Mucosal delivery of a vectored RSV vaccine is safe and elicits protective immunity in rodents and nonhuman primates.
Bottom Line: Because RSV infection is restricted to the respiratory tract, we compared intranasal (IN) and intramuscular (M) administration for safety, immunogenicity, and efficacy in different species.In addition, animals primed in the nose developed mucosal IgA against the F protein.In conclusion, we have shown that our vectored RSV vaccine induces potent cellular and humoral responses in a primate model, providing strong support for clinical testing.
Affiliation: ReiThera Srl , Rome, Italy (former Okairos Srl).
Respiratory Syncytial Virus (RSV) is a leading cause of severe respiratory disease in infants and the elderly. No vaccine is presently available to address this major unmet medical need. We generated a new genetic vaccine based on chimpanzee Adenovirus (PanAd3-RSV) and Modified Vaccinia Ankara RSV (MVA-RSV) encoding the F, N, and M2-1 proteins of RSV, for the induction of neutralizing antibodies and broad cellular immunity. Because RSV infection is restricted to the respiratory tract, we compared intranasal (IN) and intramuscular (M) administration for safety, immunogenicity, and efficacy in different species. A single IN or IM vaccination completely protected BALB/c mice and cotton rats against RSV replication in the lungs. However, only IN administration could prevent infection in the upper respiratory tract. IM vaccination with MVA-RSV also protected cotton rats from lower respiratory tract infection in the absence of detectable neutralizing antibodies. Heterologous prime boost with PanAd3-RSV and MVA-RSV elicited high neutralizing antibody titers and broad T-cell responses in nonhuman primates. In addition, animals primed in the nose developed mucosal IgA against the F protein. In conclusion, we have shown that our vectored RSV vaccine induces potent cellular and humoral responses in a primate model, providing strong support for clinical testing.
No MeSH data available.
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Mentions: The cotton rat model is considered to be informative for the safety and efficacy profile of HRSV vaccines because (i) the animals can be infected with clinical isolates of HRSV; (ii) the virus replicates in both the upper and lower respiratory tract; and (iii) vaccination with FI-RSV vaccine primes for ERD-like hallmarks, such as alveolitis, following RSV challenge.24 Groups of cotton rats were immunized with single IN administrations of 107, 108 and 5 × 108 vp or with single IM administrations of 5 × 107 and 5 × 108 vp of PanAd3-RSV. Another group received 107 pfu MVA-RSV IM. All groups were challenged IN with RSV, 7 weeks after vaccination. Control groups included unvaccinated animals, a group earlier infected with RSV and a group vaccinated with FI-RSV as an internal control for enhanced pulmonary pathology. All animals vaccinated IM with PanAd3-RSV developed good levels of neutralizing antibodies (nAbs = Log2 6–7), comparable to those induced by an earlier RSV infection (Figure 4a). As observed in BALB/c mice, IN vaccination elicited higher titers of nAbs (Log2 8–9) respect to IM vaccination at the same dose. In contrast, none of the animals vaccinated with MVA-RSV showed detectable levels of neutralizing antibodies 7 weeks after vaccination. As shown in Figure 4b, all vaccinated animals except one outlier in the group receiving the lowest dose IN were fully protected against viral replication in the lung. In addition, mucosal vaccination with PanAd3-RSV at doses of 108 and 5 × 108 effectively blocked RSV replication in the upper respiratory tract (Figure 4b), In contrast, although systemic vaccination strongly reduced viral replication in the nose, it did not achieve complete protection even at high doses. These data support the importance of mucosal immunity in preventing RSV infection. Interestingly, a single IM dose of MVA-RSV was also fully protective in the lung, despite the lack of induction of circulating neutralizing antibodies, suggesting a role for other immune effector mechanisms in MVA-mediated protection. We further explored the durability of the protective efficacy given by the single IN dose of 5 × 108 vp PanAd3-RSV. Three groups of cotton rats were vaccinated IN with PanAd3 and challenged 3, 7, or 12 weeks after vaccination. All animals were fully protected from infection in the upper and lower respiratory tract and showed quite stable neutralizing antibody titers over the whole observation period (Figure 4c). As expected, RSV infection in FI-RSV vaccinated cotton rats was associated with increased interstitial pneumonia (IP) and alveolitis (A) scores (Figure 4d). In contrast, animals vaccinated with PanAd3-RSV IN or IM or MVA-RSV IM showed no differences in A or IP scores when compared with controls, supporting a favorable safety profile of genetic vaccine regimes.
No MeSH data available.