Next-Generation Single-Cycle RSV Vaccines With Increased Interferon Induction Yield Robust Syste

10 Apr 20264 min read0 viewsJournal Feed

GIST

We previously demonstrated that vaccination with RSV-Mnull, a prototype single-cycle live vaccine lacking the matrix (M) gene, generated anti-viral serum IgG and memory T cell responses, and reduced challenge virus shedding and pulmonary dysfunction in mice. Here we further characterized the response to RSV-Mnull, and designed and tested second generation Mnull vaccines.

In mice, prime-boost vaccination with RSV-Mnull generated pre-fusion (preF) and attachment protein (G) -specific serum IgG and lung IgA, and protected from lung pathology, showing that a single-cycle live vaccine was effective in this model. In an effort to enhance efficacy for future human application, second generation Mnull vaccines were designed, in which nonstructural protein 1 (NS1), a known interferon (IFN) antagonist, was relocated to reduce expression.

In addition, the G or F genes were moved to the first genome position (RSV-Mnull/G1 and RSV-Mnull/F1 respectively). In vitro, RSV-Mnull/G1 and RSV-Mnull/F1 showed reduced NS1 levels and increased IFN-β induction, whereas IFN-λ levels were not affected.

Viruses with relocated NS1 also displayed enhanced anti-viral state in uninfected cells.

Clinical Editorial

Strategic aim and study context

The work builds on prior demonstration that RSV-Mnull, a single-cycle live RSV vaccine lacking the M gene, elicited anti-viral serum IgG and memory T cell responses and reduced challenge virus shedding and pulmonary dysfunction in mice.
The current report characterizes responses to RSV-Mnull and presents second-generation Mnull vaccines designed to improve human applicability.

Study design and vaccine constructs

Simultaneously, G or F genes were repositioned to the first genome position, yielding RSV-Mnull/G1 and RSV-Mnull/F1 constructs.

The researchers evaluated prime-boost immunization with RSV-Mnull in mice, assessing both systemic and mucosal antibody responses and protection against lung pathology.
They engineered second-generation Mnull vaccines by relocating nonstructural protein 1 (NS1), an IFN antagonist, to reduce its expression.
In vitro analyses compared NS1 abundance and interferon induction across constructs, noting decreased NS1 and increased IFN-β with relocated NS1, while IFN-λ remained unchanged.

Immunogenicity and mucosal responses

Mnull/G1 raised higher anti-G serum antibodies, whereas Mnull/F1 favored an increased anti-preF:anti-G IgG ratio.

RSV-Mnull/G1 and RSV-Mnull/F1 provoked distinct antibody profiles compared with the prototype.
Wildtype RSV elicited higher lung IgA than RSV-Mnull; however, NS1 relocation accelerated early IgA production and restored IgA to wildtype-like levels.
Overall, the data indicate that genomic positioning of NS1, G, and F modulates both antigen presentation dynamics and the timing of humoral responses.

Protective efficacy and model limitations

All vaccine variants generated neutralizing antibodies in vitro and conferred protection against a high-dose challenge with wildtype RSV.
In terms of mitigating lung pathology, neither RSV-Mnull/G1 nor RSV-Mnull/F1 showed clear superiority over the original RSV-Mnull prototype within the constraints of the mouse model used, suggesting model limitations rather than ineffectiveness of the constructs.
The single-cycle approach maintained protective potential despite reduced replication, aligning with the goal of a safe, efficacious live vaccine platform.

Context, interpretation, and practical relevance

The study underscores that altering genome organization—specifically relocating NS1 and repositioning G or F—modulates interferon responses, antibody specificities, and the timing of mucosal immunity.
Enhanced anti-G or anti-F mucosal/serum responses did not translate into markedly superior protection against pathology within the tested model, highlighting the complexity of correlates of protection and the potential need for optimization beyond immune readouts.
The authors position RSV-Mnull-based single-cycle vaccines as a promising platform for safe, efficacious immunization, with the genomic arrangement offering a lever to tune immune outcomes.