Effect of an immunobiotic nasal priming on mucosa-associated lymphoid tissue in malnourished mice

Abstract

Immunobiotic lactic acid bacteria became an interesting and non-invasive alternative for the recovery of the respiratory immune response in malnourished host. Malnutrition induces atrophy of mucosa-associated-lymphoid-tissue. Little is known about the effect of malnutrition on the nasopharynx-associated-lymphoid-tissue (NALT). The effect of nasally administered Lactobacillus rhamnosus CRL1505 on NALT and its relationship with distant lymphoid tissues was evaluated. Weaned mice were malnourished with a protein-free diet (PFD) for 21d. Malnourished mice received balanced conventional diet (BCD) during 7d (BCD group) or BCD with nasal supplementation with L. rhamnosus CRL1505 (108cells/mouse/day) during the last 2 days of treatment (BCD+Lr group). Malnourished control mice (MC) received PFD while the well-nourished control group (WC) consumed BCD. After the treatments, mice were challenge with LPS (10 mg/kg weight) by intranasal route. Flow cytometry studies were carried out on thymus, spleen, lung-BALT and NALT, to study the impact on B and T cells. Protein-malnutrition significantly reduced the number of total cells, B and T cells in all the studied organs. BCD treatment was not able to normalize these cell populations. However, the BCD+Lr group showed normal numbers of spleen, lung and NALT B cells. In addition, only this group reduced quantitative alterations of CD4+ T cells in the spleen, thymus and lung induced by malnutrition. After challenge, the BCD+Lr group showed the number of mature B cells and CD8+ cells similar to de WC. These results highlights the importance of NALT as a target for the probiotics administration to improve respiratory immunity in immunocompromised malnourished hosts.