Evaluation of synthetic infection-enhancing lipopeptides as adjuvants for a live-attenuated canine distemper virus vaccine administered intra-nasally to ferrets

Department of Virology, Erasmus MC, University Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Vaccine (Impact Factor: 3.62). 06/2012; 30(34):5073-80. DOI: 10.1016/j.vaccine.2012.05.079
Source: PubMed


Inactivated paramyxovirus vaccines have been associated with hypersensitivity responses upon challenge infection. For measles and canine distemper virus (CDV) safe and effective live-attenuated virus vaccines are available, but for human respiratory syncytial virus and human metapneumovirus development of such vaccines has proven difficult. We recently identified three synthetic bacterial lipopeptides that enhance paramyxovirus infections in vitro, and hypothesized these could be used as adjuvants to promote immune responses induced by live-attenuated paramyxovirus vaccines.
Here, we tested this hypothesis using a CDV vaccination and challenge model in ferrets. Three groups of six animals were intra-nasally vaccinated with recombinant (r) CDV(5804P)L(CCEGFPC) in the presence or absence of the infection-enhancing lipopeptides Pam3CSK4 or PHCSK4. The recombinant CDV vaccine virus had previously been described to be over-attenuated in ferrets. A group of six animals was mock-vaccinated as control. Six weeks after vaccination all animals were challenged with a lethal dose of rCDV strain Snyder-Hill expressing the red fluorescent protein dTomato.
Unexpectedly, intra-nasal vaccination of ferrets with rCDV(5804P)L(CCEGFPC) in the absence of lipopeptides resulted in good immune responses and protection against lethal challenge infection. However, in animals vaccinated with lipopeptide-adjuvanted virus significantly higher vaccine virus loads were detected in nasopharyngeal lavages and peripheral blood mononuclear cells. In addition, these animals developed significantly higher CDV neutralizing antibody titers compared to animals vaccinated with non-adjuvanted vaccine.
This study demonstrates that the synthetic cationic lipopeptides Pam3CSK4 and PHCSK4 not only enhance paramyxovirus infection in vitro, but also in vivo. Given the observed enhancement of immunogenicity their potential as adjuvants for other live-attenuated paramyxovirus vaccines should be considered.

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Available from: Rik de Swart, Aug 05, 2015
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    • "Synthetic lipopeptides have also been examined as adjuvants (101). Pam3CSK4 showed promise for live-attenuated vaccines as it enhanced infection of paramyxoviruses in vitro and in vivo (102) as well as RSV infection in multiple cell types. However, the related lipopeptides Pam-Cys-SK4 and PHCSK4 did not activate TLR signaling although they were able to enhance the binding and infection of APCs by the virus, even though RSV primarily targets airway epithelial cells (103). "
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    • "Ferrets have also been employed successfully in studies on measles virus, a related paramyxovirus, using canine distemper virus (CDV) as a model organism (Kauffman et al., 1982; Mehta & Thormar, 1979). It has been suggested that they may be valuable for assessing attenuated paramyxovirus vaccine candidates (Nguyen et al., 2012). Here we demonstrate that ferrets produce a mumps infectionspecific serum antibody response and a cytokine response consistent with infection, detectable in PBMCs. "
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    ABSTRACT: Development of live-attenuated human respiratory syncytial virus (HRSV) vaccines has proven difficult. Several vaccine candidates were found to be over-attenuated and displayed limited immunogenicity. We recently identified three synthetic cationic lipopeptides that enhanced paramyxovirus infections in vitro. The infection enhancement proved to be mediated by enhanced virus binding to target cells. We hypothesized these lipopeptides could be used as adjuvants to promote immune responses induced by live-attenuated paramyxovirus vaccines. Here this hypothesis was tested in a vaccination and challenge model in cotton rats, using a previously described recombinant live-attenuated candidate HRSV vaccine lacking the gene encoding the G glycoprotein (rHRSVΔG). Surprisingly, intranasal vaccination of cotton rats with rHRSVΔG formulated in infection-enhancing lipopeptides resulted in reduced virus loads in nasopharyngeal lavages, reduced seroconversion levels and reduced protection from wild-type HRSV challenge. In conclusion, we were unable to demonstrate the feasibility of lipopeptides as adjuvants for a candidate live-attenuated HRSV vaccine.
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