Vaccination against very virulent infectious bursal disease virus using recombinant T4 bacteriophage displaying viral protein VP2

Bacteriophage T4 nanoparticles for vaccine delivery against infectious diseases

Subunit vaccines containing one or more target antigens from pathogenic organisms represent safer alternatives to whole pathogen vaccines. However, the antigens by themselves are not sufficiently immunogenic and require additives known as adjuvants to enhance immunogenicity and protective efficacy. Assembly of the antigens into virus-like nanoparticles (VLPs) is a better approach as it allows presentation of the epitopes in a more native context. The repetitive, symmetrical, and high density display of antigens on the VLPs mimic pathogen-associated molecular patterns seen on bacteria and viruses. The antigens, thus, might be better presented to stimulate host's innate as well as adaptive immune systems thereby eliciting both humoral and cellular immune responses. Bacteriophages such as phage T4 provide excellent platforms to generate the nanoparticle vaccines. The T4 capsid containing two non-essential outer proteins Soc and Hoc allow high density array of antigen epitopes in the form of peptides, domains, full-length proteins, or even multi-subunit complexes. Co-delivery of DNAs, targeting molecules, and/or molecular adjuvants provides additional advantages. Recent studies demonstrate that the phage T4 VLPs are highly immunogenic, do not need an adjuvant, and provide complete protection against bacterial and viral pathogens. Thus, phage T4 could potentially be developed as a "universal" VLP platform to design future multivalent vaccines against complex and emerging pathogens.

Advances in vaccine research against economically important viral diseases of food animals: Infectious bursal disease virus

Numerous reviews have been published on infectious bursal disease (IBD) and infectious bursal disease virus (IBDV). Many high quality vaccines are commercially available for the control of IBD that, when used correctly, provide solid protection against infection and disease caused by IBDV. Viruses are not static however; they continue to evolve and vaccines need to keep pace with them. The evolution of IBDV has resulted in very virulent strains and new antigenic types of the virus. This review will discuss some of the limitations associated with existing vaccines, potential solutions to these problems and advances in new vaccines for the control of IBD.

Infectious bursal disease virus in poultry: current status and future prospects

Infectious bursal disease virus (IBDV) affects immature B lymphocytes of the bursa of Fabricius and may cause significant immunosuppression. It continues to be a leading cause of economic losses in the poultry industry. IBDV, having a segmented double-stranded RNA genome, is prone to genetic variation. Therefore, IBDV isolates with different genotypic and phenotypic diversity exist. Understanding these features of the virus and the mechanisms of protective immunity elicited thereof is necessary for developing vaccines with improved efficacy. In this review, we highlighted the pattern of virus evolution and new developments in prophylactic strategies, mainly the development of new generation vaccines, which will continue to be of interest for research as well as field application in the future.

Genetically modified bacteriophages

Applications of genetically modified bacteriophages.

Characterization of field and vaccine infectious bursal disease viruses from Nigeria revealing possible virulence and regional markers in the VP2 minor hydrophilic peaks

Outbreaks of infectious bursal disease in vaccinated chicken flocks are frequent in Nigeria. For the control of infectious bursal disease, live vaccines based on foreign infectious bursal disease virus (IBDV) strains are used. The present study investigated the phylogenetic relationship between field and vaccine IBDV strains from northwestern Nigeria. Thirty field IBDV strains and three commercial vaccines strains were characterized through sequencing the VP2 hypervariable region. In addition, the complete genome segment A coding region for two vaccines and two field strains was sequenced. The deduced amino acid sequences (position 212 to 331) of IBDV strains from Nigeria and other regions of the world were aligned and possible regional and virulence markers were identified associated with VP2 minor hydrophilic peaks. Reversion to virulence of a vaccine strain with a Q to L mutation at position 253 was observed. Phylogenetic analyses revealed a unique cluster of northwest Nigerian field IBDV strains alone or related to imported characterized classical and very virulent IBDV vaccines. The results suggest that when IBDV strains spread from their region of origin to a different region they mutate alongside indigenous field strains but may retain their identity on the VP2 region.

