Identification of a trypanocidal factor against Trypanosoma equiperdum in normal human serum

Normal human serum (HS) contains trypanolytic activity and agglutinins to Trypanosoma equiperdum, while such activities are not found in sera from a range of animals susceptible to infection. HS given to T. equiperdum-infected mice caused a rapid decrease in the number of circulating trypanosomes and protection from lethal infection. Trypanolytic activity of human serum was found to be associated, after DEAE chromatography and Sephadex G-200 gel filtration, with the fraction containing 19S antibodies. Immunofluorescence assays confirmed a binding of human IgM and C1q complement component onto the surface of T. equiperdum. Anti-T. equiperdum activity of HS was specifically directed to T. equiperdum surface components and not to some mouse serum components adsorbed on parasites during the growth in the host, because HS adsorbed in vivo in CD-1 mice retained full protective and agglutinating properties. Trypanocidal activity appears in human serum about the 7th month after birth and persists until late in life. On the contrary, human purified high-density lipoprotein had no significant in vitro or in vivo trypanocidal activity. In conclusion, strong natural anti-T. equiperdum activity in human serum was mainly mediated by natural antibodies of the IgM class. The presence of natural IgM active against T. equiperdum in HS could represent one of the natural mechanisms of resistance of refractory hosts against trypanosome infections. This phenomenon provides further evidence that host specificity of trypanosomes may be partly conditioned by the presence of natural antibodies.

Cell wall components of Candida albicans as immunomodulators: induction of natural killer and macrophage-mediated peritoneal cell cytotoxicity in mice by mannoprotein and glucan fractions

Cell wall components from Candida albicans were compared to intact cells for their ability to induce natural cytotoxic immunoeffectors in the peritoneal cavity of mice. A soluble mannoprotein extract (MP) and an insoluble glucan fraction (GG) strongly stimulated the generation of peritoneal effectors capable of lysing YAC-1 and P-815 tumour cell lines in vitro. The anti-YAC-1 effectors were characterized as natural killer (NK) lymphocytes while the anti-P-815 effectors appeared to be activated macrophages. The activity of each fraction was typically dose-dependent and both fractions differed from whole cells in the kinetics of induction of cytotoxicity. However, the NK and macrophage effectors generated by these materials had similar functional and phenotypic properties, irrespective of the material used as inducer. No mannoprotein was detected in the insoluble glucan fraction GG. Hence, the immunoenhancing activity of GG could not be attributed to the presence of some MP or MP-like component. Mannan-rich fractions with low (less than 3%) protein content (M) or extracted by hot alkaline reagent (M-alk) were inactive as NK and macrophage inducers. Thus, the cell wall of C. albicans contains at least two distinct macromolecular complexes which mediate the induction in murine peritoneal exudates of cytotoxic effectors active against tumour cell lines.

Comparative in vitro activity of imipenem against gram-positive and gram-negative aerobic bacteria from clinical isolates

Imipenem is a member of a new class of beta-lactam antibiotics, carbapenems, with a very broad antibacterial spectrum. In this work we evaluated the in vitro activity of imipenem against a variety of bacterial strains isolated from clinical specimens as well as the activity of other beta-lactam antibiotics. The results obtained with 501 bacterial strains show that imipenem is active on both gram-negative and gram-positive microorganisms isolated from different infections. The in vitro inhibitory activity is greater than that of aztreonam, cefotaxime, ceftriaxone, piperacillin, amikacin, and netilmicin, against the majority of strains tested.

Immunomodulation by a low-virulence, agerminative variant of Candida albicans. Further evidence for macrophage activation as one of the effector mechanisms of nonspecific anti-infectious protection

Systemic infection of mice with a Candida albicans strain (PCA-2) incapable of yeast-mycelial conversion is known to activate host macrophages and confer protection against subsequent challenge with highly pathogenic cells of the same species or by other micro-organisms. In an attempt to define the relative contributions of different immune components to the protection mediated by PCA-2, we evaluated the effect of manipulations known to selectively deplete immune functions. By means of cytostatic drug or silica induced toxicity, it was possible to demonstrate that no crucial role in protection is played by cytotoxic T lymphocytes or B cells, nor by PCA-2 induced granulocytosis alone. The cells responsible for this effect were dacarbazine-resistant silica-sensitive macrophages whose activity in vivo paralleled the in vitro expression of splenic candidacidal activity. Macrophage activation by PCA-2 and increased anti-Candida resistance did not result from an immunological response mediated by T-dependent effectors, as these effects could be reproduced in athymic mice.

