Is feline foamy virus really apathogenic?

Feline foamy virus (FFV) is a retrovirus commonly found in cats. It is generally thought to be apathogenic, making it a suitable candidate as a gene therapy vector. However, there have been reports of association of FFV with chronic progressive arthritis and a cofactor effect with feline immunodeficiency virus. This study investigated experimental FFV infection and whether this was associated with signs of disease. Eight young specific pathogen free cats were inoculated intramuscularly with FFV. The cats were examined twice weekly and blood and pharyngeal samples were taken. Haematology, biochemistry and FFV quantitative polymerase chain reaction (qPCR) were performed. Tissue samples were also collected throughout the six month period. FFV was initially detected by qPCR in the blood within the first two weeks of infection and viraemia persisted throughout the study. Two peaks of viraemia were observed, at day 20 (80-170FFU/ml blood) and day 155 (332-415FFU/ml blood). FFV was also consistently detected in oropharyngeal samples after day 36. Anti-FFV IgG was detected in all cats by ELISA; antibody levels had an early peak around day 35 and then increased again following the second rise in circulating viral load. All cats remained clinically normal, except for one cat with an unrelated gingivitis. None of the cats developed pyrexia. The biochemical profile and blood cell counts remained within normal limits except for one cat with a persistent eosinophilia. Initial fluctuations in white cell counts settled within three weeks and did not deviate outside of the normal ranges. All tissue samples contained FFV DNA; lymphoreticular tissues, salivary gland and lung had the highest viral loads. Although there were no gross pathological lesions on post mortem examination, histologically a mild glomerulonephritis and a moderate interstitial pneumonia were observed in all cats. We conclude that during the six month period of infection, although cats appeared clinically normal, histopathological changes were observed in the lungs and kidneys. Further investigation of the significance of these changes is warranted before FFV is developed as a vector for gene delivery.

Factors associated with upper respiratory tract disease caused by feline herpesvirus, feline calicivirus, Chlamydophila felis and Bordetella bronchiseptica in cats: experience from 218 European catteries.

A full history of the management practices and the prevalence of upper respiratory tract disease (URTD) at 218 rescue shelters, breeding establishments and private households with five or more cats was recorded. Oropharyngeal and conjunctival swabs and blood samples were taken from 1748 cats. The prevalences of feline herpesvirus (FHV), feline calicivirus (FCV), Chlamydophila felis and Bordetella bronchiseptica were determined by PCR on swab samples. An ELISA was applied to determine the prevalence of antibodies to B. bronchiseptica. The rates of detection by PCR of each pathogen in the cats in catteries with and without ongoing URTD were, respectively, FHV 16 per cent and 8 per cent; FCV 47 per cent and 29 per cent; C. felis 10 per cent and 3 per cent; and B. bronchiseptica 5 per cent and 1.3 per cent; the seroprevalences of B. bronchiseptica were 61 per cent and 41 per cent, respectively. There was evidence that FHV, FCV and B. bronchiseptica played a role in URTD. The risk factors associated with the disease were less than excellent hygiene, contact with dogs with URTD, and larger numbers of cats in the cattery or household.

Impaired T-cell priming and proliferation in cats infected with feline immunodeficiency virus.

