Evaluation of recombinant modified vaccinia Ankara virus-based rhesus cytomegalovirus vaccines in rhesus macaques

Area of Science:

• Virology
• Immunology
• Vaccine Development

Background:

• Rhesus cytomegalovirus (RhCMV) is a significant pathogen in non-human primates, posing challenges for research and transplantation.
• Current vaccine strategies against RhCMV are limited, necessitating the development of effective immunotherapies.

Purpose of the Study:

• To evaluate the immunogenicity and protective efficacy of a novel subunit vaccine against RhCMV in a primate model.
• To assess the impact of prior priming with expression plasmids on vaccine responses.

Main Methods:

• A vaccine comprising RhCMV antigens (pp65-2, gB, IE1) delivered via modified vaccinia Ankara (MVA) was administered to rhesus macaques.
• Groups received either two MVA treatments alone or after priming with expression plasmids encoding the same antigens.
• Immune responses, including antibody titers and cellular immunity, were measured, alongside viral load reduction.

Main Results:

• Both vaccinated groups, with or without priming, developed comparable levels of anti-gB, anti-pp65-2, and neutralizing antibody responses.
• Significant pp65-2- and IE1-specific cellular immune responses were observed in vaccinated macaques.
• Similar reductions in peak plasma viral loads were noted in vaccinated groups compared to unvaccinated controls.

Conclusions:

• The rhesus-MVA-based RhCMV subunit vaccine demonstrated both immunogenicity and protective efficacy in rhesus macaques.
• The findings support further research into optimizing subunit vaccine strategies for effective Cytomegalovirus (CMV) prevention.