It has been observed that adults and children have differences in their susceptibility to schistosome infection and reinfection. The relative importance of the various factors that may influence age-dependent innate resistance and acquired immunity to schistosome infection is uncertain. In order to assess this, juvenile and adult female Fischer rats were exposed to primary and secondary infections of <i>Schistosomia mansoni</i>. In contrast to the adult rats, juveniles were found to be harbouring significantly more worms at day 21 post-infection. After reinfection, both groups were equally resistant to challenge. Similar age-dependent susceptibility to infection was observed in rat mouse infections with <i>Nippostrongylus brasiliensis.</i> The effect of host hormones was assessed on larval schistosomes. Testosterone (but not DHEAS) was found to be schistosomicidal <i>in vitro</i>. Antibody responses (antigen-specific IgG, IgG1, IgG2a, IgG2b and IgG2c) were found to be lower in juvenile animals after primary infection. No significant differences were observed in the relative levels of anti-carbohydrate antibodies to parasite antigens. Intra-cellular cytokine staining revealed juveniles to have a more Th1 dominated cytokine profile than adults. Immunisation of juvenile and adult rats with ovalbumin resulted in lower levels of antigen-specific antibody in the juvenile group, even after subsequent boosting whilst sexually mature. To provide an experimental bridge between rodents and humans, juvenile and adult female. Rhesus monkeys were infected with <i>S. mansoni.</i> Juvenile monkeys had higher worm burdens (non-significant) with greater tissue and faecal egg counts compared to adults. However, circulating schistosome antigens (CAA) were significantly greater in infected juvenile monkeys. PBMC production of IL-4 and IL-5 was lower in juvenile animals following primary schistosome infection, as were parasite-specific antibody responses (IgG, IgG2, IgM and IgA).

No description available.

Natural killer (NK) cells are known to be important for the control of viral infections, particularly infection with large double stranded (ds)DNA viruses such as herpes simplex virus type 1 (HSV-1) and vaccinia virus (VV), but the pathways and interactions important for NK cell recognition of virally infected cells are not well understood. Thus, the aim of this thesis was to study the molecular mechanisms of NK cell recognition of target cells infected with either HSV-1 or VV. Experiments using a set of HSV-1 mutants, deficient in one or more of the immediate early (IE) genes, demonstrated that expression of ICP0 alone was found to be sufficient to render HSV-1 infected target cells susceptible to NK attack, and killing assays demonstrated that the natural cytotoxicity receptors (NCRs) were involved in the NK mediated killing of HSV-1 infected targets. For VV, it was not possible to narrow down exactly which VV gene was sufficient for generating NK cell mediated susceptibility, but the data indicated that the VV gene or genes involved are expressed early, conserved within the poxvirus family, and as such, likely to be essential for the virus. Flow cytometry experiments demonstrated that altered susceptibility of the target cells to NK cell lysis was due to upregulation of ligands for the NCRs, and the importance of the NCRs in NK mediated killing of VV infected targets was confirmed by killing assays. In addition, flow cytometry experiments demonstrated very little down regulation of MHC class I followed infection by either HSV-1 or VV, implying that MHC class I down regulation is not of major importance in NK mediated killing of infected cells.

No description available.

No description available.

