BET Inhibitor JQ1 Attenuates Feline Leukemia Virus DNA, Provirus, and Antigen Production in Domestic Cat Cell Lines

Feline leukemia virus (FeLV) is a cosmopolitan gammaretrovirus that causes lifelong infections and fatal diseases, including leukemias, lymphomas, immunodeficiencies, and anemias, in domestic and wild felids. There is currently no definitive treatment for FeLV, and while existing vaccines reduce the prevalence of progressive infections, they neither provide sterilizing immunity nor prevent regressive infections that result in viral reservoirs with the potential for reactivation, transmission, and the development of associated clinical diseases. Previous studies of murine leukemia virus (MuLV) established that host cell epigenetic reader bromodomain and extra-terminal domain (BET) proteins facilitate MuLV replication by promoting proviral integration. Here, we provide evidence that this facilitatory effect of BET proteins extends to FeLV. Treatment with the archetypal BET protein bromodomain inhibitor (+)-JQ1 and FeLV challenge of two phenotypically disparate feline cell lines, 81C fibroblasts and 3201 lymphoma cells, significantly reduced FeLV proviral load, total FeLV DNA load, and p27 capsid protein expression at nonlethal concentrations. Moreover, significant decreases in FeLV proviral integration were documented in 81C and 3201 cells. These findings elucidate the importance of BET proteins for efficient FeLV replication, including proviral integration, and provide a potential target for treating FeLV infections.

Blood and bone marrow findings in two pups with mucopolysaccharidosis type VII

Routine blood smear findings in two of four 11-day-old mixed-breed dog littermates were suggestive of a lysosomal storage disease (LSD) that was documented to be mucopolysaccharidosis type VII (MPS VII) by molecular testing. In this condition, a functional β-glucuronidase deficiency results in the accumulation of glycosaminoglycans (GAGs) in cells and tissues where β-glucuronidase is important in GAG degradation. Most neutrophils and a moderate number of lymphocytes within the blood had atypical cytoplasmic magenta inclusions. The bone marrow assessment from one of the two affected pups at 24 days of age revealed similar magenta granulation in myeloid precursor cells that was most prominent in promyelocytes and myelocytes. Moreover, atypical magenta material was present within vacuoles as well as extracellularly in some osteoblasts and macrophages. Histologic bone marrow sections revealed prominent vacuolation of osteoblasts, and some osteoclasts appeared separated from the bone by layers of osteoblasts or hematopoietic cells. At 2 months of age, the second affected dog showed moderate growth retardation and had similar but more prominent hematologic findings that extended to monocytes, eosinophils, and eosinophil precursors. It had an increased number of bone marrow macrophages with many vacuoles that could be seen cytologically to contain magenta material, and there was mild nonselective phagocytosis of hemic cells. Of the hematologic cells, inclusions were most prominent in promyelocytes, myelocytes, and macrophages, cells with relatively high β-glucuronidase activity, and GAG exposure within lysosomes or lysosome-like primary granules of granulocyte precursors.

Controlling bovine leukemia virus in dairy herds by identifying and removing cows with the highest proviral load and lymphocyte counts

The objective of this field trial was to reduce bovine leukemia virus (BLV) transmission and prevalence in commercial dairy herds using proviral load (PVL) and lymphocyte count (LC) measurements as indicators of the most infectious animals for culling or segregation. Bovine leukemia virus causes lymphoma in <5% of infected cattle, and increased lymphocyte counts (lymphocytosis) in about one-third. Recent research has shown that dairy cows infected with BLV have altered immune function associated with decreases in milk production and lifespan. Recent findings show that a minority of infected cattle have PVL concentrations in blood and other body fluids of over 1,000 times that of other infected cattle. In combination with a high LC, these animals are thought to be responsible for most transmission of BLV in a herd. Milk or blood samples from adult cows in our 3 Midwestern dairy farm field trials were tested semiannually with ELISA for BLV antibodies, and ELISA-positive cattle were then retested using a blood LC and a quantitative PCR test for PVL to identify the animals presumed to be most infectious. Herd managers were encouraged to consider PVL and LC status when making cull decisions, and to segregate cows with the highest PVL and LC from their BLV ELISA-negative herd mates where possible. After 2 to 2.5 yr of this intervention, the incidence risk of new infections decreased in all 3 herds combined, from 13.8 to 2.2, and the overall herd prevalence decreased in all 3 herds combined from 62.0 to 20.7%, suggesting that this approach can efficiently reduce BLV transmission as well as prevalence. This is encouraging, because a very low prevalence of BLV infection would make it economically feasible to cull the remaining ELISA-positive cattle, as was achieved in national eradication programs in other countries decades ago.

Infectious feline herpesvirus detected in distant bone and tendon following mucosal inoculation of specific pathogen-free cats

Emerging evidence suggests that cats infected with feline herpesvirus-1 (FHV-1) may experience a brief viremic phase. The objective of this study was to determine whether natural routes of FHV-1 inoculation could result in viremic transmission of infectious virus to connective tissues (cortical bone, tendon). Three specific pathogen-free cats were experimentally inoculated with FHV-1 via a combined mucosal (oronasal, ocular) route. Cats were euthanized at the peak of clinical signs to aseptically harvest tissues (cortical bone, tendon, trachea/tongue) for co-culture with a susceptible cell line to promote spread of infectious virus. Viral infection of Crandall-Rees feline kidney cells was microscopically visualized by cytopathic effect (CPE). Additionally, co-culture DNA was extracted either at the point of CPE or 16 days of culture without evidence of CPE, to amplify FHV-1 glycoprotein B gene using real-time PCR. Infectious virus was detected in distant cortical bone (two cats, moderate to severe clinical signs) and tendon (one cat, severe clinical signs). Direct infection of mucosal (trachea, tongue) tissues also was confirmed in these two cats. In contrast, all co-cultured tissues from the third cat (mild clinical signs) were negative for FHV-1 by CPE and PCR. Results of this study demonstrated that early primary FHV-1 viremia may be distributed to distant connective tissues.

