Most pathogens gain access to their host through mucosal surfaces. It is therefore desirable to develop mucosal vaccines that elicit an immune response to prevent this crucial first step in infection. Current mucosal vaccines are live attenuated strains of pathogens. More recent efforts have focused on the use of recombinant non-pathogenic gram-positive bacteria as live vaccine delivery vectors. Here I have tested the potential of Lactococcus lactis to be used as a vaccine vector. A recombinant strain of L. lactis has been constructed which expresses and displays on its surface the C repeat region (CRR) of the M6 protein of Streptococcus pyogenes. I show that nasal vaccination of mice with this strain elicited strong salivary IgA and serum lgG response. These responses protected mice against a nasal challenge with S. pyogenes. Subcutaneous vaccination with the same strain of L. lactis produced a strong serum lgG response, but no salivary lgA response. Subcutaneous vaccination did not protect the mice against nasal infections when the mice were challenged with S. pyogenes. The immune response and protection afforded by concomitant vaccination by both nasal and subcutaneous routes were better that that seen in nasal vaccination alone. This study shows that an effective vaccine against S. pyogenes is possible using L. lactis as a vaccine vector. It also opens up the potential of L. lactis to be used in the development of vaccines to other mucosal infections. / Graduation date: 2004

Introduction: Despite advances in prevention and treatment of vaccine-preventable diseases, diarrhoeal and pneumococcal diseases remain a major source of morbidity and mortality among children worldwide. The introduction of vaccines has led to dramatic reductions in the burden of infectious diseases and mortality among children. South Africa was the first country in Africa to introduce rotavirus vaccine (RV) and pneumococcal conjugate vaccine (PCV) in 2008 as part of its national immunisation programme. Performance of immunization programmes is commonly measured by the coverage and uptake of vaccines, hence ensuring that every child is immunized at the earliest or appropriate age is an important public health goal. We therefore assessed proportions and factors associated with uptake of RV and PCV among infants who were followed during the routine demographic surveillance system of the Africa Centre Demographic Surveillance Area (DSA) in a rural South Africa setting. Methods: An open cohort of children resident in the DSA aged 12 months or below was prospectively followed between January 2008 and December 2011. Trained interviewers visited households and administered a standardised questionnaire. Mothers and caregivers were asked to show the interviewers the South African Road-To-Health (RTH) card for all children aged 12-23 months at the time of the visit or through maternal recall for children whose RTH card was not available. The RTH card includes dates of all routine vaccinations a child has received. Rotavirus vaccine doses are given at 6 and 14 weeks of age and PCV doses at 6 and 14 weeks and 9 months. Complete uptake was defined as “complete” if a child received all recommended doses of either RV or PCV and incomplete if a child did not receive any dose or received one dose of RV or PCV. Logistic regression models were used to assess factors associated with uptake of RV and PCV separately. Results: A total of 6,263 children were included in the analysis, of which 3,082 (49%) were females. At birth, 3,823 (61%) children were living in rural areas and about one-sixth of the children were living in households located far from a health facility (≥5km). The overall uptake of RV and PCV vaccines among children aged 12 months or below was 50% and 37% respectively. Infants who ever migrated outside the DSA had reduced odds of complete RV and PCV vaccination compared to infants who did not out migrate (adjusted OR=0.49, 95% CI 0.41-0.57) and (adjusted OR=0.52, 95% CI 0.43-0.63) respectively. Complete uptake of RV was associated with the increase in education levels of mothers compared secondary education (adjusted OR=1.70, 95 % CI 1.02-2.34) or tertiary education (adjusted OR=1.80, 95 % CI 0.97-2.44). Infants whose mothers were employed were less likely than infants whose mothers were not employed to have complete vaccination for RV or PCV (adjusted OR=0.71, 95 % CI 0.60-0.84) and (adjusted OR=0.81, 95% CI 0.68-0.96) respectively. Similarly, infants whose mothers were resident in the DSA were more likely than infants whose mothers were not resident to have complete vaccination for RV or PCV (adjusted OR=1.97, 95 % CI 1.49-2.60) and (adjusted OR=1.55, 95% CI 1.16-2.08) respectively. Conclusion and recommendation: The uptake of complete RV and PCV were generally low among children in rural South Africa within our study period. Child outmigration, maternal employment, maternal education and maternal residency in the DSA at child birth were associated with complete uptake of RV and PCV vaccines. Programmes targeting mothers of lower socio-economic status are required. Such programmes may include vaccine awareness and immunization campaigns at the community level to improve vaccine uptake and more targeted interventions in areas with low RV and PCV uptake.

[Truncated abstract] Infectious and allergic diseases of the respiratory tract are major contributors to global mortality, morbidity and economic burden. Bacterial infections such as pneumonia and otitis media are important diseases, especially in children, while allergic diseases such as asthma and allergic rhinitis afflict up to 30% of the world's population. A confounding aspect of respiratory disease is the evidence of a complex relationship between respiratory allergy and respiratory infection, with infection suggested to both promote and prevent the pathogenesis of allergic disease. Additionally, allergy is a risk factor for bacterial infection such as otitis media, pneumonia and sinusitis, while respiratory infection can exacerbate allergic symptoms. Given the burden of bacterial respiratory disease and respiratory allergy, the development of preventative treatments for these diseases is needed and will benefit from clearer knowledge of the underlying immune mechanisms. This thesis aimed to to extend current knowledge by using Pasteurella pneumotropica, a similar bacteria to the human pathogen nontypeable Haemophilus influenzae (NTHi), to study respiratory infection and protective anti-outer membrane protein (OMP) immunity as well as the interaction of respiratory infection and allergic inflammation. Homologues of the important NTHi vaccine candidates P4, P6, P26 and D15 were found to be encoded by P. pneumotropica and a high level of amino acid sequence identity was noted between the different P. pneumotropica strains, as well as between other Pasteurellaceae members. ... In contrast, anti-P6his serum antibodies transferred to naïve mice did not confer protection. These results suggested that T-cell–mediated mechanisms were involved in P6his-mediated protection, and showed that the P. pneumotropcia model was useful for elucidating protective mechansims. The interaction of P. pneumotropica infection and papain-induced allergy was studied to investigate immune mechanisms underlying respiratory infection and allergy. Mice with ongoing allergic inflammation were intranasally challenged with bacteria and exhibited reduced pulmonary bacterial numbers, prolonged eosinophilia in the lungs and the induction of Th2 cytokines in the BALF, compared to nonallergic, infected mice. This suggested a protective role for allergic inflammation in this model. The effect of papaininduced inflammation on mice colonised by P. pneumotropica was also examined and allergic inflammation appeared to worsen infection in colonised mice. This suggested that allergic inflammation may also have a role in promoting infection in this model. In conclusion, this thesis explored mechanisms involved in vaccine-mediated immunity and the interaction of respiratory infection and allergy using a P. pneumotropica infection in its natural host. It was shown that intranasally administered recombinant P6 and P4 protected mice from lung infection, which justifies the inclusion of these OMPs as NTHi vaccine candidates. Additionally, it was demonstrated that the interaction of allergy and respiratory infection modulated immune responses. Overall, these results emphasize that a clearer understanding of the complex mechanisms underlying these interactions is required, and may be aided by the development of suitable animal models.