Use of immune modulators in nonspecific therapy of bacterial infections

Cytokine responses in campylobacteriosis: Linking pathogenesis to immunity

Campylobacter jejuni is an important enteric pathogen that causes diarrheas of different degrees of severity and several extra-intestinal manifestations, including Guillain-Barre syndrome. The variability of disease outcomes is thought to be linked to the immune response induced by C. jejuni. The virulence factors of C. jejuni induce a pro-inflammatory response, that is initiated by the intestinal epithelial cells, propagated by innate immune cells and modulated by the cells of the adaptive immune response. This review focuses on cytokines, that are reported to orchestrate the induction and propagation of pro-inflammatory immune response, and also those that are involved in control and resolution of inflammation. We describe the functional roles of a number of cytokines in modulating anti-Campylobacter immune responses: 1. cytokines of innate immunity (TNF-α, IL-6, and IL-8) as initiators of inflammatory response, 2. cytokines of antigen-presenting cells (IL-1β, IL-12, and IL-23) as promoters of pro-inflammatory response, 3. cytokines produced by T cells (IFN-γ, IL-17, IL-22) as activators of T cells, and 4. anti-inflammatory cytokines (IL-4 and IL-10) as inhibitors of pro-inflammatory responses. We highlight the roles of cytokines as potential therapeutic agents that are under investigation. In the end, we pose several questions that remain unanswered in our quest to understand Campylobacter immunity.

Ipomoea obscura (L.) enhances the functions of immunological effector cells, inhibits proinflammatory cytokines and nitric oxide production by LPS induced macrophages

Most of the synthetic chemotherapeutic agents available today are immunosuppressant, cytotoxic and exerts variety of side effects. Botanical based immunomodulators are often employed as supportive or adjuvant therapy to overcome the undesired effects of cytotoxic chemotherapeutic agents and to restore normal health. The methanolic extract of traditionally important medicinal plant Ipomoea obscura exhibited immunomodulatory activity in BALB/c mice. Intraperitoneal administration of five doses of the extract (10 mg/kg body wt) was found to enhance the total WBC count (13912 cells/mm(3)) on the 12(th) day, bone marrow cellularity (28.9 x 10(6)cells/femur) and number of alpha-esterase positive cells (1246 cells/4000 cells). Treatment with the extract along with the antigen, sheep red blood cells (SRBC), produced an enhancement in the circulating antibody titer and the number of plaque forming cells (PFC) in the spleen. Maximum number of PFC (267.6 PFC/10(6) spleen cells) was obtained on the 6(th) day. At the same time administration of Ipomoea obscura extract significantly reduced the elevated levels of proinflammatory cytokines and nitric oxide production by lipopolysaccharide stimulated macrophages. These results indicate the immunomodulatory activity of the alcoholic extract of Ipomoea obscura.

Isolation of beta-glucan from the cell wall of Saccharomyces cerevisiae

Beta-glucan, one of the major cell wall components of Saccharomyces cerevisiae (S. cerevisiae), has been found to enhance immune functions. At present study, we developed an optimal procedure to extract and purify beta-glucan. At first, yeast cells were grown in sabouraud dextrose agar and then cultured in yeast extract-peptone-glucose (YPG) broth. After incubation, cells were harvested, washed and disrupted by means of sonication method. The obtained cell walls were used to prepare alkali-soluble beta-glucan (glucan-S1). In this regard, 2% sodium hydroxide (NaOH) and 3% acetic acid were used in alkaline-acid extraction, respectively. This preparation contained 2.4% protein. In the next step, DEAE sephacel chromatography was used to remove remaining proteins (glucan-S2). Subsequently this preparation was applied into concanavalin-A sepharose column to remove manann. Finally, beta-glucan free of mannoprotein complexes was prepared (glucan-S3).

