Approaches to new vaccines

Structural Modifications and Strategies for Native Starch for Applications in Advanced Drug Delivery

Pharmaceutical excipients are compounds or substances other than API which are added to a dosage form, these excipients basically act as carriers, binders, bulk forming agents, colorants, and flavouring agents, and few excipients are even used to enhance the activity of active pharmaceutical ingredient (API) and various more properties. However, despite of these properties, there are problems with the synthetic excipients such as the possibility of causing toxicity, inflammation, autoimmune responses, lack of intrinsic bioactivity and biocompatibility, expensive procedures for synthesis, and water solubility. However, starch as an excipient can overcome all these problems in one go. It is inexpensive, there is no toxicity or immune response, and it is biocompatible in nature. It is very less used as an excipient because of its high digestibility and swelling index, high glycemic index, paste clarity, film-forming property, crystalline properties, etc. All these properties of starch can be altered by a few modification processes such as physical modification, genetic modification, and chemical modification, which can be used to reduce its digestibility and glycemic index of starch, improve its film-forming properties, and increase its paste clarity. Changes in some of the molecular bonds which improve its properties such as binding, crystalline structure, and retrogradation make starch perfect to be used as a pharmaceutical excipient. This research work provides the structural modifications of native starch which can be applicable in advanced drug delivery. The major contributions of the paper are advances in the modification of native starch molecules such as physically, chemically, enzymatically, and genetically traditional crop modification to yield a novel molecule with significant potential for use in the pharmaceutical industry for targeted drug delivery systems.

DNA vaccines targeting heavy chain C-terminal fragments of Clostridium botulinum neurotoxin serotypes A, B, and E induce potent humoral and cellular immunity and provide protection from lethal toxin challenge

Botulinum neurotoxins (BoNTs) are deadly, toxic proteins produced by the bacterium Clostridium botulinum that can cause significant diseases in humans. The use of the toxic substances as potential bioweapons has raised concerns by the Centers for Disease Control and Prevention and the United States Military. Currently, there is no licensed vaccine to prevent botulinum intoxication. Here we present an immunogenicity study to evaluate the efficacy of novel monovalent vaccines and a trivalent cocktail DNA vaccine targeting the heavy chain C-terminal fragments of Clostridium botulinum neurotoxin serotypes A, B, and E. These synthetic DNA vaccines induced robust humoral and polyfunctional CD4(+) T-cell responses which fully protected animals against lethal challenge after just 2 immunizations. In addition, naïve animals administered immunized sera mixed with the lethal neurotoxin were 100% protected against intoxication. The data demonstrate the protective efficacy induced by a combinative synthetic DNA vaccine approach. This study has importance for the development of vaccines that provide protective immunity against C. botulinum neurotoxins and other toxins.

Archaeosomes as Self-adjuvanting Delivery Systems for Cancer Vaccines*

Archaeal ether glycerolipid vesicles (archaeosomes) efficiently deliver exogenous antigen for induction of humoral and cell-mediated immunity. Because induction of CD8 cytotoxic T cells is critical for protective vaccination against tumors, we compared the ability of various archaeosome lipid compositions to evoke a strong CD8 CTL response to entrapped antigen. Subcutaneous immunization of mice with ovalbumin (OVA) entrapped in all archaeosome lipid compositions evoked a primary (day 10) splenic CTL response indicating processing for MHC class I presentation. Interestingly, several polar lipid compositions from halophilic archaea were very potent to adjuvant this early CTL response. Despite this, the lytic units reduced substantially by weeks 6-7. More importantly, at >50 weeks, only Methanobrevibacter smithii and Thermoplasma acidophilum both rich in bipolar membrane-spanning caldarchaeols, demonstrated recall memory CTLs. Immunization of mice with OVA entrapped in M. smithii, Halobacterium salinarum or T. acidophilum vesicles provided prophylactic protection against challenge with OVA-expressing solid tumors at 6 weeks. Even a dose of 3 microg OVA in archaeosomes significantly delayed tumor growth. Tumor protection was also noted in a therapeutic design wherein OVA-archaeosomes were injected concurrent with the tumor challenge. Interestingly, antigen-free T. acidophilum but not antigen-free H. salinarum archaeosomes provided innate therapeutic protection. Vaccination with a CTL peptide epitope from the melanoma differentiation antigen, tyrosinase-related protein 2, in archaeosomes induced a protective CD8 response against B16OVA metastasis, indicating potential for targeting self, tumor antigens. Thus, lipid structural properties of archaea may differentially modulate primary, long-term and/or innate immunity, impacting adjuvant choice for vaccine design.

