Prevalence and risk factors for cats testing positive for feline immunodeficiency virus and feline leukaemia virus infection in cats entering an animal shelter in New Zealand

Abstract

AIMS

To estimate the prevalence of cats testing positive for antibodies to feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) antigens in domestic cats entering a New Zealand animal shelter, based on a commercial point-of-care ELISA, to identify risk factors associated with cats testing positive, and to compare the results obtained from the ELISA with those obtained using PCR-based testing.     

Diagnosing feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) infection: an update for clinicians

With the commercial release in Australia in 2004 of a vaccine against feline immunodeficiency virus (FIV; Fel‐O‐Vax FIV®), the landscape for FIV diagnostics shifted substantially. Point‐of‐care (PoC) antibody detection kits, which had been the mainstay for diagnosing FIV infection since the early 1990s, were no longer considered accurate to use in FIV‐vaccinated cats, because of the production of vaccine‐induced antibodies that were considered indistinguishable from those produced in natural FIV infections. Consequently, attention shifted to alternative diagnostic methods such as nucleic acid detection. However, over the past 5 years we have published a series of studies emphasising that FIV PoC test kits vary in their methodology, resulting in differing accuracy in FIV‐vaccinated cats. Importantly, we demonstrated that two commercially available FIV antibody test kits (Witness? and Anigen Rapid?) were able to accurately distinguish between FIV‐vaccinated and FIV‐infected cats, concluding that testing with either kit offers an alternative to PCR testing. This review summarises pertinent findings from our work published in a variety of peer‐reviewed research journals to inform veterinarians (particularly veterinarians in Australia, New Zealand and Japan, where the FIV vaccine is currently commercially available) about how the approach to the diagnosis of FIV infection has shifted. Included in this review is our work investigating the performance of three commercially available FIV PoC test kits in FIV‐vaccinated cats and our recommendations for the diagnosis of FIV infection; the effect of primary FIV vaccination (three FIV vaccines, 4 weeks apart) on PoC test kit performance; our recommendations regarding annual testing of FIV‐vaccinated cats to detect ‘vaccine breakthroughs’; and the potential off‐label use of saliva for the diagnosis of FIV infection using some FIV PoC test kits. We also investigated the accuracy of the same three brands of test kits for feline leukaemia virus (FeLV) diagnosis, using both blood and saliva as diagnostic specimens. Based on these results, we discuss our recommendations for confirmatory testing when veterinarians are presented with a positive FeLV PoC test kit result. Finally, we conclude with our results from the largest and most recent FIV and FeLV seroprevalence study conducted in Australia to date.     

Feline immunodeficiency virus status of Australian cats with lymphosarcoma

OBJECTIVE: To determine the FIV status of Australian cats with lymphosarcoma and relate this to patient characteristics, tumour characteristics (tissue involvement, histological grade and immunophenotype), haematological and serum biochemical values and FeLV status of affected cats. DESIGN: Prospective study of 101 client-owned cats with naturally-occurring lymphosarcoma. PROCEDURE: Western blot analysis, ELISA and immunochromatography were used to detect FIV antibodies in serum from cats with lymphosarcoma. RESULTS: On the basis of Western blot analysis (which was considered the most accurate method for determining FIV status), 50/101 (50%) of cats with naturally-occurring lymphosarcoma were positive for FIV antibodies. Of these 50 cats, 35 had tumours of B-cell phenotype, 13 had T-cell tumours and 2 had tumours classified as non-B/non-T. Tumours from eight of these FIV-positive cats contained FeLV gene sequences, including a 9-month-old cat with FeLV antigenaemia. Compared with FlV-negative cats with lymphosarcoma, FIV-positive cats were more likely to be domestic crossbreds (P = 0.004), male (P = 0.048) and have atypical (especially nasal) forms of lymphosarcoma (P = 0.09). Only 39 of 107 (36%) blood or sera tested using ELISA were positive for FIV antibodies (including 5 false-positives). CONCLUSIONS: The prevalence of FIV infection was considerably higher in our cohort of cats compared with series of lymphosarcoma cases from the Northern hemisphere. A positive FIV status was strongly associated with lymphosarcoma in Australian cats and it is possible that this infection may predispose to the development of lymphoid neoplasia. The presence of FIV infection would have been underestimated if commercial kits alone had been used for serology.     

