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This review delves into the multifaceted technologies, benefits and considerations surrounding the expression of animal proteins in plants, emphasizing its potential role in advancing global nutrition, enhancing sustainability, while being mindful of the safety considerations. As the world's population continues to grow and is projected to reach 9 billion people by 2050, there is a growing need for alternative protein sources that can meet nutritional demands while minimizing environmental impact. Plant expression of animal proteins is a cutting-edge biotechnology approach that allows crops to produce proteins traditionally derived from animals, offering a sustainable and resource-efficient manner of producing these proteins that diversifies protein production and increases food security. In the United States, it will be important for there to be clear guidance in order for these technologies to reach consumers. As consumer demand for sustainable and alternative food sources rise, biotechnologies can offer economic opportunities, making this emerging technology a key player in the market landscape., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Tusé, McNulty, McDonald and Buchman.)

The novel wound-healing biologic EPICERTIN, a recombinant analog of cholera toxin B subunit, is in early development for the management of ulcerative colitis. This study established for the first time the pharmacokinetics (PK), bioavailability (BA), and acute safety of EPICERTIN in healthy and dextran sodium sulfate-induced colitic mice and healthy rats. For PK and BA assessments, single administrations of various concentrations of EPICERTIN were given intravenously or intrarectally to healthy and colitic C57BL/6 mice and to healthy Sprague-Dawley rats. After intravenous administration to healthy animals, the drug's plasma half-life ( t 1/2 ) for males and females was 0.26 and 0.3 hours in mice and 19.4 and 14.5 hours in rats, respectively. After intrarectal administration, drug was detected at very low levels in only four samples of mouse plasma, with no correlation to colon epithelial integrity. No drug was detected in rat plasma. A single intrarectal dose of 0.1 µM (0.6 µg/mouse) EPICERTIN significantly facilitated the healing of damaged colonic epithelium as determined by disease activity index and histopathological scoring, whereas 10-fold higher or lower concentrations showed no effect. For acute toxicity evaluation, healthy rats were given a single intrarectal administration of various doses of EPICERTIN with sacrifice on Day 8, recording body weight, morbidity, mortality, clinical pathology, and gross necropsy observations. There were no drug-related effects of toxicological significance. The no observed adverse effect level (intrarectal) in rats was determined to be 5 µM (307 µg/animal, or 5.2 µg drug/cm 2 of colorectal surface area), which is 14 times the anticipated intrarectally delivered clinical dose. SIGNIFICANCE STATEMENT: EPICERTIN is a candidate wound-healing biologic for the management of ulcerative colitis. This study determined for the first time the intravenous and intrarectal pharmacokinetics and bioavailability of the drug in healthy and colitic mice and healthy rats, and its acute safety in a dose-escalation study in rats. An initial therapeutic dose in colitic mice was also established. EPICERTIN delivered intrarectally was minimally absorbed systemically, was well tolerated, and induced epithelial wound healing topically at a low dose., (Copyright © 2022 The Author(s).)

Noroviruses (NoV) are the leading cause of epidemic acute gastroenteritis in humans worldwide. A safe and effective vaccine that prevents NoV infection or minimizes NoV disease burden is needed, especially for children and the elderly who are particularly susceptible to NoV disease. A plant-based expression system (magnICON®) was used to manufacture two different virus-like particle (VLP) immunogens derived from human NoV genogroups I and II, genotype 4 (GI.4 and GII.4), which were subsequently blended 1:1 (w/w) into a bivalent vaccine composition (rNV-2v). Here, we report on the safety and immunogenicity of rNV-2v from one pilot and two GLP-compliant toxicity studies in New Zealand White rabbits administered the vaccine subcutaneously (SC) or intramuscularly (IM). Strong genogroup-specific immune responses were induced by vaccination without adjuvant at various doses (200 to 400 μg VLP/administration) and administration schedules (Days 1 and 7; or Days 1, 15 and 29). The results showed sporadic local irritation at the injection site, which resolved over time, and was non-adverse and consistent with expected reactogenicity. There were no signs of systemic toxicity related to vaccine administration relative to vehicle-treated controls with respect to clinical chemistry, haematology, organ weights, macroscopic examinations, or histopathology. In a 3-administration regimen (n + 1 the clinical regimen), the NOAEL for rNV-2v via the SC or IM route was initially determined to be 200 μg. An improved GI.4 VLP variant mixed 1:1 (w/w) with the wild-type GII.4 VLP was subsequently evaluated via the IM route at a higher dose in the same 3-administration model, and the NOAEL was raised to 300 µg. Serology performed in samples of both toxicity studies showed significant and substantial anti-VLP-specific antibody titers for rNV-2v vaccines administered via the IM or SC route, as well as relevant NoV blocking antibody responses. These results support initiation of clinical development of the plant-made NoV vaccine., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: DT was retained as a consultant by the funding source company to assist in the design and management of toxicity studies, analysis of results and development of the manuscript. MM, KT and VB were engaged by the funding source company to conduct immunological studies. AD, FT, FJ and VK are employees of a wholly owned subsidiary of the funding source company., (Copyright © 2022. Published by Elsevier Ltd.)

