A prospective, randomized assessment of a novel, local antibiotic releasing platform for the prevention of superficial and deep surgical site infections

BACKGROUND

Despite significant advances in infection control guidelines and practices, surgical site infections (SSIs) remain a substantial cause of morbidity, prolonged hospitalization, and mortality among patients having both elective and emergent surgeries. D-PLEX₁₀₀ is a novel, antibiotic-eluting polymer-lipid matrix that supplies a high, local concentration of doxycycline for the prevention of superficial and deep SSIs. The aim of our study was to evaluate the safety and efficacy of D-PLEX in addition to standard of care (SOC) in preventing superficial and deep surgical site infections for patients undergoing elective colorectal surgery.

METHODS

From October 10, 2018 to October 6, 2019, as part of a Phase 2 clinical trial, we randomly assigned 202 patients who had scheduled elective colorectal surgery to receive either standard of care SSI prophylaxis or D-PLEX₁₀₀ in addition to standard of care. The primary objective was to assess the efficacy of D-PLEX₁₀₀ in superficial and deep SSI reduction, as measured by the incidence of SSIs within 30 days, as adjudicated by both an individual assessor and a three-person endpoint adjudication committee, all of whom were blinded to study-group assignments. Safety was assessed by the stratification and incidence of treatment-emergent adverse events.

RESULTS

One hundred and seventy-nine patients were evaluated in the per protocol population, 88 in the intervention arm [51 males, 37 females, median age (64.0 range: 19-92) years] and 91 in the control arm [57 males, 34 females, median age 64.5 (range: 21-88) years]. The SSI rate within 30 day post-index surgery revealed a 64% relative risk reduction in SSI rate in the D-PLEX₁₀₀ plus standard of care (SOC) group [n = 7/88 (8%)] vs SOC alone [n = 20/91 (22%)]; p = 0.0115. There was no significant difference in treatment-emergent adverse events.

CONCLUSIONS

D-PLEX₁₀₀ application leads to a statistically significant reduction in superficial and deep surgical site infections in this colorectal clinical model without any associated increase in adverse events.

Whole Cell Panning with Phage Display

Phage display has emerged as one of the leading technologies for the selection of highly specific monoclonal antibodies, offering a number of advantages over traditional methods of antibody generation. While there are various possibilities to conduct phage display (e.g., solution panning, solid-phase panning), whole cell panning is an elegant way to present membrane embedded target antigens in their natural environment and conformation to antibody-bearing phages. Here, a whole cell panning procedure using a Fab-based antibody library including primary cell based screening for selectivity is described.

Comparative laboratory evolution of ordered and disordered enzymes

Intrinsically disordered proteins are ubiquitous in nature. To assess potential evolutionary advantages and disadvantages of structural disorder under controlled laboratory conditions, we directly compared the evolvability of weakly active ordered and disordered variants of dihydrofolate reductase by genetic selection. The circularly permuted Escherichia coli enzyme, which exists as a molten globule in the absence of ligands, and a well folded deletion mutant of the Bacillus stearothermophilus enzyme served as starting points. Both scaffolds evolved at similar rates and to similar extents, reaching near-native activity after three rounds of mutagenesis and selection. Surprisingly, however, the starting structural properties of the two scaffolds changed only marginally during optimization. Although the ordered and disordered proteins accumulated distinct sets of mutations, the changes introduced likely improved catalytic efficiency indirectly in both cases by bolstering the network of dynamic conformational fluctuations that productively couple into the reaction coordinate.

