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Biomedical subjects

M Ristic

Publications and source records attributed to M Ristic.

At least 55 records · Page 3Linked to original sources
PubMed1985

Heterologous strain immunity in bovine babesiosis using a culture-derived soluble Babesia bovis immunogen.

The cross-protective capacity of culture-derived soluble immunogens against heterologous Babesia bovis strains from different geographical locations of Latin America was examined. Susceptible yearling cattle were either immunized with immunogens derived from Venezuelan or Mexican strains, or were administered a multi-component immunogen containing antigens of the Australian, Mexican and Venezuelan strains. Cattle were challenged with virulent B. bovis organisms of the Argentinian, Colombian, Ecuadorean, Mexican and Venezuelan strains. The major parameters used to evaluate cross-protection were the following: presence, level and duration of parasitemia; maximal PCV reduction; level and duration of fever; determination of fibrinogen and cryofibrinogen; homologous and heterologous antibody levels; and net gains in body weight. Results showed good protection with a Venezuelan B. bovis immunogen after homologous and heterologous challenge exposures. A low degree of cross-immunity was observed when cattle vaccinated with the Mexican immunogen were challenged with each of the heterologous strains.

Animals↗
PubMed1985

Adaptation of Ehrlichia sennetsu to canine blood monocytes: preliminary structural and serological studies with cell culture-derived Ehrlichia sennetsu.

Ehrlichia sennetsu, the causative agent of human sennetsu rickettsiosis, was successfully propagated in primary canine blood monocyte cultures. The growth cycle of this organism appears to be similar to that of Ehrlichia canis. The antigen derived from our E. sennetsu cultures was used to develop an indirect fluorescent antibody test for detection and titration of serum antibodies to the organism. Using this test system, we found that five human serum samples obtained from patients clinically diagnosed as having sennetsu rickettsiosis were positive for anti-E. sennetsu antibodies. In addition, 29% of the serum samples obtained from 200 patients having a fever of unknown origin and residing in various regions of Malaysia were also serologically positive. All sera from apparently healthy individuals were negative in the test. Dogs inoculated with cell culture-adapted E. sennetsu developed a significant specific antibody titer to E. sennetsu, and the organism was subsequently isolated from their blood. These animals showed no clinical evidence of disease. The possibility of a higher prevalence of human sennetsu rickettsiosis in Southeast Asia and the potential usefulness of the canine model for studies of human sennetsu rickettsiosis are discussed.

Animals↗
PubMed1985

Induction of protective immunity to Plasmodium falciparum in Saimiri sciureus monkeys with partially purified exoantigens.

Soluble Plasmodium falciparum exoantigens in crude culture supernatant fluids induced protective immunity against experimental falciparum malaria in Bolivian Saimiri sciureus monkeys. Susceptible squirrel monkeys were vaccinated with an aluminum hydroxide-fortified fraction purified from culture supernatants of P. falciparum Indochina I and Geneve/SGE-1 by cation-exchange (sulfopropyl-trisacryl) chromatography. Animals immunized with sulfopropyl-purified and corresponding control immunogens were challenged with whole blood containing monkey-adapted virulent organisms of the Indochina I strain. Hematological, serological, and parasitological profiles, including the appearance of crisis forms, served as potential indicators of protection. This immunogen conferred significant clinical protection of squirrel monkeys against needle challenge with the homologous Indochina I strain and a moderate degree of heterologous strain immunity.

Animals↗
PubMed1985

Growth inhibition of Babesia bovis in culture by secretions from bovine mononuclear phagocytes.

Bovine blood mononuclear phagocytes from babesia-free cattle were cultured in vitro. Cell monolayers were treated with culture-derived soluble Babesia bovis exoantigens, immune complexes, and bovine anti-B. bovis immune serum. Subsequently, the monolayers were washed free of the reagents and allowed to develop further in the presence of standard culture medium. Transfer of supernatant media from these cultures to those of B. bovis revealed the presence of growth-inhibiting factors. These factors were thermostable, nondialyzable, and were degraded by freeze-thawing, and their action was concentration dependent. Supernatants from antigen- and immune complex-treated monolayers demonstrated greater inhibitory effects than did supernatants from antibody-treated or untreated monolayers. Erythrocytes incubated with supernatant medium from antigen-treated monolayers did not support growth of B. bovis as well as did erythrocytes incubated with supernatants from untreated monocyte monolayers. This result suggests that the mechanism of action of soluble factors could be through some modification of the erythrocyte such as the blockage of active transport of essential nutrients.

