RT Journal Article SR Electronic(1) A1 Aerts, Laetitia A1 Rhéaume, Chantal A1 Carbonneau, Julie A1 Lavigne, Sophie A1 Couture, Christian A1 Hamelin, Marie-Ève A1 Boivin, GuyYR 2015 T1 Adjuvant effect of the human metapneumovirus (HMPV) matrix protein in HMPV subunit vaccines JF Journal of General Virology, VO 96 IS 4 SP 767 OP 774 DO https://doi.org/10.1099/vir.0.000031 PB Microbiology Society, SN 1465-2099, AB The human metapneumovirus (HMPV) fusion (F) protein is the most immunodominant protein, yet subunit vaccines containing only this protein do not confer complete protection. The HMPV matrix (M) protein induces the maturation of antigen-presenting cells in vitro. The inclusion of the M protein into an F protein subunit vaccine might therefore provide an adjuvant effect. We administered the F protein twice intramuscularly, adjuvanted with alum, the M protein or both, to BALB/c mice at 3 week intervals. Three weeks after the boost, mice were infected with HMPV and monitored for 14 days. At day 5 post-challenge, pulmonary viral titres, histopathology and cytokine levels were analysed. Mice immunized with F+alum and F+M+alum generated significantly more neutralizing antibodies than mice immunized with F only [titres of 47±7 (P<0.01) and 147±13 (P<0.001) versus 17±2]. Unlike F only [1.6±0.5×103 TCID50 (g lung)−1], pulmonary viral titres in mice immunized with F+M and F+M+alum were undetectable. Mice immunized with F+M presented the most important reduction in pulmonary inflammation and the lowest T-helper Th2/Th1 cytokine ratio. In conclusion, addition of the HMPV-M protein to an F protein-based vaccine modulated both humoral and cellular immune responses to subsequent infection, thereby increasing the protection conferred by the vaccine., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.000031