OBJECTIVE: Cats naturally infected with feline immunodeficiency virus (FIV) are particularly susceptible to infection with opportunistic pathogens, suggesting that these animals are unable to develop an effective immune response against the pathogen. Previous studies have used CD4+:CD8+ lymphocyte ratios and mitogen blastogenesis to identify immunological abnormalities in FIV-infected cats. However, these studies provide limited information for understanding the nature of the cellular dysfunction in FIV-infected cats, particularly defects in antigen-specific immune responses. DESIGN: To investigate whether cats infected with FIV are less able to mount an immune response to previously unencountered antigens, we compared the development of antigen-specific cellular immunity at the stage of T-cell priming in uninfected and FIV-infected cats. INTERVENTIONS: The general immune status of cats was assessed by peripheral blood CD4+:CD8+ lymphocyte ratios (flow cytometry), and by lymphocyte blastogenesis response to T- and B-cell mitogens. In addition, we describe the development of an autologous culture system to measure specific priming of naive feline T-cells to soluble antigen in vitro. This assay was used to compare T-cell priming in uninfected cats and cats which had been infected with FIV for 6-27 months. RESULTS: As in HIV infection, CD4+:CD8+ lymphocyte ratios in FIV-infected cats were found to be inverted, due to a reduction in the percentage of CD4+ cells. In addition, lymphocyte blastogenesis to both T- and B-cell mitogens was significantly impaired in FIV-infected cats. Priming to keyhole limpet haemocyanin (KLH) elicited a late proliferative response resulting from the expansion of CD4+ (T-helper cells). T-cell growth factor secretion correlated with cell proliferation. Restimulation of cells with fresh antigen-presenting cells and antigen showed that antigen-specific T-cell priming had occurred in the initial culture. When primary proliferation responses in FIV-infected cats were examined, it was observed that naive CD4+ T-cells from FIV-infected cats were significantly impaired (P less than 0.001) in their ability to be primed to KLH when compared with uninfected controls. CONCLUSIONS: Impaired priming of naive CD4+ T-helper cells to antigen in FIV-infected cats may explain the increased susceptibility of these animals to infection by opportunistic pathogens. The poor ability of human patients with AIDS to develop humoral immunity following vaccination may also be caused by such a defect in T-cell priming.

Role of protein kinase C alpha, Arf, and cytoplasmic calcium transients in phospholipase D activation by sodium fluoride in osteoblast-like cells.

The effect of fluoride on phospholipase D (PLD) activation was studied using in vitro culture of Saos-2, MG-63 osteosarcoma cells, and normal osteoblast-like cells derived from human bone explants. Millimolar concentrations of NaF induced a significant accumulation of phosphatidylethanol (PEt) in Saos-2 cells but not in MG-63 and normal osteoblast-like cells. PLD activation was evident at 15 mM and concentration-dependent up to 50 mM. This stimulation was inhibited by deferoxamine, a chelator of Al3+, suggesting that PLD activation involves fluoride-sensitive G proteins. A good correlation was found between the levels of intracellular free Ca2+ and the activation of PLD. The time courses of the two responses were nearly identical. The ability of NaF to induce both responses was largely dependent on the presence of extracellular calcium. The calcium ionophore A23187 reproduced the effect of NaF, and this effect was antagonized by EGTA, suggesting that PLD activation was, at least in part, a calcium-regulated event. Phorbol 12-myristate 13-acetate (PMA) also stimulated PLD activity in human bone cells. Protein kinase C alpha (PKC alpha) and epsilon were expressed in Saos-2 cells. Acute pretreatment of cells with PMA reduced concomitantly the amounts of PKC alpha, but not of PKC epsilon, and the subsequent activation of PLD elicited by PKC activators. The PLD response to NaF was not attenuated but rather enhanced by down-regulation of PKC alpha. Therefore, PKC-alpha-induced PLD activation is unlikely to mediate the effect of NaF. Moreover, PMA and NaF showed a supraadditive effect on PLD activation in Saos-2 cells. This stimulation, in contrast to NaF alone, was not reduced by EGTA. Hence, mobilization of calcium by NaF cannot account for the enhanced PLD activation in response to PMA stimulation. Membrane Arf and RhoA contents were assessed by Western immunoblot analyses. Membranes derived from NaF-stimulated Saos-2 cells contained more Arf and RhoA when compared with membranes derived from control or PMA-stimulated cells. Translocation of the small GTPases was calcium-independent. We conclude that PLD activation by NaF in Saos-2 cells includes a fluoride-sensitive G protein, increases in the levels of intracellular calcium, and Arf/RhoA redistribution to membranes. The results also indicate that the NaF-induced Arf/RhoA translocation exerts in concert with PMA-activated PKC alpha a synergistic effect on the activation of PLD in Saos-2 cells.

