Histologic classification and immunophenotype of lymphosarcomas in cats with naturally and experimentally acquired feline immunodeficiency virus infections

Characterization of platelet rich plasma in feline immunodeficiency virus-infected cats: Cell, and PDGF-BB and TGF-ß1 growth factor analysis

Autologous platelet-rich plasma (PRP) contains growth factors (GFs) that modulate the expression of inflammatory cells; thus, these products could be considered a good strategy to favor tissue regeneration in feline immunodeficiency (FIV) positive cats. However, there is no scientific documentation on obtaining PRP in FIV-positive cats. Authors hypothesized that PRP can be obtained in FIV cats following the PRGF®-Endoret® methodology. The objectives of this study were to compare the platelet, erythrocyte, and leukocyte concentration between whole blood (WB) and the PRP; and determine the concentration of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor β1 (TGF-β1) in FIV-positive cats. Sixteen adults FIV-positive asymptomatic cats were included in the study. WB samples were drawn and the PRP was obtained by centrifugation at 265g for 10 min. Erythrocyte and leukocyte, platelets, and mean platelet volume (MPV) were determined both in WB and in PRP. PDGF-BB and TGF-β1 concentrations were additionally determined in PRP. Platelet concentration increased 1.1 times in PRP fraction compared to WB, but no significant differences were reported. MPV was statistically higher in WB than in PRP (p = 0.001). Erythrocytes and leukocytes counts were decreased by 99% and 92%, respectively in the PRP fraction (p < 0.001). Regarding TGF-ß1, a higher concentration was shown in the PRP (p < 0.02). Although the product obtained could not be classified as PRP according to the PRGF®-Endoret® methodology, based on the drastic reduction of RBC and WBC, the PLT concentrate is of high purity.

Feline Lymphoma: Patient Characteristics and Response Outcome of the COP-Protocol in Cats with Malignant Lymphoma in The Netherlands

Feline lymphoma is currently less commonly associated with retrovirus infections as the feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV). This is thought to have caused a shift in the distribution of anatomical subtypes and eventually have led to poorer treatment outcomes. The aim of this study was to evaluate whether this change was also notable in the Netherlands, a country historically known for its low prevalence of FeLV and FIV, and to determine its consequences on treatment response. A 10-year cohort of 174 cats with large cell lymphoma (110 treated) were included and compared to historical data from previously published reports in the Netherlands. Of the 90 cats screened, only one tested positive for FeLV and three for FIV. The most current cohort had an increased age (median 8.7 years) and fever Siamese cats (6.3%) compared to previous reports, with alimentary (24.5%) and nasopharyngeal lymphoma (22.7%) being the most common subtypes. Sixty-six of the one hundred and ten cats (60%) went into complete remission, (CR) resulting in a median disease-free period (DFP) of 763 days, with nasopharyngeal and mediastinal having the longest DFP. The median overall survival time was 274 days with an estimated 1-year survival of 41.3% and a 2-year survival of 34.6%, respectively. Patient characteristics of cats with malignant lymphoma in the Netherlands have changed over the years, but this cannot be explained by differences in FeLV/FIV prevalence. Although the overall response rate to therapy did not change over time, for some lymphoma subtypes, longer DFPs were observed compared to 30 years ago.

Exploring the link between viruses and cancer in companion animals: a comprehensive and comparative analysis

Currently, it is estimated that 15% of human neoplasms globally are caused by infectious agents, with new evidence emerging continuously. Multiple agents have been implicated in various forms of neoplasia, with viruses as the most frequent. In recent years, investigation on viral mechanisms underlying tumoral transformation in cancer development and progression are in the spotlight, both in human and veterinary oncology. Oncogenic viruses in veterinary medicine are of primary importance not only as original pathogens of pets, but also in the view of pets as models of human malignancies. Hence, this work will provide an overview of the main oncogenic viruses of companion animals, with brief notes of comparative medicine.

Neuropathology of Central and Peripheral Nervous System Lymphoma in Dogs and Cats: A Study of 92 Cases and Review of the Literature

The literature about nervous system lymphoma (NSL) in dogs and cats is fragmentary, based on a few case series and case reports with heterogeneous results. The aim of our study was to retrospectively analyze 45 cases of canine and 47 cases of feline NSL and compare our results with previously reported data, also providing an extensive literature review. Breed, age, gender, clinical signs, type, and neurolocalization were recorded for each case. The pathological patterns and phenotype were assessed by histopathology and immunohistochemistry. The occurrence of central and peripheral NSL was similar between the two species in both primary and secondary types. NSL occurred with a slightly higher prevalence in Labrador Retrievers, and spinal cord lymphoma (SCL) was associated with young age in cats. The most frequent locations were the forebrain in dogs and the thoracolumbar segment in cats. Primary central nervous system lymphoma (CNSL) in cats most frequently involved the forebrain meninges, particularly as a B-cell phenotype. Peripheral NSL mostly affected the sciatic nerve in dogs and had no preferred location in cats. Nine different pathological patterns were identified, with extradural as the most prevalent SCL pattern in both species. Finally, lymphomatosis cerebri was described for the first time in a dog.

A review of primary central nervous system neoplasms of cats

Primary central nervous system (CNS) neoplasms are uncommonly diagnosed in cats. The majority of primary feline CNS neoplasms described in the veterinary literature consist of meningioma and glioma occurring mainly in the brain and less often in the spinal cord. Although most neoplasms can be diagnosed based on routine histologic evaluation, less typical tumors need to be further characterized using immunohistochemistry. This review compiles the relevant information about the most common primary CNS neoplasms of cats available in the veterinary literature, aiming to serve as a converging source of information for the topic.

Occurrence and risk factors of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) in cats of Lebanon

A cross-sectional study was carried out between April 2020 and August 2021. Blood samples were collected from 260 household cats recruited in different clinics in North and Mount Lebanon, with the aim of determining the seroprevalence of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). The seroprevalence reported reached 18.84% (95% CI 0.14-0.24) and 13.84% (95% CI 0.09-0.18) for FIV and FeLV, respectively. FIV seropositivity was associated with a younger age, health and neuter status, lymphoma, lethargy, and vomiting. Furthermore, male sex, neuter status, lymphoma, anaemia, lethargy, and vomiting were significantly associated with FeLV seropositivity. This first data from Lebanon emphasizes the need for implementing preventive programmes to cope with FIV- and FeLV-associated morbidity and mortality among cats.

