Protection of Cotton Rats against Human Respiratory Syncytial Virus by Vaccination with a Novel Chimeric FG Glycoprotein

Abstract

SUMMARYThe cotton rat model of experimental human respiratory syncytial virus (RSV) infection was used to study the efficacy of FG, a novel chimeric glycoprotein which was expressed in insect cells using a baculovirus vector. FG contained the extracellular regions of the F (fusion) and G (attachment) glycoproteins of RSV. Vaccination with FG resulted in induction of neutralizing antibody and was correlated with protection of lung tissue from RSV challenge against both serogroup A and B virus strains. Both crude FG taken from supernatants of insect cells and affinity-purified FG were immunogenic and active against RSV. FG vaccination was effective by three routes of administration, following a single dose, and when administered with different adjuvants. INTRODUCTIONHuman respiratory syncytial virus (RSV), a paramyxovirus, is the major cause of severe lower respiratory disease in children under 1 year of age (Parrott et al., 1973). Previous attempts to produce a safe and effective vaccine against RSV have failed. A formalin-inactivated virus vaccine tested approximately 20 years ago failed to prevent infection, and actually increased the severity of disease upon subsequent RSV infection (Kim et al., 1969). Temperature-sensitive mutants have also failed as vaccines because of either insufficient attenuation or loss of immunogenicity (Kim et al., 1971 ;Wright et al., 1982).Work using purified RSV proteins from RSV-infected cells (Walsh et al., 1987), or vaccination with vaccinia virus recombinants containing the F (fusion) or G (attachment) glycoprotein in mice (Stott et al., 1986;Wertz et al., 1987) or rats (Olmsted et al., 1986; resulted in the induction of neutralizing antibody and in a significant reduction in the replication of RSV in lung tissue. Our previous work (Wathen et al., 1989a) demonstrated that vaccination with a secreted form of the F glycoprotein (Ft), expressed in insect cells using a baculovirus vector also resulted in induction of neutralizing antibody, and in significant reduction in the titre of RSV recovered from cotton rats. The Ft glycoprotein contained the majority of the extracellular region of F (amino acids 1 to 489), but was missing the anchor region of the glycoprotein.In the preceding paper (Wathen et al., 1989b), we described a novel chimeric glycoprotein of RSV termed FG, which was expressed in insect cells using a baculovirus vector. This glycoprotein contained the signal and extracellular regions of the F glycoprotein linked to the extracellular region of the G glycoprotein. We now report that vaccination of cotton rats with the chimeric FG glycoprotein resulted in the induction of high titres of neutralizing antibody and in protection from challenge with either serogroup A or B strains of RSV. In addition, we describe the effect of route and frequency of vaccination, and the use of adjuvants on the efficacy of FG.

Use of synthetic peptides to locate neutralizing antigenic domains on the fusion protein of respiratory syncytial virus

“…For this latter analysis, most studies used recombinant viruses expressing the F protein. It has been well demonstrated that vaccination with such protein results in the induction of neutralizing antibodies and a significant reduction in the titre of RS virus in lung tissue after challenge (Brideau et al, 1989;Olmsted et al, 1986;Stott et al, 1987;Wertz et al, 1987). The results reported here show that defined synthetic peptides also induce neutralizing antibodies and could be used as an alternative in selectively exploring the immunogenicity of the F protein.…”

Protection of cotton rats against human parainfluenza virus type 3 by vaccination with a chimeric FHN subunit glycoprotein

“…2) suggest FHN-vaccinated animals are responding to both the F and HN portions. In our previous work using the FG chimeric glycoprotein for control of RSV infection, we had shown that the majority of the anti-FG antibody response was to the F portion of FG (Brideau et al, 1989). Host response to more than one major viral glycoprotein target may be needed to control paramyxovirus infections effectively.…”

“…Lysates and individual glycoproteins were preadsorbed to microtitre plates prior to assay. The assay was performed as previously described (Brideau et al, 1989). ELISA titres were expressed as the reciprocal of the dilution of sera giving 50 % of the maximum binding activity.…”

“…ELISA titres were expressed as the reciprocal of the dilution of sera giving 50 % of the maximum binding activity. Neutralizing antibody titres were measured for individual sera against PIV-3-infected HEp-2 cell cultures as previously described (Brideau et al, 1989) and were expressed as the reciprocal of the highest dilution that reduced viral c.p.e, by 50 % relative to non-neutralized controls.…”

“…Our previous work with an experimental subunit vaccine termed FG, which is a chimeric glycoprotein containing both the F and G glycoproteins of RSV, prepared in insect cells using a baculovirus vector system, showed complete protection against RSV challenge in cotton rats (Brideau et al, 1989;Wathen et al, 1991). In the preceding paper (Lehman et al, 1993), we describe the construction of a chimeric FHN glycoprotein consisting of a truncated form of the F glycoprotein linked to a truncated form of the HN glycoprotein of PIV-3, as well as secreted forms of the individual glycoproteins.…”