Synergy between acylureidopenicillins and immunoglobulin G in experimental animals

Seventy-Five Years of Research on Protein Binding

This review summarizes evidence that the impact of protein binding of the activity of antibiotics is multifaceted and more complex than indicated by the numerical value of protein binding alone. A plethora of studies has proven that protein binding of antibiotics matters, as the free fraction only is antibacterially active and governs pharmacokinetics. Several studies have indicated that independent from protein binding of immunoglobulin G, albumin, α1-acid-glycoprotein, and pulmonary surfactant acted synergistically with antibacterial agents, thus suggesting that some intrinsic properties of serum proteins may have mediated serum-antibiotic synergisms. It has been demonstrated that IgG and albumin permeabilized Gram-negative and Gram-positive bacteria and facilitated the uptake of poorly penetrating antibiotics. Alpha-1-acid-glycoprotein and pulmonary surfactant also exerted a permeabilizing activity, but proof that this property results in a sensitizing effect is missing. The permeabilizing effect of serum proteins may explain why serum-antibiotic synergisms do not represent a general phenomenon but are limited to specific drug-bug associations only. Although evidence has been generated to support the hypothesis that native serum proteins interact synergistically with antibiotics, systematic and well-controlled studies have to be performed to substantiate this phenomenon. The interactions between serum proteins and bacterial surfaces are driven by physicochemical forces. However, preparative techniques, storage conditions, and incubation methods have a significant impact on the intrinsic activities of these serum proteins affecting serum-antibiotic synergisms, so these techniques have to be standardized; otherwise, contradictory data or even artifacts will be generated.

Antibodies in infectious diseases: polyclonals, monoclonals and niche biotechnology

Antibody preparations have a long history of providing protection from infectious diseases. Although antibodies remain the only natural host-derived defense mechanism capable of completely preventing infection, as products, they compete against inexpensive therapeutics such as antibiotics, small molecule inhibitors and active vaccines. The continued discovery in the monoclonal antibody (mAb) field of leads with broadened cross neutralization of viruses and demonstrable synergy of antibody with antibiotics for bacterial diseases, clearly show that innovation remains. The commercial success of mAbs in chronic disease has not been paralleled in infectious diseases for several reasons. Infectious disease immunotherapeutics are limited in scope as endemic diseases necessitate active vaccine development. Also, the complexity of these small markets draws the interest of niche companies rather than big pharmaceutical corporations. Lastly, the cost of goods for mAb therapeutics is inherently high for infectious agents due to the need for antibody cocktails, which better mimic polyclonal immunoglobulin preparations and prevent antigenic escape. In cases where vaccine or convalescent populations are available, current polyclonal hyperimmune immunoglobulin preparations (pIgG), with modern and highly efficient purification technology and standardized assays for potency, can make economic sense. Recent innovations to broaden the potency of mAb therapies, while reducing cost of production, are discussed herein. On the basis of centuries of effective use of Ab treatments, and with growing immunocompromised populations, the question is not whether antibodies have a bright future for infectious agents, but rather what formats are cost effective and generate safe and efficacious treatments to satisfy regulatory approval.

Controlled-release and local delivery of therapeutic antibodies

Human and humanised antibodies are now poised to become a major new class of protein-based therapeutic agents. A significant fraction of new drugs in clinical testing (approximately 20% in 2002) are antibody classes. Monoclonal antibodies (mAbs) with high affinities against newly discovered disease targets, both cellularly and extracellularly, are now clinically proven to elicit high bioactivities against numerous diseases, including tumours, infections, asthma, inflammation, arthritis and osteoporosis. Clinical humanised antibody delivery is typically intravenous, with large multiple doses (grams) required for systemic volumes of distribution. Due to the relatively high costs of both this drug type, and its common mode of administration, alternatives are sought where doses might be reduced and the bioavailability and efficacy enhanced. Local, controlled-release methods that deliver antibodies locally to site of disease, offer new possibilities with these potential advantages. However, protein drugs frequently exhibit formulation challenges when packaged in delivery vehicles, and as globular proteins, antibodies are no exception. Several examples of mAb controlled-release and local delivery strategies against several disease targets are reviewed. Importantly, several antibody delivery methods work in tandem with existing clinically-accepted therapeutics, sometimes exhibiting potentiating or synergistic effects in animal models with small molecule, systemically administered drugs.