There are currently worldwide efforts to reduce sugar intake due to the various adverse health effects linked with the overconsumption of sugars. Artificial sweeteners have been used as an alternative to nutritive sugars in numerous applications; however, their long-term effects on human health remain controversial. This led to a shift in consumer preference towards non-caloric sweeteners from natural sources. Thaumatins are a class of intensely sweet proteins found in arils of the fruits of the West-African plant Thaumatococcus daniellii . Thaumatins' current production method through aqueous extraction from this plant and uncertainty of the harvest from tropical rainforests limits its supply while the demand is increasing. Despite successful recombinant expression of the protein in several organisms, no large-scale bioproduction facilities exist. We present preliminary process design, process simulation, and economic analysis for a large-scale (50 metric tons/year) production of a thaumatin II variant using several different molecular farming platforms.

Several epidemic and pandemic diseases have emerged over the last 20 years with increasing reach and severity. The current COVID-19 pandemic has affected most of the world's population, causing millions of infections, hundreds of thousands of deaths, and economic disruption on a vast scale. The increasing number of casualties underlines an urgent need for the rapid delivery of therapeutics, prophylactics such as vaccines, and diagnostic reagents. Here, we review the potential of molecular farming in plants from a manufacturing perspective, focusing on the speed, capacity, safety, and potential costs of transient expression systems. We highlight current limitations in terms of the regulatory framework, as well as future opportunities to establish plant molecular farming as a global, de-centralized emergency response platform for the rapid production of biopharmaceuticals. The implications of public health emergencies on process design and costs, regulatory approval, and production speed and scale compared to conventional manufacturing platforms based on mammalian cell culture are discussed as a forward-looking strategy for future pandemic responses., (Copyright © 2020 Tusé, Nandi, McDonald and Buyel.)

Continuous reports of foodborne illnesses worldwide and the prevalence of antibiotic-resistant bacteria mandate novel interventions to assure the safety of our food. Treatment of a variety of foods with bacteriophage-derived lysins and bacteriocin-class antimicrobial proteins has been shown to protect against high-risk pathogens at multiple intervention points along the food supply chain. The most significant barrier to the adoption of antimicrobial proteins as a food safety intervention by the food industry is the high production cost using current fermentation-based approaches. Recently, plants have been shown to produce antimicrobial proteins with accumulation as high as 3 g/kg fresh weight and with demonstrated activity against major foodborne pathogens. To investigate potential economic advantages and scalability of this novel platform, we evaluated a highly efficient transgenic plant-based production process. A detailed process simulation model was developed to help identify economic "hot spots" for research and development focus including process operating parameters, unit operations, consumables, and/or raw materials that have the most significant impact on production costs. Our analyses indicate that the unit production cost of antimicrobial proteins in plants at commercial scale for three scenarios is $3.00-6.88/g, which can support a competitive selling price to traditional food safety treatments., (© 2019 The Authors. Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers.)

