• Parasites, Hosts and Diseases
• /
• v.48 no.1
• /
• pp.23-33
• /
• 2010

An understanding of the nature of the immune response to asexual erythrocytic stages of malaria parasites will facilitate vaccine development by identifying which responses the vaccine should preferentially induce. The present study examined and compared the immune responses of NIH mice in either single or mixed infections with avirulent (DK) or virulent (DS) strains of Plasmodium chabaudi adami using the ELISA test for detecting and measurement of cytokines and antibody production. In both single and mixed infections, the study showed that both cell- and antibody-mediated responses were activated. In all experiments, an early relatively high level of IFN-$\gamma$ and IgG2a during the acute phase of the infection, and later elevation of IL-4 and IgG1, suggested that there was a sequential Th1/Th2 response. However, in the avirulent DK strain infection a stronger Th1 response was observed compared to the virulent DS strain-infection or in mixed infections. In the virulent DS infection, there was a stronger Th2 response compared to that in the DK and mixed infections. The faster proliferation rate of the virulent DS strain compared to the DK strain was also evident.

• Molecules and Cells
• /
• v.21 no.1
• /
• pp.82-88
• /
• 2006

The global pattern of growth-dependent gene expression in Streptococcus pneumoniae strains was evaluated using a high-density DNA microarray. Total RNAs obtained from an avirulent S. pneumoniae strain R6 and a virulent strain AMC96-6 were used to compare the expression patterns at seven time points (2.5, 3.5, 4.5, 5.5, 6.0, 6.5, and 8.0 h). The expression profile of strain R6 changed between log and stationary growth (the Log-Stat switch). There were clear differences between the growth-dependent gene expression profiles of the virulent and avirulent pneumococcal strains in 367 of 1,112 genes. Transcripts of genes associated with bacterial competence and capsular polysaccharide formation, as well as clpP and cbpA, were higher in the virulent strain. Our data suggest that late log or early stationary phase may be the most virulent phase of S. pneumoniae.

• IMMUNE NETWORK
• /
• v.15 no.1
• /
• pp.27-36
• /
• 2015

In the present study, we investigated the protection conferred by a live attenuated Salmonella enterica serovar Typhimurium (ST) strain against Salmonella Typhimurium, Salmonella Gallinarum (SG), and Salmonella Enteritidis (SE) infection in layer chickens. Birds were orally primed with the attenuated ST strain at 7 days of age and then boosted at 4 weeks post prime immunization (PPI). Sequential monitoring of plasma IgG and mucosal secretory IgA (sIgA) levels revealed that inoculation with ST induced a significant antibody response to antigens against ST, SE, and SG. Moreover, significant lymphoproliferative responses to the 3 Salmonella serovars were observed in the immunized group. We also investigated protection against virulent ST, SE, and SG strain challenge. Upon virulent SG challenge, the immunized group showed significantly reduced mortality compared to the non-immunized group. The reduced persistence of the virulent ST and SE challenge strains in the liver, spleen, and cecal tissues of the immunized group suggests that immunization with the attenuated ST strain may not only protect against ST infection but can also confer cross protection against SE and SG infection.

• Korean Journal of Veterinary Pathology
• /
• v.5 no.2
• /
• pp.49-56
• /
• 2001

Ocular lesions induced in 40 specific-pathogen-free Marek's disease (MD) resistant chicks by inoculation at 1 day of age with very virulent strain of Marek's disease virus (WV) were pathologically examined. Grossly,24/40 (60%) chicks had white gel-like materials in the vitreous body, whereas thickening and discoloration of iris (gray eye) were not observed. Microscopically, characteristic ocular MD lesions were observed in choroid (27/40), ciliary (30/40) and iris (23/40) in which small focal inflammatory to diffuse neoplastic Iymphoid cells were infiltrated. Five out of 40 MDV-inoculated birds revealed necrotizing Iymphomas in choroid. These lesions consisted of necrotic and degenerating Iymphoblasts accompanied by intranuclear inclusion body. There was retinal atrophy and necrosis with inclusion body detected in necrotic ganglion, inner or outer nuclear and infiltrated Iymphoblast cells. Conjunctiva showed lymphoid cell infiltration in 29/40 chicks inoculated with MDV, Vitreous body exhibited mild to severe exudation of eosinophilic proteinaceous material in 24/40 chicks. These lesions were associated with Iymphoid cell infutration, edema and fibrosis of choroid. Pecten (7/40) and optic nerve (13/40) were infiltrated usually mildly with Iymphoid cells. From these results, very virulent strain, Md/5 of MDV caused high incidence of ocular lesions in MD resistant chicks. In addition, Md/5 induced exudation of proteinaceous material into the vitreous body and fibrosis of choroid. Necrotizing ocular Iymphoma lesions in choroid is the first report in the MD literature.

