Comparison of the protective effect of human respiratory syncytial virus Pre-F protein combined with different adjuvants in BALB/c mice.

INTRODUCTION

Human respiratory syncytial virus (HRSV) has a high disease burden in infants and elderly individuals. In this study, the adjuvants AlOH, AlOH+CpG and BFA03 were used to compare the protective effect of HRSV prefusion protein (Pre-F) in BALB/c mice.

METHODS

We divided BALB/c mice into three experimental groups (Pre-F+AlOH+CpG, Pre-F+AlOH, and Pre-F+BFA03) and three adjuvant control groups (AlOH+CpG, AlOH, and BFA03). After two intramuscular immunizations, we measured serum neutralizing antibody titers and quantified the numbers of IFN-γ- and IL-4-secreting lymphocytes. After viral challenge, we monitored body weight changes, determined lung viral loads (Ct values), and scored lung pathological damage.

RESULTS

The mice in the experimental groups exhibited high titres of neutralizing antibodies and increased numbers of IFN-γ- and IL-4-secreting lymphocytes. The mice began to regain weight on the third day after challenge, but the mice in the adjuvant groups continued to lose weight. The mice immunized with Pre-F+BFA03 elicited the highest neutralizing antibody titre (1716), the lowest viral load in the lung, and milder pathological damage. The mice immunized with Pre-F+AlOH had the most severe lung pathological injury (score: 2.83) and the highest viral load in the lung (Ct value: 32.2). Compared with the BFA03 adjuvant, the AlOH adjuvant induced a Th2-biased humoral immune response in mice. The Pre-F+AlOH+CpG group had the least pathological damage in the lung (score 2.16), and the ability to induce neutralizing antibodies and cellular immune responses was comparable with that of the BFA03 adjuvant.

DISCUSSION: These findings indicate that Pre-F protein combined with AlOH+CpG or BFA03 adjuvant provided similar protection in mice and both were superior to the AlOH adjuvant, providing a reference for adjuvant selection and formulation strategies in HRSV Pre-F protein vaccine development.