Recently, several plant-made recombinant proteins received favorable regulatory review as food antibacterials in the United States through the Generally Recognized As Safe (GRAS) regulatory procedure, and applications for others are pending. These food antimicrobials, along with approved biopharmaceuticals and vaccines, represent new classes of products manufactured in green plants as production hosts. We present results of new research and development and summarize regulatory, economic and business aspects of the antibacterial proteins colicins and salmocins as new food processing aids.

Griffithsin is a marine algal lectin that exhibits broad-spectrum antiviral activity by binding oligomannose glycans on viral envelope glycoproteins, including those found in HIV-1, HSV-2, SARS, HCV and other enveloped viruses. An efficient, scalable and cost-effective manufacturing process for Griffithsin is essential for the adoption of this drug in human antiviral prophylaxis and therapy, particularly in cost-sensitive indications such as topical microbicides for HIV-1 prevention. The production of certain classes of recombinant biologics in plants can offer scalability, cost and environmental impact advantages over traditional biomanufacturing platforms. Previously, we showed the technical viability of producing recombinant Griffithsin in plants. In this study, we conducted a technoeconomic analysis (TEA) of plant-produced Griffithsin manufactured at commercial launch volumes for use in HIV microbicides. Data derived from multiple non-sequential manufacturing batches conducted at pilot scale and existing facility designs were used to build a technoeconomic model using SuperPro Designer ® modeling software. With an assumed commercial launch volume of 20 kg Griffithsin/year for 6.7 million doses of Griffithsin microbicide at 3 mg/dose, a transient vector expression yield of 0.52 g Griffithsin/kg leaf biomass, recovery efficiency of 70%, and purity of >99%, we calculated a manufacturing cost for the drug substance of $0.32/dose and estimated a bulk product cost of $0.38/dose assuming a 20% net fee for a contract manufacturing organization (CMO). This is the first report modeling the manufacturing economics of Griffithsin. The process analyzed is readily scalable and subject to efficiency improvements and could provide the needed market volumes of the lectin within an acceptable range of costs, even for cost-constrained products such as microbicides. The manufacturing process was also assessed for environmental, health and safety impact and found to have a highly favorable environmental output index with negligible risks to health and safety. The results of this study help validate the plant-based manufacturing platform and should assist in selecting preferred indications for Griffithsin as a novel drug.

Salmonella enterica causes an estimated 1 million illnesses in the United States each year, resulting in 19,000 hospitalizations and 380 deaths, and is one of the four major global causes of diarrhoeal diseases. No effective treatments are available to the food industry. Much attention has been given to colicins, natural non-antibiotic proteins of the bacteriocin class, to control the related pathogen Escherichia coli. We searched Salmonella genomic databases for colicin analogues and cloned and expressed in plants five such proteins, which we call salmocins. Among those, SalE1a and SalE1b were found to possess broad antimicrobial activity against all 99 major Salmonella pathovars. Each of the two salmocins also showed remarkably high potency (>10 6  AU/µg recombinant protein, or >10 3 higher than colicins) against major pathogenic target strains. Treatment of poultry meat matrices contaminated with seven key pathogenic serovars confirmed salmocin efficacy as a food safety intervention against Salmonella.

Enterohemorrhagic Escherichia coli (EHEC) is one of the leading causes of bacterial enteric infections worldwide, causing ∼100,000 illnesses, 3,000 hospitalizations, and 90 deaths annually in the United States alone. These illnesses have been linked to consumption of contaminated animal products and vegetables. Currently, other than thermal inactivation, there are no effective methods to eliminate pathogenic bacteria in food. Colicins are nonantibiotic antimicrobial proteins, produced by E. coli strains that kill or inhibit the growth of other E. coli strains. Several colicins are highly effective against key EHEC strains. Here we demonstrate very high levels of colicin expression (up to 3 g/kg of fresh biomass) in tobacco and edible plants (spinach and leafy beets) at costs that will allow commercialization. Among the colicins examined, plant-expressed colicin M had the broadest antimicrobial activity against EHEC and complemented the potency of other colicins. A mixture of colicin M and colicin E7 showed very high activity against all major EHEC strains, as defined by the US Department of Agriculture/Food and Drug Administration. Treatments with low (less than 10 mg colicins per L) concentrations reduced the pathogenic bacterial load in broth culture by 2 to over 6 logs depending on the strain. In experiments using meats spiked with E. coli O157:H7, colicins efficiently reduced the population of the pathogen by at least 2 logs. Plant-produced colicins could be effectively used for the broad control of pathogenic E. coli in both plant- and animal-based food products and, in the United States, colicins could be approved using the generally recognized as safe (GRAS) regulatory approval pathway.

