Alteration of T-cell subsets in the lymph nodes from cats infected with feline immunodeficiency virus

Alterations of T-cell subsets in the lymph nodes from FIV-infected cats in various clinical disease stages were examined histologically. In the early stage of infection (AP stage), follicular hyperplasia accompanied by expansion of the paracortical area was observed. Follicular involution and depletion with reduced paracortical area was observed in the ARC and AIDS stage nodes. The maximum section area of the entire popliteal lymph node was expanded significantly in the AP nodes. The paracortical area expanded in the AP nodes and decreased in the ARC and AIDS stage nodes. The cell density in the paracortical area in the AP nodes did not show a significant increase, while there was a significant reduction in the ARC and AIDS stage nodes. The lymph node CD4/CD8 ratio in the AP and ARC stages significantly decreased as compared with that of uninfected control cats, but conversion of the ratio was not seen. The estimated total numbers of CD4+ and CD8+ cells in the maximum section were increased in the AP stage but significantly decreased in the ARC and AIDS stages. Our study indicated that the lymphocyte depletion in the terminal ARC and AIDS stages of FIV infection was associated with both CD4+ cells and CD8+ cells. Findings obtained in this study might provide useful information for studying the pathophysiology of FIV infection.

Spontaneous programmed cell death (PCD) process of lymphocytes of FIV-infected cats: cellular targets and modulation

Unstimulated lymphocytes from FIV-infected cats undergo spontaneous apoptosis in vitro as indicated by internucleosomal DNA fragmentation and hypodiploid DNA content of nuclei. Unlike what is reported in HIV-infected individuals, we observed that cell death of cat lymphocytes was inhibited by activation. Spontaneous apoptosis was reduced by the addition of cat serum and after activation by phorbol ester (PMA), superantigens (SEB, SEA), and to a lesser extent by mitogens such as concanavalin A and pokeweed mitogen. In contrast, apoptosis of lymphocytes from FIV-infected, but not from control cats was increased in the presence of calcium ionophore (ionomycin). Analysis of the phenotype of cells undergoing apoptosis revealed that cell death is not restricted to a cell subpopulation but involved all lymphocyte subsets. These data suggest that the mature lymphocytes of FIV-infected cats appear programmed to die by apoptosis unless rescued by specific agents, such as protein kinase C activators or mitogens.

Immunotherapy and cytokines

Immunomodulation is now possible in veterinary medicine with the licensure of a number of biological products by the United States Department of Agriculture for veterinary use. These products activate primarily macrophages, induce the production of cytokines, and have various effects on the activity and proliferation of B and T lymphocytes. Those products most commonly used are inactivated whole bacteria of Propionibacterium acnes, cell wall fractions of nonpathogenic Mycobacterium spp, and the lysate derived from lysis of Staphylococcus aureus by a bacterial phage. All products have been licensed for use against specific diseases, but the literature includes studies for off-label usage. These immunomodulators are considered to be nonspecific stimulators of the immune system and may affect both humoral and cellular functions of immunity.

Nutritional modification of inflammatory diseases

Regulation of the immune system is extremely complex. We are only starting to understand how the immune system coordinates the body's response to a disease or invading pathogen. Immunomodulation, as the term implies, can be used to designate either a suppression or an augmentation of an immune response. Suppressing the function of the immune system may be important in cases of inflammation and augmenting the immune response when increased resistance to disease is required. Nutrition does and can play an important role in modulation of the animal's immune system. The majority of scientific literature published on the interaction of nutrition and the immune system correlates the effects of nutrient deficiency and modulation of an immune response. These studies have evaluated deficiencies of protein; energy; the fat soluble vitamins A, D, and E; the B-complex vitamins; vitamin C; and the minerals selenium, iron, zinc, and copper and their relationship to immune dysfunction. Most recently, researchers have concentrated efforts on evaluating the impact specific fatty acids have on modulation of the immune system. Undoubtedly, the nutritional status of the animal plays an important role in resistance mechanisms against disease causing organisms and may influence the outcome of disease in infected animals. The focus of this chapter is to concentrate on the role specific polyunsaturated fatty acids have on the immune response of animals and to consider the potential for nutritional modification of diseases related to inflammation.

