A Built-In CpG Adjuvant in RSV F Protein DNA Vaccine Drives a Th1 Polarized and Enhanced Protective Immune Response

Area of Science:

• Immunology
• Vaccinology
• Virology

Background:

• Human respiratory syncytial virus (RSV) is a major cause of severe respiratory infections in children.
• Currently, no licensed vaccine is available for RSV prevention.

Purpose of the Study:

• To investigate the adjuvant effect of C-Class CpG oligodeoxynucleotides (CpG-C) on a plasmid DNA vaccine encoding the RSV fusion (F) glycoprotein.
• To evaluate the impact of CpG-C incorporation on vaccine-induced immune responses and protection against RSV challenge.

Main Methods:

• Plasmid DNA vaccines encoding RSV F glycoprotein were constructed with either five or 20 copies of CpG-C motifs.
• BALB/c mice were immunized with these DNA vaccines, followed by RSV challenge.
• Humoral (antibody) and cellular (T-cell) immune responses, as well as pulmonary pathology and virus replication, were assessed.

Main Results:

• CpG-C motif incorporation significantly enhanced serum binding and virus-neutralizing antibody titers.
• Vaccination with CpG-modified DNA vaccines, particularly the 20-copy version, promoted a Th1-biased immune response.
• CpG-modified vaccines reduced pulmonary pathology, viral replication, and weight loss following RSV challenge.

Conclusions:

• CpG-C motifs act as effective built-in adjuvants in DNA vaccines targeting the RSV F glycoprotein.
• This strategy significantly improves vaccine efficacy against RSV infection by modulating immune responses and conferring protection.