Locally delivered polyclonal antibodies potentiate intravenous antibiotic efficacy against gram-negative infections

PURPOSE

Comparison of the anti-microbial efficacy of locally delivered antibodies in tandem with conventional systemic administration of ceftazidime antibiotic therapy in two lethal gram-negative animal infection models.

METHODS

Previously published lethal E. coli-induced closed peritonitis and Klebsiella-induced burn wound infections were generated in outbred female CF-1 mice cohorts. Pooled human polyclonal antibodies were injected locally into sites of infection in these mice simultaneously with intravenous infusions of the broad-spectrum antibiotic, ceftazidime. Mouse survival was compared in sham control cohorts vs. both ceftazidime-alone or antibody-alone systemically infused cohorts as well as local antibody-systemic ceftazidime combination therapy cohorts. Microbial burdens in blood and tissue samples (by agar plating), as well as interleukin-6 cytokine levels (using ELISA) correlated with sepsis, were monitored in sacrificed animals as a function of antimicrobial treatment regimen.

RESULTS

Local delivery of human polyclonal antibodies to infection sites was shown to produce synergistic therapeutic efficacy in combination with systemic antibiotic administration in these lethal wound infection models in mice. Enhanced benefits of the unique combination therapy included host survival, bacterial burden both locally and systemically, and IL-6 levels in host serum.

CONCLUSIONS

Commercial pooled human antibodies contain a broad spectrum of antimicrobial activity against gram-negative pathogens. Prevention of systemization of infection correlates with host survival in these models. Local control of infection using doses of local, high-titer polyclonal antibodies can enhance traditional approaches to curb systemic spread of infection using intravenous antibiotics. Antibodies provide antimicrobial efficacy independent of known pathogen resistance mechanisms.

Antibodies against beta-lactamase can improve ceftazidime treatment of lung infection with beta-lactam-resistant Pseudomonas aeruginosa in a rat model of chronic lung infection

To test the hypothesis that antibodies against the chromosomal beta-lactamase of Pseudomonas aeruginosa (a beta ab) might act as beta-lactamase inhibitors in patients with cystic fibrosis and chronic lung infection with P. aeruginosa, we compared in a rat model of chronic lung infection the efficacy of treatment with ceftazidime in beta-lactamase-immunized (group I) and non-immunized (group II) rats. Chronic lung infection was established with alginate-embedded P. aeruginosa producing high amounts of beta-lactamase in 133 Lewis rats. Prior to infection, group I (66 rats) was immunized three times at 2-week intervals with purified beta-lactamase in incomplete Freund's adjuvant (IFA) and group II (67 rats) received IFA. Ceftazidime treatment was initiated after challenge and continued for 10 days, after which the rats were sacrificed and the lung bacteriology and pathology were analysed. Rat serum was analysed for the beta-lactamase inhibitory activity and a beta ab-specific IgG and IgG subclasses titres. Beta-lactamase inhibitory activity was found only in sera of rats belonging to group I and it was used to divide these rats into two subgroups: rats whose sera inhibited > or = 75% of beta-lactamase activity (responders) and rats whose sera inhibited < or = 25% of beta-lactamase activity (non-responders). The responder subgroup had significantly smaller pathological areas in the lungs and lower cfu/ml lung homogenate compared to the non-immunized group (p=0.02 and p=0.01, respectively) and compared to the non-responder subgroup (p=0.008 and p=0.0001, respectively). On the day of challenge, significantly higher titres of a beta ab-specific IgG and IgG subclasses antibodies were found in the responders compared to the non-responders (p<0.0001). In the responder subgroup the avidity of IgG a beta ab was significantly higher than in the non-responder subgroup (p=0.0003). Our study showed that a beta ab with beta-lactamase inhibitory activity raised by immunization with beta-lactamase can improve the outcome of treatment with ceftazidime of resistant P. aeruginosa in a rat model of chronic lung infection.

