Improving the large scale purification of the HIV microbicide, griffithsin

Expression and antiviral application of exogenous lectin (griffithsin) in sweetpotatoes

Griffithsin (GRFT) is a highly effective, broad-spectrum, safe, and stable viral inhibitor used to suppress a variety of viruses. However, little information is available on whether GRFT can prevent plant viral diseases. In this study, we constructed a GRFT overexpression vector containing the sweetpotato storage cell signal peptide and generated exogenous GRFT overexpression lines through genetic transformation. The transgenic plants showed notable resistance to sweetpotato virus disease in the virus nursery. To verify the antiplant virus function of GRFT, transient expression in tobacco leaves showed that GRFT inhibited the sweetpotato leaf curl virus (SPLCV). The replication of SPLCV was entirely inhibited when the concentration of GRFT reached a certain level. The results of pulldown and BIFC assays showed that GRFT did not interact with the six components of SPLCV. In addition, the mutated GRFTD/A without the binding ability of carbohydrate and anticoronavirus function, in which three aspartate residues at carbohydrate binding sites were all mutated to alanine, also inhibited SPLCV. Quantitative reverse-transcription PCR analyses showed that the tobacco antiviral-related genes HIN1, ICS1, WRKY40, and PR10 were overexpressed after GRFT/GRFTD/A injection. Furthermore, HIN1, ICS1, and PR10 were more highly expressed in the leaves injected with GRFTD/A. The results suggest that sweetpotato is able to express GRFT exogenously as a bioreactor. Moreover, exogenous GRFT expression inhibits plant viruses by promoting the expression of plant antiviral genes.

Cyanovirin-N binds to select SARS-CoV-2 spike oligosaccharides outside of the receptor binding domain and blocks infection by SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped positive stranded RNA virus which has caused the recent deadly pandemic called COVID-19. The SARS-CoV-2 virion is coated with a heavily glycosylated Spike glycoprotein which is responsible for attachment and entry into target cells. One, as yet unexploited strategy for preventing SARS-CoV-2 infections, is the targeting of the glycans on Spike. Lectins are carbohydrate-binding proteins produced by plants, algae, and cyanobacteria. Some lectins can neutralize enveloped viruses displaying external glycoproteins, offering an alternative therapeutic approach for the prevention of infection with virulent β-coronaviruses, such as SARS-CoV-2. Here we show that the cyanobacterial lectin cyanovirin-N (CV-N) can selectively target SARS-CoV-2 Spike oligosaccharides and inhibit SARS-CoV-2 infection in vitro and in vivo. CV-N neutralizes Delta and Omicron variants in vitro better than earlier circulating viral variants. CV-N binds selectively to Spike with a Kd as low as 15 nM and a stoichiometry of 2 CV-N: 1 Spike but does not bind to the receptor binding domain (RBD). Further mapping of CV-N binding sites on Spike shows that select high-mannose oligosaccharides in the S1 domain of Spike are targeted by CV-N. CV-N also reduced viral loads in the nares and lungs in vivo to protect hamsters against a lethal viral challenge. In summary, we present an anti-coronavirus agent that works by an unexploited mechanism and prevents infection by a broad range of SARS-CoV-2 strains.

A Genetically Engineered Biofilm Material for SARS-CoV-2 Capturing and Isolation

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is continuously infecting people all around the world since its outbreak in 2019. Studies for numerous infection detection strategies are continuing. The sensitivity of detection methods is crucial to separate people with mild infections from people who are asymptomatic. In this sense, a strategy that would help to capture and isolate the SARS-CoV-2 virus prior to tests can be effective and beneficial. To this extent, genetically engineered biomaterials grounding from the biofilm protein of Escherichia coli are beneficial due to their robustness and adaptability to various application areas. Through functionalizing the E. coli biofilm protein, diverse properties can be attained such as enzyme display, nanoparticle production, and medical implant structures. Here, E. coli species are employed to express major curli protein CsgA and Griffithsin (GRFT) as fusion proteins, through a complex formation using SpyTag and SpyCatcher domains. In this study, a complex system with a CsgA scaffold harboring the affinity of GRFT against Spike protein to capture and isolate SARS-CoV-2 virus is successfully developed. It is shown that the hybrid recombinant protein can dramatically increase the sensitivity of currently available lateral flow assays for Sars-CoV-2 diagnostics.