Infectious Causes of Neoplasia in the Domestic Cat

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

Pathohistological features of mediastinal lymphoma in domestic cats

The article covers two clinical cases of domestic cats suffering from a mediastinal form of lymphoma and provides their cytological, immunohistochemical, and pathohistological verification. The lymphoma immunophenotyping method using the B-cell markers CD79a and CD3 was used to identify T-cells. The mediastinal type of lymphoma in cats is usually rarely registered and statistically, the number of cases does not exceed 20%, which is consistent with our observations. Shortness of breath, difficulty with swallowing, lack of appetite, cyanotic mucous membranes, lymphadenomegaly of the mediastinal lymph nodes and effusion in the chest cavity were found in the clinically ill cats. An X-ray examination of the chest cavity revealed an increased contrast in the mediastinal area and displacement of the lungs towards the spine. A complete blood count revealed lymphopenia. Cytological smears of the chest cavity transudates revealed mostly monomorphic lymphoblasts with large rounded hyperchromic nuclei and narrow cytoplasm stained in light blue. The karyoplasm was somewhat granular, the nucleoli were visible, and the mitoses were atypical and numerous. The cytological picture in biopsy samples of mediastinal lymph nodes was characterized by a monomorphic population of lymphoblasts with an eccentrically located nucleus and moderately basophilic karyoplasm. The cell cytoplasm was vacuolated in some places, with presence of atypical mitotic figures. Most of the cells had two nuclei. Diffuse tumoral lesions of the chest cavity tissues, focal tumorous lesions of the lung parenchyma, and lymphadenopathy of the mediastinal lymph nodes were found during the autopsy in the first case. The second clinical case demonstrated the massive lymphadenopathy of the mediastinal lymph nodes. Histologically, a diffuse lesion by a monomorphic population of lymphoblasts was revealed in preparations from the soft tissues of the chest wall. The lymphoblasts’ insignificant cytoplasm, with nuclei from round to elliptical shape, infiltrated the chest wall’s soft tissues. It was found immunohistochemically that the blast cells showed reactivity to CD79a, and were mostly negative to CD3. This indicates the development of a large diffuse B-cell lymphoma. The immunohistochemical picture of lymph node necropsies from another cat was somewhat similar. However, it was also characterized by lymphoblasts with eccentrically placed nuclei, increased number of cells with mitotic figures, somewhat intensive CD3 antibodies expression (especially in the paracortical area of lymph nodes), and significant CD79a marker expression.

A prospective epidemiological, clinical, and clinicopathologic study of feline leukemia virus and feline immunodeficiency virus infection in 435 cats from Greece

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses causing significant morbidity and mortality in cats. The aim of this study was to describe the epidemiological, clinical and clinicopathologic aspects of FeLV and FIV infections in different populations of cats in Greece, including client-owned cats, stray cats and cats who live in catteries. A total of 435 cats were prospectively enrolled. Serological detection of FeLV antigen and FIV antibody was performed using a commercial in-house ELISA test kit. The results showed that 17 (3.9 %) and 40 (9.2 %) of the 435 cats were positive for FeLV antigen and FIV antibody, respectively, whereas 5 (1.1 %) had concurrent infection with FeLV and FIV. Factors that were associated with FeLV antigenemia, based on multivariate analysis, included vomiting, rhinitis, infection with FIV, neutropenia, decreased blood urea nitrogen and increased serum cholesterol and triglyceride concentrations. Factors associated with FIV seropositivity included male gender, older age, outdoor access, weight loss, fever, gingivostomatitis, skin lesions and/or pruritus and hyperglobulinemia. Various clinical signs and laboratory abnormalities were found to be significantly associated with retroviral infections, suggesting that current guidelines to test all sick cats should be followed, taking into particular consideration the high-risk groups of cats found in this study.

A First NGS Investigation Suggests No Association Between Viruses and Canine Cancers

Approximately 10–15% of worldwide human cancers are attributable to viral infection. When operating as carcinogenic elements, viruses may act with various mechanisms, but the most important is represented by viral integration into the host genome, causing chromosome instability, genomic mutations, and aberrations. In canine species, few reports have described an association between viral integration and canine cancers, but more comprehensive studies are needed. The advancement of next-generation sequencing and the cost reduction have resulted in a progressive increasing of sequencing data in veterinary oncology offering an opportunity to study virome in canine cancers. In this study, we have performed viral detection and integration analyses using VirusFinder2 software tool on available whole-genome and whole-exome sequencing data of different canine cancers. Several viral sequences were detected in lymphomas, hemangiosarcomas, melanomas, and osteosarcomas, but no reliable integration sites were identified. Even if with some limitations such as the depth and type of sequencing, a restricted number of available nonhuman genomes software, and a limited knowledge on endogenous retroviruses in the canine genome, results are compelling. However, further experiments are needed, and similarly to feline species, dedicated analysis tools for the identification of viral integration sites in canine cancers are required.

Immunopathologic Effects of Prednisolone and Cyclosporine A on Feline Immunodeficiency Virus Replication and Persistence

Feline immunodeficiency virus (FIV) induces opportunistic disease in chronically infected cats, and both prednisolone and cyclosporine A (CsA) are clinically used to treat complications such as lymphoma and stomatitis. However, the impact of these compounds on FIV infection are still unknown and understanding immunomodulatory effects on FIV replication and persistence is critical to guide safe and effective therapies. To determine the immunologic and virologic effects of prednisolone and CsA during FIV infection, FIV-positive cats were administered immunosuppressive doses of prednisolone (2 mg/kg) or CsA (5 mg/kg). Both prednisolone and CsA induced acute and transient increases in FIV DNA and RNA loads as detected by quantitative PCR. Changes in the proportion of lymphocyte immunophenotypes were also observed between FIV-infected and naïve cats treated with CsA and prednisolone, and both treatments caused acute increases in CD4+ lymphocytes that correlated with increased FIV RNA. CsA and prednisolone also produced alterations in cytokine expression that favored a shift toward a Th2 response. Pre-treatment with CsA slightly enhanced the efficacy of antiretroviral therapy but did not enhance clearance of FIV. Results highlight the potential for drug-induced perturbation of FIV infection and underscore the need for more information regarding immunopathologic consequences of therapeutic agents on concurrent viral infections.

Feline lymphoma in the nervous system: pathological, immunohistochemical, and etiological aspects in 16 cats

ABSTRACT: The pathological, immunohistochemical (IHC), and etiological features of lymphoma involving the nervous system (NS) in cats were analyzed through a retrospective study (2004-2017) in Rio Grande do Sul State, Brazil. The NS involvement was observed in 16 (12.2%) of 125 felines with lymphoma. Young cats were mainly affected, with a median of 24 months old. Most cases were secondary central NS lymphoma, whereas in three cats, the NS involvement was primary. IHC revealed 14 (87.5%) FeLV-positive, six FIV-positive, and one FeLV/FIV-negative cats. Distribution of feline lymphoma in the NS was 8/16 in the spinal cord, 7/16 in the brain, and 1/16 in the paravertebral nerves and ganglia (neurolymphomatosis). The lymphoma pattern in the spinal cord was exclusively extradural, often focal (6/8), and located in the lumbar (3/6), sacral (1/6), thoracic (1/6), and cervical segments (1/6). Brain neuroanatomical patterns were: leptomeningeal lymphomatosis (4/7), lymphomatous choroiditis (2/7), and intradural lymphoma (1/7). The feline with primary neurolymphomatosis presented a marked thickening of paravertebral nerves and ganglia from the sacral region. B-cell lymphoma (75%) was often diagnosed, and diffuse large B-cell lymphoma (DLBCL) (11/16) was the main subtype. T-cell lymphoma (25%) was less commonly observed and was classified as peripheral T-cell lymphoma (PTCL) (3/16) and T-cell lymphoblastic lymphoma (T-LBL) (1/16).

