Toward the development of a stable, freeze-dried formulation ofHelicobacter pylorikilled whole cell vaccine adjuvanted with a novel mutant ofEscherichia coliheat-labile toxin

• Published in: Vaccine 2010-02, Vol.28 (5), p.1404
• Main Authors: Summerton, Nancy A, Welch, Richard W, Bondoc, Laureano, Yang, Huei-Hsiung, Pleune, Brett, Ramachandran, Naryaswamy, Harris, Andrea M, Bland, Desiree, Jackson, W James, Park, Sukjoon, Clements, John D, Nabors, Gary S
• Format: Article
• Language: English
• Subjects: Antigens; Diarrhea; Infections; Moisture content; Mutants; Side effects; Stomach; Toxins; Ulcers; Vaccines
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2009.10.147

No vaccine exists for the prevention of infection with the ubiquitous gastric pathogenHelicobacter pylori, and drug therapy for the infection is complicated by poor patient compliance, the high cost of treatment, and ineffectiveness against drug-resistant strains. A new medical advancement is required to reduce the incidence of peptic ulcer disease and stomach cancer, two conditions caused by infection withH. pylori. Clinical trials have been performed with a formalin-inactivatedH. pyloriwhole cell (HWC) vaccine, given orally in combination with the mucosal adjuvant mLT(R192G), a mutant ofEscherichia coliheat-labile toxin. Following the initial dose of this vaccine, some subjects experienced gastrointestinal side effects. To reduce side effects and potentially further increase the amount of adjuvant that can safely be administered with the HWC vaccine, experiments were performed with a form of LT that carried two mutations in the A subunit, a substitution of G for R at position 192, and A for L at position 211. The double mutant LT (dmLT) adjuvant stimulated immune responses as effectively as the single mutant LT in mice. Additionally, following a challenge infection, the dmLT-adjuvanted vaccine was as effective as single mutant LT in reducing gastric urease levels (diagnostic forH. pyloriinfection), andH. pyloricolonization in the stomach as assessed by quantitative analysis of stomach homogenates. A lyophilized formulation of HWC was developed to improve stability and to potentially reduce reliance on cold chain maintenance. It was observed that a dmLT-adjuvanted lyophilized vaccine was equally as protective in the mouse model as the liquid formulation as assessed by gastric urease analysis and analysis of stomach homogenates for viableH. pylori. No readily detectable effect of tonicity or moisture content was observed for the lyophilized vaccine within the formulation limits evaluated. In an accelerated stability study performed at 37°C the lyophilized vaccine remained equally as protective as vaccine stored at 2-8°C. The formulation selected for clinical development consisted of 2.5x1010formalin-inactivated cells per ml in 6.5% trehalose, 0.5% mannitol, and 10mM citrate buffer at pH 6.8.