Decreased mononuclear leukocyte TSH responsiveness in patients with major depression.

A subgroup of individuals with major depressive disorder have an impaired thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH). The molecular relationship between the mechanism of this "blunted" TSH response and depression is unknown. Numerous recent studies have characterized similarities and interactions between the immune and neuroendocrine systems. As the immune system both produces and responds to TSH, we utilized a peripheral blood leukocyte system to compare immunoreactive (ir)-TSH responsiveness in 10 adult patients (1 man, 9 women) with Research Diagnostic Criteria for major depressive disorder to that of 9 control subjects. All subjects had normal baseline serum TSH and T4 concentrations. Isolated mononuclear leukocytes were treated in vitro with either 0.5 micrograms/ml staphylococcal enterotoxin A (SEA), 50 micrograms/ml TRH, or no stimulant. After incubation, the cells were monitored for ir-TSH production by indirect immunofluorescence and reverse hemolytic plaque assay using antisera to TSH-beta. The culture supernates were analyzed by TSH radioimmunoassay. SEA- and TRH-treated cell cultures from depressed individuals had significantly fewer immunofluorescent positive cells, as well as significantly fewer and smaller plaques, than did similarly treated leukocytes from control subjects. The increase in supernatant ir-TSH was significantly less in TRH-treated cultures from depressed patients as compared to normals (p less than 0.05). These results suggest that examination of mononuclear leukocyte TSH production may reflect an altered state of neuroendocrine function and may thus be a useful marker for major depressive disorder.

Characterization of cytohesin-1 monoclonal antibodies: expression in neutrophils and during granulocytic maturation of HL-60 cells.

ADP-ribosylation factors (Arf) are small GTP-binding proteins involved in vesicular transport and the activation of phospholipase D (PLD). The conversion of Arf-GDP to Arf-GTP is promoted in vivo by guanine nucleotide exchange factors such as ARNO or cytohesin-1. In order to examine the expression of ARNO and cytohesin-1 in human granulocytes, we generated specific polyclonal and monoclonal antibodies (mAbs). We also overexpressed GFP-ARNO and GFP-cytohesin-1 in RBL-2H3 cells to characterize the specificity and the ability of cytohesin-1 mAbs to immunoprecipitate cytohesin-1. Among the hybridomas secreting cytohesin-1 mAbs, only the clones 2E11, 1E4, 3C8, 6F5, 4C7, 7A3 and 8F7 were found to be specific for cytohesin-1. Furthermore, mAb 2E11 immunoprecipitated GFP-cytohesin-1 but not GFP-ARNO under native conditions. In contrast, mAbs 5D8, 4C3, 2G8, 6G11, 4C3, 6D4, 7B4 and 6F8 detected both cytohesin-1 and ARNO as monitored by immunoblotting. Although mAb 6G11 detected both proteins, this antibody immunoprecipitated GFP-ARNO but not GFP-cytohesin-1 under native conditions. Another antibody, mAb 10A12, also selectively immunoprecipitated GFP-ARNO under native conditions, but the epitope recognized by this mAb is unlikely to be linear as no signal was obtained by immunoblotting. Immunoprecipitation with a cytohesin-1 polyclonal antibody and blotting with cytohesin-1 specific mAbs revealed that cytohesin-1 is highly expressed in neutrophils. Cytohesin-1 can be detected in HL-60 cells but the endogenous protein levels were low in undifferentiated cells. Using the specific cytohesin-1 mAb 2E11 we observed a marked increase in levels of cytohesin-1 expression during dibutyryl-cyclic AMP-induced granulocytic differentiation of HL-60 cells. These data suggest that cytohesin-1, which may have important functions in neutrophil physiology, can be useful as a potential marker for granulocytic differentiation.

Differential expression and regulation of thyrotropin (TSH) in T cell lines.

