W. F. Robinson

Conservation of the central MHC genome: PFGE mapping and RFLP analysis of complement, HSP70, and TNF genes in the goat

A degree of conservation of the genes located between class II and class I [central major histocompatibility complex (MHC) genes] is apparent among mammalian species including primates and the mouse. Few others have been analyzed. The caprine MHC is of particular interest, since it has recently been observed that susceptibility to a lentivirus-induced polyarthritis (caprine arthritis) segregates with serologically defined MHC class I antigens. This arthritis resembles, in a number of respects, rheumatoid arthritis in man. Human cDNA probes were used to examine the caprine central MHC and class I and II genes by restriction fragment length polymorphism (RFLP) and by pulsed field gel electrophoresis (PFGE) in order to define the polymorphism and linkage of central MHC genes to class I and class II genes. An outbred population of dairy goats (Saanen, British Alpine, Anglo Nubian, and Toggenberg) was examined for class I and class II RFLPs. Both regions were found to be highly polymorphic. The number of fragments hybridizing to an HLA-B7 probe after Eco RI, Bam HI, Bgl II, or Hind III digestion suggests there may be 10–13 class I genes. The degree of polymorphism was comparable to that reported in the mouse. Limited polymorphism was found in the central MHC genes. The caprine C4 and CYP21 genes were duplicated and demonstrated RFLP with Bam HI, Hind III, Eco RV, and Taq I. An infrequent Taq I C2 polymorphism was found. PFGE revealed substantial conservation of both the order and linkage of the central MHC genes when compared with mous and man. C4, C2, CYP21, HSP70, and tumor necrosis factor (TNF) genes are all located within 800 kilobase (kb) of the class I loci. Distant from the class I region, the C4, C2, and CYP21 genes are linked on a short genomic segment (180 kb Not I and 190 kb Pvu I fragments). HSP70 cohybridizes with the complement genes on a 380 kb Mlu I fragment. Linkage of HSP70, TNF, and class I genes was found on a single Not I fragment (610 kb). TNF and class I cohybridize on Pvu I (730 kb) and Not I (610 kb) fragments. Conservation of a similar central MHC genomic structure across species argues for functional interaction between the central MHC genes. We postulate selection for these central MHC genes through their role as non antigen-specific regulators of immune response.

Extensive sequence variation of feline immunodeficiency virus env genes in isolates from naturally infected cats

SummaryIn an investigation of the evolution of feline immunodeficiency virus (FIV) in vivo, sequential isolates from a persistently infected cat were examined by direct sequencing following amplification of selected subgenomic regions by polymerase chain reaction (PCR). Three isolates, T 90, T 91, and T 92, obtained over a three-year period revealed no changes to regions known to be conserved withingag andpol genes. Additionally, no change occurred withingag andpol in an isolate recovered from a second cat which was experimentally infected with T 90. Changes were detected within an N-terminal region of the envelope glycoprotein gp 120 (env). These consisted of point mutations, some of which would result in amino acid substitutions and the predicted amino acid changes tended to cluster within variable domains. Inoculation of T 90 into a second cat resulted in a different pattern of mutations than that observed for the three isolates from the first cat. In all cases, virus isolates derived from the same cat were much more highly related to each other (extent ofenv variation was 0.5–1.5%) than to isolates from other cats (10–12%env variation). The rate of change of FIV was estimated to be 3.4×10−3 nucleotide substitutions per site per year for theenv gene and less than 10−4 nucleotide substitutions per site per year for thegag andpol genes, values concordant with that found for human immunodeficiency virus 1. Both nucleotide and amino acid changes in the gp 120 region were found to be directional, suggesting that selective pressures influence FIV envelope gene sequences.