Animals↗
PubMed1985

Hematologic values of normal Bolivian squirrel monkeys (Saimiri sciureus): a comparison between wild-caught and laboratory-bred male animals.

Complete and differential blood counts were conducted on 23 male squirrel monkeys (Saimiri sciureus) of Bolivian origin. The sample included 9 laboratory-bred and 14 wild-caught adult monkeys weighing between 600 and 1,500 g. The means of total white blood cell (WBC) counts, total hemoglobin and hematocrits of laboratory-bred animals were found to be significantly different from those of wild-caught monkeys (p less than 0.01). Other hematologic parameters showed no significant differences between the two experimental groups. 3 of 14 (21.0%) wild-caught animals each had 1 reactive lymphocyte and 7% of the same group had 10 nucleated erythrocytes per 100 WBC. No reactive lymphocytes or nucleated erythrocytes were observed in laboratory-bred animals. The importance of these baseline data and the basis for the differences observed between laboratory and wild-caught monkeys are discussed within the context of experimental studies involving primates in which hematologic parameters are valuable.

Animals↗
PubMed1985

Structural alteration of the membrane of erythrocytes infected with Babesia bovis.

Babesia bovis, causative agent of cattle babesiosis, induces characteristic alterations on the membrane of infected erythrocytes. Elliptical protrusions measuring about 320 nm in long axis and about 160 nm in short axis appear on the membrane of infected erythrocytes, both in vitro and in vivo. Freeze-fracture demonstrated alignment of intramembrane particles (IMP) along the long axis of both the P and E faces of the protrusions. The number of IMP on the endoplasmic face increases, but the number of IMP on the protoplasmic face of the protrusions is not statistically altered from that of uninfected erythrocytes. In vitro, there are more protrusions per erythrocyte infected with the virulent form (low passage form) of B. bovis than with the avirulent form (high passage form). This suggests that the number of protrusions which appear on the membrane of infected erythrocytes may have a direct relationship to the virulence of the parasites. These protrusions may be attached to the capillary endothelial cells, which causes fatal cerebral babesiosis.

Animals↗
PubMed1985

Continuous propagation of Ehrlichia sennetsu in murine macrophage cell cultures.

Ehrlichia sennetsu, the etiologic agent of human sennetsu rickettsiosis was successfully propagated in a continuous cell culture using murine cell lines P388D1 and Raw 264. Pleomorphic cytoplasmic inclusion bodies similar to Ehrlichia canis morulae were observed 3-4 days after second post-inoculation split. In the Raw 264 cell line E. sennetsu was not seen until the third passage. Relatively heavier infection was observed in P388D1 than in Raw cell line. The latter reached a maximum of 15% infection whereas P388D1 cell line attained saturation. Structural details of the organism were confirmed by electron microscopy. A unique rippled cell mass surrounding the plasma membrane was observed. Supernatants of cultures were shown to contain infectious organisms. The advantages of propagating E. sennetsu in continuous cell lines are discussed with respect to future physiochemical and immunochemical studies of this organism.

Animals↗
PubMed1984

Antigen beads: a novel approach for the delivery of a soluble Anaplasma immunogen.

An important consideration in the development of effective immunization regimens against bovine anaplasmosis is the optimization of vaccine delivery systems. This report describes the formulation of proteinaceous antigen-containing spheres derived from supernatant fluids of Analplasma marginale cultures. The antigen beads were designed for use as potential dispersal agents for a soluble Anaplasma immunogen. Immunospecificity assays demonstrated that A marginale antigen was located on the surfaces of individual antigen beads. Use of Anaplasma antigen beads with a potent adjuvant, such as saponin, was proposed.

Adjuvants, Immunologic↗
PubMed1983

Localization of culture-derived soluble Babesia bovis antigens in the infected erythrocyte.

