A Peptide Mimic of a Protective Epitope of Respiratory Syncytial Virus Selected from a Combinatorial Library Induces Virus-Neutralizing Antibodies and Reduces Viral Load In Vivo

Abstract

Respiratory syncytial virus (RSV) is the most important cause of bronchiolitis and pneumonia in infants and young children worldwide. As yet, there is no effective vaccine against RSV infection, and previous attempts to develop a formalin-inactivated vaccine resulted in exacerbated disease in recipients subsequently exposed to the virus. In the work described here, a combinatorial solid-phase peptide library was screened with a protective monoclonal antibody (MAb 19) to identify peptide mimics (mimotopes) of a conserved and conformationally-determined epitope of RSV fusion (F) protein. Two sequences identified (S1 [HWYISKPQ] and S2 [HWYDAEVL]) reacted specifically with MAb 19 when they were presented as solid-phase peptides. Furthermore, after amino acid substitution analyses, three sequences derived from S1 (S1S [HWSISKPQ], S1K [KWYISKPQ], and S1P [HPYISKPQ]), presented as multiple antigen peptides (MAPs), also showed strong reactivity with MAb 19. The affinity constants of the binding of MAb 19, determined by surface plasmon resonance analyses, were 1.19 × 109 and 4.93 × 109 M−1 for S1 and S1S, respectively. Immunization of BALB/c mice with these mimotopes, presented as MAPs, resulted in the induction of anti-peptide antibodies that inhibited the binding of MAb 19 to RSV and neutralized viral infection in vitro, with titers equivalent to those in sera from RSV-infected animals. Following RSV challenge of S1S mimotope-immunized mice, a 98.7% reduction in the titer of virus in the lungs was observed. Furthermore, there was a greatly reduced cell infiltration in the lungs of immunized mice compared to that in controls. These results indicate the potential of peptide mimotopes to protect against RSV infection without exacerbating pulmonary pathology.

Molecular mimetics of polysaccharide epitopes as vaccine candidates for prevention of Neisseria meningitidis serogroup B disease

“…This approach has the greatest utility when the nominal antigen is toxic or di¤cult to purify (i.e. the lipooligosaccharide of Neisseria gonorrhoeae [87]) or when it is desirable to direct the immune response to a limited number of epitopes (see for example [74,82]). Table 1 summarizes reports from the literature of peptide and anti-idiotype antibody mimetics of carbohydrate structures.…”

Characterization of Murine Coronavirus Neutralization Epitopes with Phage-Displayed Peptides

“…Recently, Bastien et al (1997) reported the induction of a protective immune response by immunizing BALB/c mice with a recombinant phage expressing a protective epitope of human respiratory syncytial virus that had been previously identified with synthetic peptides. Also, other authors have reported the induction of protection by immunization with synthetic peptides that are homologous to the peptides borne by the selected phage (Chargelegue et al, 1998;Steward et al, 1995;Stoute et al, 1995). Our study represents an example of the successful use of phage-displayed peptide libraries for epitope characterization and emphasizes for the first time the possibility of a direct evaluation of protective immune responses induced by the selected peptide displayed by a phage carrier.…”

Mimotopes: realization of an unlikely concept

“…Mimotopes may also be the key to the development of a fully synthetic vaccine for respiratory syncytial virus (RSV). An effective mimotope that induces neutralizing activity has been described (Chargelegue et al, 1997(Chargelegue et al, , 1998Hsu et al, 1999) for RSV fusion protein. In combination with an equally effective linear peptide that mimics antigenic sites of RSV-G protein , a highly effective synthetic vaccine may be possible.…”

“…Subsequent reports confirmed this and described additional mimotopes. In the case of respiratory syncytial virus fusion protein, functional mimotopes were described by Chargelegue et al (1997Chargelegue et al ( , 1998 that competed with the 'template' neutralizing antibody. When used in a vaccine the mimotope induced neutralizing activity in animals and protected laboratory animals against infection.…”

“…It took, however, almost 10 years before the first mimotopes (as defined above) were reported. Amplifying the initial concept (highthroughput screening and peptide libraries; Geysen et al, 1986), molecules have been constructed that mimic discontinuous binding sites and carry some of the functions of native molecules (van Amerongen et al, 1992;Oldenburg et al, 1992;Balass et al, 1993;Hoess et al, 1993;Westerink et al, 1995;Steward et al, 1995;Valadon et al, 1996;Chargelegue et al, 1997Chargelegue et al, , 1998Zhang et al, 1997;Phalipon et al, 1997;D'Mello et al, 1997;Pincus et al, 1998;Kieber-Emmons, 1998;Luo et al, 1998;Kieber-Emmons et al, 1999;De Bolle et al, 1999;Scala et al, 1999). Thus it appears that peptides or peptide-like molecules can be defined in a generic fashion to form the basis for fully synthetic vaccines, synthetic diagnostic reagents, new drugs and molecules applicable in food and non-food industry.…”