Clinical features and risk factors for development of urinary tract infections in cats

The clinical and diagnostic features of 155 cats with urinary tract infection (UTI) and 186 controls with negative urine culture/s were characterized retrospectively (signalment, clinical signs, urinalysis, urine culture, concurrent diseases, lower urinary tract diagnostic/therapeutic procedures). Multivariable logistic regression was used to identify risk factors associated with UTI. Cats of all ages were affected by UTI with no sex/breed predisposition. Lower urinary tract signs were absent in 35.5% of cats with UTI. Pyuria and bacteriuria had sensitivities of 52.9% and 72.9%, and specificities of 85.5% and 67.7% for detection of UTI, respectively. Risk factors significantly associated with increased odds of UTI were urinary incontinence [odds ratio (OR) = 10.78, P = 0.0331], transurethral procedures (OR = 8.37, P <0.0001), urogenital surgery (OR = 6.03, P = 0.0385), gastrointestinal disease (OR = 2.62, P = 0.0331), decreased body weight (OR = 0.81, P = 0.0259) and decreased urine specific gravity (OR = 0.78, P = 0.0055). Whilst not independently significant, renal disease and lower urinary tract anatomic abnormalities improved statistical model performance and contributed to UTI.

Evaluation of modified Wright-staining of dried urinary sediment as a method for accurate detection of bacteriuria in cats

BACKGROUND

Urinary sediment examination and quantitative urinary culture results are frequently discordant.

OBJECTIVES

The aims of this study were to compare accuracy of light microscopic examination of wet-mounted unstained (wet-unstained) and air-dried modified Wright-stained (dry-stained) sedimented preparations of urine with results of quantitative aerobic bacterial culture for detection and characterization of bacteriuria in cats. In addition, the presence of pyuria detected by urinalysis and potential risk factors were assessed.

METHODS

A blinded prospective study was conducted on 472 urinary samples collected from 410 cats by cystocentesis. The age and sex of each cat were recorded. Complete urinalyses were performed and included quantification of WBCs. Quantity and morphology of bacteria in each specimen were determined by light microscopic examination of wet-unstained (performed by certified medical technologists) and dry-stained (performed by a veterinary clinical pathologist) sedimented preparations of urine and compared with results of quantitative bacterial cultures.

RESULTS

Of 472 urinary specimens, 29 were positive for bacteriuria by culture and considered true positives and 443 were considered true negatives. Compared with these results, examination of wet-unstained and dry-stained urines had sensitivities of 75.9% and 82.8%, specificities of 56.7% and 98.7%, and test efficiencies of 57.8% and 97.7%, respectively. Positive likelihood ratios were 1.8 and 63.7 and negative likelihood ratios were 0.42 and 0.17 for wet-unstained and dry-stained examinations, respectively. Compared with 29 culture-positive samples, the wet-unstained method had morphologic concordance and misclassification rates of 37.9% and 62.1%, respectively, whereas the dry-stained method had morphologic concordance and misclassification rates of 65.5% and 34.5%, respectively. Only 34% of samples with bacteriuria had pyuria. Frequency of bacteriuria was not significantly different based on age and sex of the cats, but there was a tendency for increased frequency in female cats and in cats >10 years old.

CONCLUSIONS

Staining dried urinary sediment with a modified Wright-stain significantly improved sensitivity, specificity, and test efficiency of microscopic detection and classification of bacteriuria compared with the wet-unstained method. Pyuria should not be a criterion for determining the presence or absence of bacteriuria.

Evaluation of modified Wright-staining of urine sediment as a method for accurate detection of bacteriuria in dogs

OBJECTIVE

To compare the findings of light microscopic evaluation of routine unstained wet-mounted preparations and air-dried, modified Wright-stained preparations of urine sediment with results of quantitative aerobic bacteriologic culture of urine.

DESIGN

Masked prospective study.

SAMPLE POPULATION

459 urine samples collected by cystocentesis from 441 dogs.

PROCEDURE

Urinalyses and quantitative bacteriologic cultures of urine were performed. Unstained wet-mounted preparations and air-dried, modified Wright-stained urine sediment preparations were examined by light microscopy for the presence of bacteria.

RESULTS

Compared with results of quantitative bacteriologic culture, routine unstained preparations and modified Wright-stained preparations had sensitivities of 82.4% and 93.2%, specificities of 76.4% and 99.0%, positive predictive values of 40.1% and 94.5%, negative predictive values of 95.8% and 98.7%, and test efficiencies of 77.3% and 98.0%, respectively. Compared with 74 samples that yielded growth on bacteriologic culture, the routine unstained method had concordance and misclassification rates of 39.2% and 60.8%, respectively, whereas the Wright-stained method had concordance and misclassification rates of 78.4% and 21.6%, respectively. Significant associations between each of occult blood in urine, pyuria, female sex, and lower urine specific gravity with bacteriuria detected by Wright-stained sediment examination and quantitative bacteriologic culture of urine were identified.

CONCLUSIONS AND CLINICAL RELEVANCE

Examination of modified Wright-stained preparations of urine sediment appeared to be a rapid, cost effective method that significantly improved the sensitivity, specificity, positive predictive value, and test efficiency of light microscopic detection of bacteriuria, compared with that of the routine unstained method.

Antiretroviral efficacy of a 98% solution of glycerol or ethylene oxide for inactivation of feline leukemia virus in bone

OBJECTIVE

To determine whether infectious retrovirus was inactivated in bones from FeLV-infected cats after ethylene oxide (ETO) sterilization or preservation in a 98% solution of glycerol in an in vitro cell culture system.