The Advances of Broad-Spectrum and Hot Anti-Coronavirus Drugs

Coronaviruses, mainly including severe acute respiratory syndrome virus, severe acute respiratory syndrome coronavirus 2, Middle East respiratory syndrome virus, human coronavirus OC43, chicken infectious bronchitis virus, porcine infectious gastroenteritis virus, porcine epidemic diarrhea virus, and murine hepatitis virus, can cause severe diseases in humans and livestock. The severe acute respiratory syndrome coronavirus 2 is infecting millions of human beings with high morbidity and mortality worldwide, and the multiplicity of swine epidemic diarrhea coronavirus in swine suggests that coronaviruses seriously jeopardize the safety of public health and that therapeutic intervention is urgently needed. Currently, the most effective methods of prevention and control for coronaviruses are vaccine immunization and pharmacotherapy. However, the emergence of mutated viruses reduces the effectiveness of vaccines. In addition, vaccine developments often lag behind, making it difficult to put them into use early in the outbreak. Therefore, it is meaningful to screen safe, cheap, and broad-spectrum antiviral agents for coronaviruses. This review systematically summarizes the mechanisms and state of anti-human and porcine coronavirus drugs, in order to provide theoretical support for the development of anti-coronavirus drugs and other antivirals.

Legume Lectins with Different Specificities as Potential Glycan Probes for Pathogenic Enveloped Viruses

Pathogenic enveloped viruses are covered with a glycan shield that provides a dual function: the glycan structures contribute to virus protection as well as host cell recognition. The three classical types of N-glycans, in particular complex glycans, high-mannose glycans, and hybrid glycans, together with some O-glycans, participate in the glycan shield of the Ebola virus, influenza virus, human cytomegalovirus, herpes virus, human immunodeficiency virus, Lassa virus, and MERS-CoV, SARS-CoV, and SARS-CoV-2, which are responsible for respiratory syndromes. The glycans are linked to glycoproteins that occur as metastable prefusion glycoproteins on the surface of infectious virions such as gp120 of HIV, hemagglutinin of influenza, or spike proteins of beta-coronaviruses. Plant lectins with different carbohydrate-binding specificities and, especially, mannose-specific lectins from the Vicieae tribe, such as pea lectin and lentil lectin, can be used as glycan probes for targeting the glycan shield because of their specific interaction with the α1,6-fucosylated core Man3GlcNAc2, which predominantly occurs in complex and hybrid glycans. Other plant lectins with Neu5Ac specificity or GalNAc/T/Tn specificity can also serve as potential glycan probes for the often sialylated complex glycans and truncated O-glycans, respectively, which are abundantly distributed in the glycan shield of enveloped viruses. The biomedical and therapeutical potential of plant lectins as antiviral drugs is discussed.

Contributions of the international plant science community to the fight against human infectious diseases - part 1: epidemic and pandemic diseases

Infectious diseases, also known as transmissible or communicable diseases, are caused by pathogens or parasites that spread in communities by direct contact with infected individuals or contaminated materials, through droplets and aerosols, or via vectors such as insects. Such diseases cause ˜17% of all human deaths and their management and control places an immense burden on healthcare systems worldwide. Traditional approaches for the prevention and control of infectious diseases include vaccination programmes, hygiene measures and drugs that suppress the pathogen, treat the disease symptoms or attenuate aggressive reactions of the host immune system. The provision of vaccines and biologic drugs such as antibodies is hampered by the high cost and limited scalability of traditional manufacturing platforms based on microbial and animal cells, particularly in developing countries where infectious diseases are prevalent and poorly controlled. Molecular farming, which uses plants for protein expression, is a promising strategy to address the drawbacks of current manufacturing platforms. In this review article, we consider the potential of molecular farming to address healthcare demands for the most prevalent and important epidemic and pandemic diseases, focussing on recent outbreaks of high-mortality coronavirus infections and diseases that disproportionately affect the developing world.

Combating Human Viral Diseases: Will Plant-Based Vaccines Be the Answer?