Feline low-grade alimentary lymphoma: an emerging entity and a potential animal model for human disease

BACKGROUND

Low-grade alimentary lymphoma (LGAL) is characterised by the infiltration of neoplastic T-lymphocytes, typically in the small intestine. The incidence of LGAL has increased over the last ten years and it is now the most frequent digestive neoplasia in cats and comprises 60 to 75% of gastrointestinal lymphoma cases. Given that LGAL shares common clinical, paraclinical and ultrasonographic features with inflammatory bowel diseases, establishing a diagnosis is challenging. A review was designed to summarise current knowledge of the pathogenesis, diagnosis, prognosis and treatment of feline LGAL. Electronic searches of PubMed and Science Direct were carried out without date or language restrictions.

RESULTS

A total of 176 peer-reviewed documents were identified and most of which were published in the last twenty years. 130 studies were found from the veterinary literature and 46 from the human medicine literature. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. The pathophysiology of feline LGAL still needs to be elucidated, not least the putative roles of infectious agents, environmental factors as well as genetic events. The most common therapeutic strategy is combination treatment with prednisolone and chlorambucil, and prolonged remission can often be achieved. Developments in immunohistochemical analysis and clonality testing have improved the confidence of clinicians in obtaining a correct diagnosis between LGAL and IBD. The condition shares similarities with some diseases in humans, especially human indolent T-cell lymphoproliferative disorder of the gastrointestinal tract.

CONCLUSIONS

The pathophysiology of feline LGAL still needs to be elucidated and prospective studies as well as standardisation of therapeutic strategies are needed. A combination of conventional histopathology and immunohistochemistry remains the current gold-standard test, but clinicians should be cautious about reclassifying cats previously diagnosed with IBD to lymphoma on the basis of clonality testing. Importantly, feline LGAL could be considered to be a potential animal model for indolent digestive T-cell lymphoproliferative disorder, a rare condition in human medicine.

Multiple, Independent T Cell Lymphomas Arising in an Experimentally FIV-Infected Cat during the Terminal Stage of Infection

Our laboratory has serially reported on the virologic and immunopathologic features of a cohort of experimental feline immunodeficiency virus (FIV)-infected cats for more than eight years. At 8.09 years post infection (PI), one of these animals entered the terminal stage of infection, characterized by undulating hyperthermia, progressive anorexia, weight loss, and pancytopenia; the animal was not responsive to therapeutic interventions, necessitating euthanasia six weeks later (8.20 years PI). Subsequent analyses indicated that neoplastic lymphocytes infiltrated multiple cervical lymph nodes and a band-like region of the mucosal lamina propria within a segment of the intestine. Immunohistochemistry and T cell clonality testing determined that the nodal and intestinal lesions were independently arising from CD3 T cell lymphomas. In-situ RNA hybridization studies indicated that diffuse neoplastic lymphocytes from the cervical lymph node contained abundant viral nucleic acid, while viral nucleic acid was not detectable in lymphocytes from the intestinal lymphoma lesion. The proviral long terminal repeat (LTR) was amplified and sequenced from multiple anatomic sites, and a common clone containing a single nucleotide polymorphism was determined to be defective in response to phorbol myristate acetate (PMA)-mediated promoter activation in a reporter gene assay. This assay revealed a previously unidentified PMA response element within the FIV U3 region 3’ to the TATA box. The possible implications of these results on FIV-lymphoma pathogenesis are discussed.

Applications of the FIV Model to Study HIV Pathogenesis

Feline immunodeficiency virus (FIV) is a naturally-occurring retrovirus that infects domestic and non-domestic feline species, producing progressive immune depletion that results in an acquired immunodeficiency syndrome (AIDS). Much has been learned about FIV since it was first described in 1987, particularly in regard to its application as a model to study the closely related lentivirus, human immunodeficiency virus (HIV). In particular, FIV and HIV share remarkable structure and sequence organization, utilize parallel modes of receptor-mediated entry, and result in a similar spectrum of immunodeficiency-related diseases due to analogous modes of immune dysfunction. This review summarizes current knowledge of FIV infection kinetics and the mechanisms of immune dysfunction in relation to opportunistic disease, specifically in regard to studying HIV pathogenesis. Furthermore, we present data that highlight changes in the oral microbiota and oral immune system during FIV infection, and outline the potential for the feline model of oral AIDS manifestations to elucidate pathogenic mechanisms of HIV-induced oral disease. Finally, we discuss advances in molecular biology, vaccine development, neurologic dysfunction, and the ability to apply pharmacologic interventions and sophisticated imaging technologies to study experimental and naturally occurring FIV, which provide an excellent, but often overlooked, resource for advancing therapies and the management of HIV/AIDS.

Skin as a marker of general feline health: Cutaneous manifestations of infectious disease

Practical relevance: Infectious disease in feline patients often presents a diagnostic challenge. This article reviews the most relevant viral, bacterial and protozoal diseases and their cutaneous manifestations. Many of the diseases discussed have overlapping presentations or may mimic more common noninfectious disease processes. The purpose of the article is to reinforce knowledge of common and uncommon infectious diseases, help practitioners identify possible infectious dermatoses, create a comprehensive and prioritized differential list, and provide guidance for the diagnosis of these diseases. A working knowledge of these clinical syndromes is important if what is thought to be a case of a common disease does not respond to conventional management.

AUDIENCE

This review is aimed at veterinarians who treat cats and especially those with an interest in feline dermatology. Tables are included to allow the reader to formulate a concise list of differential diagnoses for clinically similar presentations. The diagnostic approach to a case of ulcerative facial dermatitis is reviewed in a Case Notes quiz. Evidence base: This article includes up-to-date information regarding dermatologic manifestations of less commonly encountered feline cutaneous infectious diseases. Information has been drawn from the published, peer-reviewed literature and the most recent textbook chapters with a particular aim of describing and differentiating clinical lesions and the diagnostic approach to cutaneous disease, especially in unusual cases.

Primary cerebellar lymphoma with Hodgkin lymphoma-like morphology in a cat

A 4-y-old cat exhibited neurologic signs such as wobbling, right head tilt, and intention tremor, and MRI revealed a mass in the cerebellum. The cat died 5 mo after initial presentation, and no neoplastic lesions, other than the cerebellar mass, were observed at autopsy. Histologically, large atypical cells resembling Hodgkin cells, with single large inclusion-like nucleoli, and those resembling Reed-Sternberg cells, with symmetrically arranged nuclei, had infiltrated the left side of the cerebellum and were admixed with small lymphocytes. These atypical cells were positive for feline leukemia virus (FeLV), CD20, BLA36, vimentin, p16, p53, and Pax5, and negative for CD3, CD79a, and Iba1 by immunohistochemistry. Multiplex PCR for immunoglobulin heavy-chain gene rearrangement revealed monoclonal proliferation of B-lymphocytes. We describe this feline primary cerebellar B-cell lymphoma that displayed Hodgkin lymphoma-like tumor cells with FeLV protein expression.

