Highly Effective Soluble and Bacteriophage T4 Nanoparticle Plague Vaccines Against Yersinia pestis

Abstract

Plague caused by Yersinia pestis is an ancient disease, responsible for millions of deaths in human history. Unfortunately, there is no FDA-approved vaccine available. Recombinant subunit vaccines based on two major antigens, Caf 1 (F1) and LcrV (V), have been under investigation and showed promise. However, there are two main problems associated with these vaccines. First, the Yersinia capsular protein F1 has high propensity to aggregate, particularly when expressed in heterologous systems such as Escherichia coli, thus affecting vaccine quality and efficacy. Second, the subunit vaccines do not induce adequate cell-mediated immune responses that also appear to be essential for optimal protection against plague. We have developed two basic approaches, structure-based immunogen design and phage T4 nanoparticle delivery, to construct new plague vaccines that may overcome these problems. First, by engineering F1 protein, we generated a monomeric and soluble F1V mutant (F1mutV) which has similar immunogenicity as wild-type F1V. The NH2-terminal β-strand of F1 was transplanted to the COOH-terminus and the sequence flanking the β-strand was duplicated to retain a key CD4+ T cell epitope. Second, we generated a nanoparticle plague vaccine that can induce balanced antibody- and cell-mediated immune responses. This was done by arraying the F1mutV on phage T4 via the small outer capsid (Soc) protein which binds to T4 capsid at nanomolar affinity. Preparation of these vaccines is described in detail and we hope that these would be considered as candidates for licensing a next-generation plague vaccine.

Bacteriophage T4 as a Nanoparticle Platform to Display and Deliver Pathogen Antigens: Construction of an Effective Anthrax Vaccine

“…Recently, we have developed a novel antigen delivery system using the bacteriophage T4 capsid [2–4]. Antigens were displayed on the T4 capsid at a high density, and, upon immunization, they elicited robust humoral and cellular immune responses without any adjuvant, making T4 a robust antigen display and delivery system [2, 3, 5, 6].…”

“… 3 We had also constructed a universal vector, pET-Soc-C, which contains a multiple cloning site (MCS) at NH2-terminus of Soc [4]. Any other antigen gene can be amplified by PCR and cloned into pET-Soc-C to generate an in-frame fusion with the NH2-terminal end of Soc.…”

Identification of Essential Genes in the Salmonella Phage SPN3US Reveals Novel Insights into Giant Phage Head Structure and Assembly

“…Historically, the genetic system based on the T4 phage has been one of the most paradigm-shifting model systems in biology, and it is critical for our understanding of the fine structure of the gene and many of the founding principles of molecular genetics (28–31). The T4 system continues to be employed by researchers around the world for purposes ranging from addressing questions pertaining to fundamental molecular interactions (such as the molecular motor that drives DNA into phage heads [32]) to the creation of novel vaccines and therapeutics (33, 34). We hypothesized that a similar model system for a giant phage would also be an extremely powerful tool for understanding their biology and potentially for developing novel therapeutics, especially if we could blend classical genetics with omics approaches.…”

Engineering of Bacteriophage T4 Genome Using CRISPR-Cas9

“…9–11 We have developed one such platform using T4, a tailed phage belonging to the Myoviridae family. 12–14 A unique feature of phage T4 is that its 120 × 86 nm size capsid (head) is decorated with two nonessential outer capsid proteins, Soc or small outer capsid protein (870 copies) and Hoc or highly antigenic outer capsid protein (155 copies). 2,15 Antigens fused to Soc or Hoc, up to 1025 per head, can be displayed on the hoc − soc − T4 capsid with high affinity and exquisite specificity.…”