A fully synthetic human Fab antibody library based on fixed VH/VL framework pairings with favorable biophysical properties

This report describes the design, generation and testing of Ylanthia, a fully synthetic human Fab antibody library with 1.3E+11 clones. Ylanthia comprises 36 fixed immunoglobulin (Ig) variable heavy (VH)/variable light (VL) chain pairs, which cover a broad range of canonical complementarity-determining region (CDR) structures. The variable Ig heavy and Ig light (VH/VL) chain pairs were selected for biophysical characteristics favorable to manufacturing and development. The selection process included multiple parameters, e.g., assessment of protein expression yield, thermal stability and aggregation propensity in fragment antigen binding (Fab) and IgG1 formats, and relative Fab display rate on phage. The framework regions are fixed and the diversified CDRs were designed based on a systematic analysis of a large set of rearranged human antibody sequences. Care was taken to minimize the occurrence of potential posttranslational modification sites within the CDRs. Phage selection was performed against various antigens and unique antibodies with excellent biophysical properties were isolated. Our results confirm that quality can be built into an antibody library by prudent selection of unmodified, fully human VH/VL pairs as scaffolds.

HuCAL PLATINUM, a synthetic Fab library optimized for sequence diversity and superior performance in mammalian expression systems

This article describes the design of HuCAL (human combinatorial antibody library) PLATINUM, an optimized, second-generation, synthetic human Fab antibody library with six trinucleotide-randomized complementarity-determining regions (CDRs). Major improvements regarding the optimized antibody library sequence space were implemented. Sequence space optimization is considered a multistep process that includes the analysis of unproductive antibody sequences in order to, for example, avoid motifs such as potential N-glycosylation sites, which are undesirable in antibody production. Gene optimization has been used to improve expression of the antibody master genes in the library context. As a result, full-length IgGs derived from the library show both significant improvements in expression levels and less undesirable glycosylation sites when compared to the previous HuCAL GOLD library. Additionally, in-depth analysis of sequences from public databases revealed that diversity of CDR-H3 is a function of loop length. Based upon this analysis, the relatively uniform diversification strategy used in the CDR-H3s of the previous HuCAL libraries was changed to a length-dependent design, which replicates the natural amino acid distribution of CDR-H3 in the human repertoire. In a side-by-side comparison of HuCAL GOLD and HuCAL PLATINUM, the new library concept led to isolation of about fourfold more unique sequences and to a higher number of high-affinity antibodies. In the majority of HuCAL PLATINUM projects, 100-300 antibodies each having different CDR-H3s are obtained against each antigen. This increased diversity pool has been shown to significantly benefit functional antibody profiling and screening for superior biophysical properties.

Fiber scaffolds of polysialic acid via electrospinning for peripheral nerve regeneration

Fiber scaffolds of bioactive polysialic acid have been prepared via electrospinning for peripheral nerve regeneration. The diameter, morphology and alignment of fibers in scaffolds were adjusted by variation of electrospinning parameters, which are decisive for the cell-scaffold interaction. Due to the high water solubility of polysialic acid (poly-alpha-2,8-N-acetylneuraminic acid) a photoactive derivative (poly-alpha-2,8-N-pentenoylneuraminic acid) was used to obtain stable fiber scaffolds in water by photochemical crosslinking. At the optimized fiber scaffolds good cell viability and directed cell proliferation along the fibers was achieved by cell tests with immortalized Schwann cells.

Polysialic acid immobilized on silanized glass surfaces: a test case for its use as a biomaterial for nerve regeneration

The immobilization of polysialic acid (polySia) on glass substrates has been investigated with regard to the applicability of this polysaccharide as a novel, biocompatible and bioresorbable material for tissue engineering, especially with regard to its use in nerve regeneration. PolySia, a homopolymer of alpha-2,8-linked sialic acid, is involved in post-translational modification of the neural cell adhesion molecule (NCAM). The degradation of polySia can be controlled which makes it an interesting material for coating and for scaffold construction in tissue engineering. Here, we describe the immobilization of polySia on glass surfaces via an epoxysilane linker. Whereas glass surfaces will not actually be used in nerve regeneration scaffolds, they provide a simple and efficient means for testing various methods for the investigation of immobilized polySia. The modified surfaces were investigated with contact angle measurements and the quantity of immobilized polySia was examined by the thiobarbituric acid assay and a specific polySia-ELISA. The interactions between the polySia-modified surface and immortalized Schwann cells were evaluated via cell adhesion and cell viability assays. The results show that polySia can be immobilized on glass surfaces via the epoxysilane linker and that surface-bound polySia has no toxic effects on Schwann cells. Therefore, as a key substance in the development of vertebrates and as a favourable substrate for the cultivation of Schwann cells, it offers interesting features for the use in nerve guidance tubes for treatment of peripheral nerve injuries.