Prophylactic treatment of gram-positive and gram-negative abdominal implant infections using locally delivered polyclonal antibodies

The increasing clinical incidence and host risk of biomaterial-centered infections, as well as the reduced effectiveness of clinically relevant antibiotics to treat such infections, provide compelling reasons to develop new approaches for treating implanted biomaterials in a surgical context. We describe the direct local delivery of polyclonal human antibodies to abdominal surgical implant sites to reduce infection severity and mortality in a lethal murine model of surgical implant-centered peritoneal infection. Surgical implant-centered peritonitis was produced in 180 female CF-1 mice by the direct inoculation of surgical-grade polypropylene mesh disks placed in the peritoneal cavity with lethal doses of either methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. Mice randomly received a resorbable antibody delivery vehicle at the implant site: either a blank carboxymethylcellulose (CMC) aqueous gel or the same CMC gel containing 10 mg of pooled polyclonal human immunoglobulin G locally on the implant after infection, either alone or in combination with systemic doses of cefazolin or vancomycin antibiotics. Human antibodies were rapidly released (first-order kinetics) from the gel carrier to both peritoneal fluids and serum in both infection scenarios. Inocula required for lethal infection were substantially reduced by surgery and the presence of the implant versus a closed lethal peritonitis model. Survival to 10 days with two different gram-negative P. aeruginosa strains was significantly enhanced (p < 0.01) by the direct application of CMC gel containing antibodies alone to the surgical implant site. Human-equivalent doses of systemic vancomycin provided a significantly improved benefit (p < 0.01) against lethal, implant-centered, gram-positive MRSA infection. However, locally delivered polyclonal human antibodies in combination with a range of systemic vancomycin doses against MRSA failed to improve host survival. Successful antibody therapy against gram-negative, implant-centered infections complements the clinically routine use of systemic antibiotics, providing a mechanism of protection independent of antibiotic resistance.

Treatment of sepsis in cardiac surgery: role of immunoglobulins

Cardiopulmonary bypass (CPB) is associated with an injury that may cause pathophysiological changes such as systemic inflammatory response syndrome, multiple organ dysfunction syndrome, and mediator-induced multiorgan failure. Systemic endotoxinaemia, release of proinflammatory cytokines, and interactions between neutrophils and endothelium have been reported to correlate with a high incidence of organ dysfunction, infection and sepsis following cardiac surgery. This review discusses the dysregulation of the immune response as a major reason for the higher susceptibility to infections following cardiac surgery, various treatment strategies to reduce CPB-induced inflammation, and especially the prophylactic use of immunoglobulins in cardiac surgery.

Locally delivered antibodies combined with systemic antibiotics confer synergistic protection against antibiotic-resistant burn wound infection

BACKGROUND

Nosocomially derived gram-negative infections, particularly from antibiotic-resistant pathogens, are a cause of morbidity in patients with severe burn wounds.

METHODS

Locally delivered polyclonal antibodies and systemically infused ceftazidime were combined in a lethal murine burn wound model against a virulent Pseudomonas aeruginosa strain that exhibits intermediate resistance to ceftazidime.

RESULTS

Survival was synergistically enhanced in cohorts of burned mice treated both locally (subeschar) with pooled polyclonal human immunoglobulin G (1-mg dose) and intravenously with infused ceftazidime (0.44 mg dose). Enhancement of survival correlated with reduced bacterial quantitation in local and systemic tissue observed in separate burned cohorts. Burned, infected mice treated prophylactically with either individual treatment at the same dose or a combination of both treatments administered systemically showed no survival enhancement as compared with the untreated control group.

CONCLUSION

Treatment of antibiotic-resistant burn wound infections with antibiotics together with locally delivered immunoglobulins may improve antibiotic protective effects against antibiotic-resistant pathogens.

