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.

Concomitant feline immunodeficiency virus (FIV) and Mycoplasma haemofelis in a barn cat

A 5-year-old male barn cat was presented with lethargy and excessive bleeding following castration. The patient developed hemolytic anemia and diagnostic tests revealed infection with feline immunodeficiency virus and Mycoplasma haemofelis. This case serves as a reminder of the importance of testing for infectious diseases and educating owners on feline infectious disease prevention and management.

Toxoplasma gondii, Dirofilaria immitis, feline immunodeficiency virus (FIV), and feline leukemia virus (FeLV) infections in stray and pet cats (Felis catus) in northwest China: co-infections and risk factors

This study was conducted to estimate the prevalence of Toxoplasma gondii, Dirofilaria immitis, feline immunodeficiency virus (FIV), and feline leukemia virus (FeLV) infections among stray and pet cats in Lanzhou, northwest China, and to identify the influence of age, gender, and regions on seropositivity. T. gondii antibodies were examined in cat sera by the modified agglutination test (MAT). The circulating antigens of D. immitis and FeLV and specific antibodies to FIV were examined using kits commercially available. The overall prevalence of T. gondii, FIV, FeLV, and D. immitis was 19.34, 9.12, 11.33, and 3.04 %, respectively. For the genetic characterization of T. gondii genotypes in cats, genomic DNA was extracted from the seropositive cats and the T. gondii B1 gene was amplified using a semi-nested PCR. DNA samples giving positive B1 amplification were then genotyped using multilocus PCR-RFLP. Two T. gondii genotypes (ToxoDB#9 and ToxoDB#1) were identified. Results of the multivariate logistic regression analysis showed that older cats are more likely to be seropositive than juveniles for T. gondii, FIV, FeLV, and D. immitis. This is the first report of T. gondii genotypes in cats in northwest China. Moreover, the present study is the first study of retrovirus and D. immitis seroprevalence in cats in China. The results revealed that T. gondii, FIV, and FeLV infections are common in stray and pet cats in northwest China.

Diversity of trends of viremia and T-cell markers in experimental acute feline immunodeficiency virus infection

OBJECTIVE

The early events of human immunodeficiency virus infection seem critical for progression toward disease and antiretroviral therapy initiation. We wanted to clarify some still unknown prognostic relationships between inoculum size and changes in various immunological and virological markers. Feline immunodeficiency virus infection could be a helpful model.

METHODS

Viremia and T-cell markers (number of CD4, CD8, CD8β(low)CD62L(neg) T-cells, CD4/CD8 ratio, and percentage of CD8β(low)CD62L(neg) cells among CD8 T-cells) were measured over 12 weeks in 102 cats infected with different feline immunodeficiency virus strains and doses. Viremia and T-cell markers trajectory groups were determined and the dose-response relationships between inoculum titres and trajectory groups investigated.

RESULTS

Cats given the same inoculum showed different patterns of changes in viremia and T-cell markers. A statistically significant positive dose-response relationship was observed between inoculum titre and i) viremia trajectory-groups (r = 0.80, p<0.01), ii) CD8β(low)CD62L(neg) cell-fraction trajectory-groups (r = 0.56, p<0.01). Significant correlations were also found between viremia and the CD4/CD8 ratio and between seven out of ten T-cell markers.

CONCLUSIONS

In cats, the infectious dose determines early kinetics of viremia and initial CD8+ T-cell activation. An expansion of the CD8β(low)CD62L(neg) T-cells might be an early predictor of progression toward disease. The same might be expected in humans but needs confirmation.

Early detection of neuropathophysiology using diffusion-weighted magnetic resonance imaging in asymptomatic cats with feline immunodeficiency viral infection

HIV infection results in a highly prevalent syndrome of cognitive and motor disorders designated as HIV-associated dementia (HAD). Neurologic dysfunction resembling HAD has been documented in cats infected with strain PPR of the feline immunodeficiency virus (FIV), whereas another highly pathogenic strain (C36) has not been known to cause neurologic signs. Animals experimentally infected with equivalent doses of FIV-C36 or FIV-PPR, and uninfected controls were evaluated by magnetic resonance diffusion-weighted imaging (DW-MRI) and spectroscopy (MRS) at 17.5-18 weeks post-infection, as part of a study of viral clade pathogenesis in FIV-infected cats. The goals of the MR imaging portion of the project were to determine whether this methodology was capable of detecting early neuropathophysiology in the absence of outward manifestation of neurological signs and to compare the MR imaging results for the two viral strains expected to have differing degrees of neurologic effects. We hypothesized that there would be increased diffusion, evidenced by the apparent diffusion coefficient as measured by DW-MRI, and altered metabolite ratios measured by MRS, in the brains of FIV-PPR-infected cats relative to C36-infected cats and uninfected controls. Increased apparent diffusion coefficients were seen in the white matter, gray matter, and basal ganglia of both the PPR and C36-infected (asymptomatic) cats. Thalamic MRS metabolite ratios did not differ between groups. The equivalently increased diffusion by DW-MRI suggests similar indirect neurotoxicity mechanisms for the two viral genotypes. DW-MRI is a sensitive tool to detect neuropathophysiological changes in vivo that could be useful during longitudinal studies of FIV.

Effect of chronic FIV infection, and efficacy of marbofloxacin treatment, on Mycoplasma haemofelis infection

The purpose of this study was to investigate the effect of chronic feline immunodeficiency virus (FIV) infection, and efficacy of marbofloxacin treatment, on Mycoplasma haemofelis infection. Six cats chronically infected with FIV-Glasgow8 (Group X) and six FIV-free cats (Group Y) were infected with M. haemofelis on Day 0 by intravenous blood inoculation. From Day 0 until Day 86 post-infection (pi), blood samples were collected for M. haemofelis and FIV provirus quantitative real-time PCR and haematology. Three of the six cats in each of Groups X and Y were randomly selected to receive marbofloxacin treatment (2 mg/kg PO q24 h) from Day 16 to 43 pi, with the remaining cats being untreated controls with no antibiotic treatment. The M. haemofelis copy numbers and haematological data were compared between Groups X and Y, and between marbofloxacin-treated and control cats using a Mann-Whitney U-test. M. haemofelis infection was associated with development of macrocytic hypochromic anaemia. In some cats, marked variation in M. haemofelis copy number over time (>100,000-fold difference within 48 h in some cats) and/or cycling of copy number was seen. No correlation was found between FIV provirus copy number and M. haemofelis copy number or haematological variables. No significant effect of chronic FIV infection on M. haemofelis copy number kinetics or haematological changes due to M. haemofelis infection was found, other than MCHC (P=0.03). Marbofloxacin treatment was associated with a significant decrease in M. haemofelis copy number (P=0.002), although consistent clearance of infection was not demonstrated. This study reveals the presence of marked fluctuations in M. haemofelis copy number kinetics in vivo and a significant response to marbofloxacin antibiotic treatment.