Synthesis and biological evaluation of a polysialic acid-based hydrogel as enzymatically degradable scaffold material for tissue engineering

Restorative medicine has a constant need for improved scaffold materials. Degradable biopolymers often suffer from uncontrolled chemical or enzymatic hydrolysis by the host. The need for a second surgery on the other hand is a major drawback for nondegradable scaffold materials. In this paper we report the design and synthesis of a novel polysialic acid-based hydrogel with promising properties. Hydrogel synthesis was optimized and enzymatic degradation was studied using a phage-born endosialidase. After addition of endosialidase, hydrogels readily degraded depending on the amount of initially used cross-linker within 2 to 11 days. This polysialic acid hydrogel is not cytotoxic, completely stable under physiological conditions, and could be evaluated as growth support for PC12 cells. Here, additional coating with collagen I, poly-L-lysine or matrigel is mandatory to improve the properties of the material.

A study on polysialic acid as a biomaterial for cell culture applications

Polysialic acid (PSA) was investigated for its applicability as coating material for mammalian cell cultivation. PSA is involved in post-translational modification of the vertebrate neural cell adhesion molecule (NCAM). It is biocompatible and degradation-controlled. Thus, it becomes interesting for use as a coating and scaffold material for tissue engineering applications, especially for peripheral nerve regeneration. As a preliminary study of the use of PSA as scaffold material it was tested in its soluble form as coating material. The cytotoxicity was investigated and compared to another polysaccharide beta-glucan, to widely used coating substances (collagen I, poly-L-lysine, hyaluronic acid) and uncoated tissue culture plastic material. The interactions between the modified cell culture surface and the cells were investigated using a model liver cell line Hep-G2 and a neurobiological cell line PC-12. The PSA coating itself was analyzed by immunoanalysis. Viability of the cells was investigated by the MTT assay. The number and distribution of adhered cells were studied by cell nuclei staining. Furthermore, the differentiation status of the PC-12 cells was monitored, as well as glucose and lactate levels in the cell culture medium from the Hep-G2 cells. Comparable viability and similar numbers of attached cells were observed. Growth in cell clusters was observed for PSA, beta-glucan, and hyaluronic acid coated materials. In general, the results indicate that PSA is comparable to other well-established coating materials (e.g. collagen I, hyaluronic acid, and poly-L-lysine). Moreover, as a key substance in vertebrate development it offers interesting features for nerve regeneration, especially as an insoluble, modified scaffold material.

Collagen biomaterial doped with colominic acid for cell culture applications with regard to peripheral nerve repair

Colominic acid (CA) is a homopolymer of sialic acid residues and is solely composed of polymerised units of alpha-2,8-linked N-acetylneuraminic acid. CA is a specific derivative of polysialic acid (PSA), produced as the capsular polysaccharide of Escherichia coli K1 derived molecule of PSA. PSA in vivo plays a significant role in synaptic plasticity and neural development. The use of collagen materials doped with defined CA is presented for the cultivation of various cell lines relevant for possible applications in Tissue Engineering. First, the release behaviour under culture conditions of the collagen-based (C-CA) materials was investigated by thiobarbituric acid assay. Additionally, the established cell lines, PC-12 and immortalised Schwann cells (ISC), used for neurobiological and neurochemical studies and the model liver cell line Hep-G2 as indicator for biocompatibility testing, were cultured on the C-CA matrix. Cell proliferation (MTT-test) and cell adhesion (DAPI-staining) of the cell lines on the matrices were observed. Likewise, gene expression of the marker genes thyrosine hydroxylase for the PC-12 cells, and albumin, transferrin and CYP3A4 for the Hep-G2 cells was evaluated via RT-PCR. The results indicate that CA integration in established biomaterial constructs enhances cell proliferation and offers promising features as conduits additive in regarding peripheral nerve regeneration.

