| Porcine Rotavirus (PRV) belongs to the family reoviridae, species rotavirus. It is one of the major pathogens that cause life-threatening diarrhea in piglets. The young animals are the most easily infected. Its infectious ratio is over 80%, and its death rate is 7-20% in 1-4 weekage pigs. Rotavirus diarrhea's typically clinical manifestation is serious diarrhea. Partial infected piglets were dead due to severe loss of water, imbalance of acid alkali and secondary infection. Accurate diagnosis and effective vaccination are main means for the prevention of porcine diarrhea. World Health Organization (WHO)gives priority to the development of rotavirus vaccine, especially its engineering vaccine.The mucosal surfaces represent a critical component of the mammalian immunologic repertoire. The immunologic network operating on external mucosal surfaces in animal body consists of gut-associated lymphoid tissue (GALT), the lymphoid structures associated with bronchoepimelium and lower respiratory tract (BALT), occular tissue, upper airway, salivary glands, tonsils and nasopharynx (NALT), larynx (LALT), middle ear cavity, male and female genital tracts, mammary glands, and the products of lactation.The mucosal surfaces of the gastrointestinal tracts represent the principal portals of entry for most pathogens. Therefore, the use of natural or induced infections and mucosal immunization with specific vaccine antigens continue to remain an attractive possibility for immunization against infections, especially those acquired through mucosal surfaces. The major antibody isotype in external secretions is secretory immunoglobulin A (slgA). Induction of IgA response provides specific protection against many respiratory, enteric, and genital infections.It has been illustrated that IgA is an associated factor to resist rotavirus. For those researchers studying rotavirus vaccine, the most important and most challenging task is to construct a kind of vaccine which can induce the intestinal mucosal surface to secrete IgA. Research shows that the inner capsid VP6 takes amount to 51% of virus particle, whose whole length is 1356 bp. It places a most important role in virus duplication and assembling. Though VP6can't induce neutralization antibody, it can induce IgA and thus induce mucosal immunity. There is also an antigenic epitope in VP6, which can induce crossing reaction with CTL. At the same time, it has no specificity between species and genus, so it is possible to solve the problem of virus' mutation by using VP6 protein as a major antigen.At present, most protective antigenic genes of rotavirus had been cloned and sequenced. But the vectors that have been reported mostly use antibiotics as selective pressure. It becomes important to construct non-antibiotic expression vector systems instead of antibiotic vector systems owing to the spreading problem of resistant genes in the latter ones. Lactobacilli are important members of normal bacteria community in guts of human beings and animals. The use of live microorganisms as an antigen delivery system is an effective means to elicit local immune responses and thus represents a promising strategy for mucosal vaccination. In this respect, Lactic acid bacteria represent an original and attractive approach, as they are safe organisms that are used as food starters and probiotics. Since Lactobacillus is an enteric organism, it colonizes and penetrates the intestinal mucosal following oral administration. The organism has the advantage of being taken up by the intestinal M cells. It should be possible to develop for human or animal use effective, nonliving, recombinant, replicating, transgenic, and microbial vector- or plant-based mucosal vaccines to prevent infections. Mucosal immunity offers new strategies to induce protective immune responses against a variety of infectious agents. Lactobacillus strains which are able to persist in the intestinal tract for several days after administration may be particularly interesting for the mucosal presentation of antigens. It is not difficul... |
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