Nasal priming with a new postbiotic improves adaptative immune response against Streptococcus pneumoniae of the upper respiratory associated lymphoid tissue in malnourished mice

IVIR, MAXIMILIANO; VASILE, BRENDA; GUTIÉRREZ, FLORENCIA; ALVAREZ VILLAMIL, EDUARDO; SALVA, SUSANA; ALVAREZ, SUSANA

San Luis

Congreso; LXXI Reunión Científica Anual de la Sociedad Argentina de Inmunología SAI; 2023

Sociedad Argentina de Inmunología

Lymphoid tissue of the upper respiratory tract is responsible for immunosurveillance of inhaled respiratory pathogens. The hosts immunosuppressed by malnutrition are known to be particularly susceptible to Streptococcus pneumoniae (Sp) infections, and especially defects in adaptive immunity have been observed. The nasal priming of malnourished mice with the peptidoglycan (PG) of Lacticaseibacillus rhamnosus CRL1505 (Lr) is as effective as viable strain for improving systemic and respiratory immune response against Sp. However, the impact of these treatments on mucosa-associated lymphoid tissue is unknown. In this work, the effect of nasal administration of Lr or PG on the adaptive immune response of nasopharyngeal-associated lymphoid tissue (NALT) cervical lymph nodes (CLN) and axillary lymph nodes (ALN) in malnourished mice under repletion treatments was evaluated. Weaned Swiss mice were malnourished with a protein-free diet (PFD) for 21d. Then, malnourished mice received a balanced conventional diet (BCD) during 7d (BCD group) or BCD with nasal supplementation with Lr (108 cells/mouse/d) or PG (8 µg/mouse/d) during the last 2d of treatment (Lr or PG groups, respectively). Malnourished control mice (MNC) received PFD while the well-nourished control group (WNC) consumed BCD. On d8, all groups were infected with Sp (107 cells/mouse). T and B cell populations of NALT, CLN and ALN as well as production of specific antibodies were studied on days 10 and 14 post-infection. After infection, malnourished mice showed a significant reduction in the number of total cells and the different cell populations studied in both NALT and ganglia. BCD treatment was not able to normalize these parameters. However, only Lr was able to maintain the number of CD3+, CD3+CD4+ and CD3+CD8+ lymphocytes at normal values in NALT. Furthermore, Lr and PG treatments induced an increase in total B cells (B220+ cells), mature B cells (B220highCD4LowIgM+) and immature B cells (B220LowCD4HighIgM-) in NALT and ALN. Moreover, the Lr and PG mice had higher levels of bronchoalveolar lavage anti-pneumococcal antibodies (IgA, IgG and IgM) than the others groups. These results highlight the importance of NALT as a target for administration of postbiotics and immunobiotics to enhance respiratory immunity in immunocompromised malnourished hosts. Postbiotics could be an interesting alternative as mucosal adjuvants, especially in immunocompromised hosts where the use of live bacteria could be dangerous.