Role of Feline Immunodeficiency Virus in Lymphomagenesis--Going Alone or Colluding?

Feline immunodeficiency virus (FIV) is a naturally occurring lentivirus of domestic and nondomestic feline species. Infection in domestic cats leads to immune dysfunction via mechanisms similar to those caused by human immunodeficiency virus (HIV) and, as such, is a valuable natural animal model for acquired immunodeficiency syndrome (AIDS) in humans. An association between FIV and an increased incidence of neoplasia has long been recognized, with frequencies of up to 20% in FIV-positive cats recorded in some studies. This is similar to the rate of neoplasia seen in HIV-positive individuals, and in both species neoplasia typically requires several years to arise. The most frequently reported type of neoplasia associated with FIV infection is lymphoma. Here we review the possible mechanisms involved in FIV lymphomagenesis, including the possible involvement of coinfections, notably those with gamma-herpesviruses.

Commercially Available Enzyme-Linked Immunosorbent Assay and Polymerase Chain Reaction Tests for Detection of Feline Immunodeficiency Virus Infection

BACKGROUND

Feline immunodeficiency virus (FIV) infection is an important cause of disease of cats worldwide. Initial screening is commonly performed by commercially available point-of-care (POC) ELISA tests. Confirmatory testing for positive POC test results is recommended. Polymerase chain reaction (PCR) tests for FIV are commonly used additional testing methods; however, reported measures of diagnostic accuracy vary widely between PCR tests, making interpretation of results difficult.

HYPOTHESIS/OBJECTIVE

There is very good agreement between results of a commercially available PCR test and a POC ELISA test for FIV for specimens collected from owned and shelter-housed cats.

ANIMALS

Blood samples from 168 cats from 2 adoption guarantee shelters, an FIV Sanctuary, and 64 private homes were used.

METHODS

This was a prospective study. Whole blood samples were collected in K₂ -EDTA, divided, and submitted for PCR and ELISA testing. Follow-up whole blood samples were collected in lithium heparin from cats with discordant results and submitted for virus isolation (VI).

RESULTS

There was very good agreement between ELISA and PCR (kappa 0.87; P < .001; 95% CI 0.79, 0.95). Of 168 cats, eleven had discordant ELISA/PCR results: 7 ELISA+/PCR- and 4 ELISA-/PCR+. Using VI as a reference standard, there were 4 false-positive PCR results, 5 false-positive ELISA results, and 1 false-negative PCR result (1 cat lost to follow-up).

CONCLUSIONS AND CLINICAL IMPORTANCE

While there was good agreement between the POC ELISA and PCR tests, the discordant results highlight the importance of cautious interpretation of test results and the necessity of confirmatory testing.

Detection of Felis catus gammaherpesvirus 1 (FcaGHV1) in peripheral blood B- and T-lymphocytes in asymptomatic, naturally-infected domestic cats

The domestic cat is natural host to both feline immunodeficiency virus and Felis catus gammaherpesvirus 1 (FcaGHV1). Comparative data suggest that these agents might act as synergistic copathogens in feline AIDS-related lymphoma. To identify leucocyte subsets harbouring gammaherpesvirus DNA, whole blood from 5 healthy, FcaGHV1-infected cats was labelled with monoclonal antibodies to feline CD21, CD4, CD8 and CD14 for 4-way fluorescence-activated cell sorting. FcaGHV1gB qPCR was performed on DNA extracted from purified fractions and whole blood longitudinally. FcaGHV1 DNA was detected in CD21+, CD4+, CD8+, but not CD14+ cells. Variation in whole blood load, up to 19,788 copies/10(6)cells, was detected in individual cats over time. FcaGHV1 DNA was undetectable in one cat on one occasion highlighting that qPCR of whole blood from a single time point will not detect all cases of FcaGHV1 infection. Further investigation of the role of FcaGHV1 in feline lymphoid malignancies is warranted.

Seroprevalence of feline immunodeficiency virus and feline leukaemia virus in Australia: risk factors for infection and geographical influences (2011-2013)

OBJECTIVES

Our aim was to: (i) determine the current seroprevalence of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) in three large cohorts of cats from Australia; and (ii) investigate potential risk factors for retroviral infection.

METHODS

Cohort 1 (n = 2151 for FIV, n = 2241 for FeLV) consisted of cats surrendered to a shelter on the west coast of Australia (Perth, Western Australia [WA]). Cohort 2 (n = 2083 for FIV, n = 2032 for FeLV) consisted of client-owned cats with outdoor access recruited from around Australia through participating veterinary clinics. Cohort 3 (n = 169 for FIV, n = 166 for FeLV) consisted of cats presenting to Murdoch University Veterinary Hospital for a variety of reasons. Fresh whole blood was collected and tested using a commercially available point-of-care lateral flow ELISA kit that detects p27 FeLV antigen and antibodies to FIV antigens (p15 and p24) (cohorts 1 and 2), or one of two lateral flow immunochromatography kits that detect p27 antigen and antibodies to FIV antigen (p24 and/or gp40) (cohort 3). Data recorded for cats in cohort 2 included signalment, presenting complaint and postcode, allowing investigation of risk factors for FIV or FeLV infection, as well as potential geographical 'hot spots' for infection.

RESULTS

The seroprevalence of FIV was 6% (cohort 1), 15% (cohort 2) and 14% (cohort 3), while the seroprevalence of FeLV was 1%, 2% and 4% in the same respective cohorts. Risk factors for FIV infection among cats in cohort 2 included age (>3 years), sex (male), neutering status (entire males) and location (WA had a significantly higher FIV seroprevalence compared with the Australian Capital Territory, New South Wales and Victoria). Risk factors for FeLV infection among cats in cohort 2 included health status ('sick') and location (WA cats were approximately three times more likely to be FeLV-infected compared with the rest of Australia). No geographical hot spots of FIV infection were identified.

CONCLUSIONS AND RELEVANCE

Both FIV and FeLV remain important infections among Australian cats. WA has a higher seroprevalence of both feline retroviruses compared with the rest of Australia, which has been noted in previous studies. A lower neutering rate for client-owned male cats is likely responsible for the higher seroprevalence of FIV infection in WA cats, while the reason for the higher seroprevalence of FeLV in WA cats is currently unknown.

