Respiratory Syncytial Virus (RSV) is a member of the pneumovirus genus (family Paramyxoviridae, subfamily Pneumovirinae). RSV is an important respiratory virus of both infants and the elderly, representing an underappreciated burden on health care systems. In addition, re-infections can occur despite the presence of pre-existing immunity, suggesting that immunological memory to RSV is incomplete. To date, treatment of RSV infection is limited to the provision of supportive care and no effective vaccine is available. Although several are currently under investigation, these candidates focus upon the delivery of the F and G antigens of RSV to stimulate the immune system, rather than the internal antigens, which may provide cross protection between different subtypes of RSV. Vaccine development has been greatly hindered by the lack of an appropriate animal model in which to study vaccine efficacy and pneumovirus pathogenesis. Pneumonia virus of mice (PVM) is also a member of the Pneumovirus genus and, like RSV infection of humans, causes a bronchiolitis and fatal pneumonia in its natural host, the mouse. PVM has been proposed as an appropriate model system in which to both study pneumovirus pathogenesis and vaccine efficacy. The PVM model system was adapted to investigate a potential vaccination strategy to address the lack of an available RSV vaccine. Replication deficient recombinant adenovirus serotype 5 (rAd5) vectors were constructed which expressed the F, M and N genes of PVM J3666, in addition to a control construct, which expressed the LacZ gene of E. coli. The constructs were administered via the intranasal route to BALB/c mice and were able to elicit complete protection against a lethal dose of pathogenic PVM J3666, in both short-term experiments and in a long-term experiment, up to 20 weeks post immunisation. The protection effect elicited by the constructs was observed when administered in a single dose, and in alternative mouse strains, C3H/He-mg and C57BL/6, which had differing immunity haplotypes. The rAd5 vectors generated a PVM specific IgG humoral response to PVM and Ad5 antigen which did not correlate as the primary mediator of protection. The rAd5 candidate expressing the N gene of PVM was shown to induce IFNγ secreting T-cells. The use of a peptide library of PVM N protein determined that a specific response could be identified towards the amino acids N41-90, N81-130, N161-210 and N281-330. Thus, the PVM infection model of BALB/c mice provides an immunological platform to facilitate the study of RSV and PVM pathogenesis, immunology and vaccine development.EThOS - Electronic Theses Online ServiceMedical Research Council (Great Britain) (MRC)GBUnited Kingdo
