New doctoral dissertation promotes the development of animal vaccines intended for pigs


<div>The aim of DVM Miia Jakava-Viljanen’s doctoral thesis that has been publicly defended on 2 November, 2007 was to separate the lactobacilli of pigs and to develop vaccine carriers from them which are given orally against post-weaning diarrhoea and edema disease in pigs, for which there is not yet a protective bacterial vaccine. The advantage with oral vaccines is that they are easy to administer and economical to produce, which are important factors especially in veterinary medicine.</div>

In veterinary medicine the study of bacteria and their adhesion mechanisms gives an opportunity to develop new microbiological products for the prevention of contagious animal diseases. An important development in the prevention of infectious diseases is to develop new vaccine carriers along with the use of probiotics or health-promoting bacteria. The lactobacilli studied in Jakava-Viljanen's research are interesting in this regard, as vaccine molecules at their best can be produced in a probiotic strain and the benefit gained from these bacteria can thus be maximised.

Lactic acid bacteria, especially lactobacilli function as a natural protection in pigs against pathogens by helping to preserve the balance in the animals’ intestinal tract. It has been observed that these bacteria promote growth rates in pigs and improve the feed conversion. The effect mechanisms of lactobacilli are still incompletely known.

Many strains of Lactobacillus are known to adhere to the intestinal walls and the intestinal mucus, which prevents growth of other bacteria. The lactobacilli may thus protect the host from intestinal infections, as the adhesion to the intestine of harmful bacteria using the same receptors is prevented.

The surface layer proteins of lactobacilli form a uniform protein cover on the surface of the bacterial cell and are often adhesive. In order to form its cover the cell needs about half a million protein units. This is why both the gene expression signals of the surface layer proteins and the proteins themselves have many potential biotechnical applications. In many pathogenic bacteria the adhesion proteins are in the fimbriae, which are hair like protein structures.

In DVM Jakava-Viljanen's doctoral dissertation a known Lactobacillus strain's surface layer proteins were characterized, and Lactobacillus strains that express new surface layer proteins from the intestines and faeces of pigs were isolated and sequenced using molecular biological methods. In addition, the ability of these strains to adhere to the intestine’s epithelial cells and the extracellular matrix components were studied. In the study the structure of the operon or functioning unit of the F 18 fimbriae, was also characterized. The study showed that the FedF protein of the fimbriae is an adhesin which mediates the adhesion of E. coli to the pig’s epithelial cells. The F18 fimbriae carrying E. coli strains cause post-weaning diarrhoea and edema disease in pigs.

DVM Miia Jakava-Viljanen's doctoral thesis Characterization of porcine-specific surface (S-) layer protein carrying Lactobacillus species, S-layer proteins and the adhesin of Escherichia coli F18 fimbriae − potential applications for Veterinary Medicine has been publicly defended  on 2 November,2007 at the Faculty of Veterinary Medicine at the University of Helsinki.

The study belongs to the discipline of Basic Veterinary Science. The opponent was Professor Seppo Salminen (University of Turku) and the moderator was Professor Airi Palva (University of Helsinki).

DVM Miia Jakava-Viljanen’s doctoral dissertation can be found in pdf format on Evira’s Internet pages > Julkaisut > Selaa ja tilaa julkaisuja > Evira tutkimuksia 2007/Evira Research Reports 2007 > Evira Research Report 3/2007

For additional information, please contact:
DVM Miia Jakava-Viljanen, Virology Unit, Evira,
tel. +358 20 77 24587, mobile phone +358 50 351 0308,

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