Evaluation of feline immunodeficiency virus and feline leukemia virus transmembrane peptides for serological diagnosis.

The general model for retrovirus transmembrane (TM) proteins proposed by Gallaher et al. (W. R. Gallaher, J. M. Ball, R. F. Garry, M. C. Griffin, and R. C. Montelaro, AIDS Res. Hum. Retroviruses 5:431-440, 1989) suggests that all retrovirus TM proteins may contain an immunodominant domain (Imd-TM peptide) located at the apex of the TM polypeptide. Although this Imd-TM peptide has been shown to be immunodominant in a variety of lentivirus infections, there has not been a detailed serological analysis of an oncovirus Imd-TM peptide as a diagnostic agent. We describe here an analysis of the antigenic properties and diagnostic potentials of the predicted Imd-TM peptides of feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) in serological assays of sera from infected cats. The results of these studies demonstrate that antibodies specific to the FIV Imd-TM peptide are detected within 2 weeks postinfection, are maintained at high levels for extended periods, and are not detectable in uninfected or FeLV-infected cats. In marked contrast, the FeLV Imd-TM peptide displayed only negligible levels of serological reactivity in FeLV-infected cats. These studies indicate that the peptide is a useful reagent for the detection of antibodies to FIV.     

Prevalence of antibodies to feline parvovirus, calicivirus, herpesvirus, coronavirus, and immunodeficiency virus and of feline leukemia virus antigen and the interrelationship of these viral infections in free-ranging lions in east Africa.

While viral infections and their impact are well studied in domestic cats, only limited information is available on their occurrence in free-ranging lions. The goals of the present study were (i) to investigate the prevalence of antibodies to feline calicivirus (FCV), herpesvirus (FHV), coronavirus (FCoV), parvovirus (FPV), and immunodeficiency virus (FIV) and of feline leukemia virus (FeLV) antigen in 311 serum samples collected between 1984 and 1991 from lions inhabiting Tanzania's national parks and (ii) to evaluate the possible biological importance and the interrelationship of these viral infections. Antibodies to FCV, never reported previously in free-ranging lions, were detected in 70% of the sera. In addition, a much higher prevalence of antibodies to FCoV (57%) was found than was previously reported in Etosha National Park and Kruger National Park. Titers ranged from 25 to 400. FeLV antigen was not detectable in any of the serum samples. FCoV, FCV, FHV, and FIV were endemic in the Serengeti, while a transient elevation of FPV titers pointed to an outbreak of FPV infection between 1985 and 1987. Antibody titers to FPV and FCV were highly prevalent in the Serengeti (FPV, 75%; FCV, 67%) but not in Ngorongoro Crater (FPV, 27%; FCV, 2%). These differences could be explained by the different habitats and biological histories of the two populations and by the well-documented absence of immigration of lions from the Serengeti plains into Ngorongoro Crater after 1965. These observations indicate that, although the pathological potential of these viral infections seemed not to be very high in free-ranging lions, relocation of seropositive animals by humans to seronegative lion populations must be considered very carefully.     

Seroepidemiological survey of infection by feline leukemia virus and immunodeficiency virus in Madrid and correlation with some clinical aspects

A study of 180 healthy cats found that 15.6% were feline leukemia virus (FeLV) positive, 8.3% were feline immunodeficiency virus (FIV) positive, and 1.1% were FIV and FeLV positive, which corresponded to 30.4, 13.8, and 2.6, of 115 cats with FIV- and FeLV-related symptoms, respectively. Differences were seen in the sexes and ages of the populations studied. Anemia, leukopenia, and lymphopenia were the most frequent hematological abnormalities in infected cats.     