Canine Parvoviral Disease: Experimental Reproduction of the Enteric Form with a Parvovirus Isolated from a Case of Myocarditis

Five 7-week-old pups and four 4-week-old pups, all seronegative to canine parvovirus, were inoculated intravenously with 1000 haemagglutinating units of canine parvovirus originally isolated from the myocardium of a dog with naturally occurring myocarditis. After three days, pups in both litters became pyrexic, anorectic and depressed, with vomiting and diarrhoea. The 4-week-old pups were killed on day 4, and the 7-week-old pups died or were killed on day 5 post-inoculation. Histological examination showed degeneration and necrosis of intestinal crypt epithelial cells and villous atrophy. All pups had thymic atrophy caused by lymphoid depletion. Peyers patches, mesenteric lymph node and spleen also had lymphoid depletion. Lymphoid necrosis was present occasionally in these tissues. In the bone marrow, granulocytes and granulocyte and erythroid precursors were depleted. Amphophilic intranuclear inclusion bodies were abundant in crypt epithelial nuclei, less so in myocardial nuclei. Canine parvovirus was isolated from intestinal contents, thymus, spleen, mesenteric lymph node and liver in most pups, but not from kidney or myocardium.

Nucleotide sequences of Australian isolates of the feline immunodeficiency virus: comparison with other feline lentiviruses

SummaryProviral DNA from four Australian isolates of feline immunodeficiency virus (FIV) was amplified by PCR and the nucleotide sequence determined for two conserved regions withingag (p 15/p 24) andpol (RT) genes. Comparison with the nucleotide and deduced amino acid sequence of two previously described U.S. isolates from California (Petaluma and PPR), and a third from Maryland (MD) as well as the Japanese isolate TM 2, revealed a close similarity between the Australian and Californian isolates with 95–97% nucleotide and 96–99% amino acid homologies. By contrast, the Maryland and Japanese isolates were more distantly related with only 84–87% nucleotide and 90–94% amino acid homology with either the Australian or Californian isolates. The relationship of the Australian FIV isolates to other domestic isolates as well as eight lentiviral isolates from wild felidae (panthers) published previously, was investigated further by constructing a phylogenetic tree based on thepol sequence. This revealed two subgroups of FIV, an Australian/Californian group and a less tightly clustered Maryland/Japanese group. These results suggest that the genomic variability of FIV is reflected by more than simply geographic distance. Furthermore, the relative genetic homogeneity found between Australian isolates suggest a shorter period of evolution of the virus in Australia than in North America.

Canine Parvoviral Myocarditis: A Morphologic Description of the Natural Disease:

Naturally occurring acute parvoviral myocarditis in puppies 3 to 8 weeks of age was characterised clinically by sudden death or death following a brief period of dyspnoea. Mortality within litters varied from 20% to 100%. The principal lesion was in the myocardium, which in most cases was mottled by pale patches and bands. Moderate to severe pulmonary oedema with marked peribronchial and perivascular oedema was present. In some cases, the wall of the gall bladder was oedematous. Microscopically the ventricular myocardium had myofibre loss, multifocal myofibre necrosis, a mononuclear cell infiltrate of variable intensity and reactive stromal elements. In every case there were Feulgen-positive, amphophilic, intranuclear inclusion bodies in myocardial nuclei. Ultrastructurally the inclusions were composed of dense granular material and particles resembling parvovirions. Pulmonary alveolar septae were thickened by fibroblasts. Peribronchial and perivascular lymphatics were distended with oedema fluid and occasionally erythrocytes. The pulmonary lesions were considered secondary to the myocardial dysfunction. Some of the puppies that survived the acute disease developed ventricular myocardial fibrosis and died in congestive heart failure.

The pathology of disseminated Aspergillus terreus infection in dogs.

Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs—nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.

The detection and quantification of feline immunodeficiency provirus in peripheral blood mononuclear cells using the polymerase chain reaction

The polymerase chain reaction method (PCR) was used to detect feline immunodeficiency virus proviral DNA in peripheral blood mononuclear cells (PBMC) of a group of 8 experimentally infected cats. The proportion of PBMC containing provirus was determined from 6 to 32 weeks post inoculation (p.i.) by performing PCR on serially diluted samples of PBMC. Primers from the p15 and p24 regions of the gag gene were used and Southern hybridization using an end-labelled probe was required to confirm primer-specific products. Provirus was detected in 5 of 8 cats by 6 weeks p.i. in 50000 PBMC, and in all 8 infected cats by 8 weeks p.i. Provirus was not detected in PBMC from any of 3 FIV negative cats. The proportion of PBMC containing provirus in individual cats ranged from 1 in 70 to 1 in 99600 PBMC. There was no significant decline over time in the proportion of PBMC containing provirus. Sequencing of a segment (287 bases) of the gag region of a West Australian FIV isolate (T90) revealed only slight nucleotide divergence from the North American Petaluma and PPR isolates and wider divergence from the Japanese TM2 clone.

