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Biomedical subjects

F M Collins

Publications and source records attributed to F M Collins.

At least 19 recordsLinked to original sources
PubMed1992

Effects of in vivo T lymphocyte subset depletion on mycobacterial infections in mice.

The relative importance of CD4+ and CD8+ T cell subsets in the expression of acquired resistance to systemic infection by Mycobacterium kansasii was determined. T cell subsets were depleted in thymectomized C57BL/6 mice by the intravenous administration of monoclonal antibodies directed against the relevant T cell determinants. Depletion of the CD4+ subset exacerbated the severity of the infection in intravenously challenged mice. This effect was apparent in the first 2 weeks of the infection and persisted throughout the 12 weeks of the study. On the other hand, depletion of the CD8+ cells had no apparent effect on the growth curves. Infections by Mycobacterium tuberculosis Erdman or bacille Calmette-Guérin (BCG) Pasteur were also substantially enhanced by CD4 depletion, but not by the depletion of CD8+ cells. The effect of subset depletion on infections by M. tuberculosis and BCG was examined in both innately susceptible C57BL/6 mice and innately resistant B6D2 mice.

Animals↗
PubMed1992

Immunization of mice with the antigen A60 of Mycobacterium bovis BCG.

Antigen 60 (A60) is a thermostable component of the cytoplasm of Mycobacterium tuberculosis and BCG which can be fractionated into at least 15 protein bands when analysed by Western blot. Normal B6D2 mice were immunized subcutaneously with 20 micrograms of the A60 protein suspended in Freund's incomplete adjuvant (FIA) or in saline. Three weeks later the mice received a second dose of vaccine followed 2 weeks later by an aerogenic challenge with approximately 10(3) CFU of M. tuberculosis Erdman. The mice receiving the adjuvanted A60 showed a significant reduction (P less than 0.05) in the number of viable organisms recovered from the lungs and the spleen 3 weeks after challenge. However, this response was less than that seen in BCG vaccinated controls.

Animals↗
PubMed1992

Immunization of mice with mycobacterial culture filtrate proteins.

Culture filtrate proteins were obtained from Mycobacterium tuberculosis cultures after 7 days growth in Proskauer and Beck medium. The protein yield increased substantially to peak about the time the number of viable organisms reached its maximum level (day 8). Examination of the protein concentrate by SDS-PAGE revealed the presence of at least 12 separate protein bands varying from 10 to 90 kD. Mice were injected subcutaneously with 20 micrograms of M. tuberculosis culture filtrate (MTCF) protein suspended in saline or Freund's complete or incomplete adjuvant. The vaccinated mice were subjected to an aerogenic challenge with 10(3) colony-forming unit (CFU) M. tuberculosis Erdman and a significant reduction in the number of viable organisms was observed in the spleens and lungs determined over a 21-day period compared with age-matched normal controls. Mice immunized with the same culture filtrate proteins bound to nitrocellulose particles also showed some resistance to the virulent challenge, suggesting that individual antigens present in the culture filtrate were able to induce a protective T cell-mediated immune response in appropriately immunized mice.

Animals↗
PubMed1992

T-cell immune responses in Mycobacterium avium-infected mice.

Mycobacterium avium infection was substantially more severe in C57BL/6 (Bcgs) than in (C57BL/6 x DBA/2)F1 hybrid (Bcgr) mice both in terms of bacterial growth in the spleens and lungs and in host survival. Prior Mycobacterium bovis BCG vaccination resulted in increased resistance as well as enhanced tuberculin hypersensitivity to both PPD-S (Mycobacterium tuberculosis) and PPD-A (M. avium). Mice heavily infected with M. avium were used as T-cell donors in an adoptive transfer system. Substantial resistance was observed for both recipient hosts regardless of the genotype of the donor strain. Transfer of resistance was ablated by treatment of the immune spleen cells with anti-Thy 1.2 monoclonal antibody and complement or by cyclophosphamide treatment. Spleen cells which were monodepleted of L3T4+ or Lyt-2+ T cells did not lose their ability to transfer resistance against a subsequent challenge. However, when these cells were doubly deleted, all resistance was ablated in both the BCG-susceptible and -resistant mice. The recipient host expressed a detectable adoptive immune response although the donor had been unable to reduce the growth of the primary M. avium infection in vivo.