Current status of vaccines against infectious bursal disease

Infectious bursal disease virus (IBDV) is the aetiological agent of the acute and highly contagious infectious bursal disease (IBD) or "Gumboro disease". IBD is one of the economically most important diseases that affects commercially produced chickens worldwide. Along with strict hygiene management of poultry farms, vaccination programmes with inactivated and live attenuated viruses have been used to prevent IBD. Live vaccines show a different degree of attenuation; many of them may cause bursal atrophy and thus immunosuppression with poor immune response to vaccination against other pathogens and an increase in vulnerability to various types of infections as possible consequences. Depending on their intrinsic characteristics or on the vaccination procedures, some of the vaccines may not induce full protection against the very virulent IBDV strains and antigenic variants observed in the last three decades. As chickens are most susceptible to IBDV in their first weeks of life, active immunity to the virus has to be induced early after hatching. However, maternally derived IBDV-specific antibodies may interfere with early vaccination with live vaccines. Thus new technologies and second-generation vaccines including rationally designed and subunit vaccines have been developed. Recently, live viral vector vaccines have been licensed in several countries and are reaching the market. Here, the current status of IBD vaccines is discussed.

IgA response of BALB/c mice to orally administered Salmonella typhimurium flagellin-displaying T2 bacteriophages

Salmonella typhimurium antigens were displayed on the capsid of a T2 bacteriophage to explore the potential of phage display for an oral vaccine. Segments of the flagellin proteins FliC (H1 antigen) and FljB (H2) were fused to the N-terminal of T2 phage SOC to give two recombinant phages, T2FliCm and T2FljBm. Over 14 days, 19 BALB/c mice were orally administered twice, either with purified recombinant FliCm and FljBm protein, or T2FliCm and T2FljBm with or without host Escherichia coli. Feces were sampled over 10 weeks and examined for phage by plaque assay and for the presence of mucosal IgA by ELISA. Relatively few phages were detected relative to the amount administered (up to 8.21 x 10(3) PFU/g faeces) and none were detected five days after initial administration. The administration of a large number of phages appeared to cause no clinical symptoms. IgA concentration in feces peaked around four weeks after the second administration and subsided after eight weeks. The highest relative titers were observed in the protein group (0.37% for anti-FliCm and 0.22% for anti-FljBm) and the mouse group which received no E. coli (0.33% and 0.35%) despite the theoretical amount of protein contained in a phage dose being at least 80-465 times lower than the protein dose administered. The possibility that the immuno-stimulatory properties of the phage create an adjuvant effect to enhance the immunogenic properties of the displayed proteins is discussed. We conclude that phage may be valuable as a vector for oral vaccines.

Bacteriophage interactions with phagocytes and their potential significance in experimental therapy

Bacteriophages are among the most numerous creatures on earth and they are omnipresent. They are thus in constant natural contact with humans and animals. However, the clinical and technological use of bacteriophages has also become more frequent, which is why all aspects of phage-mammal interactions need to be explored. Bacteriophages are able to interact with mammalian phagocytes. They may inhibit the phagocytosis of bacteria, but they may also undergo phagocytosis themselves. The ability of bacteriophages to reduce reactive oxygen species production by polymorphonuclear leukocytes in the presence of bacteria or their endotoxins was also confirmed. Studies show that the high immunogenicity of bacteriophages may also be employed in anti-tumor treatment. The present knowledge of phage interactions with cellular components of the mammalian immune system is sparse and insufficient, especially considering the increasing interest in the application of these viruses in human life. We believe that continuation of such research is indispensable.

Molecular modification of T4 bacteriophage proteins and its potential application - review

Bacteriophage T4 is a virus with well-known genetics, structure, and biology. Such techniques as X-ray crystallography, cryo-EM, and three-dimensional (3D) image reconstruction allowed describing its structure very precisely. The genome of this bacteriophage was completely sequenced, which opens the way for the use of many molecular techniques, such as site-specific mutagenesis, which was widely applied, e.g., in investigating the functions of some essential T4 proteins. The phage-display method, which is commonly applied in bacteriophage modifications, was successfully used to display antigens (PorA protein, VP2 protein of vvIBDV, and antigens of anthrax and HIV) on T4's capsid platform. As first studies showed, the phage-display system as well as site-specific mutagenesis may also be used to modify interactions between phage particles and mammalian cells or to obtain phages infecting species other than the host bacteria. These may be used, among others, in the constantly developing bacteriophage therapy. All manipulations of this popular bacteriophage may enable the development of vaccine technology, phage therapy, and other branches of biological and medical science.