We report the first evaluation of plant-made conjugate vaccines for targeted treatment of B-cell follicular lymphoma (FL) in a Phase I safety and immunogenicity clinical study. Each recombinant personalized immunogen consisted of a tumor-derived, plant-produced idiotypic antibody (Ab) hybrid comprising the hypervariable regions of the tumor-associated light and heavy Ab chains, genetically grafted onto a common human IgG1 scaffold. Each immunogen was produced in Nicotiana benthamiana plants using twin magnICON vectors expressing the light and heavy chains of the idiotypic Ab. Each purified Ab was chemically linked to the carrier protein keyhole limpet hemocyanin (KLH) to form a conjugate vaccine. The vaccines were administered to FL patients over a series of ≥6 subcutaneous injections in conjunction with the adjuvant Leukine (GM-CSF). The 27 patients enrolled in the study had previously received non-anti-CD20 cytoreductive therapy followed by ≥4 months of immune recovery prior to first vaccination. Of 11 patients who became evaluable at study conclusion, 82% (9/11) displayed a vaccine-induced, idiotype-specific cellular and/or humoral immune response. No patients showed serious adverse events (SAE) related to vaccination. The fully scalable plant-based manufacturing process yields safe and immunogenic personalized FL vaccines that can be produced within weeks of obtaining patient biopsies.

Plant viral vectors delivered by Agrobacterium are the basis of several manufacturing processes that are currently in use for producing a wide range of proteins for multiple applications, including vaccine antigens, antibodies, protein nanoparticles such as virus-like particles (VLPs), and other protein and protein-RNA scaffolds. Viral vectors delivered by agrobacterial T-DNA transfer (magnifection) have also become important tools in research. In recent years, essential advances have been made both in the development of second-generation vectors designed using the 'deconstructed virus' approach, as well as in the development of upstream manufacturing processes that are robust and fully scalable. The strategy relies on Agrobacterium as a vector to deliver DNA copies of one or more viral RNA/DNA replicons; the bacteria are delivered into leaves by vacuum infiltration, and the viral machinery takes over from the point of T-DNA transfer to the plant cell nucleus, driving massive RNA and protein production and, if required, cell-to-cell spread of the replicons. Among the most often used viral backbones are those of the RNA viruses Tobacco mosaic virus (TMV), Potato virus X (PVX) and Cowpea mosaic virus (CPMV), and the DNA geminivirus Bean yellow dwarf virus. Prototypes of industrial processes that provide for high yield, rapid scale up and fast manufacturing cycles have been designed, and several GMP-compliant and GMP-certified manufacturing facilities are in place. These efforts have been successful as evidenced by the fact that several antibodies and vaccine antigens produced by magnifection are currently in clinical development.

Production of recombinant biologics in plants has received considerable attention as an alternative platform to traditional microbial and animal cell culture. Industrially relevant features of plant systems include proper eukaryotic protein processing, inherent safety due to lack of adventitious agents, more facile scalability, faster production (transient systems), and potentially lower costs. Lower manufacturing cost has been widely claimed as an intuitive feature of the platform by the plant-made biologics community, even though cost information resides within a few private companies and studies accurately documenting such an advantage have been lacking. We present two technoeconomic case studies representing plant-made enzymes for diverse applications: human butyrylcholinesterase produced indoors for use as a medical countermeasure and cellulases produced in the field for the conversion of cellulosic biomass into ethanol as a fuel extender. Production economics were modeled based on results reported with the latest-generation expression technologies on Nicotiana host plants. We evaluated process unit operations and calculated bulk active and per-dose or per-unit costs using SuperPro Designer modeling software. Our analyses indicate that substantial cost advantages over alternative platforms can be achieved with plant systems, but these advantages are molecule/product-specific and depend on the relative cost-efficiencies of alternative sources of the same product.

