Streptococcus pneumoniae is a significant cause of mortality and morbidity in both children and older adults, with infection resulting in invasive disease, pneumonia and otitis media. The inclusion of pneumococcal conjugate vaccines in routine infant immunisation programmes has had a major impact on disease rates. Vaccine-induced protection against pneumococcal infection is thought to be mediated by the generation of persistent serotype-specific functional antibodies and antigen-specific memory B cells, the latter capable of generating a rapid secondary antibody response on re-exposure to antigen. Although many studies have investigated the immunogenicity of pneumococcal vaccines in different age groups by measuring serotype-specific antibodies, there is more limited information about the B cells underlying such an immune response. Important areas to investigate include the identity of the B cell subsets involved in antibody production and the potential link between memory B cells (B_MEM) and persistent antibody production by long-lived plasma cells. In this thesis I have investigated in detail the immune response to pneumococcal vaccines given to children and adults by a variety of different methods. By examining the variability of a B_MEM ELISpot method, it was shown that this assay is robust and reproducible and can be performed on fresh or frozen samples and in different laboratories. Using this technique, in a study of pre-school children, it was demonstrated for the first time that the level of pre-existing serotype 3-specific antibody is negatively correlated with, and may directly impair the B_MEM response to a booster dose of 13-valent pneumococcal conjugate vaccine (PCV-13) containing serotype 3 glycoconjugate. In the same study, it was shown that antibody persistence against most vaccine serotypes can be expected until the age of 3.5 years. A novel antigen-labelling technique was used in a detailed kinetics study of antigen-specific B cell subsets in response to either PCV-13 or 23-valent pneumococcal polysaccharide vaccine in adults. The results of this study revealed distinct B cell subset response patterns that were observed in all study participants indicating that IgM B_MEM seem to play a major role in the immune response to pneumococcal vaccines. In addition, in the same study, genome wide analysis of gene expression was performed and it was shown that vaccination with either a pneumococcal conjugate or polysaccharide vaccine results in a marked difference in numbers of differentially expressed genes 8 days following vaccination. A further tool likely to be of use in investigating B cell responses is the analysis of the antibody repertoire using next-generation sequencing techniques. In order to test the ability of these methods to detect vaccine responses, a large dataset of high-throughput B cell receptor sequences was analysed and revealed convergence of antigen-specific complementary-determining region (CDR)₃ amino acid (AA) sequences following vaccination and identified antigen-specific sequences. It was further demonstrated that for sequences directed against the H. influenzae type b (Hib) polysaccharide, diversity of immunoglobulin gene rearrangements is much greater than previously recognised. Frequencies of Hib-specific CDR₃ AA sequences were linked with anti-Hib avidity indices highlighting the potential of this method as an alternative (functional) measure of vaccine immunogenicity. These data suggest that studying the B cells and antibody repertoire post-vaccination can give novel insights into the biology that underlies the immune responses.

