Protection of mice against Human respiratory syncytial virus by wild-type and aglycosyl mouse–human chimaeric IgG antibodies to subgroup-conserved epitopes on the G glycoprotein

Abstract

Monoclonal antibodies (mAbs) to conserved epitopes on the G glycoprotein of human respiratory syncytial virus (HRSV) subgroup A fail to neutralize the virus in cell culture in the absence of complement, but are protective in rodent models of infection. They may have potential as prophylactic agents in human infants. In order to investigate the role of Fc-dependent pathways in protection by one such antibody, 1C2, the V H and V L genes were isolated by RT-PCR and assembled with human k light-chain and human c1 heavy-chain constant-region genes to form two mouse-human chimaeras, which were expressed in NS0 cells. One of the chimaeras carried a wild-type c1 chain, whilst the other had an aglycosyl mutation in the C H 2 domain rendering the antibody defective in complement activation and FccR binding. Whilst both chimaeric antibodies exhibited similar avidity for HRSV in ELISA, only the fully glycosylated wild type was capable of neutralizing the virus in the presence of complement. In mice passively immunized with either murine or wild-type c1 chimaeric antibody, no virus could be recovered from the lungs 4 days after intranasal inoculation of HRSV. In mice immunized with the aglycosyl c1 chimaera, however, virus was present in the lungs following challenge, although virus titres were significantly reduced compared with controls (P<0?005). These results indicate that the protective effect of this antibody is mediated by both Fc-dependent and Fc-independent pathways.

Treatment with respiratory syncytial virus G glycoprotein monoclonal antibody or F(ab′)2 components mediates reduced pulmonary inflammation in mice

“…Two days after mAb 131-2G treatment, the viral load in mice treated with intact mAb was significantly (P,0.048) reduced compared with lung titres in F(ab9) 2 -treated mice which showed no significant reduction compared with nIgtreated mice. The ability of this non-neutralizing antibody to prevent virus replication in vivo is consistent with earlier observations and reports using other non-neutralizing RSV G protein antibodies (Corbeil et al, 1996;PlotnickyGilquin et al, 1999;Mekseepralard et al, 2006). The results suggest that mAb 131-2G may mediate virus clearance through an ADCC mechanism.…”

“…In these previous studies, treatment with the same mAb in complement-deficient mice or treatment with mAb F(ab9) 2 fragments did not confer complete protection, suggesting that protection by the intact mAb involved both Fc-dependent pathways and the complement system (Corbeil et al, 1996). Other studies investigating a different subgroup A-specific anti-RSV G mAb (1C2) that recognized a similar region on the G protein, and a related mouse-human chimeric mAb (c1 1C2), showed a level of protection against RSV infection when these antibodies were administered prophylactically to BALB/c mice (Mekseepralard et al 2006). In these studies, virus replication was minimally inhibited in mice treated with an aglycosyl chimeric mAb defective in complement activation, FccR binding and, therefore, ADCC activation, leading to the conclusion that protection from RSV infection was mediated by both Fc-dependent and Fc-independent mechanisms (Mekseepralard et al, 2006).…”

“…Others have demonstrated that non-neutralizing anti-RSV G protein mAbs are sufficient to protect against RSV infection in mouse models (Corbeil et al, 1996;Plotnicky-Gilquin et al, 1999;Mekseepralard et al, 2006). For example, it was reported that passive administration of a non-neutralizing mAb (18A2B2) against the central conserved region of RSV G protein subgroup A protected mice from RSV infection (Corbeil et al 1996).…”

“…Other studies investigating a different subgroup A-specific anti-RSV G mAb (1C2) that recognized a similar region on the G protein, and a related mouse-human chimeric mAb (c1 1C2), showed a level of protection against RSV infection when these antibodies were administered prophylactically to BALB/c mice (Mekseepralard et al 2006). In these studies, virus replication was minimally inhibited in mice treated with an aglycosyl chimeric mAb defective in complement activation, FccR binding and, therefore, ADCC activation, leading to the conclusion that protection from RSV infection was mediated by both Fc-dependent and Fc-independent mechanisms (Mekseepralard et al, 2006). In the studies cited here, F(ab9) 2 fragments of mAb 131-2G did not facilitate virus clearance, suggesting that ADCC was involved in viral clearance from the lungs of RSV-infected mice.…”

Potent High-Affinity Antibodies for Treatment and Prophylaxis of Respiratory Syncytial Virus Derived from B Cells of Infected Patients

“…Murine Abs to the central conserved region of the G protein have shown efficacy in prophylactic mouse (29) and cotton rat models (30). A recent report showed that such a murine mAb delivered postinfection decreased both viral replication and the associated pulmonary inflammatory response (31).…”