Avian genomics and the innate immune response to viruses

Viral diseases pose a significant threat to the poultry industry. However, there is currently a lack of antivirals and suitable vaccine adjuvants available to the poultry industry to combat this problem. The innate immune system is now recognised to be essential in the response to viral infection. However, in contrast to mammals, the innate immune response in chickens is relatively uncharacterised. The release of the full chicken genome sequence has accelerated the identification of genes involved in the immune response. The characterisation of these genes, including Toll-like receptors and cytokines has led to the identification of potential alternate antivirals and adjuvants.

Noncapsulated Klebsiella pneumoniae bearing mannose-containing O antigens is rapidly eradicated from mouse lung and triggers cytokine production by macrophages following opsonization with surfactant protein D

To better understand the relationship between the surface polysaccharides of pulmonary pathogens and components of the lung innate immune system, we employed selected serotypes of Klebsiella pneumoniae expressing distinct capsular polysaccharides and/or O antigen in a murine model of K. pneumoniae infection. In addition, we examined the effect of surfactant protein D (SP-D) on the cytokine response of human monocyte-derived macrophages to these serotypes in vitro. Noncapsulated mannose-containing O3 serotypes (K50/n and K55/n), which react efficiently with SP-D in vitro, triggered high levels of interleukin-1beta (IL-1beta) and IL-6 production. In vivo, they were more efficiently cleared from the lungs of mice but not from macrophage-depleted mice. They also were more efficiently internalized by alveolar macrophages in vivo. In contrast, galactose-containing O1 serotypes (K2/n and K21a/n), which interact poorly with SP-D, exhibited significantly lower cytokine production and less efficient pulmonary clearance and were ineffectively internalized by alveolar macrophages. These findings are consistent with in vitro results showing that production of IL-1beta and IL-6 mRNA and IL-6 protein by human macrophages exposed to mannose-bearing Klebsiella O serotypes is significantly increased by SP-D. Thus, survival of inhaled bacteria in the lung depends partially on the lipopolysaccharide structure of the bacteria and their interactions with innate immunity components. We speculate that an imbalance of host SP-D and therefore cytokine levels may result in high susceptibility of the host to the pathogen.

Molecular approaches to disease control

Recent advances in molecular biology, genomics, and immunology are revolutionizing our approach to managing infectious diseases of humans, livestock, and poultry. One of the most interesting additions to the armamentarium of research focusing on controlling infectious diseases has been a better understanding of how the host's innate immune system recognizes "danger" signals. Additionally, there has been recognition of the relationship between the innate and the specific arms of the immune system. For example, the recent discovery that CpG motifs can modulate immune responses has been used both as an adjuvant to enhance the responses to vaccines, as well as a direct immunostimulant to prevent infections. Using an Escherichia coli chicken model, we have been able to prevent cellulitis in chickens with CpG alone. Thus, CpG can be used immunoprophylactically to reduce infectious diseases. In addition, we will describe how CpG formulations with various antigens; recombinant proteins, peptides, and conventional vaccines can enhance immune responses to each of these different vaccine combinations. What is even more interesting is that CpG incorporation in vaccines can shift the immune response from a predominant T helper 2 (Th2)-like immune response generally induced by killed or subunit proteins to a much more balanced Th1-Th2 response. These immunomodulatory effects have significant implications for management of infectious diseases of all vertebrates.

Peptide immunomodulators versus infection; an analysis

A disease gets manifested only when the host immune system is not strong enough to fight off the infective agents. A number of small peptides both from natural and synthetic origin are found to be capable of modulating the immune response. While immune adjuvants are known to strengthen the immune response and help the host not to give way to the pathogens thereby preventing their establishment, the immunosuppressors are found useful in autoimmune conditions as well as in facilitating the organ transplants. Recent understanding of immune network, however, reveals its cross connectivity with the endocrine and central nervous systems as well. Thus, the inhibition and control of disease by planned restoration of homeostatis in these systems through immunomodulation is also possible.

