Safety of a nasal vaccine against Streptococcus pneumoniae using heat-killed Lactobacillus casei as adjuvant

Abstract

Streptococcus pneumoniae is a highly important respiratory pathogen that causes infections in children, elderly people and immunocompromised people around the world. Pneumococcal vaccines licensed did not reach to eradicate the pneumococcal infection. In a previous study was demonstrated the effectiveness of a nasal experimental vaccine that consisted in a pneumococcal protective protein A (PppA) co-administrated with heat-killed-Lactobacillus casei (LcM), in mice model of respiratory pneumococcal challenge. In the present work the safety of the experimental vaccine LcM+PppA and its components were evaluated through hematological, biochemical and immune parameters in a model infection with S. pneumoniae. Thus, alanine transaminase activity, creatinine levels, lactate dehydrogenase activity, C reactive protein levels, corticosterone levels in serum, total and differential leukocyte counts in blood and bronchoalveolar lavages (BAL) and IgE in BAL, were evaluated. Experimental vaccine: LcM+PppA nasally administered does not induce harmful effects in our vaccination-infection model. Studied parameters showed LcM+PppA's safety in liver, kidney, pulmonary and systemic levels. Although studies in experimental animals do not guarantee security for the application of the vaccine on humans, they are important evidence for the planning and subsequent clinical trials in humans.

Keywords: Adjuvant; Heat killed-L. casei; Nasal vaccine; S. pneumoniae; Vaccine safety.