Supplemental immune globulins in sepsis

Intravenous immune globulins are widely used as supplemental treatment of sepsis, septic shock and systemic inflammation in the critically ill, although this indication has at best been validated in part. Likely beneficial mechanisms of action may include the improvement of serum bactericidal activity due to neutralizing and opsonizing immunoglobulin (Ig)G- and IgM-antibodies, as well as stimulation of phagocytosis and neutralization of bacterial endo- and exotoxins; another attractive mode of action may represent immune globulin-mediated modification and specific suppression of proinflammatory cytokine release from endotoxin- and superantigen-activated blood cells. For the "entire group of patients with sepsis and septic shock" a reduction in mortality by intravenous immune globulin could not be documented; however, in the score-based immunoglobulin in sepsis (SBITS)-study with 653 patients included, a moderate improvement in sepsis morbidity and multiple organ dysfunction syndrome was demonstrated. In defined sepsis subgroups, a reduction in mortality by intravenous immune globulin has been seen in individual small, not yet confirmed trials. Finally, the incidence of some severe infections in well characterized "patients at risk" and "operations at risk" is reduced by intravenous immune globulin prophylaxis. Thus, intravenous immune globulin is not a "magic bullet"of sepsis treatment, but it may reduce morbidity and thereby represent a useful piece of stone in the therapeutic mosaic of sepsis treatment.

Lymphocyte function in wound healing and following injury

BACKGROUND

Injury activates a cascade of local and systemic immune responses.

METHODS

A literature review was undertaken of lymphocyte function in wound healing and following injury.

RESULTS

Lymphocytes are not required for the initiation of wound healing, but an intact cellular immune response is essential for a normal outcome of tissue repair. Injury affects lymphocyte immune mechanisms leading to generalized immunosuppression which, in turn, increases host susceptibility to infection and sepsis. Although the exact origin of post-traumatic immunosuppression remains unknown, stress hormones and immunosuppressive factors, such as inflammatory cytokines, prostaglandin E2 and nitric oxide, affect lymphocyte function adversely. Post-traumatic impairment of T lymphocyte immune function is reflected in decreased lymphocyte numbers, as well as altered T cell phenotype and activity. Antibody-producing B lymphocytes are variably affected by injury, probably secondary to alterations of T lymphocyte function, as a result of their close interaction with helper T cells. Therapeutic modulation of the host immune response may include non-specific and specific interventions to improve overall defence mechanisms.

CONCLUSION

Early resuscitation to restore lymphocyte function after injury is important for tissue repair and the prevention of immunosuppression.

Study of some phagocyte membrane receptors in patients receiving intravenous polyvalent immunoglobulins as adjunct treatment for nosocomial pneumonia

PURPOSE

Phagocytosis is a major mechanism of defense against bacterial infections. The ingestion of bacteria by phagocytes involves a variety of cell membrane recognition structures and, among them, immunoglobulin receptors. The aim of this study was to test the phagocytic activity of granulocytes and monocytes of intensive care unit (ICU) patients, and to evaluate the effects of intravenous polyvalent immunoglobulins (IVIG) used as adjunct treatment of nosocomial pneumonia on some phagocyte membrane receptors of these patients.

MATERIALS AND METHODS

The phagocytic activity of granulocytes and monocytes of 41 mechanically ventilated patients with nosocomial bacterial pneumonia was studied during the acute phase of infection. These ICU patients were compared with 21 hospitalized, noninfected volunteer patients hospitalized in a medical ward. Peripheral blood granulocytes and monocytes were studied. Of the 41 ICU patients, after randomization, 21 received IVIG at a dose of 1 g/kg for 3 days. The 41 ICU patients were compared with the 21 non-ICU, noninfected hospitalized controls. The 21 ICU patients who received 3 days of IVIG were also compared with the 20 ICU patients not receiving IVIG. Cells were tested in standard immunoglobulin-free medium (fetal calf serum) and in the presence of patients' serum. Blood granulocytes and monocytes were purified and separately exposed to three types of particles: antibody-coated erythrocytes (to test immunoglobulin receptors), opsonized zymosan (to test C3 receptors), and glutaraldehyde-treated erythrocytes (to test lectinlike or other nonspecific binding sites). Phagocytosis and superoxide anion production (oxidative burst) were measured.

RESULTS

Granulocytes of ICU patients compared with those of non-ICU, noninfected patients exhibited a substantial decrease of zymosan ingestion (P < .05), whereas phagocytosis of other particles was normal. Monocytes from the ICU patients, compared with those of the non-ICU, noninfected patients, displayed an unselective overall decrease of phagocytic ability for the three particle types (P < .05). The phagocytosis activity of the three membrane receptor species of blood monocytes and granulocytes of ICU patients was not significantly modified by the IVIG infusion. For both monocytes and granulocytes, no significant improvement was observed in the fraction of cells that ingested at least one foreign particle and the mean number of particles per cell having phagocytized at least one foreign particle. Granulocyte and monocyte functions were also tested by the production of reduced ferricytochrome and no significant improvement in the oxidative burst was observed after infusion of IVIG.