Leishmaniosis due toLeishmania infantumin a FIV and FeIV positive cat with a squamous cell carcinoma diagnosed with histological, serological and isoenzymatic methods

Leishmaniosis caused by Leishmania infantum is an endemic zoonosis present in the Mediterranean area. Canidae (dog and fox) constitute the main reservoir hosts for the parasite, whilst wild rodents or the cat can be carriers of the protozoan and are considered as secondary potential reservoirs. This paper describes a case of disseminated feline leishmaniosis with cutaneous (ulcerative), visceral (spleen and lymph nodes) and blood involvement in a FIV-FelV positive cat. The microscopic identification of the Leishmania infection was initially made on a skin biopsy of the temporal area, where a squamous cell carcinoma was diagnosed. The diagnosis of the disease was achieved by several serological techniques (ELISA, IFAT and Western-blot). The strain was obtained by blood culture, characterized by electrophoresis of isoenzymes and identified as Leishmania infantum zymodeme MON-1. Since the infection due to L. infantum is a zoonosis, the potential feline reservoir should be more investigated. Serological analysis by Western blot on domestic cats provides a useful tool. In veterinary practice, feline leishmaniosis should be systematically included in the differential diagnosis when compatible cutaneous lesions are present, especially in the endemic areas of canine leishmaniosis.

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.

Evidence for modulated immune response to Anaplasma phagocytophila sensu lato in cats with FIV-induced immunosuppression

Human granulocytic ehrlichiosis (HGE) is an emerging infectious disease in which some patients experience unusual opportunistic infections. In this study, cats infected with the HGE agent, Anaplasma phagocytophila s.l., had clinical granulocytic ehrlichiosis (GE), anti-nuclear antibodies and increased IFN-gamma mRNA. In FIV-immunosuppressed cats with GE, there was upregulated IL-10 transcription but not IFN-gamma. Cats with FIV had poor response to vaccines, regardless of GE status. This preliminary report demonstrates that cats with FIV-infection make a good model of ehrlichiosis in an immunocompromised host, and that viral immunosuppression may not increase the severity of ehrlichiosis but may attenuate immune responses to the pathogen.

Retrospective study of 46 cases of feline haemobartonellosis in Israel and their relationships with FeLV and FIV infections

Forty-six cats with clinical haemobartonellosis were studied; 75 per cent of the cats of known age were two-and-a-half years old or younger, 50 per cent were intact males and 19.5 per cent were castrated males. The predominant signs of the disease were tachypnoea, lethargy, depression, anorexia, infestation with fleas, pale mucous membranes, icterus, emaciation, dehydration, splenomegaly, anaemia, leucocytosis, increased activities of alanine aminotransferase and aspartate aminotransferase, and azotaemia. Thirty-eight per cent of the cats that were tested for feline leukaemia virus (FeLV) antigen were positive, and 22 per cent of those tested for feline immunodeficiency virus (FIV) antibodies were positive. The prevalence of both FeLV and FIV was much higher than in the general Israeli cat population. The cats infected with both Haemobartonella felis and FeLV had a significantly lower body temperature, were more anaemic and the mean cell volume of their erythrocytes was greater than in the cats with haemobartonellosis alone.

Unique susceptibility of the fetal thymus to feline immunodeficiency virus infection: an animal model for HIV infection in utero

PROBLEM

Human infants infected in utero with HIV develop thymus insufficiency and progress to AIDS sooner than infants infected peripartum. However, direct analysis of the thymus is difficult due to limited tissue access and variable timing of vertical transmission.

METHOD OF STUDY

Fetal and neonatal cats were inoculated with feline immunodeficiency virus (FIV) at an equivalent infectious dose. The thymus, blood, and lymph nodes were harvested and compared at 23 and 46 days post-inoculation (p.i.) and also compared to sham-inoculated, age-matched controls. Lymphocyte phenotypes were analyzed by flow cytometry and virus burden was quantified in histologic sections and by virus isolation from plasma.

RESULTS

Fetal cats inoculated with FIV had acute thymus atrophy at birth, which coincided with peak viremia. At 46 days p.i., thymus size and cell composition rebounded and supported increased productive infection. In contrast, neonatal cats inoculated with FIV developed chronic thymus atrophy and degeneration, which was associated with decreasing productive infection and low-level viremia.

CONCLUSIONS

The fetal thymus is uniquely vulnerable to acute, transient depletion and high-level productive infection. The neonatal thymus is less vulnerable to acute changes, and responds through progressive atrophy and declining productive infection. Reduced immune competence, as reflected by the failure to control virus replication, may contribute to the accelerated progression of FIV and HIV infections in utero.

Methamphetamine and HIV-1: potential interactions and the use of the FIV/cat model

The interaction of methamphetamine with human immunodeficiency virus (HIV), the aetiologic agent of Acquired Immune Deficiency Syndrome (AIDS), has not been thoroughly investigated. However, increasingly, a larger proportion of HIV infected individuals acquire the virus through methamphetamine use or are exposed to this drug during their disease course. In certain populations, there is a convergence of methamphetamine use and HIV-1 infection; yet our understanding of the potential effects that simultaneous exposure to these two agents have on disease progression is extremely limited. Studying the interactions between methamphetamine and lentivirus in people is difficult. To thoroughly understand methamphetamine's effects on lentivirus disease progression, an animal model that is both clinically relevant and easily manipulated is essential. In this report, we identified potential problems with methamphetamine abuse in individuals with a concurrent HIV-1 infection, described the Feline Immunodeficiency Virus (FIV)/cat model for HIV-1, and reported our early findings using this modelling system to study the interaction of methamphetamine and lentivirus infections.

Fungal flora on cutaneous and mucosal surfaces of cats infected with feline immunodeficiency virus or feline leukemia virus

OBJECTIVE

To compare cutaneous and mucosal mycoflora in cats infected with FIV or FeLV with that in noninfected cats.

ANIMALS

85 client-owned cats; 24 seropositive for FIV, 10 seropositive for FeLV, 1 seropositive for both viruses, and 50 seronegative for both viruses.

PROCEDURE

Cutaneous specimens were obtained from the coat and external acoustic meatus (ear canal) and mucosal specimens from the oropharynx and rectum. Fungi were isolated from specimens, using Sabouraud dextrose agar incubated at 27 or 37 C for cutaneous and mucosal specimens, respectively.

