
23
This study was
performed in duplicate, with 20 rabbits used per experiment. After
topical and systemic anesthesia, both eyes of the rabbits were
inoculated with 50 µl (1.2 x 105 pfu/eye)
Ad5 McEwen intrastromally by using a 30-gauge short-beveled needle to
form five focal blebs (dice pattern, 10 µl per bleb). The corneas
were then scarified superficially (eight scratches) with a number 25
needle to form a square around the central intrastromal injections.
Inoculation was completed by applying 50 µl (1.2 x
106 pfu/eye) Ad5 McEwen.22
Twenty-four hours later, 10 rabbits each were randomly assigned to the
same treatment groups and regimens, as previously described for the
topical inoculationonly group. The extent of subepithelial immune
infiltrate formation was determined by slit lamp examination of rabbit
corneas on day 25 after injection (PI). The extent of subepithelial
infiltrate formation was scored according to a scale of zero to four
(zero, 0 infiltrates; one, 1 to 5 infiltrates; two, 6 to 10
infiltrates; three, 11 to 15 infiltrates; four, 16 + infiltrates).
Determination of Viral Titers by Plaque Assay
The ocular samples to be titered were thawed and diluted
serially (1:10) for two dilutions. Each dilution (0.1 ml per well) was
then inoculated onto A549 cells in duplicate wells of a 24-well plate.
The virus was adsorbed for 3 hours at 37°C in a 5%
CO2-water vapor atmosphere. After adsorption, 1
ml of outgrowth media plus 0.5% methylcellulose was added to each
well, and the plates were incubated at 37°C in a 5%
CO2-water vapor atmosphere for 7 days. The plates
were stained with 0.5% gentian violet, and the number of plaques per
well counted under a dissecting microscope (x25). The viral titers
were then calculated and expressed in plaque-forming units per
milliliter. The viral titer data were presented as both the mean daily
Ad5 titers and a global measure referred to as the mean combined Ad5
titers during the early phase (days 15) and late phase (days 714)
of infection.
Evaluation of Serious Ocular Toxicity
All eyes were examined for signs of serious toxicity (corneal
melting and perforation) before culture (during the acute phase of
infection) and during slit lamp evaluation of subepithelial infiltrates
(during the late phase of infection).
Statistical Analysis
After the completion of both experiments, the codes masking the
treatment regimens were broken, and the data from each experiment were
analyzed statistically. Data based on viral replication (Ad5 titers,
duration of shedding, and Ad5-positive cultures/total) from experiments
using the topical inoculationonly technique were combined and
analyzed statistically. Similarly, data based on clinical scores of
subepithelial infiltrates from experiments using the topical and
intrastromal inoculation technique were combined and analyzed
statistically. The statistical tests used included: analysis of
variance (ANOVA), KruskalWallis ANOVA, Duncans multiple comparisons
for ANOVA,
2, and Monte Carlo randomization
analyses. Significance was established at the P
0.05
confidence level. There was one outlying titer value (1.17 x
103 pfu/ml) from a day 7 sample in the cidofovir
+ ketorolac group that was 3 logs greater than the mean ± SD
(2.1 ± 8.0 x 100 pfu/ml) of the 19
other day 7 samples, of which only two demonstrated a positive Ad5
culture. This data point exceeded our criterion for inclusion (greater
than three SDs from the mean) and was eliminated from all titer,
Ad5-positive eyes, and duration of shedding analyses.
| Results |
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Ad5-Positive Cultures per Total.
A significant antiviral effect was seen overall from days 1 through 14
in eyes treated with cidofovir + artificial tears (79/160; 49%),
cidofovir + ketorolac (71/159; 45%), and cidofovir + diclofenac
(81/160; 51%), which demonstrated fewer Ad-positive cultures compared
with the control + artificial tears group (100/160; 63%;
P
0.042,
2 analysis). There
were no differences among the cidofovir treatment groups.
During the early phase of infection (days 15), there were no
differences among any of the groups based on Ad5-positive cultures
(Table 1)
. However, during the late phase (days 714), an antiviral
effect was demonstrated in which the cidofovir + artificial tears
(6/80; 8%), cidofovir + ketorolac (3/79; 4%), and cidofovir +
diclofenac (9/80; 11%) groups all demonstrated fewer Ad-positive
cultures compared with the control + artificial tears group (24/80;
30%; P < 0.007,
2 analysis).