SAMPLE POPULATION

Metatarsal bones obtained from 5 FeLV-infected cats and cultured with feline fibroblast cells.

PROCEDURE

Metatarsal bones were treated with 100% ETO, a 98% solution of glycerol, or left untreated. Twenty-five flasks of feline fibroblast cells were assigned to 5 groups: negative control, positive control, ETO-treated bone, glycerol-treated bone, and untreated bone with 5 replicates/group for 4 passages. Media and cell samples were harvested from every flask at each passage to measure FeLV p27 antigen and the number of copies of provirus per 100 ng of DNA, respectively.

RESULTS

All negative control and ETO-treated group replicates were negative for FeLV p27 antigen and provirus throughout the study. All positive control group replicates were positive for FeLV p27 antigen and provirus at passages 1 to 4. Untreated bone group replicates were positive for FeLV p27 antigen at passages 3 and 4 and provirus beginning at passage 2. Glycerol-treated group replicates had delayed cell replication and were negative for FeLV p27 antigen and provirus at passages 1 to 4 and 2 to 4, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Ethylene oxide sterilization of bone from FeLV-infected cats appeared to abrogate transmission of infectious retrovirus and effectively sterilized bone allografts. Impact for Human Medicine-Additional studies to confirm effectiveness of ETO treatment of allograft tissues for prevention of pathogen transmission via transplantation are warranted.

Lyophilization does not inactivate infectious retrovirus in systemically infected bone and tendon allografts

BACKGROUND

A review of multiple transplantations of human immunodeficiency virus-infected musculoskeletal allografts found that recipients of lyophilized (freeze-dried) bone or tendon from an infected donor all tested negative for human immunodeficiency virus. The finding that 75% of the recipients of fresh-frozen bone from the same donor contracted human immunodeficiency virus has led to speculation that freeze-drying may render retroviral-infected musculoskeletal allografts noninfectious.

HYPOTHESIS

Lyophilization does not inactivate retrovirus in systemically infected bone and tendon.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendons and cortical bone segments from cats systemically infected with feline leukemia virus were used in this study. Feline embryonic fibroblast cells were cultured in the presence of fresh-frozen or freeze-dried cortical bone or tendon segments. At each passage, feline leukemia virus p27 antigen was measured in media by enzyme-linked immunosorbent assay, and feline leukemia virus (pro)viral nucleic acids were quantified by real-time quantitative polymerase chain reaction in the DNA extracted from cells.

RESULTS

Enzyme-linked immunosorbent assay results and quantitative polymerase chain reaction results demonstrated retroviral antigen and proviral DNA in all cultured cell replicates after exposure to fresh-frozen or freeze-dried bones or tendons.

CONCLUSION

Freeze-drying (lyophilization) of retroviral-infected cortical bone and tendon does not inactivate retrovirus.

CLINICAL RELEVANCE

These results conclusively demonstrate that freeze-drying should not be relied on to inactivate infectious retrovirus in systemically infected musculoskeletal allografts.

Clinical evaluation of a leukocyte esterase test-strip for detection of feline pyuria

Commercial macroscopic test-strips (dipsticks) that indirectly detect urine leukocytes by quantifying leukocyte esterase (LE) activity have been advocated as a simple, rapid, and inexpensive alternative to microscopic examination for detection of significant pyuria in urine specimens. The purpose of this study was to evaluate the diagnostic performance of a commercial LE test-strip for detection of feline pyuria. Two hundred and thirteen consecutive urine specimens were collected from 188 different feline patients and analyzed for LE activity with a LE test-strip (Multistix 2 Reagent Strips:Ames Division, Bayer Corp., Elkhart, IN). Results of the LE test-strip were compared with those of standard urine biochemical and microscopic sediment evaluations. Compared with urine sediment leukocyte counts, the LE test-strip had a sensitivity of 77%, a specificity of 34%, positive and negative predictive values of 14 and 91 % respectively, and an overall test efficiency of 39%. Multivariable logistic regression analysis did not reveal significant associations between pyuria (>5 WBC/hpf) and a positive LE test- strip reaction; however, hematuria, lipiduria, increasing age, and decreasing urine specific gravity were associated with a significantly increased risk for positive LE test-strip reactions. We conclude that the LE test-strip evaluated in this study is highly nonspecific for detection of significant pyuria in feline urine specimens and should not replace routine microscopic urine sediment examination in this species.

Demineralization for inactivation of infectious retrovirus in systemically infected cortical bone: in vitro and in vivo experimental studies

BACKGROUND

Clinical and experimental studies have demonstrated viral transmission through the transplantation of fresh-frozen infected bone. While sterilization methods sufficient to inactivate the human immunodeficiency virus (HIV) have been shown to markedly alter osteoconductive and osteoinductive properties of bone allografts, the ability of a process for creating demineralized bone matrix to abrogate transmission of a retrovirus has not been investigated, to our knowledge. We hypothesized that a clinically accepted demineralization procedure would alter the nucleic acids of the feline leukemia virus (FeLV, a retrovirus with a structure and replication cycle similar to those of HIV), inactivating the virus in infected bone and rendering it noninfectious.

METHODS

Bone infected with FeLV was demineralized with a method employed for creating demineralized bone matrix powder. The effects of demineralization on cellular and (pro)viral nucleic acids were examined with use of gel electrophoresis and quantitative polymerase chain reaction, respectively. To compare the infectivity of the demineralized bone matrix with that of mineralized bone particles in cell cultures and in animals in which they had been implanted, we measured FeLV p27 antigen and (pro)viral nucleic acids as well as antiviral antibodies.

