Comprehensive microRNA profiling in acetaminophen toxicity identifies novel circulating biomarkers for human liver and kidney injury.

Our objective was to identify microRNA (miRNA) biomarkers of drug-induced liver and kidney injury by profiling the circulating miRNome in patients with acetaminophen overdose. Plasma miRNAs were quantified in age- and sex-matched overdose patients with (N = 27) and without (N = 27) organ injury (APAP-TOX and APAP-no TOX, respectively). Classifier miRNAs were tested in a separate cohort (N = 81). miRNA specificity was determined in non-acetaminophen liver injury and murine models. Sensitivity was tested by stratification of patients at hospital presentation (N = 67). From 1809 miRNAs, 75 were 3-fold or more increased and 46 were 3-fold or more decreased with APAP-TOX. A 16 miRNA classifier model accurately diagnosed APAP-TOX in the test cohort. In humans, the miRNAs with the largest increase (miR-122-5p, miR-885-5p, miR-151a-3p) and the highest rank in the classifier model (miR-382-5p) accurately reported non-acetaminophen liver injury and were unaffected by kidney injury. miR-122-5p was more sensitive than ALT for reporting liver injury at hospital presentation, especially combined with miR-483-3p. A miRNA panel was associated with human kidney dysfunction. In mice, miR-122-5p, miR-151a-3p and miR-382-5p specifically reported APAP toxicity - being unaffected by drug-induced kidney injury. Profiling of acetaminophen toxicity identified multiple miRNAs that report acute liver injury and potential biomarkers of drug-induced kidney injury.

The flanking region sequences of the 15-kDa lipoprotein gene differentiate pathogenic treponemes.

The species Treponema pallidum includes three subspecies (pallidum, pertenue, and endemicum) that cause syphilis, yaws, and bejel, respectively. A closely related species, Treponema paraluiscuniculi, is the etiologic agent of venereal syphilis in rabbits but does not infect humans. Although these treponemes cause distinct diseases, no laboratory method for differentiation has been reported. Genetic signatures were defined in the 5' and 3' flanking regions of the 15-kDa lipoprotein gene (tpp15) that distinguish the human pathogens and T. paraluiscuniculi, as well as distinguishing T. pallidum subsp. pallidum from the causes of human nonvenereal treponematoses. A single Eco47III restriction site in the 5' flanking region differentiates T. pallidum subsp. pallidum from the other subspecies and species, and an XcmI site in the 3' flanking region differentiates T. paraluiscuniculi from the human pathogens. Polymerase chain reaction methods and restriction polymorphism were used to analyze 27 strains of pathogenic Treponema species.

Identification of the Treponema pallidum subsp. pallidum glycerophosphodiester phosphodiesterase homologue.

To identify potential opsonic targets of Treponema pallidum subsp. pallidum, a treponemal genomic expression library was constructed and differentially screened with opsonic and non-opsonic T. pallidum antisera. This method identified an immunoreactive clone containing an open reading frame encoding a 356 residue protein. Nucleotide sequence analysis demonstrated the translated protein to be a homologue of glycerophosphodiester phosphodiesterase, a glycerol metabolizing enzyme previously identified in Haemophilus influenzae, Escherichia coli, Bacillus subtilis and Borrelia hermsii. Sequence alignment analyses revealed the T. pallidum and H. influenzae enzymes share a high degree of amino acid sequence similarity (72%), suggesting that in T. pallidum this molecule may be surface exposed and involved in IgD binding as is the case with its counterpart in H. influenzae.

Detection of Treponema pallidum by a sensitive reverse transcriptase PCR.

Syphilis is diagnosed by serologic testing or by identification of the causative agent, Treponema pallidum. The bacterium has historically been detected in clinical specimens by dark-field microscopy, immunostaining with polyclonal or monoclonal antibodies, or the rabbit inoculation test (RIT). RIT is considered to be very sensitive and specific, although it is available only in research settings and is not clinically useful due to the length of time required to obtain a result. In recent years, several PCR methods have been developed for the detection of T. pallidum, but none of these has shown a clear advantage in sensitivity over RIT. We have developed a specific and highly sensitive reverse transcriptase PCR (RT-PCR) that targets a 366 bp region of the 16S rRNA of T. pallidum. This RT-PCR can detect a single organism by Southern analysis when whole organisms are diluted and 10(-2) to 10(-3) T. pallidum organisms when RNA equivalents are used to make cDNA. The test was demonstrated to detect 10(-2) T. pallidum RNA equivalents in cerebrospinal fluid. Twenty different strains of T. pallidum, isolated from cerebrospinal fluids, aqueous humor, blood, and chancres, were shown to be detectable by this test. This efficient and sensitive technique could be more useful than existing methods for detecting very low numbers of organisms in clinical samples.

Conservation of the 15-kilodalton lipoprotein among Treponema pallidum subspecies and strains and other pathogenic treponemes: genetic and antigenic analyses.

