New approaches to improve a peptide vaccine against porcine Taenia solium cysticercosis

Sexual Dimorphism of the Neuroimmunoendocrine Response in the Spleen during a Helminth Infection: A New Role for an Old Player?

The interaction of the nervous, immune, and endocrine systems is crucial in maintaining homeostasis in vertebrates, and vital in mammals. The spleen is a key organ that regulates the neuroimmunoendocrine system. The Taenia crassiceps mouse system is an excellent experimental model to study the complex host–parasite relationship, particularly sex-associated susceptibility to infection. The present study aimed to determine the changes in neurotransmitters, cytokines, sex steroids, and sex-steroid receptors in the spleen of cysticercus-infected male and female mice and whole parasite counts. We found that parasite load was higher in females in comparison to male mice. The levels of the neurotransmitter epinephrine were significantly decreased in infected male animals. The expression of IL-2 and IL-4 in the spleen was markedly increased in infected mice; however, the expression of Interleukin (IL)-10 and interferon (IFN)-γ decreased. We also observed sex-associated differences between non-infected and infected mice. Interestingly, the data show that estradiol levels increased in infected males but decreased in females. Our studies provide evidence that infection leads to changes in neuroimmunoendocrine molecules in the spleen, and these changes are dimorphic and impact the establishment, growth, and reproduction of T. crassiceps. Our findings support the critical role of the neuroimmunoendocrine network in determining sex-associated susceptibility to the helminth parasite.

A cross talk between the immunization and edible vaccine: Current challenges and future prospects

INTRODUCTION

It is well known that immune system is highly specific to protect the body against various environmental pathogens. The concept of conventional vaccination has overcome the pandemic situation of several infectious diseases outbreak.

AREA COVERED

The recent idea of immunization through oral route (edible vaccine) is vital alternatives over conventional vaccines. Edible vaccines are composed of antigenic protein introduced into the plant cells which induce these altered plants to produce the encoded protein. Edible vaccine has no way of forming infection and safety is assured as it only composed of antigenic protein and is devoid of pathogenic genes. Edible vaccines have significant role in stimulating mucosal immunity as they come in contact with digestive tract lining. They are safe, cost-effective, easy-to-administer and have reduced manufacturing cost hence have a dramatic impact on health care in developing countries.

EXPERT OPINION

The edible vaccine might be the solution for the potential hazard associated with the parenteral vaccines. In this review we discuss the detailed study of pros, cons, mechanism of immune stimulation, various outbreaks that might be controlled by edible vaccines with the possible future research and applied application of edible vaccine.

Filamentous bacteriophage fd as an antigen delivery system in vaccination

Peptides displayed on the surface of filamentous bacteriophage fd are able to induce humoral as well as cell-mediated immune responses, which makes phage particles an attractive antigen delivery system to design new vaccines. The immune response induced by phage-displayed peptides can be enhanced by targeting phage particles to the professional antigen presenting cells, utilizing a single-chain antibody fragment that binds dendritic cell receptor DEC-205. Here, we review recent advances in the use of filamentous phage fd as a platform for peptide vaccines, with a special focus on the use of phage fd as an antigen delivery platform for peptide vaccines in Alzheimer's Disease and cancer.

Role of transgenic plants in agriculture and biopharming

At present, environmental degradation and the consistently growing population are two main problems on the planet earth. Fulfilling the needs of this growing population is quite difficult from the limited arable land available on the globe. Although there are legal, social and political barriers to the utilization of biotechnology, advances in this field have substantially improved agriculture and human life to a great extent. One of the vital tools of biotechnology is genetic engineering (GE) which is used to modify plants, animals and microorganisms according to desired needs. In fact, genetic engineering facilitates the transfer of desired characteristics into other plants which is not possible through conventional plant breeding. A variety of crops have been engineered for enhanced resistance to a multitude of stresses such as herbicides, insecticides, viruses and a combination of biotic and abiotic stresses in different crops including rice, mustard, maize, potato, tomato, etc. Apart from the use of GE in agriculture, it is being extensively employed to modify the plants for enhanced production of vaccines, hormones, etc. Vaccines against certain diseases are certainly available in the market, but most of them are very costly. Developing countries cannot afford the disease control through such cost-intensive vaccines. Alternatively, efforts are being made to produce edible vaccines which are cheap and have many advantages over the commercialized vaccines. Transgenic plants generated for this purpose are capable of expressing recombinant proteins including viral and bacterial antigens and antibodies. Common food plants like banana, tomato, rice, carrot, etc. have been used to produce vaccines against certain diseases like hepatitis B, cholera, HIV, etc. Thus, the up- and down-regulation of desired genes which are used for the modification of plants have a marked role in the improvement of genetic crops. In this review, we have comprehensively discussed the role of genetic engineering in generating transgenic lines/cultivars of different crops with improved nutrient quality, biofuel production, enhanced production of vaccines and antibodies, increased resistance against insects, herbicides, diseases and abiotic stresses as well as the safety measures for their commercialization.