Fast and efficient screening system for new biomaterials in tissue engineering: a model for peripheral nerve regeneration

The use of three-dimensional biodegradable matrices is one major issue in tissue engineering. Numerous materials, fabrication techniques, and modifications have been used and tested in different areas of tissue engineering recently. But nevertheless, technology is far from being optimized and optimal constructs with bioidentical and mechanical properties have not been described in the literature so far. Hence, there is great demand of new suitable biomaterials for tissue engineering applications. In this study, a fast and efficient screening system for initial testing of biomaterials for cell culture application was developed. The set up for the screening system and the decision criteria applied for the determination of suitability of new materials are presented. Hep-G2 and PC-12 cells were seeded onto different matrices and cultured over a period of 2 weeks. The viability of the cells was monitored via the MTT assay. Cell spreading was investigated by DAPI-staining of cell nuclei. Furthermore, the adhesion of the cells on the different matrices was examined by counting the number of attached cells. With these general assays a classification of materials is possible with regard to their suitability. Optimal cell models must be chosen for the defined applications and at least two cell lines are necessary for a differentiating interpretation.

Crystallization and molecular-replacement solution of a diagnostic fluorescent dye in complex with a specific Fab fragment

Tetrasulfocyanine (TSC) has been described as a fluorescent probe for tumour imaging. The complex of TSC and the Fab antibody fragment MOR03268 has been crystallized in three different crystal forms. MOR03268 was identified from the HuCAL GOLD library and further optimized to bind TSC with high affinity (Kd = 0.6 nM). For two of the three crystal forms (forms 1 and 2), data sets could be collected to 2.8 and 2.85 A resolution, respectively. Form 1 belongs to space group I222, with unit-cell parameters a = 72, b = 99, c = 154 A. Form 2 belongs to space group P4(3)2(1)2, with unit-cell parameters a = b = 77, c = 379 A. Form 3 only diffracted to 8 A and was not analyzed further. Molecular-replacement solutions for forms 1 and 2 were found and rebuilding and refinement is in progress. Form 1 contains one Fab molecule per asymmetric unit, while form 2 harbours two. Judging from the green colour of the crystals, both forms contain the Fab molecule bound to the green TSC dye and in both the hydrolysis-sensitive dye molecule is protected from degradation for several weeks to months. The structures should reveal the molecular basis of the high-affinity recognition of TSC by the Fab molecule MOR03268.

Application of collagen matrices for cartilage tissue engineering

Articular cartilage shows little capacity for self-repair once it has been damaged. The aim of this study was to investigate different collagen matrices regarding their applicability for cartilage tissue engineering. The matrices consist of collagen I and small amounts of elastine, were crosslinked with carbodiimide or glucose. Primary chondrocytes were seeded onto these different collagen matrices and cultured with or without differentiation medium. The viability of the cells was monitored via MTT test. The arrangement of the cells onto the scaffold was investigated by histological staining. Furthermore, extracellular matrix synthesis was studied by immunohistological staining, especially the expression of the typical chondrogenic marker collagen II. Moreover gene expression for collagen type II was analysed by RT-PCR. The chondrocytes showed high viability on all matrices used. The results for the histological staining revealed a three-dimensional arrangement of the chondrocytes in the collagen matrices. Moreover, the matrices also supported chondrogenic differentiation. On the matrix MATRIDERM 2 mm the synthesis of collagen II was stimulated without adding any differentiation supplements to the cell culture medium, as observed by immunohistological staining and by gene expression analysis of collagen II.