RESULTS

Demineralization of FeLV-infected bone appeared to inactivate the virus by degradation and fragmentation of the DNA, rendering it noninfectious in both in vitro and in vivo test systems. In contrast, untreated mineralized FeLV-infected bone contained intact nucleic acids and readily transmitted the virus in both test systems.

CONCLUSIONS

The demineralization process inactivated infectious retrovirus in infected cortical bone, thereby preventing disease transmission.

Serum and plasma latex agglutination tests for detection of fibrin(ogen) degradation products in clinically ill dogs

An increased concentration of fibrin(ogen) degradation products (FDPs) commonly is used in conjunction with other hemostatic test abnormalities to identify patients with disseminated intravascular coagulation (DIC). Positive FDP results, however, have been observed in dogs without clinical evidence of DIC. The purpose of this study was to evaluate FDP concentrations in a group of clinically ill dogs with a variety of disorders. Dogs included in the study had the following hemostatic parameters evaluated: prothrombin time, activated partial thromboplastin time, fibrinogen concentration, platelet count, and FDP concentration. Two rapid latex agglutination methods were compared for detecting FDP in serum samples (Thrombo-Wellcotest, International Murex Technologies Corp) and plasma samples (FDP Plasma, American Bioproducts Inc). Results of the serum FDP method were positive in 8% (4/50) of the dogs tested: 3 with DIC and 1 with immune-mediated hemolytic anemia and liver disease. Results of the plasma FDP test were positive in 60% (30/50) of the animals tested: 6 with DIC, 3 with confirmed thrombosis, and 21 with a variety of conditions, including neoplasia, immune-mediated hemolytic anemia, pancreatitis, gastric dilatation-volvulus, heat stroke, severe trauma, sepsis, protein-losing nephropathy, liver disease, hyperadrenocorticism, and chronic heart failure. Because the plasma FDP test was positive more frequently than the serum FDP test in ill dogs, it may be more sensitive for the detection of canine FDP.

Prevalence of bovine herpesvirus-4 infection in cats in Central Michigan

The gammaherpesvirus bovine herpesvirus-4 (BHV-4) has been isolated from a wide variety of animals, including lions and domestic cats. Although BHV-4 antibodies have been detected in normal cats and cats with urinary disorders, the epidemiology and pathogenic role of BHV-4 in cats is unknown. The purpose of this study was to determine the prevalence of BHV-4 antibodies and viral nucleic acid in a population of free-roaming cats. Plasma and peripheral blood leukocyte samples were collected from 52 male and 52 female free-roaming cats impounded at a regional animal control facility in Central Michigan. Plasma concentrations of BHV-4 antibodies were measured with an indirect fluorescent antibody test. Peripheral blood leukocyte DNA was isolated, and a 2-stage polymerase chain reaction with heminested primers delineating a conserved portion of the BHV-4 glycoprotein B gene homologue was used to amplify BHV-4-specific DNA sequences. BHV-4 antibodies were detected in 38 (73%) male and 23 (44%) female cats. Seropositive cats were significantly more likely to be male than female (odds ratio = 3.22; P = .007). Cell-associated viremia was detected in 17 (33%) male and 11 (21%) female cats. Of the 61 seropositive cats, 23 (38%) had a detectable viremia; only 5 (12%) seronegative cats had detectable viremia. Seropositive cats were significantly more likely to be viremic than seronegative cats (OR = 4.30: P = .009). Our results suggest that BHV-4 infection may be more widespread in certain cat populations than previously reported. Furthermore, many cats seropositive for BHV-4 antibodies have a concurrent cell-associated viremia.

Effects of a 98% solution of glycerol or sterilization with ethylene oxide on FeLV in bone allografts and effects on bone incorporation of allografts in cats

OBJECTIVES

To compare virucidal effects and bone incorporation properties of cortical bone allografts transplanted into specific-pathogen-free (SPF) cats. Allografts consisted of untreated bone from a SPF cat (negative-control group) and bone from 5 FeLV-infected cats that was subjected to sterilization with ethylene oxide (ETO), preservation with glycerol, or no treatment (positive-control group).

SAMPLE POPULATION

Bones from the aforementioned groups and twenty 8-week-old SPF cats (5 cats/group) implanted with an allograft from 1 of the aforementioned groups.

PROCEDURE

After implantation, blood samples were collected weekly to monitor FeLV p27 antigen and antibody titers. Quantification of FeLV provirus was performed on blood samples at weeks 0, 4, and 8 and donor bone samples at time of implantation. Cats were euthanatized 8 weeks after transplantation, and graft sites were evaluated.

RESULTS

All results for negative-control cats were negative. All ETO group cats had negative results for antigen and provirus in blood, whereas 1 cat had a low antibody titer. Although 3 ETO-treated allografts were positive for provirus, the DNA appeared denatured. One cat in the glycerol group had positive results for all tests in blood samples. All glycerol-preserved allografts were positive when tested for provirus. All results for positive-control group cats were positive. Differences in incorporation of bone grafts were not observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Glycerol preservation of FeLV-infected bone allografts did not eliminate transmission of retrovirus to recipients. In contrast, ETO sterilization appeared to denature DNA and prevent infection. Treatments did not affect incorporation of bone grafts in young cats.

Calcium oxalate crystalluria in a goat

As part of a routine health evaluation of an 8-month-old female Nubian goat, serum biochemical analyses and urinalysis were performed. Most serum biochemical values including concentrations of blood calcium and indicators of urinary system dysfunction, such as blood urea nitrogen, creatinine, and phosphorous concentrations, were within reference ranges. An aliquot of voided urine was hypersthenuric and acidic and contained numerous typical cuboidal-bipyramidal calcium oxalate dihydrate crystals and unique rectangular parallelepiped crystals that were confirmed by energy dispersive X-ray microanalysis as being of calcium oxalate dihydrate composition. We hypothesize that the calcium oxalate crystals resulted from a diet containing calcium and oxalic acid. Treatment was not administered, and the goat remained healthy during the ensuing year.

