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1.
The purpose of this investigation was to characterize the shedding pattern of feline leukemia virus (FeLV) RNA in saliva, and to correlate it with the proviral load in whole blood, viral load in plasma, levels of p27 in saliva and plasma, the isolation of infectious FeLV from saliva, and the titers of FeLV-specific antibodies of the IgG and IgA isotypes. We evaluated 24 experimentally FeLV-infected cats for these parameters using real-time RT-PCR and PCR, cell culture assay and sandwich ELISA. We observed that shedding of viral RNA in saliva was a consistent feature in viremic cats. Latently FeLV-infected cats, displaying a very low proviral load, did not shed infectious virus in saliva, but occasionally shed viral RNA. Consequently, salivary shedding of FeLV RNA may not necessarily indicate a transmission potential for susceptible cats. This study also confirmed previous results from our laboratory, showing that a negative result for p27 in plasma, or for viral RNA in plasma or saliva does not exclude FeLV infection, considering that blood cells from those cats contained provirus. We also showed that FeLV RNA and DNA were stable for more than 64 days in saliva samples stored at room temperature. We conclude that the detection of FeLV RNA in saliva may be a useful indicator of viremia, and that the detection of salivary viral RNA by RT-PCR could become a reliable tool for the diagnosis of FeLV infection, which is facilitated by the low invasive method of collection of the samples.  相似文献   

2.
Although it is assumed that fecal shedding of feline leukemia virus (FeLV) constitutes a transmission potential, no study has been performed showing that feces of infected cats can be a source of infection. In this study, we investigated fecal viral shedding of FeLV and its role in viral pathogenesis with the goal to improve infection control. FeLV RNA and DNA levels were determined in rectal swabs of experimentally infected cats by real-time PCR, and the results were correlated with proviral and viral loads in whole blood and plasma, respectively, and plasma p27 levels. All antigenemic cats shed FeLV RNA and DNA in feces. To determine whether the viral RNA detected was infectious, virus isolation from feces was also performed. Infectious virus was isolated from feces of antigenemic cats, and these results perfectly correlated with the isolation of virus from plasma. Na?ve cats exposed to these feces seroconverted, showing that infection through feces took place, but remained negative for the presence of FeLV provirus and p27 in blood, an outcome so far not described. Some of the organs collected after euthanasia were provirus positive at low copy numbers. From these results it is concluded that fecal shedding of FeLV plays a role in transmission, but it is probably of secondary importance in viral pathogenesis. Nevertheless, sharing of litter pans by susceptible and viremic cats could increase the environmental infectious pressure and appropriate measures should be taken to avoid unnecessary viral exposure.  相似文献   

3.
In felids, feline leukemia virus (FeLV) infection results in a variety of outcomes that range from abortive (virus readily eliminated and never detectable) to progressive infection (persistent viremia and viral shedding). Recently, a novel outcome was postulated for low FeLV infectious doses. Naïve cats exposed to faeces of persistently infected cats seroconverted, indicating infection, but remained negative for provirus and p27 antigen in blood. FeLV provirus was found in some tissues but not in the bone marrow, infection of which is usually considered a necessary stage for disease progression. To investigate the impact of low FeLV doses on young cats and to test the hypothesis that low dose exposure may lead to an unknown pathogenesis of infection without involvement of the bone marrow, 21 cats were infected oronasally with variable viral doses. Blood p27, proviral and viral loads were followed until week 20 post-infection. Tissue proviral loads were determined as well. The immune response was monitored by measuring FeLV whole virus and p45 antibodies; and feline oncornavirus-associated cell membrane antigen (FOCMA) assay. One cat showed regressive infection (transient antigenemia, persistent provirus-positivity, and seroconversion) with provirus only found in some organs at sacrifice. In 7 of the 20 remaining cats FOCMA assay positivity was the only sign of infection, while all other tests were negative. Overall, the results show that FeLV low dose exposure can result in seroconversion during a presumed abortive infection. Therefore, commonly used detection methods do not detect all FeLV-infected animals, possibly leading to an underestimation of the prevalence of infection.  相似文献   