High-level expression of human interferon alpha-2b in transgenic carrot (Daucus carota L.) plants

In this study, we report the obtaining of carrot plants expressing human interferon alpha-2b via Agrobacterium-mediated transformation using two vector constructs containing the sequence coding for interferon gene fused with Nicotiana plumbagenifolia calreticulin apoplast targeting signal driven by 35S CaMV promoter and root-specific Mll promoter. The human interferon alpha-2b gene was correctly translated in carrot plants according to Western blot analysis. The recombinant protein exhibited antiviral activity in vitro by inhibition of vesicular stomatitis virus replication in established piglet testicular cells. The results demonstrated the higher activity of interferon accumulated in carrot plants for young leaves (up to 50.7 × 10(3) IU/g FW) compared to the mature ones probably due to the degradation-susceptible nature of this protein. The taproot-expressing system could have also provided the sufficient protein amounts (up to 16.5 × 10(3) IU/g FW) and could possibly be used for generating interferon alpha-2b protein in planta for preventing and curing infectious diseases.

Fact or hypothesis: Taenia crassiceps as a model for Taenia solium, and the S3Pvac vaccine

Research undertaken over the past 40 years has established many of the general principals concerning immunity to taeniid cestodes. Although much is well understood about the host-protective mechanisms against taeniids and this knowledge has been exploited in studies on vaccine development, many aspects require further investigation or confirmation. Some phenomena have come to be regarded as being well established, while careful analysis of the published data would suggest that they may be better regarded as hypotheses rather than established facts. This review considers one selected issue pertaining to immunity to cestode infections and examines carefully the nature of the evidence that is available to support conclusions that have been made in this area. The issue examined is the use of Taenia crassiceps as a model for cysticercosis in pigs caused by Taenia solium, together with the S3Pvac vaccine, which has been developed based on this model. Strong evidence is found to support the conclusion that defined T. crassiceps antigens can limit intraperitoneal proliferation of the ORF strain of T. crassiceps in mice; however, the potential for these antigens to affect T. solium infection in pigs requires further confirmation.

Taenia crassiceps: in vivo and in vitro models

Taenia crassiceps is a cestode parasite of wild and domestic animals that rarely affects humans; it has been widely used as an experimental model. The asexual proliferation by budding is a useful attribute of T. crassiceps cysticerci, which allows the various strains to be maintained indefinitely in the peritoneal cavity of inbred mice. Over the last 50 years, experimental results using larval and adult stages of T. crassiceps have yielded much information on the morphology, infectivity, proliferation dynamics, host immune response, endocrinological responses and vaccine research, all of which have contributed to our knowledge of cestode biology.

Plant production of veterinary vaccines and therapeutics

Plant-derived biologicals for use in animal health are becoming an increasingly important target for research into alternative, improved methods for disease control. Although there are no commercial products on the market yet, the development and testing of oral, plant-based vaccines is now beyond the proof-of-principle stage. Vaccines, such as those developed for porcine transmissible gastroenteritis virus, have the potential to stimulate both mucosal and systemic, as well as, lactogenic immunity as has already been seen in target animal trials. Plants are a promising production system, but they must compete with existing vaccines and protein production platforms. In addition, regulatory hurdles will need to be overcome, and industry and public acceptance of the technology are important in establishing successful products.