Immunoprecipitates derived from crossed immunoelectrophoresis of Babesia bovis culture supernatant fluid against a polyspecific anti-B. bovis serum were used to produce monospecific rabbit antibodies to individual B. bovis antigens. These antibodies were utilized in an immunofluorescence test to identify the location of the respective antigens within the infected erythrocyte. Two antigens were found on or near the erythrocyte membrane, while a third antigen was directly associated with the parasite itself.

Animals↗
PubMed1983

Cell culture-derived Babesia bovis vaccine: sequential challenge exposure of protective immunity during a 6-month postvaccination period.

Cell culture-derived soluble Babesia bovis vaccine admixed with a saponin adjuvant was administered in 2 doses, 3 weeks between doses, to 18 yearling heifers. An additional 9 heifers served as nonvaccinated controls. Comparable groups of these animals were challenge exposed at 131 and 178 days after vaccination, using 1 X 10(8) B bovis organisms contained in freshly collected blood from a splenectomized calf with ascending parasitemia. Challenge exposure led to no deaths of vaccinated animals, whereas 4 of the control (nonvaccinated) animals died of disease. All clinical and hematologic variables examined indicated that the vaccinated animals had gained immunologic protection in comparison with the control group. An immune recognition as manifested by an anamnestic humoral response to challenge exposure was in evidence in the vaccinated animals.

Animals↗
PubMed1982

Distribution of Ehrlichia canis among military working dogs in the world and selected civilian dogs in the United States.

Antibodies to Ehrlichia canis were detected by indirect immunofluorescence in sera from 233 of 2,077 (11%) military working dogs in various locations throughout the world and from 535 of 938 (57%) civilian dogs in the United States during a 1-year period of study. Overall, E canis infection rates ranged from 13% in the tropical and temperate zones below 45 degrees N to 8% in the cold zone north of 45 degrees N latitude. The highest antibody prevalence rate (24%) was found among a select population of dogs stationed between 40 degrees and 45 degrees north latitude (Japan and Okinawa). The seropositive military dogs did not have clinical signs of ehrlichiosis, thus indicating that the predominant form of infection was subclinical. On the other hand, 216 (23%) of the seropositive civilian dogs had various signs of the disease. The difference was attributed to the fact that the sera from civilian dogs were submitted by practitioners who suspected the disease.

Animals↗
PubMed1982

Antigenic and immunogenic studies on cell culture-derived Babesia canis.

Babesia canis antigens derived from cell culture reacted specifically with immune serum from dogs convalescing from babesiosis. The antigens were heterogenous as compared to antigens elaborated in vivo. The major antigenic moiety from cell culture eluted in the first peak of Sephadex G-200 is indicative of a molecular weight around 900 000. In contrast, in vivo-derived antigen coeluted with albumin and hemoglobin suggesting a molecular weight of 67 000. The major antigenic mass is proteinacious and contains disulfide bonds as indicated by thermolability and sensitivity to 2-mercaptoethanol. Both particulate and soluble B. canis antigens were immunogenic, particularly when emulsified in Saponin as an adjuvant. Such antigens conferred a considerable degree of protection in Saponin as an adjuvant. Such antigens conferred a considerable degree of protection in susceptible dogs and it suggested that immunoprophylaxis to B. canis may be feasible.

Adjuvants, Immunologic↗
PubMed1982

Rickettsia sennetsu in human blood monocyte cultures: similarities to the growth cycle of Ehrlichia canis.

Microscopic examination of cultured human monocytes infected with Rickettsia sennetsu and stained by the Giemsa method revealed the presence of various organismal growth forms in the cytoplasm of the infected cells. The growth forms were loosely scattered individual organisms, clusters of organisms, various sizes of dense inclusion bodies in intact and vacuolated cytoplasm, and organisms in close proximity to disintegrated monocytes. The appearance and the morphology of these R. sennetsu growth forms were similar to those of Ehrlichia canis propagated in canine monocytes. Specific identification of R. sennetsu was made by staining cultured monocytes with fluorescein-conjugated globulins extracted from the pooled sera of patients recovering from sennetsu rickettsiosis. Mice infected with cultured R. sennetsu developed gross pathological changes indicative of infection, and the organism was demonstrated in their spleens, peritoneal macrophages, and mononuclear blood cells. Human monocyte culture appeared to be more sensitive than the previously used African green monkey kidney cell line (BSC-1) for the isolation of R. sennetsu from samples containing minute infectious quantities of this organism.