4.
Most studies that investigate the prevalence of infections with feline leukemia virus (FeLV) are based on the detection of p27 antigen in blood, but they do not detect proviral DNA to identify the prevalence of regressive FeLV infections. The aim of the present study was to assess the prevalence and status of FeLV infection in cats in Southern Germany. P27 antigen enzyme-linked immunosorbent assay (ELISA), anti-p45 antibody ELISA, DNA polymerase chain reaction (PCR) of blood and RNA PCR of saliva were performed. Nine out of 495 cats were progressively (persistently) infected (1.8%) and six were regressively (latently) infected (1.2%). Cats with regressive infections are defined as cats that have been able to overcome antigenemia but provirus can be detected by PCR. Twenty-two unvaccinated cats likely had abortive infections (regressor cats), testing FeLV antigen- and provirus-negative but anti-p45 antibody-positive. Most of the FeLV-vaccinated cats did not have anti-FeLV antibodies. Both progressive, as well as regressive infections seem to be rare in Germany today.  相似文献   

5.
FeLV was discovered 40 years ago and vaccines have been commercially available for almost two decades. So far, most FeLV pathogenesis and vaccine studies were conducted assaying parameters, such as virus isolation and antigen detection. Accordingly, regressive infection was characterized by transient or undetectable viremia, while persistent viremia is typically observed in cats with progressive infection. Using real-time polymerase chain reaction assays, the spectrum of host response categories to FeLV infection was recently refined by investigating proviral and plasma viral RNA loads. Cats believed to be immune to FeLV infection were found to turn provirus-positive after virus exposure. Moreover, efficacious FeLV vaccines were found unable to prevent provirus-integration and minimal viral replication. Remarkably, no difference was found in initial proviral and plasma viral RNA loads between cats with different infection outcomes. Only subsequently, the infection outcome is associated with FeLV loads. FeLV provirus was found to persist for years; reoccurrence of viremia and disease development was observed in some cats. Thus, aviremic provirus-positive cats are FeLV carriers and, following reactivation, may act as an infection source. However, integrated viral DNA may also be essential for solid protection and long-lasting maintenance of protective immunity. In conclusion, real-time TaqMan PCR and RT-PCR assays are highly sensitive and specific. They yield a more sensitive measure for FeLV exposure than antigen detection, virus isolation or immunofluoresence assays. We recommend the use of real-time PCR assays to identify FeLV exposed cats, particularly in catteries, and investigate obscure clinical cases that may be FeLV-associated. The use of sensitive molecular methods will contribute to a more in-depth understanding of the FeLV pathogenesis.  相似文献   

6.
Cats exposed to feline leukemia virus (FeLV), a naturally occurring gammaretrovirus develop either progressive or regressive infection. Recent studies using analyses with enhanced sensitivity have correlated loads throughout FeLV with the clinical outcome, though remarkably, during the acute phase of infection, proviral and viral RNA burdens in the peripheral blood do not differ between groups. We hypothesized that viral loads in specific leukocyte subsets influence the infection outcome. Using a method established to determine the proviral and cell-associated viral RNA loads in specific leukocyte subsets, we evaluated viral loads in eleven FeLV-exposed specific pathogen-free (SPF) cats 2.5 years post-infection. Six cats had undergone regressive infection whereas five were persistently viremic. Aviremic cats had lower total proviral blood loads than the persistently infected cats and FeLV proviral DNA was shown to be integrated into genomic DNA in four out of four animals. Lymphocytes were predominantly infected vs. moncytes and granulocytes in aviremic cats. In contrast, persistently viremic cats were provirus-positive in all leukocyte subsets. The acute phase kinetics of FeLV infection were analyzed in two additional cats; an early lymphoreticular phase with productive infection in lymphocytes in both cats and in monocytes in one cat was followed by infection of the granulocytes; both cats became persistently infected. These results indicate that FeLV persistent viremia is associated with secondary viremia of bone marrow origin, whereas regressive cats only sustain a non-productive infection in low numbers of lymphocytes.  相似文献   

7.
Transmission of feline leukaemia virus in the milk of a non-viraemic cat   总被引：3，自引：0，他引：3  
The possibility of the transmission of feline leukaemia virus (FeLV) from latently infected cats was studied. Five female cats with latent infections were examined for evidence of transmission of the virus to their kittens. One of the cats infected members of four consecutive litters of kittens which subsequently became persistently viraemic and transmitted the virus to other susceptible kittens by contact. Shortly after birth its kittens were apparently FeLV-free since neither viral antigen nor infectious virus was detected in their blood and no virus was found in cell cultures made from aspirates of bone marrow. The kittens became viraemic from 45 days of age onwards at a time when their passively acquired colostral FeLV neutralising antibodies were no longer detectable. Transmission of the virus occurred via the milk since both FeLV antigen and infectious virus were found in milk samples taken six weeks after kittening and the virus was transmitted to a fostered kitten. Eleven weeks after the birth of the fourth litter the cat became viraemic. The intermittent presence of FeLV antigens detected by the Leukassay F test, but not infectious virus, in the plasma of this cat over the previous months and a low level of serum neutralising antibodies distinguished it from four other latently infected queens which did not transmit infection to their kittens. These factors may indicate a risk of milk transmission and reactivation of latent virus.  相似文献   