The immune system's production of and response to thyrotropin (TSH) suggests the existence of a hypothalamic-lymphoid-thyroid regulatory axis (HLT). To evaluate the possible roles of lymphocyte-derived TSH we characterized its structure and regulation of production. Using an in vitro system, we screened T cell lines for the production of TSH in response to thyrotropin-releasing hormone (TRH). We identified MOLT 4 T cells as producers of intact TSH based on TSH radioimmunoassay (RIA) displacement and de novo synthesized protein structure similar to pituitary TSH. Northern blot analysis using a cDNA probe to TSH beta showed the existence of an mRNA species similar in molecular size to pituitary mRNA of TSH beta. The MOLT 4-derived TSH is induced in a dose-dependent fashion by TRH and that induction is significantly inhibited by the thyroid hormone, triiodothyronine (T3). HUT 78 T cells express an mRNA species similar to TSH beta but do not express detectable protein suggesting a lack of translation of the mRNA species. The evidence suggests that the MOLT 4 T cells serve as an in vitro model for TSH production and may be used to study differential expression of the genes for TSH in the immune system. Elucidation of this in vitro system will provide information on mechanisms of regulation of an HLT axis that are unique to the immune system as well as pathways common to the immune and neuroendocrine systems.

Glucocorticoids in malignant lymphoid cells: gene regulation and the minimum receptor fragment for lysis.

We have examined clones of human malignant lymphoid cells for markers that correlate with glucocorticoid-mediated cell lysis. In glucocorticoid-sensitive clones of CEM, a human T-cell lymphoblastic leukemia line, two genes correlate with glucocorticoid-induced cell lysis. The glucocorticoid receptor (GR) itself is induced by standard glucocorticoids in sensitive clones and not in insensitive clones. The phenylpyrazolo-glucocorticoid cortivazol (CVZ) is capable of lysing several clones resistant to high concentrations of standard potent glucocorticoids. When these clones were tested for cortivazol responses, they were not only lysed by cortivazol but also showed induction of GR mRNA. Thus receptor induction appears to correlate with the lysis function of receptor in these cells. To determine what parts of the GR are required for lysis, we have mapped this function by transfecting and expressing GR and GR fragment genes in a GR-deficient CEM clone. Our results indicate that none of the known trans-activation regions of the GR are required. Removal of the steroid binding domain gives a fragment that is fully constitutive. Only one and one-half "Zn fingers" of the DNA binding region are required. We also find in CEM cells rapid suppression of the c-myc protooncogene, preceding growth arrest and cell lysis by glucocorticoids. This occurs only in clones possessing both intact receptors and lysis function. Thus the simple presence of GR alone is not sufficient to guarantee c-myc down-regulation. Introduction into the cells of c-myc driven by a promoter that does not permit suppression by glucocorticoids confers resistance to steroids. Furthermore, suppression of c-myc by antisense oligonucleotides also kills the cells. Therefore, c-myc appears to be a pivotal gene related both to ability of steroid to kill and to cell viability.

Methods for detection of haematogenous dissemination of brain tissue after stunning of cattle with captive bolt guns.

Because of concern that the stunning of cattle with captive bolt guns (CBGs) could, if used on an animal with bovine spongiform encephalopathy (BSE), cause embolism of infective brain tissue and carcass contamination, the Ministry of Agriculture, Food and Fisheries commissioned research to assess the risk of haematogenous dissemination of CNS material after stunning. We have devised two methods to investigate this risk. The first involves the concentration of embolic tissue in buffy coat Cytoblocks that can be embedded for sectioning, microscopy and immunocytochemistry. The second method is an ELISA for the presynaptic protein, syntaxin 1B. The methods were validated by analysis of several bovine tissues, including blood samples deliberately contaminated with brain. We then studied jugular venous blood obtained before and after the stunning of 60 cattle with CBGs. Samples obtained, after stunning, from five of the cattle contained CNS tissue within the Cytoblocks and yielded positive syntaxin assays. Syntaxin was also detected in samples from one other animal that had been stunned with a pneumatically operated CBG. The described methods should allow an assessment of the risk of neuroembolism associated with different types of CBG and may also be useful in other contexts.

