In Vitro Evaluation of Effect of Storage Time on Immunogenicity of the 10-Valent Pneumococcal Conjugate Vaccine Using Baby Rabbit Complement & HL-60 Cells

Abstract

Background: The efficacy and effectiveness of a vaccine is influenced by several factors including storage duration. Additionally, vaccines may be sufficiently administered but functionality of antibody generated may be hampered with by other factors such as nutritional status of the patient. As such, one of the ways of assessing vaccine efficacy is assessing the functionality of the antibodies generated. The 10v-PCV is a highly effective vaccine used to prevent invasive pneumococcal diseases in children. However, here in Kenya, cases of pneumococcal diseases are high and challenging to treat. This study thus aimed to evaluate the effect of storage of PCV-10 storage time on the functionality of Abs generated.

Methodology; An in vitro experimental research design was employed for this study. opsonophagocytic activity assay using HL-60 Cells & Baby rabbit complement was used to assess whether or not the Pneumococci Serotype IgG antibodies elicited following administration with 10v-PCV vaccine are functional. Only 10v-PCV vaccine with same production date were procured. Twenty experimental rabbits of same gender were procured and used injected intraperitoneally with 3 doses of 100µl (0.34g) of 10v-PCV vaccine after every four weeks. Antibody functionality was then assessed using the opsonophagocytic activity assay method.

Results: An average of 28.9% of pneumococcus exposed to the vaccine-induced secreted antibodies were killed by the pneumococcal IgG antibody. The highest percentage of number of bacteria killed was achieved after the 3^rd dose of vaccination. There was no significant influence of storage duration on opsonophagocytic activity of generated antibodies.

Conclusion: Storing of 10v-PCV vaccine up to 12 weeks does not significantly affect the opsonophagocytic activity of pneumococcal IgG antibodies.