Size and composition of T-cell receptor delta (TCRD) junctional sequences are not predictive of the sensitivity of clonospecific oligonucleotides designed for detection of minimal residual disease in acute lymphoblastic leukemia

We characterized 168 junctional regions of T-cell receptor delta (TCRD) rearrangements from 116 children with acute lymphoblastic leukemia (ALL) (101 with precursor B-cell ALL, 15 with T-cell ALL). Application of 101 allele-specific oligonucleotide (ASO) probes representing 85 Vdelta2Ddelta3, 10 Ddelta2Ddelta3, 3 Vdelta1Jdelta1, 1 Vdelta3Jdelta1, and 2 Ddelta2Jdelta1 junctions for the detection of minimal residual disease (MRD) revealed detection levels of 10(-4) to 10(-6) leukemia cells in the vast majority of cases (93 of 101). Of interest was that neither the N, D, P (nontemplated, diversity, palindromic) content and length of the junctional regions nor the number of nucleotides deleted from the flanking V, D, or J (variable, diversity, joining) elements correlated with the sensitivity of ASO probes. These data indicated that in ALL TCRD rearrangements can serve as suitable tools for the detection of MRD irrespective of the specific composition of the junctional region.

Immunoglobulin kappa gene rearrangements between the kappa deleting element and Jkappa recombination signal sequences in acute lymphoblastic leukemia and normal hematopoiesis

The kappa deleting element (kappaDE) located 24 kb downstream of the Ckappa gene segment mediates the deletion of Ckappa and the Jkappa-Ckappa Intron enhancer, which results in allelic exclusion of the immunoglobulin kappa light chain locus. We here report that the kappaDE can recombine to each recombination signal sequence (RSS) flankappaing Jkappa1 to Jkappa5 in normal hematopoiesis. Moreover, usage of the JkappaRSS-kappaDE junctional sequence allows the detection of minimal residual disease in acute lymphoblastic leukemia.

T cell receptor Ddelta2Ddelta3 rearrangement: a suitable allele-specific marker for the detection of minimal residual disease in childhood acute lymphoblastic leukemia

The applicability of T cell receptor (TCR) Ddelta2Ddelta3 junctional regions for the detection of minimal residual disease (MRD) was examined in childhood acute lymphoblastic leukemia (ALL). Southern blot analysis showed a Ddelta2Ddelta3 rearrangement in 22 of 172 (13%) precursor-B ALL. No Ddelta2Ddelta3 rearrangement was identified in 29 T-ALL cases. Three patients exhibited Ddelta2Ddelta3 recombinations in both alleles. Sequence analysis of Ddelta2Ddelta3 junctions revealed extensive diversity due to the random insertion and deletion of nucleotides at the joining site. PCR analysis utilizing allele-specific probes or oligonucleotides generated on the basis of Ddelta2Ddelta3 junctional sequences reached a sufficient sensitivity of 10(-4) to 10(-5) in the majority of cases. In four of 25 (16%) rearranged alleles, however, the 5' heptamer-nonamer recombination signal sequence (RSS) of the Ddelta2 segment had recombined directly to the 3' heptamer-nonamer RSS of the Ddelta3 segment thus generating a so-called signal junction. Respective heptamer-heptamer junctions are not suited to design allele-specific oligonucleotides for the detection of MRD because of their limited diversity and hence specificity.

Insufficient stocking of poisoning antidotes in hospital pharmacies

OBJECTIVE

To determine whether antidotes for poisoning and overdose are available in hospitals that provide emergency department care.

DESIGN

Written survey of hospital pharmacy directors, each of whom reported the amount currently in stock of 8 different antidotes: antivenin (Crotalidae) polyvalent, cyanide kit, deferoxamine mesylate, digoxin immune Fab, ethanol, naloxone hydrochloride, pralidoxime chloride, and pyridoxine hydrochloride.

PARTICIPANTS

Pharmacy directors of all hospitals with emergency departments in Colorado, Montana, and Nevada.

MAIN OUTCOME MEASURES

Proportions of hospitals with insufficient stocking of each antidote, defined as complete lack of the antidote or an amount inadequate to initiate treatment of 1 seriously poisoned 70-kg patient.

RESULTS

Questionnaires were mailed to 137 hospital pharmacy directors and 108 (79%) responded. Only 1 (0.9%) of the 108 hospitals stocked all 8 antidotes in adequate amounts. The rate of insufficient stocking for individual antidotes ranged from 2% (for naloxone) to 98% (for digoxin immune Fab). In a multiple regression analysis, smaller hospital size and lack of a formal review of antidote stocking were independent predictors of the number of antidotes stocked insufficiently.