8.
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9.
Feline leukemia virus (FeLV) is an oncogenic retrovirus of cats. While higher viral RNA and proviral DNA loads have been correlated with progressive infections and disease, a similar correlation has been suggested for p27 antigen concentrations. This analytical study compared the results of a quantitative ELISA for p27 antigen with quantitative real-time PCR results for FeLV proviral DNA in patient samples. A significant positive correlation between copies of proviral DNA and the concentration of p27 antigen was identified (r = 0.761, P < 0.0001). Samples with high proviral DNA loads, at least 1 × 106 copies/mL of whole blood, typically had p27 antigen concentrations greater than 30 ng/mL in plasma. Samples with proviral DNA loads below this level all had concentrations of p27 antigen in plasma that were less than 10 ng/mL. Given this correlation, it is hypothesized that the concentration of p27 antigen at a given point in time may help to indicate the likelihood of a progressive or regressive infection similar to what has been demonstrated for proviral DNA loads.  相似文献   

10.
Two hundred and seventy-seven sick pet cats living in Italy were tested for antibodies to feline immunodeficiency virus (FIV) and for feline leukemia virus (FeLV) antigen. Overall, 24% of the cats resulted positive for anti-FIV antibody and 18% for FeLV antigen. FIV was isolated from the peripheral mononuclear blood cells of ten out of 15 seropositive cats examined and from one out of eight saliva samples. No FIV isolations were obtained from six serum samples cultured. Feline syncytium forming virus (FeSFV) could be isolated from blood and/or saliva in ten out of 11 FIV seropositive cats examined, in six out of nine FeLV antigen positive cats, in two cats found positive for both infection markers, and in three out of 11 cats negative for both markers. Thus, the probability of isolating FeSFV was enhanced by infection with other exogenous retroviruses.  相似文献   

11.
Feline leukemia virus is an oncogenic retrovirus that can result in a wide variety of neoplastic and non-neoplastic diseases, including immunosuppression. Diagnosis of FeLV infection can be achieved by several methods, including virus isolation; IFA assay of a peripheral blood smear; and detection of a viral protein (called p27) by ELISA testing of whole blood, plasma, serum, saliva, or tears. Commercially available ELISA kits have revolutionized FeLV testing and have become very popular as "in-house" procedures. This article discusses the interpretation of ELISA results and compares them with IFA assay findings. Feline immunodeficiency virus is a lentivirus that causes immunosuppression, but not neoplasia, in cats. It originally was called feline T-lymphotropic lentivirus. Differentiating FIV infection from the immunosuppressive type of FeLV infection requires virus isolation or serology. The most rapid method for diagnosis of FIV infection is ELISA testing for antiviral antibody.  相似文献   

12.
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13.
Feline leukemia is a useful model for malignant hematopoïetic tumor studies. It is caused by a type C, RNA virus, the Feline Leukemia virus (FeLV), transmitted horizontally, and widespread in the cat population.The presence of DNA sequences and virus specific RNA expression in cell cultures of SPF cats and cat embryos, indicates a vertical transmission may occur.These FeLV-related sequences in virus negative lymphosarcoma, almost from older cats, indicate that in certain FeLV related diseases the viral replication may not occur. An endogenous ecotropic feline virus may also explain this finding. The absence of FeLV gene expression in some lymphomatous cats—many older—suggest that, in these cats, spontaneous lymphoma may not be caused by FeLV.The widespread occurrence of feline xenotropic endogenous virus RD-114 gene, in feline lymphoma, suggest that expression of certain functions of this virus may be involved etiologically in the development of lymphoid tumors in the cat.Nevertheless, immunisation against FeLV would provide a good prevention against the main part of the feline lymphosarcomas and other FeLV-related diseases. Inactivated FeLV does not provide a good immunisation in young cats. By contrast a good protection against tumoral development is obtained by vaccination using the Feline oncogenic virus cell membrane antigen (FOCMA).  相似文献   

