Objective—To evaluate the ability of 5 small interfering RNAs (siRNAs) targeting mRNA of the feline herpesvirus-1 (FHV-1) DNA polymerase gene to reduce in vitro viral replication and gene expression of FHV-1, to evaluate combinations of these siRNAs with siRNAs that target the glycoprotein D gene of FHV-1, and to determine the combination or combinations of siRNAs that yield the greatest inhibition of in vitro viral replication.
Procedures—CRFK cells were transfected with siRNAs designed to target mRNA of the FHV-1 DNA polymerase gene. Effective treatment was determined by quantification of the inhibition of mRNA available for DNA polymerase translation, viral protein production, and viral replication. Combinations of 2 siRNAs that target mRNA of the FHV-1 DNA polymerase gene and 2 siRNAs that target the mRNA of the essential FHV-1 glycoprotein D gene were evaluated for the ability to inhibit viral replication.
Results—Verified by a reduction in viral gene expression, 2 of the 5 siRNAs designed to target mRNA of the FHV-1 DNA polymerase gene significantly suppressed viral replication. Two combinations of siRNAs that target mRNA of the FHV-1 DNA polymerase gene, the FHV-1 glycoprotein D gene, or both also significantly suppressed viral replication.
Conclusions and Clinical Relevance—Combinations of siRNAs that target mRNA of the FHV-1 DNA polymerase gene, FHV-1 glycoprotein D gene, or both could potentially be used as a treatment for the prevention of clinical disease associated with FHV-1 infection.
Procedures—Crandell-Rees feline kidney cells were transfected with small interfering RNAs (siRNAs) that were designed to inhibit expression of FHV-1 glycoprotein D. The effectiveness of the treatment was determined via measurement of amounts of glycoprotein D mRNA, intracellular glycoprotein D, and glycoprotein D expressed on the surface of infected cells and comparison with appropriate control sample data.
Results—2 of 6 siRNAs tested were highly effective in reducing expression (ie, knockdown) of glycoprotein D mRNA; there were 77% and 85% reductions in mRNA in treated samples, compared with findings in the control samples. The knockdown of glycoprotein D mRNA resulted in reduced glycoprotein D protein production, as evidenced by 27% and 43% decreases in expression of glycoprotein D on the surface of siRNA-treated, FHV-1–infected cells and decreased expression of the protein within infected cells, compared with control samples. Treatment with these siRNAs also resulted in inhibition of FHV-1 replication, with reductions of 84% and 77% in amounts of virus released into cell culture supernatant, compared with findings in control samples.
Conclusions and Clinical Relevance—2 chemically produced siRNAs that targeted the glycoprotein D gene significantly reduced FHV-1 titers in treated cells, suggesting that glycoprotein D is necessary for production of infective virions. This gene is a potential target for RNA interference as a means of inhibition of FHV-1 infection of feline cells.
Objective—To evaluate agents used for delivery of small interfering RNAs (siRNAs) into feline corneal cells, toxicity of the delivery agents, and functionality of anti-feline herpesvirus 1 (FHV-1)–specific siRNA combinations.
Sample—Feline primary corneal cells and 19 six-month-old colony-bred cats.
Procedures—siRNA delivery into corneal cells via various delivery agents was evaluated via flow cytometric detection of labeled siRNAs. Cellular toxicity was evaluated with a proliferation assay. Functionality was tested via quantitative reverse transcriptase PCR assay, plaque assay, and flow cytometry. In vivo safety was evaluated with an ocular scoring method following topical application of delivery agents containing siRNAs into eyes. Corneal biopsy specimens were used to assess safety and uptake of siRNAs into corneal cells.
Results—Use of 3 delivery agents resulted in > 95% transfection of primary corneal cells. Use of a peptide for ocular delivery yielded approximately 82% transfection of cells in vitro. In cultured corneal cells, use of the siRNA combinations resulted in approximately 76% to 89% reduction in FHV-1–specific mRNA, 63% to 67% reduction of FHV-1–specific proteins in treated cells, and 97% to 98% reduction in FHV-1 replication. The agents were nonirritating in eyes, caused no substantial clinical ocular signs, and were nontoxic. Histologically, corneal epithelium and stroma were normal in treated cats. However, none of the agents were effective in delivering siRNAs into the corneal cells in vivo.