Feline leukaemia virus status of Australian cats with lymphosarcoma

OBJECTIVE: To determine the FeLV status of sera and tumours from Australian cats with lymphosarcoma in relation to patient characteristics, tumour characteristics (tissue involvement, histological grade and immunophenotype), haematological and biochemical values. DESIGN: Prospective study of 107 client-owned cats with naturally-occurring lymphosarcoma. PROCEDURE: An ELISA was used to detect FeLV p27 antigen in serum specimens collected from cats with lymphosarcoma. A PCR was used to detect FeLV DNA in formalin-fixed, paraffin-embedded tissue sections containing neoplastic lymphoid cells. The PCR was designed to amplify a highly conserved region of the untranslated long terminal repeat of FeLV provirus. RESULTS: Only 2 of 107 cats (2%), for which serum samples were available, were FeLV-positive on the basis of detectable p27 antigen in serum. In contrast, 25 of 97 tumours (26%) contained FeLV DNA. Of the 86 cats for which both PCR and ELISA data were available, 19(22%) had FeLV provirus in their tumours but no detectable circulating FeLV antigen in serum, while 2 (2%) had FeLV provirus and circulating FeLV antigen. FeLV PCR-positive/ELISA-negative cats (19) differed from PCR-negative/ELISA-negative cats (65) in having fewer B-cell tumours (P = 0.06), more non B-/non T-cell tumours (P = 0.02) and comprising fewer non-Siamese/Oriental pure-bred cats (P = 0.03). CONCLUSIONS: The prevalence of FeLV antigen or provirus was considerably lower in our cohort of cats compared with studies of lymphosarcoma conducted in the Northern hemisphere. This suggests that factors other than FeLV are important in the development of lymphosarcoma in many Australian cats. No firm conclusions could be drawn concerning whether FeLV provirus contributed to the development of lymphosarcoma in PCR-positive/ELISA-negative cats.     

Serological differentiation of FIV-infected cats from dual-subtype feline immunodeficiency virus vaccine (Fel-O-Vax FIV) inoculated cats

Feline immunodeficiency virus (FIV) vaccine, Fel-O-Vax FIV, was released for sale in the US in 2002. The antibodies of vaccinated cats interfere with serological assays by currently available FIV diagnostic kits. In this study, we investigated whether it is possible to distinguish serologically cats vaccinated with Fel-O-Vax FIV from cats experimentally or naturally infected with FIV. A total of 153 sera taken from 97 cats were used as serum samples. Enzyme linked immunosorbent assay (ELISA) was performed using whole FIV antigen and formalin treated whole FIV antigen, recombinant-gag (r-gag) antigen, and transmembrane (TM) peptide. Statistical analysis was performed using ELISA optical density (O.D.) values obtained with each antigen as variables. Except for the ELISA O.D. values obtained with r-gag antigen, a significant difference in ELISA O.D. values was observed between the vaccinated and the infected groups. However, it was not possible to distinguish both groups unequivocally. Using discriminant analysis, it was possible to distinguish the two groups with an accuracy of 97.1% with two discriminating variables (ELISA O.D. values obtained with formalin treated whole FIV antigen, and TM peptide), 97.8% with three discriminating variables (ELISA O.D. values obtained with whole FIV antigen, formalin treated whole FIV antigen, and TM peptide). Therefore, it was considered possible to distinguish cats vaccinated with Fel-O-Vax FIV from FIV-infected cats by ELISA using two types of antigens including formalin treated whole FIV antigen and TM peptide, or three types of antigens including formalin treated whole FIV antigen, TM peptide and whole FIV antigen.     