Cell wall of Candida albicans and host response

Modulation in chemistry and organization of cell wall macromolecules play decisive roles in the morphogenic processes and virulence of Candida albicans. Cell wall components also have a diversified range of effects on the host's immune system, including immunopotentiating or immunodepressing activities. Mannan, mannan-protein, and glucan fractions have been especially studied in this context. In in vitro cultured human peripheral blood mononuclear cells, a mannan-protein fraction (GMP) from the cell wall of the yeast form acted as a strong antigenic activator by stimulating lymphokine production and lymphocyte proliferation. Cytolytic effectors active against several tumor targets were also generated. In the mouse, GMP was a strong inducer of natural killer lymphocytes. Other cell wall components, mostly the insoluble beta-glucan, modulated the activity of macrophages and monocyte precursors. Some of the immunomodulating properties of artificially extracted components were shared, even with greater potency, by antigens which were released from C. albicans during its growth and hyphal morphogenesis. Altogether, the range of the immunoresponses elicited and the intensity of the observed effects are such as to individuate in this human indigenous fungus a microorganism capable of profoundly affecting the host's immune system.

Involvement of host macrophages in the immunoadjuvant activity of amphotericin B in a mouse fungal infection model

We have recently reported the in vivo augmentation of resistance to experimental Candida albicans injection by amphotericin B in mice and have shown that this event is concurrent with the appearance in the spleen of a highly candidacidal cell population reactive in vitro against 51Cr-labeled yeast cells. In the present study we characterize these in vitro fungicidal effectors as macrophages and describe the conditions of amphotericin B treatment most suitable for inducing candidacidal activity. We also report that macrophages from intact mice can be activated in vitro to become cytotoxic against Candida. The possible mechanisms through which the amphotericin B activated macrophages exert their increased anti-Candida activity are also investigated.

Evidence for macrophage-mediated protection against lethal Candida albicans infection

Systemic infection of mice with a Candida albicans strain (PCA-2) incapable of yeast-mycelial conversion conferred protection against a subsequent intravenous challenge with the pathogenic strain of the parent organism, strain CA-6. Protection was nonspecific since it was also detected upon challenge of mice with Staphylococcus aureus. Moreover, the PCA-2 organisms had to be viable, their effects being most evident when they were given intravenously at a dose of 10(6) cells 7 to 14 days prior to microbial challenge. Thus, all mice pretreated with PCA-2 and challenged 14 days later with viable CA-6 cells lived through a 60-day observation period, whereas all control mice not treated with PCA-2 died within 3 days. In an attempt to correlate the immunostimulatory effects observed in vivo with possible modifications in in vitro functions, it was found that administration of PCA-2 was accompanied by an increase in the number of peripheral blood polymorphonuclear cells and by the activation in the spleen of cells with highly candidacidal activity in vitro. Moreover, the adoptive transfer of plastic-adherent cells from PCA-2-infected mice into histocompatible recipients conferred considerable protection against subsequent CA-6 challenge.

Induction of natural killer cell activity by inactivated Candida albicans in mice

Injection of merthiolate-inactivated yeast form cells of Candida albicans into the peritoneal cavities of mice induced the appearance of a cytolytic effector population against YAC-1 tumor cell lines. This induction was maximally manifested in 5- to 8-week-old animals 3 to 4 days after injection of 2 X 10(7)C. albicans cells, and the peritoneal lytic population exerted its optimum cytotoxic effect after 4 h of incubation. No significant natural cytotoxic activity was generated by C. albicans in the bone marrow or thymus, whereas there was a slight, transient, but significant depression of natural splenic cytotoxicity. Experiments performed to characterize the natural cytotoxic population elicited by the inactivated yeast showed that the effectors were nonadherent, nonphagocytic cells. Moreover, the anti-YAC-1 lytic activity was partially sensitive to anti-Thy1.2 serum and was completely abrogated by treatment of peritoneal nonadherent cells with monoclonal anti-asialo GM1 antibodies. Finally, the peritoneal population of cytotoxic cells induced by C. albicans was fully susceptible to Ly5.1 plus anti-immunoglobulin G2a and complement lysis. Although different cell populations could be induced by inactivated C. albicans, all of our data support the view that the anti-YAC-1 activity was entirely attributable to natural killer lymphocytes.

