Recombinant expression and purification of T4 phage Hoc, Soc, gp23, gp24 proteins in native conformations with stability studies

Evolution of the T4 phage virion is driven by selection pressure from non-bacterial factors

Bacteriophages colonize animal and human bodies, propagating on sensitive bacteria that are symbionts, commensals, or pathogens of animals and humans. T4-like phages are dependent on abundant symbionts such as Escherichia coli, commonly present in animal and human gastrointestinal (GI) tracts. Bacteriophage T4 is one of the most complex viruses, and its intricate structure, particularly the capsid head protecting the phage genome, likely contributes substantially to the overall phage fitness in diverse environments. We investigated how individual head proteins-gp24, Hoc, and Soc-affect T4 phage survival under pressure from non-bacterial factors. We constructed a panel of T4 phage variants defective in these structural proteins: T4∆Soc, T4∆24byp24, T4∆Hoc∆Soc, T4∆Hoc∆24byp24, T4∆Soc∆24byp24, and T4∆Hoc∆Soc∆24byp24 (byp = bypass). These variants were investigated for their sensitivity to selected environmental conditions relevant to the microenvironment of the GI tract, including pH, temperature, and digestive enzymes. The simple and "primitive" structure of the phage capsid (∆24byp24) was significantly less stable at low pH and more sensitive to inactivation by digestive enzymes, and the simultaneous lack of gp24 and Soc resulted in a notable decrease in phage activity at 37°C. Gp24 was also found to be highly resistant to thermal and chemical denaturation. Thus, gp24, which was acquired relatively late in evolution, seems to play a key role in T4 withstanding environmental conditions, including those related to the animal/human GI tract, and Soc is a molecular glue that enhances this protective effect. IMPORTANCE Bacteriophages are important components of animal and human microbiota, particularly in the gastrointestinal tract, where they dominate the viral community and contribute to shaping microbial balance. However, interactions with bacterial hosts are not the only element of the equation in phage survival-phages inhabiting the GI tract are constantly exposed to increased temperature, pH fluctuations, or digestive enzymes, which raises the question of whether and how the complex structure of phage capsids contributes to their persistence in the specific microenvironment of human/animal bodies. Here we address this phage-centric perspective, identifying the role of individual head proteins in T4 phage survival in GI tract conditions. The selection pressure driving the evolution of T4-like phages could have come from the external environment that affects phage virions with increased temperature and variable pH; it is possible that in the local microenvironment along the GI tract, the phage benefits from stability-protecting proteins.

The novel combinations of CTB, CpG, and aluminum hydroxide significantly enhanced the immunogenicity of clumping factor A 221-550 of Staphylococcus aureus

Here, we prepared the novel combined adjuvants, CTB as intra-molecular adjuvant, CpG and aluminum hydroxide (Alum) to strengthen the immunogenicity of clumping factor A_221-550 of Staphylococcus aureus (S. aureus). The protein-immunoactive results showed CTB-ClfA_221-550 elicited the strong immune responses to serum from mice immunized with CTB and ClfA_221-550, respectively. The mice immunized with CTB-ClfA_221-550 plus CpG and Alum adjuvant exhibited significantly stronger CD4⁺ T cell responses for IFN-γ, IL-2, IL-4, and IL-17 and displayed the higher proliferation response of splenic lymphocytes than the control groups, in addition, these mice generated the strongest humoral immune response against ClfA_221-550 among all groups. Our results also showed CTB-ClfA_221-550 plus CpG and Alum adjuvant obviously increased the survival percentage of the mice challenged by S. aureus. These data suggested that the novel combined adjuvants, CTB, CpG, and Alum, significantly enhance the immune responses triggered with ClfA_221-550, and could provide a new approach against infection of S. aureus.

ABBREVIATIONS

CTB: Cholera Toxin B; CpG: Cytosine preceding Guanosine; ODN: Oligodeoxynucleotides; Alum: Aluminum hydroxide; TRAP: Target of RNAIII-activating Protein; TLR9: Toll-like Receptor 9; TMB: 3, 3', 5, 5'-tetramethylbenzidine; mAbs: Monoclonal Antibodies; OD: Optical Densities; S. aureus: Staphylococcus aureus; ClfA: Clumping factor A; FnBPA: Fibronection-binding protein A; IsdB: Iron-regulated surface determinant B; SasA: Staphylococcus aureus Surface Protein A; GapC: Glycer-aldehyde-3-phosphate dehydrogenase-C.

