Study on intranasal immunizatious with recombinated-pneumococcal autolysin (Re-LytA) in mice / 中华微生物学和免疫学杂志

ABSTRACT

Objective To evaluate the protective effectiveness of intranasal immunizations with recombinated-pneumococcal autolysin(Re-LytA), which protects mice against local and systemic Streptococ- cus pneumoniae(Sp) infection. Methods Testing group (group A) CpG as an adjuvant, the mice were intranasally immunized with purified Re-LytA, obtained by affinity chromatograph. The negative control group(group B) were intranasally immunized with sterile saline. And the positive control group (group C) were received 23-valent polysaccharide commercial vaccine through intramuscular injection. All the samples were collected 2 weeks post the last immunization. The levels of antibody was determined by ELISA. Then the mice were challenged intraperitoneally and intranasally with Sp, respectively. The infection and coloniza- tion was followed by monitoring colony-forming units of Sp in the blood, homogenized lung, and nasopharyn- geal lavage fluid 4 days post intranasal immunization. The mice were observed daily to note the livability of each group. Results The level of the LytA antibody (IgG, IgA, slgA) in group A were higher than that in group B and C (P < 0.05). Neither the LytA nor polysaccharide antibody could be detected in group B. Polysaccharide antibody could be detected in group C. After challenged intraperitoneally there was no signifi- cant difference in survival rates between group A and group C (P > 0.05), which was significant higher than that in group B (P <0.05). After challenged intranasally, compared with the group A, the geometric mean colony-forming units washed from the nasopharyngeal lavage fluid of the group B and group C were signifi- cantly higher (P <0.05). Conclusion lntranasal immunizations with Re-LytA can protect mice against lo- cal and systemic pneumococcal infection, and the protective immunity may be related to sIgA.