Novel gammaherpesviruses in North American domestic cats, bobcats, and pumas: identification, prevalence, and risk factors

Gammaherpesviruses (GHVs) are a diverse and rapidly expanding group of viruses associated with a variety of disease conditions in humans and animals. To identify felid GHVs, we screened domestic cat (Felis catus), bobcat (Lynx rufus), and puma (Puma concolor) blood cell DNA samples from California, Colorado, and Florida using a degenerate pan-GHV PCR. Additional pan-GHV and long-distance PCRs were used to sequence a contiguous 3.4-kb region of each putative virus species, including partial glycoprotein B and DNA polymerase genes. We identified three novel GHVs, each present predominantly in one felid species: Felis catus GHV 1 (FcaGHV1) in domestic cats, Lynx rufus GHV 1 (LruGHV1) in bobcats, and Puma concolor GHV 1 (PcoGHV1) in pumas. To estimate infection prevalence, we developed real-time quantitative PCR assays for each virus and screened additional DNA samples from all three species (n = 282). FcaGHV1 was detected in 16% of domestic cats across all study sites. LruGHV1 was detected in 47% of bobcats and 13% of pumas across all study sites, suggesting relatively common interspecific transmission. PcoGHV1 was detected in 6% of pumas, all from a specific region of Southern California. The risk of infection for each host varied with geographic location. Age was a positive risk factor for bobcat LruGHV1 infection, and age and being male were risk factors for domestic cat FcaGHV1 infection. Further characterization of these viruses may have significant health implications for domestic cats and may aid studies of free-ranging felid ecology.

IMPORTANCE

Gammaherpesviruses (GHVs) establish lifelong infection in many animal species and can cause cancer and other diseases in humans and animals. In this study, we identified the DNA sequences of three GHVs present in the blood of domestic cats (Felis catus), bobcats (Lynx rufus), and pumas (Puma concolor; also known as mountain lions, cougars, and panthers). We found that these viruses were closely related to, but distinct from, other known GHVs of animals and represent the first GHVs identified to be native to these feline species. We developed techniques to rapidly and specifically detect the DNA of these viruses in feline blood and found that the domestic cat and bobcat viruses were widespread across the United States. In contrast, puma virus was found only in a specific region of Southern California. Surprisingly, the bobcat virus was also detected in some pumas, suggesting relatively common virus transmission between these species. Adult domestic cats and bobcats were at greater risk for infection than juveniles. Male domestic cats were at greater risk for infection than females. This study identifies three new viruses that are widespread in three feline species, indicates risk factors for infection that may relate to the route of infection, and demonstrates cross-species transmission between bobcats and pumas. These newly identified viruses may have important effects on feline health and ecology.

Primary cerebral T-cell lymphoma in a sea otter (enhydra lutris)

A 10-year-old female sea otter exhibited convulsions, arrhythmia, hyperthermia, forced breathing and anorexia and died after a week. Histopathological examination revealed neoplastic proliferation of small round cells with scant cytoplasm and round or oval nuclei distributed mainly in the thalamus. The proliferation of neoplastic cells was observed in the cerebral parenchyma and perivascular areas. The neoplastic cells were immunopositive for CD3, but not CD20. No neoplastic proliferation of T-cells was found in other organs. Taken together, we diagnosed this case as a primary cerebral T-cell lymphoma. To our knowledge, this is the first case of primary cerebral T-cell lymphoma in a sea otter.

Clinical findings and survival in cats naturally infected with feline immunodeficiency virus

BACKGROUND

The clinical course and outcome of natural feline immunodeficiency virus (FIV) infection are variable and incompletely understood. Assigning clinical relevance to FIV infection in individual cats represents a considerable clinical challenge.

OBJECTIVE

To compare signalment, hematologic and biochemical data, major clinical problem, and survival among client-owned, FIV-infected, and uninfected domestic cats.

ANIMALS

Client-owned, domestic cats tested for FIV (n = 520).

METHODS

Retrospective, case control study. Logistic regression analyses were conducted to identify risk factors for FIV infection and to compare hematologic and biochemical data between cases and controls, after adjusting for potential confounders. Survival times were compared using Kaplan-Meier curves.

RESULTS

The prevalence of FIV infection was 14.6%. Mixed breed, male sex, and older age were risk factors for FIV infection. Hematologic abnormalities, biochemical abnormalities or both were common in both FIV-infected and uninfected cats. Lymphoid malignancies were slightly more common in FIV-infected than uninfected cats. Survival of FIV-infected cats was not significantly different from that of uninfected cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

Multiple hematologic and biochemical abnormalities are common in old, sick cats regardless of their FIV status. Their presence should not be assumed to indicate clinical progression of FIV infection. A negative effect of FIV on survival was not apparent in this study.

Selective expansion of viral variants following experimental transmission of a reconstituted feline immunodeficiency virus quasispecies

Following long-term infection with virus derived from the pathogenic GL8 molecular clone of feline immunodeficiency virus (FIV), a range of viral variants emerged with distinct modes of interaction with the viral receptors CD134 and CXCR4, and sensitivities to neutralizing antibodies. In order to assess whether this viral diversity would be maintained following subsequent transmission, a synthetic quasispecies was reconstituted comprising molecular clones bearing envs from six viral variants and its replicative capacity compared in vivo with a clonal preparation of the parent virus. Infection with either clonal (Group 1) or diverse (Group 2) challenge viruses, resulted in a reduction in CD4+ lymphocytes and an increase in CD8+ lymphocytes. Proviral loads were similar in both study groups, peaking by 10 weeks post-infection, a higher plateau (set-point) being achieved and maintained in study Group 1. Marked differences in the ability of individual viral variants to replicate were noted in Group 2; those most similar to GL8 achieved higher viral loads while variants such as the chimaeras bearing the B14 and B28 Envs grew less well. The defective replication of these variants was not due to suppression by the humoral immune response as virus neutralising antibodies were not elicited within the study period. Similarly, although potent cellular immune responses were detected against determinants in Env, no qualitative differences were revealed between animals infected with either the clonal or the diverse inocula. However, in vitro studies indicated that the reduced replicative capacity of variants B14 and B28 in vivo was associated with altered interactions between the viruses and the viral receptor and co-receptor. The data suggest that viral variants with GL8-like characteristics have an early, replicative advantage and should provide the focus for future vaccine development.

Acute virulent infection with feline immunodeficiency virus (FIV) results in lymphomagenesis via an indirect mechanism

Four cats (24%) experimentally infected with FIV unexpectedly developed neoplastic changes within four months of inoculation. While FIV has previously been associated with neoplasia, the rapidity and high attack rate seen here is highly unusual. PCR for antigen receptor rearrangements (PARR) detected clonally rearranged T cells in two animals diagnosed with B cell follicular lymphoma by classical means. All cats were negative for feline leukemia virus; gamma-herpesvirus DNA was not amplified using degenerate primers. FIV proviral load in neoplastic tissue was two orders of magnitude lower than in the periphery, lower in neoplastic vs non-neoplastic lymph node, and clonal integration was not detected. We hypothesize that neoplasia was secondary to FIV immune dysregulation, and show that PARR can augment our capacity to phenotype these tumors and distinguish follicular hyperplasia from lymphoma. Age of exposure and relative virulence of the inoculum likely contributed to this unusual presentation of FIV infection.