• Journal of fish pathology
• /
• v.21 no.3
• /
• pp.189-199
• /
• 2008

This paper aims to compare difference with the in an ability of their resistance and survival against in a non-specific defence mechanism of the olive flounder, between the virulent and the avirulent E. tarda strains. The tested E. tarda strains, we divided into the virulent and the avirulent strain groups on the basis of a value of 50% lethal dose (LD50) for the olive flounder weighed 10.3 g in average. The strains of LD50 101.6~104.2 cfu/fish were grouped as virulent strains, such as KE-1, KE-3, KE-5 and FSW910410. The group of avirulent strains as LD50 exceeded 108.7 cfu/fish were included the strains, SU100 and AL92448. A test was conducted to understand the survival ability of each strain in the mucus of the skin and the intestine of olive flounders. The results showed KE-1, KE-3, KE-5 and FSW910410 were highly to survive between 6 hours and 24 hours in intestine. The survival ability in the bile of olive flounder the number of avirulent strains declined during incubation but the virulent strain showed the number of alive bacteria having sustained or increased. In the test for the survival of bacteria in fresh sera of olive flounder, the virulent strains also had tendency to multiply. Concerning the tested bacteria internalization into the head kidney macrophages and the intracellurar replication in the macrophages of olive flounder. The virulent strains exhibited strong internalization, followed high rate replication. According to the results, virulent strains of E. tarda revealed more ability to resist and survive in the face of humoral and cellular defence factors than avirulent strains.

• The Plant Pathology Journal
• /
• v.36 no.5
• /
• pp.450-458
• /
• 2020

Pepper and tomato plants infected with two Clavibacter species, C. capsici and C. michiganensis have shown different patterns of disease development depending on their virulence. Here, we investigated how pepper and tomato plants respond to infection by the high-virulent or low-virulent Clavibacter strains. For this, we chose two strains of each Clavibacter species to show different virulence level in the host plants. Although low-virulent strains showed less disease symptoms, they grew almost the same level as the high-virulent strains in both plants. To further examine the response of host plants to Clavibacter infection, we analyzed the expression patterns of plant defense-related genes in the leaves inoculated with different strains of C. capsici and C. michiganensis. Pepper plants infected with high-virulent C. capsici strain highly induced the expression of CaPR1, CaDEF, CaPR4b, CaPR10, and CaLOX1 at 5 days after inoculation (dai), but their expression was much less in low-virulent Clavibacter infection. Expression of CaSAR8.2 was induced at 2 dai, regardless of virulence level. Expression of GluA, Pin2, and PR2 in tomato plants infected with high-virulent C. michiganensis were much higher at 5 dai, compared with mock or low-virulent strain. Expression of PR1a, Osmotin-like, Chitinase, and Chitinase class 2 was increased, regardless of virulence level. Expression of LoxA gene was not affected by Clavibacter inoculation. These results suggested that Clavibacter infection promotes induction of certain defense-related genes in host plants and that differential expression of those genes by low-virulent Clavibacter infection might be affected by their endophytic lifestyle in plants.

• Journal of Microbiology and Biotechnology
• /
• v.30 no.4
• /
• pp.497-504
• /
• 2020

For control of brucellosis in small ruminants, attenuated B. melitensis Rev1 is used but it can be virulent for animals and human. Based on these aspects, it is essential to identify potential immunogens to avoid these problems in prevention of brucellosis. The majority of OMPs in the Omp25/31 family have been studied because these proteins are relevant in maintaining the integrity of the outer membrane but their implication in the virulence of the different species of this genus is not clearly described. Therefore, in this work we studied the role of Omp31 on virulence by determining the residual virulence and detecting lesions in spleen and testis of mice inoculated with the B. melitensis LVM31 mutant strain. In addition, we evaluated the conferred protection in mice immunized with the mutant strain against the challenge with the B. melitensis Bm133 virulent strain. Our results showed that the mutation of omp31 caused a decrease in splenic colonization without generating apparent lesions or histopathological changes apparent in both organs in comparison with the control strains and that the mutant strain conferred similar protection as the B. melitensis Rev1 vaccine strain against the challenge with B. melitensis Bm133 virulent strain. These results allow us to conclude that Omp31 plays an important role on the virulence of B. melitensis in the murine model, and due to the attenuation shown by the strain, it could be considered a vaccine candidate for the prevention of goat brucellosis.