CpG motifs in bacterial DNA and their immune effects

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Physiological rationale for suppression of fever

Two critical assumptions are made when prescribing antipyretic therapy. One is that fever is, at least in part, noxious, and the other is that suppression of fever will reduce, if not eliminate, the noxious effects of fever. At present, neither assumption has been validated experimentally.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Trends in immunotherapy of fungal infections

Fungal infections are the primary cause of mortality in patients with severely impaired host defense mechanisms, such as neutropenic patients with acute leukemia or those who have undergone bone marrow transplantation. In view of the unacceptably high mortality due to disseminated candidiasis, it is rational to focus on augmentation of host defense mechanisms in addition to conventional antifungal therapy. In vitro, a variety of immunomodulators, including tumor necrosis factor, interferon-g, and the hematopoietic growth factors, enhance the killing of Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans. Various studies have demonstrated beneficial effects of immunomodulatory therapy in animal models of disseminated candidiasis. For further preclinical and clinical studies, recombinant interferon-g, interleukin-1, granulocyte colony-stimulating factor, and the other hematopoietic growth factors are currently the most promising immunomodulators.

Protective effect of adenylate deaminase (from Penicillium lanoso-viride) against acute infections in mice

We examined the effects of the immunomodulator-adenylate deaminase (E.C. 3.5.4.6) from Penicillium lanoso-viride on experimental mice infections. Prophylactic intraperitoneal administration of adenylate deaminase (ADA) increased survival time and numbers of survivors after infection with Salmonella typhimurium, Pseudomonas aeruginosa and influenza A (H3N2) virus. Protection against influenza virus after intranasal ADA application was also observed. The influence of ADA was time and dose dependent. The most pronounced protection was obtained by administration of 3 U ADA/mice 24 h prior to infection. ADA had no antibiotic effect against these bacterial strains. Protective effects of ADA were studied in immunosuppressed mice under different regimes of treatment including cyclosporin A and trypan blue. The results indicated, that the protective effect of ADA is of a complex nature and probably depends on both T-cell and macrophage components.

Characterization of the non-specific humoral and cellular antiviral immunity stimulated by the chloroform-methanol residue (CMR) fraction of Coxiella burnetii

Modulation of the immune response by the chloroform-methanol residue (CMR) of phase I Coxiella burnetii whole cell was studied in Rift Valley fever virus-infected, or in naive endotoxin-non-responder C3H/HeJ mice. A single dose of CMR completely protected the mice from viral infection. Treating virus-infected mice with antibodies directed against interferons alpha/beta (IFN-alpha beta) and gamma (IFN-gamma) eliminated the CMR-induced protection. CMR stimulated the production of high levels of IFN-alpha/beta and 2'-5'-oligoadenylate synthetase activities in sera of the CMR-treated mice. IFN-gamma was present in supernatants of cultured spleen cells of CMR-treated, virus-infected mice, but not in their serum. Priming mice with CMR optimized the release of INF-gamma, interleukin-1 alpha (IL-1 alpha) and IL-6 from splenocytes in vitro. When stimulated in vitro, IL-2 and granulocyte-macrophage stimulating factor (GM-CSF) did not require in vivo priming for release from cultured spleen cells. Fluorescence-assisted cytometry of CMR-treated mouse spleen cells showed there was a CMR-dependent increase in the percentage of T-cells and Ia-positive T-cells. There also was a biphasic increase in the ratio between Th (L3T4) and Ts (Lyt2) cells. Biological activities stimulated by CMR indicate that CMR is a potent immunostimulant, which may modulate specific and non-specific antiviral responses.

