Evaluating PLVF Vaccine Against Shigella Keratoconjunctivitis

Male (Agouti strain) guinea pigs were purchased from the Federal State Budgetary Institution of Science “Scientific Center for Biomedical Technologies of the Federal Medical and Biological Agency”, Russia. To examine the PLVF for eye protection against virulent S. flexneri stains, groups of 10 guinea pigs (aged 3 months at the start of the experiment and weighing 275 ± 3 g) were twice immunized subcutaneously dorsally with a dose of 125 µg of vaccine at an interval of 10 days. Control animals were given saline. Ten days after the last immunization, S. flexneri keratoconjunctivitis was induced in experimental and control groups of animals by inoculation into the mucosal surface of the conjunctiva of both eyes with a suspension of a virulent strain at a dose of 2 × 10⁹ cells in 30 µL of sterile saline. Each group was inoculated with one of S. flexneri 1b, 2a, 3a, 6, and Y serotypes. Keratoconjunctivitis was assessed 7 days after challenge by visual inspection. The efficacy of PLVF was calculated by the formula: PLVF Efficacy = 100 × (Control attack rate – PLVF attack rate)/Control attack rate, where attack rate = number of infected eyes/total eyes [4 (link)].