RESULTS

Fungal colonies were cultured from at least 1 specimen from 83 of 85 (97.6%) cats. The most common fungal isolates were Aspergillus spp (cultured from 59.3% of all specimens), Penicillium spp (50.0%), Cladosporium spp (44.2%), Scopulariopsis spp (41.8%), and lipophilic yeasts of the genus Malassezia (31.4%). A greater diversity of fungal genera was isolated from retrovirus-infected cats, and Malassezia spp were more commonly recovered from these cats, compared with noninfected cats. Candida albicans, Cryptococcus neoformans, and dermatophytes (eg, Microsporum canis) were rarely isolated from any cat. Significant differences in frequency of isolation of C. neoformans and dermatophytes were not found between infected and noninfected cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Cats infected with FIV or FeLV may have a greater diversity of cutaneous and mucosal mycoflora than noninfected cats. However, infected cats may be no more likely than noninfected cats to expose humans to zoonotic fungi such as C. albicans, C. neoformans, and M. canis.

HIV-1-infection in the CNS. A pathogenesis of some neurological syndromes in the light of recent investigations

The main factors in the pathogenesis of AIDS-dementia complex (ADC) are analyzed. The author suggests that these factors can be divided into two groups. The "nonspecific" factors present in every immunologic processes manifested by inflammation compose the first group. They are cytotoxic lymphocytes T, the immunoactivation of infected macrophages, cytokines, NO, NOS and iNOS, the increase of the BBB permeability, the accumulation of beta-amyloid precursor protein, excitotoxic amino acids, various and numerous cells adhesion molecules. The second group may contain factors connected with HIV-1 infection of CNS. In the pathogenesis of AIDS an important role is played by toxic glycoproteins gp 120 and gp 41 which are in the coat of HIV-1 virus, nucleotide sequences variability, possibility of various virus replication in various parts of CNS, the participation of lymphokines IL-4 and IL-10, and presence of co-receptors to HIV-1 virus on lymphocytes, macrophages, neurons and microglial cells.

Feline immunodeficiency virus (FIV) infection leads to increased incidence of feline odontoclastic resorptive lesions (FORL)

Feline odontoclastic resorptive lesions (FORL), previously known as 'neck lesions,' are commonly known in domestic, but also in non-domestic cats. They are characterized by odontoclastic resorptive processes, which take place at the dental root and at the periodontium. Chronic inflammation of gingiva and periodontium is believed to be an important etiological factor in the development of FORL. In this context, various feline viruses have been discussed to play a relevant role in the pathogenesis of these lesions. The aim of this project was to determine in a blinded study the incidence of FORL in 10 cats which were infected for several years with feline immunodeficiency virus (FIV), but were otherwise free of feline viral infections (feline leukemia virus, feline calicivirus, feline herpesvirus, feline parvovirus, feline coronavirus, feline syncytium-forming virus). Nine age-matched controls were kept under identical conditions, but free of FIV. Subgingival resorptive lesions were found in six of 10 FIV-positive cats, but in three of nine controls only. FIV-positive cats had significantly more often gingivae with an increased tendency for bleeding upon probing than FIV-negative cats (p=0.0055), and they had slightly more often hyperplastic gingivae (p=0.0867). In conclusion, signs characteristic of FORL such as subgingival lesions, granulomatous or hyperplastic gingivae with a tendency for bleeding, were found significantly more often in FIV-positive cats than in the controls (p=0.0198). Therefore, it was concluded that FIV infection is an important factor for the occurrence of FORL, possibly through immune suppression or changes of the (sub)gingival micro-environment. However, non-infected control cats also showed some evidence of FORL in the absence of all tested viral infections. Therefore, factors other than viral infections must also play a role in the development of FORL in cats.

Progressive encephalopathy associated with CD4/CD8 inversion in adult FIV-infected cats

Experimental intravenous challenge of five adult cats with the feline immunodeficiency virus Maryland isolate (FIV-MD) was investigated for its ability to induce neurologic abnormalities associated with the onset of immunodeficiency. Five 8-month-old cats were inoculated with 1000 median tissue culture infective dose of FIV-MD isolate, with five age-matched cats serving as uninfected controls. All FIV-MD-infected cats tested positive for serum antiviral antibodies and plasma viral DNA as detected by polymerase chain reaction at 2, 4, 10, and 16 months postinfection (PI). At 10 and 16 months PI, there was a significant reduction in the CD4/CD8 lymphocyte ratio, with all cats having a CD4/CD8 ratio of 1 or less. Total protein electrophoretic analysis of cerebrospinal fluid demonstrated a significantly increased albumin quotient at 4 and 16 months PI, representing a disrupted blood-brain barrier (BBB). At 16 months PI, all cats demonstrated a preferential increase in frontal cortical slow-wave activity compared with control cats. Serial evaluation of brainstem auditory evoked potential recordings revealed a prolongation of the interpeak latencies times over the study time. At least one abnormality was found over time in visual and somatosensory evoked potential testing in three and four infected cats, respectively. Comparing lymphocyte subtype ratios with neurologic testing revealed that every FIV-MD-infected cat exhibited an abnormality in at least one neurologic functional test with a concurrent CD4/CD8 count ratio of 1 or less. Overall, this study demonstrated that FIV-MD infection in adult cats results in a delayed-onset, progressive encephalopathy that parallels the decline in the CD4/CD8 lymphocyte ratio. Compared with prior information from pediatric FIV-MD-infected cats, these results indicate that age of infection influences the onset and severity of disease and may be associated with CD4 cell depletion in FIV-MD-infected cats, as seen in HIV-1-infected humans.

Retrospective study of 60 cases of feline lymphosarcoma

OBJECTIVE

To characterise epidemiological and clinical findings, and diagnostic procedures undertaken, in cats with lymphosarcoma at a veterinary teaching hospital.

DESIGN

Retrospective case study.

PROCEDURE

Hospital records were reviewed for 7159 cats, sick or healthy, examined during a 10-year period (1984 to 1994). Sixty cats with lymphosarcoma were identified and classified by anatomical location of the tumor. Data on breed, age, sex, clinical signs and diagnostic procedures were collated.

RESULTS

The prevalence of feline lymphosarcoma in the hospital population was 0.84%. Siamese cats appeared predisposed to lymphosarcoma but other purebreds were not. Males were somewhat overrepresented amongst affected cats. Similar numbers of cases (12 to 18) were seen in each of the four anatomic categories (multicentric, mediastinal, alimentary and extranodal). Cats with mediastinal lymphosarcoma were mostly young and Siamese. Clinical signs in affected cats were varied, usually multiple and often nonspecific. Two of 22 cases tested positive for feline leukaemia virus antigen in blood and 6 of 13 were positive for feline immunodeficiency virus antibody.