Elevated interleukin 6 activity in aqueous humor of cats with uveitis

The purpose of this study was to assess the role of interleukin 6 (IL-6) in feline uveitis by measuring IL-6 activity in the serum and aqueous humor of cats. Serum and aqueous humor was collected from clinically normal, random source cats (n = 10); clinically normal, specific-pathogen free cats experimentally inoculated with Toxoplasma gondii strain ME49 and sampled sequentially for 20 months (n = 4); and client-owned cats with uveitis (n = 27). Interleukin 6 activity was measured in each sample. Client-owned cats with uveitis were also evaluated for evidence of present or prior exposure to T. gondii, feline leukemia virus, feline immunodeficiency virus, and feline coronaviruses. Interleukin 6 activity was non-detectable or low in serum from cats of each group. Interleukin 6 activity was not detected in aqueous humor of clinically normal cats. Interleukin 6 activity was detected in 22/27 (81.5%) aqueous humor samples from cats with uveitis, with a range of 28.9 U ml(-1)-15702.9 U ml(-1) (mean = 1911.9 U ml[-1], SD = 3946.7 U ml[-1]). Serologic evidence of exposure to T gondii, feline immunodeficiency virus, feline leukemia virus, or a coronavirus was present in 21/27 (77.8%) cats with uveitis. Interleukin 6 was detected in the aqueous humor of 18/21 (85.7%) and 3/6 (50%) of the cats with and without serologic evidence of exposure to one to the infectious diseases, respectively. Statistically significant increases in mean IL-6 activity in aqueous humor were found for cats with any evidence of infection with T. gondii, for cats with T. gondii antigen in aqueous humor and for cats with coronavirus antibody titers > or = 1:100. Aqueous humor IL-6 activity was greater than corresponding serum IL-6 activity in 21/27 cats. These results show that IL-6 is produced intraocularly in some cats with uveitis and that IL-6 may be a mediator of uveitis in cats.

Feline heartworm (Dirofilaria immitis) infection: detection of specific IgG for the diagnosis of occult infections

Sera from 54 cats, 53 asymptomatic and one symptomatic (chronic dyspnoea and coughing), living in a hyper-endemic area for canine heartworm (Dirofilaria immitis) infection were studied to evaluate the reliability of two ELISA-based antibody tests coupled with both somatic (ELISASA) and excretory/secretory (ELISAE/S) antigens. All cats were examined by echocardiography and radiography. In addition, an ELISA-based test to detect adult female heartworm circulating antigens and a modified Knott test for microfilariae in the blood were carried out on all cats. No cat was positive for microfilariae in the blood. Heartworms were visualized in 12 of 54 cats by echocardiography. Of these, three asymptomatic cats and the symptomatic one had radiographic signs of infection and were the only ones positive for heartworm circulating antigens. All sera except two were positive when analyzed in ELISA(SA). In ELISA(E/S), nine sera were positive but three were negative. No sera from the 42 echocardiography-negative cats was positive in ELISA(E/S), but 11 were positive in ELISA(SA). Western blot analyses with somatic antigens of sera from echocardiography-positive cats showed at least four bands of recognition between 19 and 30 kDa and one of about 40 kDa. With E/S antigen, a large band of about 22 kDa and one of about 25 kDa were recognized; these appear to be most specific.