The purpose of the current study was to determine if saliva contains biomarkers that can be used as diagnostic tools for Sjögren's syndrome (SjS). Twenty seven SjS patients and 27 age-matched healthy controls were recruited for these studies. Unstimulated glandular saliva was collected from the Wharton's duct using a suction device. Two µl of salvia were processed for mass spectrometry analyses on a prOTOF 2000 matrix-assisted laser desorption/ionization orthogonal time of flight (MALDI O-TOF) mass spectrometer. Raw data were analyzed using bioinformatic tools to identify biomarkers. MALDI O-TOF MS analyses of saliva samples were highly reproducible and the mass spectra generated were very rich in peptides and peptide fragments in the 750-7,500 Da range. Data analysis using bioinformatic tools resulted in several classification models being built and several biomarkers identified. One model based on 7 putative biomarkers yielded a sensitivity of 97.5%, specificity of 97.8% and an accuracy of 97.6%. One biomarker was present only in SjS samples and was identified as a proteolytic peptide originating from human basic salivary proline-rich protein 3 precursor. We conclude that salivary biomarkers detected by high-resolution mass spectrometry coupled with powerful bioinformatic tools offer the potential to serve as diagnostic/prognostic tools for SjS.

Guidelines issued by regulatory agencies for the development of plant-made pharmaceutical (PMP) products provide criteria for product manufacturing and characterization, safety determination, containment and mitigation of environmental risks. Features of plant-made products do not always enable an easy fit within the criteria subscribed to by regulators. The unconventional nature of plant-based manufacturing processes and peculiarities of plant biology relative to that of traditional biological production systems have led to special considerations in the regulatory scrutiny of PMP. Presented in this review are case studies of two plant-made autologous (patient-specific) cancer vaccines, the nature of which introduced challenges to conventional and standardized development and preclinical evaluation routes. The rationale presented to FDA by the sponsors of each vaccine to build consensus and obtain variances to existing guidelines is discussed. While development of many plant-made biologics can be accomplished within the existing regulatory framework, the development of specialized products can be defended with rational arguments based on strong science.

Background: Animal and clinical studies with plant-produced single-chain variable fragment lymphoma vaccines have demonstrated specific immunogenicity and safety. However, the expression levels of such fragments were highly variable and required complex engineering of the linkers. Moreover, the downstream processing could not be built around standard methods like protein A affinity capture., Design: We report a novel vaccine manufacturing process, magnifection, devoid of the above-mentioned shortcomings and allowing consistent and efficient expression in plants of whole immunoglobulins (Igs)., Results: Full idiotype (Id)-containing IgG molecules of 20 lymphoma patients and 2 mouse lymphoma models were expressed at levels between 0.5 and 4.8 g/kg of leaf biomass. Protein A affinity capture purification yielded antigens of pharmaceutical purity. Several patient Igs produced in plants showed specific cross-reactivity with sera derived from the same patients immunized with hybridoma-produced Id vaccine. Mice vaccinated with plant- or hybridoma-produced Igs showed comparable protection levels in tumor challenge studies., Conclusions: This manufacturing process is reliable and robust, the manufacturing time from biopsy to vaccine is <12 weeks and the expression and purification of antigens require only 2 weeks. The process is also broadly applicable for manufacturing monoclonal antibodies in plants, providing 50- to 1000-fold higher yields than alternative plant expression methods.