CONCLUSIONS

Insufficient stocking of antidotes is a widespread problem in Colorado, Montana, and Nevada. Although these states are served by a certified regional poison center, potentially lifesaving antidotes are frequently not available when and where they might be needed to treat a single poisoned patient.

Management of alimentary tract duplication in children

Duplication of the alimentary tract is rare but potentially dangerous. Five of 72 children with alimentary tract duplication treated between 1973 and 1992 died from postoperative complications; a further ten required more than one operation. Ileal duplications were the commonest, occurring in 16 patients (22 per cent). Thoracoabdominal duplications were the most complicated and responsible for much of the overall morbidity and mortality. Surgical complications were related to the size and location of the duplication, communication with the gastrointestinal tract or vertebral canal, presence of heterotopic gastric mucosa and involvement of mesenteric vessels. Complete excision of the duplication should be possible in most cases.

Slow cytotoxicity of the polysaccharide levan on tumor cells in vitro

Previous studies have shown that 1 h preincubation with levan caused a sharp decrease in tumorigenicity of tumor cells, although cell viability was not affected. In the present study, the possibility that levan might change the sensitivity of Lewis lung carcinoma cells to the host immune system and that levan might cause delayed damage were tested. Cell morphology, DNA synthesis, cell multiplication and viability as well as osmotic fragility were followed during several days in culture. Levan was found not to affect cell immunogenicity. The polysaccharide destroyed tumor cells by a rather peculiar mechanism: after a seemingly normal or even enhanced growth in culture during 3-5 days, cells suddenly burst. During the apparently normal growth, several morphological changes were observed: cell volume increased, cytoplasm swelled by apparent water uptake and some cells contained two or more nuclei. Levan-treated cells were found to be more susceptible to osmotic shock than non-treated cells. The reason for the sudden cell death could be a gradual increase in volume, up to a point which is no more compatible with membrane integrity, resulting in cell lysis.

Different effects of the polysaccharide levan on the oncogenicity of cells of two variants of Lewis lung carcinoma

A marked difference in sensitivity to the direct effect of the polysaccharide levan on tumour cells was observed between two variants of malignancy of Lewis lung carcinoma: cells of the more malignant variant (3LL-M) were much more sensitive to the drug than those of the less malignant tumour (3LL). A gradual decrease in tumorigenicity following preincubation with increasing levan concentrations was observed with both variants, but statistically significant inhibition was observed at lower levan concentrations with 3LL-M than with 3LL.

Different biological behavior of AKR lymphoma cells from primary and metastatic tumors

AKR lymphoma cells derived from primary s.c. tumors (PT) and cells from their metastases (MT) were inoculated into recipient mice in order to compare their malignant behavior. A higher malignant potential of MT compared to PT cells was found. The results support the hypothesis that metastasis is a process of selection of cells possessing a potential to metastasize, which preexist in the primary tumor. In the model used, both the selection of 'variants' of malignancy and the assay of malignancy were as close as possible to natural tumor progression.

Different stages of tumor development are unequally affected by pretreatment of tumor cells with a polysaccharide

Pretreatment with the polysaccharide levan of Lewis lung carcinoma and AKR lymphoma cells affected unequally different stages of tumor development. While levan pretreatment sharply reduced the evolution of tumors from subcutaneously inoculated cells, no such inhibition was observed with pretreated cells inoculated intravenously. Since levan is known to affect the cell membrane, it is concluded that different cell membrane properties may be involved in the various stages of tumor progression.