CONCLUSIONS

Extranodal lymphosarcoma seemed more prevalent in this study than reported elsewhere. Siamese cats in the study population may have had a genetic predisposition to lymphosarcoma. Limited evidence suggested feline leukaemia virus may be less important, and feline immunodeficiency virus more important, in the local population than indicated in overseas reports. Additional studies are needed to investigate breed predisposition and feline leukaemia virus and feline immunodeficiency virus status in Australian cats with lymphosarcoma.

Interstitial lung disease in feline immunodeficiency virus (FIV) infected cats

Postmortem bronchoalveolar lavage of feline immunodeficiency virus-infected cats indicated an alveolitis process, and histological examination of their lungs confirmed the occurrence of alveolitis, parenchymatous lymphoplasmocytic infiltration and myomatosis. Similar lymphoid interstitial pneumonitis has been described in human and animal lentiviral diseases: lymphocytic interstitial pneumonitis in HIV-1-infected human beings, and maedi in sheep infected by the maedi-visna virus. Such lymphoid interstitial pneumonitis may thus be a common feature of lentiviral infections.

Cytologic identification of Toxoplasma gondii in bronchoalveolar lavage fluid of experimentally infected cats

OBJECTIVE

To determine whether it was possible to retrieve organisms, by means of bronchoalveolar lavage (BAL), from cats inoculated with Toxoplasma gondii.

DESIGN

Experimental study.

ANIMALS

27 cats. Sixteen of the 27 were experimentally infected with feline immunodeficiency virus.

PROCEDURE

All cats were inoculated with T gondii tachyzoites. Cats were grouped on the basis of feline immunodeficiency virus status and route (IV or intra-arterial) and number of tachyzoites administered. Bronchoalveolar lavage was performed by means of a standard technique. Lavage fluid was evaluated cytologically for tachyzoites.

RESULTS

Clinical signs of toxoplasmosis varied widely among individual cats, but were generally most pronounced in group-1 and -2 cats (n = 5 each) and less pronounced in group-3 (n = 5) cats. Group-4 and -5 cats (n = 6 each) did not have clinical signs of toxoplasmosis. In 14 of the 15 cats in groups 1, 2, and 3, tachyzoites were detected in BAL fluid collected 7 days after inoculation. Tachyzoites were detected 14 days after inoculation in the single cat without tachyzoites 7 days after inoculation. A necropsy was performed on 9 of these cats, and tachyzoites were identified histologically in 4 of the 9. Tachyzoites were not detected in BAL fluid collected 3 days (n = 6) or 7 days (n = 6) after inoculation from the 12 cats in groups 4 and 5. Tachyzoites were not identified histologically in any of these 12 cats.

CLINICAL IMPLICATIONS

BAL may be useful in the diagnosis of toxoplasmosis, particularly in cats with signs of pulmonary involvement.

Two related strains of feline infectious peritonitis virus isolated from immunocompromised cats infected with a feline enteric coronavirus

Two groups of cats were experimentally infected orally with the cat-passaged RM strain of feline enteric coronavirus (FECV-RM). One group of cats (n = 19) had been chronically infected with feline immunodeficiency virus (FIV) for over 6 years, while a second control group (n = 20) consisted of FIV-naive siblings. Fecal virus shedding of FECV occurred in both groups starting on day 3 postinfection, nearly ceased by 4 weeks in FIV-uninfected cats, but remained at high levels in FIV-infected animals. FIV-infected cats shed virus for a longer period of time and at levels 10 to 100 times greater than those for FIV-uninfected cats. The coronavirus antibody response of the FIV-infected cats was delayed and of reduced titer compared with that of the FIV-uninfected animals. Cats in both groups remained asymptomatic for the first two months following FECV-RM infection; however, 8 to 10 weeks postinfection two cats in the FIV-infected group developed feline infectious peritonitis (FIP). The FIP viruses (designated FIPV-UCD9 and -UCD10) isolated from these two cats had almost complete genetic homology to each other and to the infecting FECV-RM. However, unlike FECV-RM, they readily induced FIP when inoculated intraperitoneally into specific-pathogen-free cats. This study confirms that FIPVs are frequently and rapidly arising mutants of FECV. Immunosuppression caused by chronic FIV infection may have enhanced the creation and selection of FIPV mutants by increasing the rate of FECV replication in the bowel and inhibiting the host's ability to combat the mutant viruses once they occurred.

Encephalitis associated with giant cells in a cat with naturally occurring feline immunodeficiency virus infection demonstrated by in situ hybridization

This report describes the clinical, pathological, immunocytochemical, and in situ hybridization characteristics of encephalitis associated with feline immunodeficiency virus (FIV) infection in a 4-year-old domestic cat. Lesions were identified throughout the brain, affecting the cerebrum, medulla, and cervical spinal cord. Perivascular lymphocytic cuffing, gliosis, and white matter vacuolation were most severe in the cerebrum, affecting the white matter and the deep laminae of the grey matter. Gemistocytes were prominent, and many bizarre cells with large, sometimes multinucleate, hyperchromatic nuclei were evident. Immunostaining with antibody specific for FIV p24 nucleocapsid protein produced staining in the gemistocytes and glial cells of the white matter. In situ hybridization with a 327-base pair fragment of the FIV gag gene produced staining that was most intense in the white matter and gemistocytes of the deep laminae of the grey matter. These findings indicated localization of FIV infection within the cerebrum, and the detection of FIV RNA by in situ hybridization confirms the infection as active.

Primary and secondary Toxoplasma gondii infection in normal and feline immunodeficiency virus-infected cats

Normal and asymptomatic feline immunodeficiency virus (FIV)-infected adult cats were inoculated orally with Toxoplasma gondii tissue cysts to assess differences in clinical disease, T. gondii serologic test results, hematologic results, and oocyst shedding. There was no difference between FIV-naive and FIV-infected cats in terms of clinical illness and duration of oocyst shedding following primary exposure. Both groups of cats developed significant decreases in neutrophil counts following primary inoculation with T. gondii; FIV-infected cats that were neutropenic prior to inoculation with T. gondii developed the most profound decreases in neutrophil numbers. Both FIV-naive and FIV-infected cats became lymphopenic during acute T. gondii infection; however, only FIV-naive cats developed lymphocytosis in the recovery stage. FIV-infected cats had lower total CD4+ and higher total CD8+ T-lymphocyte counts than FIV-naive cats prior to inoculation with T. gondii, but changes in these lymphocyte subsets were similar between groups of cats during the first several weeks after inoculation. Toxoplasma gondii infection had neither an ameliorating nor enhancing effect on T-lymphocyte subset abnormalities in FIV-infected cats during acute or chronic infection. Both groups of cats developed comparable levels of T. gondii-specific IgM and IgG antibodies and T. gondii antigen-specific lymphocyte blastogenic responses following primary inoculation. Both groups of cats were fed T. gondii tissue cysts 66 wk following primary exposure and both groups were solidly immune as evidenced by a lack of oocyst shedding and only minor changes in IgM but not IgG antibodies.