The double adjuvants LTB and CpG significantly enhanced the immuno-protective effects of recombinant GIT derived from Staphylococcus aureus and Streptococcus in mice

PURPOSE

In this study, we prepared GapC1-150-IsdB126-361-TRAP (GIT) proteins plus heat-labile enterotoxin B (LTB) as an intra-molecular adjuvant, together with CpG to further enhance its immunogenicity.

METHODOLOGY

Initially, the target genes were acquired and inserted into pET-32a (+) vectors to express LTB-GIT protein. LTB-GIT expression was confirmed by Western blotting and its immunocompetence was estimated through ELISA. Further, we immunized BALB/c mice with the LTB-GIT plus CpG adjuvant. After the second immunization, the antigen-specific CD4⁺ cell responses for IFN-γ, IL-2, IL-4 and IL-10 were monitored by intracellular cytokine staining (ICS) assay. After the third immunization, the level of IgG antibodies in the serum from immunized groups was assessed by ELISA, and the protective immune response was appraised by Staphylococcus aureus and Streptococcus dysgalactiae challenge.

RESULTS

The ELISA results showed that the OD450nm value of the LTB-GIT group was significantly higher than that of the BSA group. The group immunized with LTB-GIT plus CpG exhibited significantly stronger CD4⁺ T cell responses for IFN-γ, IL-2, IL-4 and IL-10 compared to the group immunized with LTB-GIT, GIT alone orLTB-GIT plus CpG. In addition, the group immunized with LTB-GIT plus CpG generated the highest level of IgG antibodies against GIT among all of the groups, and our results also showed that LTB-GIT plus CpG markedly improved the survival percentage of mice compared to other groups.

CONCLUSION

We confirmed that the novel double adjuvants, LTB and CpG, are able to significantly improve GIT-induced immune responses. This formula could be a promising strategy for enhancing the immune efficacy of multi-subunit vaccines against Staphylococcus aureus and streptococcal infection.

T4 Phage Tail Adhesin Gp12 Counteracts LPS-Induced Inflammation In Vivo

Bacteriophages that infect Gram-negative bacteria often bind to the bacterial surface by interaction of specific proteins with lipopolysaccharide (LPS). Short tail fiber proteins (tail adhesin, gp12) mediate adsorption of T4-like bacteriophages to Escherichia coli, binding surface proteins or LPS. Produced as a recombinant protein, gp12 retains its ability to bind LPS. Since LPS is able to exert a major impact on the immune response in animals and in humans, we have tested LPS-binding phage protein gp12 as a potential modulator of the LPS-induced immune response. We have produced tail adhesin gp12 in a bacterial expression system and confirmed its ability to form trimers and to bind LPS in vitro by dynamic light scattering. This product had no negative effect on mammalian cell proliferation in vitro. Further, no harmful effects of this protein were observed in mice. Thus, gp12 was used in combination with LPS in a murine model, and it decreased the inflammatory response to LPS in vivo, as assessed by serum levels of cytokines IL-1 alpha and IL-6 and by histopathological analysis of spleen, liver, kidney and lungs. Thus, in future studies gp12 may be considered as a potential tool for modulating and specifically for counteracting LPS-related physiological effects in vivo.

Oral Application of T4 Phage Induces Weak Antibody Production in the Gut and in the Blood

A specific humoral response to bacteriophages may follow phage application for medical purposes, and it may further determine the success or failure of the approach itself. We present a long-term study of antibody induction in mice by T4 phage applied per os: 100 days of phage treatment followed by 112 days without the phage, and subsequent second application of phage up to day 240. Serum and gut antibodies (IgM, IgG, secretory IgA) were analyzed in relation to microbiological status of the animals. T4 phage applied orally induced anti-phage antibodies when the exposure was long enough (IgG day 36, IgA day 79); the effect was related to high dosage. Termination of phage treatment resulted in a decrease of IgA again to insignificant levels. Second administration of phage induces secretory IgA sooner than that induced by the first administrations. Increased IgA level antagonized gut transit of active phage. Phage resistant E. coli dominated gut flora very late, on day 92. Thus, the immunological response emerges as a major factor determining phage survival in the gut. Phage proteins Hoc and gp12 were identified as highly immunogenic. A low response to exemplary foreign antigens (from Ebola virus) presented on Hoc was observed, which suggests that phage platforms can be used in oral vaccine design.