High feline trypsin-like immunoreactivity in a cat with pancreatitis and hepatic lipidosis

A 1.5-year-old domestic shorthair cat was examined because of vomiting and icterus. Clinicopathologic abnormalities included high alanine transaminase, alkaline phosphatase, and gamma-glutamyltransferase activities and high total bilirubin concentration. During abdominal ultrasonography, the left limb and body of the pancreas appeared hypoechoic, and a small quantity of peritoneal effusion was seen. The liver was diffusely hyperechoic, with echogenicity similar to that of the spleen, indicating hepatic lipidosis. Feline trypsin-like immunoreactivity was high, suggesting that the cat also had pancreatitis. The cat was treated with crystalloid fluids and was fed a protein-restricted diet via a percutaneous endoscopically placed gastrostomy tube. The cat's condition continued to deteriorate despite medical treatment, and it was euthanatized. Necropsy confirmed the clinical suspicion of acute pancreatitis and hepatic lipidosis. This case suggests that measurement of trypsin-like immunoreactivity may be useful in cats suspected of having pancreatitis.

Exposure of cats in southern Africa to Coxiella burnetii, the agent of Q fever

Recently, the domestic cat has been implicated in numerous outbreaks of Q fever in humans. To determine if cats in southern Africa are infected with the agent of Q fever we tested sera from cats in South Africa and Zimbabwe by indirect fluorescence for antibodies reactive with phase II Coxiella burnetii antigen (Nine Mile strain). Reactive antibodies were detected at titres of > or = 1/40 in sera from cats in South Africa (1/52, 2%) and Zimbabwe (15/119, 13%). Our results indicate that cats in southern Africa are infected with C. burnetii and should be considered as sources of infection for humans.

Feline leukaemia virus: a review of immunity and vaccination

The availability feline leukaemia virus (FeLV) vaccines has added a new and important dimension to the control of this infectious agent. FeLV vaccination is a controversial issue, however, partly because of differences in the formulation between the current products, partly because of conflicting claims by vaccine manufactures and partly because experimental trials have shown that none of the vaccines provides 100 per cent protection against infection. This paper reviews the role of the immune response in determining the outcome following exposure to FeLV and describes the importance of FeLV subgroups. The five commercial FeLV vaccines currently available in the USA and Europe are described and the published literature on efficacy studies is summarised. However, these efficacy studies are often difficult to interpret for various reasons, including the small numbers of animals used; differences in challenge methods, vaccine strains and vaccine dose employed; and differences in postchallenge monitoring protocols.

Efficacy of hyposensitization in feline allergic diseases based upon results of in vitro testing for allergen-specific immunoglobulin E

A survey was undertaken to evaluate the responses to hyposensitization in cats for which a diagnosis of allergic disease was made by assessment of clinical signs and evaluation of allergen-specific immunoglobulin E (IgE) using the radioallergosorbent test (RAST). Eighty-one cases were available for analysis. In 39 cases, a dietary change resulted in some subjective improvement, which usually was minimal; however, some cases had significant improvement. In 75.3% of cases, an improvement of at least 50% was noted and ascribed to a combination of immunotherapy and dietary change, when implemented. The response of the 42 cases in which immunotherapy alone was used or where there was no response to dietary change was broadly similar. Response of the specific dermatological conditions ranged from 93.6% in the case of linear granuloma to 60% in cases where self-induced hair loss was evident. Response also was good in cases of presumed allergic asthma (86.1% improvement) and suspected allergic otitis externa (62.6% improvement). In nine patients, the hyposensitization was discontinued due to lack of response. The results suggest that confirmation of a suspected diagnosis of allergic disease in cats by means of in vitro tests and subsequent therapy with hyposensitization should be a major consideration in feline practice.