Oral administration of bovine lactoferrin for treatment of intractable stomatitis in feline immunodeficiency virus (FIV)-positive and FIV-negative cats

OBJECTIVE

To study the effects of oral administration of bovine lactoferrin (LF) on intractable stomatitis in feline immunodeficiency virus (FIV)-positive and FIV-negative cats, and phagocytosis of neutrophils in healthy and ill cats, simultaneously.

ANIMALS

7 ill cats with diagnosis of intractable stomatitis (4 FIV positive and 3 FIV negative) and 7 healthy, FIV-negative cats.

PROCEDURE

LF (40 mg/kg ot body weight) was applied topically to the oral mucosa of cats with intractable stomatitis daily for 14 days and improvement of clinical signs of disease (pain-related response, salivation, appetite, and oral inflammation), expressed by scoring from 1 to 4, were evaluated. Assay of neutrophil phagocytosis was examined before and 2 weeks after starting LF treatment, using nonopsonized hydrophilic polymer particles (2 microns).

RESULTS

Oral administration of LF improved intractable stomatitis in all 4 respects. Phagocytic activity of neutrophils increased after LF treatment. This effect was observed in healthy and ill (FIV positive and FIV negative) cats.

CONCLUSION AND CLINICAL RELEVANCE

Oral administration of LF improved intractable stomatitis and concurrently enhanced the host defense system. Topical application of LF to oral mucous membrane is useful as a treatment for intractable stomatitis even in FIV-positive cats.

Does coinfection of Bartonella henselae and FIV induce clinical disorders in cats?

It was found that Bartonella henselae (B. henselae) may induce clinical disorders in cats in natural conditions from a comparison of the serological status for B. henselae with the serostatus for feline immunodeficiency virus (FIV) and several clinical characteristics in 170 domestic cats. Seropositivity for B. henselae was not significantly different between FIV antibody-positive and -negative cats (18.4% vs 16.0%). The incidence of clinical characteristics were compared among four cat groups distinguished by the reactivity of sera against B. henselae and FIV. The incidence of lymph node swelling was lower in only FIV antibody-positive cats (3.0%), but higher in B. henselae antibody-positive cats (13.6%) and significantly higher in both B. henselae and FIV antibody-positive cats (42.9%) compared with the incidence of lymph node swelling in cats which were negative for both antibodies (5.5%). The same relation was also observed for the incidence of gingivitis among the 4 cat groups, suggesting that coinfection of B. henselae and FIV may be associated with gingivitis and lymphadenopathy in cats.

Molecularly cloned feline immunodeficiency virus NCSU1 JSY3 induces immunodeficiency in specific-pathogen-free cats

A full-length feline immunodeficiency virus NCSU1 (FIV-NCSU1) genome (JSY3) was cloned directly from FIV-NCSU1-infected feline CD4+ lymphocyte (FCD4E) genomic DNA and identified by PCR amplification with 5' long terminal repeat, gag, env, and 3' long terminal repeat primer sets. Supernatant from FCD4E cells cocultured with JSY3-transfected Crandell feline kidney (CrFK) cells was used as an inoculum. Cell-free JSY3 virus was cytopathogenic for FCD4E lymphocytes but did not infect CrFK cells in vitro. To determine in vivo infectivity and pathogenesis, six young adult specific-pathogen-free cats were inoculated with cell-free JSY3 virus. Provirus was detected at 2 weeks postinfection (p.i.) and was still detectable at 25 weeks p.i. as determined by gag region PCR-Southern blot analysis of peripheral blood mononuclear cell lysates. Infectious virus was recovered from peripheral blood mononuclear cells at 6 and 25 weeks p.i., and an antibody response to FIV was detected by 4 weeks. In the acute phase of infection, JSY3 provirus was found only in the CD4+ lymphocyte subset; however, by 14 weeks p.i., the greatest provirus burden was detected in B lymphocytes. All six cats were panlymphopenic at 2 weeks p.i., CD4+/CD8+ ratios were inverted by 6 weeks p.i., and five of the six cats developed lymphadenopathy by 10 weeks p.i. To determine if the JSY3 molecular clone caused immunodeficiency similar to that of the parental wild-type FIV-NCSU1, the cats were challenged with the low-virulence ME49 strain of Toxoplasma gondii at 29 weeks p.i. Five of six cats developed clinical signs consistent with generalized toxoplasmosis, and three of six cats developed acute respiratory distress and required euthanasia. Histopathologic examination of the severely affected cats revealed generalized inflammatory reactions and the presence of T. gondii tachyzoites in multiple tissues. None of the six age- and sex-matched specific-pathogen-free cats inoculated with only T. gondii developed clinical disease. Our results suggest that the pathogenesis of the molecularly cloned NCSU1 JSY3 is similar to that of wild-type FIV-NCSU1.

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

Lymphosarcoma (malignant lymphoma) is the commonest hematopoietic tumor in the cat. Many cases are associated with feline leukemia virus (FeLV) infection, but epidemiologic and experimental data suggest that feline immunodeficiency virus (FIV) may also have a role in lymphomagenesis. In this paper, we describe the clinical presentation, histologic classification, and immunophenotype of lymphosarcoma in eight domestic cats with natural or experimental FIV infections. The tumors were often of unusual distribution, with the majority of cases conforming to the least common anatomic classification of "miscellaneous." Histopathologic and immunophenotypic analysis using a panel of anti-cat and cross-reactive anti-human monoclonal and polyclonal antibodies identified seven of these tumors as high-grade B cell lymphomas of the centroblastic or immunoblastic subtypes. The remaining case was a T-cell tumor associated with a concurrent FeLV infection. Our findings, together with the results of an analysis of FIV proviral DNA in these tumors, indicate that the B-cell lymphosarcomas were comparable to those observed in human and simian immunodeficiency virus infections and that the role of FIV in lymphomagenesis is indirect and related to the potential for malignant transformation during polyclonal B cell activation.

Opportunistic infections associated with retroviral infections in cats

Naturally occurring infection of cats with feline leukemia virus and feline immunodeficiency virus is common. A wide variety of clinical manifestations occur in retrovirus-infected cats including gastrointestinal tract disease, respiratory tract disease, central nervous system disease, ophthalmic disease, hepatic disease, urogenital tract disease, dermatologic disease, hematologic disease, and musculoskeletal disease. Clinical signs are often directly attributable to the primary viral infection, but because both feline leukemia virus and feline immunodeficiency virus can induce immunodeficiency, opportunistic secondary infections may cause the clinical manifestations of disease in some cats. Diagnosis, treatment, and zoonotic potential of the common opportunistic agents associated with feline retroviral infections are reviewed.

