Chimeric Pneumoviridae fusion proteins as immunogens to induce cross‐neutralizing antibody responses

Abstract

Human respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV), two members of the Pneumoviridae family, account for the majority of severe lower respiratory tract infections worldwide in very young children. They are also a frequent cause of morbidity and mortality in the elderly and immunocompromised adults. High levels of neutralizing antibodies, mostly directed against the viral fusion (F) glycoprotein, correlate with protection against either hRSV or hMPV. However, no cross‐neutralization is observed in polyclonal antibody responses raised after virus infection or immunization with purified F proteins. Based on crystal structures of hRSV F and hMPV F, we designed chimeric F proteins in which certain residues of well‐characterized antigenic sites were swapped between the two antigens. The antigenic changes were monitored by ELISA with virus‐specific monoclonal antibodies. Inoculation of mice with these chimeras induced polyclonal cross‐neutralizing antibody responses, and mice were protected against challenge with the virus used for grafting of the heterologous antigenic site. These results provide a proof of principle for chimeric fusion proteins as single immunogens that can induce cross‐neutralizing antibody and protective responses against more than one human pneumovirus.

A Pan-Pneumovirus vaccine based on immunodominant epitopes of the fusion protein

“…Multiple protein engineering strategies have been investigated to generate cross-protective or epitope-based antigens against RSV F or hMPV F. Previous attempts at grafted a single antigenic site on RSV F or hMPV F from one to another induced cross-neutralizing antibodies but very limited protection against the heterologous virus challenge, likely due to the epitopes on the backbone still dominate the immune responses (39). RHMS-1 contains multiple immunodominant epitopes of both RSV F and hMPV F in relatively equal propotions, including at least three RSV F-specific and three MPV F-specific antigenic sites.…”

“…Due to the similarities between RSV and hMPV F, researchers have tried to generate universal RSV/MPV vaccines by grafting the helix-turn-helix motif (site II) from RSV F onto hMPV F, however, this chimera induced neutralizing antibody responses only to hMPV, but not RSV (38). A similar study that grafted RSV F and hMPV F epitopes on pre-fusion and pos-fusion F proteins showed that chimeric proteins swapping either site II or site IV can induce cross-neutralizing antibodies in mice, but a challenge with pre-fusion candidates was lacking (39). For the influenza hemagglutinin (HA) protein, chimeric immunogens generated by swapping the HA head with zoonotic subtypes while retaining the conserved HA stem successfully induced antibodies targeting the subdominant HA stem (40, 41).…”

Probing Morbillivirus Antisera Neutralization Using Functional Chimerism between Measles Virus and Canine Distemper Virus Envelope Glycoproteins

“…The tools described herein provide the opportunity to identify other antigenic determinants in related morbilliviruses, for the ultimate development of pan-protective vaccines against another morbilliviruses. Such a concept has recently been exploited in the newly created Pneumoviridae family, separate from the original Paramyxoviridae family [94,95]. Thus, chimeric fusion protein consisting of respiratory syncytial virus and human metapneumovirus were shown in mice to induce cross-neutralizing immune responses [94,95].…”

Characterization of prefusion-F-specific antibodies elicited by natural infection with human metapneumovirus

“…However, reinfections among the immunocompromised and the elderly can lead to more severe disease such as bronchiolitis and pneumonia (Boivin et al, 2002; Boivin et al, 2007; Walsh et al, 2008). Although vaccines and monoclonal antibodies are in various stages of early clinical development (Biacchesi et al, 2005; Chupin et al, 2021; Cox et al, 2014; Cseke et al, 2007; Hamelin et al, 2007; Herfst et al, 2008; Huang et al, 2021; Karron et al, 2018; Levy et al, 2013; Olmedillas et al, 2018; Schuster et al, 2015; Stepanova et al, 2020; Stewart-Jones et al, 2021), there are currently no FDA-approved interventions available. To develop an effective hMPV countermeasure, it will be important to have a thorough understanding of the humoral immune response that is elicited by natural infection.…”