Absence of coreceptor switch with disease progression in human immunodeficiency virus infections in India

The envelope glycoprotein of the human immunodeficiency virus (HIV) utilizes CD4 as a receptor and CCR5 and/or CXCR4 as coreceptor to gain entry into the cell. The CCR5-tropic viruses, observed early in infection, could be important in transmission and the CXCR4-tropic viruses, observed late, may play an important role in disease progression. Viruses from 40 HIV-positive, asymptomatic or symptomatic individuals in India were isolated. Of 40 isolates 39 used CCR5. Thirty-three isolates were subtype C, 3 isolates were subtype A, and 4 isolates were HIV-2. Only 1 HIV-2 isolate, from a symptomatic individual, was dualtropic. Therefore, a majority of isolates from India belonged to subtype C and all the isolates utilized CCR5 exclusively irrespective of HIV disease status.     

Immunological changes in cats with concurrent Toxoplasma gondii and feline immunodeficiency virus infections.

To examine the immunological changes in cats concurrently infected with feline immunodeficiency virus (FIV) and Toxoplasma gondii, kittens (four per group) were inoculated with FIV, T. gondii, both agents, or no pathogens. Blood mononuclear cells and plasma were collected weekly for lymphocyte assays and serology. At week 14, spleen and lymph node cells were used for lymphocyte assays; brains and mesenteric lymph nodes were used for isolation of T. gondii. More T. gondii organisms were present in tissues of the dually infected cats than in tissues of cats with toxoplasmosis alone. Two dually infected cats and one cat infected with T. gondii developed chorioretinitis. Spleen, lymph node, and blood mononuclear cells from dually infected cats had the greatest reduction in mitogenic responses. By week 3, cats infected with FIV underwent a decrease in the number of CD4 cells that was not changed by concurrent T. gondii infection; the number of CD8 cells increased only in cats infected with T. gondii alone. For cats infected with T. gondii, the responses of lymphocytes to T. gondii antigen were not affected by FIV infection; the responses to FIV antigen were negligible in all groups. Overall, this study indicates that FIV infection favors T. gondii proliferation. Also, the establishment of toxoplasmosis may enhance FIV-induced immunodeficiency and is likely to cause a more rapid disease progression than that from infection with FIV alone.     

Susceptibility and production of a feline endogenous retrovirus (RD-114 virus) in various feline cell lines

RD-114 virus is a replication-competent feline endogenous retrovirus that has been classified as a xenotropic virus. In this study, we examined the expression of the receptors for RD-114 virus in feline cell lines by conducting a pseudotype virus infection assay. Six out of eight feline cell lines were susceptible to the RD-114 pseudotype virus and two cell lines (MCC and FER cells) were resistant. The two resistant cell lines and one cell line (CRFK cells) weakly sensitive to the RD-114 pseudotype virus were found to produce replication-competent RD114-like viruses by the LacZ marker rescue assay and the interference assay. These data strongly suggest that RD-114 virus is polytropic and resistance to RD-114 virus in certain cell lines is due to receptor interference but not polymorphism of the RD-114 receptors. In addition, we determined the amino acid sequences of the envelope region of RD-114-like viruses produced from MCC, FER and CRFK cells. The sequences were identical with the authentic RD-114 virus. Because many feline cell lines are used to manufacture live attenuated vaccines for companion animals, attention should be paid to contamination of the RD-114 virus in vaccines.     

Influence of antisera to oncornavirus glycoprotein (gp71) on infections of cats with feline leukemia virus.

Six-month-old kittens that had been inoculated 6 days previously with feline leukemia virus (FeLV) were treated with either normal goat serum, goat antiserum to FeLV, or goat antiserum to the purified Friend leukemia virus (FLV) gp71. All of the kittens treated with normal goat serum became persistently viremic, whereas up to three-fourths of those treated with the antiviral antisera resisted persistent viremia. These results suggest that viral antigens, in particular, their interspecies determinants, can be used as targets for immunotherapeutic regimens for the prevention and control of diseases induced by oncornaviruses.     