There were no differences among the cidofovir + artificial tears,
cidofovir + ketorolac, and cidofovir + diclofenac groups.
The percentage of daily Ad5-positive cultures are displayed graphically in Figure 2 . Compared with the control + artificial tears group, significantly fewer Ad-positive cultures were demonstrated for the cidofovir + artificial tears group on day 7 (P = 0.0099) and day 9 (P = 0.0099), for the cidofovir + ketorolac group on day 7 (P < 0.02) and day 9 (P = 0.0099), and for the cidofovir + diclofenac group on day 9 (P < 0.02; Monte Carlo randomization test). There were no differences among the cidofovir treatment groups on any day.
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Evaluation of Serious Ocular Toxicity
There were no cases of corneal melting or perforation in any of
the eyes treated with topical NSAIDs, cidofovir, or artificial tears in
any of the experimental studies.
| Discussion |
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Corticosteroids are known to inhibit both the cyclooxygenase and lipoxygenase inflammatory pathways, other cellular enzymes, and direct expression of cytokines and lymphokines that activate the immune system. Previously, we reported that the antiviral efficacy of topical cidofovir was eliminated by local immunosuppression induced by 1% prednisolone acetate treatment in the Ad5/New Zealand White rabbit ocular model.11
NSAIDs (e.g., diclofenac sodium and ketorolac tromethamine) represent a class of anti-inflammatory agents currently available for ophthalmic use. NSAIDs block only the cyclooxygenase pathway and appear to have no direct effect on immune-mediated mechanisms.13 Although they do not have the potency of strong topical corticosteroids (e.g., 1% prednisolone acetate), they also are free of significant steroid-associated side effects (cataract, glaucoma, superinfection). Despite a recent anecdotal report of serious side effects associated with topical NSAIDs (corneal melting and perforation) after cataract surgery,21 we did not observe any cases of corneal thinning or perforation after topical diclofenac or ketorolac therapy in rabbit eyes.
There have been no clinical trials performed to determine the effects of topical NSAIDs on adenoviral ocular infections. Experimentally, prolonged treatment with topical diclofenac or ketorolac had no effect on the natural history of adenoviral replication, virus clearance or the formation of subepithelial infiltrates in the Ad5/New Zealand rabbit ocular model.22 Based on those results, we proposed that topical diclofenac or ketorolac may be desirable alternatives to topical steroids as adjunct therapy with cidofovir.
The antiviral efficacy of topical 0.5% cidofovir was not affected when used in combination with either topical 0.5% ketorolac tromethamine or 0.1% diclofenac sodium. Furthermore, the effect of the combined use of topical cidofovir with topical ketorolac or diclofenac was not different from the use of cidofovir alone with regard to formation of subepithelial infiltrates. Although topical corticosteroids alone and in combination with cidofovir inhibited formation of subepithelial infiltrates, the formation of these infiltrates is believed to be immune based23 and these data support the observed differences as being best understood in terms of the immune-suppressive effect of topical steroids rather than their anti-inflammatory activity.
Based on the Ad5/New Zealand White rabbit ocular model, our projected clinical guideline suggests that treatment with topical NSAIDs diclofenac sodium and ketorolac tromethamine may not adversely effect the antiviral inhibitory activity of 0.5% cidofovir during the treatment of acute adenoviral ocular infections. The clinically proven anti-inflammatory and topical analgesic effects may provide patient comfort by reducing ocular inflammation and local pain and irritation. However, a controlled clinical trial remains the best way to establish the value of concomitant NSAIDs and cidofovir therapy.
| Footnotes |
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Submitted for publication May 15, 2000; revised August 31, 2000; accepted September 6, 2000.
Commercial relationships policy: C (EGR), F (YJG).
Corresponding author: Y. Jerold Gordon, The Eye & Ear Institute, 203 Lothrop Street, Pittsburgh, PA 15213. gordonjs{at}msx.upmc.edu
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