CONCLUSION

Infected ICU patients display a deficiency of phagocytosis membrane receptors of blood granulocytes and monocytes. The addition of IVIG to standard therapy does not improve the phagocytic activity of ICU patients with nosocomial pneumonia.

Effects of immunoglobulin G and low-dose amphotericin B on Candida albicans infections in burned mice

Candidiasis causes serious problems for compromised hosts. Effective treatments for Candida albicans infections are few. To see if immunoglobulin (Ig) therapy could be beneficial, burn-immunocompromised mice were treated intravenously with 2.5 mg of five different IgG preparations 48 h postburn and post-C. albicans challenge. Despite up to fourfold differences in titer (1:1,600 to 1:6,400) to C. albicans, all preparations improved 10-day survival about 30% (P less than 0.0001). Treatment with a low dose of amphotericin B (AmB; 0.09 mg/kg of body weight) intravenously 24 and 48 h after burn and challenge improved survival 9 to 45% (P less than 0.0001). Treatment with a low dose of AmB plus IgG showed the same results as treatment with AmB alone and better results than treatment with IgG alone. Quantitative renal cultures from burned mice treated with AmB plus one IgG preparation, Sandoglobulin, showed that C. albicans counts decreased in sham-treated mice from 7.21 +/- 0.15 log10 CFU/g (mean +/- standard error of the mean) to 5.31 +/- 0.34, which was significantly less than counts with AmB (6.11 +/- 0.35) or Sandoglobulin (6.39 +/- 0.18) treatment alone. We conclude that (i) by using decreases in mortality and in renal fungal load as end points, treatment with IgG preparations alone or with a low dose of AmB alone protected burn-immunocompromised mice from candidiasis; (ii) though AmB plus one IgG preparation significantly decreased renal fungal load, the combination did not significantly decrease mortality beyond that found with AmB alone; and (iii) survival data did not correlate with IgG titers to C. albicans.

Supplemental immunoglobulin (ivIgG) treatment in 163 patients with sepsis and septic shock--an observational study as a prerequisite for placebo-controlled clinical trials

In a multicenter observational study of 163 medical and surgical patients with a total of 173 episodes of sepsis or septic shock (Elebute sepsis score: 19.0 +/- 0.5), the effects of supplemental i.v. immunoglobulin (i.v. IG) treatment (unmodified polyvalent IgG pH 4.25, n = 123; for Pseudomonas sepsis, n = 50, Pseudomonas IgG) on multiple organ failure (MOF) were investigated by means of APACHE II score changes (pretreatment: 23.7 +/- 0.6). In 44% of the cases ("responders"), a prompt improvement in APACHE II score (defined as decrease greater than or equal to 4) was evident from day 0 to day 4 after onset of therapy, thus being in close time relationship to the i.v. IG administration. This improvement, associated with a better prognosis (mortality 24% vs. 55%), was found in all subgroups, most importantly the following: polyvalent IgG vs. Pseudomonas IgG treatment; medical vs. surgical patients; moderate vs. severe MOF; and gram-positive vs. gram-negative septicemia. In a small-sized second comparative nonrandomized control group (n = 27, antibiotic treatment alone) of septic patients (Elebute: 14.7 +/- 1.0) with similar MOF severity (APACHE II: 23.6 +/- 1.4), the response rate (30%) was, though not statistically significant, lower by one-third. The optimal baseline score ranges for patient inclusion into future placebo-controlled randomized i.v. IG trials were found to be 20-35 for the APACHE II score and 12-27 for the Elebute score.

