Formulation of bovine respiratory syncytial virus fusion protein with CpG oligodeoxynucleotide, cationic host defence peptide and polyphosphazene enhances humoral and cellular responses and induces a protective type 1 immune response in mice

Abstract

Respiratory syncytial virus (RSV) is the leading cause of serious respiratory tract disease in children and calves; however, RSV vaccine development has been slow due to early observations that formalin-inactivated vaccines induced Th2-type immune responses and led to disease enhancement upon subsequent exposure. Hence, there is a need for novel adjuvants that will promote a protective Th1-type or balanced immune response against RSV. CpG oligodeoxynucleotides (ODNs), indolicidin, and polyphosphazene were examined for their ability to enhance antigen-specific immune responses and influence the Th-bias when co-formulated with a recombinant truncated bovine RSV (BRSV) fusion protein (DF). Mice immunized with DF co-formulated with CpG ODN, indolicidin, and polyphosphazene (DF/CpG/indol/PP) developed higher levels of DF-specific serum IgG, IgG1 and IgG2a antibodies when compared with DF alone, and displayed an increase in the frequency of gamma interferon-secreting cells and decreased interleukin (IL)-5 production by in vitro restimulated splenocytes, characteristic of a Th1 immune response. These results were observed in both C57BL/6 and BALB/c strains of mice. When evaluated in a BRSV challenge model, mice immunized with DF/CpG/indol/PP developed significantly higher levels of BRSV-neutralizing serum antibodies than mice immunized with the DF protein alone, and displayed significantly less pulmonary IL-4, IL-5, IL-13 and eotaxin and reduced eosinophilia after challenge. These results suggest that co-formulation of DF with CpG ODN, host defence peptide and polyphosphazene may result in a safe and effective vaccine for the prevention of BRSV and may have implications for the development of novel human RSV vaccines. INTRODUCTIONHuman respiratory syncytial virus (HRSV) is the leading cause of serious lower respiratory tract infections in infants, and almost all children will have been infected by the age of two (Glezen et al., 1986; Shay et al., 1999). Severe HRSV infection in infancy has been strongly associated with the development of asthma and allergic sensitization later in life (Sigurs et al., 1995(Sigurs et al., , 2000, and it may also cause disease in adults, especially in elderly and immunosuppressed individuals (Meyer et al., 2008). Likewise, bovine respiratory syncytial virus (BRSV) causes considerable economic loss in the cattle industry (Gershwin, 2007). BRSV and HRSV are closely related, displaying similar epidemiology and pathogenesis (Van der Poel et al., 1994), making BRSV a good model for the study of RSV vaccines (Valarcher & Taylor, 2007 , 1996). More recent evidence has suggested that the failure of the FI-RSV vaccine may also have been due to the inability of the formalin-inactivated virus to prime for CD8 + T cell responses (Srikiatkhachorn & Braciale, 1997), as well as the resultant generation of low avidity, nonprotective antibody responses (Delgado et al., 2009;Polack et al., 2002). To date, there is still no licensed vaccine against HRSV, and BRSV vaccines are only moderately effective. The...

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Importance of Endosomal Cathelicidin Degradation To Enhance DNA-Induced Chicken Macrophage Activation

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