Clinical aspects of feline retroviruses: a review

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses with global impact on the health of domestic cats. The two viruses differ in their potential to cause disease. FeLV is more pathogenic, and was long considered to be responsible for more clinical syndromes than any other agent in cats. FeLV can cause tumors (mainly lymphoma), bone marrow suppression syndromes (mainly anemia), and lead to secondary infectious diseases caused by suppressive effects of the virus on bone marrow and the immune system. Today, FeLV is less commonly diagnosed than in the previous 20 years; prevalence has been decreasing in most countries. However, FeLV importance may be underestimated as it has been shown that regressively infected cats (that are negative in routinely used FeLV tests) also can develop clinical signs. FIV can cause an acquired immunodeficiency syndrome that increases the risk of opportunistic infections, neurological diseases, and tumors. In most naturally infected cats, however, FIV itself does not cause severe clinical signs, and FIV-infected cats may live many years without any health problems. This article provides a review of clinical syndromes in progressively and regressively FeLV-infected cats as well as in FIV-infected cats.

Feline alimentary lymphoma: 1. Classification, risk factors, clinical signs and non-invasive diagnostics

PRACTICAL RELEVANCE

Alimentary lymphoma (AL) occurs commonly in cats and exists as distinct subtypes that differ in their clinical course, response to treatment and prognosis. Accurate diagnosis is important to guide appropriate treatment.

CLINICAL CHALLENGES

Differentiation of low-grade alimentary lymphoma from lymphoplasmacytic enteritis can be challenging, especially where endoscopic intestinal biopsies, which sample only the mucosa and submucosa, are used. The major differentials for intermediate- and high-grade alimentary lymphoma are other neoplastic and non-neoplastic intestinal mass lesions. The diagnosis of large granular lymphocyte lymphoma requires vigilance as it may be missed with routine diagnostics.

PATIENT GROUP

AL affects predominantly middle- to old-aged domestic crossbred cats (median age 10-13 years).

EVIDENCE BASE

The evidence supporting this review is grade II, III and IV, derived from prospective studies, retrospective case series, reviews, extrapolation from other species, pathophysiological justification and the combined clinical experience of those working in the field.

The molecular biology of feline immunodeficiency virus (FIV)

Feline immunodeficiency virus (FIV) is widespread in feline populations and causes an AIDS-like illness in domestic cats. It is highly prevalent in several endangered feline species. In domestic cats FIV infection is a valuable small animal model for HIV infection. In recent years there has been sa significant increase in interest in FIV, in part to exploit this, but also because of the potential it has as a human gene therapy vector. Though much less studied than HIV there are many parallels in the replication of the two viruses, but also important differences and, despite their likely common origin, the viruses have in some cases used alternative strategies to overcome similar problems. Recent advances in understanding the structure and function of FIV RNA and proteins and their interactions has enhanced our knowledge of FIV replication significantly, however, there are still many gaps. This review summarizes our current knowledge of FIV molecular biology and its similarities with, and differences from, other lentiviruses.

Clinical aspects of feline immunodeficiency and feline leukemia virus infection

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses with a global impact on the health of domestic cats. The two viruses differ in their potential to cause disease. FIV can cause an acquired immunodeficiency syndrome that increases the risk of developing opportunistic infections, neurological diseases, and tumors. In most naturally infected cats, however, FIV itself does not cause severe clinical signs, and FIV-infected cats may live many years without any health problems. FeLV is more pathogenic, and was long considered to be responsible for more clinical syndromes than any other agent in cats. FeLV can cause tumors (mainly lymphoma), bone marrow suppression syndromes (mainly anemia) and lead to secondary infectious diseases caused by suppressive effects of the virus on bone marrow and the immune system. Today, FeLV is less important as a deadly infectious agent as in the last 20 years prevalence has been decreasing in most countries.

The role of BST2/tetherin in feline retrovirus infection

Pathogenic retroviral infections of mammals have induced the evolution of cellular anti-viral restriction factors and have shaped their biological activities. This intrinsic immunity plays an important role in controlling viral replication and imposes a barrier to viral cross-species transmission. Well-studied examples of such host restriction factors are TRIM5α, an E3 ubiquitin ligase that binds incoming retroviral capsids in the cytoplasm via its C-terminal PRY/SPRY (B30.2) domain and targets them for proteasomal degradation, and APOBEC3 proteins, cytidine deaminases that induce hypermutation and impair viral reverse transcription. Tetherin (BST-2, CD317) is an interferon-inducible transmembrane protein that potently inhibits the release of nascent retrovirus particles in single-cycle replication assays. However, whether the primary biological activity of tetherin in vivo is that of a restriction factor remains uncertain as recent studies on human tetherin suggest that it is unable to prevent spreading infection of human immunodeficiency virus type 1 (HIV-1). The feline tetherin homologue resembles human tetherin in amino acid sequence, protein topology and anti-viral activity. Transiently expressed feline tetherin displays potent inhibition of feline immunodeficiency virus (FIV) and HIV-1 particle release. However, stable ectopic expression of feline tetherin in a range of feline cell lines has no inhibitory effect on the growth of either primary or cell culture-adapted strains of FIV. By comparing and contrasting the activities of the felid and primate tetherins against their respective immunodeficiency-causing lentiviruses we may gain insight into the contribution of tetherins to the control of lentiviral replication and the evolution of lentiviral virulence.

FIV associated neoplasms--a mini-review

Retroviral induced neoplasms have been key to understanding oncogenesis and are important etiologic agents associated with cancer formation. Cats infected with feline immunodeficiency virus (FIV), the feline analogue to human immunodeficiency virus (HIV), are reported to be at increased incidence of neoplasia. This review highlights reported risk factors and tumor cell phenotypes associated with neoplasias arising in FIV-infected animals, differences in oncogenic disease in natural versus experimental FIV infections, and similarities between FIV- and HIV-related malignancies. The most common type of FIV-associated neoplasm reported in the literature is lymphoma, specifically of B-cell origin, with experimentally infected cats developing neoplastic lesions at an earlier age than their naturally infected cohorts. The mechanism of FIV-induced lymphoma has not been completely ascertained, though the majority of published studies addressing this issue suggest oncogenesis arises via indirect mechanisms. HIV-infected individuals have increased risk of neoplasia, specifically B cell lymphoma, in comparison with uninfected individuals. Additional similarities between FIV- and HIV-associated neoplasms include the presence of extranodal lymphoma, a synergism with other oncogenic viruses, and an apparent indirect mechanism of induced oncogenesis. This literature supports study of FIV-associated neoplasms to further characterize this lentiviral-neoplasia association for the benefit of both human and animal disease, and to advance our general knowledge of mechanisms for viral-induced oncogenesis.