Hematologic abnormalities associated with retroviral infections in the cat

Feline patients with unexplained peripheral blood cytopenias, circulating immature or neoplastic cells, dysplastic or dysmorphic bone marrow abnormalities, and/or lymphoid tumors are likely suffering from an underlying retroviral infection with feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV). Cytopenic hematologic disorders are often caused by the direct or indirect hematosuppressive effects of these retroviruses. Alternatively, secondary infections, nutritional deficiencies, and/or hematopoietic neoplasms may be important cofactors in the development of blood and bone marrow abnormalities in retrovirus-positive patients. Mild to moderate nonregenerative anemia, with or without concurrent granulocytopenia and/or thrombocytopenia, is one of the most frequent hematologic disorders encountered with either infectious agent. Severe, isolated anemia with absent reticulocytes (pure red blood cell aplasia) specifically suggests infection with FeLV subgroup C. Hemolytic (regenerative) anemia, more commonly associated with FeLV infection, may be caused by an autoimmune process and/or coinfection with Haemobartonella felis. Lymphopenia is a hallmark of chronic, symptomatic FIV infection. Neutropenia may accompany a panleukopenia-like syndrome in FeLV-positive cats or it may be associated with acute primary infection or an adverse drug effect in the FIV-infected patient. FeLV and, to a lesser extent, FIV are both causally related to lymphoid neoplasms in domestic cats, but with dissimilar epidemiologic, clinical, and host cell phenotypic features. Clinicians must be cognizant of the wide spectrum of hematologic manifestations of FeLV and FIV infections to recognize and appropriately manage these complications in their feline patients.

Vertical transmission of feline immunodeficiency virus

We studied vertical transmission of feline immunodeficiency virus (FIV) to determine whether it might provide a model with which to study intervention strategies for mother-to-offspring transmission of human immunodeficiency virus (HIV). We found that pregnant cats acutely infected with FIV (FIV-CSU-2771) transmitted the virus to their offspring via both prenatal and postnatal routes. In utero transmission led to several pathogenic consequences including arrested fetal development, abortion, stillbirth, subnormal birth weights, and birth of viable, virus-infected, and asymptomatic but T cell-deficient kittens. Postnatal milk-borne FIV transmission was demonstrated by the presence of cell-free and cell-associated virus in colostrum and milk and through a foster-nursing experiment. The potential for intrapartum FIV transmission was documented by frequent virus isolation from vaginal wash cells in both the pre- and postpartum periods. FIV transmission was efficient during acute maternal infection, leading to an overall infection rate of 70%. We conclude that FIV vertical transmission may be a useful model with which to evaluate intervention strategies for HIV transmission from mother to child.

Long-term renal and hematologic effects of uninephrectomy in healthy feline kidney donors

To assess long-term hematologic and renal effects associated with a solitary kidney, 16 healthy cats undergoing uninephrectomy for kidney donation between May 1987 and January 1991 were evaluated by use of physical examination, CBC, serum biochemical analysis, urinalysis, and urine protein:creatinine ratio. Results of preoperative CBC, serum biochemical analysis, and urinalysis were within reference limits in all donors. Median age at surgery and at follow-up evaluation was 34 and 72 months, respectively. Mean (+/- SEM) interval between follow-up and uninephrectomy was 39.3 +/- 14.6 months. Postuninephrectomy hematocrit and RBC indices were within reference limits in 15 donors. One cat with chronic renal insufficiency had normocytic, normochromic, nonregenerative anemia. In 15 clinically normal donor cats, mean (+/- SEM) serum creatinine concentrations pre- and post-uninephrectomy were 1.36 +/- 0.20 and 1.71 +/- 0.33 mg/dl, respectively (P = 0.0002); however, the clinical relevance of this statistical difference in serum creatinine is uncertain, because all values were within reference limits. In addition, urine-concentrating ability was maintained in 14 donors, with urine specific gravity > or = 1.040. Two donors, including the cat with chronic renal insufficiency, produced dilute urine (specific gravity < or = 1.020) and had substantial proteinuria, with urine protein:creatinine ratios of 2.16 and 3.62, respectively. Mean urine protein:creatinine ratio in donor cats was not significantly different from that in an age- and sex-matched comparison group. Renal and erythropoetic function was clinically preserved in the group of donor cats within 2 to 5 years after uninephrectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

[Findings in the eyes of serologically FIV (feline immunodeficiency virus) positive cats]

The findings in the eyes of 19 serologically FIV-positive cats in the terminal stage of the disease were compared to those in 23 serologically FIV-negative cats. An inflammation of iris and ciliary body was more common in the FIV-group than in the other cats and could be seen in 16 out of 19 serologically FIV-positive cats. In most cases a diffuse infiltration of both lymphocytes and plasma cells could be observed. There were only few signs of acute inflammation in the posterior segment. Degenerative alterations of the retina were found in all groups. The most common degenerative finding was a cystoid atrophy of the retina. Due to these findings an association of FIV-infection and anterior uveitis seems to be very likely. It remained unclear whether the FIV was involved directly or whether indirect mechanisms like secondary infections or alterations in the immune system caused the inflammation.

Circulating immune complexes and analysis of renal immune deposits in feline immunodeficiency virus-infected cats

Total immunoglobulin content and concentration of immune complexes (IC) were determined in the sera of 51 cats infected with feline immunodeficiency virus (FIV) and of 40 controls. IgG and IgM were quantified by radial immunodiffusion and circulating IC (CIC) by the CIC-conglutinin assay. IgG fractions were obtained by acid elution from kidney tissues of 15 FIV-infected and five negative control cats to investigate the possible role of IC in the genesis of renal damage observed in infected animals. Mean concentrations of IgG and circulating IC were higher in FIV-infected cats than in controls (29.6 +/- 6.7 versus 23.0 +/- 1.9 mg/dl (mean +/- s.d.) P < 0.001; and 66.5 +/- 17.0 versus 27.4 +/- 19.9% I, P < 0.001, respectively), while IgM levels were only slightly increased (0.9 +/- 0.05 versus 0.87 +/- 0.04 mg/dl, P < 0.02). Immunoglobulin fractions were eluted from 10 of the 15 renal tissue samples from FIV-infected cats and were found to be polyclonal and at least partly specific for FIV antigens. These findings confirm the presence of a B cell activation in FIV-infected cats and demonstrate the presence of high levels of CIC in their sera. The presence of immune deposits in renal tissues suggests that IC might play a role in the pathogenesis of the renal damage observed in FIV-infected cats.