The application of polymerase chain reaction to the detection of rotaviruses in faeces.

An assay protocol based on exploiting the polymerase chain reaction (PCR) for the detection of rotavirus in infected faeces is described. The assay is 100,000 times more sensitive than the standard electropherotype method that is widely used. It also gives a 5000-fold increase in sensitivity over the hybridisation based assay previously developed (Pedley and McCrae, 1984) and does not require the use of radioisotopes. The amplified product is a full length c-DNA copy of the gene encoding the major neutralisation antigen of the virus whose molecular cloning and sequence analysis will allow detailed information on the molecular basis of epidemiological variation to be rapidly collected.

Mucosal infection and vaccination against feline immunodeficiency virus.

Feline immunodeficiency virus (FIV) infection is a naturally occurring lentiviral infection of cats which progresses to immunodeficiency in a manner strikingly similar to that observed in HIV infection in man. The rectal and cervico-vaginal mucosae are common routes of transmission of HIV and it has been shown that the gastrointestinal tract is an important site of HIV infection and primary pathology. Although biting is the principle mode of transmission for FIV, we have shown that it is possible to reliably infect cats via both the rectal and vaginal routes. Using a biotin-streptavidin linked immunoperoxidase technique we have detected FIV core and envelope proteins in the colonic follicle associated epithelial cells, cells within the lymphoid follice and occasional cells in the lamina propria. Further, in the intestine we have detected FIV RNA and proviral DNA in epithelial cells, colonic lymphoid aggregates and isolated lamina propria cells. We have studied a group of asymptotic cats which have been rectally infected with FIV for 1 year or longer and shown an increase in the number of lamina propria CD8+ cells and greater levels of IL-2, IL-6, IL-10 and gamma-IFN mRNA. Since these cats remained clinically healthy these results might suggest that both local antibody and class I restricted cytotoxic lymphocytes (CTLs) may play a role in control of viral replication. We have investigated a range of vaccination regimes for their ability to generate responses which would protect from rectal challenge with virulent virus. Cats have been immunized with whole virus (FIV-pet, FIV-GLA-8), V3, V3MAP or C2 with cholera toxin (CT), or Quil A based adjuvants via rectal, intra-nasal, parenteral or targeted lymph node routes, and challenged rectally with ten mucosal cat infectious doses (MCID) of FIV-GLA-8. We have shown that the adjuvant effects of cholera toxin and Quil A are not influenced by the route of delivery (intraperitoneal (i.p.) versus rectal) with CT more effective in stimulating humoral and Quil A more effective in stimulating cellular responses to FIV antigens. However we have shown that, quantitatively, CT is more effective when used as an adjuvant via the intra-nasal than the rectal route. Recently, we have begun to investigate if the promising results obtained with targeted lymph node (TLN) vaccination in monkeys could be reproduced in the cat. We have shown that TLN was more effective than rectal immunisation in stimulating both humoral and proliferative responses. In a preliminary study we have also been able to detect FIV specific CTLs and have observed protection from rectal challenge in four out of four cats.

PCR-based 16S ribosomal DNA detection technique for Clostridium estertheticum causing spoilage in vacuum-packed chill-stored beef.

Chill stored vacuum-packaged meat is sometimes spoiled by psychrotrophic or psychrophilic clostridia. Clostridium estertheticum was first isolated from vacuum-packed beef from southern Africa, but has recently been found in beef originating from northern Europe. This organism is difficult to isolate using conventional methods, and two PCR-based methods have been devised for use in measures to control the bacterium in the abattoir and to study its ecology. In the first method, primers were designed having a high annealing temperature of 65 degrees C to increase specificity, producing a PCR product of 567 bp from the 16S rDNA. Two species of Enterobacteriaceae found in meat cross-reacted in this test, and so it was necessary to use a second step, digesting the PCR product with two restriction enzymes. Subsequently a further set of primers was designed, producing a PCR product of 641 bp, and using an annealing temperature of 60 degrees C. The second procedure was more specific and did not require subsequent restriction analysis of the PCR product. The two sets of primers appeared to have similar sensitivity, detecting 10-100 cells of C. estertheticum in broth, meat or meat purge (drip). A semiquantitative method is described for estimating numbers of the target bacterium.

