|
|
||||||||
From the Department of Ophthalmology, University of Pittsburgh School of Medicine; and the Eye and Ear Institute, Pittsburgh, Pennsylvania.
| Abstract |
|---|
|
|
|---|
METHODS. In duplicate experiments for each serotype, a total of 20 rabbits (Ad5) or 16 rabbits each (Ad1 and Ad6) were inoculated topically in both eyes, with 1.5 x 106 pfu/eye of the appropriate virus. Twenty-four hours later, the rabbits in each serotype group were randomly divided into two topical treatment groups: I, 0.5% cidofovir; II, control vehicle. Treatment was twice daily for 7 days. All eyes were cultured for virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14.
RESULTS. Compared to the control, treatment with 0.5% cidofovir reduced the following: mean Ad titer (days 1 to 7) for Ad1 (6.3 ± 20 x 101 versus 2.5 ± 3.9 x 102 pfu/ml; P < 0.0003), Ad5 (3.4 ± 5.8 x 102 versus 1.6 ± 2.0 x 103 pfu/ml; P < 0.000001), and Ad6 (1.2 ± 5.1 x 102 versus 5.5 ± 14 x 102 pfu/ml; P = 0.015); reduced Ad-positive eyes/total for Ad1 [45/128 (35%) versus 84/128 (66%); P = 0.000002], Ad5 [84/160 (53%) versus 131/152 (86%); P < 0.000001], and Ad6 [36/128 (28%) versus 82/128 (64%); P < 0.000001]: and reduced the duration of Ad shedding for Ad1 (4.9 ± 1.9 versus 9.3 ± 3.3 days; P < 0.00007), Ad5 (6.4 ± 2.8 versus 11.5 ± 2.3 days; P < 0.0001), and Ad6 (4.4 ± 2.1 versus 8.4 ± 2.5 days; P < 0.00004).
CONCLUSIONS. Topical 0.5% cidofovir twice daily for 7 days demonstrated significant antiviral activity against multiple adenoviral serotypes (Ad1, Ad5, and Ad6) in the New Zealand rabbit ocular model. These in vivo data expand in vitro studies indicating the efficacy of cidofovir against different adenovirus serotypes and support its use in clinical trials.
| Introduction |
|---|
|
|
|---|
The studies of the pathogenesis and treatment of ocular adenoviral infections have been limited by the narrow host range exhibited by human adenoviruses. It has been previously determined that one serotype of human adenovirus, adenovirus type 5 (Ad5), has the ability to extend its host range to permit replication in the eyes of New Zealand rabbits.2 3 Our Ad5 McEwen/New Zealand rabbit ocular model has been used to establish possible clinical guidelines for the use of corticosteroids and nonsteroidal anti-inflammatory drugs (NSAIDs) in the treatment of acute adenoviral ocular infections.4 5
Cidofovir is a highly promising broad spectrum antiviral with significant inhibitory activity against a number of DNA viruses [human cytomegalovirus (HCMV), herpes simplex virus type 1 (HSV-)1, HSV-2, varicella zoster virus (VZV), and adenoviruses ].6 It has been previously demonstrated in prevention and treatment studies that topical administration of cidofovir, using various concentrations and treatment regimens, significantly reduced ocular viral titers and the duration of viral shedding in the Ad5/New Zealand rabbit ocular model.7 8 9
To further evaluate the efficacy of cidofovir as a topical treatment for adenoviral ocular infections, the antiviral efficacy against a variety of adenoviral ocular serotypes in vitro and in vivo should be determined along with the optimum concentration and dosing regimen. Previous in vitro studies have demonstrated that cidofovir was an effective antiviral agent against a variety of ocular adenoviral serotypes.6 9 10 11 However, no data have been published to date demonstrating the efficacy of cidofovir against multiple Ad serotypes in vivo.
In previously published reports, our group demonstrated that the members of human adenovirus subgroup C (Ad1, Ad2, Ad5, and Ad6) were able to replicate in rabbit corneal organ culture.12 Recently, we demonstrated that Ad1, Ad2, and Ad6, along with Ad5, also have the ability to replicate and cause productive infections in the eyes of New Zealand rabbits.13
The goal of the present study was to determine the antiviral efficacy of topical 0.5% cidofovir administered twice daily for 7 days, on multiple Ad serotypes of subgroup C (Ad1, Ad5, and Ad6) in the New Zealand rabbit ocular model of adenoviral infection.
| Materials and Methods |
|---|
|
|
|---|
A549 cells, an epithelial-like cell derived from human lung carcinoma, were grown and maintained in Eagles minimum essential medium with Earles salts (Sigma Cell Culture Reagents, St. Louis, MO), supplemented with 6% fetal bovine serum (Harlan Bioproducts for Science, Indianapolis, IN), 2.5 µg/ml amphotericin B, 100 units/ml penicillin G, and 0.1 mg/ml streptomycin (Sigma).