• Korean Journal of Veterinary Service
• /
• v.33 no.1
• /
• pp.29-35
• /
• 2010

This study was performed to test the hypothesis that Brucella abortus strain RB51 (SRB51) might protect Korean indigenous mongrel dog against challenge with either virulent B. abortus biotype 1 or B. canis. A total of 12 Korean mongrel dogs were divided into four groups (Group A, B, C and D). Dogs belonging to Group A and C were inoculated subcutaneously with $1{\times}10^9$ CFU of SRB51 in 1ml of sterile phosphate buffered saline (PBS). Dogs of Group B and D were inoculated subcutaneously with 1ml of sterile PBS as control. At 12 weeks post vaccination, dogs of Group A and B were challenged by oral inoculation of virulent strain of B. canis ($5.0{\times}10^9$ CFU) and dogs of Group C and D were challenged by oral inoculation of virulent strain of B. abortus biotype 1 ($4.4{\times}10^{10}$ CFU). The serum antibodies titers in all dogs were monitored at regular interval for eight weeks after challenge (AC) by standard tube agglutination test, plate agglutination test, rose bengal test, 2-mercaptoethanol rapid slide agglutination test and 2-mercaptoethanol tube agglutination test. No antibody titers in Group A and C was detected. Also, the challenge strains were not found from blood of all dogs of Group A and C from 1 week AC till the end of the experiment by culture and modified AMOS-PCR, whereas B. canis and B. abortus challenge strains were detected from blood of Group B and D, respectively. In addition, neither of two challenge bacteria was recovered from liver, spleen, kidneys, lymph nodes and reproductive tracts of Group A and C dogs after postmortem. However, B. canis and B. abortus challenge strains were isolated from these tissues of Group B and D, respectively. These data suggest that SRB51 could be a promising vaccine candidate for immunizing dogs to control canine brucellosis caused by B. canis or B. abortus.

• Journal of Microbiology and Biotechnology
• /
• v.12 no.1
• /
• pp.145-148
• /
• 2002

The virulence of five Verticillium lecanii strains against greenhouse whiteflies, Trialeurodes vaporariorum, was tested at various temperatures as a major environmental factor. Strain CS-626 was found to be the most durable strain at a broad temperature range, and highly virulent against greenhouse whiteflies in a detached-leaf bioassay. In a tomato plant pot experiment, the $LT_{50}\;and\;LC_{50}$ of the CS-626 strain were 6.2 days and $2.3{\times}10^6$ conidia/ml, respectively. The optimal concentration of CS-626 for successful infection was $1{\times}10^8$conidia/ml. These results indicate that the CS-626 strain of Verticillium lecanii has a strong potential for effectively controlling greenhouse whiteflies.

• Korean Journal of Microbiology
• /
• v.4 no.2
• /
• pp.1-4
• /
• 1966

As a part of studies of plant tumor induction, this experiment was prepared for the purpose of studying the ability of tumor induction and the tendency of tumor initiation in some Korean plants using the various Agrobacterium tumefaciens strains. Results obtained from this experiment are as follows. The virulences of five strains used in this experiment were gradually decreased in order of strain A6Kl, B6, 11BV7, T37 and 11 BNV6. Especially strain T37 which is known to the host limited strain showed virulent effect to the most of plants given for the materials as well as strain A6Kl, B 6 and 11BV7. Concerning the grade of tumor development, in plants which has tough stem, for example, Glycine max Meer, tumor induction was not well developed after the inoculation of all strains. Particullary in Ricinus communes Linne all strains showed virulent effect but tumor tissues were declined in relation to the development of lignification. It was also confirmed that the induction of tumor tissues on plants is to delay according to the increase of the age of host plants.