14.
Use of tears for diagnosis of feline leukemia virus infection   总被引：2，自引：0，他引：2  
A comparison was made of the use of serum, tears, and saliva for the detection of feline leukemia virus (FeLV) infection in cats. Cotton swabs were used to collect saliva, and tear-test strips were used to collect tears. Specimens were analyzed by a commercially available ELISA. Using a 10- to 15-minute specimen incubation period, FeLV was detected in 70% of the saliva specimens and in 73% of the tear specimens from viremic (serum-positive) cats. Feline leukemia virus antigen was not detected in saliva and tear specimens from serum-negative cats. The sensitivity of the tear assay was improved by increasing the incubation time to 24 hours. Tear strips could be air-dried and stored at room temperature for up to 7 days without any appreciable loss of activity. Client-owned and experimentally infected laboratory cats were tested for FeLV, using air-dried tear-test strips and a 24-hour incubation period. Tears were positive (contained FeLV antigen) in 65 of 72 (90%) serum-positive cats and did not contain antigen in 46 of 46 (100%) serum-negative cats. Results of ELISA obtained from serum and tears also were compared with results obtained from indirect fluorescent antibody testing of blood smears. Results of indirect fluorescent antibody and ELISA compared favorably with each other and with the results of tear testing.  相似文献   

15.
Feline leukemia virus is a naturally occurring, contagiously transmitted and oncogenic immunosuppressive retrovirus of cats. The effects of FeLV are paradoxical, causing cytoproliferative and cytosuppressive disease (eg, lymphoma and myeloproliferative disorders vs immunodeficiency and myelosuppressive disorders). In the first few weeks after virus exposure, interactions between FeLV and hemolymphatic system cells determine whether the virus or the cat will dominate in the host/virus relationship--persistent viremia and progressive infection or self limiting, regressive infection will develop. The outcome of these early host/virus interactions is revealed in the diagnostic assays for FeLV antigenemia and viremia. The latter, in turn, predict the outcome of FeLV infection in cats. Known host resistance factors include age and immune system functional status. Known virus virulence factors are magnitude of exposure and virus genotype. Molecular analysis of FeLV strains indicated that natural virus isolates exist as mixtures of closely related virus genotypes and that minor genetic variations among FeLV strains can impart major differences in pathogenicity. The genetic coding regions responsible for cell targeting and specific disease inducing capacity (eg, thymic lymphoma, acute immunosuppression, or aplastic anemia) have been mapped to the virus surface glycoprotein and/or long terminal repeat regions for several FeLV strains. Infection by specific FeLV strains leads to either malignant transformation or cytopathic deletion of specific lymphocyte and hemopoietic cell population, changes that prefigure the onset of clinical illness. Another notable feature of the biology of FeLV is that many cats are able to effectively contain and terminate viral replication, an important example of host immunologic control of a retrovirus infection and a process that can be selectively enhanced by vaccination. Thus, FeLV infection serves as a natural model of the multifaceted pathogenesis of retroviruses and as a paradigm for immunoprophylaxis against an immunosuppressive leukemogenic retrovirus.  相似文献   

16.
Feline leukaemia virus (FeLV) can be a challenging infection to diagnose due to a complex feline host-pathogen relationship and occasionally unreliable test results. This study compared the accuracy of three point-of-care (PoC) FeLV p27 antigen test kits commonly used in Australia and available commercially worldwide (SNAP FIV/FeLV Combo, Witness FeLV/FIV and Anigen Rapid FIV/FeLV), using detection of FeLV provirus by an in-house real-time polymerase chain reaction (qPCR) assay as the diagnostic gold standard. Blood (n = 563) and saliva (n = 419) specimens were collected from a population of cats determined to include 491 FeLV-uninfected and 72 FeLV-infected individuals (45 progressive infections [p27 and qPCR positive], 27 regressive infections [p27 negative, qPCR positive]). Sensitivity and specificity using whole blood was 63% and 94% for SNAP Combo, 57% and 98% for Witness, and 57% and 98% for Anigen Rapid, respectively. SNAP Combo had a significantly lower specificity using blood compared to the other two kits (P = 0.004 compared to Witness, P = 0.007 compared to Anigen Rapid). False-positive test results occurred with all three kits using blood, and although using any two kits in parallel increased specificity, no combination of kits completely eliminated the occurrence of false-positive results. We therefore recommend FeLV proviral PCR testing for any cat that tests positive with a PoC FeLV antigen kit, as well as for any cat that has been potentially exposed to FeLV but tests negative with a FeLV antigen kit, before final assignment of FeLV status can be made with confidence. For saliva testing, sensitivity and specificity was 54% and 100%, respectively, for all three test kits. The reduced sensitivity of saliva testing compared to blood testing, although not statistically significant, suggests saliva testing with the current generation of PoC FeLV antigen kits is unsuitable for screening large populations of cats, such as in shelters.  相似文献   