Plant-made vaccines have been the subject of intense interest because they can be produced economically in large scale without the use of animal-derived components. Plant-made therapeutic vaccines against challenging chronic diseases, such as cancer, have received little research attention, and no previous human clinical trials have been conducted in this vaccine category. We document the feasibility of using a plant viral expression system to produce personalized (patient-specific) recombinant idiotype vaccines against follicular B cell lymphoma and the results of administering these vaccines to lymphoma patients in a phase I safety and immunogenicity clinical trial. The system allowed rapid production and recovery of idiotypic single-chain antibodies (scFv) derived from each patient's tumor and immunization of patients with their own individual therapeutic antigen. Both low and high doses of vaccines, administered alone or co-administered with the adjuvant GM-CSF, were well tolerated with no serious adverse events. A majority (>70%) of the patients developed cellular or humoral immune responses, and 47% of the patients developed antigen-specific responses. Because 15 of 16 vaccines were glycosylated in plants, this study also shows that variation in patterns of antigen glycosylation do not impair the immunogenicity or affect the safety of the vaccines. Collectively, these findings support the conclusion that plant-produced idiotype vaccines are feasible to produce, safe to administer, and a viable option for idiotype-specific immune therapy in follicular lymphoma patients.

We have developed a method for rapidly producing in plants the idiotype regions of the tumor-specific Ig as single-chain Fv (scFv) proteins for use in the treatment of non-Hodgkin's lymphoma. Variable region gene sequences were generated from either a tumor hybridoma or human tumor biopsy cells, and idiotype domains were joined by a novel linker and cloned into a modified tobacco mosaic virus (TMV) vector designed to secrete the scFv protein in infected Nicotiana benthamiana plants. Thirty-eight out of 44 human scFv proteins showed Coomassie visible material in crude secretory (interstitial fluid, IF) extracts, 21 of those between 100 and 800 microg/ml. Eight of these proteins were tested for appropriate idiotype responses in vaccinated mice. In all eight cases, anti-idiotype immune responses were induced with minimal cross reactivity to irrelevant Ig or scFv proteins. Four out of four anti-scFv sera were also shown to recognize the Ig on human tumor cells by flow cytometry analysis.

An overproduction of proinflammatory cytokines mediates the damaging sequelae of inflammation in pathologic conditions such as rheumatoid arthritis, graft-vs-host reaction, cachexia, and sepsis syndrome. We examined the cytokine regulatory activity of synthetic melanin, exemplified by biosynthetic l-glycine-l-tyrosine-based polymer (ME-1) and chemosynthetic dihydroxyphenylalanine-based polymer (MC-1). At nontoxic concentrations, both compounds effectively (>/=60%) and reversibly suppressed the production of tumor necrosis factor (TNF), even when applied after stimulation of human peripheral blood monocytes with lipopolysaccharide (LPS). The inhibitory activity of melanin was selective with regard to cytokine response but not inducer- or cell-type-specific. In addition to TNF, melanin inhibited production of interleukin (IL)-1beta, IL-6, and IL-10 but not granulocyte-macrophage colony-stimulating factor by the LPS-stimulated monocytes. Melanin was equally effective in inhibiting production of TNF by monocytes stimulated with the purified protein derivative of Mycobacterium tuberculosis and production of IL-6 by IL-1alpha-stimulated human fibroblasts and endothelial cells. Northern blot analysis, mRNA stability determination, immunoprecipitation studies on metabolically labeled intracellular TNF, and pulse chase experiments revealed that melanin reduced efficiency of mRNA translation. The finding that melanin arrests ongoing cytokine synthesis suggests that this compound may be useful as an adjunct therapy for conditions showing involvement of proinflammatory cytokines., (Copyright 2000 Academic Press.)

Rapid production of protein-based tumor-specific vaccines for the treatment of malignancies is possible with the plant-based transient expression system described here. We created a modified tobamoviral vector that encodes the idiotype-specific single-chain Fv fragment (scFv) of the immunoglobulin from the 38C13 mouse B cell lymphoma. Infected Nicotiana benthamiana plants contain high levels of secreted scFv protein in the extracellular compartment. This material reacts with an anti-idiotype antibody by Western blotting, ELISA, and affinity chromatography, suggesting that the plant-produced 38C13 scFv protein is properly folded in solution. Mice vaccinated with the affinity-purified 38C13 scFv generate >10 micrograms/ml anti-idiotype immunoglobulins. These mice were protected from challenge by a lethal dose of the syngeneic 38C13 tumor, similar to mice immunized with the native 38C13 IgM-keyhole limpet hemocyanin conjugate vaccine. This rapid production system for generating tumor-specific protein vaccines may provide a viable strategy for the treatment of non-Hodgkin's lymphoma.