Genetic and antigenic heterogeneity among feline calicivirus isolates from distinct disease manifestations

The capsid protein genes of five feline calicivirus (FCV) isolates associated with different disease manifestations were cloned and sequenced. The viruses represented two recent isolates from cats with chronic stomatitis, one recent isolate from a cat with acute stomatitis, one recent isolate each from a cat with acute respiratory symptoms and the classical limping syndrome strain FCV-2280. The amino acid sequences were compared with eight other published sequences and analyzed for their relationships. Phylogenetic analysis of the complete capsid protein sequences or of known antigenic regions of that protein (hypervariable regions A and E) did not group the isolates of different disease manifestations in distinct subclusters. Monoclonal antibodies (MAbs) generated against either a chronic stomatitis isolate or a recent isolate associated with respiratory symptoms were tested against a panel of 11 recent isolates and four "classical' FCV strains, covering all known disease associations. With those MAbs no obvious clustering with respect to disease manifestation could be seen. Four specific sera prepared in rabbits against our prototype isolates also failed to cluster those isolates according to the disease manifestations when examined in neutralization tests. From these antigenic and genetic analyses of the capsid protein the hypothesis of the existence of biotypes of FCV responsible for distinct disease manifestations could not be confirmed.

Evaluation of commercially available assays of neopterin and beta 2-microglobulin for the assessment of disease progression in FIV-infected cats

Serum or plasma samples from cats at different stages of feline immunodeficiency (FIV) infection and from uninfected cats were tested using immunoassays designed to detect human neopterin and beta 2-microglobulin (beta 2M). The results obtained from the anti-human neopterin assay did not correlate with infection status, time post-infection, fCD4 count or clinical picture. Feline samples gave negative results in the anti-human beta 2M assay. The assay kits used in this study are not suitable for the determination of the effect of FIV infection on immune activation markers in the cat.

Adhesion of insect cells expressing the feline herpesvirus type 1 hemagglutinin (gD) to feline cell lines

Feline herpesvirus type 1 (FHV-1) gD-expressing Sf9 cells adhered to two feline cell lines, but not to the porcine, bovine, or canine cell lines tested. In addition, this adhesion activity was inhibited by a monoclonal antibody against FHV-1 gD. These results showed that the FHV-1 gD might bind to a specific-molecule(s) on the surface of feline cell lines. We discussed a possible importance of the FHV-1 gD in host cell restriction to FHV-1 infection.

Suspected ehrlichial infection in five cats from a household

Ehrlichiosis is a poorly recognized condition of cats that may be associated with anemia, leukopenia, thrombocytopenia, or dysproteinemia. Affected cats may have indirect fluorescent antibody titers to Ehrlichia canis and E risticii. We reviewed the clinical evaluation and response to treatment of 5 cats in a household where ehrlichial disease was suspected as the cause of recurrent leukopenias and thrombocytopenias. All of the cats had E risticii indirect fluorescent antibody titers and western blot confirmation of antibodies to 4 of the 9 major antigens of E risticii. Response to doxycycline was monitored serologically and hematologically in each cat, and indicated that administration of doxycycline at a dosage of 10 mg/kg of body weight, PO, every 12 hours, for a minimum of 21 days is necessary for treatment of this condition.

Feline colostrum--friend or foe: maternal antibodies in queens and kittens

The transfer of immunoglobulins (Ig) by colostrum from the queen to the neonatal kitten not only provides protection from infection, but may also cause serious illness. Neonatal isoerythrolysis may occur when kittens of blood type A or AB receive colostral anti-A alloantibodies from a type B queen. In contrast to other species, Ig concentrations in milk and colostrum did not differ markedly. Gastrointestinal absorption of IgG was limited to the first day of life. The half-lifes of maternally derived IgG and IgA in kittens were shorter than in puppies. In conclusion, milk from another queen may be given as a replacement for colostrum to neonatal kittens. Kittens at risk of neonatal isoerythrolysis must be removed from their type B queen during the first day of life and may safely receive milk or colostrum from a type A queen.

Identification of lambda light chain amyloid in eight canine and two feline extramedullary plasmacytomas

Amyloid deposition in varying amounts and with variable patterns of distribution (focal or diffuse) was demonstrated in eight canine and two feline extramedullary plasmacytomas expressing lambda light chains. Frequently, the neoplastic plasma cells had been displaced by the amyloid deposits. Foreign-body giant cells were regularly detected in the vicinity of the amyloid. In all 10 cases, Congo-red staining of the amyloid was resistant to potassium permanganate oxidation. Immunohistochemically, the amyloid reacted positively with cross-reacting antibodies against human and equine A lambda amyloids. Extramedullary plasmacytomas accompanied by localized AL amyloidosis have so far been described in human beings, dogs, cats and horses.