Intravenous immunoglobulins: pharmacological aspects and therapeutic use

The requirements for a present-day IVIG preparation are outlined. These are mainly: fully preserved activities of the recognition and effector functions of the IgG molecule, a normal subclass distribution, and a normal half-life after infusion. The therapeutic uses of IVIG preparations are discussed as follows: Antibody substitution in cases of generalized or partial antibody deficiency in immune-compromised patients. These include the following diseases: hypogammaglobulinemia (congenital and acquired, including the neonates); drug-induced and viral immunosuppression. Antibody substitution in cases of selective antibody deficiency in otherwise immune-competent patients. These include acute cases of consumptive antibody deficiencies of the Jarisch-Herxheimer reaction type; in particular, chronic inflammations which apparently involve ineffective immune responses in which the organism is unable to build up sufficient amounts of antibodies with the required partial specificity, which is indispensable for overcoming the disease. Modulation of the immune system by Ig-Ig interactions (mainly idiotype-anti-idiotype interactions) and Ig-Fc-receptor interactions, as it is known from the RES blockade during IVIG treatment of idiopathic thrombocytopenic purpura.

In vitro and in vivo effect of immunoglobulin G on the integrity of bacterial membranes

The interaction between a modified 7S immunoglobulin (MISG) and bacterial membranes was studied by adopting in vitro as well as in vivo techniques. Preincubation of Escherichia coli and Pseudomonas aeruginosa with MISG resulted in a release of enzymatic markers from the periplasmic space, whereas no cytoplasmic or membrane-bound enzymes were liberated. Due to the interaction of MISG with the outer membrane of gram-negative rods, the bacteria became more susceptible to the antibacterial action of poorly penetrating penicillins because of a significantly increased rate of uptake. These in vitro effects were corroborated under in vivo conditions by adopting the granuloma pouch model. A single intravenous injection of MISG enhanced the therapeutic efficacy of mezlocillin against E. coli; similarly, the antibacterial activity of penicillin G, oxacillin, cephalothin and cefamandole against Staphylococcus aureus was augmented by MISG. These in vivo effects of MISG were not due to an increased rate of phagocytosis or complement activity. Thus, MISG sensitized bacteria to several beta-lactam antibiotics by disorganizing their outer membrane.

Experimental Klebsiella septicemia in mice: treatment with specific antibodies from the rabbit alone and in combination with gentamicin

Using a model of an experimental Klebsiella pneumoniae septicemia in mice, we examined the therapeutic effect of passively administered specific antibacterial antibodies from rabbits. Both specific IgM and IgG antibody proved to be therapeutically effective. However, the effect of IgG was markedly superior to that of IgM with regard both to the degree of protection and the time interval allowing efficient therapy after infection. The effect of IgG was due to a marked enhancement of in vivo phagocytosis, as demonstrated by monitoring bacterial numbers in the liver, spleen, lungs and kidneys. In mice immunocompromised with cyclophosphamide, treatment with IgG still exerted protection against low challenge inocula. When higher inocula were used, treatment with IgG ceased to influence the final mortality rates but delayed the course of the disease for several days by transient reduction of bacterial numbers in the parenchymal organs. In both normal and immunocompromised mice, concomitant treatment with gentamicin resulted in a marked synergistic enhancement of survival.

In vitro and in vivo effect of immunoglobulin G on the integrity of bacterial membranes

The interaction between a modified 7S immunoglobulin (MISG) and bacterial membranes was studied by adopting in vitro as well as in vivo techniques. Preincubation of Escherichia coli and Pseudomonas aeruginosa with MISG resulted in a release of enzymatic markers from the periplasmic space, whereas no cytoplasmic or membrane-bound enzymes were liberated. Due to the interaction of MISG with the outer membrane of gram-negative rods, the bacteria became more susceptible to the antibacterial action of poorly penetrating penicillins because of a significantly increased rate of uptake. These in vitro effects were corroborated under in vivo conditions by adopting the granuloma pouch model. A single intravenous injection of MISG enhanced the therapeutic efficacy of mezlocillin against E. coli; similarly, the antibacterial activity of penicillin G, oxacillin, cephalothin and cefamandole against Staphylococcus aureus was augmented by MISG. These in vivo effects of MISG were not due to an increased rate of phagocytosis or complement activity. Thus, MISG sensitized bacteria to several beta-lactam antibiotics by disorganizing their outer membrane.

Antibody levels in reduced/alkylated intravenous immune globulin

Antibody titers, found in representative lots of a reduced and alkylated intravenous immune globulin, against a variety of common microorganisms are presented. With the more frequently occurring pathogens the specific antibody level does not vary significantly between lots. Depending upon the type of assay used, antibody titers per se may or may not reflect the therapeutic activity of the preparation against a specific microorganism.