Characterisation of lymphosarcomas in Australian cats using polymerase chain reaction and immunohistochemical examination

Objective To examine tumour tissue of cats with lymphosarcoma for the presence of feline leukaemia virus and feline immunodeficiency virus and analyse the immunophenotype of the tumours.
Design A retrospective study of feline lymphosarcoma cases.
Methods Formalin-fixed, paraffin-embedded tumour tissue of 14 feline lymphosarcomas was examined for the presence of feline leukaemia virus and feline immunodeficiency virus by polymerase chain reaction and immunohistochemistry. Using polyclonal and monoclonal antibodies against T and B lymphocytes, the phenotypic expression of the tumours was characterised.
Results No feline leukaemia virus antigen or proviral sequences were detected. Feline immunodeficiency virus proviral sequences were detected in two cases by polymerase chain reaction. Immunophenotyping of all 14 cases resulted in seven cases being classified as B-cell phenotype, four as T-cell phenotype, and the remaining three undetermined.
Conclusions In contrast to previous reports overseas, our results suggest that feline leukaemia virus infection appears to be an infrequent cause of lymphosarcoma in the cats that were necropsied. Feline immunodeficiency virus may have a role in lymphomagenesis. The potential role of feline immunodeficiency virus needs to be explored in more depth. Compared with most previous reports, B-cell tumours were more common than T-cell tumours in this series of cats.     

Vaccine protection against feline immunodeficiency virus: setting the challenge

Since feline immunodeficiency virus (FIV) was first isolated, international research efforts have been directed towards developing a protective vaccine, not least because it may provide a model for a candidate human immunodeficiency virus (HIV) vaccine. This article reviews the challenges facing vaccine development, the current state of knowledge and future prospects for FIV vaccination.     

Molecular subtyping of feline immunodeficiency virus from cats in Melbourne

OBJECTIVE: To determine the subtypes of feline immunodeficiency virus (FIV) present in the domestic cat population in Melbourne. METHODS: Blood samples were collected from 42 cats that had serum antibodies against FIV. DNA was extracted and subjected to polymerase chain reaction (PCR) to amplify variable regions of the envelope (env) and group specific antigen (gag) genes of FIV. PCR products were directly sequenced or sequenced after cloning when direct sequencing yielded ambiguous results. Phylogenetic analysis was performed and comparisons made with representative sequences of different subtypes. RESULTS: The variable region of the env gene was successfully amplified by PCR from 41 of the 42 cats. All 41 were found to cluster with subtype A env sequences. The variable region of the gag gene was successfully amplified by PCR from all 42 cats. Forty-one were found to cluster with subtype A gag genes and one was found to cluster with subtype B sequences, suggesting that it may be derived from a recombinant env A/gag B virus. CONCLUSIONS: Subtype A is the predominant FIV type in Melbourne, although a subtype A/B recombinant was identified in the population of FIV positive cats. These results of env gene analysis were similar to those in a previous Australian study, suggesting that subtype A predominates in Australia. The results of the gag gene analysis show the importance of analysing multiple areas of the FIV genome when assigning FIV subtypes. Comparison with other major urban centres may provide useful information about the phylogenic diversity of FIV in Australia.     

Therapeutic effects of recombinant feline interferon-omega on feline leukemia virus (FeLV)-infected and FeLV/feline immunodeficiency virus (FIV)-coinfected symptomatic cats