Awareness of the Bacteroidaceae as important members of the normal human flora and as pathogens has increased dramatically in recent years. Classification, however, has been confused and the identification of isolates difficult. In particular, the role of pigment production in the classification of Bacteroides spp. was debated. The aims of this investigation were (i) to study the classification of Bacteroidaceae with specific reference to pigment production by B. melaninogenicus; (ii) to examine conventional bacteriological tests for the characterization and identification of clinically important gram-negative anaerobic bacilli; and (iii) to apply these methods to the study of Bacterosdes spp. isolated from the normal human flora and from infections. In studies on pigment production, B. melaninogenicus strains produced a characteristic pigment when grown on media containing blood. The pigment was extracted by ultrasonic disintegration of washed cells of strains of B. melaninogenicus grown in blood broth and on blood agar. It was intra-cellular or cell-associated, soluble in water and had the spectrophotometric characteristics of a derivative of haemoglobin. No such pigment was extracted from strains of B.fragilis, F.necrophorum and Cl. clostridiiforme. The pigment was unrelated to the dense black colloidal precipitate of ferrous sulphide that resulted from the production of H2S by Bacteroides spp. and facultative species in the presence of ferrous ions. However, the pigment-producing strains were not a homogeneous species and were divided into three subgroups: B. melaninogenicus ss. melaninogenicus, ss. intermedius and ss. asaccharolyticus. A scheme for the identification of unknown isolates of Bacteroides spp, was devised following studies in which 165 reference strains and laboratory isolates were subjected to a series of simple laboratory tests that included conventional biochemical and fermentation tests, tests for resistance to antibiotics, and tolerance of dyes and bile salts. These tests allowed a clear separation of strains into three main groups - B.fragilis, B.melaninogenicus and Pusobacterium spp. - and certain tests were useful for identifying the subspecies of B. fragilis and B. melaninogenicus. The classification of B. melaninogenicus and related species was further studied in a series of tests with 175 strains of B. melaninogenicus, 17 strains of B. oralis and 6 strains of B. ochraceus. The pigmented asaccharolytic strains formed a distinct group and have been assigned a separate species - B. asaccharolyticus. B.melaninogenicus ss. intermedius strains formed a homogeneous group. B. ochraeceus was distinguished from other Bacteroides spp. by its ability to grow in air plus 10% C02 and its resistance to metronidazole; it is suggested that it should be removed from the genus Bacteroides. B.melaninogenicus as. melaninogenicus and B. oralis gave similar patterns of results and were often indistinguishable except for the production of pigment by B. melaninogenicus strains. The following system of classification was derived after studies with additional reference and referred strains. The Bacteroidaceae were divided into 4 main groups - B.fragilis group, B. melaninogenicus/oralis/ruminicola group, asaccharolytic group and Fusobacterium group. The B.fragilis group comprised the 5 subspecies of B.fragilisi that have been reinstated to species rank - B. fragilis, B. vulgatus, B. distasonis, B.thetaiotaomicron and B.ovatus - and several related species - B. splanchnicus, B. eggerthii, B. uniformis and B. variabilis. The B. melaninogenicus/oralis/ruminicola group contained the 2 saccharolytic subspecies of B. melaninogenicus, as. melaninogenicus and as. intermedius, a weakly fermentative subspecies - as. levii, and 4 non-pigmented specie's - species B.bivius, B.disiens and B.ruminicola. Bs oralis and B.melaninogenicus as. melaninogenicus strains share many characteristics and it is suggested that pigment production might not .be a valid criterion for their separation. The asaccharolytic group included'B.asaccharolyticus, B.corrodens and non-pigmented strains that were not further identified, and the:Fusobacterium group was represented by reference strains of F.polVmorphum, F.varium, F.necrogenes, F.necrophorum and L.buccalis. These species were identified by a combined set of 'tolerance tests with taurocholate, deoxycholate, Victoria blue 4R and ethyl violet, antibiotic disk resistance tests with neomycin 1000pg, kanamycin 1000pg, penicillin 2 units and rifampicin l5pg, pigment production and biochemical tests for indole production, gelatin digestion, aesculin hydrolysis and the fermentation of glucose, lactose, sucrose, rhamnose, trehalose, mannitol and xylose. Strains were allocated to the appropriate group by the results of the tolerance and resistance tests and to species/subspecies level by the results of biochemical and fermentation tests.The scheme was evaluated satisfactorily in studies with Bacteroides strains isolated from the normal human flora and clinical infections. Specimens of faeces, vaginal secretions and sub-gingival plaque were obtained from 20 normal healthy adults. A heavy growth of Bacteroides spp. was' obtained from all specimens of faeces and 10 colonies were selected from each subject for identification. Most (84%) isolates belonged to the B.fragilis group. The commonest species/subspecies were B.fragilis as. vulgatus and as. thetaiotaomicron (22% of B.fragilis-group isolates each 5, Ss distasonis (18%) and the B.eggerthii/variabilis group (14%). B.fragilis ss. fragilis accounted for only 9% of B.fragilis-group isolates. Bacteroides spp. were recovered from 65% of vaginal specimens. Most (78%) isolates belonged to the B. melaninogenicus/oralis/ruminicola group and the commonest species/subspecies were B. bivius/disiens (42% of the group isolates) B. melaninogenicus as. melaninogenicus (16%) and as. intermedius (22%). Only 6 B.fragilis strains were identified and 5 were from a single subject. A heavy growth of Bacteroidaceae was obtained from all specimens of sub-gingival plaque; 68% of isolates were members of the B. melaninogenicus/ oralis/ruminicola group. B.oralis (42% of the group isolates), B.melaninogenicus as. melaninogenicus (26%) and ss I'ntermedius (17%) were the commonest species. Fusobacterium spp. and L.buccalis were common isolates from sub-gingival plaque and accounted for 36 isolates,In studies of the role of Bacteroides spp. in infections, 399 significant isolates were obtained from 356 specimens from 332 patients. A variety of species were identified; the B.fragilis group accounted for 261 isolates and there were 55 isolates of B.asaccharolyticus. Many (68%) were from infections related to the gastro-intestinal tract but others were from gynaecological, soft tissue and a variety of other infections. B.fragilis ss. fragilis accounted for 51% of-all isolates and 78% of B.fragilis-group isolates, which indicates that this subspecies has particular pathogenic potential, not only in infections-derived from the gastro-intestinal tract. The Bacteroides app. were isolated in pure culture from only 26% of the infections, 73% were mixed infections with Bacteroides spp. and facultative organisms that may act synergistically.Bacteroides spp. can be identified by a simple set of conventional bacteriological tests that can be performed by any diagnostic laboratory. These studies have shown that different species are predominant in the normal flora of the mouth, faeces and vagina and that a number of species, particularly B.fragilis as. fragilis, form only a minor part of the normal flora but are the commonest pathogens.