Direct antitumor effect of the polysaccharide levan in mice: effects of drug concentration and time and temperature of incubation

In vitro treatment of Lewis lung carcinoma cells with the polysaccharide levan was shown previously to reduce the oncogenicity of these cells by acting on the cell membrane. In the present study the direct effect of levan on the tumorigenicity of Lewis lung carcinoma in C57BL male mice was tested at different doses and intervals and temperatures of incubation. A dose-dependent decrease in tumorigenicity was observed: Doses of 0.5, 1, and 2 mg levan/2 X 10(5) cells/0.2 ml reduced tumor incidence by 30, 50, and 70%, respectively. Some degree of inhibition was observed even with a dose of 0.004 mg. The inhibitory effect was rapid; 5 minutes of incubation resulted in the same reduction in oncogenicity as 60 minutes. Inhibition at 0 degree C was as effective as inhibition at 37 degrees C. The lack of temperature effect indicates that enzymatic activity probably is not involved. The data presented here, together with previous data, suggest that levan induces a physical, rather than a chemical, change in the affected tumor cells. The polysaccharide appears to be loosely, noncovalently bound to the cell membrane.

Change from inhibition to stimulation by levan of AKR lymphoma following serial transfers

A progressive increase in malignancy following serial passages of AKR lymphoma is often accompanied by loss in sensitivity to the antitumor agent, levan. In further transfers, stimulation of tumor growth, instead of inhibition, is sometimes observed. It is proposed that the shift from inhibition to stimulation of tumor growth by the immunomodulator levan may be due to a change during tumor progression in the sensitivity of the tumor cells to the reported dual effect of macrophages, inhibitory or stimulatory, on tumor growth.

Combined effect of levan and cytotoxic agents on the growth of experimental tumours in mice

The combined effect of the polysaccharide levan (previously shown to exert a host-dependent as well as direct antitumoural activity) and the cytotoxic agents cyclophosphamide (CY), methotrexate (MTX), vincristine (VINC) and 5-fluoro-uracil (SFU) was studied in Lewis lung carcinoma and AKR lymphoma. Combined chemo- and immunotherapy was applied beginning on the day of tumour cell inoculation. Additive effects were obtained with the combined treatments, compared to single treatments, with all the combinations except MTX-levan in Lewis lung carcinoma, where the combined effect was synergistic. The additive effect was obtained with different doses and routes of chemotherapy, whether local or intraperitoneal. A 2 mg dose of CY combined with levan administered at daily doses of 10 mg, resulted in a 100% prevention of Lewis lung carcinoma growth. It is suggested that the levan may have two beneficial effects: it can exert an inhibitory effect on tumour growth and diminish the deleterious effect of cytotoxic agents on the immune system.

Effect of administration schedule on the levan-cyclophosphamide combined treatment of Lewis lung carcinoma

Combined treatment with levan and cyclophosphamide (CY) was applied intratumorally to Lewis lung carcinoma tumors in C57B1 mice on day 5 after tumor cell inoculation. Although on that day levan alone had no effect and CY alone caused only temporary regression of tumors, the combined CY-levan treatment caused 60% cure. Levan given before CY was almost as effective as simultaneous administration of both drugs on day 5. Delaying the administration of levan after CY treatment reduced the therapeutic effect. It is concluded that timing in relation to tumor cell inoculation as well as the order of administration of drugs, determine the degree of therapeutic efficacy. In tumor chemo-immunotherapy the final effect is probably due not only to the anti-tumoral effect per se of each drug, but also to the fact that the two agents have an effect on the immune system. Since the immune response may change during tumor development, the effect of timing of administration of an immunomodulator and certainly to two immunomodulators, can be crucial.

Mechanism of the inhibitory effect of levan on experimental tumors

The mechanism of the antitumoral effect of levan was studied in the C57BL mice-Lewis lung carcinoma system. Modulation of host immune response and a direct inhibitory effect on tumor cells were found. Local treatment was more effective when begun early. It reduced tumor incidence without affecting the size of developing tumors. Systemic treatment was more effective when started late, inhibiting equally the tumor size in all mice. Macrophages are involved in local, lymphocytes possibly in systemic, inhibition. A direct effect on tumor cells was suggested by a decrease in oncogenicity, following preincubation with levan. Levan augments the antitumoral effect of cyclophosphamide in vivo and in vitro.