Reovirus type 2 in domestic cats: isolation and experimental transmission.

Five reovirus isolates were recovered in MA104 cell cultures from the faeces of three cats with nictitating membrane protrusion and diarrhoea, one cat with diarrhoea only and from one healthy cat. Four of these isolates were characterised as reovirus type 2 and one as reovirus type 3 by haemagglutination-inhibition and serum neutralization tests. Reovirus type 2 has not been reported previously in cats. Mild clinical signs of diarrhoea were noted in kittens infected experimentally with one of the feline reovirus type 2 isolates.

Detection of feline coronaviruses by culture and reverse transcriptase-polymerase chain reaction of blood samples from healthy cats and cats with clinical feline infectious peritonitis.

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the detection of the feline coronavirus (FCoV) genome and a co-cultivation method for the isolation of field strains of FCoV are described. Using the RT-PCR assay to assess blood samples from cats with feline infectious peritonitis (FIP) (n = 47) and healthy cats from households with endemic FCoV (n = 69) it was shown that approximately 80% of the cats were viraemic, irrespective of their health status. It was also shown that, over a 12-month period, a similar percentage of healthy cats remained viraemic, and that the presence of viraemia did not appear to predispose the cats to the development of FIP. The co-cultivation system proved to be a suitable method for the culture of field strains of FCoV from blood samples, so long as the cultures were maintained for at least 4 weeks. Using this system, followed by the RT-PCR, viraemia was detected as frequently as by RT-PCR on RNA extracted directly from peripheral blood mononuclear cells.

Virus shedding and immune responses in cats inoculated with cell culture-adapted feline infectious peritonitis virus.

Eight specific pathogen-free cats were inoculated orally or parenterally with a cell culture-adapted strain of feline infectious peritonitis virus (FIPV). Faeces and oropharyngeal swabs were monitored daily for infectious virus by inoculation of feline embryo lung cells. Virus was recovered from both sites for approximately 2 weeks after inoculation, before clinical signs of disease developed. Peripheral blood lymphocytes collected from these cats were tested in an in-vitro blastogenic assay using concanavalin A (con A) and FIPV antigen. All cats showed a profound suppression of the response to con A which only recovered to pre-inoculation levels in 2 cats, one of which survived. These 2 cats also responded to FIPV antigen on the 21st day after infection, the greater response being in the survivor. The other cats, surviving 16-18 days, developed no response to FIPV antigen. Antibody titres, measured by immunofluorescence and by virus neutralization, rose rapidly to very high levels in all cats, regardless of the route of inoculation.

The sites of early viral replication in feline infectious peritonitis.

The sites of early replication of feline infectious peritonitis virus were studied following oral inoculation of specific-pathogen-free (SPF) cats with virus grown in cell cultures. Viral antigen was first detected by immunofluorescence in the tonsils and small intestine within 24 h of inoculation, and was later found in caecum, colon, mesenteric lymph nodes and liver. However, histological changes in the gut did not appear until relatively late in the course of infection. Virus was recovered from the oropharynx and the faeces from as early as the second or third day after inoculation, and shedding continued until euthanasia.

Polymerase chain reaction and partial sequencing of a British isolate (T637) of feline immunodeficiency virus.

We have used the polymerase chain reaction (PCR) and direct sequencing of the amplified products to obtain information of the molecular nature of an FIV isolate, T637. Cats experimentally infected with T637 have progressed to clinical immunodeficiency disease. The 5' long terminal repeat (LTR), most of the genes coding for internal proteins (GAG) and surface proteins (ENV), and part of the polymerase (POL) gene have been sequenced. The LTR of T637 has 92% nucleic acid identity with the prototype strain, FIV-Petaluma and the Glasgow isolate, FIV-14, 89% with a Swiss isolate, FIVZ2, and 95% with the PPR isolate. Both GAG and POL genes of T637 share extensive homology with Petaluma and PPR. In the ENV gene, T637 has 91% nucleic acid homology with Petaluma and 86% with PPR, and an overall amino acid homology of between 81-87%. For the surface (SU) region of the ENV gene product, T637 has 89% amino acid homology with Petaluma and FIVZ2 and 86% with PPR.