Immunogenicity studies of proteins forming the T4 phage head surface

Advances in phage therapy and novel applications of phages in biotechnology encourage interest in phage impact on human and animal immunity. Here we present comparative studies of immunogenic properties of T4 phage head surface proteins gp23*, gp24*, Hoc, and Soc, both as elements of the phage capsid and as isolated agents. Studies comprise evaluation of specific antibodies in the human population, analysis of the proteins' impact on the primary and secondary responses in mice, and the effect of specific antibodies on phage antibacterial activity in vitro and in vivo in mice. In humans, natural antibodies specific to T4-like phages were abundant (81% of investigated sera). Among those, significantly elevated levels of IgG antibodies only against major head protein (gp23*) were found, which probably reflected cross-reactions of T4 with antibodies induced by other T4-like phages. Both IgM and IgG antibodies were induced mostly by gp23* and Hoc, while weak (gp24*) and very weak (Soc) reactivities of other head proteins were noticed. Thus, T4 head proteins that markedly contribute to immunological memory to the phage are highly antigenic outer capsid protein (Hoc) and major capsid protein (gp23*). Specific anti-gp23* and anti-Hoc antibodies substantially decreased T4 phage activity in vitro and to some extent in vivo. Cooperating with antibodies, the immune complement system also contributed to annihilating phages.

IMPORTANCE

Current descriptions of phage immunogenicity and its biological consequences are still vague and incomplete; thus, the central problem of this work is timely and may have strong practical implications. Here is presented the very first description of the contribution of bacteriophage proteins to immunological memory of the phage. Understanding of interactions between phages and mammalian immunology may help in biotechnological adaptations of phages for therapeutic requirements as well as for better appreciation of phage ecology and their role in the biosphere.

Bacteriophages displaying anticancer peptides in combined antibacterial and anticancer treatment

ABSTRACT: 

Aims: Novel anticancer strategies have employed bacteriophages as drug carriers and display platforms for anticancer agents; however, bacteriophage-based platforms maintain their natural antibacterial activity. This study provides the assessment of combined anticancer (engineered) and antibacterial (natural) phage activity in therapies. Materials & methods: An in vivo BALB/c mouse model of 4T1 tumor growth accompanied by surgical wound infection was applied. The wounds were located in the areas of tumors. Bacteriophages (T4) were modified with anticancer Tyr–Ile–Gly–Ser–Arg (YIGSR) peptides by phage display and injected intraperitoneally. Results & conclusion: Tumor growth was decreased in mice treated with YIGSR-displaying phages. The acuteness of wounds, bacterial load and inflammatory markers in phages-treated mice were markedly decreased. Thus, engineered bacteriophages combine antibacterial and anticancer activity.

Highly purified mussel adhesive protein to secure biosafety for in vivo applications

BACKGROUND

Unique adhesive and biocompatibility properties of mussel adhesive proteins (MAPs) are known for their great potential in many tissue engineering and biomedical applications. Previously, it was successfully demonstrated that redesigned hybrid type MAP, fp-151, mass-produced in Gram-negative bacterium Escherichia coli, could be utilized as a promising adhesive biomaterial. However, purification of recombinant fp-151 has been unsatisfactory due to its adhesive nature and polarity which make separation of contaminants (especially, lipopolysaccharide, a toxic Gram-negative cell membrane component) very difficult.

RESULTS

In the present work, we devised a high resolution purification approach to secure safety standards of recombinant fp-151 for the successful use in in vivo applications. Undesirable impurities were remarkably eliminated as going through sequential steps including treatment with multivalent ion and chelating agent for cell membrane washing, mechanical cell disruption, non-ionic surfactant treatment for isolated inclusion body washing, acid extraction of washed inclusion body, and ion exchange chromatography purification of acid extracted sample. Through various analyses, such as high performance liquid chromatographic purity assay, limulus amoebocyte lysate endotoxin assay, and in vitro mouse macrophage cell tests on inflammation, viability, cytotoxicity, and apoptosis, we confirmed the biological safety of bacterial-derived purified recombinant fp-151.

CONCLUSIONS

Through this purification design, recombinant fp-151 achieved 99.90% protein purity and 99.91% endotoxin reduction that nearly no inflammation response was observed in in vitro experiments. Thus, the highly purified recombinant MAP would be successfully used as a safety-secured in vivo bioadhesive for tissue engineering and biomedical applications.

A novel approach for separating bacteriophages from other bacteriophages using affinity chromatography and phage display

Practical applications of bacteriophages in medicine and biotechnology induce a great need for technologies of phage purification. None of the popular methods offer solutions for separation of a phage from another similar phage. We used affinity chromatography combined with competitive phage display (i) to purify T4 bacteriophage from bacterial debris and (ii) to separate T4 from other contaminating bacteriophages. In ‘competitive phage display’ bacterial cells produced both wild types of the proteins (expression from the phage genome) and the protein fusions with affinity tags (expression from the expression vectors). Fusion proteins were competitively incorporated into the phage capsid. It allowed effective separation of T4 from a contaminating phage on standard affinity resins.