Experimental Infections with Wild and Mutant Yersinia pseudotuberculosis Strains in Rabbits

Abstract

Experimental oral infections of rabbits with a wild-type Yersinia pseudotuberculosis strain (pIB102), and two null-mutants (yopK and ypkA) were carried out with the aim to explore the possibility to use mutant strains of Y. pseudotuberculosis as live carrier vaccine strains. The infectious process of the three strains proceed with passing hyperthermia, leucocytosis with granulocytosis, moderate monocytosis and a transient lymphopenia, better demonstrated at mutant strain infections. Short-term bacterial dissemination into the brain and viscera was observed at yopK infection. An augmented resistance to bactericidal activity of leucocytes at the initial phase of infection was followed by an increased sensitivity discovered earlier in case of yopK strain accompanied by at least 70- and 20-fold, respectively, for ypkA lower virulence for mice. The level of attenuation of yopK was accompanied by significant Yersinia specific IgG and IgM antibody response. Inflammatory foci were found by morphological examination in brain, lung and small intestines after infection with the wild-type strain, while such foci were only observed in brain and mesenterial lymph nodes after infection with the yopK mutant. After infection with the ypkA mutant foci were found in brain and spleen of the infected animals. Morphological changes in the lymphatic tissue of rabbits infected with mutant strains were consistent with induction of immunogenesis. The data suggest that genetically constructed yopK null-mutant exhibits characteristics that makes the strain suitable to be used as a live carrier vaccine to deliver heterologous antigens.

Attenuation and Preserved Immunogenic Potential of Yersinia pseudotuberculosis Mutant Strains Evidenced in Oral Pig Model

“…This prolonged strong antibody response was preceded by significant augmentation of lymphocyte count. A similar antibody response was established after experimental oral infection of rabbits with the same strains of Y. pseudotuberculosis, where the highest value of IgG -1 : 200 was measured after infection with parental and mutant yopK strain (Najdenski et al, 2003). Anti-Yops IgG antibodies, against Y. pseudotuberculosis, with high titre (1 : 320) were established in our previous screening of randomly selected pigs from different farms of Bulgaria .…”

“…Significant leucocytosis accompanied by lymphocytosis and monocytosis was observed in the beginning of parental and yopK infections, which indicates an effective stimulation of lymph tissue. The level of haemoglobin and erythrocytes, established in the pig model, were surprisingly increased in contrast to the rabbit model (Najdenski et al, 2003). Similarly, high haemoglobin levels and activated erythropoesis were proved after experimental infection of pigs with Y. enterocolitica (Najdenski et al, 2006).…”

“…IgG antibodies were detected against high and low molecule weight proteins during the whole period of experimental infections with the three tested strains of Y. pseudotuberculosis . When rabbits were used as animal experimental model (Najdenski et al., 2003) immune response was detected only against seven of Yops (YopH, YopM, YopB, LcrV, YopD, YopN and YopE), but the dynamic of IgG antibodies repeats these results also in the experimentally infected pigs. This difference could be explained with host‐specific adaptation of bacteria (Pelludat et al., 2002).…”

Guanylate Binding Proteins Regulate Inflammasome Activation in Response to Hyperinjected Yersinia Translocon Components

“…YopK deficiency results in significantly attenuated infection in vivo, which was initially surprising given that YopK-deficient Yersinia translocate an increased amount of virulence factors into target cells (36,76,85,86). However, attenuation of yopK mutant Yersinia depends on caspase-1/-11, suggesting that Yersinia regulates translocation to prevent inflammasome sensing of T3SS activity (36,46).…”

Monitoring of plasmid dissociation and pathogenic potential amongYersinia enterocolotica andYersinia pseudotuberculosis during storage of refrigerated pork meat

“…The full expression of virulence in Yersinia requires the presence of 70 kb plasmid (pYV) which encodes a number of secreted proteins (Yops), as basic components of a multicomponent type III secretion system (TTSS). It is used by bacteria to establish close contact to eukaryotic cells and systemic infection proved in mice and rabbit models (Cornelis et al, 1998;Najdenski et al, 2003).…”