Panleukopenia-like syndrome of FeLV caused by co-infection with FeLV and feline panleukopenia virus

To study the effect of interferon on feline leukemia virus (FeLV) infection, 30 specific pathogen free (SPF) cats were infected with the apathogenic FeLV A Glasgow. Unexpectedly, between 5 and 8 weeks after FeLV infection, all 19 cats with persistent FeLV infection but not the FeLV-negative cats died from a panleukopenia-like syndrome. No feline panleukopenia virus (FPLV) antigen was found in feces by latex agglutination, enzyme-linked immunosorbent assay (ELISA) or immunoelectron microscopy. No enteropathogenic bacteria were found. Histopathology revealed changes resembling those of FPLV infection such as destruction of crypts and pancytopenia of bone marrow. Neither clinical signs nor seroconversion to FPLV could be induced by transmitting intestinal extracts to two SPF cats. However, FPLV antigen was demonstrated by immunofluorescence assay in intestinal cryostat sections of diseased animals. FPLV could also be demonstrated in intestinal extracts by immunoelectron microscopy, by latex agglutination and ELISA after anti-FPLV antibodies were removed from immune-complexed FPLV by ultracentrifugation over a CsCl gradient at pH 2.0. From these experiments it was concluded that the panleukopenia-like syndrome of FeLV may not be caused by FeLV alone but at least in some cases by co-infection with FeLV and FPLV. In addition, some form of 'cooperation' between FeLV and FPLV must be postulated because neither virus alone induced symptoms.

Cryptococcosis in a cat seropositive for feline immunodeficiency virus

A 5-year-old female Siamese cat was presented to the veterinary teaching hospital with a history of bronchopneumonia for 20 days. The cat had not responded to antibacterial chemotherapy and had developed a pronounced submandibular lymphadenopathy. Characteristically encapsulated yeast cells with narrow-necked buds were clearly seen in a fine-needle aspirate of the lymph node with an India ink preparation. Cryptococcus neoformans var. neoformans was identified. Susceptibility tests on the isolated strain were performed using antifungal tablets. The strain was sensitive to amphotericin B, fluconazole, itraconazole and ketoconazole and was resistant to 5-fluorocytosine. The cat was positive for feline immunodeficiency virus. Nevertheless, the cat was treated with ketoconazole for 3 months and apparently recovered. Three months later the animal was presented in a precomatose state. The owners refused to treat the animal and the cat was destroyed.

Analysis of leucocytes and lymphocyte subsets in cats with naturally-occurring cryptococcosis but differing feline immunodeficiency virus status

Although cryptococcosis is a well-characterised disease of cats, the factors predisposing individuals to infection are unknown. As an indication of the immune status of an individual, lymphocyte subsets can be analysed. Reference ranges for feline lymphocyte subsets (Pan T+, CD4+, CD8+ and B cells) were established using a rapid whole blood technique and flow cytometry. There were no effects of age or sex on lymphocyte subset values. The numbers of circulating leucocytes and lymphocyte subsets were determined in FIV-positive and FIV-negative cats with cryptococcosis and compared with a group of healthy control cats. There were only minor differences in the numbers of lymphocyte subsets among the subgroups of cats examined in the study and the predisposition to cryptococcosis in cats could not be explained by deficiencies in lymphocyte subsets. There was a tendency for FIV-negative cats with cryptococcosis to have reduced numbers of circulating CD4+ cells and lower CD4:CD8 ratios compared with normal cats, although the interpretation of this finding was complicated by the wide reference range for normal cats. The extent to which this is the cause of the fungal infection was not determined. The only difference in leucocyte or lymphocytes subset values between FIV-negative cats with cryptococcosis and FIV-positive cats with cryptococcosis was that the CD4+ percentage was lower in the FIV-positive cats. The absolute CD4+ count was similar however, in FIV-positive and FIV-negative cryptococcosis cases. On the basis of this and other available information, the categorisation of cryptococcosis as a disease defining the AIDS phase of FIV infection may be incorrect.

Lentiviral infection, immune response peptides and sleep

The aberrant sleep documented in subjects with human immunodeficiency virus (HIV) infection is uniquely important because of the contribution this poor quality sleep makes to the fatigue, disability, and eventual unemployment that befalls these patients. Especially given this importance in clinical care, the research on the prominent sleep changes described in HIV infection remains modest in quantity. The chronic asymptomatic stage of HIV infection is associated with the most intriguing and singular sleep structure changes. Especially robust is the increase in slow wave sleep, particularly in latter portions of the sleep period. This finding is rare in other primary or secondary sleep disorders. The sleep structure alterations are among the most replicable of several pathophysiological sequelae in the brain associated with early HIV infection. It is unlikely that these sleep architecture changes are psychosocial in etiology, and they occur before medical pathology is evident. They are not associated with stress, anxiety, or depression. Evidence is accumulating to support a role for the somnogenic immune peptides tumor necrosis factor (TNF)alpha and interleukin (IL-1 beta) in the sleep changes and fatigue commonly seen in HIV infection. These peptides are elevated in the blood of HIV-infected individuals, and are somnogenic in clinical use and animal models. The peripheral production of these peptides may also have a role in the regulation of normal sleep physiology. The lentivirus family contains both HIV and the feline immunodeficiency virus (FIV). The use of the FIV model of HIV infection may provide a way to further investigate the mechanism of a neurotropic, neurotoxic virus initiating the immune acute phase response and affecting sleep. Neurotropic lentivirus infection is a microbiological probe facilitating neuroimmune investigation.

Lentivirus infection in an African lion: a clinical, pathologic and virologic study

In May 1991, clinical, pathologic, and virologic investigations were carried out on an 8-yr-old male lion (Panthera leo), with recurrent infections, in captivity with two lionesses in the Zoological Garden of Pistoia, Tuscany, Italy. The lion had severe pneumonia, neutropenia, thrombocytopenia, and an increase in blood urea nitrogen and creatininemia; in spite of therapy, it died within 3 months. At necropsy, the animal had a lymphoma and other lesions similar to those described in feline immunodeficiency virus-infected cats. We identified FIV gag-sequence using PCR amplification of lymph node tissues.