Plant-based oral vaccines: results of human trials

Vaccines consisting of transgenic plant-derived antigens offer a new strategy for development of safe, inexpensive vaccines. The vaccine antigens can be eaten with the edible part of the plant or purified from plant material. In phase 1 clinical studies of prototype potato- and corn-based vaccines, these vaccines have been safe and immunogenic without the need for a buffer or vehicle other than the plant cell. Transgenic plant technology is attractive for vaccine development because these vaccines are needle-less, stable, and easy to administer. This chapter examines some early human studies of oral transgenic plant-derived vaccines against enterotoxigenic Escherichia coli infection, norovirus, and hepatitis B.

Construction and characterization of a recombinant fowlpox virus containing HIV-1 multi-epitope-p24 chimeric gene in mice

The epidemic of HIV/AIDS is sweeping across the world. It is of great importance to figure out new ways to curb this disease. Epitope-based vaccine is one of these solutions. In this study, a chimeric gene was obtained by combination of a designed HIV-1 multi-epitope gene (MEG) and HIV-1 p24 gene. A recombinant plasmid pUTA2-MEGp24 was then constructed by inserting MEGp24 gene into the downstream of the promoter (ATI-P7.5x20) of fowlpox virus (FPV) transfer vector pUTA2. The recombinant plasmid and wild-type FPV 282E4 strain were then co-transfected into CEF cells and homologous recombination occurred. A recombinant virus expressing HIV-1 protein MEGp24 was screened by genome PCR and Western blot assay. Large scale preparation and purification of the recombinant fowlpox virus (rFPV) were then carried out. BALB/c mice were immunized intramuscularly with the rFPV for three times on day 0, 14 and 42. Mice were executed and sampled one week after the third inoculation. Anti-HIV-1 antibody in serum and Th1 cytokines in the supernatant of cultured spleen cells were assayed by ELISA. The count of T lymphocyte subsets and the CTL activity of spleen lymphocytes were analyzed by flow cytometry and lactate dehydrogenase (LDH) release assay, respectively. The results showed that HIV-1 specific antibody in serum and increased T lymphocyte subsets (CD4(+) T, CD8(+) T) were detected in the immunization group. CTL target-killing activity and higher secretion of Th1 cytokines (IFN-gamma and IL-2) of spleen lymphocytes stimulated by H-2(d)-restricted CTL peptide were observed in immunized mice. We concluded that the rFPV may induce HIV-1 specific immunity especially cellular immunity in mice.

Control of Taenia solium cysticercosis/taeniosis

Cysticercosis is emerging as a serious public health and agricultural problem in many poorer countries of Latin America, Africa, and Asia. Caused by the pork tapeworm, Taenia solium, this zoonotic disease forms larval cysts in humans and pigs that can lead to epilepsy and death in humans, reduces the market value of pigs and makes pork unsafe to eat. It occurs where pigs range freely, sanitation is poor, and meat inspection is absent or inadequate, and is thus strongly associated with poverty and smallholder farming. Although theoretically easy to control and declared eradicable cysticercosis remains neglected in most endemic countries due to lack of information and awareness about the extent of the problem, suitable diagnostic and management capacity, and appropriate prevention and control strategies. Human neurocysticercosis occurs when the larval cysts develop in the brain. It is considered to be the most common parasitic infection of the human nervous system and the most frequent preventable cause of epilepsy in the developing world. Thus far the infection has not been eliminated from any region by a specific program, and no national control programs are yet in place. We consider the tools available for combating cysticercosis and suggest simple packages of interventions, which can be conducted utilizing existing services and structures in the endemic countries to provide appropriate and sustainable control of the disease.

Research Advances on Transgenic Plant Vaccines

In recent years, with the development of genetics molecular biology and plant biotechnology, the vaccination (e.g. genetic engineering subunit vaccine, living vector vaccine, nucleic acid vaccine) programs are taking on a prosperous evolvement. In particular, the technology of the use of transgenic plants to produce human or animal therapeutic vaccines receives increasing attention. Expressing vaccine candidates in vegetables and fruits open up a new avenue for producing oral/edible vaccines. Transgenic plant vaccine disquisitions exhibit a tempting latent exploiting foreground. There are a lot of advantages for transgenic plant vaccines, such as low cost, easiness of storage, and convenient immune-inoculation. Some productions converged in edible tissues, so they can be consumed directly without isolation and purification. Up to now, many transgenic plant vaccine productions have been investigated and developed. In this review, recent advances on plant-derived recombinant protein expression systems, infectious targets, and delivery systems are presented. Some issues of high concern such as biosafety and public health are also discussed. Special attention is given to the prospects and limitations on transgenic plant vaccines.