The 15-kDa lipoprotein of Treponema pallidum is a major immunogen during natural syphilis infection in humans and experimental infection in other hosts. The humoral and cellular immune responses to this molecule appear late in infection as resistance to reinfection is developing. One therefore might hypothesize that this antigen is important for protective immunity. This possibility is explored by using both genetic and antigenic approaches. Limited or no cross-protection has been demonstrated between the T. pallidum subspecies and strains or between Treponema species. We therefore hypothesized that if the 15-kDa antigen was of major importance in protective immunity, it might be a likely site of antigenic diversity. To explore this possibility, the sequences of the open reading frames of the 15-kDa gene have been determined for Treponema pallidum subsp. pallidum (Nichols and Bal-3 strains), T. pallidum subsp. pertenue (Gauthier strain), T. pallidum subsp. endemicum (Bosnia strain), Treponema paraluiscuniculi (Cuniculi A, H, and K strains), and a little-characterized simian isolate of Treponema sp. (Fribourg-Blanc strain). No significant differences in DNA sequences of the genes for the coding region of the 15-kDa antigen were found among the different species and subspecies studied. In addition, all organisms showed expression of the 15-kDa antigen as determined by monoclonal antibody staining. The role of the 15-kDa antigen in protection against homologous infection with T. pallidum subsp. pallidum Nichols was examined in rabbits immunized with a purified recombinant 15-kDa fusion protein. No alteration in chancre development was observed in immunized, compared to unimmunized, rabbits, and the antisera induced by the immunization failed to enhance phagocytosis of T. pallidum subsp. pallidum by macrophages in vitro. These results do not support a major role for this antigen in protection against syphilis infection.

VDRL antibodies enhance phagocytosis of Treponema pallidum by macrophages.

Although reactivity in nontreponemal tests develops in patients with untreated syphilis, no immunologic function has been ascribed to these antibodies. This study demonstrates that rabbit antibodies induced by immunization with VDRL antigen and VDRL antibodies affinity-purified from syphilitic rabbit serum enhance phagocytosis of Treponema pallidum. The proportion of macrophages ingesting treponemes in the presence of these antisera was 45% +/- 5% and 27% +/- 4%, respectively, versus 14% +/- 3% for normal serum (P < .001 and P < .01). Both IgG and IgM fractions contained opsonic activity. Absorption of VDRL antibodies from syphilitic serum diminished but did not eliminate opsonization, suggesting at least two classes of target molecules. Despite opsonic capacity, VDRL antibodies fail to facilitate macrophage-mediated killing of T. pallidum. Nevertheless, VDRL-immunized rabbits are partially protected against T. pallidum infection, developing fewer lesions (delayed and smaller) than do unimmunized controls. These results suggest a heretofore unrecognized functional role for VDRL antibodies in syphilis infection.

Characterization of the serum requirement for macrophage-mediated killing of Treponema pallidum ssp. pallidum: relationship to the development of opsonizing antibodies.

Serum pools were collected from rabbits bled at various times after intra-testicular infection with Treponema pallidum ssp. pallidum. These were tested for their ability to opsonize T. pallidum and promote killing of the organisms by macrophages. Compared to normal sera, significant opsonization was first seen on day 10 of infection as measured by both ingestion (P < 0.001) and macrophage-mediated killing (P = 0.006); significant levels of functional antibodies persisted through 300 days of infection. Although opsonic activity peaked early in infection, antibodies that promoted optimal macrophage-mediated killing developed much later, suggesting that these two functions may represent activities of antibodies with differing specificities or affinities. The initial development of antibodies that augment both phagocytosis and killing corresponds with the in vivo clearance of treponemes from the primary site of infection. These observations support the hypothesis that macrophages are the major effector mechanism for elimination of T. pallidum during early syphilis infection.

Opsonization of Treponema pallidum is mediated by immunoglobulin G antibodies induced only by pathogenic treponemes.

Rabbit antisera to Leptospira interrogans, Borrelia hermsii, and Treponema phagedenis biotype Reiter, reactive to shared spirochetal antigens, failed to enhance phagocytosis of Treponema pallidum by macrophages, while immunoglobulin G to Treponema pallidum subsp. pertenue and Treponema paraluiscuniculi promoted phagocytosis. Opsonic antibodies are directed to pathogen-restricted, not shared spirochetal, antigens.

A subpopulation of Treponema pallidum is resistant to phagocytosis: possible mechanism of persistence.

While untreated syphilis infection is characterized by spontaneous resolution of early lesions, a few organisms evade the host immune response and persist for many years. Macrophages are generally recognized as the effector cell responsible for bacterial clearance, and phagocytosis is enhanced by immune serum. This study examined the susceptibility of Treponema pallidum isolated at various stages of lesion resolution to opsonization and phagocytosis by macrophages in vitro. Findings suggest that the population of organisms remaining after the majority of bacteria have been cleared in vivo is resistant to phagocytosis. This may provide a mechanism for the persistence of T. pallidum in the face of an otherwise active immune response.