Experimental Drugs
Cidofovir [S-HPMPC;
(S)-9-(3-hydroxy-2-phophonylmethoxypropyl)cytosine],
was provided by Bausch and Lomb Pharmaceuticals, Inc., Tampa, Florida.
A topical ocular formulation was prepared as a 0.5% solution. Control
eye drops for cidofovir consisted of the vehicle alone.
Animals
Six-week-old, 1-kg, female New Zealand albino rabbits were
obtained from Myrtles Rabbitry (Thompson Station, TN). All animal
studies conformed to the ARVO Statement on the Use of Animals in
Ophthalmic and Vision Research. Institutional approval was obtained and
institutional guidelines regarding animal experimentation were
followed.
Experimental Design
This study was performed in duplicate for each virus serotype.
After appropriate systemic and topical anesthesia,2
a
total of 20 rabbits, for both trials, for Ad5 McEwen and 16 rabbits
each for Ad1 Kmetz and Ad6 ATCC were inoculated with 50 µl (1.5 x 106 pfu/eye) of the appropriate virus in both
eyes after 12 cross-hatched strokes of a no. 25 sterile
needle.7
Twenty-four hours after inoculation, each virus
serotype group was divided into two topical treatment groups: I, 0.5%
cidofovir (n = 10 rabbits for Ad5, n =
8 rabbits for Ad1 and Ad6); II, control drops (n = 10
rabbits for Ad5, n = 8 rabbits for Ad1 and Ad6). For
each serotype tested, treatment of the cidofovir and control groups was
administered in both eyes twice daily for 7 days. Ocular swabbing was
performed on days 0, 1, 3, 4, 5, 7, 9, 11, and 14 after inoculation at
least 1 hour after the second dose. Each eye was swabbed in the upper
and lower fornicies with a cotton-tipped applicator, and the swab was
placed in 1 ml of media and frozen at -70°C, pending plaque assay.
The experimental design was masked with regard to the identity of the
treatment drops, so that treatment, swabbing, and the determination of
viral titers also was masked to those carrying out the experiment.
Determination of Viral Titers (Plaque Assay)
The ocular samples to be titered were thawed and diluted serially
(1:10) for two dilutions. Each dilution and the undiluted original
sample were then inoculated onto A549 monolayers (0.1 ml per well) in
duplicate wells of a 24-well plate. The virus was adsorbed for 3 hours
at 37°C in a 5% CO2water vapor atmosphere.
After adsorption, 1 ml of A549 media plus 0.5% methylcellulose was
added to each well, and the plates were incubated at 37°C in a 5%
CO2water vapor atmosphere. After 7 days
incubation, the cells were stained with 0.5% gentian violet, and the
number of plaques was counted under a dissecting microscope (25x). The
viral titers were then calculated and expressed as plaque-forming units
per milliliter (pfu/ml).
Statistical Analysis
After the completion of all experiments, the codes that masked the
identity of the treatment were broken, and the data from each
experiment were analyzed statistically. Because comparable results were
obtained in each experiment, the data were then pooled to obtain a
larger subject number and analyzed using analysis of variance (ANOVA),
Fishers Exact Test, and
2 analyses.
Significance was established at the P
0.05
confidence level.
| Results |
|---|
|
|
|---|
|
|
|
Ad-Positive Eyes per Total
The number of Ad-positive eyes per total was determined for each
serotype and treatment group by ascertaining the number of eye swabs
that demonstrated a positive Ad culture per total number of cultures.
Table 1
summarizes these results. Overall, from days 1 to 14, eyes treated with
0.5% cidofovir demonstrated fewer Ad-positive eyes than the control
group for Ad1 Kmetz [45/128 (35%) versus 84/128 (66%);
P = 0.000002], Ad5 McEwen [84/160 (53%) versus
131/152 (86%); P < 0.000001], and Ad6 ATCC
[36/128 (28%) versus 82/128 (64%); P <
0.000001] (
2 analysis).
|
0.0434) for Ad6 ATCC (Fishers Exact
Test).
