MRC/FAPESP - bilateral agreement: Multiple-epitope vaccine to confer serotype-independent protection against pneumonia

Pneumococcal infections account for 11% of all deaths in children under 5 years of age and in older adults, Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. Pneumococcal infections in both children and adults are potentially preventable by vaccination but current vaccines do not offer the level of protection needed. Furthermore, the use of polysaccharide conjugate vaccine is associated with disease caused by non-vaccine types, a phenomenon known as serotype replacement. The existence of >90 different pneumococcal types implies that serotype replacement will be a persistent problem for anti-capsular vaccines. The development of a vaccine based on pneumococcal proteins common to all strains offers the potential for serotype-independent protection and the complete eradication of carriage.
Pneumococcal surface proteins A (PspA) and Pneumococcal surface protein C (PspC) among the most promising candidates for a protein-based vaccine. Although these proteins are variable among different clinical isolates, we have found some variants that are able to induce antibodies with broad reactivity, recognizing different PspA and PspC variants. We have also shown that fusion of PspA protein fragments is an efficient strategy to extend protection provided by a protein, but the ideal epitopes (parts of the protein) to be included in the vaccine has yet to be defined. The selection of epitopes capable of inducing antibodies with broad cross-reactivity (able to recognize all variants of PspA and PspC) is of clinical importance to the successful development of a vaccine using this approach.
We will use peptide array techniques to describe the entire range of cross-reactive epitopes target by sera that are known to be cross-reactive (murine immunized and human sera) and determine the optimal epitopes to be included in the vaccine. The approach of using peptide arrays has been successful used to identify immunogenic epitopes of candidates for Plasmodium and Leptospira vaccine but not yet for S. pneumoniae.
Our group at LSTM has successful established an Experimental Human Pneumococcal Carriage (EHPC) model and has established pneumonia patient cohorts. We will use a unique set of pre- and post-pneumococcal intranasal inoculation samples to dissect responses to PspA and PspC epitopes to a known carriage event. We will use samples from pneumonia patients to compare healthy and susceptible antibody function. Results obtained in a previous experimental human carriage study showed that presence of serum antibodies against PspA correlated with failure to establish carriage. We have observed increased antibody responses to PspA and PspC in serum, nasal wash and bronchoalveolar lavage following carriage. Immunoglobulin reponses to exposure, carriage and disease are different and show compartmentalization.
There is an urgent need for a pneumonia vaccine that is effective in childhood and in old age. We propose that an optimal vaccine will protect both age groups against pneumonia caused by all serotypes of pneumococci. We will achieve this by identifying epitopes of PspA and PspC to produce a multiple-epitope vaccine, test this vaccine in murine models of invasive disease and confirm cross-reactivity of antibodies using a wide panel of pneumococcal clinical isolates. Further we will use the effective acquired immunity that protects healthy adults against carriage and the deficient response of pneumonia patients to determine the effective levels and function of antibodies to this vaccine candidate. Finally, we will confirm induction of cellular responses elicited by immunisation in mice and the presence of multiple-epitope antigen specific CD4 T cells in healthy adults and pneumonia patients.

Invasive pneumococcal disease is a leading cause of morbidity and premature mortality around the world. Although current vaccination strategies are effective, they have major limitations such as low levels of protection against pneumonia and serotype replacement.
We have conducted extensive basic laboratory and clinical translational research that has substantially improved our understanding of the limitations of current vaccines and provided insights into new approaches for vaccine development.
We now propose a collaborative project between BI and LSTM that draws on previous successful projects to identify targets for a completely new type of pneumonia vaccine that will confer serotype-independent protection against pneumonia.
Pneumococcal surface protein A (PspA) and Pneumococcal surface protein C (PspC) are among the most promising vaccine candidates but they exhibit antigen variability. We will describe the entire range of PspA and PspC peptides in peptide arrays that will be probed with serum from immunized mice and adults exposed to pneumococci during experimental carriage to identify optimal cross-reacting epitopes to be included in a multiple-epitope vaccine.
We will test the protective potential of this vaccine in murine models and serum cross-reactivity in in vitro assays. We will confirm induction of cellular responses in immunized mice and the presence of multiple-epitope antigen specific CD4 T cells in healthy adults and pneumonia patients after ex-vivo stimulation. We will determine responses to vaccine associated with protection from experimental human pneumococcal carriage and with susceptibility to pneumonia disease.
These experiments will add a novel approach to protein vaccine discovery and knowledge regarding optimal vaccination strategy for mucosal protection.

The impact of this grant will be mainly on the partner Institutions and the development of a novel collaboration. Our Institutions are of similar age and have committed to serve least served populations. The Butantan Institute (BI) has a long standing expertise in vaccine technology that is novel to Liverpool School of Tropical Medicine (LSTM). LSTM has wide international links and an experimental/ medicine platform that is novel to BI.
1. Impact of the collaboration on partner Institutions
I. Change in the culture of organizations (LSTM and BI). We intend to add vaccine research to LSTM portfolio and improve BI international collaboration and international exposure. Vaccine research has long been the focus of BI effort but is new to the LSTM portfolio.
II. Attract R&D investment: LSTM will help BI to partner with a UK vaccine production company.
BI has expertise in technology transfer for vaccine production. BI will gain from partnership with a UK based vaccine company to transfer technology for production of other vaccines important to Brazil and other least economically developed countries (LEDC).
2. Impact on project staff and students
I. International exposure: BI researchers will gain from enhanced impact publications, international collaborators and conferences. International exposure will bring more international collaborators and joined grant applications.
II. Collaborative training: C Vadesilho (MSc student) and the PhD student that will continue the Multiple-epitope project at BI will have the opportunity of internships in the LSTM laboratory. BI students will gain from opportunity of visiting and work in an international laboratory environment. All LSTM staff will gain from the exchange of knowledge and experience during visit of international students and researchers. Staff will also benefit from future grant applications.
3. Impact on general public
I. Public involvement: General public will gain knowledge that will be disseminated during "Meet the public days" and school visits, which are regular events on both institutions. BI and LSTM have a strong past record of successful public engagement and are committed to improving the public understanding of science.
4. Impact on vulnerable populations
I. LSTM and BI have close collaboration with least economically developed countries (LEDC). The global burden of pneumococcal disease is highest in vulnerable LEDC and a successful vaccine will be targeting particularly those LEDC that do not have a pneumococcal vaccine in their national immunization program. Vulnerable population living in these countries such as woman, children and HIV population will benefit from a new vaccine.
5. Vaccination Policy
I. Vaccine success will impact in change of vaccination policy. BI is affiliated with Ministry of Health in Brazil and both produces vaccines used in the Brazilian vaccine programme and advices in vaccination policy. Our results will directly feed into a body of work that is used to inform government on vaccination strategy.