Animals↗
PubMed1982

Age resistance in bovine babesiosis: role of blood factors in resistance to Babesia bovis.

In vitro cultivation of Babesia bovis in erythrocyte cultures demonstrated that blood from young animals contains a factor(s) responsible for their resistance to severe babesiosis. This factor is independent of antibody, is present in the serum of all young animals tested, and is dialyzable. The presence of this factor results in inhibition of parasite multiplication and the eventual death of the parasite while inside the erythrocyte.

Aging↗
PubMed1982

Intestinal, pulmonary, and serum antibody responses of feeder pigs exposed to transmissible gastroenteritis virus by the oral and the oral-intranasal routes in inoculation.

Specific antibodies against transmissible gastroenteritis (TGE) virus produced as a result of oral and oral-intranasal viral exposure of feeder pigs were isolated by molecular sieve column chromatography of lung wash, intestinal fluid, and serum samples. Selected fractions were analyzed for neutralizing antibody activity. Oral inoculation gave a predominantly immunoglobulin (Ig) G antibody response in lung wash and serum, as compared with the response in intestinal fluid in which neutralizing antibody activity was found in the IgA-containing fractions. Oral-intranasal inoculation produced a predominantly IgA antibody response in intestinal fluid. Lung wash contained IgA and IgG antibody, and serum antibody consisted primarily of IgG class of Ig. Neutralizing antibody (IgA, IgG, IgM) from the lung wash, intestinal fluid, and serum samples persisted beyond 56 days after oral and oral-intranasal viral exposures. The virus-shedding period in feces was 1 to 7 days after oral or oral-intranasal inoculation of feeder swine with virulent TGE virus. However, TGE virus was reisolated from lung and intestinal tissue for as long as 42 and 56 days, respectively.

Animals↗
PubMed1982

Efficacy of a nonviable culture-derived Babesia bovis vaccine.

Tissue culture-derived soluble Babesia bovis antigens were combined with a saponin adjuvant and used to vaccinate 3 adult cows and 8 yearling heifers. Each animal was vaccinated twice at a 3-week interval between vaccinations. Two adult cattle were premunized with an attenuated B bovis. All vaccinated cattle and premunized cattle along with 3 nonvaccinated adult cattle and 8 nonvaccinated yearling heifers were challenge exposed 4 weeks after the 2nd vaccine dose by IM inoculation of an estimated 1 x 10(8) virulent B bovis organisms. Both vaccinated and nonvaccinated controls responded to challenge exposure, whereas the premunized cattle were refractory to challenge exposure. These cattle given the adjuvant-vaccine showed a significantly milder clinical response to infection. Death occurred in 2 of the 3 adult controls and 2 of the 8 yearling controls. Death losses or severe reactions were not seen among the vaccinated cattle. Vaccinated animals, before challenge exposure, failed to respond serologically to the complement-fixation test even though specific antibodies to B bovis antigens were detected with the indirect antibodies to B bovis antigens were detected with the indirect fluorescent antibody test. The apparent absence of isoimmunizing antigens and the ability to serologically distinguish vaccinated animals from infected animals are additional attributes which contribute to the potential usefulness of this vaccine.

Adjuvants, Immunologic↗
PubMed1982

Preservation of lyophilization of anaplasmosis capillary tube-agglutination test antigen.

An antigen for anaplasmosis capillary tube agglutination test was lyophilized, using different stabilizers. The lyophilized and control (suspension) antigens were maintained at 4, 18, and 37 C and tested for reactivity with known positive and negative sera once every 7 days for a period of 28 days and then once every 2 weeks for a grand total of 154 days. Both the lyophilized and control antigens retained their antigenicities during the entire test period.

Agglutination Tests↗