A potentially misleading presentation and course of acute myelomonocytic leukemia in a dog

A nine-year-old, castrated male golden retriever had lethargy, fever, massive peripheral lymphadenomegaly, hepatosplenomegaly, and pale mucous membranes. There was a marked leukocytosis (456.3 x 10(3) cells/microliter) with 99% blasts; a moderate, nonregenerative anemia; and marked thrombocytopenia. A tentative diagnosis of acute lymphocytic leukemia was made pending results of cytochemical staining. Despite the severity of the laboratory and clinical findings, the dog exhibited a partial response to an induction chemotherapy protocol commonly used for lymphoma. Subsequent cytochemical staining of the original blood and bone-marrow samples resulted in a revised diagnosis of acute myelomonocytic leukemia (AML-M4). Clinicopathological findings, response to treatment, and clinical outcome in this case of canine AML-M4 are discussed.

Retroviral transmission in bone allotransplantation. The effects of tissue processing

The transmission of a retrovirus through transplantation of processed bone allografts was studied using the feline leukemia virus. The long bones of 4 previously infected donor cats were harvested and assigned to 1 of 3 treatment groups: single freeze/thaw cycle, double freeze/thaw cycle, or double freeze/thaw cycle with water flush to remove bone marrow. Cortical bone grafts and corticocancellous bone grafts from each treatment group were transplanted into individual specific-pathogen-free recipients. Samples of plasma were obtained weekly from all recipients and were tested with an enzyme-linked immunosorbent assay to detect viral antigen. For animals that tested consistently negative for viral antigen, plasma samples also were tested for antiviral antibody to feline leukemia virus measured by live cell immunofluorescence. The results of the antigen and antibody testing revealed that all of the cortical and corticocancellous bone allografts in each of the 3 treatment groups transmitted virus. The ability of the treated bone allografts to transmit a feline retrovirus suggests that routine processing and removal of bone marrow may not inhibit their ability to transmit other retroviruses, such as the human immunodeficiency virus.

Lipopolysaccharide induces monocyte chemoattractant protein production by rat mesangial cells

Lipopolysaccharide, a potent pro-inflammatory constituent of bacterial cell walls, is capable of promoting glomerular inflammation, by both activating circulating inflammatory cells and local interactions with renal parenchymal cells. We sought to determine whether lipopolysaccharide was capable of promoting glomerular inflammation by directly stimulating mesangial cell production of monocyte chemoattractant protein 1, a recently described cytokine capable of eliciting recruitment of mononuclear phagocytes into inflammatory foci. Northern hybridization analysis revealed dose and time-dependent induction of mRNA coding for monocyte chemoattractant protein 1 in quiescent rat mesangial cells treated with lipopolysaccharide. Lipopolysaccharide-elicited induction of monocyte chemoattractant protein mRNA was detectable after 1 hour and persisted for at least 30 hours. Media isolated from rat mesangial cell cultures stimulated by lipopolysaccharide possessed monocyte chemotactic activity that was detectable at 8 hours and peaked at 24 hours; an antimonocyte chemoattractant protein antibody blocked 87% of this chemotactic activity. We suggest that lipopolysaccharide, released from bacterial cell walls, promotes glomerular inflammation by stimulating mesangial cell production of monocyte chemoattractant protein 1.

Retroviral transmission by the transplantation of connective-tissue allografts. An experimental study

The transmission of a retrovirus by the transplantation of allografts of connective tissues was studied in a feline model with use of the feline leukemia virus, a retrovirus with a replication cycle and pathological characteristics similar to those of the human immunodeficiency virus. The retrovirus was used to infect four specific-pathogen-free cats that were subsequently used as tissue donors. Fresh allografts of menisci, patellar ligaments, and patellar ligament and bone composites were harvested from infected donors and were transplanted into the knee joints of twelve specific-pathogen-free cats. A fresh cancellous-bone allograft was transplanted into the proximal part of the tibia of four additional specific-pathogen-free cats, which served as positive control animals. Additional grafts from infected donors were harvested and were stored at -80 degrees Celsius for ten weeks. A fresh-frozen graft was then transplanted into the knee of twelve other specific-pathogen-free cats. Samples of plasma were obtained weekly from all twenty-eight cats and were tested with both an enzyme-linked immunosorbent assay to detect the presence of viral antigen and an immunofluorescent antibody assay to determine exposure to the virus. All types of fresh and fresh-frozen connective-tissue allografts from the infected donors resulted in transmission of the retrovirus to the recipient cats. The recipients had evidence of viral antigen or rising antibody titers as early as two weeks after the transplantation. Histological examination of specimens of the allografts revealed normal incorporation of the transplanted tissues, with no sign of rejection of the graft.

