NASAL IMMUNIZATION WITH INACTIVATED LACTOCOCCUS LACTIS-PppA ASSOCIATED TO PROBIOTIC STRAIN, ENHANCES PROTECTION AGAINST PNEUMOCOCCAL RESPIRATORY INFECTION IN YOUNG MICE

VINTIÑI ELISA; ALVAREZ SUSANA; MEDINA MARCELA

San Miguel de Tucuman

Simposio; III Simposio Internacional de Bacterias Lacticas-Segundo encuentro Argentino Red BAL; 2009

CONICET-UNT

Streptococcus pneumoniae represents a serious public health problem, with high rates of morbidity and mortality, especially in underdeveloped countries. In Latin America about 20,000 children die every year because of pneumonia. In Argentina 20,000 cases of pneumonia are produced annually in children under two 2 years, with a mortality of 1% in 2008. Our group obtained a recombinant strain expressing the protective protein A (PppA) of S. pneumoniae: Lactococcus lactis-PppA (LL). Nasal (N) immunization with the live vaccine was effective in inducing protective antibodies (Abs) in both systemic (S) and pulmonary (P) compartments, in a pneumococcal infection model. However, the use of live vaccines in human is limited in the short term, due to the presence of ATB resistance genes in recombinant strains. Objective: To asses the protective effect of the N administration of recombinant inactivated bacteria alone (D-LL) and in association with a probiotic (D-LL+Lc) and to compare its effectiveness with the live vaccine (LL). We used a protocol of immunization including 3 sequential doses (days 0, 14 and 28) of the recombinant strains, while the probiotic (Lc) was nasally administered, associated with D-LL during the previous 2 d of each immunization. Control mice received PBS. Samples were taken at days 0, 14, 28 and 42. We evaluated: 1)Anti-PppA IgA, IgM, IgG Abs in serum and bronchoalveolar lavages (BAL), 2) IgG1(Th2)/IgG2a(Th1) rate in serum and BAL, 3)Protection assay: evaluation of nasal, pulmonary and blood colonization in a respiratory pneumococcal infection model with serotypes 3 and 14, 4)Cytokines in BAL: IL-2, INF-ã, IL-4, IL-10 and IL-17. D-LL induced significantly higher levels of IgA and IgG Abs in BAL and IgG in serum compared with LL. The association of Lc with D-LL induced the highest levels of specific Abs. LL-dead showed a mixed Th1/Th2 response considering an IgG1/IgG2a rate>1, while immunization with D-LL+Lc showed a polarization of the response towards Th1 cells. D-LL+Lc avoided infection with serotype 14 and reduced significantly lung and nasal colonization of serotype 3, preventing its spread to bloodstream. This immunization strategy was more effective than LL and D-LL alone. D-LL+Lc increased IL-4 with but induced lower levels of IL-10 and IL-2 compared with LL and D-LL, while INF-ã showed significantly higher levels than LL. In addition, D-LL+Lc induced lower levels of IL-17 than LL and LL-dead. The activation of the Th1 population, associated with specific humoral response in systemic and mucosal compartments (induced by IL-4), enhances the adaptive immune response by promoting pathogen clearance. Inactivated vaccine was less effective in protecting the host against the challenge with S. pneumoniae than LL. However, the nasal administration of probiotic exerted an important adjuvant effect when it was associated with inactivated recombinant strain. These results represent a promising alternative as vaccination strategy for application in human health.