Feline immunodeficiency virus infection: plasma, but not peripheral blood mononuclear cell virus titer is influenced by zidovudine and cyclosporine

SummaryThe plasma and peripheral blood mononuclear cell (PBMC) titer of feline immunodeficiency virus (FIV) in experimentally infected cats was assessed following administration of either zidovudine or cyclosporine. Treatments were begun 24 h post infection (p.i.) and continued for 4 weeks. Zidovudine treatment did not prevent establishment of infection with FIV, but plasma virus titers were significantly lower than controls at 2 weeks p.i. This reduction of plasma virus titer by zidovudine was not maintained at subsequent sampling times. Similarly, cyclosporine treatment initially lowered plasma virus titers at 2 weeks p.i., but at 4 weeks p.i. the plasma virus titers in cyclosporine-treated cats were significantly higher than in the untreated group. In the untreated group, plasma virus titers declined rapidly to an undetectable level by 14 weeks p.i. Neither zidovudine or cyclosporine treatment significantly influenced the titer of FIV in PBMCs. In all groups (untreated, zidovudine and cyclosporine) the titers in PBMC were high for the duration of the experiment. The decline in plasma virus titers in immunocompetent cats combined with the effect of cyclosporine on plasma titers strongly suggests that the immune system plays a major role in clearing FIV from plasma. In contrast, it appears that the immune response has little impact on PBMC virus titers. This shows that for complete assessment of antiviral agents, both cell-free and cell-associated virus titers must be examined. We also suggest that the limitation of viral titers in PBMC may be of critical importance in the control of lentiviral infection.

Feline immunodeficiency virus: quantification in peripheral blood mononuclear cells and isolation from plasma of infected cats.

SummaryThe titer of feline immunodeficiency virus in peripheral blood mononuclear cells (PBMC) and the presence of infectious virus in plasma was investigated over 20 week period in 8 experimentally infected cats, 3 uninfected cats and 2 naturally infected cats by end point dilution cultures using a feline T-lymphoblastoid cell line (MYA-1). FIV was isolated from PBMC of all infected cats, but not from the uninfected cats. FIV was also isolated consistently from 100 µl plasma from most of the experimentally infected cats, but not from the 2 naturally infected cats. The virus titer in PBMCs in both experimentally and naturally infected cats was comparatively high, ranging from 10 TCID/106 PBMC to 14,286 TCID/106 PBMC. The titers in PBMC of individual cats remained unchanged or varied only slightly over the 20 week period. In contrast, the titers varied substantially between cats, with significantly higher titers in the youngest litter (4 cats) than in the oldest litter (3 cats). This suggests that there is an age-related factor influencing the level of PBMC virus titers in experimental infection with FIV. A similar age-related susceptibility has been shown with feline leukemia virus. More importantly, the sustained titers in the experimentally infected cats bear close resemblance to infection of children with human immunodeficiency virus. These data reinforce suggestions that age and immune maturity have a fundamental influence on PBMC and plasma titers in lentivirus infections.

The caprine MHC contains DYA genes

Department of Clinical Immunology, Royal Perth Hospital, Wellington Street, GPO Box X2213, Perth WA6000, Western Australia 2 Department of Veterinary Pathology, Veterinary School, Murdoch University, Perth, Western Australia 3 Department of Animal Breeding, Agricultural University Wageningen, Marykeweg 40, 6709 PG Wageningen, and Department of Immunohaematology and Bloodbank, University Hospital, Bldg 1, E3-Q, Rijnsburgerweg 10, 2333 AA Leiden, The Netherlands