Failure of killed Listeria monocytogenes vaccine to produce protective immunity

Suppression of the Bacterial Antigen‐Specific T Cell Response and the Dendritic Cell Migration to the Lymph Nodes by Osteopontin

“…However, our results unexpectedly demonstrated that exogenously added OPN suppressed the induction of the Th1 response against listerial antigen. The induction of the Th1 response by both weak Th1 inducer HKLM (17,43) and strong Th1 inducer VLM (16,19,22) was suppressed. Although these findings seem to conflicting with those of previously published reports showing the importance of OPN in Th1 induction (5,24,29,46), we would like to state that their experimental approach differed from ours.…”

“…monocytogenes is an intracellular bacterium, and it is well established that the vaccination with viable L. monocytogenes (VLM) can induce a strong Th1 response and protective immunity. In contrast, vaccination with heat-killed L. monocytogenes (HKLM) failed to induce a strong protective immunity (43). We previously reported that HKLM failed to induce a sufficient level of interferon (IFN)-γ-producing Th1-type T cells to protect the mice because IL-10 induced by HKLM suppresses IL-12 production (39,40).…”

Harnessing Listeria monocytogenes to target tumors

“…40,42 Also, only live Listeria-based vaccines provide protection while heat-killed Listeria, despite the induction of strong memory CD8 T-cell responses, does not. 43 One reason could be that CD8 T-cells activated by live LM are cytolytic in vitro, while CD8 T-cells activated by heatkilled LM are not. 44 However, another report describes that cytolytic activity is not required for protection.…”

Towards a non-living vaccine against Shigella flexneri: From the inactivation procedure to protection studies

“…Considerable knowledge has been accumulated regarding the efficiency of microbicidal treatments but, at the same time, the preservation of immunogenicity and native structure during production may limit their potential due to the alteration of epitopes that may be essential to confer protection. Thus, most used treatments, such as heat, acetone, phenol or formaldehyde, cause membrane damage or induce cross-linking of proteins leading to antigenic alterations and consequent failure in the ability to elicit protective immunity [13][14][15][16][17][18][19][20][21]. Here, we evaluate binary ethylenimine (BEI) alone or in combination with formaldehyde (BEI-FA) as inactivating agent against Shigella cells viability.…”