Helper T (Th) cell differentiation is highly regulated by cytokines but initiated by mitogens. By examining gene expression in discrete generations of dividing cells, we have delineated the relationship between proliferation and differentiation. Initial expression of IL-2 is cell cycle-independent, whereas effector cytokine expression is cell cycle-dependent. IFNgamma expression increases in frequency with successive cell cycles, while IL-4 expression requires three cell divisions. Cell cycle progression and cytokine signaling act in concert to relieve epigenetic repression and can be supplanted by agents that hyperacetylate histones and demethylate DNA. Terminally differentiated cells exhibit stable epigenetic modification and cell cycle-independent gene expression. These data reveal a novel mechanism governing Th cell fate that initially integrates proliferative and differentiative signals and subsequently maintains stability of the differentiated state.

To determine whether DNA immunization could elicit protective immunity to Leishmania major in susceptible BALB/c mice, cDNA for the cloned Leishmania antigen LACK was inserted into a euykaryotic expression vector downstream to the cytomegalovirus promoter. Susceptible BALB/c mice were then vaccinated subcutaneously with LACK DNA and challenged with L. major promastigotes. We compared the protective efficacy of LACK DNA vaccination with that of recombinant LACK protein in the presence or absence of recombinant interleukin (rIL)-12 protein. Protection induced by LACK DNA was similar to that achieved by LACK protein and rIL-12, but superior to LACK protein without rIL-12. The immunity conferred by LACK DNA was durable insofar as mice challenged 5 wk after vaccination were still protected, and the infection was controlled for at least 20 wk after challenge. In addition, the ability of mice to control infection at sites distant to the site of vaccination suggests that systemic protection was achieved by LACK DNA vaccination. The control of disease progression and parasitic burden in mice vaccinated with LACK DNA was associated with enhancement of antigen-specific interferon-γ (IFN-γ) production. Moreover, both the enhancement of IFN-γ production and the protective immune response induced by LACK DNA vaccination was IL-12 dependent. Unexpectedly, depletion of CD8+ T cells at the time of vaccination or infection also abolished the protective response induced by LACK DNA vaccination, suggesting a role for CD8+ T cells in DNA vaccine induced protection to L. major. Thus, DNA immunization may offer an attractive alternative vaccination strategy against intracellular pathogens, as compared with conventional vaccination with antigens combined with adjuvants.

Significance After infection of Escherichia coli by bacteriophage T7, the host RNA polymerase (RNAP) produces early phage transcription products that encode the phages own RNAP (that transcribes subsequent phage genes) as well as Gp2, an essential inhibitor of the host RNAP. X-ray crystal structures of E. coli RNAP define the structure and location of the RNAP σ 70 subunit domain 1.1 inside the RNAP active site channel, where it must be displaced by the DNA upon formation of the transcription complex. Gp2 binds inside the RNAP active site channel and also interacts with , preventing from exiting the RNAP active site channel. Gp2 thus misappropriates a domain of the RNAP, , to inhibit the function of the enzyme.

SUMMARY Follicular helper T cells (Tfh cells) are the major producers of interleukin-4 (IL-4) in secondary lymphoid organs where humoral immune responses develop. Il4 regulation in Tfh cells appears distinct from the classical T helper 2 (Th2) cell pathway, but the underlying molecular mechanisms remain largely unknown. We found that HS V (also known as CNS2), a 3’ enhancer in the Il4 locus, is essential for IL-4 production by Tfh cells. Mice lacking HS V display marked defects in Th2 humoral immune responses, as evidenced by abrogated IgE and sharply reduced IgG1 production in vivo. In contrast, effector Th2 cells that are involved in tissue responses were far less dependent on HS V. HS V facilitated removal of repressive chromatin marks during Th2 and Tfh cell differentiation, and increased accessibility of the Il4 promoter. Thus Tfh and Th2 cells utilize distinct but overlapping molecular mechanisms to regulate Il4, a finding with important implications for understanding the molecular basis of Th2 mediated allergic diseases.

Sea turtle fibropapillomatos~s (FP) is a disease marked by proliferat~on of b e n~g n but debilitating cutaneous fibropapillomas and occasional visceral fibromas Transmission experiments have implicated a chloroform-sensltlve transforming agent present in filtered cell-free tumor homogenates in the etiology of FP In t h~s study, consensus pnmer PCR methodology was used to test the a s s o c~a t~o n of a chelonian herpesvirus with f~bropapillomatosis Fibiopap~lloma and skin samples were obtalned f~o m 17 green and 2 loggerhead turtles affected iwth FP stranded along the Flor~da coastline Ninety-three cutaneous and vlsceral tumors fiom the 19 turtles, and 33 skln samples from 16 of the turtles, were tested All turtles affected with FP had herpesvlrus associated w t h thelr tumors as detected by PCR N~nety-six percent (89/93) of the tumors but only 9 % (3/33) of the skin samples from affected turtles contained detectable herpesvirus The skin samples that contained herpesvirus were all within 2 cm of a flbropapillo~na Also. 1 of 11 scar tissue samples from sites where fibropapillomas had been removed 2 to 51 wk earlier from 5 green turtles contalned detectable herpesvirus None of 18 normal skln samples from 2 green and 2 loggerhead turtles stranded without FP contained herpesvirus The data indicated that heipesvlrus was detectable only withln or close to tumors To determine if the same vlrus infected both turtle specles, partial nucleotide sequences of the herpesvlrus DNA polymerase gene were determined from 6 loggerhead and 2 green turtle samples The sequences predicted that herpesviius of loggerhead turtles dlffered from those of green turtles by only 1 of 60 a m~n o acids In the sequence examined, Indicating that a chelonlan herpesvlrus exhibltlng minor intratyplc vanation was the only helpesvlrus present in tumors of both green and loggerhead turtles The FP-assoc~ated herpesvlrus reslsted cultlvat~on on chelonian cell hnes whlch support the replicat~on of other chelonian herpesvlruses These results lead to the conclus~on that a chelonian herpesvirus IS regularly associated with f~bropap~llomatosis and 1s not merely an ~ncldental flndlng in affected turtles