17.
The safety and the efficacy of several feline leukemia virus (FeLV) vaccines for 16-week-old kittens were determined. Vaccines were derived from an FL74 lymphoblastoid cell line that has been in continuous tissue culture passage for about 4 years. The vaccines were made from living virus, formaldehyde-inactivated whole FL74 cells, and formaldehyde-inactivated whole virus. The efficacy of each produced vaccine was determined by challenge exposure of vaccinated cats with virulent FeLV. The two formaldehyde-inactivated vaccines were found to be safe for use in kittens. Neither vaccine produce a significant feline oncornavirus-associated cell membrane antigen or virus-neutralizing antibody response, nor did they prevent infection with virulent FeLV. The inactivated whole-virus vaccine, however, did substantially decrease the proportion of kittens infected with virulent FeLV that became persistently viremic. In contrast, the whole FL74 cell vaccine did not reduce the number of infected kittens that became persistently viremic. The live-virus vaccine was found to be both safe and efficacious. About a half of the kittens vaccinated with live virus had transient bone marrow infection that lasted from 2 to 4 weeks. Viral antigen was not detected in peripheral blood, and infective virus was not shed in saliva, urine, or feces during the period that the vaccinal virus could be recovered from the bone marrow. In addition, there was no horizontal spread of vaccinal virus from vaccinated to non-vaccinated cagemates. Within several weeks, vaccinated kittens demonstrated no clinical or hematologic abnormalities and had high serum levels of feline oncornavirus-associated cell membrane antigen and virus-neutralizing antibody. Kittens vaccinated with living FeLV were resistant to infection with virulent virus.  相似文献   

18.
Bone marrow fibroblast colony-forming units (CFU-F) were evaluated in cats experimentally infected with feline leukemia virus (FeLV). Cats that developed persistent viral infection and anemia (progressor cats) had a progressive decrease in the number of CFU-F at 2, 4, 6, 8, and 10 weeks after inoculation with FeLV. This suppression of CFU-F number in progressor cats ranged from 16 to 44% of the preinoculation CFU-F value. Cats that did not develop persistent viral infection or anemia (regressor cats) had decreased numbers of CFU-F (24% of the preinoculation CFU-F value) at 2 weeks after inoculation, but normal CFU-F numbers at 4, 6, 8, and 10 weeks after inoculation. In vitro incubation of bone marrow mononuclear cells from healthy cats with the 15,000-dalton envelope protein of FeLV resulted in decreased number of CFU-F (21% of that of untreated cultures). The number of CFU-F from bone marrow mononuclear cells incubated with the 27,000-dalton core protein of FeLV was similar to that from untreated cultures.  相似文献   

19.
More than 2000 cats sent for necropsy in order to provide a diagnosis were investigated immunohistologically using paraffin sections for the presence of a persistent infection with feline leukemia virus (FeLV). The spectrum of neoplastic and non-neoplastic diseases associated significantly with FeLV infection was determined statistically. Three-quarters of the cats with persistent FeLV infections died of non-neoplastic diseases and about 23% died of tumors, nearly exclusively those of the leukemia/lymphoma disease complex. A strong association with liver degeneration, icterus and a FeLV-associated enteritis was found in addition to the known association with non-neoplastic diseases and conditions such as anemia, bacterial secondary infections and respiratory tract inflammations due to the immunosuppressive effect of FeLV, hemorrhages and feline infectious peritonitis. Surprisingly, diseases and conditions like feline infectious panleukopenia, enteritis (of other types than FeLV-associated enteritis and feline infectious panleukopenia), glomerulonephritis, uremia and hemorrhagic cystitis were not associated with persistent FeLV infection. Another unexpected finding was that most pathogenic infectious agents demonstrated in the cats were not FeLV-associated either. Thus, immunosuppression due to FeLV infection seems to make the animals susceptible to certain pathogenic infectious agents, but not to the majority.  相似文献   

20.
The performance of a micro ELISA test for detection of feline leukemia virus (FeLV) infection was evaluated. The test was found specific for FeLV and feline sarcoma virus (FeSV) group-specific antigens in blood, plasma or serum of infected cats. Other common feline pathogens were negative to the test.Quantities as little as 7.8 ng of p-27 (the major group specific antigen of FeLV) per ml of sample gave positive results. The correlation between the micro ELISA test and the indirect immunofluorescent test commonly used for diagnosis of FeLV infection was 98% in 116 clinical cases and 184 samples from cats inoculated with FeLV and 100% in 100 specific pathogen-free cats.  相似文献   

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