INTRODUÇÃO: Pacientes infectados pelo HIV apresentam maior risco de doença pneumocócica invasiva com maior mortalidade que a população geral. Estratégias para redução da carga de doença pneumocócica são importantes. A vacina antipneumocócica polissacarídica 23-valente é recomendada para adultos infectados pelo HIV, entretanto, a imunogenicidade desta vacina nessa população ainda é discutível. A vacina antipneumocócica ideal e o regime vacinal de maior eficácia ainda são controversos na literatura. Os poucos estudos publicados com vacina antipneumocócica conjugada 7-valente em adultos infectados pelo HIV apresentam resultados discrepantes. Esse estudo visa comparar a resposta de anticorpos e a reatogenicidade de três esquemas diferentes de vacina antipneumocócica, em adultos infectados pelo HIV; e avaliar o impacto da vacinação no estado de colonização da nasofaringe. MÉTODOS: ensaio clínico randomizado e duplo-cego, envolvendo 331 pacientes infectados pelo HIV, de 18 a 60 anos de idade, com contagem de linfócitos T-CD4 acima de 200 cél/mm3. Os pacientes foram alocados em grupos de duas intervenções com intervalos de 60 dias entre elas: a) vacina antipneumocócica polissacarídica 23-valente + placebo; b) vacina antipneumocócica conjugada 7-valente + placebo; c) vacina antipneumocócica conjugada 7-valente + vacina antipneumocócica polissacarídica 23-valente. A imunogenicidade das vacinas foi determinada através da reação de ELISA para sorotipos 6B, 9V e 14, realizadas no momento pré-vacinal, 60 dias e 180 dias após a primeira intervenção. A reatogenicidade foi avaliada através de entrevista após cada vacinação. A colonização da nasofaringe foi avaliada antes do início da vacinação e 180 dias após. RESULTADOS: Os grupos foram similares nas características demográficas e condições associadas à infecção pelo HIV. Nos três grupos foi observado um aumento significativo dos níveis de anticorpo-IgG para todos os três sorotipos avaliados. Foi observada uma maior proporção de indivíduos que sustentaram aumento de quatro vezes ou mais na concentração de anticorpos para sorotipos 6B e 9V nos grupos que receberam PC7V na primeira vacinação. A combinação das vacinas conjugada 7-valente seguida da vacina polissacarídica 23-valente não aumentou a imunogenicidade para nenhum dos sorotipos avaliados. Ambas as vacinas foram bem toleradas, entretanto, eventos adversos sistêmicos foram mais frequentes após aplicação da vacina conjugada 7-valente. Nenhum evento grave foi reportado. O uso da vacina polissacarídica 23- valente após a aplicação da vacina conjugada 7-valente não aumentou a reatogenicidade. A colonização da nasofaringe por S.pneumoniae foi significantemente menor 180 dias após a vacinação, embora não tenha sido observada diferença entre os três grupos. CONCLUSÃO: nesse ensaio clínico conduzido em adultos brasileiros infectados pelo HIV, observamos que as vacinas antipneumocócicas polissacarídica 23-valente e conjugada 7- valente foram seguras e imunogênicas. As evidências sugerem que a vacina conjugada 7-valente foi mais imunogênica que a polissacarídica 23-valente para os sorotipos 6B e 9V. Não houve benefício da aplicação da vacina antipneumocócica polissacarídica 23-valente após vacina conjugada 7- valente. A vacinação antipneumocócica reduziu a colonização da nasofaringe por S.pneumoniae, independentemente do esquema vacinal aplicado / BACKGROUND: The risk and the mortality of invasive pneumococcal disease are higher in HIV-infected patients than in uninfected individuals. Strategy to reduce the burden of invasive pneumococcal disease is crucial. Pneumococcal polysaccharide vaccine 23-valent is recommended for HIV- adults, but its immunogenicity is still controversial. The ideal antipneumococcal vaccine and effective vaccination regimen remain controversial. Few trials with 7-valent pneumococcal conjugate vaccine in HIV-adults revealed disparate results. This study aims to compare antibody response and reactogenicity to three different pneumococcal vaccine schedules in HIV-infected adults, and impact of vaccine in nasopharyngeal carriage of Streptococcus pneumoniae. METHODS: a randomized, blinded clinical trial was conducted in Brazil with 331 HIV-patients aged 18 to 60 years with CD4+ T-lymphocytes count >=200 cells/mm3. Two interventions 60 days apart were done in three schedules: a) 23-valent pneumococcal polysaccharide vaccine + placebo; b) 7-valent