ABSTRACT
Mycobacterium bovis BCG prime DNA (Mycobacterium tuberculosis genes)-booster vaccinations have been shown to induce greater protection against tuberculosis (TB) than BCG alone. This heterologous prime-boost strategy is perhaps the most realistic vaccination for the future of TB infection control, especially in countries where TB is endemic. Moreover, a prime-boost regimen using biodegradable microspheres seems to be a promising immunization to stimulate a long-lasting immune response. The alanine proline antigen (Apa) is a highly immunogenic glycoprotein secreted by M. tuberculosis. This study investigated the immune protection of Apa DNA vaccine against intratracheal M. tuberculosis challenge in mice on the basis of a heterologous prime-boost regimen. BALB/c mice were subcutaneously primed with BCG and intramuscularly boosted with a single dose of plasmid carrying apa and 6,6'-trehalose dimycolate (TDM) adjuvant, coencapsulated in microspheres (BCG-APA), and were evaluated 30 and 70 days after challenge. This prime-boost strategy (BCG-APA) resulted in a significant reduction in the bacterial load in the lungs, thus leading to better preservation of the lung parenchyma, 70 days postinfection compared to BCG vaccinated mice. The profound effect of this heterologous prime-boost regimen in the experimental model supports its development as a feasible strategy for prevention of TB.
Subject(s)
Adjuvants, Immunologic/administration & dosage , Antigens, Bacterial/immunology , Cord Factors/administration & dosage , Mycobacterium tuberculosis/immunology , Tuberculosis Vaccines/immunology , Tuberculosis, Pulmonary/prevention & control , Vaccines, DNA/immunology , Animals , Antigens, Bacterial/genetics , Bacterial Load , Disease Models, Animal , Drug Carriers/administration & dosage , Female , Humans , Lung/microbiology , Lung/pathology , Mice , Mice, Inbred BALB C , Microspheres , Mycobacterium tuberculosis/genetics , Tuberculosis Vaccines/administration & dosage , Tuberculosis Vaccines/genetics , Tuberculosis, Pulmonary/immunology , Vaccines, DNA/administration & dosage , Vaccines, DNA/geneticsABSTRACT
A tuberculose (TB) é responsável por dois milhões de mortes a cada ano, apesar daampla utilização da vacina BCG (Bacilo Calmette-Guérin). Embora essa vacina nãoproteja contra a TB pulmonar no adulto, protege contra as formas graves da TB nainfância. Para muitos autores, a imunização heteróloga (prime-boost) talvezseja uma das estratégias mais importantes e realistas para o controle da TB,principalmente nos países endêmicos. Muitos estudos têm demonstrado que aimunização com BCG seguido de reforço com vacina gênica (genes de M.tuberculosis) induz melhor proteção contra TB do que somente a vacina BCG. Alémdisso, a estratégia prime-boost utilizando microesferas biodegradáveis pareceser uma imunização promissora para estimular a resposta imune de longa duração.A glicoproteína APA foi identificada como importante antígeno imunodominante,induzindo níveis significativos de proteção contra M. tuberculosis. Assim, esteestudo teve como objetivo avaliar a eficácia protetora da imunização heteróloga emmodelo experimental de TB. Para isso, camundongos BALB/c foram imunizados porvia subcutânea com BCG seguido de um reforço por via intramuscular com aformulação vacinal contendo apa e DMT co-encapsuladosem microesferas (BCG/APA). Essa estratégia prime-boost foi eficiente na indução daresposta imune protetora à infecção por M. tuberculosis, caracterizada pela reduçãosignificativa do número de bacilos no pulmão destes animais na fase mais tardia dainfecção (70 dias após desafio). Além de ser significativamente mais imunogênciaque a vacina BCG, permitiu uma melhor preservação do parênquima pulmonar, comredução do número e tamanho dos granulomas, limitando a extensão da injúriatecidual induzida pela infecção e restringindo a inflamação no tecido alveolar. Apotencialização do efeito protetor da vacina BCG induzida pelo reforço com a vacinapVAXapa+DMT-Me sugere que a estratégia utilizada pode ser importante para aprevenção da TB...
Tuberculosis (TB) is responsible for two millions of deaths each year despite thewidespread use of BCG vaccine (Bacillus Calmette-Guérin). Although this vaccinedoes not protect against adult pulmonary TB, it is protective against severe forms ofchildhood TB. For many authors, heterologous prime-boost regimen is perhaps themost realistic strategy for future TB control, especially in endemic countries. Manystudies have demonstrated that BCG-prime DNA-(M. tuberculosis genes)-boosterinduce greater protection against TB than BCG alone. APA glycoprotein has beenidentified as major immunodominant antigen and induces significant levels ofprotection against M. tuberculosis. Moreover, prime-boost strategy by usingbiodegradable microspheres seems to be a promising immunization to stimulate longlasting immune response. Thus, this study had as aim to investigate the immuneprotection against M. tuberculosis challenge in mice based on BCG priming and DNAvaccine boosting. For that, BALB/c mice were inoculated subcutaneously with aheterologous BCG priming-DNA boosting immunization using pVAXapa and TDM coencapsulatedin microspheres (BCG/APA), intramuscularly. This prime-boost strategywas effective in inducing protective immune response against M. tuberculosisinfection, characterized by significant lower numbers of bacilli in the lungs of theseanimals, in the late phase of infection (70 days after infection). In addition to beingsignificantly more immunogenic than BCG, it allowed better preservation of the lungparenchyma and reduction in the number and size of granulomas, limiting the extentof lung injury induced by infection and inflammation in the alveolar tissue. Theimprovement of the protective effect of BCG vaccine mediated by pVAXapa boostersuggests that our strategy can be important in the treatment for prevention of TB...