Molecular pharming or the technology of application of plants and plant cell culture to manufacture high-value recombinant proteins has progressed a long way over the last three decades. Whether generated in transgenic plants by stable expression or in plant virus-based transient expression systems, biopharmaceuticals have been produced to combat several human viral diseases that have impacted the world in pandemic proportions. Plants have been variously employed in expressing a host of viral antigens as well as monoclonal antibodies. Many of these biopharmaceuticals have shown great promise in animal models and several of them have performed successfully in clinical trials. The current review elaborates the strategies and successes achieved in generating plant-derived vaccines to target several virus-induced health concerns including highly communicable infectious viral diseases. Importantly, plant-made biopharmaceuticals against hepatitis B virus (HBV), hepatitis C virus (HCV), the cancer-causing virus human papillomavirus (HPV), human immunodeficiency virus (HIV), influenza virus, zika virus, and the emerging respiratory virus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been discussed. The use of plant virus-derived nanoparticles (VNPs) and virus-like particles (VLPs) in generating plant-based vaccines are extensively addressed. The review closes with a critical look at the caveats of plant-based molecular pharming and future prospects towards further advancements in this technology. The use of biopharmed viral vaccines in human medicine and as part of emergency response vaccines and therapeutics in humans looks promising for the near future.

Plant Molecular Farming as a Strategy Against COVID-19 - The Italian Perspective

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed more than 37,000 people in Italy and has caused widespread socioeconomic disruption. Urgent measures are needed to contain and control the virus, particularly diagnostic kits for detection and surveillance, therapeutics to reduce mortality among the severely affected, and vaccines to protect the remaining population. Here we discuss the potential role of plant molecular farming in the rapid and scalable supply of protein antigens as reagents and vaccine candidates, antibodies for virus detection and passive immunotherapy, other therapeutic proteins, and virus-like particles as novel vaccine platforms. We calculate the amount of infrastructure and production capacity needed to deal with predictable subsequent waves of COVID-19 in Italy by pooling expertise in plant molecular farming, epidemiology and the Italian health system. We calculate the investment required in molecular farming infrastructure that would enable us to capitalize on this technology, and provide a roadmap for the development of diagnostic reagents and biopharmaceuticals using molecular farming in plants to complement production methods based on the cultivation of microbes and mammalian cells.

Low-Cost, Large-Scale Production of the Anti-viral Lectin Griffithsin

Griffithsin, a broad-spectrum antiviral lectin, has potential to prevent and treat numerous viruses including HIV, HCV, HSV, SARS-CoV, and SARS-CoV-2. For these indications, the annual demand for Griffithsin could reach billions of doses and affordability is paramount. We report the lab-scale validation of a bioprocess that supports production volumes of >20 tons per year at a cost of goods sold below $3,500/kg. Recombinant expression in engineered E. coli enables Griffithsin titers ∼2.5 g/L. A single rapid precipitation step provides > 90% yield with 2-, 3-, and 4-log reductions in host cell proteins, endotoxin, and nucleic acids, respectively. Two polishing chromatography steps remove residual contaminants leading to pure, active Griffithsin. Compared to a conventional one this process shows lower costs and improved economies of scale. These results support the potential of biologics in very large-scale, cost-sensitive applications such as antivirals, and highlight the importance of bioprocess innovations in enabling these applications.

Griffithsin Inhibits Nipah Virus Entry and Fusion and Can Protect Syrian Golden Hamsters From Lethal Nipah Virus Challenge

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus that causes fatal encephalitis and respiratory disease in humans. There is currently no approved therapeutic for human use against NiV infection. Griffithsin (GRFT) is high-mannose oligosaccharide binding lectin that has shown in vivo broad-spectrum activity against viruses, including severe acute respiratory syndrome coronavirus, human immunodeficiency virus 1, hepatitis C virus, and Japanese encephalitis virus. In this study, we evaluated the in vitro antiviral activities of GRFT and its synthetic trimeric tandemer (3mG) against NiV and other viruses from 4 virus families. The 3mG had comparatively greater potency than GRFT against NiV due to its enhanced ability to block NiV glycoprotein-induced syncytia formation. Our initial in vivo prophylactic evaluation of an oxidation-resistant GRFT (Q-GRFT) showed significant protection against lethal NiV challenge in Syrian golden hamsters. Our results warrant further development of Q-GRFT and 3mG as potential NiV therapeutics.