SummaryA number of investigations have established the critical role ofinterleukin 4 (IL-4) in mediating the development of T helper (Th)2 effector cells in vitro and in vivo. Despite intensive study, the origin of the IL-4 required for Th2 priming and differentiation remains unclear. Natural killer (NK)1.1 + ot/[3 T cell receptor + T (NT) cells, a unique lineage of cells capable of producing large amounts of IL-4 after activation in vivo, are important candidates for directing Th2 priming. These cells are selected by the nonpolymorphic major histocompatibility complex (MHC) class I molecule, CD1, and are deficient in [~2-microglobulin ([32m)-null mice. We used [32m-deficient mice on both BALB/c and C57BL/6 backgrounds to examine their capacity to mount Th2 immune responses after challenge with a number of well-characterized antigens administered by a variety of routes. As assessed by immunization with protein antigen, infection with Leishmania major, embolization with eggs of Schistosoma mansoni, intestinal infection with Nippostrongylus brasiliensis, or induction of airway hyperreactivity to aerosolized antigen, [32m-deficient mice developed functional type 2 immune responses that were not substantially different than those in wild-type mice. Production of IL-4 and the generation ofimmunoglobulin E (IgE) and eosinophil responses were preserved as assessed by a variety of assays. Collectively, these results present a comprehensive analysis of type 2 immune responses in [32m-deficient mice, and indicate that [32m-dependent NT cells are not required for Th2 development in vivo.

Tortoise mycoplasmosis is one of the most extensively characterized infectious diseases of chelonians. A 1989 outbreak of upper respiratory tract disease (URTD) in free-ranging Agassiz's desert tortoises (Gopherus agassizii) brought together an investigative team of researchers, diagnosticians, pathologists, immunologists and clinicians from multiple institutions and agencies. Electron microscopic studies of affected tortoises revealed a microorganism in close association with the nasal mucosa that subsequently was identified as a new species, Mycoplasma agassizii. Over the next 24  years, a second causative agent, Mycoplasma testudineum, was discovered, the geographic distribution and host range of tortoise mycoplasmosis were expanded, diagnostic tests were developed and refined for antibody and pathogen detection, transmission studies confirmed the pathogenicity of the original M. agassizii isolate, clinical (and subclinical) disease and laboratory abnormalities were characterized, many extrinsic and predisposing factors were found to play a role in morbidity and mortality associated with mycoplasmal infection, and social behavior was implicated in disease transmission. The translation of scientific research into management decisions has sometimes led to undesirable outcomes, such as euthanasia of clinically healthy tortoises. In this article, we review and assess current research on tortoise mycoplasmosis, arguably the most important chronic infectious disease of wild and captive North American and European tortoises, and update the implications for management and conservation of tortoises in the wild.

Minimal standards for novel species of the class Mollicutes (trivial term, mollicutes), last published in 1995, require revision. The International Committee on Systematics of Prokaryotes Subcommittee on the Taxonomy of Mollicutes proposes herein revised standards that reflect recent advances in molecular systematics and the species concept for prokaryotes. The mandatory requirements are: (i) deposition of the type strain into two recognized culture collections, preferably located in different countries; (ii) deposition of the 16S rRNA gene sequence into a public database, and a phylogenetic analysis of the relationships among the 16S rRNA gene sequences of the novel species and its neighbours; (iii) deposition of antiserum against the type strain into a recognized collection; (iv) demonstration, by using the combination of 16S rRNA gene sequence analyses, serological analyses and supplementary phenotypic data, that the type strain differs significantly from all previously named species; and (v) assignment to an order, a family and a genus in the class, with an appropriate specific epithet. The 16S rRNA gene sequence provides the primary basis for assignment to hierarchical rank, and may also constitute evidence of species novelty, but serological and supplementary phenotypic data must be presented to substantiate this. Serological methods have been documented to be congruent with DNA-DNA hybridization data and with 16S rRNA gene placements. The novel species must be tested serologically to the greatest extent that the investigators deem feasible against all neighbouring species whose 16S rRNA gene sequences show .0.94 similarity. The investigator is responsible for justifying which characters are most meaningful for assignment to the part of the mollicute phylogenetic tree in which a novel species is located, and for providing the means by which novel species can be identified by other investigators.