Biopharmaceuticals derived from genetically modified plants

Modern biotechnology has resulted in a resurgence of interest in the production of new therapeutic agents using botanical sources. With nearly 500 biotechnology products approved or in development globally, and with production capacity limited, the need for efficient means of therapeutic protein production is apparent. Through genetic engineering, plants can now be used to produce pharmacologically active proteins, including mammalian antibodies, blood product substitutes, vaccines, hormones, cytokines, and a variety of other therapeutic agents. Efficient biopharmaceutical production in plants involves the proper selection of host plant and gene expression system, including a decision as to whether a food crop or a non-food crop is more appropriate. Product safety issues relevant to patients, pharmaceutical workers, and the general public must be addressed, and proper regulation and regulatory oversight must be in place prior to commercial plant-based biopharmaceutical production. Plant production of pharmaceuticals holds great potential, and may become an important production system for a variety of new biopharmaceutical products.

Plant cell cultures: Chemical factories of secondary metabolites

This review deals with the production of high-value secondary metabolites including pharmaceuticals and food additives through plant cell cultures, shoot cultures, root cultures and transgenic roots obtained through biotechnological means. Plant cell and transgenic hairy root cultures are promising potential alternative sources for the production of high-value secondary metabolites of industrial importance. Recent developments in transgenic research have opened up the possibility of the metabolic engineering of biosynthetic pathways to produce high-value secondary metabolites. The production of the pungent food additive capsaicin, the natural colour anthocyanin and the natural flavour vanillin is described in detail.

Dendritic cells engineered to express the Flt3 ligand stimulate type I immune response, and induce enhanced cytoxic T and natural killer cell cytotoxicities and antitumor immunity

BACKGROUND

Tumor antigen presentation by dendritic cells (DCs) to T cells in lymphoid organs is crucial for induction of antitumor immune responses. Fms-like tyrosine kinase 3 ligand (Flt3L) is a regulator of hematopoietic cell development.

METHODS

To investigate the potential effect of Flt3L transgene expression on DC-based cancer vaccines, we constructed a recombinant adenovirus AdVFlt3L expressing Flt3L, transfected DCs with AdVFlt3L, and investigated the efficacy of antitumor immunity by vaccination of DC(Flt3L) engineered to express Flt3L transgene.

RESULTS

Our data demonstrated that AdVFlt3L transfection up-regulated the expression of cytokine IL-1beta and chemokines MIP-1alpha, MIP-1beta, IP-10, MCP-1 and MIP-2, and stimulated DC(Flt3L) cell proliferation in vitro and migration toward regional lymph nodes in vivo. Our data also demonstrated that vaccination of Mut1-pulsed DC(Flt3L) cells was able to stimulate (i). a type 1 immune response comprising CD4(+) Th1 and CD8(+) Tc1 activation and (ii). around 2- and 3-fold enhanced tumor-specific cytotoxic T lymphocyte (CTL) and non-specific NK responses (p < 0.05) than vaccination with similarly pulsed control virus-transfected and untransfected DCs, respectively. More importantly, vaccination of Mut1-pulsed DC(Flt3L) cells induced enhanced antitumor immunity in vivo, even against poorly immunogenic 3LL tumor cells. Vaccinations of Mut1-pulsed DCs, DC(pLpA) and DC(Flt3L) all protected mice from challenge of low dose (0.5 x 10(5)) tumor cells. However, only vaccination of the last one was able to protect 63% (6/8) mice from challenge of high dose (3 x 10(5)) 3LL tumor cells (p < 0.01).

CONCLUSIONS

DCs engineered to secrete Flt3L may offer a new strategy in DC-based cancer vaccines.

Measuring Gene Flow in the Cultivation of Transgenic Barley

Genetic engineering is becoming a useful tool in the improvement of plants and plant-based raw materials. Varieties with value-added traits are developed for nonfood use in industrial and medical production, and different production lines must be kept separate. For good management practices, knowledge of relevant gene flow parameters is required. In the present study, pollen-mediated dispersal of transgenes via cross-fertilization was examined. A transgenic barley (Hordeum vulgare L.) line carrying a marker gene coding for neomycin phosphotransferase II (nptII) was used as a pollen donor. For maximum resolution, a cytoplasmically male-sterile barley line was utilized as recipient and the flow of nptII transgene was monitored at distances of 1, 2, 3, 6, 12, 25, 50, and 100 m from the donor plots of 225 and 2000 m(2). Male-fertile plots at a distance of 1 m were included to measure the transgene flow in normal barley. The number of seeds obtained from male-sterile heads diminished rapidly with distance and only a few seeds were found at distances of 50 and 100 m. Molecular genetic analysis (polymerase chain reaction-PCR) revealed that all seeds obtained from male-sterile heads at a distance of 1 m were transgenic, as anticipated. However, only 3% of the distant seeds (50 m) actually carried the transgene, whereas most of them resulted from fertilization with nontransgenic background pollen. This background pollen was mainly due to pollen leakage in some male-sterile heads. In normal male-fertile barley, the cross-fertilization frequency with transgenic pollen varied from 0 to 7% at a distance of 1 m, depending on weather conditions on the heading day. We conclude that, because of competing self-produced and nontransgenic background pollen, the possibility of cross-pollination is very low between a transgenic barley field and an adjacent field cultivated with normal barley. However, adequate isolation distances and best management practices are needed for cultivation of transgenic barley.