Brucella spp. lumazine synthase: a novel antigen delivery system

Lumazine synthase from Brucella spp. (BLS) was evaluated as a protein carrier to improve antigen delivery of KETc1, one of the peptides of the anti-cysticercosis vaccine. KETc1 becomes antigenic, preserved its immunogenicity and its protective capacity when expressed as a recombinant chimeric protein using Brucella spp. lumazine synthase. KETc1 and BLS-KETc1 were not MHC H-2(d), H-2(k) nor H-2(b) haplotype-restricted albeit KETc1 is preferentially presented in the H-2(b) haplotype. These findings support that BLS is a potent new delivery system for the improvement of subunit vaccines.

Induction of protection against porcine cysticercosis by vaccination with recombinant oncosphere antigens

Two recombinant Taenia solium oncosphere antigens, designated TSOL18 and TSOL45-1A, were investigated as vaccines to prevent transmission of the zoonotic disease cysticercosis through pigs. Both antigens were effective in inducing very high levels of protection (up to 100%) in three independent vaccine trials in pigs against experimental challenge infection with T. solium eggs, which were undertaken in Mexico and Cameroon. This is the highest level of protection that has been achieved against T. solium infection in pigs by vaccination with a defined antigen. TSOL18 and TSOL45-1A provide the basis for development of a highly effective practical vaccine that could assist in the control and, potentially, the eradication of human neurocysticercosis.

Host gender in parasitic infections of mammals: an evaluation of the female host supremacy paradigm

A review of current literature on mammalian hosts' sexual dimorphism (SD) in parasitic infections revealed that (1) it is a scarcely and superficially studied biological phenomenon of considerable significance for individual health, behavior, and lifestyles and for the evolution of species; (2) there are many notable exceptions to the rule of a favorable female bias in susceptibility to infection; (3) a complex network of molecular and cellular reactions connecting the host's immuno-neuroendocrine systems with those of the parasite is responsible for the host-parasite relationship rather than just an adaptive immune response and sex hormones; (4) a lack of gender-specific immune profiles in response to different infections; (5) the direct effects of the host hormones on parasite physiology may significantly contribute to SD in parasitism; and (6) the need to enrich the reductionist approach to complex biological issues, like SD, with more penetrating approaches to the study of cause-effect relationships, i.e., network theory. The review concludes by advising against generalization regarding SD and parasitism and by pointing to some of the most promising lines of research.

Population genetic structure of Taenia solium from Madagascar and Mexico: implications for clinical profile diversity and immunological technology

Taenia solium is a cestode parasitic of humans and pigs that strongly impacts on public health in developing countries. Its larvae (cysticercus) lodge in the brain, causing neurocysticercosis, and in other tissues, like skeletal muscle and subcutaneous space, causing extraneuronal cysticercosis. Prevalences of these two clinical manifestations vary greatly among continents. Also, neurocysticercosis may be clinically heterogeneous, ranging from asymptomatic forms to severely incapacitating and even fatal presentation. Further, vaccine design and diagnosis technology have met with difficulties in sensitivity, specificity and reproducibility. Parasite diversity underlying clinical heterogeneity and technological difficulties is little explored. Here, T. solium genetic population structure and diversity was studied by way of random amplified polymorphic DNA in individual cysticerci collected from pigs in Madagascar and two regions in Mexico. The amplification profiles of T. solium were also compared with those of the murine cysticercus Taenia crassiceps (ORF strain). We show significant genetic differentiation between Madagascar and Mexico and between regions in Mexico, but less so between cysticerci from different localities in Mexico and none between cysticerci from different tissues from the same pig. We also found restricted genetic variability within populations and gene flow was estimated to be low between populations. Thus, genetic differentiation of T. solium suggests that different evolutionary paths have been taken and provides support for its involvement in the differential tissue distribution of cysticerci and varying degrees of severity of the disease. It may also explain difficulties in the development of vaccines and tools for immunodiagnosis.

