Engineered lactobody-producing lactobacilli: a novel form of therapy against rotavirus infection

Passive Immunization

Whereas active immunity refers to the process of exposing the individual to an antigen to generate an adaptive immune response, passive immunity refers to the transfer of antibodies from one individual to another. Passive immunity provides immediate but short-lived protection, lasting several weeks up to 3 or 4 months. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta or from breast milk to the gut of the infant. It can also be produced artificially, when antibody preparations derived from sera or secretions of immunized donors or, more recently, different antibody producing platforms are transferred via systemic or mucosal route to nonimmune individuals. Passive immunization has recently become an attractive approach because of the emergence of new and drug-resistant microorganisms, diseases that are unresponsive to drug therapy and individuals with an impaired immune system who are unable to respond to conventional vaccines. This chapter addresses the contributions of natural and artificial acquired passive immunity in understanding the concept of passive immunization. We will mainly focus on administration of antibodies for protection against various infectious agents entering through mucosal surfaces.

Lactobacilli producing bispecific llama-derived anti-rotavirus proteins in vivo for rotavirus-induced diarrhea

AIMS

Using genetically engineered lactobacilli, producing high avidity llama VHH domains (referred to as anti-rotavirus proteins; ARPs), to test the effect of multimeric antibody fragments as prophylaxis and therapy against rotavirus infection.

METHODS

Two ARPs, ARP1 and ARP3, shown to bind to different epitopes and act synergistically against rotavirus, were displayed on the surface of Lactobacillus paracasei as monovalent or bivalent proteins (mono- or bi-specific).

RESULTS

Although a nonsignificant difference was observed between lactobacilli producing bispecific ARP3-ARP1 and monomeric ARPs, lactobacilli producing bispecific ARP3-ARP1 were superior at reducing the rate of diarrhea when used for prophylactic and therapeutic intervention in a mouse model of rotavirus infection in comparison to nontreated animals.

CONCLUSION

Expression of bispecific antibodies in lactobacilli resulted in slight improvement of their efficacy. Furthermore, increasing the specificity would theoretically reduce the rate of appearance of viral escape mutants and would have a broader capacity to be effective against a range of viral serotypes.

Integrative expression system for delivery of antibody fragments by lactobacilli

A series of expression cassettes which mediate secretion or surface display of antibody fragments was stably integrated in the chromosome of Lactobacillus paracasei. L. paracasei producing surface-anchored variable domain of llama heavy chain (VHH) (ARP1) directed against rotavirus showed efficient binding to rotavirus and protection in the mouse model of rotavirus infection.