Amphotericin B and 5-fluorocytosine: in vitro effects on lymphocyte function

Adverse drug reactions to systemic antifungals. Prevention and management

Systemic administration of antifungal agents for invasive mycoses has dramatically increased over the past 10 years in many fields of medicine. The increase has been due both to an increasing immune compromised population and to potent antibacterial agents which allow these fungi to invade tissue. It is apparent that our understanding of the use of both the old and new antifungal agents has significantly increased in the last few years. In this review, we attempt to document our extensive knowledge of the adverse effects of the polyenes, flucytosine, griseofulvin and azoles when given systemically for treatment. Interwoven in this documentation of the adverse reactions to these agents is the attempt to help clinicians potentially avoid some of these adverse effects and if they do occur, to be able to identify and successfully manage them.

Liposomal amphotericin B inhibits in vitro T-lymphocyte response to antigen

The effects of free amphotericin B (as Fungizone) and amphotericin B (AMB) incorporated into liposomes on the proliferation of lymphocytes were determined. Freshly obtained guinea pig and rat antigen-specific lymphocytes were compared with rat T-lymphocyte cell lines cultured for a long period of time. Incorporation of AMB into multilayered vesicles significantly reduced its effect relative to that of Fungizone on cultured T-cell lines, as reported by others for mammalian cells. In contrast, the effects on freshly obtained antigen-specific lymphocytes were different. Fungizone inhibited proliferation of antigen-specific lymph node cells freshly obtained from immunized guinea pigs at fungicidal concentrations, and incorporation into multilayered lipid vesicles did not have much of a protective effect. Higher concentrations of Fungizone were required to inhibit proliferation of fresh rat lymph node cells, but incorporation into multilayered lipid vesicles still did not have much of a protective effect. Some T lymphocytes in the peripheral circulation of guinea pigs and in the lymph nodes of rats were more resistant to liposomal AMB than another more sensitive T-lymphocyte population was. Proliferation of lymphocytes in response to mitogens was inhibited less than that in response to specific antigen was. Thus, sensitivity to AMB depended on the species, the strength of the stimulus used to activate the lymphocytes, and on some other property of the lymphocytes, possibly their state of differentiation. Regardless of the reason for the difference in effects on freshly obtained lymph node lymphocytes and cultured line cells, the former may be more relevant to effects in vivo and should be considered in a complete evaluation of the in vivo toxicity of these forms of the drug. Incorporation into sonicated unilamellar vesicles had more of a protective effect, while equimolar drug-lipid complexes had even more of a protective effect. These forms of AMB might have less of an immunosuppressive potential than multilayered vesicles containing low amounts of AMB do.

The use of amphotericin B in prevention of Trypanosoma theileri growth in bovine cell culture

Trypanosoma theileri is an ubiquitous blood parasite of cattle. This parasite grows easily in RPMI medium and perturbs lymphocyte tests based on [3H]thymidine uptake. This paper reports that 0.5 microgram ml-1 amphotericin B in the medium is adequate to get Trypanosoma growth inhibition without alteration of either mitogenic or allogenic stimulation of bovine lymphoid cells in vitro.

How do the polyene macrolide antibiotics affect the cellular membrane properties?

In the 1970's great strides were made in understanding the mechanism of action of amphotericin B and nystatin: the formation of transmembrane pores was clearly demonstrated in planar lipid monolayers, in multilamellar phospholipid vesicles and in Acholeplasma laidlawii cells and the importance of the presence and of the nature of the membrane sterol was analyzed. For polyene antibiotics with shorter chains, a mechanism of membrane disruption was proposed. However, recently obtained data on unilamellar vesicles have complicated the situation. It has been shown that: membranes in the gel state (which is not common in cells), even if they do not contain sterols may be made permeable by polyene antibiotics, several mechanisms may operate, simultaneously or sequentially, depending on the antibiotic/lipid ratio, the time elapsed after mixing and the mode of addition of the antibiotic, there is a rapid exchange of the antibiotic molecules between the vesicles. Although pore formation is apparently involved in the toxicity of amphotericin B and nystatin, it is not the sole factor which contributes to cell death, since K+ leakage induced by these antibiotics is separate from their lethal action. The peroxidation of membrane lipids, which has been demonstrated for erythrocytes and Candida albicans cells in the presence of amphotericin B, may play a determining role in toxicity concurrently with colloid osmotic effect. On the other hand, it has been shown that the action of polyene antibiotics on cells is not always detrimental: at sub-lethal concentrations these drugs stimulate either the activity of some membrane enzymes or cellular metabolism. In particular, some cells of the immune system are stimulated. Furthermore, polyene antibiotics may act synergistically with other drugs, such as antitumor or antifungal compounds. This may occur either by an increased incorporation of the drug, under the influence of a polyene antibiotic-induced change of membrane potential, for example, or by a direct interaction of both drugs. That fungal membranes contain ergosterol while mammalian cell membranes contain cholesterol, has generally been considered the basis for the selective toxicity of amphotericin B and nystatin for fungi. Actually, in vitro studies have not always borne out this assumption, thereby casting doubt on the use of polyene antibiotics as antifungal agents in mammalian cell culture media.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of 2-mercaptoethanol and mycostatin on guinea pig lymphocyte transformation: interpretation of results depends on the method of calculation