Cryptococcal infection in cats: factors influencing treatment outcome, and results of sequential serum antigen titers in 35 cats

The relationship between treatment outcome and location of cryptococcal infection, gender, magnitude of pretreatment cryptococcal antigen titers, results of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) serology, and serial changes in antigen titers during and after treatment were evaluated in a prospective and nonrandomized study of 35 cats with cryptococcosis. A commercial cryptococcal latex agglutination kit (CALAS; Meridian Diagnostic Inc, Cincinnati, OH) was used to detect cryptococcal antigen in sera. All cats were treated with itraconazole (Sporanox; Janssen Pharmaceutica Inc, Titusville, NJ). Pretreatment mean log titers for serum cryptococcal antigen were not influenced by location of the infection. Treatment outcome was not influenced by gender, location of the infection, or magnitude of pretreatment serum antigen titer. Treatment outcome was influenced by FeLV and FIV status; cats seropositive for FeLV or FIV had a higher likelihood of treatment failure (P = .008). The cryptococcal antigen titers of cats successfully treated decreased with significant linearity over time during treatment (r = -.64, P < .000001), whereas the corresponding titers for cats not treated successfully did not decrease with significant linearity (r = -.03, P > .9). For cats in which treatment was successful, antigen titers decreased significantly from pretreatment values by 1.3 orders of magnitude at 2 months after initiation of treatment. By 10 months after initiating treatment, log titers decreased by at least 2 orders of magnitude in all cats successfully treated, and 9 of 16 cats had undetectable titers. In contrast, in 5 of 6 cats in which treatment failed, antigen titers were unchanged or increased in magnitude even after at least 6 months of treatment.

A latex cryptococcal antigen agglutination test for diagnosis and monitoring of therapy for cryptococcosis

A latex cryptococcal antigen agglutination test (LCAT) was performed on sera obtained during the first 14 days of treatment from 58 animals (46 cats, 9 dogs, 2 koalas and 1 long billed corella) with cryptococcosis. The same commercial kit was used for all samples, and most serum samples were treated with pronase before testing. Sera from all 58 cases tested positive with the qualitative LCAT protocol (using undiluted sera), while sera from all 26 cats without cryptococcosis tested negative. Titres determined using the quantitative protocol ranged from 1 to > or = 131 072 (median titre between 2048 and 4096), with 57 of 58 cases (including all 8 animals that presented for neurological signs) having titres > or = 2 and thus considered positive according to the manufacturer's recommendations. The LCAT titre was positively correlated with disease severity (r = 0.4169; P = 0.0011), and patients with disseminated skin and/or lymph node involvement had significantly higher titres than those that did not (P = 0.0157). The presence of neurological signs, the species of the patient, concurrent viral disease (in cats) and the biotype of the isolate had no significant association with the LCAT titre. Cats that died of active cryptococcosis despite treatment did not have significantly higher titres (P = 0.3010) than those that responded to treatment. Sequential LCAT determinations obtained in 37 patients during treatment provided a useful quantitative indication of clinical progress, although the decline in titre lagged somewhat behind clinical improvement. Generally, the antigen titre declined by 2 to 4 fold per month during successful therapy. Although there are insufficient data to make unequivocal recommendations, we suggest that either antifungal therapy be continued until the LCAT titre declines to less than 1, or therapy be discontinued after a 32 fold or greater reduction in titre, with periodic monitoring of the serum antigen titre. Treatment of serum samples with pronase substantially increased the sensitivity of the LCAT.