Adoptive immunotherapy of feline immunodeficiency virus with autologous ex vivo-stimulated lymphoid cells modulates virus and T-cell subsets in blood

The potential of immunotherapy with autologous virus-specific T cells to affect the course of feline immunodeficiency virus (FIV) infection was explored in a group of specific-pathogen-free cats infected with FIV a minimum of 10 months earlier. Popliteal lymph node cells were stimulated by cocultivation with UV-inactivated autologous fibroblasts infected with recombinant vaccinia viruses expressing either FIV gag or env gene products, followed by expansion in interleukin-2. One or two infusions of both Gag- and Env-stimulated cells resulted in a slow increase in FIV-specific gamma interferon-secreting T cells in the circulation of cats. In the same animals, viral set points fluctuated widely during the first 2 to 3 weeks after adoptive transfer and then returned to pretreatment levels. The preexisting viral quasispecies was also found to be modulated, whereas no novel viral variants were detected. Circulating CD4(+) counts underwent a dramatic decline early after treatment. CD4/CD8 ratios remained instead essentially unchanged and eventually improved in some animals. In contrast, a single infusion of Gag-stimulated cells alone produced no apparent modulations of infection.     

The bone marrow in human immunodeficiency virus (HIV)-related disease. Morphology and clinical correlation.

To determine the true incidence of abnormalities in bone marrow specimens from patients infected with human immunodeficiency virus (HIV) and the clinical significance of these abnormalities regarding their cause and their role in the production of hematologic complications, 216 bone marrow biopsies, aspirates, and/or imprint preparations from 178 patients who either were seropositive for HIV infection or met the Centers for Disease Control (CDC) criteria for acquired immunodeficiency syndrome (AIDS) were studied. Detailed morphologic review was performed in a blind fashion as to clinical status. Extensive clinical, therapeutic, and laboratory data were collected for each patient. Statistical analysis was performed to detect significant correlations between morphologic findings and clinical/therapeutic/laboratory features. Among the most common bone marrow findings were hypercellularity (53% of specimens), myelodysplasia (69%), evidence of reticuloendothelial (RE) iron blockade (65%), megaloblastic hematopoiesis (38%), fibrosis (20%), plasmacytosis (25%), lymphocytic aggregates (36%), and granulomas (13%). A number of statistically significant correlations between morphologic findings and clinical features were noted. No significant association was detected between any morphologic finding and therapy with a variety of drugs. In 7 of 14 (50%) patients found to have marrow involvement by malignant neoplasm, the bone marrow represented the initial site of diagnosis of the neoplasm. Most of the bone marrow abnormalities associated with HIV infection appear to be related directly to the infection or its complications and not to therapeutic intervention. In certain clinical situations, bone marrow examination continues to be useful in the management of patients infected with HIV.     

Development of feline immunodeficiency virus ORF-A (tat) mutants: in vitro and in vivo characterization

A functional ORF-A is essential for efficient feline immunodeficiency virus replication in lymphocytes. We have characterized a series of mutants of the Petaluma strain, derived from p34TF10 and having different combinations of stop codons and increasingly long deletions in ORF-A. Six clones proved fully replicative in fibroblastoid Crandell feline kidney cells and monocyte-derived macrophage cultures but failed to replicate in T cell lines and primary lymphoblasts. Cats inoculated with three selected mutants had considerably milder infections than controls given intact ORF-A virus. In vivo, the mutants maintained growth properties similar to those in vitro for at least 7 months, except that replication in lymphoid cells was strongly reduced but not ablated. One mutant underwent extensive ORF-A changes without, however, reverting to wild-type. Antiviral immune responses were feeble in all cats, suggesting that viral loads were too low to represent a sufficiently powerful antigenic stimulus.     

Haematological abnormalities in human immunodeficiency virus (HIV) disease.

Peripheral blood and bone marrow changes are commonly seen in disease associated with human immunodeficiency virus (HIV). This annotation aims to summarise these changes and to suggest possible factors entailed in their occurrence.     

