Since there is an urgent need for development of vaccines and antiviral agents to combat influenza pandemics, this study aimed to develop influenza virus-like particles (VLPs) and aptamers targeting the virus particles as vaccine and antiviral agent candidates. Influenza VLPs containing three structural proteins of hemagglutinin (HA), neuraminidase (NA) and matrix 1 (M1) derived from influenza A/Hong Kong/01/2009 (H1N1) virus (HK/01) were constructed using a Bac-to-Bac baculovirus expression system. The expressed VLPs were purified by sucrose density gradient ultracentrifugation and characterized by Western blotting analysis and transmission electron microscopy. The immune responses and protective efficacy induced by VLPs were compared with those elicited by the clinically used Panenza vaccine in BALB/c mouse model. The results showed that two-dose vaccination with both VLP and the Panenza vaccine could confer complete protection. Single-dose vaccination with VLP could also provide 100% protection against lethal virus challenge, whereas single dose of an equal amount (based on HA content) of the Panenza vaccination just provided incomplete protection (67% survival rate) against the lethal virus challenge. Compared to the Panenza vaccination, the VLP vaccination could induce higher and broader antibody responses and higher viral specific T help (Th) cell and cytotoxic T lymphocyte (CTL) responses. Notably, a novel finding in this study is that the VLP vaccination could induce antibodies to inhibit virus release from infected MDCK cells, although the underlined mechanism needed to be further studied. These results indicated that influenza VLP might be a more effective and safe vaccine candidate which could be developed into an alternative vaccine for the control of epidemic and pandemic influenza in the future. To develop aptamers as antiviral agents against influenza, I sought to use influenza VLPs as target for ssDNA aptamer selection. After 11 rounds of selection using the systemic evolution of ligandsby exponential enrichment (SELEX),the recovered DNA molecules were PCR-amplified, gel purified and cloned into pCR-Blunt II TOPO vector for sequencing. The sequencing results showed that one aptamer Va-1 was markedly enriched, which was accounted for 59% (13/22) of the selected aptamers. Compared to the other non-enriched aptamers, the enriched aptamer Va-1 showed the highest binding affinity to the UV inactivated influenza HK/01 virus. It was also shown that the aptamer Va-1 specifically bound to the HK/01 stain while it could not bind other respiratory viruses even the PR8 strain within the H1N1 subtype. It was further demonstrated that the aptamer Va-1 could only bind to NA protein in a dose-dependent manner but not bind to HA and M1 proteins. Unfortunately, the selected aptamer did not show any antiviral effects. However, it may be potentially developed into a diagnostic and analytic agent because its binding activity was comparable with that of the commercial anti-NA antibody. In conclusion, the influenza VLPs may be a promising vaccine candidate for the control of influenza virus infection and the selected aptamer may be potentially developed into an alternative tool for influenza virus detection. / published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

The control of foodborne pathogens especially Salmonella and Campylobacter are of great concern to the commercial poultry industry. The control of these pathogens could be essential in the reduction of foodborne illness and deaths related to eggs and poultry meat. Previous studies have found that the presence or disappearance of Salmonella or Campylobacter is linked to various environmental and management-based factors, of which include vaccines used in the industry. Presently, we evaluated the effect of the infectious bronchitis virus (IBV) vaccine on the incidence of Salmonella or Campylobacter prevalence in broiler chicks. In the current study, a high vaccine dosage of IBV vaccine was associated with an increase the prevalence of Campylobacter during the first two weeks of age. Although in a previous study a high vaccine dose of IBV was linked in to increased prevalence of Salmonella, this was not seen in our study. In a subsequent trial, we also evaluated the potential cross-protection against three Salmonella serotypes of two-previously formulated vaccines when used in various dosage combinations. The combination vaccine was effective in reducing shedding of S. Enteritidis however reduction of S. Typhimurium and S. Hadar were not seen consistently. The vaccines were also shown to not significantly affect the body weights of the birds. Vaccines have been an essential component in the control of diseases within flocks in the commercial poultry industry. Ensuring the uniform application of IBV vaccine could help prevent and/or reduce the prevalence of Campylobacter in broiler flocks. The combination vaccine was effective against one serotype of Salmonella but further trials are needed to complete evaluate its potential as a vaccine that could be used in the poultry industry.

No description available.