Seroepidemiology of feline chlamydiosis by microimmunofluorescence assay with multiple strains as antigens

The prevalence of anti-chlamydia antibodies was examined in 232 cat sera collected in 1985 and from 1993 to 1995 from laboratories and veterinary hospitals located in 11 prefectures of Japan. The antibodies were determined by an indirect microimmunofluorescence test using six strains of feline Chlamydia: one strain each of avian- and guinea pig-derived C. psittaci and one strain each of C.pecorum, C.pneumoniae and C.trachomatis. Positive rates of IgG antibodies to chlamydiae were 34.4% in 1985 and 16.5-21.4% from 1993 to 1995. Positive rates of IgM antibodies to chlamydiae were 8.2% in 1985 and 6.6-14.3% from 1993 to 1995. Variations in antibody reactivity to the different feline strains were observed. The results suggest the wide prevalence of chlamydial infection in cats in Japan, and antigenic diversity in the feline strains of C.psittaci.

Clinical and serologic evaluation of cats with cryptococcosis

OBJECTIVE

To evaluate the long-term clinical outcomes and serologic changes in cryptococcal antigen and antibody titers in cats with confirmed Cryptococcus neoformans infection.

DESIGN

Prospective case series.

ANIMALS

47 cats with cryptococcosis.

PROCEDURE

Cats included in this study were determined to have cryptococcosis on the basis of identification of C neoformans on histologic or cytologic examination, isolation of C neoformans in culture, or positive serologic test results for cryptococcal antigens. Information concerning the signalment, history, physical examination findings, FeLV and feline immunodeficiency virus status, serologic testing, treatment, and outcome for each cat was requested on a survey form. Follow-up measurements of serum cryptococcal antigen and antibody titers were requested for all surviving cats.

RESULTS

Signalment and clinical signs of cats with cryptococcosis reported here were consistent with previous reports. Treatment consisted primarily of azole antifungal drugs. All cats were seronegative for cryptococcal antibody titers, whether tested initially or at follow-up examination. All but 1 cat tested were seropositive for cryptococcal antigens when initially tested. Cats with and without clinical signs of C neoformans infection were seropositive for cryptococcal antigens months to years after initial diagnosis of cryptococcosis.

CLINICAL IMPLICATIONS

The results of this study indicate that serum titers to cryptococcal antigens in cats can persist with or without clinical signs for months to years after an initial diagnosis of cryptococcosis is made. Repeated evaluation of serum cryptococcal antigen titers is advised during the treatment of cats to monitor progress, evaluate prognosis, and guide cessation of treatment.

Proficiency testing of selected antigen and antibody tests for use in dogs and cats

OBJECTIVE

To determine the correlation of seroimmunologic test results between reference and nonreference laboratories.

DESIGN

Retrospective data analysis.

PROCEDURE

Serum samples obtained from naturally infected dogs and cats were distributed to reference and nonreference laboratories for seroimmunologic testing. Correlation of test results was evaluated by use of nonparametric analysis.

RESULTS

Correlation coefficients were high between laboratory groups for samples tested for feline immunodeficiency virus antibodies, FeLV antigen, and toxoplasmosis antibodies in cats. Results for feline immunodeficiency virus antibody tests from reference laboratories were more likely to be positive than results from nonreference laboratories. Test results for feline infectious peritonitis antibodies, antinuclear antibodies, and Borrelia antibodies in cats were not significant. Coefficient correlations were significant for results of heart-worm antigen, Brucella antibodies, Toxoplasma antibodies, antinuclear antibodies, and rheumatoid factor in dogs. Results for Borrelia antibodies were not correlated between laboratory groups.

CLINICAL IMPLICATIONS

Results were highly correlated between reference and nonreference laboratories for 8 of 14 seroimmunologic tests. Seroimmunologic tests for use in cats were less correlated as a group than those for use in dogs. Poor correlation of results between laboratories was attributed to variations in control agents, antigens, reagents, technical expertise, and cutoff values and end-point titers used for diagnosis.