Pre- and postexposure chemoprophylaxis: evidence that 3'-azido-3'-dideoxythymidine inhibits feline leukemia virus disease by a drug-induced vaccine response

The benefits of postexposure 3'-azido-3'-dideoxythymidine (AZT) prophylaxis following human immunodeficiency virus exposure are unknown. We describe a comprehensive assessment of pre- and postexposure AZT therapy in the feline leukemia virus (FeLV)-cat model for AIDS which included in vitro testing, an in vivo dose-response titration, a postexposure treatment study, plasma drug concentration determinations, and evaluation of the immune response to FeLV. In in vitro studies, AZT prevented FeLV infection of a feline T-lymphoid cell line, giving 50 and 90% inhibition concentrations of 4.6 and 11.1 mM, respectively. In all of the in vivo efficacy studies, AZT was administered by continuous subcutaneous infusion for 28 days. AZT toxicity was excessive at a dosage of 120 mg/kg of body weight per day, causing acute anemia, but AZT was tolerable at 60 mg/kg/day. In preexposure studies, AZT was efficacious in preventing chronic antigenemia at a dosage of > or = 15 mg/kg/day, at which plasma AZT concentrations averaged between 0.51 and 0.81 micrograms/ml (2.13 and 3.03 microM). As a postexposure treatment, at 60 mg/kg/day, AZT prevented chronic FeLV antigenemia when treatment was started up to 96 h post-virus inoculation (p.i.), but not when treatment was started at 192 h p.i. The 4-day period between 96 and 192 h p.i. appears to be critical for establishing chronic viremia. It is presumed that the increase in virus load between 4 and 8 days p.i. was able to overwhelm the immunologic functions responsible for containment of FeLV infection, even though AZT therapy effectively controlled viremia during the treatment period. The antibody response to FeLV varied depending on the time of AZT treatment initiation relative to virus challenge. When AZT treatment was started 48 h before or 8 h after FeLV challenge, antibodies to FeLV were not detected until after AZT treatment was discontinued at 28 days p.i. Following AZT treatment, however, antibody titers rapidly increased at a rate suggestive of a secondary immune response. When AZT treatment was initiate at later time points relative to virus challenge (24, 48, and 96 h p.i.), antibodies to FeLV became detectable during the treatment period. These results indicate that AZT treatment does not completely prevent FeLV infection, even when treatment begins before virus challenge, and that immune sensitization to FeLV proceeds during the prophylactic drug treatment period.

Prophylactic and therapeutic effects of phosphonoformate against feline leukemia virus in vitro

Phosphonoformate (PFA), a noncompetitive inhibitor of reverse transcriptase (RT), inhibited feline leukemia virus (FeLV) infection of 2 feline cell lines and inhibited progeny virus RT activity in a chronically FeLV-infected cell line. Feline leukemia virus infection of 3201 cells, an FeLV-negative lymphoma cell line, was inhibited by greater than 70% at a concentration of only 1 microM PFA and by greater than 90% at concentrations of 64 to 256 microM PFA, as evidenced by RT activity. However, FeLV antigen expression by 3201 cells remained relatively constant over noncytotoxic concentrations of PFA. Because the persistence of viral antigen expression with concomitant suppression of RT activity appears to be unique and because 3201 cells express small amounts of an endogenous retrovirus (RD-114) and contain endogenous FeLV proviral sequences, a possible role of endogenous retroviruses acting as helper viruses was suggested. Feline leukemia virus infection of 81C cells, a sarcoma-positive, leukemia-negative fibroblast cell line, was inhibited by greater than 50% at a concentration of 64 microM PFA and by greater than 98% at concentrations of 256 to 512 microM PFA, as indicated by suppression of focus formation. The feline lymphoid cell line FL-74 is a large producer of FeLV. When FL-74 cells were cultured in the presence of 256 microM PFA, virus production (virus budding and viral antigen) was not affected, but progeny virus lost RT activity and infectivity. Direct addition of PFA (256 microM) to FeLV also reduced RT activity and infectivity. These data indicate that PFA can directly and rapidly inactivate retrovirus independent of cellular processing, presumably by inhibiting RT.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of antiviral activity and toxicity of dextran sulfate in feline leukemia virus-infected cats

The feline leukemia virus (FeLV) disease model was used to conduct a toxicity and antiretrovirus efficacy trial of dextran sulfate (DS; molecular mass, 7,000 to 8,000 Da). In vitro, FeLV infection of feline lymphoid cells was inhibited by 10 micrograms of DS per ml. DS was administered to cats by continuous intravenous infusion at doses of 600, 120, 24, or 4.8 mg/kg of body weight per day, beginning 24 h before FeLV challenge. Doses of 24 mg/kg/day and more were excessively toxic, causing intestinal lesions and death. Similar changes were observed in unchallenged animals receiving 24 mg/kg/day, indicating that toxicity was DS mediated. The dosage of 4.8 mg/kg/day was subtoxic but did not prevent the induction and persistence of FeLV viremia. The results demonstrate that DS by continuous intravenous infusion is excessively toxic at high doses and ineffective at preventing FeLV infection at a subtoxic dose in the FeLV cat model.

Age-related differences in phosphonoformate-induced bone toxicity in cats

Phosphonoformate (PFA), a monophosphonate pyrophosphate analog, caused plasma biochemical and bone histomorphologic abnormalities in cats given 1,000 mg/kg/day as a continuous intravenous infusion for 14 days. Plasma biochemical alterations observed in young cats (10 weeks old) treated with PFA included increased calcium and decreased phosphorus, alkaline phosphatase, and calcitriol. Young cats treated with PFA developed rickets-like lesions characterized by widened growth plates, increased osteoid, and failure of mineralization. In addition, area of mineralized trabecular bone was decreased. Osteoclast size was increased whereas osteoclast perimeter and number were unaffected in young PFA-treated cats. Plasma alkaline phosphatase was decreased in adult cats (greater than or equal to 1 year old) treated with PFA but changes in calcium, calcitriol, and immunoreactive parathyroid hormone were highly variable and not significantly different. Adult cats treated with PFA exhibited osteomalacia characterized by increased osteoid area, perimeter, and width with failure of mineralization. In addition, static resorption indices were increased in PFA-treated adult cats but area of mineralized trabecular bone was not decreased. The monophosphonate PFA inhibited bone mineralization in young and adult cats similar to bisphosphonate treatment in other species. Because PFA is currently in phase I trials for use in AIDS, results of this study suggest a need to evaluate patients treated with PFA for metabolic bone disease.