pneumococcal conjugate vaccine + placebo; and c) 7-valent pneumococcal conjugate vaccine + pneumococcal polysaccharide vaccine 23-valent. Immunogenicity was assessed by an IgG enzyme-linked immunosorbent assay to S. pneumoniae serotypes 6B, 9V and 14, performed at baseline, 60 and 180 days after first intervention. Reactogenicity was evaluated by individual interview. Nasopharyngeal colonization was evaluated before first dose and 180 days after. RESULTS: Demographic and HIV conditions were similar between all groups. Significant increase in IgG-antibodies was observed to all serotypes evaluated. A greater proportion of individuals who reached and sustained IgG antibody concentrations at least four times as high as those at baseline, for serotypes 6B and 9V received PC7V at first vaccination. A pneumococcal polysaccharide vaccine 23-valent dose after 7-valent pneumococcal conjugate vaccine did not enhance immunogenicity. Both vaccines were well tolerated across vaccine groups; however, more systemic adverse events were reported after 7-valent pneumococcal conjugate vaccine despite none severe events were described. Pneumococcal polysaccharide vaccine 23- valent after 7-valent pneumococcal conjugate vaccine did not increased reactogenicity. Nasopharyngeal colonization of S. pneumoniae 180 days after vaccination was statistically significant lower than pre-vaccination, although none difference was been observed between three groups. CONCLUSIONS: In this clinical trial conducted in Brazilian HIV-infected adults, both pneumococcal polysaccharide vaccine 23-valent and 7-valent pneumococcal conjugate vaccine were safe and immunogenic. Evidence suggesting 7-valent pneumococcal conjugate vaccine was more immunogenic than pneumococcal polysaccharide vaccine 23-valent, as it elicited higher and persistent >=4-fold increase of antibodies for serotypes 6B and 9V in a greater proportion of HIV-patients, is noteworthy. No benefit of a pneumococcal polysaccharide vaccine 23-valent dose following 7-valent pneumococcal conjugate vaccine was observed. Pneumococcal vaccination reduced nasopharyngeal colonization of S.pneumoniae in this population, without statistical difference between groups

INTRODUÇÃO: Pacientes infectados pelo HIV apresentam maior risco de doença pneumocócica invasiva com maior mortalidade que a população geral. Estratégias para redução da carga de doença pneumocócica são importantes. A vacina antipneumocócica polissacarídica 23-valente é recomendada para adultos infectados pelo HIV, entretanto, a imunogenicidade desta vacina nessa população ainda é discutível. A vacina antipneumocócica ideal e o regime vacinal de maior eficácia ainda são controversos na literatura. Os poucos estudos publicados com vacina antipneumocócica conjugada 7-valente em adultos infectados pelo HIV apresentam resultados discrepantes. Esse estudo visa comparar a resposta de anticorpos e a reatogenicidade de três esquemas diferentes de vacina antipneumocócica, em adultos infectados pelo HIV; e avaliar o impacto da vacinação no estado de colonização da nasofaringe. MÉTODOS: ensaio clínico randomizado e duplo-cego, envolvendo 331 pacientes infectados pelo HIV, de 18 a 60 anos de idade, com contagem de linfócitos T-CD4 acima de 200 cél/mm3. Os pacientes foram alocados em grupos de duas intervenções com intervalos de 60 dias entre elas: a) vacina antipneumocócica polissacarídica 23-valente + placebo; b) vacina antipneumocócica conjugada 7-valente + placebo; c) vacina antipneumocócica conjugada 7-valente + vacina antipneumocócica polissacarídica 23-valente. A imunogenicidade das vacinas foi determinada através da reação de ELISA para sorotipos 6B, 9V e 14, realizadas no momento pré-vacinal, 60 dias e 180 dias após a primeira intervenção. A reatogenicidade foi avaliada através de entrevista após cada vacinação. A colonização da nasofaringe foi avaliada antes do início da vacinação e 180 dias após. RESULTADOS: Os grupos foram similares nas características demográficas e condições associadas à infecção pelo HIV. Nos três grupos foi observado um aumento significativo dos níveis de anticorpo-IgG para todos os três sorotipos avaliados. Foi observada uma maior proporção de indivíduos que sustentaram aumento de quatro vezes ou mais na concentração de anticorpos para sorotipos 6B e 9V nos grupos que receberam PC7V na primeira vacinação. A combinação das vacinas conjugada 7-valente