Malignant lymphoma in african lions (panthera leo)

Malignant lymphoma has become an increasingly recognized problem in African lions (Panthera leo). Eleven African lions (9 male and 2 female) with clinical signs and gross and microscopic lesions of malignant lymphoma were evaluated in this study. All animals were older adults, ranging in age from 14 to 19 years. Immunohistochemically, 10 of the 11 lions had T-cell lymphomas (CD3(+), CD79a(-)), and 1 lion was diagnosed with a B-cell lymphoma (CD3(-), CD79a(+)). The spleen appeared to be the primary site of neoplastic growth in all T-cell lymphomas, with involvement of the liver (6/11) and regional lymph nodes (5/11) also commonly observed. The B-cell lymphoma affected the peripheral lymph nodes, liver, and spleen. According to the current veterinary and human World Health Organization classification of hematopoietic neoplasms, T-cell lymphoma subtypes included peripheral T-cell lymphoma (4/11), precursor (acute) T-cell lymphoblastic lymphoma/leukemia (2/11), chronic T-cell lymphocytic lymphoma/leukemia (3/11), and T-zone lymphoma (1/11). The single B-cell lymphoma subtype was consistent with diffuse large B-cell lymphoma. Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) testing by immunohistochemistry on sections of malignant lymphoma was negative for all 11 lions. One lion was seropositive for FeLV. In contrast to domestic and exotic cats, in which B-cell lymphomas are more common than T-cell lymphomas, African lions in this study had malignant lymphomas that were primarily of T-cell origin. Neither FeLV nor FIV, important causes of malignant lymphoma in domestic cats, seems to be significant in the pathogenesis of malignant lymphoma in African lions.

Modulation of the virus-receptor interaction by mutations in the V5 loop of feline immunodeficiency virus (FIV) following in vivo escape from neutralising antibody

Background

In the acute phase of infection with feline immunodeficiency virus (FIV), the virus targets activated CD4+ T cells by utilising CD134 (OX40) as a primary attachment receptor and CXCR4 as a co-receptor. The nature of the virus-receptor interaction varies between isolates; strains such as GL8 and CPGammer recognise a "complex" determinant on CD134 formed by cysteine-rich domains (CRDs) 1 and 2 of the molecule while strains such as PPR and B2542 require a more "simple" determinant comprising CRD1 only for infection. These differences in receptor recognition manifest as variations in sensitivity to receptor antagonists. In this study, we ask whether the nature of the virus-receptor interaction evolves in vivo.

Results

Following infection with a homogeneous viral population derived from a pathogenic molecular clone, a quasispecies emerged comprising variants with distinct sensitivities to neutralising antibody and displaying evidence of conversion from a "complex" to a "simple" interaction with CD134. Escape from neutralising antibody was mediated primarily by length and sequence polymorphisms in the V5 region of Env, and these alterations in V5 modulated the virus-receptor interaction as indicated by altered sensitivities to antagonism by both anti-CD134 antibody and soluble CD134.

Conclusions

The FIV-receptor interaction evolves under the selective pressure of the host humoral immune response, and the V5 loop contributes to the virus-receptor interaction. Our data are consistent with a model whereby viruses with distinct biological properties are present in early versus late infection and with a shift from a "complex" to a "simple" interaction with CD134 with time post-infection.

Dominance of highly divergent feline leukemia virus A progeny variants in a cat with recurrent viremia and fatal lymphoma

Background

In a cat that had ostensibly recovered from feline leukemia virus (FeLV) infection, we observed the reappearance of the virus and the development of fatal lymphoma 8.5 years after the initial experimental exposure to FeLV-A/Glasgow-1. The goals of the present study were to investigate this FeLV reoccurrence and molecularly characterize the progeny viruses.

Results

The FeLV reoccurrence was detected by the presence of FeLV antigen and RNA in the blood and saliva. The cat was feline immunodeficiency virus positive and showed CD4⁺ T-cell depletion, severe leukopenia, anemia and a multicentric monoclonal B-cell lymphoma. FeLV-A, but not -B or -C, was detectable. Sequencing of the envelope gene revealed three FeLV variants that were highly divergent from the virus that was originally inoculated (89-91% identity to FeLV-A/Glasgow-1). In the long terminal repeat 31 point mutations, some previously described in cats with lymphomas, were detected. The FeLV variant tissue provirus and viral RNA loads were significantly higher than the FeLV-A/Glasgow-1 loads. Moreover, the variant loads were significantly higher in lymphoma positive compared to lymphoma negative tissues. An increase in the variant provirus blood load was observed at the time of FeLV reoccurrence.

Conclusions

Our results demonstrate that ostensibly recovered FeLV provirus-positive cats may act as a source of infection following FeLV reactivation. The virus variants that had largely replaced the inoculation strain had unusually heavily mutated envelopes. The mutations may have led to increased viral fitness and/or changed the mutagenic characteristics of the virus.

Feline immunodeficiency virus env gene evolution in experimentally infected cats

Feline immunodeficiency virus (FIV), an immunosuppressive lentivirus found in cats worldwide, is studied to illuminate mechanisms of lentiviral pathogenesis and to identify key components of protective immunity. During replication, lentiviruses accumulate errors of nucleotide mis-incorporation due to the low-fidelity of reverse transcriptase and recombination between viral variants, resulting in the emergence of a complex viral "quasispecies". In patients infected with HIV-1, env sequences may vary by up to 10% and the detection of quasispecies with greater heterogeneity is associated with higher viral loads and reduced CD4+ T cell numbers [1], indicating that transmission of more complex quasispecies may lead to disease progression. However, little is known about how FIV evolves as disease progresses, or why some cats develop AIDS rapidly while disease progression is slow in others. The aim of this study was to determine whether disease progression may be governed by viral evolution and to examine the diversity of viral variants emerging following infection with an infectious molecular clone. The FIV env gene encoding the envelope glycoprotein (Env) was examined at early (12 weeks) and late (322 weeks) stages of FIV infection in two groups of cats infected experimentally with the FIV-GL8 molecular clone. Viral variants were detected within quasispecies in cats in the late stages of FIV infection that contained differing amino acid compositions in several variable loops of Env, some of which were identified as determinants of receptor usage and resistance to neutralization. Therefore these results indicate that the FIV env gene evolves during the course of infection, giving rise to variants that resist neutralization and likely lead to disease progression.

Feline immunodeficiency. ABCD guidelines on prevention and management

Overview

Feline immunodeficiency virus (FIV) is a retrovirus closely related to human immunodeficiency virus. Most felids are susceptible to FIV, but humans are not. Feline immunodeficiency virus is endemic in domestic cat populations worldwide. The virus loses infectivity quickly outside the host and is susceptible to all disinfectants.

Infection

Feline immunodeficiency virus is transmitted via bites. The risk of transmission is low in households with socially well-adapted cats. Transmission from mother to kittens may occur, especially if the queen is undergoing an acute infection. Cats with FIV are persistently infected in spite of their ability to mount antibody and cell-mediated immune responses.

Disease signs

Infected cats generally remain free of clinical signs for several years, and some cats never develop disease, depending on the infecting isolate. Most clinical signs are the consequence of immunodeficiency and secondary infection. Typical manifestations are chronic gingivostomatitis, chronic rhinitis, lymphadenopathy, weight loss and immune-mediated glomerulonephritis.

Diagnosis

Positive in-practice ELISA results obtained in a low-prevalence or low-risk population should always be confirmed by a laboratory. Western blot is the ‘gold standard’ laboratory test for FIV serology. PCR-based assays vary in performance.

Disease management

Cats should never be euthanased solely on the basis of an FIV-positive test result. Cats infected with FIV may live as long as uninfected cats, with appropriate management. Asymptomatic FIV-infected cats should be neutered to avoid fighting and virus transmission. Infected cats should receive regular veterinary health checks. They can be housed in the same ward as other patients, but should be kept in individual cages.