Interleukin-1 (IL-1)-induced resistance to bacterial infection: role of the type I IL-1 receptor

Pretreatment with a low dose of recombinant human interleukin-1 beta (IL-1) (3 to 30 micrograms/kg) 24 h before a lethal Pseudomonas aeruginosa infection prolongs survival in neutropenic mice. We investigated the role of the type I IL-1 receptor (IL-1RI) and IL-1RII in this IL-1-induced protection by using a specific IL-1 receptor antagonist (IL-1-Ra), which blocks effects mainly via IL-1RI. Pretreatment with IL-1Ra before IL-1 partially blocked the IL-1-induced enhanced survival, whereas pretreatment with a specific neutralizing monoclonal antibody to IL-1RI (35F5) eliminated the IL-1 induced protection. The nonapeptide fragment 163-171 of recombinant human IL-1 beta, which possesses the immunoadjuvant but not the inflammatory effect of the entire molecule via a non-receptor-mediated signal transduction process, did not reproduce the IL-1-induced protection. IL-1-induced protection was associated with reduced serum aspartate aminotransferase and alanine aminotransferase concentrations in conjunction with ameliorated histopathology of the liver. These findings may be due to reduced cytokine production and cytokine sensitivity of target cells after infection. We conclude that the IL-1-induced nonspecific resistance to infection is mediated by cells bearing IL-1RI and is associated with a reduction of liver damage.

Interleukin-1 and related pro-inflammatory cytokines in the treatment of bacterial infections in neutropenic and non-neutropenic animals

Bacterial infections in the immunocompromized host cause considerable mortality, and even the recently developed antimicrobial strategies often fail to cure these infections, especially in granulocytopenic patients. Cytokines and hematopoietic growth factors have been shown to stimulate host defense mechanisms in vitro and in vivo. We discuss the possible role of the pro-inflammatory cytokines interleukin-1, tumor necrosis factor-alpha, interleukin-6 and interleukin-8 as modulators of host resistance to bacterial infections. Interleukin-1 has been shown effective in various animal models of potentially lethal bacterial infection, even during severe granulocytopenia. The protective mechanism of interleukin-1 may be mediated via downregulation of cytokine receptors and cytokine production, and via induction of acute phase proteins. Moreover, in subacute and chronic infections interleukin-1 interferes with microbial outgrowth, via mechanisms that have only been partially elucidated.

Cytokines in the treatment of fungal infections

The incidence of invasive fungal infections in the immunocompromized host has increased during the past decade. Even the recently developed antifungal drugs are unable to cure these infections in patients with severely impaired host defense mechanisms. Cytokines have great potential to augment host resistance and as adjunctive therapy of invasive mycoses. We discuss the mechanisms of host defense against invasive candidiasis, aspergillosis, and cryptococcosis, and review the use of cytokines and growth factors in this setting. Interleukin-1 has been shown effective in an animal model of disseminated candidiasis, even during severe granulocytopenia. Interferon-gamma has been very effective as a modulator of resistance against a variety of fungal infections in vitro. The effect of interferon-gamma against disseminated candidiasis has been demonstrated in a mouse model. Activation of neutrophils is the main mechanism by which interferon-gamma enhances the elimination of Candida, and consequently the agent is not effective in severely granulocytopenic animals. Data on the role of colony-stimulating factors against fungal pathogens are accumulating, and trials with these agents for hematologic patients with invasive fungal infections are now being performed.

Cytokines in the treatment of leishmaniasis: from studies of immunopathology to patient therapy

The genus Leishmania, an obligate intramacrophage parasite, causes a wide spectrum of clinical diseases. It is worldwide in distribution and causes 20 million new cases annually with an at risk population of approximately 1.5 billion persons. The most severe forms are associated with high morbidity, mortality and relapses with conventional therapy. The therapeutic issues and responses to standard and alternative therapies are reviewed. Recent developments in molecular biology and immunology methods employed in the study of leishmaniasis have defined an intricate interaction of the parasite with host immune system. Perturbation of the host immune responses may be part of the survival mechanisms of Leishmania. In murine model, the finding of T helper cells that differ by their panel of cytokines has allowed a more precise definition of immunopathogenesis of leishmaniasis. Preliminary data from leishmaniasis patients lend support to this concept of altered immunomodulation. Furthermore, the data from leishmaniasis patients lend support to this concept of altered enhancement of therapeutic response by interferon-gamma has provided a new approach for treatment of patients using recombinant cytokines and for the study of the disease. Current research for early diagnosis, alternative therapies and need for vaccines are reviewed in the context of the immunopathology of leishmaniasis.