No safe and effective vaccine exists against respiratory syncytial virus (RSV), the main viral cause of lower respiratory tract infections in young children. Proteosome-based adjuvants, derived from the outer membrane proteins (OMP) of Neisseria species are potent inducers of mucosal and systemic immunity in humans and animals. RSV subunit vaccines based on enriched RSV proteins (eRSV) were formulated with proteosomes (Pro) or its S. flexneri LPS-supplemented derivative, Protollin (Prl). Administered intranasally (IN) in BALB/c mice, the vaccines elicited systemic and mucosal RSV-specific antibodies and fully protected against RSV challenge without enhanced pulmonary pathology or evidence of a Th2-biased response (eg: eosinophil infiltation or antigen-specific 1L-5 production by restimulated splenocytes or lung cells). Restimulation of cells from Prl-eRSV immunized mice elicited F peptide-specific CD8+ T cells producing IFNgamma and supernatant IFNgamma, TNFalpha, 1L-2 and IL-10. The Prl-eRSV vaccine was also studied in C57Bl/6 mice, to exploit the TLR2, TLR4 and MyD88-deficient (-/-) animals available on this background. Protection was significantly impaired in both TLR4-/- and MyD88 -/- mice, but not in TLR2 -/- mice following Prl- eRSV immunization and challenge. These studies revealed a role for the LPS component of Protollin in both initial (innate) cytokine release as well as dendritic cell maturation and Th1 polarization. Although antibody levels were sustained in MyD88-/- mice, the IgG1/IgG2a ratio was markedly higher in the absence of this pathway. The MyD88-/- mice also displayed elevated levels of pulmonary eosinophils following challenge, with concomitant reduction of neutrophils compared to wt mice. Using CD1d-iNKT cell-deficient mice (CD1-/-) in our BALB/c model, we also identified a significant role for the lipid component of both the Pro- and Prl-based vaccines. Responses to both vaccines in CD1-/- animals elicited lower antibody titers and reduced restimulated splenocyte supernatant cytokines (IFNgamma, IL-17 and IL-10), with concomitant augmentation of neutrophil recruitment (Prl only). Pro- and Prl-eRSV vaccines may therefore exert their powerful adjuvant effects by exploiting both CD1d-iNKT and, in the case of the Prlbased formulations the TLR4-MyD88-dependant signalling pathway. These pathways not only promote stronger Th1 immune responses but also act to control pulmonary eosinophil (MyD88-dependent) and neutrophil (MyD88 and CD1d-NKT-dependent) recruitment in a murine RSV challenge model.

No description available.

No description available.

As the number of drug-resistant malaria parasites continues to grow, pressure is increasing to find an effective, cross-protective, multi-valent malaria vaccine (32). Expression library immunisation is an un-biased screening technique that leads to the identification of novel, protective antigens that can be administered as components of a multivalent DNA vaccine (9, 50, 75, 86, 92). Here, a P. c. adami DS expression library has been evaluated as a malaria vaccine in mice, and several subpools of cross-protective plasmids have been identified. Upon vaccination with these plasmid subpools, mice demonstrate significantly lower mean cumulative parasitemia values than control vaccinated mice, when challenged with avirulent heterologous P. c. adami DK parasites. These cross-protective responses correlate with the induction of opsonizing antibodies against infected red blood cells and the production of IFN-gamma by T-cells. The determination of P. c. adami antigens capable of inducing strain-transcending immunity implies the identification of orthologues in the P. falciparum genome that may be applied as components of a human malaria vaccine.

Includes bibliographical references. / 146, [65] leaves, [18] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The major aim of this thesis is to establish whether toxin-coregulated pilus (TCP) is significant in the pathogenesis of Vibrio cholerae strains of the alternative El Tor biotype. The study investigates whether TCP are assembled by El Tor strains during growth in vitro, evaluates the in vivo significance of TCP by constructing tcpA mutants of several El Tor strains and comparing their in vivo behaviour with wild-type and determines whether the TCP produced by the 017 cosmid clones is solely cosmid-derived or whether the chromosomal tcp operon is also expressed. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1996

Copies of author's previously published article inserted onto back cover. / Bibliography: leaves 164-187. / xxii, 187, [87] leaves, [18] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Confirms the value of DHBV infection in ducks as a model to evaluate the protective and therapeutic efficacy of DNA vaccines against hepadnavirus infection. The possibility that this model could be explored further to evaluate various combinations of antigens and cytokines 'cocktail' DNA vaccines that elicit the most effective humoral and effective CMI responses for prevention and treatment of HBV infection is discussed. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1999

Copies of author's previously published article inserted onto back cover. / Bibliography: leaves 164-187. / xxii, 187, [87] leaves, [18] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Confirms the value of DHBV infection in ducks as a model to evaluate the protective and therapeutic efficacy of DNA vaccines against hepadnavirus infection. The possibility that this model could be explored further to evaluate various combinations of antigens and cytokines 'cocktail' DNA vaccines that elicit the most effective humoral and effective CMI responses for prevention and treatment of HBV infection is discussed. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1999