Immunoadjuvant activity of amphotericin B as displayed in mice infected with Candida albicans

Mice receiving a single intraperitoneal injection of amphotericin B showed increased resistance to subsequent challenge with either Candida albicans or Staphylococcus aureus. This enhancement of resistance was obvious in terms of both survival criteria and clearance of the intravenously injected organism from different organs. The protective effect of amphotericin B was conditioned by dose, time of drug administration, and size of yeast or bacterial inoculum and was reversed by cyclophosphamide. Effector cells from mice treated with amphotericin B displayed enhanced fungicidal activity in vitro as measured in a short-term 51Cr release assay. Macrophages from intact animals exposed in vitro to amphotericin B also acquired strong candidacidal reactivity.

Turkey red blood cell passive haemagglutination assay as guideline for specific prevention of tetanus in injured persons

Turkey red blood cell passive haemagglutination assays (TRBC-HA) were carried out on serum samples from 873 injured patients in order to compare individual prophylactic treatment against tetanus based on the anti-tetanus antibody levels with interventions based on anamnestic criteria. The results showed a great difference: according to the anamnesis 124 persons (14.2%) were protected, 253 (29%) were partially protected, and 496 (56.8%) were unprotected; according to the TRBC-HA assay, 479 (54.9%) were protected, 279 (32%) partially protected, and 115 (13.2%) unprotected.The efficiency of the prophylactic treatments given on the basis of the two criteria was also compared in a study of 129 injured patients who were divided in two groups: group 1 (50 patients) received 250 IU of human tetanus immunoglobulin (HTI) regardless of their tetanus immunity, and group II (79 patients) received appropriate or no treatment depending on the level of anti-tetanus antibodies determined by TRBC-HA assay. The results showed that prophylactic interventions based on the anti-tetanus antibody levels can give protection in 100% of injured patients at minimum cost and risk.

Enhancement of natural killer cell activity in mice by treatment with a thymic factor

The administration of a thymic factor, thymostimulin (TP-1), to mice resulted in considerable augmentation of natural killer (NK) cell activity as measured in a short-term assay against 51Cr-labeled YAC-1 target cells. Conditions suitable for detection of the thymostimulin-induced boosting of NK included multiple daily exposures to TP-1 (50 micrograms/kg), and peak levels of reactivity were observed at 2-4 days after discontinuation of treatment. A strict age-dependency of the effect was also observed, with optimal augmentation of NK-cell activity when TP-1 was administered to mice at 4-6 weeks of age. The effect was not limited to TP-1 treatment but was also observed on administration of another thymic factor (thymosin alpha 1). The activated cells responsible for the increased natural cell-mediated cytotoxicity appeared to be typical murine NK cells, judging by both functional and antigenic criteria.

Combined effects of chemotherapy and host antitumor response in a murine histocompatible lymphoma model

Combined effects of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) and host antitumor immune response were studied in mice inoculated intraperitoneally with histocompatible LSTRA leukemia cells carrying virus-induced transplantation antigens. Marked chemo-immune collaborative activity was found to occur when selected schedules of BCNU administration were employed. Moreover, synergist effects were also detected between chemotherapy and both specific and non-specific immunotherapy.

Relationships among tumor load, route of tumor inoculation, and response to immunochemotherapy in a murine lymphoma model

The combined effects of nonspecific immunostimulation with Candida albicans (CA) and chemotherapy were studied in (BALB/cCr X DBA/2Cr)F1 and (C57BL/6Cr X DBA/2Cr)F1 mice bearing virus-induced LSTRA lymphomas. Paradoxically, animals treated with a relatively high number of tumor cells responded better to therapy with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) than those challenged with a low number of tumor cells. However, the majority of mice subjected to low initial tumor load were cured when they were treated with chemotherapy or chemotherapy plus booster injection of CA at a relatively "late" stage of the disease, i.e., when high tumor load was present in tumor-bearing hosts. It has been shown that this phenomenon, provisionally called high tumor load protection, occurs when the animals are challenged ip but not when they are challenged iv with the tumor and is abolished by total-body gamma-irradiation. Moreover, marked host protection can be attained when immunostimulated mice, inoculated iv with lymphoma cells, are subjected to simultaneous challenge with high inocula of the same tumor ip, followed by BCNU administration. These data stress the importance of the peritoneal cavity for successful CA plus drug treatment and suggest that optimal tumor "antigen load" should be present at the time of CA and/or BCNU administration.