Conclusions and Clinical Relevance—The tested anti–FHV-1–specific siRNAs could potentially be used as a treatment for FHV-1 if a successful means of in vivo delivery can be achieved.
Objective—To analyze the 7a7b genes of the feline coronavirus (FCoV) of cheetahs, which are believed to play a role in virulence of this virus.
Sample Population—Biologic samples collected during a 4-year period from 5 cheetahs at the same institution and at 1 time point from 4 cheetahs at different institutions.
Procedures—Samples were first screened for FCoV via a reverse transcription-PCR procedure involving primers that encompassed the 3′-untranslated region. Samples that yielded positive assay results were analyzed by use of primers that targeted the 7a7b open reading frames. The nucleotide sequences of the 7a7b amplification products were determined and analyzed.
Results—In most isolates, substantial deletional mutations in the 7a gene were detected that would result in aberrant or no expression of the 7a product because of altered reading frames. Although the 7b gene was also found to contain mutations, these were primarily point mutations resulting in minor amino acid changes. The coronavirus associated with 1 cheetah with feline infectious peritonitis had intact 7a and 7b genes.
Conclusions and Clinical Relevance—The data suggest that mutations arise readily in the 7a region and may remain stable in FCoV of cheetahs. In contrast, an intact 7b gene may be necessary for in vivo virus infection and replication. Persistent infection with FCoV in a cheetah population results in continued virus circulation and may lead to a quasispecies of virus variants.
Objective—To determine the methicillin-resistant
profile of staphylococcal isolates from the skin of
dogs with pyoderma.
Animals—90 dogs with pyoderma.
Procedure—Staphylococci isolated from dogs with
pyoderma were tested for susceptibility to methicillin
by use of a standard disk diffusion test with oxacillin
disks. The DNA extracted from the isolates was tested
for the mecA gene that encodes the penicillinbinding
protein 2a (PBP2a) by use of a polymerase
chain reaction (PCR) assay. The expression of PBP2a
was determined with a commercial latex agglutination
assay. Species of staphylococcal isolates were
identified by use of morphologic, biochemical, and
Results—Most of the isolated staphylococci were
Staphylococcus intermedius isolates. Whereas only 2
of 57 S intermedius isolates were resistant to methicillin,
approximately half of the isolates had the mecA
gene and produced PBP2a. Staphylococcus schleiferi
was the second most common isolate. Widespread
resistance to methicillin was found among S schleiferi
isolates. More coagulase-negative S schleiferi isolates
were identified with mecA gene-mediated resistance
to methicillin, compared with coagulase-positive S
Conclusions and Clinical Relevance—The latex
agglutination assay for the detection of PBP2a
expression coupled with the PCR assay for the mecA
gene may provide new information about emerging
antimicrobial resistance among staphylococcal isolates.
(Am J Vet Res2004;65:1265–1268)
Objective—To evaluate the ability of small interfering RNAs (siRNAs) to inhibit in vitro viral replication and gene expression of feline coronavirus (FCoV).
Sample—Cell cultures of Crandell-Rees feline kidney cells.
Procedures—5 synthetic siRNAs that each targeted a different region of the FCoV genome were tested individually and in various combinations for their antiviral effects against 2 strains of FCoV (feline infectious peritonitis virus WSU 79-1146 and feline enteric coronavirus WSU 79-1683) in cell cultures. Tested combinations targeted the FCoV leader and 3′ untranslated region, FCoV leader region and nucleocapsid gene, and FCoV leader region, 3′ untranslated region, and nucleocapsid gene. For each test condition, assessments included relative quantification of the inhibition of intracellular viral genomic RNA synthesis by means of real-time, reverse-transcription PCR analysis; flow cytometric evaluation of the reduction of viral protein expression in infected cells; and assessment of virus replication inhibition via titration of extracellular virus with a TCID50 infectivity assay.