The stimulating effects of 2-mercaptoethanol (2-ME) reported in murine cell cultures were confirmed for guinea pig lymphocyte transformation (LT). 2-ME was mitogenic for peripheral blood lymphocytes (PBL) and lymph node lymphocytes (LNL) and enhanced PPD-induced LT. The effect on LNL was dependent on the magnitude of the response of non-2-ME treated cultures. The 2-ME effect on PPD-stimulated LNL was reversed when stimulation index (SI) replaced the delta cpm estimate. Mycostatin (MYC) inhibited the blastogenic response of PBL control cultures, whereas its effect on LNL control cultures varied. The interpretation of the effect of MYC on PPD-stimulated cultures was dependent on the use of the delta cpm or SI estimates. The interpretation of LT experiments is therefore highly dependent on whether delta cpm or SI is used for expression of results. Analysis of effects on control and stimulated cultures should precede the addition of 2-ME or MYC to cultures for LT.

Amphotericin B modifications of peripheral blood lymphocyte and tonsil lymphocyte responses to concanavalin A

Peripheral blood lymphocytes (PBL) were shown previously to be activated to incorporate 3H-thymidine by concanavalin A (con A). Amphotericin B (Am B) was reported to be both immuno-enhancing and suppressive. We investigated the response of PBL and tonsil lymphocytes (TL) to con A in culture, and the effect of Am B on these responses. PBL were activated by con A as expected, and the magnitude of the response diminished as cell density increased. The responses of PBL usually were significantly enhanced by Am B at 2.5 or 5 micrograms/ml, but 10 micrograms Am B/ml significantly inhibited the con A response. TL had relatively high rates of spontaneous proliferation, but Am B was a potent inhibitor of this. TL responded to con A just as well as PBL, and Am B strongly inhibited these responses too. When TL were cultured with various doses of con A in the presence of 5 or 10 micrograms Am B/ml, the shape of the dose curves resembled those of PBL stimulated in the absence of Am B except that the incorporation of 3H-thymidine increased with increasing cell density. It was concluded that Am B at 2.5-5.0 micrograms/ml enhanced the response of PBL to con A and suppressed the response at 10 micrograms/ml. All doses of Am B inhibited both spontaneous proliferation and con A-induced proliferation in TL. In spite of this inhibition, the TL population responded to various doses of con A in the presence of Am B.

Amphotericin B and 5-fluorocytosine: effects on cell-mediated immunity

Although single-dose amphotericin B therapy appears to be immunostimulatory in mice, no data are available regarding the effects of chronic anti-fungal drug therapy on the immune system. We studied the effects on the guinea-pig cellular immune system of 4 weeks of treatment with amphotericin B, 5-fluorocytosine, or the combination of both drugs. The in vitro lymphocyte response to phytohaemagglutinin and the specific antigen, picryl human serum albumin (picHSA), were not affected by anti-fungal drug treatment. At 1.5 weeks of therapy with amphotericin B, skin test reactivity to picHSA was significantly reduced but returned toward normal by the end of 3.5 weeks of drug therapy. Macrophage migration inhibitory factor production by guinea-pig peripheral blood lymphocytes was significantly reduced after 4 weeks of amphotericin B therapy. No immunostimulatory properties could be ascribed to amphotericin B. 5-fluorocytosine had no effect on cellular immunity.