Vaccination recommendations

At present, there is no FIV vaccine commercially available in Europe. Potential benefits and risks of vaccinating FIV-infected cats should be assessed on an individual cat basis. Needles and surgical instruments used on FIV-positive cats may transmit the virus to other cats, so strict hygiene is essential.

Genetically divergent strains of feline immunodeficiency virus from the domestic cat (Felis catus) and the African lion (Panthera leo) share usage of CD134 and CXCR4 as entry receptors

The env open reading frames of African lion (Panthera leo) lentivirus (feline immunodeficiency virus [FIV(Ple)]) subtypes B and E from geographically distinct regions of Africa suggest two distinct ancestries, with FIV(Ple)-E sharing a common ancestor with the domestic cat (Felis catus) lentivirus (FIV(Fca)). Here we demonstrate that FIV(Ple)-E and FIV(Fca) share the use of CD134 (OX40) and CXCR4 as a primary receptor and coreceptor, respectively, and that both lion CD134 and CXCR4 are functional receptors for FIV(Ple)-E. The shared usage of CD134 and CXCR4 by FIV(Fca) and FIV(Ple)-E may have implications for in vivo cell tropism and the pathogenicity of the E subtype among free-ranging lion populations.

Feline large granular lymphocyte (LGL) lymphoma with secondary leukemia: primary intestinal origin with predominance of a CD3/CD8(alpha)(alpha) phenotype

Clinicopathologic and immunophenotypic characteristics of large granular lymphocyte (LGL) neoplasia in 21 cats were examined. All cats were domestic short (19) or long hair (2) with a mean age of 9.3 years at diagnosis. Increased peripheral blood LGL counts were present in 18/21 cats. Neutrophilia (12/21 cats) and increased serum liver enzymes (7/12), total and direct bilirubin (7/13), BUN (5/14), and creatinine (2/14) were observed. Cats usually presented with advanced disease and none survived longer than 84 days (mean 18.8 days) postdiagnosis. Cytologically, LGLs had a mature (6/21), immature (13/21), or mixed (2/21) morphology. Necropsy lesions consisted of neoplastic lymphoid infiltrates in the jejunum, ileum, and duodenum in decreasing order of frequency. In the small intestine, mucosal ulceration (9/13) and epitheliotropism of neoplastic cells (9/13) were common. Neoplastic infiltrates were also present in the mesenteric lymph nodes (13/13), liver (12/13), spleen (8/13), kidneys (5/7), and bone marrow (5/7). A T cell phenotype (CD3epsilon+) characterized LGL neoplasia in 19/21 cases. A CD8alphaalpha+ cytotoxic/suppressor phenotype was present in 12/19 T cell tumors, 2 had a CD4+CD8alphaalpha phenotype, 3 had a CD4-CD8- phenotype, and 2 were CD4+ helper T cells. CD8beta chain expression was not detected in any instance. In two cats, a B or T cell origin could not be established. CD103 was expressed by 11 of 19 (58%) of the lymphomas tested. The immunophenotypic features shared by neoplastic LGLs in the cat and feline intestinal intraepithelial lymphocytes (IELs) support a small intestinal IEL origin for feline LGL lymphoma.

Immunohistochemical Diagnosis of Alimentary Lymphomas and Severe Intestinal Inflammation in Cats

Intestinal tissue samples were examined from 32 cats in which a histopathological diagnosis of alimentary lymphoma or multicentric lymphoma affecting the gastrointestinal tract had been made. These samples were re-evaluated histopathologically and serial sections were examined immunohistochemically with antisera specific for the lymphoid markers CD3, CD79a and BLA-36 and for class II molecules of the major histocompatability complex. The cats ranged in age from 4-16 years (median 10.5 years). The main presenting clinical signs were vomiting, diarrhoea and weight loss. The majority of alimentary lymphomas were of the B-cell type (n=15), whereas cases of T-cell lymphoma were fewer in number (n=8). Four cats had lymphoma of a mixed T-and B-cell phenotype. In five of the cats, immunohistochemistry suggested an inflammatory process, in contradiction to the original histopathological diagnosis of lymphoma. Immunolabelling would appear to be a useful adjunct to histopathology in classifying cases of feline alimentary lymphoma, and may help in distinguishing lymphoma from severe intestinal inflammation.

Neuropathology associated with feline immunodeficiency virus infection highlights prominent lymphocyte trafficking through both the blood-brain and blood-choroid plexus barriers

Feline immunodeficiency virus (FIV) infection in the cat is a well-evaluated model of human immunodeficiency virus (HIV)-1 infection in man with both viruses associated with significant neuropathology. Although studies in both HIV and FIV infections have shown that virus enters the brain in the acute stages of disease, little is known of the mechanisms of viral entry. The dissection of this stage is fundamental to the development of therapies that may prevent or modulate central nervous system (CNS) infection. The present study was designed to characterize the early sequential neuropathological changes following infection with FIV(GL8), a strain known to enter the CNS in acute infection. Cats were infected either by the intraperitoneal (n = 13) or intravenous (n = 12) route with 2000 cat infectious units of virus. Histopathological assessments following intraperitoneal infections were at 4 (n = 2), 5 (n = 1), 8 (n = 3), 10 (n = 1), 16 (n = 1), 32 (n = 2), 52 (n = 2), and 104 (n = 1) weeks post infection whereas animals infected intravenously were examined (n = 3) at 1, 4, 10, and 23 weeks post infection. The most significant lesions following both routes of infection were lymphocyte-rich perivascular infiltrates within cerebral and cerebellar meninges, in choroid plexus and spinal cord dura mater and within epineurium of the sciatic nerve. In addition, following intravenous infection perivascular infiltrations were noted in parenchymal blood vessels primarily of cerebral white matter. Infiltrates were composed of CD79+ B cells and CD3+ T cells. The latter population contained a mixture of CD4+ and CD8+ cells. The severity of lesions increased in intensity in the 8-to 16-week period following infection and then began to wane. The evaluation of this large group of cats at multiple time points revealed pathology comparable with that of early stage HIV-1-associated encephalitis. Moreover, in contrast to previous FIV neuropathology studies, transient meningeal, choroid plexus, and parenchymal vascular pathology were consistent significant findings suggesting that, as in HIV-1 infection, blood-brain barrier and choroid plexus brain barrier integrity are both compromised in early infection.

Feline gastrointestinal lymphoma

Gastrointestinal lymphoma is a common cause of anorexia and weight loss in older cats, with or without vomiting or diarrhea. Most cats are feline leukemia virus-negative and feline immunodeficiency virus-negative. Low-grade gastrointestinal lymphoma may be more common than previously thought, and these cats respond better to chemotherapy agents than cats with high-grade lymphoma. The most significant prognostic indicator is initial response to chemotherapy, with cats that survive the initial induction period generally achieving long-term remission. Thus far, investigations into molecular markers and immunophenotyping have failed to identify useful prognostic indicators.