The clinical efficacy of a recombinant feline interferon, rFeIFN-omega, was evaluated for the treatment of cats presented with clinical signs associated with feline leukemia virus (FeLV) infection and FeLV/feline immunodeficiency virus (FIV) coinfection in the field. In this multicentric, double-blind, placebo-controlled trial, 81 cats meeting the inclusion criteria were randomly placed into 2 groups and treated subcutaneously with rFelFN-omega (1 million [M]U/kg per day) or placebo once daily for 5 consecutive days in 3 series (day 0, 14, 60). The cats were monitored for up to 1 year for clinical signs and mortality. During the initial 4-month period, interferon (IFN)-treated cats (n = 39) had significantly reduced clinical scores compared with placebo (n = 42), with all cats having received concomitant supportive therapies. Compared with the control, the IFN-treated group showed significantly lower rates of mortality: 39% versus 59% (1.7-fold higher risk of death for controls) at the 9-month time point and 47% versus 59% (1.4-fold higher risk of death for controls) at the 12-month time point. The IFN treatment was associated with minor but consistent improvement in abnormal hematologic parameters (red blood cell count, packed cell volume, and white blood cell count), apparently underlying the positive effects of IFN on clinical parameters. These data demonstrate that rFeIFN-omega initially has statistically significant therapeutic effects on clinical signs and later on survival of cats with clinical signs associated with FeLV infection and FeLV/FIV coinfection.     

Diagnosing feline immunodeficiency virus (FIV) infection in FIV-vaccinated and FIV-unvaccinated cats using saliva

We recently showed that two immunochromatography point-of-care FIV antibody test kits (Witness FeLV/FIV and Anigen Rapid FIV/FeLV) were able to correctly assign FIV infection status, irrespective of FIV vaccination history, using whole blood as the diagnostic specimen. A third FIV antibody test kit, SNAP FIV/FeLV Combo (an enzyme-linked immunosorbent assay [ELISA]), was unable to differentiate antibodies produced in response to FIV vaccination from those incited by FIV infection. The aim of this study was to determine if saliva is a suitable diagnostic specimen using the same well characterized feline cohort. FIV infection status of these cats had been determined previously using a combination of serology, polymerase chain reaction (PCR) testing and virus isolation. This final assignment was then compared to results obtained using saliva as the diagnostic specimen utilizing the same three point-of-care FIV antibody test kits and commercially available PCR assay (FIV RealPCR). In a population of cats where one third (117/356; 33%) were FIV-vaccinated, both immunochromatography test kits accurately diagnosed FIV infection using saliva via a centrifugation method, irrespective of FIV vaccination history. For FIV diagnosis using saliva, the specificity of Anigen Rapid FIV/FeLV and Witness FeLV/FIV was 100%, while the sensitivity of these kits was 96% and 92% respectively. SNAP FIV/FeLV Combo had a specificity of 98% and sensitivity of 44%, while FIV RealPCR testing had a specificity of 100% and sensitivity of 72% using saliva. A revised direct method of saliva testing was trialed on a subset of FIV-infected cats (n = 14), resulting in 14, 7 and 0 FIV positive results using Anigen Rapid FIV/FeLV, Witness FeLV/FIV and SNAP FIV/FeLV Combo, respectively. These results demonstrate that saliva can be used to diagnose FIV infection, irrespective of FIV vaccination history, using either a centrifugation method (Anigen Rapid FIV/FeLV and Witness FeLV/FIV) or a direct method (Anigen Rapid FIV/FeLV). Collection of a saliva specimen therefore provides an acceptable alternative to venipuncture (i) in fractious cats where saliva may be easier to obtain than whole blood, (ii) in settings when a veterinarian or trained technician is unavailable to collect blood and (iii) in shelters where FIV testing is undertaken prior to adoption but additional blood testing is not required.     

Combination chemotherapy in feline lymphoma: treatment outcome, tolerability, and duration in 23 cats