seguida da vacina polissacarídica 23-valente não aumentou a imunogenicidade para nenhum dos sorotipos avaliados. Ambas as vacinas foram bem toleradas, entretanto, eventos adversos sistêmicos foram mais frequentes após aplicação da vacina conjugada 7-valente. Nenhum evento grave foi reportado. O uso da vacina polissacarídica 23- valente após a aplicação da vacina conjugada 7-valente não aumentou a reatogenicidade. A colonização da nasofaringe por S.pneumoniae foi significantemente menor 180 dias após a vacinação, embora não tenha sido observada diferença entre os três grupos. CONCLUSÃO: nesse ensaio clínico conduzido em adultos brasileiros infectados pelo HIV, observamos que as vacinas antipneumocócicas polissacarídica 23-valente e conjugada 7- valente foram seguras e imunogênicas. As evidências sugerem que a vacina conjugada 7-valente foi mais imunogênica que a polissacarídica 23-valente para os sorotipos 6B e 9V. Não houve benefício da aplicação da vacina antipneumocócica polissacarídica 23-valente após vacina conjugada 7- valente. A vacinação antipneumocócica reduziu a colonização da nasofaringe por S.pneumoniae, independentemente do esquema vacinal aplicado / BACKGROUND: The risk and the mortality of invasive pneumococcal disease are higher in HIV-infected patients than in uninfected individuals. Strategy to reduce the burden of invasive pneumococcal disease is crucial. Pneumococcal polysaccharide vaccine 23-valent is recommended for HIV- adults, but its immunogenicity is still controversial. The ideal antipneumococcal vaccine and effective vaccination regimen remain controversial. Few trials with 7-valent pneumococcal conjugate vaccine in HIV-adults revealed disparate results. This study aims to compare antibody response and reactogenicity to three different pneumococcal vaccine schedules in HIV-infected adults, and impact of vaccine in nasopharyngeal carriage of Streptococcus pneumoniae. METHODS: a randomized, blinded clinical trial was conducted in Brazil with 331 HIV-patients aged 18 to 60 years with CD4+ T-lymphocytes count >=200 cells/mm3. Two interventions 60 days apart were done in three schedules: a) 23-valent pneumococcal polysaccharide vaccine + placebo; b) 7-valent pneumococcal conjugate vaccine + placebo; and c) 7-valent pneumococcal conjugate vaccine + pneumococcal polysaccharide vaccine 23-valent. Immunogenicity was assessed by an IgG enzyme-linked immunosorbent assay to S. pneumoniae serotypes 6B, 9V and 14, performed at baseline, 60 and 180 days after first intervention. Reactogenicity was evaluated by individual interview. Nasopharyngeal colonization was evaluated before first dose and 180 days after. RESULTS: Demographic and HIV conditions were similar between all groups. Significant increase in IgG-antibodies was observed to all serotypes evaluated. A greater proportion of individuals who reached and sustained IgG antibody concentrations at least four times as high as those at baseline, for serotypes 6B and 9V received PC7V at first vaccination. A pneumococcal polysaccharide vaccine 23-valent dose after 7-valent pneumococcal conjugate vaccine did not enhance immunogenicity. Both vaccines were well tolerated across vaccine groups; however, more systemic adverse events were reported after 7-valent pneumococcal conjugate vaccine despite none severe events were described. Pneumococcal polysaccharide vaccine 23- valent after 7-valent pneumococcal conjugate vaccine did not increased reactogenicity. Nasopharyngeal colonization of S. pneumoniae 180 days after vaccination was statistically significant lower than pre-vaccination, although none difference was been observed between three groups. CONCLUSIONS: In this clinical trial conducted in Brazilian HIV-infected adults, both pneumococcal polysaccharide vaccine 23-valent and 7-valent pneumococcal conjugate vaccine were safe and immunogenic. Evidence suggesting 7-valent pneumococcal conjugate vaccine was more immunogenic than pneumococcal polysaccharide vaccine 23-valent, as it elicited higher and persistent >=4-fold increase of antibodies for serotypes 6B and 9V in a greater proportion of HIV-patients, is noteworthy. No benefit of a pneumococcal polysaccharide vaccine 23-valent dose following 7-valent pneumococcal conjugate vaccine was observed. Pneumococcal vaccination reduced nasopharyngeal colonization of S.pneumoniae in this population, without statistical difference between groups