Clinical immunology and infectious diseases

Without the application of immunology, understanding of the pathogenesis and pathophysiology of infectious diseases would be severely retarded. The development new vaccines for the prevention of infectious diseases has been based on new immunologic findings. Immunodiagnostic modalities have provided for the growth of diagnostic techniques for infectious diseases. Clinical immunology also has laid the groundwork for immunotherapies using the old intravenous immunoglobulin preparations and the new monoclonal antibodies, cytokines, and interferons.

Roles of tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor, platelet-activating factor, and arachidonic acid metabolites in interleukin-1-induced resistance to infection in neutropenic mice

Treatment with a single low dose (80 to 800 ng) of interleukin-1 (IL-1) 24 h before a lethal bacterial challenge in granulocytopenic and in normal mice enhances nonspecific resistance. The mechanism behind this protection has only partially been elucidated. Since IL-1 induces production of tumor necrosis factor alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), platelet-activating factor (PAF), and arachidonic acid metabolites, we investigated the potential role of these substances in IL-1-induced protection. Low doses of murine TNF-alpha but not of human TNF-alpha enhanced survival, suggesting an effect via the type II TNF receptor rather than the type I TNF receptor, which has little species specificity. In line with this TNF-alpha-induced protection from infection, pretreatment with a low dose of a rat anti-murine TNF-alpha monoclonal antibody tended to inhibit IL-1-induced protection, suggesting a role of TNF-alpha as a mediator of IL-1-induced enhanced resistance to infection. Pretreatment with higher doses of anti-TNF-alpha, however, showed a dose-related protective effect per se, which could be further enhanced by a suboptimal dose of IL-1. A combination of optimal doses of anti-TNF-alpha and IL-1 produced an increase in survival similar to that produced by separate pretreatments. This lack of further enhancement of survival by combined optimal pretreatments suggests a similar mechanism of protection, most likely attenuation of deleterious effects of overproduced proinflammatory cytokines like TNF-alpha during lethal infection. Pretreatment with different doses of GM-CSF before a lethal Pseudomonas aeruginosa challenge in neutropenic mice did not enhance survival. Different doses of WEB 2170, a selective PAF receptor antagonist, of MK-886, a selective inhibitor of leukotriene biosynthesis, or of several cyclooxygenase inhibitors did not reduce the protective effect of IL-1 pretreatment. We conclude that IL-1-induced nonspecific resistance is partially mediated by induction of TNF-alpha and not by GM-CSF, PAF, and arachidonic acid metabolites. The mechanism of action of IL-1 seems to be similar to that of anti-TNF-alpha.

Modulation of mucosal immunity against Campylobacter jejuni by orally administered cytokines

The effect of oral recombinant interleukin (rIL) treatment on the course of Campylobacter jejuni infection and the development of mucosal immunity in mice was investigated. rIL-2, rIL-5, and rIL-6 were administered to mice at 24 and 6 h before infection and at 0, 24, and 48 h after infection with C. jejuni HC, and the subsequent development of an immune response and intestinal colonization resistance were determined. In this model, orally administered cytokines retained their biological activities with no apparent side effects. Following infection, initial bacterial counts in fecal samples collected from cytokine-treated and untreated mice were similar. However, within 48 h of infection a greater than 3-log-unit reduction in the number of C. jejuni shed in the feces was found for rIL-6-treated animals. Colonization levels were similarly reduced in rIL-5-treated mice, although the rate of clearance was somewhat slower. In contrast, rIL-2 treatment had no significant effect on colonization levels compared with that in controls. Oral rIL-6 treatment was also associated with enhanced intestinal and systemic Campylobacter-specific immunoglobulin A responses compared with those observed in either rIL-5- or rIL-2-treated animals. Upon rechallenge, initial colonization in all cytokine-treated groups was approximately 2 log units lower than that in controls. However, local infection was controlled only in rIL-2-treated mice over time. rIL-5 and rIL-6 treatment had only a marginal effect on colonization resistance following rechallenge. On the basis of these results, it appears that rIL-5 or rIL-6 may function to modulate the induction and/or expression of anti-C. jejuni immunity through different mechanisms.

