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unique to this study. These in vivo-induced (ivi) proteins, encoded by ivi genes, mapped to thebackbone, O islands (OIs), and pO157. Lack of in vitro expression of O157-specific ivi proteinswas confirmed by proteomic analysis of a mid-exponential-phase culture of E. coli O157 grown inLB broth. Because ivi proteins are expressed in response to specific cues during infection andmight help pathogens adapt to and counter hostile in vivo environments, those identified in thisstudy are potential targets for drug and vaccine development. Also, such proteins may beexploited as markers of O157 infection in stool specimens.Collyn, F., M.-A. Lety, et al. (2002). "Yersinia pseudotuberculosis Harbors a Type IV Pilus Gene ClusterThat Contributes to Pathogenicity." Infect. Immun. 70(11): 6196-6205.http://iai.asm.org/cgi/content/abstract/70/11/6196Fimbriae have been shown to play an essential role in the adhesion of pathogenic gram-negativebacteria to host cells. In the enteroinvasive bacterium Yersinia pseudotuberculosis, wecharacterized a previously unknown 11-kb chromosomal locus involved in the synthesis of type IVpili. The locus consists of 11 open reading frames forming a polycistronic unit and encodingputative Pil proteins, PilLMNOPQRSUVW. When introduced into Escherichia coli, the Y.pseudotuberculosis operon reconstituted bundles of filaments at a pole on the bacterial surface,demonstrating that the pil locus was functional in a heterogenous genetic background.Environmental factors regulated transcription of the Y. pseudotuberculosis operon; in particular,temperature, osmolarity, and oxygen tension were critical cues. Deletion of the type IV pilus genecluster was associated with a reduction of Y. pseudotuberculosis pathogenicity for mice infectedorally. Forty-one percent of Y. pseudotuberculosis strains isolated from human or animal sourcesharbored the type IV pilus locus. Therefore, the pil locus of Y. pseudotuberculosis mightconstitute an "adaptation island," permitting the microorganism to colonize a vast reservoir.Jung, Y.-J., R. LaCourse, et al. (2002). "Evidence Inconsistent with a Negative Influence of T Helper 2Cells on Protection Afforded by a Dominant T Helper 1 Response against Mycobacteriumtuberculosis Lung Infection in Mice." Infect. Immun. 70(11): 6436-6443.http://iai.asm.org/cgi/content/abstract/70/11/6436Mice incapable of generating an efficient Th2 response because of functional deletion of thegenes for signal transducer and activation of transcription 6 (Stat6), interleukin-4 receptor alphachain (IL-4R{alpha}), or IL-4 plus IL-13 (IL-4/IL-13) were no more resistant than wild-type (WT)mice to airborne infection with virulent Mycobacterium tuberculosis. WT mice were able to controlinfection and hold it at a stationary level following 20 days of log linear M. tuberculosis growth.Likewise, infection was kept under control and was held at the same stationary level in IL-4/IL-13-/- mice but progressed to a slightly higher level in Stat6-/- and IL-4R{alpha}-/- mice. The onset ofstationary-level infection in WT mice was associated with the expression of Th1-mediatedimmunity, as evidenced by an approximately 100- to 1,000-fold increase in the lungs in thesynthesis of mRNA for IL-12, gamma interferon (IFN-{gamma}), and inducible nitric oxidesynthase (NOS2) that was sustained for at least 100 days. IL-12 is essential for the induction ofTh1 immunity, IFN-{gamma} is a key Th1 cytokine involved in mediation of immunity, and NOS2is an inducible enzyme of macrophages and is needed by these cells to express immunity. Inresponse to infection, the lungs of Stat6-/- mice showed increases in synthesis of mRNA for IL-12, IFN-{gamma}, and NOS2 similar to that seen in WT mice. In IL-4/IL-13-/- mice, however,synthesis of mRNA for IFN-{gamma} and NOS2 reached higher levels than in WT mice. Theseresults argue against the notion that a Th2 response is partly or wholly responsible for the inabilityof Th1-mediated immunity to resolve infection with a virulent strain of M. tuberculosis.