No description available.

No description available.

Malignant catarrhal fever (MCF) is a fatal lymphoproliferative disease affecting ruminants. The disease is caused by infection of susceptible hosts with one of two gammaherpesviruses, <I>Alcelaphine Herpesvirus</I>-1 (AHV-1) or <I>Ovine Herpesvirus</I>-2 (OHV-2). On isolation AHV-1 infectivity is cell-associated and will induce MCF on inoculation into experimental animals. After serial passage cell-free infective virus is observed, but this virus cannot produce MCF experimentally. The aim of this project was to characterise the genomic alterations which occurred in one isolate, C500, associated with this altered pathogenicity. Viral DNA of virulent (PP) and cell-free attenuated (CFA) C500 derivatives was compared by restriction endonuclease profiling. Variability was observed using Sma I, as a 5kbp fragment was present in PP DNA but not CFA DNA. Conversely a 3.8kbp fragment was present in CFA DNA but absent from PP DNA. Homology was observed between these Sma I fragments. The Sma I 3.8kbp fragment was cloned (ATT-1), as were two Hind III equivalents of the PP 5kbp Sma I fragment (VIR-1 and VIR-2). These clones were mapped for several restriction endonucleases, subcloned and sequenced. The location of the C500 clones was assessed by Southern blotting and PCR. The structure of the C500 genome consisted of a central unique region of approximately 130kbp, flanked on either side by multiple copies of a 1-5-kp repeat unit, resulting in an overall genome size of 160kbp. The ATT-1 clone was found to be present twice in the CFA genome, located at both ends of the unique region, close to the terminal repeats, with both copies orientated in the same direction. The location of the VIR-1 and VIR-2 clones in the PP genome was not fully determined during this study, however, the results obtained suggested that VIR-1 and VIR-2 clones were located approximately 1.4kbp apart, at one end of the unique region, close to the terminal repeats.

No description available.