Nebulized live-attenuated influenza vaccine provides protection in ferrets at a reduced dose.

Live-attenuated influenza vaccine (LAIV) is delivered to vaccine recipients using a nasal spray syringe. LAIV delivered by this method is immunogenic at current doses; however, improvements in nasal delivery might allow for significant dose reduction. We investigated LAIV vaccination in ferrets using a high efficiency nebulizer designed for nasal delivery. LAIV nasal aerosol elicited high levels of serum neutralizing antibodies and protected ferrets from homologous virus challenge at conventional (10(7)TCID(50)) and significantly reduced (10(3)TCID(50)) doses. Aerosol LAIV also provided a significant level of subtype-specific cross-protection. These results demonstrate the dose-sparing potential of nebulizer-based nasal aerosol LAIV delivery.

Aerosol vaccination induces robust protective immunity to homologous and heterologous influenza infection in mice.

Live-attenuated influenza vaccine (LAIV) delivered by large droplet intranasal spray is efficacious against infection. However, many of the large droplets are trapped in the external nares and do not reach the target nasal airway tissues. Smaller droplets might provide better distribution yielding similar protection with lower doses. We evaluated 20 and 30 µm aerosol delivery of influenza virus in mice. A 15s aerosol exposure optimally protected against homologous and heterologous influenza infection and induced a robust immune response. These results demonstrate the feasibility of nasal vaccination using aerosolized particles, providing a strategy to improve vaccine efficacy and delivery.

Human metapneumovirus establishes persistent infection in the lungs of mice and is reactivated by glucocorticoid treatment.

Human metapneumovirus (HMPV) has been identified as a worldwide agent of serious upper and lower respiratory tract infections in infants and young children. HMPV is second only to respiratory syncytial virus (RSV) as a leading cause of bronchiolitis, and, like RSV, consists of two major genotypes that cocirculate and vary among communities year to year. Children who have experienced acute HMPV infection may develop sequelae of wheezing and asthma; however, the features contributing to this pathology remain unknown. A possible mechanism for postbronchiolitis disease is that HMPV might persist in the lung providing a stimulus that could contribute to wheezing and asthma. Using immunohistochemistry to identify HMPV-infected cells in the lungs of mice, we show that HMPV mediates biphasic replication in respiratory epithelial cells then infection migrates to neuronal processes that innervate the lungs where the virus persists with no detectable infection in epithelial cells. After glucocorticoid treatment, the virus is reactivated from neural fibers and reinfects epithelial cells. The findings show that HMPV persists in neural fibers and suggest a mechanism for disease chronicity that has important implications for HMPV disease intervention strategies.

Recombinant parainfluenza virus 5 (PIV5) expressing the influenza A virus hemagglutinin provides immunity in mice to influenza A virus challenge.

Parainfluenza virus type 5 (PIV5), formerly known as simian virus 5 (SV5), is a non-segmented negative strand RNA virus that offers several advantages as a vaccine vector. PIV5 infects many cell types causing little cytopathic effect, it replicates in the cytoplasm of infected cells, and does not have a DNA phase in its life cycle thus avoiding the possibility of introducing foreign genes into the host DNA genome. Importantly, PIV5 can infect humans but it is not associated with any known human illness. PIV5 grows well in tissue culture cells, including Vero cells, which have been approved for vaccine production, and the virus can be obtained easily from the media. To test the feasibility of using PIV5 as a live vaccine vector, the hemagglutinin (HA) gene from influenza A virus strain A/Udorn/72 (H3N2) was inserted into the PIV5 genome as an extra gene between the hemagglutinin-neuraminidase (HN) gene and the large (L) polymerase gene. Recombinant PIV5 containing the HA gene of Udorn (rPIV5-H3) was recovered and it replicated similarly to wild type PIV5, both in vitro and in vivo. The HA protein expressed by rPIV5-H3-infected cells was incorporated into the virions and addition of the HA gene did not increase virus virulence in mice. The efficacy of rPIV5-H3 as a live vaccine was examined in 6-week-old BALB/c mice. The results show that a single dose inoculation provides broad and considerable immunity against influenza A virus infection.