Effects of incidental infections and immune activation on disease progression in experimentally feline immunodeficiency virus-infected cats

Specific pathogen-free cats were experimentally infected with feline immunodeficiency virus (FIV) and subsequently exposed to common infectious pathogens and immune stimuli over a 3-year period. Cats with preexisting FIV infection showed signs of disease after exposure to Haemobartonella felis, Toxoplasma gondii, feline herpesvirus-1, and feline calicivirus similar to signs in non-FIV-infected cats, although they were more severe. No adverse effects of immunization with inactivated rabies virus vaccine and a synthetic polyproline immunogen were observed in either FIV-infected or non-FIV-infected cats, whereas the application of a diphtheria-tetanus-pertussis vaccine caused transient fever and lymphadenopathy in both groups of animals. Primary immune responses to pathogens or immunogens were usually delayed or diminished in FIV-infected compared with non-FIV-infected cats. Repeated infections and immune activation had no significant effects on the levels of FIV-specific antibodies or on the proportion of peripheral blood mononuclear cells (PBMCs) containing FIV proviral DNA. However, FIV-infected cats that were not exposed to immune stimuli had lower CD4+ T-lymphocyte numbers and lower CD4+/CD8+ T lymphocyte ratios at the end of the 3-year study than FIV-infected cats exposed to cofactors. The latter also had normal levels of interleukin-3 receptor (IL-2R) and major histocompatibility class II (MHC-II) antigen expression on PBMCs, while FIV-infected cats not exposed to cofactors had up-regulated IL-2R and down-regulated MHC-II antigen expression. It was concluded that repeated immune stimulation did not have a deleterious effect on the course of FIV-induced immunodeficiency.

Development of clinical disease in cats experimentally infected with feline immunodeficiency virus

Cats naturally infected with feline immunodeficiency virus (FIV) develop an AIDS-like syndrome whereas experimentally infected cats do not. To investigate the role of cofactors in the development of this disease in cats, 7 specific pathogen-free (SPF) and 12 random-source (RS) cats were infected with FIV. Over 4 years, infected cats developed similar phenotypic and functional immune abnormalities characterized by early and chronic inversion of CD4+:CD8+ cell ratios and significantly decreased mitogen responses compared with controls. Beginning 18-24 months after infection, 10 RS cats developed chronic clinical disease typical of feline AIDS, including stomatitis and recurrent upper respiratory disease; 4 SPF cats also developed chronic clinical disease, 2 with neurologic disease and 2 with B cell lymphomas. Thus, immunologic background is important in the type of disease that develops in cats infected with FIV, and FIV represents a promising animal model for studying the immunopathogenesis of AIDS in humans.

Evaluation of in vivo and in vitro interactions of feline immunodeficiency virus and feline leukemia virus

OBJECTIVE

To determine the potential mechanisms for disease potentiation where feline immunodeficiency virus (FIV) infection of persistently feline leukemia virus (FeLV)-infected cats results in more severe FIV disease and increased mortality than FIV infection of specific pathogen-free cats.

DESIGN AND METHODS

To determine whether pseudotype formation resulting in expanded cell tropism may be an important mechanism, cellular targets and tissue distribution of FIV and FeLV were determined by in situ hybridization and/or immunohistochemistry. To determine whether FeLV can transactivate the FIV long terminal repeat (LTR) resulting in increased FIV expression, in vitro transient expression assays were performed. To examine whether persistent FeLV infection can cause the deletion of a suppressive T-lymphocyte population, peripheral blood mononuclear cell (PBMC) cultures from persistently FeLV-infected cats were infected with FIV and monitored for FIV antigen levels.

RESULTS

Macrophages were the predominant target of FIV infection and were disseminated in a similar pattern in lymphoid and nonlymphoid tissues of both FIV-infected and FeLV/FIV-coinfected cats. FeLV-infected cells expressing FIV RNA were not present. Significant transactivation of the FIV LTR in FeLV-infected cells was not demonstrated. FIV antigen production was similar upon in vitro infection of PBMC from FeLV-infected and uninfected cats.

CONCLUSIONS

Neither direct virus/virus interactions, such as FeLV/FIV pseudotype formation or transactivation of the FIV LTR in FeLV-infected cells, nor deletion of a regulatory cell subset from the blood of FeLV-infected cats, was found to be the mechanism of disease potentiation.

Epidemiologic observations on infection with Rochalimaea species among cats living in Baltimore, Md

Cats from several sources in Baltimore, Md, were tested for seropositivity to Rochalimaea henselae and R quintana. Co-infection with Toxoplasma gondii or feline immunodeficiency virus was assessed as a risk factor for infection with Rochalimaea spp. Of 592 cats tested, 87 (14.7%) were seropositive for one or both Rochalimaea spp, although titers to R henselae were significantly higher than those to R quintana. Prevalence of seropositivity increased significantly with cat age and weight and was associated with seropositivity to T gondii but was not associated with gender. Prevalence of seropositivity was similar (12.5 to 14.4%) among groups of cats with some history of human contact but was higher among feral cats (44.4%). Whether cats are reservoirs or mechanical vectors of Rochalimaea spp that can cause diseases in people is still uncertain, but these findings indicated widespread infection of cats and suggested possible modes of transmission for Rochalimaea spp among cats.

Malignant lymphoma associated with experimentally induced feline immunodeficiency virus infection

A malignant low-grade B-cell lymphoma, primarily in the kidney, is described in a specific-pathogen-free cat experimentally infected with feline immunodeficiency virus (FIV) and free of feline leukaemia virus. At the time of diagnosis the cat showed a marked reduction of circulating CD4+ T lymphocytes, was 2 years old, and had been infected for 18 months. FIV was isolated both from peripheral blood mononuclear cells and the neoplastic tissue. DNA of FIV gag gene was detected in several specimens, including the neoplastic tissue. Even if they do not demonstrate a direct role for virus promotion of lymphomas, these and previous observations indicate that B-cell malignant lymphoma might be associated with FIV infection as reported for human and simian immunodeficiency virus infections.

Effect of chronic feline immunodeficiency virus infection on experimental feline calicivirus-induced disease

Acute feline calicivirus (FCV) infection caused a more severe disease in chronically feline immunodeficiency virus (FIV) infected than in non-FIV infected cats. FIV infected cats shed significantly higher amounts of FCV through their saliva after FCV challenge than the non-FIV infected cats. However, there was no difference in the duration of FCV shedding. None of the cats exposed to FCV developed chronic FCV carriage. Both groups of cats mounted similar titers of neutralizing antibodies to FCV. Although FIV infected cats started out with significantly lower total lymphocyte and neutrophil numbers than the non-FIV infected cats, the transient lymphopenia and neutrophilia attributable to the FCV infection was of similar intensity in both groups of animals. There was no evidence that the underlying FIV-related disease or viremia was influenced by acute FCV infection. Acute FCV infection did not significantly alter the CD4+/CD8+ T lymphocyte ratio in FIV infected compared to non-FIV infected cats. The ongoing humoral IgG response to FIV was not affected by the FCV infection. There was no significant change in the proportion of FIV infected peripheral blood mononuclear cells during 8 subsequent weeks after FCV challenge as determined by polymerase chain reaction.