Monocyte chemotaxis and activating factor production by keratinocytes in response to IFN-gamma

Monocytes accumulate in the epidermis and along the dermo-epidermal junction in several different inflammatory skin diseases. To determine whether human epidermal keratinocytes elaborate a specific chemotaxin responsible for the accumulation of monocytes at these anatomic sites, monocyte chemotactic activity in conditioned 16-h cultured keratinocyte supernatants were assayed using human peripheral blood monocytes as the target cell. Dilutional analysis revealed directed monocyte migration in IFN-gamma-treated (100 U/ml) keratinocyte supernatants (80% maximal FMLP response) which was 10-fold more than IFN-gamma itself or untreated keratinocyte activity alone. Gel filtration chromatography revealed that this activity eluted just ahead of a 12.5-kDa molecular mass marker. Blocking studies demonstrated that a rabbit polyclonal antibody to monocyte chemotaxis and activating factor (MCAF) inhibited all monocyte chemotaxis by greater than 80%. Keratinocytes were metabolically labeled with 35S-cysteine/methionine, and after 16 h incubation the supernatants immunoprecipitated with the same anti-MCAF antibody. MCAF was detected as a protein doublet of 12 and 9 kDa only in IFN-gamma-treated (100 U/ml) keratinocyte supernatants. Incubation with IFN-gamma and TNF-alpha (250 U/ml) in combination resulted in increased production of MCAF protein. By Northern blot analysis, MCAF mRNA was constitutively expressed in keratinocytes and upregulated only in the presence of IFN-gamma. TNF-alpha, IL-1 beta, transforming growth factor-beta and phorbol esters had no positive or negative influence on MCAF mRNA. These studies demonstrate that biologically active MCAF is elaborated by human epidermal keratinocytes upon activation by IFN-gamma, a cytokine also required for the induction of adherence between monocytes and keratinocytes. Keratinocyte-derived MCAF is likely to be important in the regulation of cutaneous monocyte trafficking and may also be responsible for the recruitment of Langerhans cells and dermal dendrocytes, which share many phenotypic features with monocytes/macrophages, to their anatomic locations in skin.

Monocyte chemotaxis and activating factor production by keratinocytes in response to IFN-gamma

Monocytes accumulate in the epidermis and along the dermo-epidermal junction in several different inflammatory skin diseases. To determine whether human epidermal keratinocytes elaborate a specific chemotaxin responsible for the accumulation of monocytes at these anatomic sites, monocyte chemotactic activity in conditioned 16-h cultured keratinocyte supernatants were assayed using human peripheral blood monocytes as the target cell. Dilutional analysis revealed directed monocyte migration in IFN-gamma-treated (100 U/ml) keratinocyte supernatants (80% maximal FMLP response) which was 10-fold more than IFN-gamma itself or untreated keratinocyte activity alone. Gel filtration chromatography revealed that this activity eluted just ahead of a 12.5-kDa molecular mass marker. Blocking studies demonstrated that a rabbit polyclonal antibody to monocyte chemotaxis and activating factor (MCAF) inhibited all monocyte chemotaxis by greater than 80%. Keratinocytes were metabolically labeled with 35S-cysteine/methionine, and after 16 h incubation the supernatants immunoprecipitated with the same anti-MCAF antibody. MCAF was detected as a protein doublet of 12 and 9 kDa only in IFN-gamma-treated (100 U/ml) keratinocyte supernatants. Incubation with IFN-gamma and TNF-alpha (250 U/ml) in combination resulted in increased production of MCAF protein. By Northern blot analysis, MCAF mRNA was constitutively expressed in keratinocytes and upregulated only in the presence of IFN-gamma. TNF-alpha, IL-1 beta, transforming growth factor-beta and phorbol esters had no positive or negative influence on MCAF mRNA. These studies demonstrate that biologically active MCAF is elaborated by human epidermal keratinocytes upon activation by IFN-gamma, a cytokine also required for the induction of adherence between monocytes and keratinocytes. Keratinocyte-derived MCAF is likely to be important in the regulation of cutaneous monocyte trafficking and may also be responsible for the recruitment of Langerhans cells and dermal dendrocytes, which share many phenotypic features with monocytes/macrophages, to their anatomic locations in skin.

Chylothorax in cats: 37 cases (1969-1989)

Case records of 37 cats with chylothorax examined at 2 institutions were retrospectively evaluated. Dyspnea and coughing were the most common abnormalities noticed by the owners, and most cats were dyspneic on initial examination. There was no statistically significant difference in the gender distribution of cats studied when compared with reference populations; however, purebred cats appeared to be overrepresented in the study population. Four of the cats had unilateral pleural effusion (2 left side, 2 right side) and 9 cats had effusions that were primarily, but not exclusively, on the right side. Surgery was performed on 20 cats. Fifteen cats underwent thoracic duct or cisterna chyli ligation; 20% had complete resolution of pleural fluid. There was no significant difference in the survival rate of cats that underwent thoracic duct ligation and those that were treated by other means. Six cats had mesenteric lymphangiography performed; 2 cats had normal results, and the remainder had various degrees of thoracic lymphangiectasia. Two cats in which pleuroperitoneal shunts were placed and 2 of 3 cats that underwent pleurodesis were euthanatized or died after surgery.