In Preparation for Outdoor Pharming: Griffithsin Can Be Expressed in Nicotiana excelsiana and Retains Activity After Storage as Silage

Griffithsin is an algae-derived lectin with strong anti-viral activity against HIV and a positive safety profile. Multiple clinical studies are investigating griffithsin's utility as topical HIV microbicide. HIV microbicides are an extremely cost-sensitive market and plant-based griffithsin protein expression has the potential to meet those demands. The griffithsin product used in the clinic has been expressed and purified in N. benthamiana, using a TMV-based viral vector system, Geneware®. Outdoor pharming of biopharmaceuticals would further alleviate startup costs for biotechnology firms and may allow broader product accessibility. Therefore, this study assessed expression in a hybrid tobacco line, N. excelsiana, that is susceptible to TMV-based viral vectors and can be grown outdoors. In addition to using this hybrid line we expand on methods for in planta storage of griffithsin in leafy plants by ensiling kilogram quantities of griffithsin. The ensiling process allows year-round biomanufacturing, minimal environmental-controlled storage, and reduces the industry need for multiple growth areas to maintain multi-product manufacturing of plant-based pharmaceuticals. This study shows that griffithsin can be expressed in N. excelsiana and is stable, recoverable, and active from ensiled tissue. These studies can pave the way for future plant-based pharmaceuticals to be expressed and stored in this manner.

Plant-made HIV vaccines and potential candidates

Millions of people around the world suffer from heavy social and health burdens related to HIV/AIDS and its associated opportunistic infections. To reduce these burdens, preventive and therapeutic vaccines are required. Effective HIV vaccines have been under investigation for several decades using different animal models. Potential plant-made HIV vaccine candidates have also gained attention in the past few years. In addition to this, broadly neutralizing antibodies produced in plants which can target conserved viral epitopes and neutralize mutating HIV strains have been identified. Numerous epitopes of envelope glycoproteins and capsid proteins of HIV-1 are a part of HIV therapy. Here, we discuss some recent findings aiming to produce anti-HIV-1 recombinant proteins in engineered plants for AIDS prophylactics and therapeutic treatments.

The Emergency Response Capacity of Plant-Based Biopharmaceutical Manufacturing-What It Is and What It Could Be

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.

Griffithsin Retains Anti-HIV-1 Potency with Changes in gp120 Glycosylation and Complements Broadly Neutralizing Antibodies PGT121 and PGT126

Griffithsin (Grft) is an antiviral lectin that has been shown to potently inhibit HIV-1 by binding high-mannose N-linked glycosylation sites on HIV-1 gp120. A key factor for Grft potency is glycosylation at N295 of gp120, which is directly adjacent to N332, a target glycan for an entire class of broadly neutralizing antibodies (bNAbs). Here, we unify previous work on the importance of other glycans to Grft potency against HIV-1 and Grft's role in mediating the conformational change of gp120 by mutating nearly every glycosylation site in gp120. In addition to a significant loss of Grft activity by the removal of glycosylation at N295, glycan absence at N332 or N448 was found to have moderate effects on Grft potency. Interestingly, in the absence of N295, Grft effectiveness could be improved by a mutation that results in the glycan at N448 shifting to N446, indicating that the importance of individual glycans may be related to their effect on glycosylation density. Grft's ability to alter the structure of gp120, exposing the CD4 binding site, correlated with the presence of glycosylation at N295 only in clade B strains, not clade C strains. We further demonstrate that Grft can rescue the activity of the bNAbs PGT121 and PGT126 in the event of a loss or a shift of glycosylation at N332, where the bNAbs suffer a drastic loss of potency. Despite targeting the same region, Grft in combination with PGT121 and PGT126 produced additive effects. This indicates that Grft could be an important combinational therapeutic.

Impact of Q-Griffithsin anti-HIV microbicide gel in non-human primates: In situ analyses of epithelial and immune cell markers in rectal mucosa

Natural-product derived lectins can function as potent viral inhibitors with minimal toxicity as shown in vitro and in small animal models. We here assessed the effect of rectal application of an anti-HIV lectin-based microbicide Q-Griffithsin (Q-GRFT) in rectal tissue samples from rhesus macaques. E-cadherin⁺ cells, CD4⁺ cells and total mucosal cells were assessed using in situ staining combined with a novel customized digital image analysis platform. Variations in cell numbers between baseline, placebo and Q-GRFT treated samples were analyzed using random intercept linear mixed effect models. The frequencies of rectal E-cadherin⁺ cells remained stable despite multiple tissue samplings and Q-GRFT gel (0.1%, 0.3% and 1%, respectively) treatment. Whereas single dose application of Q-GRFT did not affect the frequencies of rectal CD4⁺ cells, multi-dose Q-GRFT caused a small, but significant increase of the frequencies of intra-epithelial CD4⁺ cells (placebo: median 4%; 1% Q-GRFT: median 7%) and of the CD4⁺ lamina propria cells (placebo: median 30%; 0.1–1% Q-GRFT: median 36–39%). The resting time between sampling points were further associated with minor changes in the total and CD4⁺ rectal mucosal cell levels. The results add to general knowledge of in vivo evaluation of anti-HIV microbicide application concerning cellular effects in rectal mucosa.

Griffithsin, a Highly Potent Broad-Spectrum Antiviral Lectin from Red Algae: From Discovery to Clinical Application

Virus entry into a susceptible host cell is the first step in the formation of all viral diseases. Controlling viral infections by disrupting viral entry is advantageous for antibody-mediated neutralization by the host’s immune system and as a preventive and therapeutic antiviral strategy. Recently, several plant-derived carbohydrate-binding proteins (lectins) have emerged as a new class of antiviral biologics by taking advantage of a unique glycosylation pattern only found on the surface of viruses. In particular, a red algae-derived griffithsin (GRFT) protein has demonstrated superior in vitro and in vivo antiviral activity with minimum host toxicity against a variety of clinically relevant, enveloped viruses. This review examines the structural characteristics of GRFT, focusing on its carbohydrate-binding capability. Its in vitro antiviral profiles against human immunodeficiency virus (HIV) are also discussed followed by a description of the results from a combination study using anti-HIV drugs. The results of several studies regarding its novel antiviral mechanism of action are provided in conjunction with an explanation of viral resistance profiles to GRFT. In addition, its in vitro and in vivo host toxicity profiles are summarized with its pharmacokinetic behavior using in vivo efficacy study results. Also, a large-scale production and formulation strategy, as well as a drug delivery strategy, for GRFT as a new class of broad-spectrum microbicides is discussed. Finally, results from two ongoing clinical studies examining GRFT’s effects on viruses are presented.

In vitro antiviral activity of Griffithsin against porcine epidemic diarrhea virus

Griffithsin is a lectin with potent antiviral activity against enveloped viruses. The objective of this study was to assess Griffithsin’s inhibitory effect on porcine epidemic diarrhea virus (PEDV). The results showed that Griffithsin reduced PEDV infection of Vero cells by approximately 82.8%. Moreover, using time-of-addition assays and RT-qPCR, we found that delayed addition of Griffithsin had a weaker inhibitory effect on PEDV than earlier treatment. The mechanism of Griffithsin’s action against PEDV involved both preventing viral attachment to host cells and disrupting cell-to-cell transmission; its dual mode of action distinguished Griffithsin from most other antiviral drugs. In conclusion, Griffithsin was identified as a potent PEDV inhibitor and may represent a candidate drug for preventing PEDV infection.

Griffithsin inhibits porcine reproductive and respiratory syndrome virus infection in vitro

Porcine reproductive and respiratory syndrome virus (PRRSV) is a pathogen that severely disrupts swine production. Despite sustained efforts, the disease is still endemic, with high mortality and morbidity. New antiviral strategies to control PRRSV are needed. Griffithsin, a red algal lectin, has potent antiviral effect on several human enveloped viruses, but this effect has not been demonstrated on PRRSV. Here, we first tested the in vitro antiviral activity of Griffithsin against PRRSV. Griffithsin exerted strong saccharide-dependent antiviral activity against PRRSV, probably through interactions with glycans on the surface of PRRSV that interfered with virus entry. Furthermore we revealed that Griffithsin's action on PRRSV involved blocking viral adsorption, and it had no effect on viral penetration. Besides Our findings also suggested that Griffithsin may interfere with cell-to-cell spread to prevent virus transmission. The remarkable potency profile of Griffithsin supports its potential value as an antiviral agent against PRRSV.

Pharmaceutical Approaches to HIV Treatment and Prevention

Human immunodeficiency virus (HIV) infection continues to pose a major infectious disease threat worldwide. It is characterized by the depletion of CD4+ T cells, persistent immune activation, and increased susceptibility to secondary infections. Advances in the development of antiretroviral drugs and combination antiretroviral therapy have resulted in a remarkable reduction in HIV-associated morbidity and mortality. Antiretroviral therapy (ART) leads to effective suppression of HIV replication with partial recovery of host immune system and has successfully transformed HIV infection from a fatal disease to a chronic condition. Additionally, antiretroviral drugs have shown promise for prevention in HIV pre-exposure prophylaxis and treatment as prevention. However, ART is unable to cure HIV. Other limitations include drug-drug interactions, drug resistance, cytotoxic side effects, cost, and adherence. Alternative treatment options are being investigated to overcome these challenges including discovery of new molecules with increased anti-viral activity and development of easily administrable drug formulations. In light of the difficulties associated with current HIV treatment measures, and in the continuing absence of a cure, the prevention of new infections has also arisen as a prominent goal among efforts to curtail the worldwide HIV pandemic. In this review, the authors summarize currently available anti-HIV drugs and their combinations for treatment, new molecules under clinical development and prevention methods, and discuss drug delivery formats as well as associated challenges and alternative approaches for the future.

Surface-displayed porcine reproductive and respiratory syndrome virus from cell culture onto gram-positive enhancer matrix particles

Vaccine immunization is now one of the most effective ways to control porcine reproductive and respiratory syndrome virus (PRRSV) infection. Impurity is one of the main factors affecting vaccine safety and efficacy. Here we present a novel innovative PRRSV purification approach based on surface display technology. First, a bifunctional protein PA-GRFT (protein anchor-griffithsin), the crucial factor in the purification process, was successfully produced in Escherichia coli yielding 80 mg/L of broth culture. Then PRRSV purification was performed by incubation of PA-GRFT with PRRSV and gram-positive enhancer matrix (GEM) particles, followed by centrifugation to collect virions loaded onto GEM particles. Our results showed that most of the bulk impurities had been removed, and PA-GRFT could capture PRRSV onto GEM particles. Our lactic acid bacteria-based purification method, which is promising as ease of operation, low cost and easy to scale-up, may represent a candidate method for the large-scale purification of this virus for vaccine production.

Technoeconomic Modeling of Plant-Based Griffithsin Manufacturing

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.

High-level expression of the HIV entry inhibitor griffithsin from the plastid genome and retention of biological activity in dried tobacco leaves

KEY MESSAGE

The potent anti-HIV microbicide griffithsin was expressed to high levels in tobacco chloroplasts, enabling efficient purification from both fresh and dried biomass, thus providing storable material for inexpensive production and scale-up on demand. The global HIV epidemic continues to grow, with 1.8 million new infections occurring per year. In the absence of a cure and an AIDS vaccine, there is a pressing need to prevent new infections in order to curb the disease. Topical microbicides that block viral entry into human cells can potentially prevent HIV infection. The antiviral lectin griffithsin has been identified as a highly potent inhibitor of HIV entry into human cells. Here we have explored the possibility to use transplastomic plants as an inexpensive production platform for griffithsin. We show that griffithsin accumulates in stably transformed tobacco chloroplasts to up to 5% of the total soluble protein of the plant. Griffithsin can be easily purified from leaf material and shows similarly high virus neutralization activity as griffithsin protein recombinantly expressed in bacteria. We also show that dried tobacco provides a storable source material for griffithsin purification, thus enabling quick scale-up of production on demand.

Development of a Vaginal Fast-Dissolving Insert Combining Griffithsin and Carrageenan for Potential Use Against Sexually Transmitted Infections

Precoital, on-demand topical microbicides to reduce a woman's risk of sexually transmitted infections have been in development for nearly 3 decades, but no product has been approved due to acceptability issues and poor adherence in clinical trials. We set out to develop a self-administered vaginal fast-dissolving insert (FDI) produced by freeze-drying that would deliver safe and effective amounts of the antiviral agents griffithsin (GRFT) and carrageenan (CG) and would have properties women and their partners find acceptable. We evaluated FDI physical criteria, attributes of the gel produced upon dissolving, and GRFT stability. The lead formulation, FDI-024, was selected from 13 candidates and contains 4 mg of GRFT, 15 mg of CG, and excipients (the cryoprotectant sucrose and bulking agents dextran 40 and mannitol). The FDI exhibits good friability and hardness and is stable for at least 6 months at up to 40°C/75% relative humidity. It disintegrates in less than 60 s in a physiologically relevant volume (∼1 mL) of simulated vaginal fluid, forming a viscous semi-solid gel with favorable mucoadhesive and spreading properties. The formulation retains the antiviral activity of GRFT and CG against HIV type 1 and human papillomavirus, respectively, in cell-based assays.

Historical development of vaginal microbicides to prevent sexual transmission of HIV in women: from past failures to future hopes

Infection with human immunodeficiency virus (HIV) remains a global public health concern and is particularly serious in low- and middle-income countries. Widespread sexual violence and poverty, among other factors, increase the risk of infection in women, while currently available prevention methods are outside the control of most. This has driven the study of vaginal microbicides to prevent sexual transmission of HIV from men to women in recent decades. The first microbicides evaluated were formulated as gels for daily use and contained different substances such as surfactants, acidifiers and monoclonal antibodies, which failed to demonstrate efficacy in clinical trials. A gel containing the reverse transcriptase inhibitor tenofovir showed protective efficacy in women. However, the lack of adherence by patients led to the search for dosage forms capable of releasing the active principle for longer periods, and hence to the emergence of the vaginal ring loaded with dapivirine, which requires a monthly application and is able to reduce the sexual transmission of HIV. The future of vaginal microbicides will feature the use of alternative dosage forms, nanosystems for drug release and probiotics, which have emerged as potential microbicides but are still in the early stages of development. Protecting women with vaginal microbicide formulations would, therefore, be a valuable tool for avoiding sexual transmission of HIV.

Griffithsin-Modified Electrospun Fibers as a Delivery Scaffold To Prevent HIV Infection

Despite current prophylactic strategies, sexually transmitted infections (STIs) remain significant contributors to global health challenges, spurring the development of new multipurpose delivery technologies to protect individuals from and treat virus infections. However, there are few methods currently available to prevent and no method to date that cures human immunodeficiency virus (HIV) infection or combinations of STIs. While current oral and topical preexposure prophylaxes have protected against HIV infection, they have primarily relied on antiretrovirals (ARVs) to inhibit infection. Yet continued challenges with ARVs include user adherence to daily treatment regimens and the potential toxicity and antiviral resistance associated with chronic use. The integration of new biological agents may avert some of these adverse effects while also providing new mechanisms to prevent infection. Of the biologic-based antivirals, griffithsin (GRFT) has demonstrated potent inhibition of HIV-1 (and a multitude of other viruses) by adhering to and inactivating HIV-1 immediately upon contact. In parallel with the development of GRFT, electrospun fibers (EFs) have emerged as a promising platform for the delivery of agents active against HIV infection. In the study described here, our goal was to extend the mechanistic diversity of active agents and electrospun fibers by incorporating the biologic GRFT on the EF surface rather than within the EFs to inactivate HIV prior to cellular entry. We fabricated and characterized GRFT-modified EFs (GRFT-EFs) with different surface modification densities of GRFT and demonstrated their safety and efficacy against HIV-1 infection in vitro We believe that EFs are a unique platform that may be enhanced by incorporation of additional antiviral agents to prevent STIs via multiple mechanisms.

Griffithsin: An Antiviral Lectin with Outstanding Therapeutic Potential

Griffithsin (GRFT), an algae-derived lectin, is one of the most potent viral entry inhibitors discovered to date. It is currently being developed as a microbicide with broad-spectrum activity against several enveloped viruses. GRFT can inhibit human immunodeficiency virus (HIV) infection at picomolar concentrations, surpassing the ability of most anti-HIV agents. The potential to inhibit other viruses as well as parasites has also been demonstrated. Griffithsin's antiviral activity stems from its ability to bind terminal mannoses present in high-mannose oligosaccharides and crosslink these glycans on the surface of the viral envelope glycoproteins. Here, we review structural and biochemical studies that established mode of action and facilitated construction of GRFT analogs, mechanisms that may lead to resistance, and in vitro and pre-clinical results that support the therapeutic potential of this lectin.

Rice endosperm is cost-effective for the production of recombinant griffithsin with potent activity against HIV

