Bacterial Ghosts (BGs) are empty, non-living bacterial envelopes of Gram-negative bacteria. They are produced by controlled expression of the cloned bacteriophage gene E, which forms a lysis-tunnel structure within the envelope of the living bacteria (picture A). Since the cytoplasm and parts of the bacterial DNA are ejected into the medium through the resulting hole (arrow in picture B and C), the bacterium cannot replicate.


A) Living bacteria B) Lysing bacterium C) Bacterial Ghosts


The remaining shell is an intact membrane structure. It maintains all surface proteins of the original bacterium in its original state and therefore possesses all the structural, immunogenic and bio-adhesive properties of the original bacterium. BG envelopes are highly sophisticated natural particles that mimic the living bacteria and, therefore represent safe and effective candidates for vaccines and tumor therapy.


Following are answers to frequently asked questions (FAQs) about Bacterial Ghosts


LPS, also known as endotoxin, is part of the Bacterial Ghost (BG). Does LPS from Bacterial Ghosts pose a threat in a vaccine formulation? 


LPS is a bound entity to the intact Bacterial Ghost membrane and therefore an endotoxin reaction is not expected in humans or animals. It has been demonstrated in the limulus test that a 100-1000 fold increase of BG dose rate would be necessary to induce comparable endotoxin reactions to free LPS.


Are BGs made from pathogenic bacteria completely inactivated?


Yes, this is insured by a novel BG production process using an additional inactivation method.


For the BG production process, is there a bacteriophage involved?


No, only a plasmid with the cloned gene E from bacteriophage ΦX174 is necessary.


Is there a need for the addition of adjuvants to BGs?


For all BG candidate vaccines, regardless which immunization route is used, the addition of adjuvants is NOT required. It has been shown that LPS and petidoglycan, which are part of the BG envelope complex, act as adjuvants. They increase immunogenicity against target antigens by stimulating humoral as well as cellular immunity.


Is there a hazard of horizontal gene transfer?

BGs are 100% inactivated and therefore unable to replicate. BGs can be produced DNA-free and therefore do not present a hazard of horizontal gene transfer.


Can BGs also be produced from Gram-positive bacteria?

No, the lysis process for the production of BGs works only with Gram-negative bacteria.


How stable are BGs?

BGs are extremely stable. They can be lyophilized and stored at ambient temperatures for several years without losing its properties.


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