Duration of Ad Shedding
The duration of Ad shedding was determined for each eye by
discerning the final day on which a positive Ad culture was detected
and calculating the mean and SD for both treatment groups for each
serotype. Treatment with 0.5% cidofovir significantly reduced the mean
duration of Ad shedding compared to the control group for the three
serotypes tested: Ad1 Kmetz [n = 16 for both groups;
4.9 ± 1.9 versus 9.3 ± 3.3 days (P <
0.00007)]; Ad5 McEwen [n = 20 for 0.5% Cidofovir;
n = 18 for control; 6.4 ± 2.8 versus 11.5 ±
2.3 days (P < 0.0001)]; Ad6 ATCC [n = 16 for both groups; 4.4 ± 2.1 versus 8.4 ± 2.5 days
(P < 0.00004)] (ANOVA).
| Discussion |
|---|
|
|
|---|
Recently, our group demonstrated that Ad1, Ad2, and Ad6, along with Ad5, can replicate and cause productive infections in the eyes of New Zealand rabbits.13 Although all these serotypes are members of a single subgroup of adenoviruses (subgroup C), they are the only adenoviruses known that have the genetic capability to extend their host range to replicate in the eyes of New Zealand rabbits. The serotypes most commonly associated with human adenoviral ocular disease (Ad3, 4, 7) did not replicate in rabbit corneal organ culture12 and (Ad8, 19) did not replicate in New Zealand rabbit eyes.13 Nevertheless, we believe that information obtained from the use of the subgroup C adenoviruses will be useful to demonstrate antiviral efficacy of topical cidofovir against multiple Ad serotypes in vivo.
The results of this study clearly confirms and extends our previous work by demonstrating that topical cidofovir reduces Ad5, Ad1, and Ad6 ocular titers and the number of Ad-positive eyes and shortens the duration of ocular shedding in vivo. The treatment regimen of 0.5% cidofovir twice daily for 7 days clearly delivered a therapeutic dose of cidofovir. The present study further strengthens the preclinical data that support the continued development of cidofovir as the first broad spectrum antiviral agent for the treatment of adenoviral and HSV ocular infections.14
| Footnotes |
|---|
Submitted for publication May 28, 1999; revised August 27, 1999; accepted September 15, 1999.
Commercial relationships policy: C2, C3.
Corresponding author: Y. Jerold Gordon, University of Pittsburgh School of Medicine, The Eye and Ear Institute, 203 Lothrop Street, Pittsburgh, PA 15213. yjgordon{at}vision.eei.upmc.edu
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
E. G. Romanowski, K. A. Yates, B. Teuchner, M. Nagl, E. U. Irschick, and Y. J. Gordon N-Chlorotaurine Is an Effective Antiviral Agent against Adenovirus In Vitro and in the Ad5/NZW Rabbit Ocular Model Invest. Ophthalmol. Vis. Sci., May 1, 2006; 47(5): 2021 - 2026. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. R. Kinchington, E. G. Romanowski, and Y. Jerold Gordon Prospects for adenovirus antivirals J. Antimicrob. Chemother., April 1, 2005; 55(4): 424 - 429. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. De Clercq Clinical Potential of the Acyclic Nucleoside Phosphonates Cidofovir, Adefovir, and Tenofovir in Treatment of DNA Virus and Retrovirus Infections Clin. Microbiol. Rev., October 1, 2003; 16(4): 569 - 596. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Hillenkamp, T. Reinhard, R. S. Ross, D. Bohringer, O. Cartsburg, M. Roggendorf, E. De Clercq, E. Godehardt, and R. Sundmacher Topical Treatment of Acute Adenoviral Keratoconjunctivitis With 0.2% Cidofovir and 1% Cyclosporine: A Controlled Clinical Pilot Study Arch Ophthalmol, October 1, 2001; 119(10): 1487 - 1491. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. K. Adhikary, J. Numaga, T. Kaburaki, H. Kawashima, S. Kato, M. Araie, K. Miyata, H. Shimizu, F. Yagyu, E. Suzuki, et al. Rapid Detection and Typing of Oculopathogenic Strain of Subgenus D Adenoviruses by Fiber-Based PCR and Restriction Enzyme Analysis Invest. Ophthalmol. Vis. Sci., August 1, 2001; 42(9): 2010 - 2015. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. G. Romanowski, Y. J. Gordon, T. Araullo-Cruz, K. A. Yates, and P. R. Kinchington The Antiviral Resistance and Replication of Cidofovir-Resistant Adenovirus Variants in the New Zealand White Rabbit Ocular Model Invest. Ophthalmol. Vis. Sci., July 1, 2001; 42(8): 1812 - 1815. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. G. Romanowski and Y. J. Gordon Effects of Diclofenac or Ketorolac on the Inhibitory Activity of Cidofovir in the Ad5/NZW Rabbit Model Invest. Ophthalmol. Vis. Sci., January 1, 2001; 42(1): 158 - 162. [Abstract] [Full Text] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |