Inhibition of HIV infectivity by a natural human isolate of Lactobacillus jensenii engineered to express functional two-domain CD4

Metabolic engineering of Lactobacilli spp. for disease treatment

BACKGROUND

A variety of probiotics have been utilized as chassis strains and engineered to develop the synthetic probiotics for disease treatment. Among these probiotics, Lactobacilli, which are generally viewed as safe and capable of colonizing the gastrointestinal tract effectively, are widely used. We review recent advancements in the engineering of Lactobacilli for disease treatment. Specifically, the Lactobacilli that are used for the construction of synthetic probiotics, the application of these engineered strains for diseases treatment, and the therapeutic outcomes of these engineered microbes are summarized in this review. Moreover, the applications of these engineered strains for disease treatment are categorized based on their engineering strategies. Of note, we compare the advantages and disadvantages of various engineering strategies and offer insights for the future development of genetically modified Lactobacillus strains with stable and safe properties.

SHORT CONCLUSION

Our study comprehensively reviews researches on engineering diverse Lactobacillus strains for disease treatment, categorized by their engineering strategies, and emphasizes the importance of developing synthetic probiotics with stable and safe characteristics to enhance their therapeutic applications.

Designer probiotics: Opening the new horizon in diagnosis and prevention of human diseases

Probiotic microorganisms have been used for therapeutic purposes for over a century, and recent advances in biotechnology and genetic engineering have opened up new possibilities for developing therapeutic approaches using indigenous probiotic microorganisms. Diseases are often related to metabolic and immunological factors, which play a critical role in their onset. With the help of advanced genetic tools, probiotics can be modified to produce or secrete important therapeutic peptides directly into mucosal sites, increasing their effectiveness. One potential approach to enhancing human health is through the use of designer probiotics, which possess immunogenic characteristics. These genetically engineered probiotics hold promise in providing novel therapeutic options. In addition to their immunogenic properties, designer probiotics can also be equipped with sensors and genetic circuits, enabling them to detect a range of diseases with remarkable precision. Such capabilities may significantly advance disease diagnosis and management. Furthermore, designer probiotics have the potential to be used in diagnostic applications, offering a less invasive and more cost-effective alternative to conventional diagnostic techniques. This review offers an overview of the different functional aspects of the designer probiotics and their effectiveness on different diseases and also, we have emphasized their limitations and future implications. A comprehensive understanding of these functional attributes may pave the way for new avenues of prevention and the development of effective therapies for a range of diseases.

Synthetic biology-inspired cell engineering in diagnosis, treatment, and drug development

The fast-developing synthetic biology (SB) has provided many genetic tools to reprogram and engineer cells for improved performance, novel functions, and diverse applications. Such cell engineering resources can play a critical role in the research and development of novel therapeutics. However, there are certain limitations and challenges in applying genetically engineered cells in clinical practice. This literature review updates the recent advances in biomedical applications, including diagnosis, treatment, and drug development, of SB-inspired cell engineering. It describes technologies and relevant examples in a clinical and experimental setup that may significantly impact the biomedicine field. At last, this review concludes the results with future directions to optimize the performances of synthetic gene circuits to regulate the therapeutic activities of cell-based tools in specific diseases.

An optimized electrotransformation protocol for Lactobacillus jensenii

Engineered bacteria are promising candidates for in situ detection and treatment of diseases. The female uro-genital tract presents several pathologies, such as sexually transmitted diseases or genital cancer, that could benefit from such technology. While bacteria from the gut microbiome are increasingly engineered, the use of chassis isolated from the female uro-genital resident flora has been limited. A major hurdle to implement the experimental throughput required for efficient engineering in these non-model bacteria is their low transformability. Here we report an optimized electrotransformation protocol for Lactobacillus jensenii, one the most widespread species across vaginal microflora. Starting from classical conditions, we optimized buffers, electric field parameters, cuvette type and DNA quantity to achieve an 80-fold improvement in transformation efficiency, with up to 3.5·103 CFUs/μg of DNA in L. jensenii ATCC 25258. We also identify several plasmids that are maintained and support reporter gene expression in L. jensenii. Finally, we demonstrate that our protocol provides increased transformability in three independent clinical isolates of L. jensenii. This work will facilitate the genetic engineering of L. jensenii and enable its use for addressing challenges in gynecological healthcare.

Lactobacilli, a Weapon to Counteract Pathogens through the Inhibition of Their Virulence Factors

To date, several studies have reported an alarming increase in pathogen resistance to current antibiotic therapies and treatments. Therefore, the search for effective alternatives to counter their spread and the onset of infections is becoming increasingly important.

Use of genetically modified lactic acid bacteria and bifidobacteria as live delivery vectors for human and animal health

There is now strong evidence to support the interest in using lactic acid bacteria (LAB)in particular, strains of lactococci and lactobacilli, as well as bifidobacteria, for the development of new live vectors for human and animal health purposes. LAB are Gram-positive bacteria that have been used for millennia in the production of fermented foods. In addition, numerous studies have shown that genetically modified LAB and bifodobacteria can induce a systemic and mucosal immune response against certain antigens when administered mucosally. They are therefore good candidates for the development of new mucosal delivery strategies and are attractive alternatives to vaccines based on attenuated pathogenic bacteria whose use presents health risks. This article reviews the most recent research and advances in the use of LAB and bifidobacteria as live delivery vectors for human and animal health.

Chlamydia trachomatis Enhances HIV Infection of Non-Activated PBMCs

Sexual contact is the most common route of HIV transmission, and the concurrent presence of sexually transmitted infections (STIs) such as Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (gonococcus, GC) is known to increase the HIV risk. Antibiotic treatment decreases the incidence of STIs but not HIV. CT and GC activate Toll-like receptors (TLRs) 2 and 4, which act as sensors of microbial infection are critical for initiating immune responses to control infection. We have previously shown that GC enhances HIV infection of primary resting CD4+ T cells through activation of TLR2 but not TLR4. In this study, we determined the effect of live and fixed CT and different species of lactobacilli including L. jensenii and L. reuteri on HIV infection of freshly isolated PBMCs. We found that pretreatment of freshly isolated PBMCs with fresh or fixed CT, but not lactobacilli, promoted HIV infection of freshly isolated CD4+ T cells. Together with our previous reports, we concluded that STIs such as CT and GC but not commensal bacteria like lactobacilli enhanced HIV infection, possibly through immune activation. Importantly, the enhancement effect of fixed CT on HIV infection may explain the failure of antibiotic treatments to reduce the HIV incidence. Combined strategies to inhibit STI growth and STI-mediated mucosal immune activation should be considered for HIV prevention in the settings of STIs.

The potential application of probiotics for the prevention and treatment of COVID-19

Background

Given the severe infection, poor prognosis, and the low number of available effective drugs, potential prevention and treatment strategies for COVID-19 need to be urgently developed.

Main body

Herein, we present and discuss the possible protective and therapeutic mechanisms of human microbiota and probiotics based on the previous and recent findings. Microbiota and probiotics consist of mixed cultures of living microorganisms that can positively affect human health through their antiviral, antibacterial, anti-inflammatory, and immunomodulatory effect. In the current study, we address the promising advantages of microbiota and probiotics in decreasing the risk of COVID-19.

Conclusions

Thus, we recommend further studies be conducted for assessing and evaluating the capability of these microbes in the battle against COVID-19.

Deployment of Engineered Microbes: Contributions to the Bioeconomy and Considerations for Biosecurity

Engineering at microscopic scales has an immense effect on the modern bioeconomy. Microbes contribute to such disparate markets as chemical manufacturing, fuel production, crop optimization, and pharmaceutical synthesis, to name a few. Due to new and emerging synthetic biology technologies, and the sophistication and control afforded by them, we are on the brink of deploying engineered microbes to not only enhance traditional applications but also to introduce these microbes to sectors, contexts, and formats not previously attempted. In microbially managed medicine, microbial engineering holds promise for increasing efficacy, improving tissue penetration, and sustaining treatment. In the environment, the most effective areas for deployment are in the management of crops and protection of ecosystems. However, caution is warranted before introducing engineered organisms to new environments where they may proliferate without control and could cause unforeseen effects. We summarize ideas and data that can inform identification and assessment of the risks that these tools present to ensure that realistic hazards are described and unrealistic ones do not hinder advancement. Further, because modes of containment are crucial complements to deployment, we describe the state of the art in microbial biocontainment strategies, current gaps, and how these gaps might be addressed through technological advances in synthetic engineering. Collectively, this work highlights engineered microbes as a foundational and expanding facet of the bioeconomy, projects their utility in upcoming deployments outside the laboratory, and identifies knowns and unknowns that will be necessary considerations and points of focus in this endeavor.

Lactobacilli Expressing Broadly Neutralizing Nanobodies against HIV-1 as Potential Vectors for HIV-1 Prophylaxis?

In the absence of an active prophylactic vaccine against HIV-1, passively administered, broadly neutralizing antibodies (bnAbs) identified in some chronically infected persons were shown to prevent HIV-1 infection in animal models. However, passive administration of bnAbs may not be suited to prevent sexual HIV-1 transmission in high-risk cohorts, as a continuous high level of active bnAbs may be difficult to achieve at the primary site of sexual transmission, the human vagina with its acidic pH. Therefore, we used Lactobacillus, a natural commensal in the healthy vaginal microbiome, to express bn nanobodies (VHH) against HIV-1 that we reported previously. After demonstrating that recombinant VHHA6 expressed in E. coli was able to protect humanized mice from mucosal infection by HIV-1Bal, we expressed VHHA6 in a soluble or in a cell-wall-anchored form in Lactobacillus rhamnosus DSM14870. This strain is already clinically applied for treatment of bacterial vaginosis. Both forms of VHHA6 neutralized a set of primary epidemiologically relevant HIV-1 strains in vitro. Furthermore, VHHA6 was still active at an acidic pH. Thus, lactobacilli expressing bn VHH potentially represent an attractive vector for the passive immunization of women in cohorts at high risk of HIV-1 transmission.

Blocking HIV-1 Infection by Chromosomal Integrative Expression of Human CD4 on the Surface of Lactobacillus acidophilus ATCC 4356

Lactobacillus bacteria are potential delivery vehicles for biopharmaceutical molecules because they are well-recognized as safe microorganisms that naturally inhabit the human body. The goal of this study was to employ these lactobacilli to combat human immunodeficiency virus type 1 (HIV-1) infection and transmission. By using a chromosomal integration method, we engineered Lactobacillus acidophilus ATCC 4356 to display human CD4, the HIV-1 receptor, on the cell surface. Since human CD4 can bind to any infectious HIV-1 particles, the engineered lactobacilli can potentially capture HIV-1 of different subtypes and prevent infection. Our data demonstrate that the CD4-carrying bacteria are able to adsorb HIV-1 particles and reduce infection significantly in vitro and also block intrarectal HIV-1 infection in a humanized mouse model in preliminary tests in vivo Our results support the potential of this approach to decrease the efficiency of HIV-1 sexual transmission.IMPORTANCE In the absence of an effective vaccine, alternative approaches to block HIV-1 infection and transmission with commensal bacteria expressing antiviral proteins are being considered. This report provides a proof-of-concept by using Lactobacillus bacteria stably expressing the HIV-1 receptor CD4 to capture and neutralize HIV-1 in vitro and in a humanized mouse model. The stable expression of antiviral proteins, such as CD4, following genomic integration of the corresponding genes into this Lactobacillus strain may contribute to the prevention of HIV-1 sexual transmission.

A Synthetic System That Senses Candida albicans and Inhibits Virulence Factors

Due to a limited set of antifungals available and problems in early diagnosis, invasive fungal infections caused by Candida species are among the most common hospital-acquired infections with staggering mortality rates. Here, we describe an engineered system able to sense and respond to the fungal pathogen Candida albicans, the most common cause of candidemia. In doing so, we identified hydroxyphenylacetic acid (HPA) as a novel molecule secreted by C. albicans. Furthermore, we engineered E. coli to be able to sense HPA produced by C. albicans. Finally, we constructed a sense-and-respond system by coupling the C. albicans sensor to the production of an inhibitor of hypha formation, thereby reducing filamentation, virulence factor expression, and fungal-induced epithelial damage. This system could be used as a basis for the development of novel prophylactic approaches to prevent fungal infections.

Protective Effects of Cell-Free Supernatant and Live Lactic Acid Bacteria Isolated from Thai Pigs Against a Pandemic Strain of Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea virus (PEDV) is a coronavirus which causes severe diarrhea and fatal dehydration in piglets. In general, probiotic supplements could enhance recovery and protect piglets against enteric pathogens. Seven local lactic acid bacteria (LAB), (Ent. faecium 79N and 40N, Lact. plantarum 22F, 25F and 31F, Ped. acidilactici 72N and Ped. pentosaceus 77F) from pig feces were well-characterized as high potential probiotics. Cell-free supernatants (CFS) and live LAB were evaluated for antiviral activities by co-incubation on Vero cells and challenged with a pandemic strain of PEDV isolated from pigs in Thailand. Cell survival and viral inhibition were determined by cytopathic effect (CPE) reduction assay and confirmed by immunofluorescence. At 1:16, CFS dilution (pH 6.3–6.8) showed no cytotoxicity in Vero cells and was therefore used as the dilution for antiviral assays. The diluted CFS of all Lact. plantarum showed the antiviral effect against PEDV; however, the same antiviral effect could not be observed in Ent. faecium and Pediococcus strains. In competitive experiment, only live Lact. plantarum 25F and Ped. pentosaceus 77F showed CPE reduction in the viral infected cells to <50% observed field area. This study concluded that the CFS of all tested lactobacilli, and live Lact. plantarum (22F and 25F) and Pediococcus strains 72N and 77F could reduce infectivity of the pandemic strain of PEDV from pigs in Thailand on the target Vero cells.

Gut microbes as future therapeutics in treating inflammatory and infectious diseases: Lessons from recent findings

The human gut microbiota has been the interest of extensive research in recent years and our knowledge on using the potential capacity of these microbes are growing rapidly. Microorganisms colonized throughout the gastrointestinal tract of human are coevolved through symbiotic relationship and can influence physiology, metabolism, nutrition and immune functions of an individual. The gut microbes are directly involved in conferring protection against pathogen colonization by inducing direct killing, competing with nutrients and enhancing the response of the gut-associated immune repertoire. Damage in the microbiome (dysbiosis) is linked with several life-threatening outcomes viz. inflammatory bowel disease, cancer, obesity, allergy, and auto-immune disorders. Therefore, the manipulation of human gut microbiota came out as a potential choice for therapeutic intervention of the several human diseases. Herein, we review significant studies emphasizing the influence of the gut microbiota on the regulation of host responses in combating infectious and inflammatory diseases alongside describing the promises of gut microbes as future therapeutics.

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.

HIV Entry and Its Inhibition by Bifunctional Antiviral Proteins

HIV entry is a highly specific and time-sensitive process that can be divided into receptor binding, coreceptor binding, and membrane fusion. Bifunctional antiviral proteins (bAVPs) exploit the multi-step nature of the HIV entry process by binding to two different extracellular targets. They are generated by expressing a fusion protein containing two entry inhibitors with a flexible linker. The resulting fusion proteins exhibit exceptional neutralization potency and broad cross-clade inhibition. In this review, we summarize the HIV entry process and provide an overview of the design, antiviral potency, and methods of delivery of bAVPs. Additionally, we discuss the advantages and limitations of bAVPs for HIV prevention and treatment.

Rational CCL5 mutagenesis integration in a lactobacilli platform generates extremely potent HIV-1 blockers

Efforts to improve existing anti-HIV-1 therapies or develop preventatives have identified CCR5 as an important target and CCL5 as an ideal scaffold to sculpt potent HIV-1 entry inhibitors. We created novel human CCL5 variants that exhibit exceptional anti-HIV-1 features using recombinant lactobacilli (exploited for live microbicide development) as a screening platform. Protein design, expression and anti-HIV-1 activity flowed in iterative cycles, with a stepwise integration of successful mutations and refinement of an initial CCL5 mutant battery towards the generation of two ultimate CCL5 derivatives, a CCR5 agonist and a CCR5 antagonist with similar anti-HIV-1 potency. The CCR5 antagonist was tested in human macrophages and against primary R5 HIV-1 strains, exhibiting cross-clade low picomolar IC50 activity. Moreover, its successful combination with several HIV-1 inhibitors provided the ground for conceiving therapeutic and preventative anti-HIV-1 cocktails. Beyond HIV-1 infection, these CCL5 derivatives may now be tested against several inflammation-related pathologies where the CCL5:CCR5 axis plays a relevant role.

The Human Microbiota, Infectious Disease, and Global Health: Challenges and Opportunities

Despite significant advances in treating infectious diseases worldwide, morbidity and mortality associated with pathogen infection remains extraordinarily high and represents a critical scientific and global health challenge. Current strategies to combat these infectious agents include a combination of vaccines, small molecule drugs, increased hygiene standards, and disease-specific interventions. While these approaches have helped to drastically reduce the incidence and number of deaths associated with infection, continued investment in current strategies and the development of novel therapeutic approaches will be required to address these global health threats. Recently, human- and vector-associated microbiotas, the assemblages of microorganisms living on and within their hosts, have emerged as a potentially important factor mediating both infection risk and disease progression. These complex microbial communities are involved in intricate and dynamic interactions with both pathogens as well as the innate and adaptive immune systems of their hosts. Here, we discuss recent findings that have illuminated the importance of resident microbiotas in infectious disease, emphasizing opportunities for novel therapeutic intervention and future challenges for the field. Our discussion will focus on four major global health threats: tuberculosis, malaria, HIV, and enteric/diarrheal diseases. We hope this Perspective will highlight the many opportunities for chemists and chemical biologists in this field as well as inspire efforts to elucidate the mechanisms underlying established disease correlations, identify novel microbiota-based risk factors, and develop new therapeutic interventions.

Therapeutic Opportunities in the Vaginal Microbiome

The reproductive tract of females lies at the core of humanity. The immensely complex process that leads to successful reproduction is miraculous yet invariably successful. Microorganisms have always been a cause for concern for their ability to infect this region, yet it is other, nonpathogenic microbial constituents now uncovered by sequencing technologies that offer hope for improving health. The universality of Lactobacillus species being associated with health is the basis for therapeutic opportunities, including through engineered strains. The manipulation of these and other beneficial constituents of the microbiota and their functionality, as well as their metabolites, forms the basis for new diagnostics and interventions. Within 20 years, we should see significant improvements in how cervicovaginal health is restored and maintained, thus providing relief to the countless women who suffer from microbiota-associated disorders.

Engineered Probiotics: Applications and Biological Containment

Bioengineered probiotics represent the next generation of whole cell-mediated biotherapeutics. Advances in synthetic biology, genome engineering, and DNA sequencing and synthesis have enabled scientists to design and develop probiotics with increased stress tolerance and the ability to target specific pathogens and their associated toxins, as well as to mediate targeted delivery of vaccines, drugs, and immunomodulators directly to host cells. Herein, we review the most significant advances in the development of this field. We discuss the critical issue of biological containment and consider the role of synthetic biology in the design and construction of the probiotics of the future.

Probiotics in health maintenance: do they really work?

Probiotics are live micro-organisms that confer a health benefit to the host by providing both a nutritional benefit and protection against pathogens. This is a review of the present state of knowledge concerning probiotics, with emphasis on the criteria used for selection and clinical evidence of their beneficial effects.

Expression of Human Immunodeficiency Virus Type 1 Neutralizing Antibody Fragments Using Human Vaginal Lactobacillus

Eradication of human immunodeficiency virus type 1 (HIV-1) by vaccination with epitopes that produce broadly neutralizing antibodies is the ultimate goal for HIV prevention. However, generating appropriate immune responses has proven difficult. Expression of broadly neutralizing antibodies by vaginal colonizing lactobacilli provides an approach to passively target these antibodies to the mucosa. We tested the feasibility of expressing single-chain and single-domain antibodies (dAbs) in Lactobacillus to be used as a topical microbicide/live biotherapeutic. Lactobacilli provide an excellent platform to express anti-HIV proteins. Broadly neutralizing antibodies have been identified against epitopes on the HIV-1 envelope and have been made into active antibody fragments. We tested single-chain variable fragment m9 and dAb-m36 and its derivative m36.4 as prototype antibodies. We cloned and expressed the antibody fragments m9, m36, and m36.4 in Lactobacillus jensenii-1153 and tested the expression levels and functionality. We made a recombinant L. jensenii 1153-1128 that expresses dAb-m36.4. All antibody fragments m9, m36, and m36.4 were expressed by lactobacilli. However, we noted the smaller m36/m36.4 were expressed to higher levels, ≥3 μg/ml. All L. jensenii-expressed antibody fragments bound to gp120/CD4 complex; Lactobacillus-produced m36.4 inhibited HIV-1_BaL in a neutralization assay. Using a TZM-bl assay, we characterized the breadth of neutralization of the m36.4. Delivery of dAbs by Lactobacillus could provide passive transfer of these antibodies to the mucosa and longevity at the site of HIV-1 transmission.

Bioengineered probiotics as a new hope for health and diseases: an overview of potential and prospects

Despite the use of microorganisms as therapeutics for over a century, the scientific and clinical admiration of their potential is a recent phenomenon. Genome sequencing and genetic engineering has enabled researchers to develop novel strategies, such as bioengineered probiotics or pharmabiotics, which may become a therapeutic strategy. Bioengineered probiotics with multiple immunogenic or antagonistic properties could be a viable option to improve human health. The bacteria are tailored to deliver drugs, therapeutic proteins or gene therapy vectors with precision and a higher degree of site specificity than conventional drug administration regimes. This article provides an overview of methodological concepts, thereby encouraging research and interest in this topic, with the ultimate goal of using designer probiotics as therapeutics in clinical practice.

Inhibition of Plasmodium berghei Development in Mosquitoes by Effector Proteins Secreted from Asaia sp. Bacteria Using a Novel Native Secretion Signal

Novel interventions are needed to prevent the transmission of the Plasmodium parasites that cause malaria. One possible method is to supply mosquitoes with antiplasmodial effector proteins from bacteria by paratransgenesis. Mosquitoes have a diverse complement of midgut microbiota including the Gram-negative bacteria Asaia bogorensis. This study presents the first use of Asaia sp. bacteria for paratransgenesis against P. berghei. We identified putative secreted proteins from A. bogorensis by a genetic screen using alkaline phosphatase gene fusions. Two were secreted efficiently: a siderophore receptor protein and a YVTN beta-propeller repeat protein. The siderophore receptor gene was fused with antiplasmodial effector genes including the scorpine antimicrobial peptide and an anti-Pbs21 scFv-Shiva1 immunotoxin. Asaia SF2.1 secreting these fusion proteins were fed to mosquitoes and challenged with Plasmodium berghei-infected blood. With each of these effector constructs, significant inhibition of parasite development was observed. These results provide a novel and promising intervention against malaria transmission.

Lactic acid bacteria: reviewing the potential of a promising delivery live vector for biomedical purposes

Lactic acid bacteria (LAB) have a long history of safe exploitation by humans, being used for centuries in food production and preservation and as probiotic agents to promote human health. Interestingly, some species of these Gram-positive bacteria, which are generally recognized as safe organisms by the US Food and Drug Administration (FDA), are able to survive through the gastrointestinal tract (GIT), being capable to reach and colonize the intestine, where they play an important role. Besides, during the last decades, an important effort has been done for the development of tools to use LAB as microbial cell factories for the production of proteins of interest. Given the need to develop effective strategies for the delivery of prophylactic and therapeutic molecules, LAB have appeared as an appealing option for the oral, intranasal and vaginal delivery of such molecules. So far, these genetically modified organisms have been successfully used as vehicles for delivering functional proteins to mucosal tissues in the treatment of many different pathologies including GIT related pathologies, diabetes, cancer and viral infections, among others. Interestingly, the administration of such microorganisms would suppose a significant decrease in the production cost of the treatments agents since being live organisms, such vectors would be able to autonomously amplify and produce and deliver the protein of interest. In this context, this review aims to provide an overview of the use of LAB engineered as a promising alternative as well as a safety delivery platform of recombinant proteins for the treatment of a wide range of diseases.

Designer probiotics: Development and applications in gastrointestinal health

Given the increasing commercial and clinical relevance of probiotics, improving their stress tolerance profile and ability to overcome the physiochemical defences of the host is an important biological goal. Herein, I review the current state of the art in the design of engineered probiotic cultures, with a specific focus on their utility as therapeutics for the developing world; from the treatment of chronic and acute enteric infections, and their associated diarrhoeal complexes, to targeting HIV and application as novel mucosal vaccine delivery vehicles.

Protein and oligonucleotide delivery systems for vaginal microbicides against viral STIs

Intravaginal delivery offers an effective option for localized, targeted, and potent microbicide delivery. However, an understanding of the physiological factors that impact intravaginal delivery must be considered to develop the next generation of microbicides. In this review, a comprehensive discussion of the opportunities and challenges of intravaginal delivery are highlighted, in the context of the intravaginal environment and currently utilized dosage forms. After a subsequent discussion of the stages of microbicide development, the intravaginal delivery of proteins and oligonucleotides is addressed, with specific application to HSV and HIV. Future directions may include the integration of more targeted delivery modalities to virus and host cells, in addition to the use of biological agents to affect specific genes and proteins involved in infection. More versatile and multipurpose solutions are envisioned that integrate new biologicals and materials into potentially synergistic combinations to achieve these goals.

Lactobacilli inactivate Chlamydia trachomatis through lactic acid but not H2O2

Lactobacillus species dominate the microbiome in the lower genital tract of most reproductive-age women. Producing lactic acid and H2O2, lactobacilli are believed to play an important role in prevention of colonization by and growth of pathogens. However, to date, there have been no reported studies characterizing how lactobacilli interact with Chlamydia trachomatis, a leading sexually transmitted bacterium. In this report, we demonstrate inactivation of C. trachomatis infectivity by culture media conditioned by Lactobacillus crispatus, L. gasseri and L. jensenii, known to be dominating organisms in the human vaginal microbiome. Lactobacillus still cultures produced lactic acid, leading to time- and concentration-dependent killing of C. trachomatis. Neutralization of the acidic media completely reversed chlamydia killing. Addition of lactic acid into Lactobacillus-unconditioned growth medium recapitulated the chlamydiacidal activity of conditioned media. The H2O2 concentrations in the still cultures were found to be comparable to those reported for the cervicovaginal fluid, but insufficient to inactivate chlamydiae. Aeration of Lactobacillus cultures by shaking markedly induced H2O2 production, but strongly inhibited Lactobacillus growth and lactic acid production, and thus severely affected acidification, leading to significantly reduced chlamydiacidal efficiency. These observations indicate lactobacilli inactivate chlamydiae primarily through maintaining acidity in a relatively hypoxic environment in the vaginal lumen with limited H2O2, which is consistent with the notion that women with higher vaginal pH are more prone to sexually transmitted C. trachomatis infection. In addition to lactic acid, formic acid and acetic acid also exhibited potent chlamydiacidal activities. Taken together, our findings imply that lowering the vaginal pH through engineering of the vaginal microbiome and other means will make women less susceptible to C. trachomatis infection.

Coexpression and secretion of endoglucanase and phytase genes in Lactobacillus reuteri

A multifunctional transgenic Lactobacillus with probiotic characteristics and an ability to degrade β-glucan and phytic acid (phytate) was engineered to improve nutrient utilization, increase production performance and decrease digestive diseases in broiler chickens. The Bacillus subtilis WL001 endoglucanase gene (celW) and Aspergillus fumigatus WL002 phytase gene (phyW) mature peptide (phyWM) were cloned into an expression vector with the lactate dehydrogenase promoter of Lactobacillus casei and the secretion signal peptide of the Lactococcus lactisusp45 gene. This construct was then transformed into Lactobacillus reuteri XC1 that had been isolated from the gastrointestinal tract of broilers. Heterologous enzyme production and feed effectiveness of this genetically modified L. reuteri strain were investigated and evaluated. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed that the molecular mass of phyWM and celW was approximately 48.2 and 55 kDa, respectively, consistent with their predicted molecular weights. Endoglucanase and phytase activities in the extracellular fraction of the transformed L. reuteri culture were 0.68 and 0.42 U/mL, respectively. Transformed L. reuteri improved the feed conversion ratio of broilers from 21 to 42 days of age and over the whole feeding period. However, there was no effect on body weight gain and feed intake of chicks. Transformed L. reuteri supplementation improved levels of ash, calcium and phosphorus in tibiae at day 21 and of phosphorus at day 42. In addition, populations of Escherichia coli, Veillonella spp. and Bacteroides vulgatus were decreased, while populations of Bifidobacterium genus and Lactobacillus spp. were increased in the cecum at day 21.

Vaginal microbiota and its role in HIV transmission and infection

The urogenital tract appears to be the only niche of the human body that shows clear differences in microbiota between men and women. The female reproductive tract has special features in terms of immunological organization, an epithelial barrier, microbiota, and influence by sex hormones such as estrogen. While the upper genital tract is regarded as free of microorganisms, the vagina is colonized by bacteria dominated by Lactobacillus species, although their numbers vary considerably during life. Bacterial vaginosis is a common pathology characterized by dysbiosis, which increases the susceptibility for HIV infection and transmission. On the other hand, HIV infections are often characterized by a disturbed vaginal microbiota. The endogenous vaginal microbiota may protect against HIV by direct production of antiviral compounds, through blocking of adhesion and transmission by ligands such as lectins, and/or by stimulation of immune responses. The potential role of probiotics in the prevention of HIV infections and associated symptoms, by introducing them to the vaginal and gastrointestinal tract (GIT), is also discussed. Of note, the GIT is a site of considerable HIV replication and CD4(+) T-cell destruction, resulting in both local and systemic inflammation. Finally, genetically engineered lactobacilli show promise as new microbicidal agents against HIV.

Sustained delivery of commensal bacteria from pod-intravaginal rings

Topical administration of live commensal bacteria to the vaginal tract holds significant potential as a cost-effective strategy for the treatment of sexually transmitted infections and the delivery of mucosal vaccines. Probiotic-releasing intravaginal rings (IVRs) embody significant theoretical advantages over traditional daily-dosage forms, such as sustained and controlled delivery leading to improved adherence to therapy compared to that of frequent dosing. The conventional IVR designs, however, are not amenable to the delivery of live bacteria. We have developed a novel pod-IVR technology where polymer-coated tablets ("pods") of Lactobacillus gasseri strain ATCC 33323, a commensal microorganism of human origin, are embedded in silicone IVRs. The release rate of bacterial cells is controlled by the diameter of a delivery channel that exposes a portion of the pod to external fluids. In vitro studies demonstrated that the prototype devices released between 1.1×10(7) and 14×10(7) cells per day for up to 21 days in a controlled sustained fashion with stable burst-free release kinetics. The daily release rates were correlated with the cross-sectional area of the delivery channel. Bacteria in the IVR pods remained viable throughout the in vitro studies and formed biofilms on the surfaces of the devices. This proof-of-principle study represents the first demonstration of a prolonged, sustained release of bacteria from an intravaginal device and warrants further investigation of this device as a nonchemotherapeutic agent for the restoration and maintenance of normal urogenital flora.

Pushing the Bacterial Envelope

Over the past three decades, a powerful array of techniques has been developed for expressing heterologous proteins and saccharides on the surface of bacteria. Surface-engineered bacteria, in turn, have proven useful in a variety of settings, including high-throughput screening, biofuel production, and vaccinology. In this chapter, we provide a comprehensive review of methods for displaying polypeptides and sugars on the bacterial cell surface, and discuss the many innovative applications these methods have found to date. While already an important biotechnological tool, we believe bacterial surface display may be further improved through integration with emerging methodology in other fields, such as protein engineering and synthetic chemistry. Ultimately, we envision bacterial display becoming a multidisciplinary platform with the potential to transform basic and applied research in bacteriology, biotechnology, and biomedicine.

Molecular dialogue between the human gut microbiota and the host: a Lactobacillus and Bifidobacterium perspective

The human gut represents a highly complex ecosystem, which is densely colonized by a myriad of microorganisms that influence the physiology, immune function and health status of the host. Among the many members of the human gut microbiota, there are microorganisms that have co-evolved with their host and that are believed to exert health-promoting or probiotic effects. Probiotic bacteria isolated from the gut and other environments are commercially exploited, and although there is a growing list of health benefits provided by the consumption of such probiotics, their precise mechanisms of action have essentially remained elusive. Genomics approaches have provided exciting new opportunities for the identification of probiotic effector molecules that elicit specific responses to influence the physiology and immune function of their human host. In this review, we describe the current understanding of the intriguing relationships that exist between the human gut and key members of the gut microbiota such as bifidobacteria and lactobacilli, discussed here as prototypical groups of probiotic microorganisms.

The highly autoaggregative and adhesive phenotype of the vaginal Lactobacillus plantarum strain CMPG5300 is sortase dependent

Lactobacilli are important for the maintenance of a healthy ecosystem in the human vagina. Various mechanisms are postulated but so far are poorly substantiated by molecular studies, such as mutant analysis. Bacterial autoaggregation is an interesting phenomenon that can promote adhesion to host cells and displacement of pathogens. In this study, we report on the identification of a human vaginal isolate, Lactobacillus plantarum strain CMPG5300, which shows high autoaggregative and adhesive capacity. To investigate the importance of sortase-dependent proteins (SDPs) in these phenotypes, a gene deletion mutant was constructed for srtA, the gene encoding the housekeeping sortase that covalently anchors these SDPs to the cell surface. This mutant lost the capacity to autoaggregate, showed a decrease in adhesion to vaginal epithelial cells, and lost biofilm-forming capacity under the conditions tested. These results indicate that the housekeeping sortase SrtA of CMPG5300 is a key determinant of the peculiar surface properties of this vaginal Lactobacillus strain.

Lactobacillus: host-microbe relationships

Lactobacilli are a subdominant component of the human intestinal microbiota that are also found in other body sites, certain foods, and nutrient-rich niches in the free environment. They represent the types of microorganisms that mammalian immune systems have learned not to react to, which is recognized as a potential driving force in the evolution of the human immune system. Co-evolution of lactobacilli and animals provides a rational basis to postulate an association with health benefits. To further complicate a description of their host interactions, lactobacilli may rarely cause opportunistic infections in compromised subjects. In this review, we focus primarily on human-Lactobacillus interactions. We overview the microbiological complexity of this extraordinarily diverse genus, we describe where lactobacilli are found in or on humans, what responses their presence elicits, and what microbial interaction and effector molecules have been identified. The rare cases of Lactobacillus septicaemia are explained in terms of the host impairment required for such an outcome. We discuss possibilities for exploitation of lactobacilli for therapeutic delivery and mucosal vaccination.

Development of an HIV-1 Microbicide Based on Caulobacter crescentus: Blocking Infection by High-Density Display of Virus Entry Inhibitors

The HIV/AIDS pandemic remains an enormous global health concern. Despite effective prevention options, 2.6 million new infections occur annually, with women in developing countries accounting for more than half of these infections. New prevention strategies that can be used by women are urgently needed. Topical microbicides specific for HIV-1 represent a promising prevention strategy. Conceptually, using harmless bacteria to display peptides or proteins capable of blocking entry provides an inexpensive approach to microbicide development. To avoid the potential pitfalls of engineering commensal bacteria, our strategy is to genetically display infection inhibitors on a non-native bacterium and rely on topical application of stabilized bacteria before potential virus exposure. Due to the high density cell-surface display capabilities and the inherent low toxicity of the bacterium, the S-layer mediated protein display capabilities of the non-pathogenic bacterium Caulobacter crescentus has been exploited for this approach. We have demonstrated that C. crescentus displaying MIP1α or CD4 interfered with the virus entry pathway and provided significant protection from HIV-1 pseudovirus representing clade B in a standard single cycle infection assay. Here we have expanded our C. crescentus based microbicide approach with additional and diverse classes of natural and synthetic inhibitors of the HIV-1 entry pathway. All display constructs provided variable but significant protection from HIV-1 infection; some with protection as high as 70%. Further, we describe protection from infection with additional viral clades. These findings indicate the significant potential for engineering C. crescentus to be an effective and readily adaptable HIV-1 microbicide platform.

Genetic approaches to interfere with malaria transmission by vector mosquitoes

Malaria remains one of the most devastating diseases worldwide, causing over 1 million deaths every year. The most vulnerable stages of Plasmodium development in the vector mosquito occur in the midgut lumen, making the midgut a prime target for intervention. Mosquito transgenesis and paratransgenesis are two novel strategies that aim at rendering the vector incapable of sustaining Plasmodium development. Mosquito transgenesis involves direct genetic engineering of the mosquito itself for delivery of anti-Plasmodium effector molecules. Conversely, paratransgenesis involves the genetic modification of mosquito symbionts for expression of anti-pathogen effector molecules. Here we consider both genetic manipulation strategies for rendering mosquitoes refractory to Plasmodium infection, and discuss challenges for the translation of laboratory findings to field applications.

Identification and characterisation of vaginal lactobacilli from South African women

Background

Bacterial vaginosis (BV), which is highly prevalent in the African population, is one of the most common vaginal syndromes affecting women in their reproductive age placing them at increased risk for sexually transmitted diseases including infection by human immunodeficiency virus-1. The vaginal microbiota of a healthy woman is often dominated by the species belonging to the genus Lactobacillus namely L. crispatus, L. gasseri, L. jensenii and L. iners, which have been extensively studied in European populations, albeit less so in South African women. In this study, we have therefore identified the vaginal Lactobacillus species in a group of 40 African women from Soweto, a township on the outskirts of Johannesburg, South Africa.

Methods

Identification was done by cultivating the lactobacilli on Rogosa agar, de Man-Rogosa-Sharpe (MRS) and Blood agar plates with 5% horse blood followed by sequencing of the 16S ribosomal DNA. BV was diagnosed on the basis of Nugent scores. Since some of the previous studies have shown that the lack of vaginal hydrogen peroxide (H₂O₂) producing lactobacilli is associated with bacterial vaginosis, the Lactobacillus isolates were also characterised for their production of H₂O₂.

Results

Cultivable Lactobacillus species were identified in 19 out of 21 women without BV, in three out of five women with intermediate microbiota and in eight out of 14 women with BV. We observed that L. crispatus, L. iners, L. jensenii, L. gasseri and L. vaginalis were the predominant species. The presence of L. crispatus was associated with normal vaginal microbiota (P = 0.024). High level of H₂O₂ producing lactobacilli were more often isolated from women with normal microbiota than from the women with BV, although not to a statistically significant degree (P = 0.064).

Conclusion

The vaginal Lactobacillus species isolated from the cohort of South African women are similar to those identified in European populations. In accordance with the other published studies, L. crispatus is related to a normal vaginal microbiota. Hydrogen peroxide production was not significantly associated to the BV status which could be attributed to the limited number of samples or to other antimicrobial factors that might be involved.

Mucosal Lactobacillus vectored vaccines

Traditional non-gastrointestinal vaccines can prevent effectively the invasion of pathogens; however, these vaccines are less effective against mucosal infections because there is not a sufficient immune response at the mucosa. Most pathogens invade via a mucosal pathway (oral, intranasal, or vaginal). It is widely accepted that Lactobacillus species play a critical role as commensals in the gastrointestinal (GI) tract. Their ability to survive in the digestive tract, their close association with the intestinal epithelium, their immunomodulatory properties and their safety even when consumed in large amounts make lactobacilli attractive candidates for live vehicles for the delivery of immunogens to the intestinal mucosa. The oral or intranasal administration of Lactobacillus-based vaccines is a promising method to control mucosal infection because these vaccines could induce strong humoral and cellular immune responses both in the blood and at mucosal sites.

Homeostatic properties of Lactobacillus jensenii engineered as a live vaginal anti-HIV microbicide

Background

Vaginal probiotics are investigated as a binary strategy for prevention of bacterial vaginosis and HIV. We applied an innovative experimental model using primary and immortalized human cervical and vaginal epithelial cells to assess the functional properties of Lactobacillus jensenii, a predominant constituent of the healthy vaginal microbiome, engineered to express the HIV-1 entry inhibitor modified cyanovirin-N (mCV-N). In this model bacteria colonize the epithelial cells over a period of 24-72 h. Staurosporine and the Toll-like receptor 2/6 ligand macrophage-activating lipopeptide-2 (MALP-2) serve as positive controls for apoptosis and proinflammatory activation, respectively. In 24-hour intervals, the colonized epithelium is assessed microscopically, supernatants are collected for measurement of soluble immunoinflammatory mediators and production of CV-N, and cells are lysed for assessment of: 1) apoptosis by cleaved versus total caspase-3 assay; 2) NF-κB activation by a luciferase reporter assay; or 3) epithelia-associated colony forming units (CFU) in Brucella agar.

Results

Wild type (WT) L. jensenii 1153 consistently colonized cervical and vaginal cells in the absence of epithelial damage and apoptosis. The bioengineered derivatives expressing mCV-N or control plasmids showed the same stable colonization pattern, which was reproducible between technologists and bacterial batches (CFU coefficient of variation <10% within and between experiments and epithelial cell types). MALP-2 activated NF-κB and caused fold-increased levels of proinflammatory mediators with clinically established significance in the cervicovaginal environment (IL-1α, IL-1β, IL-6, TNF-α, IL-8, RANTES, MIP-3α, and ICAM-1), measured by a multiplex electrochemiluminescence assay. At the same time levels of protective anti-inflammatory mediators interleukin 1 receptor antagonist (IL-1RA) and secretory leukocyte protease inhibitor (SLPI), both measured by ELISA, remained constant (IL-1RA) or moderately increased (SLPI). Similarly to MALP-2, colonization by L. jensenii WT activated NF-κB; however, unlike the synthetic TLR2/6 ligand, the live microorganisms did not induce significant changes in the secreted levels across all inflammation-associated proteins. The mCV-N production and function were confirmed by western blot and a HIV-1 gp120 binding assay, respectively. The bioengineered lactobacilli expressed mCV-N with anti-HIV activity preserved in the epithelial cell context and caused no significant immunoinflammatory changes as compared to the WT L. jensenii.

Conclusions

These results highlight the translational value of the colonization model and justify further clinical investigation of the homeostatic and anti-HIV effectiveness of the L. jensenii derivates.

Microbicides: a new hope for HIV prevention

Human immunodeficiency virus (HIV), causative agent of acquired immunodeficiency syndrome (AIDS), is a global health concern. To control its transmission, safe sex has been proposed as one of the strategies. Microbicides- intravaginal/intrarectal topical formulations of anti-HIV agents have also been proposed to prevent HIV transmission. Microbicides would provide protection by directly inactivating HIV or preventing the attachment, entry or replication of HIV in susceptible target cells as well as their dissemination from target cells present in semen or the host cells lining the vaginal/rectal wall to other migratory cells. Microbicides must be safe, effective following vaginal or rectal administration, and should cause minimal or no genital symptoms or inflammations following long-term repeated usage. However, a safe and efficacious anti-HIV microbicide is not yet available despite the fact that more than 60 candidate agents have been identified to have in vitro activity against HIV, several of which have advanced to clinical testing. Nonetheless, proof-of-concept of microbicides has been established based on the results of recent CAPRISA 004 clinical trials. In this article, the trends and challenges in the development of effective and safe microbicides to combat HIV transmission are reviewed.

Advances in HIV microbicide development

There is an urgent need control the spread of the global HIV pandemic. A microbicide, or topical drug applied to the mucosal environment to block transmission, is a promising HIV prevention strategy. The development of a safe and efficacious microbicide requires a thorough understanding of the mucosal environment and its role in HIV transmission. Knowledge of the key events in viral infection identifies points at which the virus might be most effectively targeted by a microbicide. The cervicovaginal and rectal mucosa play an important role in the innate defense against HIV, and microbicides must not interfere with these functions. In this review, we discuss the current research on HIV microbicide development.

Probiogenomics as a tool to obtain genetic insights into adaptation of probiotic bacteria to the human gut

Bifidobacteria and lactobacilli are widely exploited as health-promoting bacteria in many functional foods. However, the molecular mechanisms as to how these bacteria positively impact on host health are far from completely understood. For this reason these microorganisms represent a growing area of interest with respect to their genomics, molecular biology and genetics. Recent genome sequencing of a large number of strains of bifidobacteria and lactobacilli has allowed access to the complete genetic makeup of representative members of these bacteria. Here, we will discuss how the analysis of genomic data has helped us to understand the mechanisms by which these bacteria adapt to the specific environment of the gastrointestinal tract, while also revealing genetic functions that mediate specific host-microbe interactions.

Mucosal vaccination and therapy with genetically modified lactic acid bacteria

Lactic acid bacteria (LAB) have proved to be effective mucosal delivery vehicles that overcome the problem of delivering functional proteins to the mucosal tissues. By the intranasal route, both live and killed LAB vaccine strains have been shown to elicit mucosal and systemic immune responses that afford protection against infectious challenges. To be effective via oral administration, frequent dosing over several weeks is required but new targeting and adjuvant strategies have clearly demonstrated the potential to increase the immunogenicity and protective immunity of LAB vaccines. Oral administration of Lactococcus lactis has been shown to induce antigen-specific oral tolerance (OT) to secreted recombinant antigens. LAB delivery is more efficient at inducing OT than the purified antigen, thus avoiding the need for purification of large quantities of antigen. This approach holds promise for new therapeutic interventions in allergies and antigen-induced autoimmune diseases. Several clinical and research reports demonstrate considerable progress in the application of genetically modified L. lactis for the treatment of inflammatory bowel disease (IBD). New medical targets are on the horizon, and the approval by several health authorities and biosafety committees of a containment system for a genetically modified L. lactis that secretes Il-10 should pave the way for new LAB delivery applications in the future.

Incorporation of the HIV-1 microbicide cyanovirin-N in a food product

An urgent need exists for HIV-1 microbicides. Here, we describe the in vivo testing of lactic acid bacteria bioengineered to secrete cyanovirin-N. We fed pigtail macaques a yogurt formulation that used bioengineered strains as a starter culture. Cyanovirin-N expression could be detected in the rectal vault during and immediately after feeding. Ex vivo viral challenge of rectal tissue biopsies revealed that peak viral burden was significantly lower in tissue obtained from experimental animals compared with control animals. Formulation of candidate compounds in lactic acid bacteria and their oral administration seems to be a feasible strategy for mucosal delivery of microbicides.

Prevention of vaginal SHIV transmission in macaques by a live recombinant Lactobacillus

Most human immunodeficiency virus (HIV) transmissions in women occur through the cervicovaginal mucosa, which is coated by a bacterial biofilm including Lactobacillus. This commensal bacterium has a role in maintaining a healthy mucosa and can be genetically engineered to produce antiviral peptides. Here, we report a 63% reduction in transmission of a chimeric simian/HIV (SHIV(SF162P3)) after repeated vaginal challenges of macaques treated with Lactobacillus jensenii expressing the HIV-1 entry inhibitor cyanovirin-N. Furthermore, peak viral loads in colonized macaques with breakthrough infection were reduced sixfold. Colonization and prolonged antiviral protein secretion by the genetically engineered lactobacilli did not cause any increase in proinflammatory markers. These findings lay the foundation for an accessible and durable approach to reduce heterosexual transmission of HIV in women, which is coitally independent, inexpensive, and enhances the natural protective effects of the vaginal microflora.

Enhanced neutralization of HIV by antibodies displayed on the S-layer of Caulobacter crescentus

Innovative methods of prevention are needed to stop the more than two million new HIV-1 infections annually, particularly in women. Local application of anti-HIV antibodies has been shown to be effective at preventing infection in nonhuman primates; however, the concentrations needed are cost prohibitive. Display of antibodies on a particulate platform will likely prolong effectiveness of these anti-HIV agents and lower the cost of goods. Here, we demonstrate that the bacterium Caulobacter crescentus and its highly expressed surface-layer (S-layer) protein can provide this antibody display platform. Caulobacters displaying protein G, alone or with CD4 codisplay, successfully captured HIV-1-specific antibodies and demonstrated functional neutralization. Compared to soluble antibodies, a neutralizing anti-HIV antibody displayed on Caulobacter was as effective or more effective at neutralizing diverse HIV-1 isolates. Moreover, when an antibody reactive with an epitope induced by CD4 binding (CD4i) was codisplayed with CD4, there was significant enhancement in HIV-1 neutralization. These results suggest that caulobacters displaying anti-HIV antibodies offer a distinct improvement in the use of antibodies as microbicides. Furthermore, these reagents can specifically evaluate anti-HIV antibodies in concert with other HIV-1 blocking agents to assess the most suitable tools for conversion to scFvs, allowing for direct display within the S-layer protein and further reducing cost of goods. In summary, C. crescentus, which can be easily produced and chemically stabilized at low cost, is well suited for engineering as an effective platform, offering an inexpensive way to produce and deliver HIV-1-specific microbicides.

Secretion of anti-Plasmodium effector proteins from a natural Pantoea agglomerans isolate by using PelB and HlyA secretion signals

The insect-vectored disease malaria is a major world health problem. New control strategies are needed to supplement the current use of insecticides and medications. A genetic approach can be used to inhibit development of malaria parasites (Plasmodium spp.) in the mosquito host. We hypothesized that Pantoea agglomerans, a bacterial symbiont of Anopheles mosquitoes, could be engineered to express and secrete anti-Plasmodium effector proteins, a strategy termed paratransgenesis. To this end, plasmids that include the pelB or hlyA secretion signals from the genes of related species (pectate lyase from Erwinia carotovora and hemolysin A from Escherichia coli, respectively) were created and tested for their efficacy in secreting known anti-Plasmodium effector proteins (SM1, anti-Pbs21, and PLA2) in P. agglomerans and E. coli. P. agglomerans successfully secreted HlyA fusions of anti-Pbs21 and PLA2, and these strains are under evaluation for anti-Plasmodium activity in infected mosquitoes. Varied expression and/or secretion of the effector proteins was observed, suggesting that the individual characteristics of a particular effector may require empirical testing of several secretion signals. Importantly, those strains that secreted efficiently grew as well as wild-type strains under laboratory conditions and, thus, may be expected to be competitive with the native microbiota in the environment of the mosquito midgut.

Lactococcus lactis as a live vector: heterologous protein production and DNA delivery systems

Lactic acid bacteria (LAB), widely used in the food industry, are present in the intestine of most animals, including humans. The potential use of these bacteria as mucosal delivery vehicles for vaccinal, medical or technological use has been extensively investigated. Lactococcus lactis, a LAB species, is a potential candidate for the production of biologically useful proteins and for plasmid DNA delivery to eukaryotic cells. Several delivery systems have been developed to target heterologous proteins to a specific cell location (i.e., cytoplasm, cell wall or extracellular medium) and more recently to efficiently transfer DNA to eukaryotic cells. A promising application of L. lactis is its use for the development of live mucosal vaccines. Here, we have reviewed the expression of heterologous protein and the various delivery systems developed for L. lactis, as well as its use as an oral vaccine carrier.

HIV sexual transmission and microbicides

Pathogens often rely on the contacts between hosts for transmission. Most viruses have adapted their transmission mechanisms to defined behaviours of their host(s) and have learned to exploit these for their own propagation. Some viruses, such as HIV, the human papillomavirus (HPV), HSV-2 and HCV, cause sexually transmitted infections (STIs). Understanding the transmission of particular viral variants and comprehending the early adaptation and evolution is fundamental to eventually inhibiting sexual transmission of HIV. Here, we review the current understanding of the mechanisms of sexual transmission and the biology of the transmitted HIV. Next, we present a timely overview of candidate microbicides, including past, ongoing and future clinical trials of HIV topical microbicides.