Analysis of Variance↗
PubMed1991

Immunomodulation of mouse macrophage killing of Mycobacterium avium in vitro.

When C57BL/6 mice were infected intravenously with Mycobacterium avium, bacterial growth continued within the spleen until more than 10(8) CFU/g of tissue were attained. This contrasted with Mycobacterium bovis BCG infections where growth declined after 2 weeks. In vivo M. avium-infected splenic macrophages were harvested from chronically infected mice and cultured in vitro for 4 days at 37 degrees C. The number of viable mycobacteria within the resulting macrophage monolayers decreased when cultured in the presence of autologous sensitized T cells and an exogenous source of interleukin-2 (recombinant interleukin-2; 50 U/ml) compared with untreated controls (P less than 0.05). Incubation of the infected macrophages with autologous T cells and soluble M. avium antigens also significantly reduced the number of viable organisms. These results indicate that the mycobactericidal activity of M. avium-infected macrophages can be enhanced in a way that may have important therapeutic implications for patients infected with this opportunistic pathogen.

Animals↗
PubMed1991

Memory T cell-mediated resistance to Mycobacterium tuberculosis infection in innately susceptible and resistant mice.

The memory T cell immune response to Mycobacterium tuberculosis infection was examined in strains of mice which vary in their natural susceptibility to Mycobacterium bovis BCG infection. Naturally susceptible (NS) C57BL/6 and naturally resistant (NR) B6D2 F1 hybrid mice were infected with a sublethal dose of M. tuberculosis and then given antibiotic therapy beginning 2 weeks postinfection. T cells from both strains of mice transferred significant levels of resistance to syngeneic mice challenged aerogenically with M. tuberculosis. This memory response was not substantially reduced by depletion of either L3T4+ or Lyt2+ T cells from the donor mice but was ablated by depletion of both T cell subsets. Cyclophosphamide pretreatment of C57BL/6 memory T cell donors also ablated the resistance transferred to recipient mice. In contrast, B6D2 memory T cells were not affected by cyclophosphamide treatment, suggesting that differences may exist in the metabolic state of the memory T cells in the two donor strains, despite the fact that they both develop similar levels of acquired resistance to a subsequent tuberculous challenge.

Animals↗
PubMed1990

Passive transfer of immunity of Mycobacterium avium in susceptible and resistant strains of mice.

Naturally susceptible mice (C57BL/6) infected with M. avium (strain Weybridge) developed a population of splenic T cells which, on transfer to syngeneic recipient mice, conferred significant protection against a subsequent challenge inoculum of M. avium. Similar T cells from naturally resistant mice (A/J) did not protect syngeneic recipient mice. Growth of M. avium in donor mice only occurred in the C57BL/6 strain. Replication of M. avium in donor mice was necessary for the development of protective T cells. High numbers of killed mycobacterium did not induce immune T cells. In addition, A/J mice inoculated with increasing numbers of viable M. avium (which still did not replicate) failed to develop protective T lymphocytes. Further studies indicated that no protective T cells were present in the M. avium-infected A/J mouse, although evidence for non-specific immunity in these mice was obtained. In addition, BCG (which grows progressively in A/J mice) stimulated a population of splenic T cells which protected recipient mice from subsequent infection with M. tuberculosis.

Animals↗
PubMed1990

Dynamics of the phagocytic cell response within the lungs of parabiotic mice infected with mycobacteria with decreasing virulence for mice.

Alveolar macrophages constitute the first line of defense against an aerogenic mycobacterial challenge. The kinetics of the alveolar macrophage response to an infectious stimulus was studied in parabiotic (C57BL/6 x DBA/2 [B6D2]F1 hybrid mice pulse-labeled with tritiated thymidine given to one (donor) animal while the other (recipient) received an equivalent amount of "cold" thymidine. Lavage fluid collected from uninfected recipients yielded few labeled monocytes. However, after introduction of 10(5) viable Mycobacterium bovis BCG into the lung, an immediate influx of heavily labeled mononuclear cells was observed, peaking around day 3. This cellular response was compared with that induced by several members of the Mycobacterium avium complex of different virulence to mice. The strains M. avium 724 and M. intracellulare 1405, virulent to mice, induced moderate mononuclear cell responses, whereas the avirulent M. intracellulare 1411 induced a predominantly polymorphonuclear rather than mononuclear cell influx, analogous to that seen when heat-killed mycobacteria were introduced into the lung. These results suggest that the mycobacteria within the lung must remain in a metabolically active state in order to induce the maximum mononuclear cell response of the type associated with acquired antituberculous immunity.

Administration, Inhalation↗
PubMed1989

Mycobacterial disease, immunosuppression, and acquired immunodeficiency syndrome.

The mycobacteria are an important group of acid-fast pathogens ranging from obligate intracellular parasites such as Mycobacterium leprae to environmental species such as M. gordonae and M. fortuitum. The latter may behave as opportunistic human pathogens if the host defenses have been depleted in some manner. The number and severity of such infections have increased markedly with the emergence of the acquired immunodeficiency syndrome (AIDS) epidemic. These nontuberculous mycobacteria tend to be less virulent for humans than M. tuberculosis, usually giving rise to self-limiting infections involving the cervical and mesenteric lymph nodes of young children. However, the more virulent serovars of M. avium complex can colonize the bronchial and intestinal mucosal surfaces of healthy individuals, becoming virtual members of the commensal gut microflora and thus giving rise to low levels of skin hypersensitivity to tuberculins prepared from M. avium and M. intracellulare. Systemic disease develops when the normal T-cell-mediated defenses become depleted as a result of old age, cancer chemotherapy, or infection with human immunodeficiency virus. As many as 50% of human immunodeficiency virus antibody-positive individuals develop mycobacterial infections at some time during their disease. Most isolates of M. avium complex from AIDS patients fall into serotypes 4 and 8. The presence of these drug-resistant mycobacteria in the lungs of the AIDS patient makes their effective clinical treatment virtually impossible. More effective chemotherapeutic, prophylactic, and immunotherapeutic reagents are urgently needed to treat this rapidly increasing patient population.

Acquired Immunodeficiency Syndrome↗
PubMed1988

T-cell-mediated immunity in persistent Mycobacterium intracellulare infections in mice.

Growth of mouse-virulent Mycobacterium intracellulare D673 and TMC 1405 in the lung was affected by T-cell depletion in susceptible C57BL/6 mice. Significant differences also occurred between the growth patterns seen in congenitally athymic (nu/nu) mice and their nu/+ littermates. Treatment of the mice with an immunosuppressive regimen of cyclosporin A (75 mg/kg of body weight per day subcutaneously) provided further evidence of the importance of T cells in controlling growth of M. intracellulare in the normal host. Adoptive transfer experiments indicated the presence of a T-cell-mediated specific protective immunity against a subsequent M. intracellulare challenge when transfer was carried out 3 weeks after immunization of the donor host. At this time, cross-protective immunity was also observed against a virulent M. tuberculosis challenge. There was no difference in the rate of growth by M. intracellulare as challenge in Mycobacterium bovis BCG-activated or normal peritoneal macrophages from C57BL/6 mice tested in vitro during a 7-day period. However, M. tuberculosis growth rates were decreased substantially in the BCG-activated macrophages. These studies suggest that mice infected with M. intracellulare do not eliminate the infection, because this organism can resist the bactericidal activity of the T-cell-activated macrophage better than M. tuberculosis can.

Animals↗
PubMed1988

Biological activity of protein antigens isolated from Mycobacterium tuberculosis culture filtrate.

Mycobacterium tuberculosis culture filtrate (MTCF) protein antigens were isolated from mid-logarithmic-phase cultures grown in liquid medium and examined by high-pressure liquid chromatography and Western blot (immunoblot) analysis. A major protein band with a molecular mass of about 68 kilodaltons (kDa) and several fainter bands in the 38- and 24-kDa range were observed. The MTCF protein produced a significant delayed footpad hypersensitivity response in Mycobacterium bovis BCG-vaccinated C57BL/6 mice, comparable to that observed with standard purified protein derivative (PPD). The same proteins induced a blastogenic response in tuberculin-sensitive human peripheral blood monocytes and in T-cell clones developed from these cells. The proliferative responses to the MTCF antigens were equivalent to those observed following stimulation with PPD or M. tuberculosis sonic extracts. However, the MTCF sensitins were not recognized by five monoclonal antibodies directed against killed M. tuberculosis antigens in an enzyme immunoassay, although some response was seen with a monoclonal antibody (ML34) directed against M. leprae antigens. The ability of the MTCF to stimulate T-cell responses both in vivo and in vitro while not being recognized by antibodies directed against dead mycobacterial antigens suggests that they may be of interest as potential protective immunogens.

Animals↗
PubMed1988

Growth of Mycobacterium avium in activated macrophages harvested from inbred mice with differing innate susceptibilities to mycobacterial infection.

The growth of Mycobacterium avium in macrophages obtained from Mycobacterium bovis BCG-infected mice was compared with that in macrophages from uninfected mice. BCG vaccination resulted in substantial macrophage activation, measured as increased acid phosphatase and superoxide anion production, as well as enhanced leishmanicidal activity. However, the activated macrophages were only able to reduce the rate of intracellular growth by Listeria monocytogenes and M. avium in vivo and did not express detectable levels of mycobactericidal activity in vitro. Exposure of the macrophage monolayers to concanavalin A-stimulated spleen cell supernatant fluid and lipopolysaccharide did not further enhance the ability of the BCG-activated macrophages to control the intracellular replication of the M. avium. Macrophages from BCG-infected C57BL/6 (BCGs) mice were quantitatively better able to control the intracellular replication of the M. avium challenge than were similar phagocytes obtained from BCGr (A/J) mice. These findings have important implications with respect to the expression of acquired resistance to these atypical mycobacterial infections.

Animals↗
PubMed1987

Mycobacterium avium-complex infections in normal and immunodeficient mice.

Specific pathogen-free C57Bl/6 X DBA/2 (B6D2) F1 hybrid mice were challenged aerogenically with M. avium, M. intracellulare and M. scrofulaceum and the resulting lung and spleen infections were followed over a period of several months. Growth of the mouse virulent M. avium 724 and M. intracellulare D673 was more extensive in the susceptible (Balb/c or C57Bl/6) mice than it was in the resistant A/J and B6D2 strains. Oral challenge of normal C57Bl/6 mice with virulent M. avium-complex serotypes resulted in substantial infection of the gut-associated lymphoid tissues, the lungs and spleen. No infection developed when the mice were infected orally with the avirulent MAC serotypes. T-cell depleted Balb/c (nude or Thxb) mice infected with virulent M. avium developed markedly enhanced lung and spleen infections compared to those seen in the immunocompetent controls. T-cell depletion did not potentiate the systemic growth of the avirulent MAC strains. The significance of these growth patterns (especially in the T-cell depleted mouse) is discussed in relation to the development of life-threatening M. avium-complex infections in patients with Acquired Immune Deficiency Syndrome.

Animals↗
PubMed1987

Use of membrane filters for measurement of mycobactericidal activity of alkaline glutaraldehyde solution.

Bactericidal assays of 2% alkaline glutaraldehyde solution were carried out using Millipore membranes, and the rate of kill was compared with that of mycobacteria in suspension and on Penicylinder surfaces when using the methods recommended for the official tuberculocidal test. The rate of inactivation observed on the membrane filter surface was similar to that achieved using Penicylinders. The absence of visible colonies on the treated membranes provided a direct demonstration of sterility. The use of filter membranes in tuberculocidal tests provides a simple quantitative assay.

Aldehydes↗
PubMed1987

Immunosuppressive effect of cyclosporin A on Mycobacterium bovis BCG infections in mice.

The effect of increasing doses of cyclosporin A (CsA) given to mice infected intravenously with Mycobacterium bovis BCG was investigated. Development of both tuberculin hypersensitivity and acquired antituberculous resistance was suppressed in a dose-responsive manner. Daily dosages at 100 mg/kg of body weight prevented any reduction in the BCG counts within the lungs, liver, or spleen. This effect was associated with lowered nonspecific resistance to a Listeria monocytogenes challenge and a decline in specific protective immunity adoptively transferred to naive recipients. CsA treatment had no effect on antilisterial activity by activated macrophages or on the antituberculous immunity expressed by specific memory T cells. CsA treatment inhibited the ability of BCG-vaccinated mice to produce gamma interferon (IFN-gamma) after a secondary stimulation with live BCG or with lipopolysaccharide. Spleen cells from BCG-infected mice which were exposed to daily treatment with CsA showed reduced IFN-gamma production in response to purified protein derivative or concanavalin A stimulation, suggesting that the immunosuppressive effect of CsA on BCG-infected mice was expressed by inhibiting the development of effector T cells responsible for the production of IFN-gamma.

Animals↗