Application of a Virus-Like Particle Platform to the Development of a Vaccine against Neisseria gonorrhoeae

Abstract

Gonorrhoea is a global public health concern, owing to its growing rise in incidence due to antibiotic resistance and severe health complications caused, especially in women. Although a vaccine is considered essential for the prevention and control of gonorrhoea infections, its development has remained elusive, hampered by antigenic variation and a lack of a correlate of protection following infection. Firstly, this project aimed to develop modified virus-like particle (VLP) vaccine candidates against Neisseria gonorrhoeae. These candidates were derived from the core protein of the Hepatitis B virus (HBc) and capable of binding antigens fused to antibody Fc domains via S. aureus Protein A domains located on the surface. Secondly, the project investigated the production of gonococcal antigen-Fc fusions in an in vitro HEK293 cell expression system. Thirdly, the production of the modified HBc VLPs in Nicotiana tabacum (N. tabacum) plants was investigated as a low-cost expression system suitable for manufacturing in low- to middle-income countries (LMICs). Selected Fc-fused gonococcal antigens produced were soluble, thermally stable, and correctly assembled. Immunisation studies were conducted in BALB/c female mice vaccinated with modified HBc VLPs decorated with gonococcal antigens produced in human cells (HEK293). The analysis of ELISA results found high levels of antigen-specific IgG antibodies in the mouse serum that could recognise cognate antigens expressed in bacteria (Escherichia coli). The sequences encoding the modified VLPs were inserted into chloroplast expression vectors and N. tabacum leaves were transformed by particle bombardment. Following in vitro spectinomycin‐based selection for transgenic cells, resistant shoots were screened with anti-HBc mouse sera for HBc VLP expression. Transformants were transferred to soil for scale-up. The modified HBc VLPs were shown to accumulate in chloroplasts of N. tabacum plants as assembled particles structurally similar to the bacterial-derived HBc VLPs. In conclusion, the modified HBc VLP platform's versatility in displaying a diverse range of gonococcal antigens makes it a promising technology for developing a vaccine against gonorrhoea. Adopting low-cost plant systems to manufacture vaccines can address global vaccine inequity.

Date of Award	4 Mar 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jeremy Derrick (Main Supervisor) & Anil Day (Co Supervisor)