Role of acute-phase proteins in interleukin-1-induced nonspecific resistance to bacterial infections in mice

Treatment with a single low dose (80 to 800 ng) of interleukin-1 (IL-1) 24 h before a lethal bacterial challenge of granulocytopenic and normal mice enhances nonspecific resistance. Since IL-1 induces secretion of acute-phase proteins, liver proteins which possess several detoxifying effects, we investigated the role of these proteins in the IL-1-induced protection. Inhibition of liver protein synthesis with D-galactosamine (GALN) completely inhibited the IL-1-induced synthesis of acute-phase proteins. GALN pretreatment abolished the protective effect of IL-1 on survival completely (neutropenic mice infected with Pseudomonas aeruginosa) or partially (nonneutropenic mice infected with Klebsiella pneumoniae). Pretreatment with IL-6, a cytokine induced by IL-1, did not reproduce the protection offered after IL-1 pretreatment, nor did it enhance or deteriorate the IL-1-enhanced resistance to infection. A protective effect of IL-1 via effects on glucose homeostasis during the acute-phase response was investigated by comparing plasma glucose levels in IL-1-treated mice and control mice before and during infection. Although glucose levels in IL-1-pretreated mice were somewhat higher in the later stages of infection, no significant differences from levels in control mice were present, and the glucose levels in control-treated animals never fell to hypoglycemic values. We conclude that the IL-1-induced nonspecific resistance is mediated neither by the induction of IL-6 nor by the effects of IL-1 on glucose homeostasis. Acute-phase proteins generated after IL-1 pretreatment, however, seem to play a critical role in the IL-1-induced protection to infection.

The use of recombinant human interleukin-2 in treating infectious diseases

Data from animal models indicate that interleukin-2 is potentially valuable in the treatment of a variety of infectious diseases of viral, fungal, protozoal, bacterial, and mycobacterial origin. The role of interleukin-2 in resistance to infection with human immunodeficiency virus or Mycobacterium leprae (the causative agent of leprosy) has recently been studied in detail. Data from animal models and clinical trials indicate that relatively low doses of interleukin-2 effectively stabilize or reverse the course of these infections. The recent characterization of Th1 and Th2 helper T cells, and their relationship to the control of infectious diseases, are revealing the mechanisms involved in producing disease. Increased understanding of these mechanisms may help extend interleukin-2 therapy to other clinical applications.

Efficacy of granulocyte colony-stimulating factor and RU-40555 in combination with clarithromycin against Mycobacterium avium complex infection in C57BL/6 mice

We compared the activities of two different biological-response modifiers with that of clarithromycin against Mycobacterium avium complex infection in C57BL/6 mice. Mice were pretreated daily with clarithromycin (50 mg/kg of body weight subcutaneously [s.c.]), RU-40555 (100 mg/kg s.c.), or granulocyte colony-stimulating factor (G-CSF) at low dose (15 micrograms/kg intraperitoneally [i.p.]) or high dose (300 micrograms/kg i.p.) 3 days before intravenous challenge with 2.5 x 10(7) CFU of the MO-1 strain of M. avium complex. Mice were treated daily until sacrifice at day 1, 8, 15, or 21 after challenge, and the numbers of CFU were measured per gram of tissue in lung and spleen. Compared at day 21 with control treatment, clarithromycin significantly decreased the level of infection in spleen (P < 0.0001) and lungs (P < 0.0001). Compared with control treatment, G-CSF at low dose had no activity, but G-CSF in combination with clarithromycin was more effective than clarithromycin alone in spleen (P < 0.05) and lungs (P < 0.015). The high dose of G-CSF was as effective as the low dose. RU-40555 alone had no beneficial activity. The RU-40555-clarithromycin combination was more effective than control treatment in spleen (P = 0.0001) and lungs (P < 0.0005) and more effective than clarithromycin alone in spleen (P < 0.009) but not in lungs. Thus, our experiments suggest that clarithromycin alone or in combination with G-CSF should be further evaluated for the prophylaxis of M. avium complex infection.