Vaginal and rectal infection of cats with feline immunodeficiency virus.

The objective of this study was to examine the potential of vaginal and rectal mucosal routes for feline immunodeficiency virus (FIV) uptake and infection, as a model of mucosal HIV infection, and to determine the fate of virus at these mucosal sites following transmission of infection. SPF cats were exposed to FIV isolates (PET, GL-8, T637), administered as either cell-associated or cell-free inocula, via the rectum or vagina. Establishment of infection was confirmed by isolation of infectious FIV from peripheral blood mononuclear cells (PBMC), and by presence of FIV proviral DNA in PBMC using a nested polymerase chain reaction. Fate of virus in tissue taken at necropsy from cats infected for 6-48 weeks was assessed by localizing FIV core and envelope proteins, p24 and gp41, using a biotin-streptavidin linked immunoperoxidase (IP) technique. Cells susceptible to infection were identified by an in situ hybridization technique for FIV viral DNA and RNA. Cell-free, as well as cell-associated, virus was infectious across intact vaginal and rectal mucosal surfaces. Transmission was most successful using cell-associated inocula, and via the rectal route. Cells infected with FIV were detected by IP staining in the colon of 6/9 rectally challenged cats and 1/5 vaginally challenged cats. Virus was predominantly localized within the epithelium at the base of the colonic crypts associated with lymphoid aggregates (follicle associated epithelium; FAE), and within the lymphoid follicle itself. Occasional infected cells were also noted within the lamina propria. The distribution of FIV DNA positive cells in the colon was similar to that for FIV antigen whilst FIV RNA positive cells were found more extensively, including within the lamina propria and lymphoid follicle. FIV infected cells were not detected within the vagina, or colonic and ileac lymph nodes. Similar patterns of infected cells were seen in all of the positive cats, indicating that colonic tissues remain persistently actively infected with FIV. We conclude that the FIV/cat model of rectal and vaginal mucosal infection should prove useful for characterizing the mechanism by which HIV infects mucosal surfaces and as a challenge system for the design of vaccines effective at preventing HIV infection via rectal and vaginal routes.

16S rDNA comparison demonstrates near identity between an United Kingdom Haemobartonella felis strain and the American California strain.

A handful of North American (USA) strains of the uncultured erythrocytotrophic pathogen of cats, Haemobartonella felis, have been differentiated by comparison of the 16S rRNA gene sequences. Using this approach, an UK strain was characterised, providing an identity for a non-USA H. felis for the first time. This strain shared close phylogenetic homology with the USA Californian strain.

Comparison of antibody and cell-mediated immune responses in horses following feeding of a novel dietary antigen, ovalbumin, and rotavirus.

Adult ponies which were fed ovalbumin (OVA) daily for 2 weeks had significantly greater serum anti-OVA IgG (P = 0.001) and antigen specific lymphocyte responses (P = 0.031) after intramuscular injection with OVA given with saponin than control ponies which had not been fed the antigen. This suggests that, despite the lack of evidence of B- or T-cell activation in peripheral blood during the period of OVA feeding, the animals were primed for an active secondary immune response. Adult ponies were challenged with equine rotavirus, strain H-2, but no statistically significant differences were found in serum IgG-associated antibody responses or antigen-specific lymphocyte responses between the rotavirus-challenged group and the control group, either following rotavirus challenge or intramuscular injection of rotavirus antigen given with saponin. Our findings, that feeding the non-replicating protein antigen OVA appeared to prime for an increased immune response rather than inducing oral tolerance, may be of relevance to future studies on the way the equine gastrointestinal tract handles usually harmless antigens.