Orally delivered foot-and-mouth disease virus capsid protomer vaccine displayed on T4 bacteriophage surface: 100% protection from potency challenge in mice

An orally delivered foot-and-mouth disease (FMD) vaccine has not previously been reported. By using a T4 bacteriophage nanoparticle surface gene-protein display system (T4-S-GPDS), we created a foot-and-mouth disease virus (FMDV) entire capsid protein vaccine candidate. On the T4 phage surface SOC site, a full length FMDV capsid precursor polyprotein (P1, 755 aa) and proteinase 3C (213 aa) derived from an infected pig of serotype O strain GD-10 (1999), were separately displayed on different T4 phage particle surfaces through inserting their coding region DNAs into the T4 phage genome, yielding phage strains T4-P1 and T4-3C. We also constructed a series of FMDV sub-full length capsid structural protein (subunit) containing T4 phage recombinant vaccines. Both sucking and young BALB/c mice were used as two kinds of FMDV vaccine potency evaluation models. Many groups of both model mice were vaccinated orally or by subcutaneous injection with varying FMDV-T4 phage recombinant vaccines, with and without addition of adjuvant, then challenged with a lethal dose of cattle source virulent FMDV. In the case of immunization with a mixture of phage T4-P1 and phage T4-3C particles without any adjuvant added, all mice were 100% protected following either oral or injection immunization, whereas 100% of the control, non-immunized mice and mice immunized with only T4 phage vector Z1/Zh(-) or wild-type T4(+)D phage died; in contrast, with FMDV subunit vaccine, less than 75% protection followed the same potency challenge in both mice model groups. In addition, two pigs immunized with a phage T4-P1 and phage T4-3C mix were protected upon housing together with infected pigs. This study represents a clear example of how FMD and other pathogenic disease vaccines can be prepared by a simple and efficient bacteriophage route.

Bacteriophage T4 nanoparticle capsid surface SOC and HOC bipartite display with enhanced classical swine fever virus immunogenicity: a powerful immunological approach

The phage T4 HOC, SOC bipartite display system is attractive for the expression of cDNA and display of peptides or proteins at high copy numbers on the phage capsid surface. Until recently, using T4 phage vector to display large foreign molecular immunogens resulted only from either an SOC or HOC single site. In this report, the main advantages of the phage T4 system over other display technologies are substantiated by using the phage T4 SOC, HOC dual site display vector T4-Zh(-) to express: (1) on the SOC site, the classical swine fever virus (CSFV) major antigenic determinant cluster mE2 (123 amino acid, aa) through gene fusion to the SOC gene C-terminus of T4 genome, and (2) on the HOC site, full-length CSFV primary antigen E2 (371 aa) through a co-transformed plasmid, hence leading to a simultaneous display of both proteins on the T4 capsid surface. The immunogenicities of these constructs were measured by ID-ELISA, dot-ELISA, Western blotting, and immunogenic response in mice including humoral and cellular immunity tests. The immunological efficiencies both in vitro and in mice of phage T4 with both single site and dual site displays, as well as conventional Escherichia coli plasmid expression, were evaluated. The animal immune response data showed that the antibody titers elicited by the T4 phage-CSFV recombinants were significantly higher than those obtained by E. coli plasmid expression, and the unpurified double site display T4 phage particles were around two times higher than either single site display or plasmid expression while being at lower phage concentrations than the single site phages. The immunogens were effective in the absence of eukaryotic protein modifications. Therefore, the phage T4 dual site display emerges as a powerful method with an enhanced immune response in animals for research and development of immunological products.

Efficacy of VP2 protein expressed in E. coli for protection against highly virulent infectious bursal disease virus

The ability of a heat-inactivated whole virus from a highly virulent infectious bursal disease virus (hvIBDV) and VP2 protein from hvIBDV expressed in E. coli provided protection against a hvIBDV challenge in specificpathogen-free (SPF) chickens. Six out of seven chickens that were injected three times with crude VP2 protein developed significant antibody titer against IBDV. However, only four out of the seven chickens survived the hvIBDV challenge. Despite showing low antibody titer profiles, all chickens immunized with the heat-inactivated whole virus also survived the challenged with hvIBDV. However, all of these chickens had bursal atrophy and mild to moderate depletion of lymphocytes. Thus, antibodies raised against IBDV VP2 protein expressed in E. coli and denatured IBDV proteins induced some degree of protection against mortality but not against bursal damage following challenge with hvIBDV.