Interleukin-1-induced nonspecific resistance to bacterial infection in mice is not mediated by glucocorticosteroids

Preexposure to a low dose of interleukin-1 (IL-1; 3 to 30 micrograms/kg) 24 h before a lethal gram-negative bacterial infection prolonged survival in normal and granulocytopenic mice. To examine whether this protective effect is mediated by glucocorticosteroids, we first measured corticosterone concentrations in mice after administration of 80 and 800 ng of IL-1. IL-1 induced a dose-dependent increase in corticosterone levels in plasma. Next, the corticosterone peak induced by a protective dose of IL-1 (800 ng) was simulated by administration of synthetic human adrenocorticotropic hormone 1-24 (ACTH) in normal and neutropenic mice. Although corticosterone levels induced by pretreatment with IL-1 or ACTH were virtually identical, the ACTH-induced corticosterone peak was not associated with protection against Klebsiella pneumoniae infection in normal mice and Pseudomonas aeruginosa infection in neutropenic mice. This indicates that the protective effect of IL-1 pretreatment against gram-negative bacterial infection is not mediated by elevated levels of glucocorticosteroids. In addition, we found that plasma corticosterone concentrations during K. pneumoniae infection were significantly lower after pretreatment with IL-1 than after pretreatment with ACTH or vehicle, probably reflecting the better physical condition of IL-1-treated mice.

Pharmacoeconomics of antibacterial treatment

Antibacterial drugs account for between 3 and 25% of all prescriptions, between 6 and 21% of the total market value of drugs in a single country, and up to 50% of the drug budget in hospitals. Bacterial infection is widely perceived as disease caused by harmful outside agents which can be isolated and tested to select the best drug for treatment. In fact, the need for any treatment and the pros and cons of different drugs are just as debatable as in any other therapeutic area. Moreover, the bacteria which make up the normal flora of the body fulfil important roles, so that the ecological implications of treatment for the individual and for society should be considered in assessing the costs and consequences of antibacterial treatment. In this review we outline the most important issues relating to the treatment of bacterial infection in the community and in the hospital, contrasting information from developed and developing countries where appropriate. We review the existing literature on economic evaluation, but in general most of the literature deals with containing the costs of antibacterial drugs in hospitals, and there are many gaps in the literature on cost-effectiveness of treatment. Consequently there are still extreme variations in medical practice which present a challenge for future evaluation. As the outcomes of antibacterial treatment are apparent in a few weeks or months, this is an ideal field for testing pharmacoeconomic methodology. The desire to overcome medical practice variation through consensus statements should be avoided. Instead we recommend wider application of decision analysis to acknowledge that choices exist for the diagnosis and treatment of bacterial infection and to gather information about the implications of these choices. Much of the existing literature would be improved by a more explicit definition of costs. Direct costs to the health services should be distinguished from non medical costs. Moreover, the analysis should consider whether savings from one budget result in costs to another health service budget, or to the patient (transfer costs). These deficiencies in cost analysis will be relatively easy to correct. Of more concern is the fact that the efficacy of much antibacterial treatment is either totally debatable, or variable, depending on factors such as the type of patient treated or the quality of delivery of treatment.(ABSTRACT TRUNCATED AT 400 WORDS)