In vitro and in vivo evidence that the antiviral activity of 2',3'-dideoxycytidine is target cell dependent in a feline retrovirus animal model

2',3'-Dideoxycytidine (DDC) was evaluated for prophylactic antiviral activity in vitro and in vivo, using the feline leukemia virus (FeLV)-cat animal model. In vitro antiviral activity of DDC against FeLV was dependent upon the target cell used for infection. DDC (5 to 10 microM) inhibited FeLV infection of feline lymphoid cells by greater than 80%, while 6.07 to 12.13 microM DDC was required to similarly inhibit infection of feline fibroblasts. However, 43 to 384 microM DDC was needed to inhibit FeLV infection of primary bone marrow cells by greater than 80%. These in vitro results suggest that, although relatively low doses of DDC may be adequate to prevent infection of feline lymphoid cells, 8- to 80-times-higher doses may be necessary to block infection of bone marrow cells, a primary target cell type for FeLV infection. In vivo studies with DDC consisted of pharmacokinetic and toxicity determinations and evaluation of the prophylactic antiviral activity against FeLV in cats. Clearance and half-life values for DDC in cats were 6.5 ml/min per kg and 54.7 min, respectively. In the prophylactic studies, DDC was administered by continuous intravenous infusion at doses of 22, 15, 10, and 5 mg/kg per h for 28 days in most animals. Cats were challenged intravenously with FeLV 1 to 3 days after drug treatment began. Doses of 22 and 15 mg/kg per h were extremely toxic, causing death in 8 of 10 cats. The mg/kg per h dose was slightly toxic, causing chronic progressive thrombocytopenia over the 28-day treatment period. Of 10 cats given 10 to 5 mg of DDC per kg per h, only one was completely protected from FeLV antigenemia. However, conversion to positive FeLV antigenemia status was delayed by 2 to 7 weeks in seven of nine remaining animals. Interestingly, FeLV infection of bone marrow cells, as indicated by FELV antigen in peripheral blood neutrophils, was only slightly delayed by 0 to 2 weeks, except in the case of the one protected cat, and usually preceded conversion to antigenemia. This pattern of neutrophils becoming antigen positive before detection of antigenemia was not seen in FeLV challenge control animals and indicates that the antiviral activity of DDC may be incomplete during DDC treatment. Results of our in vitro and in vivo studies suggest that feline bone marrow cells may remain partially susceptible to FeLV infection at tolerated doses, while other somatic target tissues (i.e., lymphoid or epithelial tissues) may be protected from infection. Incomplete inhibition of FeLV infection permitted focal bone marrow infection to develop in cats given DDC. These loci of infection served as virus reservoirs which, subsequent to discontinuation of DDC treatment, permitted spread of infection to tissues previously protected during treatment.

Age-related differences in pharmacokinetics of phosphonoformate in cats

Phosphonoformate (PFA) is a simple PPi analog which inhibits the activities of a variety of viral DNA polymerase, RNA polymerase, and reverse transcriptase enzymes. PFA is a topical and parenteral treatment for human herpesvirus infections and is currently in phase I trials for treatment of acquired immunodeficiency syndrome. Pharmacokinetic properties of PFA in young (growing) and adult specific-pathogen-free cats were compared. Mean PFA clearance from plasma was twofold higher in young cats (7.52 ml/min per kg of body weight) than in adult cats (3.70 ml/min per kg). Higher PFA clearance from plasma observed in young cats may result from higher renal clearance or enhanced accumulation of PFA in bone tissue of young versus adult cats. No plasma protein binding of PFA was observed. Mean oral bioavailability was 35% in young cats. These data indicate that age-related differences in PFA clearance from plasma occur in cats.

Prevalence of disease in nonviremic cats previously exposed to feline leukemia virus

Feline leukemia virus status and antibody titer to feline oncornavirus-associated cell membrane antigen (FOCMA) were determined on plasma from 183 outpatient cats and 61 cats from 2 closed, FeLV-positive, multiple-cat households. Cats with FOCMA antibody titer had a significantly (P less than 0.02) higher prevalence of history of disease than did cats without FOCMA antibody. Diseases included upper respiratory tract infections, abscesses, ear infections, lower urinary tract infections, gastrointestinal disease, pneumonia, uterine infection, lymphadenopathy, fever of unknown origin, and bacterial infections. The FOCMA antibody titer was determined by use of an indirect fluorescent antibody test; titer greater than or equal to 1:16 was considered to be positive results. Lower mean FOCMA antibody titer was observed in young cats with history of disease (P less than 0.05) than in young cats without history of disease or in older cats with or without history of disease. Prevalence of FOCMA antibody titer was identical (38%) in young and adult cats, indicating cats likely were exposed to FeLV as kittens because a higher prevalence of FOCMA antibody titer in older cats would otherwise be expected.

Visceral leishmaniasis in an English foxhound from an Ohio research colony

Visceral leishmaniasis was diagnosed in a 5-year-old English Foxhound born and housed in an Ohio research colony. Physical examination revealed pyrexia, hematochezia, panuveitis, splenomegaly, and lymphadenopathy. Hematologic and serum biochemical abnormalities consisted of anemia, thrombocytopenia, hypoalbuminemia, hyperglobulinemia, azotemia, and proteinuria. Postmortem examination revealed widely disseminated (spleen, bone marrow, lymph node, liver, kidney, lungs) Leishmania amastigotes within macrophages.

Sensitivity and specificity of canine serum total amylase and isoamylase activity determinations

Serum isoamylases were determined prospectively in dogs with pancreatic and extrapancreatic diseases. Mean serum isoamylase determinations were significantly different (p less than 0.05) between normal dogs and dogs with pancreatitis and exocrine pancreatic insufficiency. The sensitivity of serum isoamylase determination exceeded that of total amylase activity for the diagnosis of pancreatitis. Serum isoamylase determinations were less influenced by extrapancreatic diseases compared to total amylase activity when used in the diagnosis of pancreatic disease. Neither serum isoamylase determination nor total amylase activity had adequate sensitivity to support their use in the diagnosis of exocrine pancreatic insufficiency. There were significant (p less than 0.05) linear correlations between isoamylase determinations, total amylase activity, and trypsin-like immunoreactivity concentration.