Respiratory Syncytial Virus F Protein Adjuvanted with a Carbomer-Based Adjuvant Induces Protective Humoral Response in Mice

Carbomer-lecithin-based adjuvant Adjuplex has been shown to induce a balanced T cell response and high antibody titers with some of the viral pathogens. Here, we compared the humoral immune response in mice immunized intranasally with respiratory syncytial virus fusion (RSV-F) or glycoprotein (RSV-G) or both using Adjuplex and/or a TLR9 agonist, CpG oligodeoxynucleotide (ODN). Both the adjuvants elicited robust antibody response in mice; however, Adjuplex generated higher levels of neutralizing antibodies as compared to CpG ODN when used with RSV-F protein. Neutralizing antibody titers were associated with reduced RSV load in the lungs of immunized BALB/c mice upon intranasal challenge with the RSV A2 strain. RSV-G alone was insufficient to elicit a strong antibody response with either of the adjuvants, and combining RSV-F and RSV-G did not show any synergistic response in terms of neutralizing antibody titers; however, this combination of antigens elicited a strong mucosal immune response as measured by IgA titers specific to RSV-F and RSV-G in lung tissues. These data suggest that carbomer-based adjuvants can induce a potent and protective humoral and mucosal response when used as an adjuvant for the RSV-F subunit vaccine, and the combination of RSV-F and RSV-G with Adjuplex may further be explored for enhancing the efficacy of RSV vaccines.