Results—The 5 siRNAs had variable inhibitory effects on FCoV when used singly. Combinations of siRNAs that targeted different regions of the viral genome resulted in more effective viral inhibition than did individual siRNAs that targeted a single gene. The tested siRNA combinations resulted in approximately 95% reduction in viral replication (based on virus titration results), compared with findings in negative control, nontargeting siRNA–treated, FCoV-infected cells.
Conclusions and Clinical Relevance—In vitro replication of FCoV was specifically inhibited by siRNAs that targeted coding and noncoding regions of the viral genome, suggesting a potential therapeutic application of RNA interference in treatment of feline infectious peritonitis.
Objective—To determine frequency with which
Staphylococcus schleiferi could be isolated from dogs
with pyoderma and antimicrobial susceptibility patterns
of isolates that were obtained.
Animals—54 dogs with a first (n = 14) or recurrent
(40) episode of pyoderma.
Procedure—Specimens were obtained and submitted
for bacterial culture. Isolates were identified as S
schleiferi on the basis of growth and biochemical
characteristics. Two isolates were submitted for DNA
sequencing to confirm identification. Methicillin susceptibility
was determined by means of disk diffusion
with oxacillin-impregnated disks.
Results—3 of 14 dogs examined because of a first
episode of pyoderma and 12 of 40 dogs examined
because of a recurrent episode of pyoderma were
receiving antimicrobials at the time of specimen collection.
Staphylococcus schleiferi was not isolated
from any dog with first-time pyoderma but was isolated
from 5 dogs with recurrent pyoderma that were
not receiving antimicrobials at the time of specimen
collection and 10 dogs with recurrent pyoderma that
were receiving antimicrobials. Nine isolates were
identified as S schleiferi subsp schleiferi, and 6 were
identified as S schleiferi subsp coagulans. All S
schleiferi subsp schleiferi isolates were resistant to
methicillin, but only 2 S schleiferi subsp coagulans
isolates were. Two methicillin-resistant isolates were
also resistant to fluoroquinolones, and 1 isolate had
intermediate susceptibility to fluoroquinolones.
Conclusions and Clinical Relevance—Results suggest
that S schleiferi subsp schleiferi and S schleiferi
subsp coagulans may be isolated from dogs with recurrent
pyoderma. Although isolates from dogs with pyoderma
were frequently resistant to methicillin, multiple
drug resistance was uncommon. (J Am Vet Med Assoc
Objective—To measure antibody titers against
bovine coronavirus (BCV), determine frequency of
BCV in nasal swab specimens, and compare calves
treated for bovine respiratory tract disease (BRD)
between those given an intranasally administered
vaccine and control calves.
Design—Randomized clinical trial.
Animals—414 heifer calves.
Procedure—Intranasal BCV antigen concentration
and antibody titer against BCV were measured on
entry to a feedlot. Calves were randomly assigned to
receive 3.0 mL of a modified-live virus vaccine against
bovine enteric coronavirus and rotavirus or 3.0 mL of
saline (0.9% NaCl) solution. Calves were confined to
1 of 2 pens, depending on vaccination status, for a
minimum of 17 days of observation (range, 17 to 99).
Selection of calves for treatment of BRD and scoring
for severity of disease were done by veterinarians
unaware of treatment status.
Results—Intranasal BCV (125/407 [31%]) and serum
antibody titers ≥ 20 against BCV (246/396 [62%])
were identified in calves entering the feedlot.
Vaccination was associated with significant decrease
in risk of treatment for BRD; intranasal BCV on entry
to the feedlot was associated with increased risk of
treatment. Univariate analysis revealed that control
calves with intranasal BRD on entry to the feedlot and
those with antibody titer < 20 were significantly more
likely to be treated for BRD.
Conclusions and Clinical Relevance—These data
provide further evidence of an association between
BCV and respiratory tract disease in feedlot calves.
An intranasally administered vaccine appeared to
reduce risk of treatment for BRD. (J Am Vet Med