Protein microbicides containing neutralizing antibodies and antiviral lectins may help to reduce the rate of infection with human immunodeficiency virus (HIV) if it is possible to manufacture the components in large quantities at a cost affordable in HIV-endemic regions such as sub-Saharan Africa. We expressed the antiviral lectin griffithsin (GRFT), which shows potent neutralizing activity against HIV, in the endosperm of transgenic rice plants (Oryza sativa), to determine whether rice can be used to produce inexpensive GRFT as a microbicide ingredient. The yield of (OS) GRFT in the best-performing plants was 223 μg/g dry seed weight. We also established a one-step purification protocol, achieving a recovery of 74% and a purity of 80%, which potentially could be developed into a larger-scale process to facilitate inexpensive downstream processing. (OS) GRFT bound to HIV glycans with similar efficiency to GRFT produced in Escherichia coli. Whole-cell assays using purified (OS) GRFT and infectivity assays using crude extracts of transgenic rice endosperm confirmed that both crude and pure (OS) GRFT showed potent activity against HIV and the crude extracts were not toxic towards human cell lines, suggesting they could be administered as a microbicide with only minimal processing. A freedom-to-operate analysis confirmed that GRFT produced in rice is suitable for commercial development, and an economic evaluation suggested that 1.8 kg/ha of pure GRFT could be produced from rice seeds. Our data therefore indicate that rice could be developed as an inexpensive production platform for GRFT as a microbicide component.

A scalable low-cost cGMP process for clinical grade production of the HIV inhibitor 5P12-RANTES in Pichia pastoris

In the continued absence of an effective anti-HIV vaccine, approximately 2 million new HIV infections occur every year, with over 95% of these in developing countries. Calls have been made for the development of anti-HIV drugs that can be formulated for topical use to prevent HIV transmission during sexual intercourse. Because these drugs are principally destined for use in low-resource regions, achieving production costs that are as low as possible is an absolute requirement. 5P12-RANTES, an analog of the human chemokine protein RANTES/CCL5, is a highly potent HIV entry inhibitor which acts by achieving potent blockade of the principal HIV coreceptor, CCR5. Here we describe the development and optimization of a scalable low-cost production process for 5P12-RANTES based on expression in Pichia pastoris. At pilot (150 L) scale, this cGMP compliant process yielded 30 g of clinical grade 5P12-RANTES. As well as providing sufficient material for the first stage of clinical development, this process represents an important step towards achieving production of 5P12-RANTES at a cost and scale appropriate to meet needs for topical HIV prevention worldwide.

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New medicines are required to prevent the spread of HIV/AIDS in low-resource regions.

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5P12-RANTES, a chemokine analog, is a promising new candidate drug.

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We describe a process for producing clinical grade cGMP 5P12-RANTES in Pichia pastoris.

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This is a key step to achieving production at cost and scale appropriate for use worldwide.

Bulk production of the antiviral lectin griffithsin

Application of plant-based protein expression systems for bulk production of recombinant protein pharmaceuticals is building momentum. There are considerable regulatory challenges to consider in commercialization of plant-made pharmaceuticals (PMPs), some of which are inherent to plant-production systems and others that are common with other production systems, but are new to PMPs because of the youth of the industry. In this review, we discuss our recent and ongoing experience with bulk production of the HIV microbicide candidate, griffithsin (GRFT), utilizing plant-based transient protein expression, with specific focus on areas relevant to commercial manufacturing of bulk GRFT active pharmaceutical ingredient (API). Analytical programs have been developed for the qualification and monitoring of both the expression vector system and the API detailing our experience and plans for each. Monitoring postpurification protein modifications are discussed in relation to stability and safety programs. Expression, processing and analytics programs are associated with increased manufacturing costs in current good manufacturing practice (cGMP) production because of the required qualification testing. The impact of these costs on the overall cost of goods is particularly relevant to GRFT manufacturing because GRFT, as an HIV microbicide, is most needed in populations at high risk for HIV exposure in resource-poor countries. Consequently, GRFT for microbicide applications is a very cost-sensitive recombinant PMP. We have therefore emphasized maintaining a low cost of goods. We provide a review of the literature on the economics of PMPs with various expression systems and how they may impact production costs and complexity.

Proteins, peptides, polysaccharides, and nucleotides with inhibitory activity on human immunodeficiency virus and its enzymes

Human immunodeficiency virus (HIV), the causative agent of acquired immune deficiency syndrome, has claimed innumerable lives in the past. Many biomolecules which suppress HIV replication and also other biomolecules that inhibit enzymes essential to HIV replication have been reported. Proteins including a variety of milk proteins, ribosome-inactivating proteins, ribonucleases, antifungal proteins, and trypsin inhibitors; peptides comprising cathelicidins, defensins, synthetic peptides, and others; polysaccharides and polysaccharopeptides; nucleosides, nucleotides, and ribozymes, demonstrated anti-HIV activity. In many cases, the mechanism of anti-HIV action has been elucidated. Strategies have been devised to augment the anti-HIV potency of these compounds.