BACKGROUND: Different chemotherapy regimes have been described for feline lymphoma with varying outcomes. HYPOTHESIS: In cats with lymphoma, a long-term, multiagent chemotherapy protocol will be effective and carry acceptable toxicity. ANIMALS: Twenty-three cats with histologically or cytologically confirmed diagnosis of lymphoma. METHODS: Prospective, single-arm clinical trial in which cats were treated with a chemotherapy protocol consisting of a cyclic combination of l-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate, and prednisolone with a planned total treatment time of 122 weeks. RESULTS: Complete remission (CR) rate was 74% (n = 17). Fourteen percent of cats attained partial remission (PR). Median duration of first CR was 264 days (range, 45-2,485 days). Six-month, 1-, and 2-5-year remission rates were 75, 50, and 34%, respectively. Duration of PR ranged between 23 and 63 days. Median survival in cats with CR was 296 days (range, 50-2,520 days). Six-month, 1-, 2-, and 3-5-year survival rates in cats with CR were 82, 47, 34, and 27%, respectively. Survival of cats achieving PR ranged between 38 and 120 days. Of the analyzed variables, only anatomical location had a significant influence on remission duration (P=.022). Actual median treatment time in cats with CR was 128 days (18 weeks). Hematologic and gastrointestinal toxicosis was infrequent and mostly low grade. CONCLUSIONS AND CLINICAL IMPORTANCE: In this population of cats with lymphoma, chemotherapy was effective. With infrequent and mostly low-grade toxicosis, tolerability of the protocol may be considered good.     

Evaluation of barcoded magnetic bead–based immunoassays for the simultaneous detection of feline leukemia virus antigen and antibody against feline immunodeficiency virus

Testing platforms that leverage automation, require minimal sample volume, and enable various tests to be performed simultaneously on a single sample have the potential to improve workflow and efficiency in veterinary diagnostic laboratories. We evaluated a barcoded magnetic bead (BMB) technology using established immunoassays for detection of feline leukemia virus (FeLV) p27 antigen and antibody against feline immunodeficiency virus (FIV). Analytical sensitivity, limit of blank, and limit of detection were used to establish a functional sensitivity of 1.00 ng/mL of inactivated FeLV antigen and 35.7 ng/mL of anti-FIV monoclonal antibody. Common interferents, such as hemoglobin, lipid, and bilirubin, were not found to interfere with the performance of the assay. Intra- and inter-assay CVs were <13% for both assays using manufactured samples. Using a set of 116 feline samples, the diagnostic accuracy of our multiplex assay was 100% compared to reference assays. Performance in a convenience set of 1,000 feline samples submitted to a commercial diagnostic laboratory revealed a proportion of positive results of 1.3% for FeLV and 3.7% for FIV. BMB technology should enable rapid screening of samples for various markers in a single immunoassay well.     

Therapy for Australian cats with lymphosarcoma

OBJECTIVE: To determine the response of Australian cats with lymphosarcoma to chemotherapy and/or surgery in relation to patient and tumour characteristics, haematological and serum biochemical values and retroviral status. DESIGN: Prospective study of 61 client-owned cats with naturally-occurring lymphosarcoma subjected to multi-agent chemotherapy and/or surgery. PROCEDURE: An accepted chemotherapy protocol utilising l-asparaginase, vincristine, cyclophosphamide, doxorubicin, methotrexate and prednisolone was modified and used to treat 60 cats with lymphosarcoma. Clinical findings were recorded before and during therapy. As far as practical, cases were followed to death, euthanasia or apparent cure. Owner satisfaction with the results of chemotherapy was determined using a questionnaire sent after the completion of chemotherapy. RESULTS: One cat, with lymphosarcoma limited to a single mandibular lymph node, was treated using surgery alone and was cured. The other 60 cats were treated using multi-agent chemotherapy, although seven cats with localised intestinal, ocular and subcutaneous lesions had these lesions partially (2 intestinal lesions) or completely (2 eyes, 2 intestinal lesions and a cluster of regional lymph nodes) resected prior to starting chemotherapy. The median survival time for these 60 cats was 116 days. Of the 60 cats, 48 rapidly went into complete remission following the administration of 1-asparaginase, vincristine and prednisolone (complete remission rate 80%) and these cats had a median survival of 187 days. Three cats were censored from further analysis as their long-term survival data were uninterpretable because they died of causes unrelated to lymphosarcoma or were prematurely lost to follow-up. Twenty cats were classed as 'long-term survivors' based on survival time in excess of one year and at least 14 were 'cured' based on the absence of physical evidence of lymphosarcoma 2-years after initiating treatment. In other words, of the 48 cats that reached complete remission, in excess of 29% were 'cured'. Despite detailed analysis, few meaningful prognostic indicators based on patient or tumour characteristics were identified, although long-term survivors were more likely to be less than 4-years (P= 0.04) and to have tumours of the T-cell phenotype (P= 0.06). Excluding the one FeLV ELISA-positive cat with mediastinal LSA, 7 of 9 cats less than 4 years-of-age were long-term survivors (median survival time >1271 days). There was a strong association between achieving complete remission and long-term survival (P = 0.003). On the basis of 27 replies to a questionnaire, owners were generally very satisfied with the response to chemotherapy, irrespective of the survival time of the individual patient. Eighty five percent of owners expressed complete satisfaction with their decision to pursue chemotherapy and 70% believed their cat's health status improved during the first 2-weeks of treatment. Importantly, 78% of owners considered that chemotherapy required a very substantial time commitment on their part. CONCLUSIONS: It was possible to cure approximately one quarter of cats with lymphosarcoma using sequential multi-agent chemotherapy and/or surgery. FeLV-negative cats younger than 4 years (typically with mediastinal lymphosarcoma) had a particularly favourable prognosis. The decision to embark on chemotherapy should be based on the results of induction chemotherapy with l-asparaginase, vincristine and prednisolone, as the response to this was a good predictor of long-term survival. Cats surviving the first 16 weeks of chemotherapy generally enjoyed robust remissions (in excess of 1 year) or were cured of their malignancy.     