Diagnosis, treatment and control of Taenia solium cysticercosis

PURPOSE OF REVIEW

Taenia solium taeniasis/cysticercosis is now recognized as a major public health problem in most developing countries because of its association with seizures. Major advances in the diagnosis and epidemiology of taeniasis/cysticercosis have occurred in recent years. However, despite abundant literature on the subject, many questions remain unanswered including the role of anti-parasitic therapy and the potential for long-term control or elimination of the disease in field conditions following active interventions.

RECENT FINDINGS

Recent advances have included improved knowledge of the availability and optimization of diagnostic tools for the tapeworm stage, a better understanding of the meaning of antibody serology, the introduction of antigen detection assays, a consensus on the use of antiparasitic medication, awareness of inflammation and chronic scars around calcified cysts, population-based neuroimaging studies, application of control measures, and progress in the development of a pig vaccine.

SUMMARY

Neurocysticercosis is now much better understood than it was a few years ago. Infection and disease are now classified in terms of parasite viability, resulting in multiple and diverse clinical entities, each of which has a proper prognosis and management. As a result of this, the interpretation of diagnostic assays and imaging examinations is much more coherent. New aspects of this interesting disease have been recognized, mainly in relation to the frequency of calcified neurocysticercosis and its potential association with symptomatic relapses. Consensus diagnostic and treatment schemes have been proposed, and promising alternatives for control are currently being tested in several countries.

Vaccination against cestode parasites: anti-helminth vaccines that work and why

Highly effective recombinant vaccines have been developed against the helminth parasites Taenia ovis, Taenia saginata and Echinococcus granulosus. These vaccines indicate that it is possible to achieve a reliable, high level of protection against a complex metazoan parasite using defined recombinant antigens. However, the effectiveness of the vaccines against the taeniid cestodes stands in contrast to the more limited successes which characterise attempts to develop vaccines against other platyhelminth or nematode parasites. This review examines the features of the host-parasite relationships among the taeniid cestodes which have formed the basis for vaccine development. Particular consideration is given to the methodologies that have been used in making the cestode vaccines that might be of interest to researchers working on vaccination against other helminths. In developing the cestode vaccines, antigens from the parasites' infective larval stage contained within the egg (oncosphere) were identified as having the potential to induce high levels of protection in vaccinated hosts. A series of vaccination trials with antigen fractions, and associated immunological analyses, identified individual protective antigens or fractions. These were cloned from cDNA and the recombinant proteins expressed in Escherichia coli. This strategy was independently successful in developing vaccines against T. ovis and E. granulosus. Identification of protective antigens for these species enabled rapid identification, cloning and expression of their homologues in related species and thereby the development of effective vaccines against T. saginata, E. multilocularis and, more recently, T. solium. The T. saginata vaccine provides an excellent example of the use of two antigen components, each of which were not protective when used individually, but when combined they induce a reliable, high level of protection. One important contributing factor to the success of vaccine development for the taeniid cestodes was the concentration on studies seeking to identify native host-protective antigens, before the adoption of recombinant methodologies. The cestode vaccines are being developed towards practical (commercial) application. The high level of efficacy of the vaccines against T. solium cysticercosis and hydatid disease suggests that they would be effective also if used directly in humans.

Control of Taenia solium

Control or eradication of Taenia solium cysticercosis has been achieved to date only in Europe and North America. Significant improvements in sanitary conditions and developing functional slaughterhouse control systems were primarily responsible for control in these regions. Conversely, in endemic areas of developing countries control is limited by economic and sanitary conditions: the life cycle of T. solium is sustained because pigs have access to infected faeces, and cysticercosis-infested pork is available for consumption. Interventional trials with massive human cestocidal chemotherapy, treatment of both human and porcine populations with antihelminthic drugs and/or immunotherapy and health education have shown improvements in specific settings but not yet proven to be sustainable in the long-term. In order to ensure sustainability, any given control strategy towards elimination/eradication of porcine cysticercosis should incorporate economic incentives.