Suppression of Friend leukemia cell-induced tumours by cellular preparations of Candida albicans

Inactivated cellular preparations and cell wall materials of Candida albicans (CA) were tested for their capacity to suppress the growth of Friend Leukemia Cell (FLC)-induced tumours and the infection by Friend Leukemia Virus (FLV) in histocompatible mice. Factors affecting the inhibition of tumor growth by CA cellular preparations were: i) the schedule of agent administration; ii) the method of cell inactivation; iii) the FLC load. In particular, mice given 10(7) yeast cells, inactivated by cold alkali, on days -14 and +1 with respect to 10(4) FLC challenge on day 0 did not develop tumors. A crude cell wall fraction derived from cells extracted with hot alkali was still effective in reducing (but not suppressing) tumour growth whereas a purified, particulate glucan fraction (glucan "ghosts", essentially consisting of beta 1,3-1,6 glucan) was ineffective. No cellular preparation or cell wall fraction exerted anti-FLV effects (as shown by splenomegaly measurements) nor did any CA material induce interferon-like activity in the serum of animals injected with either FLC or FLV. Therefore, the observed antitumor activity by CA was not mediated by antiviral effects but possibly due to an "adjuvant-type", nonspecific, immunopotentiation of host antitumor response, as documented in other animal tumor models.

Correlation between in vivo and in vitro studies of modulation of resistance to experimental Candida albicans infection by cyclophosphamide in mice

Mice receiving a single injection of cyclophosphamide (150 mg/kg) 1 to 6 days before inoculation with viable Candida albicans showed an increased susceptibility to the challenge accompanied by a reduction in peripheral blood polymorphonuclear leukocytes and lymphocytes as well as in spleen cellularity. Several immunological in vitro functions also appeared to be dramatically depressed. Most of these hematological and functional parameters returned to control values by day 9 after cyclophosphamide administration, at a time when resistance to C. albicans infection appeared to be unchanged. However, when exposure to cyclophosphamide occurred 12 to 21 days before inoculation with the live yeast, enhanced resistance was observed with the majority of the animals surviving challenge. To gain some insight into the mechanisms underlying this late increase in resistance to C. albicans infection after cyclophosphamide administration, we analyzed a series of immunological functions, including the in vitro candidacidal activity of polymorphonuclear neutrophils and plastic-adherent and nonadherent spleen cells as well as the activity of natural killer cells and alloreactive T lymphocytes. The results show that a numerical rebound of blood polymorphonuclear neutrophils and the appearance of a highly candidacidal cell population in the spleen may be among the factors underlying the late increase in resistance to C. albicans after administration of cyclophosphamide.

Comparison of Passive Hemagglutination with Turkey Erythrocyte Assay, Enzyme-Linked Immunosorbent Assay, and Counterimmunoelectrophoresis Assay for Serological Evaluation of Tetanus Immunity

Antibody titers to tetanus toxin in human sera were assayed by passive hemagglutination with turkey erythrocytes, enzyme-linked immunosorbent assay, and counterimmunoelectrophoresis. The first two of these tests were shown to be the most sensitive for antibody detection, having the same range of sensitivity and reproducibility. The antibody levels determined by these assays were up to 400-fold higher than those determined by counterimmunoelectrophoresis. The turkey erythrocyte hemagglutination assay requires only 40 min, whereas the immunosorbent assay method requires 24 h. These results suggest that the hemagglutination assay is the more appropriate method for rapid and sensitive determination of tetanus antibody levels.

Determination of immunity against tetanus infection by passive haemagglutination assay

Evaluation of anti-tetanus antibody level in human sera is of primary importance for a prophylaxis of tetanus infection. Many efforts have been made to develop simple, sensitive and reproducible in vitro methods for detecting and quantifying antibodies to tetanus toxin. We have recently developed an HA assay using lyophilized turkey red blood cells (TRBC-HA). In this paper we demonstrated that the TRBC-HA test is more sensitive than the most widely used sheep red blood cell assay (SRBC-HA) and that TRBC-HA assay shows a high correlation with the neutralization test (NT). Furthermore, comparisons of TRBC-HA assay with enzyme-linked immunosorbent assay (ELISA) and counterimmunoelectrophoresis (CIE) indicate that TRBC-HA and ELISA assays detected the same antibody level with a sensitivity up to 400-fold higher than that determined by CIE. However, TRBC-HA also offers many advantages over the ELISA test, because TRBC-HA can be performed in only 40 minutes instead of the 24 hrs. needed for the ELISA, it is less expensive than ELISA and requires no special equipment. Therefore, the overall results suggest that the TRBC-HA is the most appropriate method for rapid and sensitive determination of tetanus antibody levels.