We identified a structural analog of thyroid hormone, methyl-3,5-diiodo-4-(4'-methoxyphenoxy) benzoate (Oncocidin A1), that inhibits human carcinoma cell proliferation and the growth of human breast (MDA MB-231) and ovarian (OVCAR-3) carcinoma xenografts in nude mice. This novel antitumor agent is orally bioavailable and well tolerated by animals. Exposure of MCF-7 and MDA MB-231 breast carcinoma cells to Oncocidin A1 in vitro caused a cell-cycle arrest in prometaphase (a G2/M arrest) and apoptosis, suggesting a cytotoxic mechanism involving mitotic spindle function. The interaction of Oncocidin A1 with microtubules was demonstrated by: 1) immunofluorescence studies of microtubule assembly in the presence of the drug in cell-free and in cellular assays; and 2) in vitro binding inhibition studies involving radiolabeled Oncocidin A1 or colchicine and tubulin monomers. Taken together, these experiments indicate that Oncocidin A1 perturbs cellular microtubule assembly, possibly by binding to the colchicine site on tubulin. Three-dimensional structural modelling of Oncocidin A1 revealed that it can adopt a twisted conformation similar to that of combretastatin A-4, which binds to the colchicine site of tubulin. The novel structural features of Oncocidin A1 could guide the design of a new class of microtubule-binding antitumor agents having substantially reduced normal tissue toxicity upon oral administration.

Murine peritoneal macrophages insonated in vitro at 37 degrees C were assayed for impairment of adhesion to and spreading on glass coverslips, expressions of Fc gamma and C3b receptors, and phagocytosis. Insonation conditions were typical for exposures by B-mode imaging equipment and approximated the most severe exposures anticipated in use of pulsed Doppler equipment. In no case were the assay results for insonated samples significantly different from those for the sham-exposed controls.

Murine peritoneal exudate cells (PEC), predominantly macrophages, were insonated in vitro with burst-mode ultrasound and assayed for their ability to phagocytose and kill Staphylococcus aureus. PEC were exposed at 37 degrees C in rotating tubes to 1-MHz, burst-mode (10 ms on, 10 ms off) ultrasound at 3.7 +/- 0.2 W/cm2 ISPTA (7.4 +/- 0.4 W/cm2 ISPBA) for 150 s. Bactericidal activity was assayed at 1, 2, and 3 h after exposure and subsequent 37 degrees C incubation with the bacteria for 20 min. In these experiments, which comprised 17 treated and 7 sham-treated control samples, there was no significant difference in results between treated and control samples (p > 0.29).

Batch and continuous fermentations with Clostridium thermoaceticum (ATCC 39073) using automatic pH control were conducted. The value of mu(max) obtained from batch fermentation was about 0.14 h(-1); acetate yield, which was both growth and non-growth associated, was about 2 mole of acetic acid/mole of glucose, compared with a theoretical maximum value of 3. This low yield, compared with literature data, may be explained by glucose loss through a combination of degradation routes. Continuous fermentation could be sustained for 1600 h or more without contamination problems. Continuous fermentation at high dilution rates indicates that mu(max) may be well above 0.17 h(-1) when fresh feed medium is used. Acetate yields in continuous fermentation were about 77% of theoretical or 2.3 mole of acetic acid/mole of glucose.

The consumption of microorganisms by man and animals is not a revolutionary new idea. For thousands of years man has consumed, either intentionally or unintentionally, such products as alcoholic beverages, cheeses, yogurt, and soya sauce and, along with these products, the microbial biomass responsible for their production. The rapid growth rate and high protein content of microbes and their ability to utilize inexpensive feedstocks as sources of carbon and energy for growth have made microorganisms prime candidates for use as human food and animal feed protein supplements. Yet, in spite of their promise, only a limited number of commercial-scale, single-cell protein (SCP) processes have been seen. Recently, with the advent of recombinant DNA technology a rebirth of interest in SCP has resulted. This review analyzes the answers to two questions: (1) how far have we come?; and (2) what impact, if any, will the new biotechnologies have in this field?