Deep and superficial skin scrapings from a feline immunodeficiency virus-positive cat

An 8-year-old, neutered male, domestic shorthair cat housed at the North Carolina State University, College of Veterinary Medicine, Laboratory Animal Research facility as part of a research colony was examined because of mulifocal skin lesions. The lesions consisted of patchy alopecia with mild crusting of the periauricular region, neck, and dorsum; periauricular excoriations; marked dorsal seborrhea and scaling; and generalized erythematous papules. A moderate amount of ceruminous exudate was present in both ear canals. Results of testing for feline immunodeficiency virus (FIV) were positive. An ear swab specimen and superficial and deep skin scrapings were obtained, mounted with oil on glass slides, and coverslipped for microscopic examination. Two populations of mites were observed: a large population of slender, long (approximately 200 microm), adult mites with long, tapering abdomens that comprised two-thirds of the total body length; and a smaller population of more translucent and shorter mites (approximately 100 microm) with wide, blunt abdomens that had prominent transverse ridges. The interpretation was demodicosis, with Demodex cati and D gatoi co-infection. Histologic sections of biopsies from skin lesions on the neck, dorsum, and periauricular area contained a mild perivascular and perifollicular inflammatory infiltrate composed predominantly of histiocytes, lymphocytes, and plasma cells. Diffusely within the follicular lumina and occasionally within the superficial keratin, a myriad of Demodex organisms were observed. Intrafollicular mites were compatible in appearance with D cati whereas those in the corneal layer were suggestive of D gatoi. Demodicosis is an uncommon disease of cats, and rare cases of dual infection have been documented, occasionally in FIV-infected cats. The dual infection emphasizes the importance of doing both superficial and deep skin scrapings and of recognizing the unique microscopic features of different Demodex mites.     

In vivo CXCR4 expression, lymphoid cell phenotype, and feline immunodeficiency virus infection