Simple in vitro methods for titrating feline immunodeficiency virus (FIV) and FIV neutralizing antibodies.

The feline immunodeficiency virus (FIV) readily produced syncytia in Crandell feline kidney (CrFK) cells adapted to a medium containing 0.5% fetal calf serum, a variety of growth factors and other supplements. This finding has been exploited to develop simple and sensitive virus titration and neutralization assays. High titre neutralizing antibodies were detected in cats infected naturally and experimentally with FIV, but not in uninfected animals.     

Pathological manifestations of feline immunodeficiency virus (FIV) infection in wild African lions

Feline immunodeficiency virus (FIV) causes AIDS in the domestic cat (Felis catus) but has not been explicitly associated with AIDS pathology in any of the eight free-ranging species of Felidae that are endemic with circulating FIV strains. African lion (Panthera leo) populations are infected with lion-specific FIV strains (FIVple), yet there remains uncertainty about the degree to which FIV infection impacts their health. Reported CD4+ T-lymphocyte depletion in FIVple-infected lions and anecdotal reports of lion morbidity associated with FIV seroprevalence emphasize the concern as to whether FIVple is innocuous or pathogenic. Here we monitored clinical, biochemical, histological and serological parameters among FIVple-positive (N = 47) as compared to FIVple-negative (N = 17) lions anesthetized and sampled on multiple occasions between 1999 and 2006 in Botswana. Relative to uninfected lions, FIVple-infected lions displayed a significant elevation in the prevalence of AIDS-defining conditions: lymphadenopathy, gingivitis, tongue papillomas, dehydration, and poor coat condition, as well as displaying abnormal red blood cell parameters, depressed serum albumin, and elevated liver enzymes and gamma globulin. Spleen and lymph node biopsies from free-ranging FIVple-infected lions (N = 9) revealed evidence of lymphoid depletion, the hallmark pathology documented in immunodeficiency virus infections of humans (HIV-1), macaques, and domestic cats. We conclude that over time FIVple infections in free-ranging lions can lead to adverse clinical, immunological, and pathological outcomes in some individuals that parallel sequelae caused by lentivirus infection in humans (HIV), Asian macaques (SIV) and domestic cats (FIVfca).     

Interferon alpha (IFN)-macrophage interactions in human immunodeficiency virus (HIV) infection: role of IFN in the tempo and progression of HIV disease.

Components of the host immune response that constrain virus replication and affect long-lasting antiviral immunity following HIV infection are incompletely defined. IFNs are critical participants in host antiviral processes. While IFN induces significant anti-retroviral activities, they also serve as harbingers for poor clinical outcomes. Moreover, monocytes, a major cellular source of IFN and HIV in man, are poor producer cells for IFN following HIV infection. Indeed, HIV infection of monocytes results in a diminished production and induction of IFN. IFN is only produced during cell to cell contact between HIV-infected cells and uninfected PBMC. Analysis of the biologic activity of HIV-induced IFN(s) shows that it poorly restricts HIV replication. Thus, the role of IFN in HIV disease is complex and seemingly paradoxical. The diminished capacity of HIV-infected monocytes to produce IFN and the production of defective IFNs likely reflect specific viral adaptive mechanisms for persistent infection.     

Pathogenesis of feline panleukopenia virus in susceptible newborn kittens I. Clinical signs, hematology, serology, and virology

Inoculation of susceptible newborn kittens with a large dose of panleukopenia virus caused subclinical infection in 19 of 23 cases. All infected kittens developed severe and prolonged leukopenia. Cell-free virus was present in the blood from 1 to 7 postinoculation days. The virus spread to all organs, regardless of the route of inoculation. The thymus, spleen, mesenteric lymph nodes, and the cerebellum were the most severely infected organs. Kittens responded to virus infection by production of specific antibodies, first detectable in the circulatory system 6 to 8 days after infection. Antibody production preceded recovery from leukopenia by 3 days.