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Influenza Other Respir Viruses. 2013 Nov;7(6):1227-36. doi: 10.1111/irv.12112. Epub 2013 Apr 10.

A virosomal respiratory syncytial virus vaccine adjuvanted with monophosphoryl lipid A provides protection against viral challenge without priming for enhanced disease in cotton rats.

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Department of Medical Microbiology, Molecular Virology Section, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.



Non-replicating respiratory syncytial virus (RSV) vaccine candidates could potentially prime for enhanced respiratory disease (ERD) due to a T-cell-mediated immunopathology, following RSV infection. Vaccines with built-in immune response modifiers, such as Toll-like receptor (TLR) ligands, may avoid such aberrant imprinting of the immune system.


We developed reconstituted RSV envelopes (virosomes) with incorporated TLR4 ligand, monophosphoryl lipid A (RSV-MPLA virosomes). Immune responses and lung pathology after vaccination and challenge were investigated in ERD-prone cotton rats and compared with responses induced by live virus and formaldehyde-inactivated vaccine (FI-RSV), a known cause of ERD upon RSV challenge.


Vaccination with RSV-MPLA virosomes induced higher levels of virus-neutralizing antibodies than FI-RSV or live virus infection and provided protection against infection. FI-RSV, but not RSV-MPLA virosomes, primed for increases in expression of Th2 cytokines IL-4, IL-5, IL-13, and Th1 cytokine IL-1b, 6 hour-5 days after infection. By contrast, RSV-MPLA virosomes induced IFN-γ transcripts to similar levels as induced by live virus. Animals vaccinated with FI-RSV, but not RSV-MPLA virosomes showed alveolitis, with prominent neutrophil influx and peribronchiolar and perivascular infiltrates.


These results show that RSV-MPLA virosomes represent a safe and immunogenic vaccine candidate that warrants evaluation in a clinical setting.


Adjuvant; cotton rat; enhanced respiratory disease; monophosphoryl lipid A; respiratory syncytial virus; vaccine; virosomes

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