Primary isolates of feline immunodeficiency virus (FIV) appear to require binding to CD134 in conjunction with CXCR4(X4) to infect IL-2-dependent T-cell-derived cells in culture. However, much less is known about the role of X4 for the infection of cells in vivo. To investigate the correlation between X4 expression and FIV infection in cats acutely infected with FIV-C-Pgmr we used high-speed fluorescence-activated cell sorting and realtime PCR to co-analyze cell phenotypes from lymph node, thymus, bone marrow and blood for FIV infection and X4 expression. X4 expression was greatest in lymph node, both in frequency and in mean fluorescence intensity. The thymus demonstrated a higher proviral burden in X4+ thymic T cells (14% in X4+ thymic T cells and 7% in X4− cells) whereas, proviral loads were similar between X4+ and X4− cell populations in all other tissues examined. Assuming a minimum of one proviral copy per cell, a maximum of 50% of FIV-positive cells were X4+. The highest fraction of FIV-infected X4− cells was present in bone marrow. Regardless of X4 status, proviral loads were higher in lymph node and blood T cells than in B cells. These studies provide both a positive association between X4 expression and FIV infection and introduce the probability that X4-independent infection occurs in other target cells in vivo.     

猫免疫缺陷病毒在医学中的应用

猫免疫缺陷病毒(Feline immunodeficiency virus,FIV)是一种主要感染猫的反转录病毒.FIV与人的免疫缺陷病毒(Human immunodeficiency virus,HIV)有许多相似性,可作为HIV的研究模型,如测量FIV病毒在动物体内的感染曲线,可为了解HIV在人体内的传播细节提供蓝图;利用FIV偏好感染发展中的神经系,可以帮助人们了解艾滋病(Acquired immure deficiency syndrome,AIDS)对神经系统的致病机理.FIV疫苗的研究获得成功,可为HIV疫苗的研制提供提示.FIV在基因治疗方面有重要的应用价值,目前应用FIV传递CFTR(cystic fibrosis transmembrane conductance regulator)的cDNA到呼吸系统表皮细胞治疗囊肿性纤维化(cystic fibrosis,CF)的研究已经取得了很大进展.     

猫免疫缺陷病毒在医学中的应用

猫免疫缺陷病毒（Feline immunodeficiency virus，FIV）是一种主要感染猫的反转录病毒。FIV与人的免疫缺陷病毒（Human immunodeficiency virus，HIV）有许多相似性，可作为HIV的研究模型，如测量FIV病毒在动物体内的感染曲线，可为了解HIV在人体内的传播细节提供蓝图；利用FIV偏好感染发展中的神经系，可以帮助人们了解艾滋病（Acquired immure deficiency syndrome，AIDS）对神经系统的致病机理。FIV疫苗的研究获得成功，可为HIV疫苗的研制提供提示。FIV在基因治疗方面有重要的应用价值，目前应用FIV传递CFTR（cystic fibrosis transmembrane conductance regulator）的cDNA到呼吸系统表皮细胞治疗囊肿性纤维化（cysticfibrosis，CF）的研究已经取得了很大进展。     

The kinetics of feline leukaemia virus shedding in experimentally infected cats are associated with infection outcome

Feline leukaemia virus (FeLV) infection in felids results mainly from oronasal exposure to infectious saliva and nasal secretions, but the potential for viral transmission through faeces and urine has not been completely characterized. In order to assess and compare potential FeLV transmission routes, we determined the viral kinetics in plasma, saliva, faeces and urine during early experimental FeLV infection (up to week 15 post-exposure) in specific pathogen-free cats. In addition to monitoring p27 antigen levels measured by ELISA, we evaluated the presence of infectious particles by cell culture assays and quantified viral RNA loads by a quantitative real-time TaqMan polymerase chain reaction. RNA load was associated with infection outcome (high load-progressive infection; low load-regressive infection) not only in plasma, but also in saliva, faeces and urine. Infectious virus was isolated from the saliva, faeces and urine of infected cats with progressive infection as early as 3-6 weeks post-infection, but usually not in cats with regressive infection. In cats with progressive infection, therefore, not only saliva but also faeces and to some extent urine might represent potential FeLV transmission routes. These results should be taken into account when modelling FeLV-host interactions and assessing FeLV transmission risk. Moreover, during early FeLV infection, detection of viral RNA in saliva may be used as an indicator of recent virus exposure, even in cats without detectable antigenaemia/viraemia. To determine the clinically relevant outcome of FeLV infection in exposed cats, however, p27 antigen levels in the peripheral blood should be measured.