New technology for improved vaccine safety and efficacy

Nearly all of the 2000 vaccines presently licensed by the US Department of Agriculture for veterinary use in the United States are conventional vaccines containing either killed or modified live whole bacteria or viruses. Recent advances in molecular biology, immunology, microbiology, and genetics and in understanding microbial pathogenesis have led to the development of a wide variety of new approaches for developing safer and more effective vaccines. This article briefly describes these new technologies and their potential advantages and disadvantages as compared with conventional killed and modified live vaccines.

Intranasal vaccination against plague, tetanus and diphtheria

Plague is an extremely virulent and potentially lethal infection caused by the bacterium Y. pestis. The current vaccine used to immunise against plague often fails to engender solid (100%) protection against inhalational infection with Y. pestis. Similarly, logistical factors favour the development of non-parenteral immunisation protocols to counter plague. Recently an improved parenteral vaccination strategy for plague, based on the recombinant subunit approach, has entered clinical trails. The Yersinia pestis subunit antigens (F1 and V) have been successfully incorporated into novel vaccine delivery systems such as biodegradable microspheres composed of poly-L-(lactide) (PLLA). Intranasal and intratracheal administration of PLLA microencapsulated F1 and V serves to protect experimental animals from inhalational and subcutaneous challenge with virulent Y. pestis bacilli. Liposomes have also been used to improve the immunogenicity of intranasally administered Y. pestis antigens, and the effectiveness of this approach to plague immunisation has been evaluated. Tetanus and diphtheria still cause many deaths worldwide. The maintenance of protective immunity to diphtheria and tetanus requires booster injections of the currently licensed toxoid vaccines. Consequently, many people remain unprotected. Improved coverage may well result from the development of effective non-invasive vaccines that could be readily distributed and potentially self-administered. To this end, the intranasal and inhalational routes of administration have been extensively investigated. Tetanus and diphtheria toxoids have been delivered intranasally to experimental animals using a wide variety of adjuvants (enterotoxin derivatives), penetration enhancers (cyclodextrins, bile salts, surfactants, cationic polymers) and delivery systems (microspheres and liposomes). As compared with parenteral vaccination, nasal immunisation has been shown favourably effective in small animal models, and a limited number of early phase clinical trails. As a caveat to this, adjuvantisation of toxoid/subunit molecules appears to be a requisite for elicitation of appreciable immunological responses, following nasal administration of acellular immunogens. Testing in larger animal models and humans is needed to ascertain if the promising results obtained in rodents can be reciprocated without compromising safety.

Impaired gamma interferon responses against parvovirus B19 by recently infected children

Parvovirus B19 is the causative agent of "fifth disease" of childhood. It has been implicated in a variety of conditions, including unsuccessful pregnancy and rheumatoid arthritis, and is a potential contaminant of blood products. There has been little study of immunity to parvovirus B19, and the exact nature of the protective humoral and cell-mediated immune response is unclear. Immune responses to purified virus capsid proteins, VP1 and VP2, were examined from a cohort of recently infected children and compared with responses from long-term convalescent volunteers. The results demonstrate that antibody reactivity is primarily maintained against conformational epitopes in VP1 and VP2. The unique region of VP1 appears to be a major target for cell-mediated immune responses, particularly in recently infected individuals. We confirm that antibody reactivity against linear epitopes of VP2 is lost shortly after infection but find no evidence of the proposed phenotypic switch in either the subclass of parvovirus B19-specific antibody or the pattern of cytokine production by antigen-specific T cells. The dominant subclass of specific antibody detected from both children and adults was immunoglobulin G1. No evidence was found for interleukin 4 (IL-4) or IL-5 production by isolated lymphocytes from children or adults. In contrast, lymphocytes from convalescent adults produced a typical type 1 response associated with high levels of IL-2 and gamma interferon (IFN-gamma). However, we observed a significant (P<0.001) deficit in the production of IFN-gamma in response to VP1 or VP2 from lymphocytes isolated from children. Taken together, these results imply that future parvovirus B19 vaccines designed for children will require the use of conformationally preserved capsid proteins incorporating Th1 driving adjuvants. Furthermore, these data suggest novel mechanisms whereby parvovirus B19 infection may contribute to rheumatoid arthritis and unsuccessful pregnancy.