Recombinant measles AIK-C vaccine strain expressing heterologous virus antigens

Chimeric Measles Virus (MV/RSV), Having Ectodomains of Respiratory Syncytial Virus (RSV) F and G Proteins Instead of Measles Envelope Proteins, Induced Protective Antibodies against RSV

In our previous study, fusion (F) or glyco (G) protein coding sequence of respiratory syncytial virus (RSV) was inserted at the P/M junction of the measles AIK-C vector (MVAIK), and the recombinant measles virus induced protective immune responses. In the present study, the ectodomains of measles fusion (F) and hemagglutinin (HA) proteins were replaced with those of RSV F and G proteins, and a chimeric MV/RSV vaccine was developed. It expressed F and G proteins of RSV and induced cytopathic effect (CPE) in epithelial cell lines (Vero, A549, and HEp-2 cells), but not in lymphoid cell lines (B95a, Jurkat, and U937 cells). A chimeric MV/RSV grew similarly to AIK-C with no virus growth at 39 °C. It induced NT antibodies against RSV in cotton rats three weeks after immunization through intramuscular route and enhanced response was observed after the second dose at eight weeks. After the RSV challenge with 10⁶ PFU, significantly lower virus (10^1.4±0.1 PFU of RSV) was recovered from lung tissue in the chimeric MV/RSV vaccine group than in the MVAIK control group with 10^4.6±0.2 PFU (p < 0.001) and no obvious inflammatory pathological finding was noted. The strategy of ectodomain replacement in the measles virus vector is expected to lead to the development of safe and effective vaccines for other enveloped viruses.

Recombinant Measles AIK-C Vaccine Strain Expressing Influenza HA Protein

Recombinant measles AIK-C vaccine expressing the hemagglutinin (HA) protein of influenza A/Sapporo/107/2013(H1N1pdm) (MVAIK/PdmHA) was constructed. Measles particle agglutination (PA) and influenza hemagglutinin inhibition (HI) antibodies were induced in cotton rats immunized with MVAIK/PdmHA. Cotton rats immunized with two doses of the HA split vaccine were used as positive controls, and higher HI antibodies were detected 3 weeks after the first dose. Following the challenge of A/California/07/2009(H1N1pdm), higher viral loads (10⁷ TCID50/g) were detected in the lung homogenates of cotton rats immunized with the empty vector (MVAIK) or control groups than those immunized with MVAIK/Pdm HA (10³ TCID50/g) or the group immunized with HA split vaccine (10⁵ TCID50/g). Histopathologically, destruction of the alveolar structure, swelling of broncho-epithelial cells, and thickening of the alveolar wall with infiltration of inflammatory cells and HA antigens were detected in lung tissues obtained from non-immunized rats and those immunized with the empty vector after the challenge, but not in those immunized with the HA spilt or MVAIK/PdmHA vaccine. Lower levels of IFN-α, IL-1β, and TNF-α mRNA, and higher levels of IFN-γ mRNA were found in the lung homogenates of the MVAIK/PdmHA group. Higher levels of IFN-γ mRNA were detected in spleen cell culture from the MVAIK/PdmHA group stimulated with UV-inactivated A/California/07/2009(H1N1pdm). In conclusion, the recombinant MVAIK vaccine expressing influenza HA protein induced protective immune responses in cotton rats.

Simultaneous Administration of Recombinant Measles Viruses Expressing Respiratory Syncytial Virus Fusion (F) and Nucleo (N) Proteins Induced Humoral and Cellular Immune Responses in Cotton Rats

We previously reported that recombinant measles virus expressing the respiratory syncytial virus (RSV) fusion protein (F), MVAIK/RSV/F, induced neutralizing antibodies against RSV, and those expressing RSV-NP (MVAIK/RSV/NP) and M2-1 (MVAIK/RSV/M2-1) induced RSV-specific CD8⁺/IFN-γ⁺ cells, but not neutralizing antibodies. In the present study, MVAIK/RSV/F and MVAIK/RSV/NP were simultaneously administered to cotton rats and immune responses and protective effects were compared with MVAIK/RSV/F alone. Sufficient neutralizing antibodies against RSV and RSV-specific CD8⁺/IFN-γ⁺ cells were observed after re-immunization with simultaneous administration. After the RSV challenge, CD8⁺/IFN-γ⁺ increased in spleen cells obtained from the simultaneous immunization group in response to F and NP peptides. Higher numbers of CD8⁺/IFN-γ⁺ and CD4⁺/IFN-γ⁺ cells were detected in lung tissues from the simultaneous immunization group after the RSV challenge. No detectable RSV was recovered from lung homogenates in the immunized groups. Mild inflammatory reactions with the thickening of broncho-epithelial cells and the infiltration of inflammatory cells were observed in lung tissues obtained from cotton rats immunized with MVAIK/RSV/F alone after the RSV challenge. No inflammatory responses were observed after the RSV challenge in the simultaneous immunization groups. The present results indicate that combined administration with MVAIK/RSV/F and MVAIK/RSV/NP induces humoral and cellular immune responses and shows effective protection against RSV, suggesting the importance of cellular immunity.

Establishment of an efficient reverse genetic system of Mumps virus S79 from cloned DNA

BACKGROUND

Mumps is a common type of respiratory infectious disease caused by mumps virus (MuV), and can be effectively prevented by vaccination. In this study, a reverse genetic system of MuV that can facilitate the rational design of safer, more efficient mumps vaccine candidates is established.

METHODS

MuV-S79 cDNA clone was assembled into a full-length plasmid by means of the GeneArt™ High-Order Genetic Assembly System, and was rescued via reverse genetic technology. RT-PCR, sequencing, and immunofluorescence assays were used for rMuV-S79 authentication. Viral replication kinetics and in vivo experimental models were used to evaluate the replication, safety, and immunogenicity of rMuV-S79.

RESULTS

A full-length cDNA clone of MuV-S79 in the assembly process was generated by a novel plasmid assemble strategy, and a robust reverse genetic system of MuV-S79 was successfully established. The established rMuV-S79 strain could reach a high virus titer in vitro. The average viral titer of rMuV-S79 in the lung tissues was 2.68 ± 0.14 log₁₀PFU/g lung tissue, and rMuV-S79 group did not induce inflammation in the lung tissues in cotton rats. Neutralizing antibody titers induced by rMuV-S79 were high, long-lasting and could provide complete protection against MuV wild strain challenge.

CONCLUSION

We have established a robust reverse genetic system of MuV-S79 which can facilitate the optimization of mumps vaccines. rMuV-S79 rescued could reach a high virus titer and the safety was proven in vivo. It could also provide complete protection against MuV wild strain challenge.