Kohler, A. K., D. M. Stone, et al. (2003). "Rhodococcus equi Secreted Antigens Are Immunogenic andStimulate a Type 1 Recall Response in the Lungs of Horses Immune to R. equi Infection." Infect.Immun. 71(11): 6329-6337.http://iai.asm.org/cgi/content/abstract/71/11/6329Rhodococcus equi is an opportunistic pathogen in immunocompromised humans and animportant primary pathogen in young horses. Although R. equi infection can produce lifethreateningpyogranulomatous pneumonia, most foals develop a protective immune responsethat lasts throughout life. The antigen targets of this protective response are currently unknown;however, Mycobacterium tuberculosis is a closely related intracellular pathogen and provides amodel system. Based on previous studies of M. tuberculosis protective antigens released intoculture filtrate supernatant (CFS), a bacterial growth system was developed for obtaining R. equiCFS antigens. Potential immunogens for prevention of equine rhodococcal pneumonia wereidentified by using immunoblots. The 48-h CFS contained five virulence-associated protein bandsthat migrated between 12 and 24 kDa and were recognized by sera from R. equi-infected foalsand immune adult horses. Notably, the CFS contained the previously characterized proteinsVapC, VapD, and VapE, which are encoded by genes on the R. equi virulence plasmid. R. equiCFS was also examined for the ability to stimulate a type 1-like memory response in immunehorses. Three adult horses were challenged with virulent R. equi, and cells from thebronchoalveolar lavage fluid were recovered before and 1 week after challenge. In vitrostimulation of pulmonary T-lymphocytes with R. equi CFS resulted in significant proliferation anda significant increase in gamma interferon mRNA expression 1 week after challenge. Theseresults were consistent with a memory effector response in immune adult horses and provideevidence that R. equi CFS proteins are antigen targets in the immunoprotective response againstR. equi infection.Long, C. D., D. M. Tobiason, et al. (2003). "Low-Level Pilin Expression Allows for Substantial DNATransformation Competence in Neisseria gonorrhoeae." Infect. Immun. 71(11): 6279-6291.http://iai.asm.org/cgi/content/abstract/71/11/6279The gonococcal pilus is a major virulence factor that has well-established roles in mediatingepithelial cell adherence and DNA transformation. Gonococci expressing four gonococcal pilinvariants with distinct piliation properties under control of the lac regulatory system were grown indifferent levels of the inducer isopropyl-{beta}-D-thiogalactopyranoside (IPTG). These pilinvariants expressed various levels of pilin message and pilin protein in response to the level ofIPTG in the growth medium. Moreover, posttranslational modifications of the variant pilin proteinswere detected, including S-pilin production and glycosylation. The ratio of the modified andunmodified pilin forms did not substantially change with different levels of pilin expression,showing that these modifications are not linked to pilin expression levels. DNA transformationcompetence was also influenced by IPTG levels in the growth medium. Substantial increases intransformation competence over an isogenic, nonpiliated mutant were observed when limitedamounts of three of the pilin variants were expressed. Immunoelectron microscopy showed thatwhen limited amounts of pilin are expressed, pili are rare and do not explain the pilin-dependenttransformation competence. This pilin-dependent transformation competence required prepilinprocessing, the outer membrane secretin PilQ, and the twitching-motility-regulating protein PilT.These requirements show that a fully functional pilus assembly apparatus is required for DNAuptake when limited pilin is produced. We conclude that the pilus assembly apparatus functionsto import DNA into the bacterial cell in a pilin-dependent manner but that extended pili are notrequired for transformation competence.
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Page 14 and 15: 700.http://iai.asm.org/cgi/content/
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Page 20 and 21: Behrens, M., J. Sheikh, et al. (200
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Page 25: histopathology. The mucosal immune
Page 29 and 30: Immun. 70(10): 5556-5561.http://iai

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