Expression of the HOX-2.3 homeobox gene in human lymphocytes and lymphoid tissues.

Homeobox proteins are sequence-specific DNA-binding proteins initially implicated in the control of gene expression in developing tissues; however, there is increasing evidence that these proteins are important in gene regulation in adult tissues. A cDNA for the homeobox gene HOX-2.3 was isolated from an adult human B-lymphocyte cDNA library. Northern blot analysis showed expression of a 1.1 and a 1.6 kb messenger RNA (mRNA) in a human B-cell line. RNase protection assays demonstrated variable expression in both human B- and T-cell lines. Virally transformed and nontransformed lymphocyte cell lines expressed HOX-2.3 transcripts. Essentially no transcripts were found in unactivated normal B and T lymphocytes; however, B-cell activation with Staphylococcus aureus Cowan strain I and phorbol myristate acetate (PMA) or T-cell activation with phytohemagglutinin and PMA were accompanied by a rapid induction of HOX-2.3 expression even in the presence of the protein synthesis inhibitor, cycloheximide. In situ hybridization was performed to examine HOX-2.3 expression in lymphoid tissues. HOX-2.3 mRNA was detected in the thymic cortex from an 8-year-old child, in the germinal centers in adult tonsil, and in a limited number of hematopoietic cells from the bone marrow. These findings suggest the involvement of HOX-2.3 in regulating gene transcription not only in developing tissues but in hematopoietic and lymphoid tissues as well.

Application of a nested, multiplex PCR to psittacosis outbreaks.

We developed a nested, multiplex PCR for simultaneous detection of three species of chlamydiae in human and avian specimens. The PCR was designed to increase sensitivity and to circumvent inhibitors of PCR present in clinical specimens. The target sequence was the 16S rRNA gene. The first-step PCR was genus specific, and the second-step PCR was multiplexed (i.e., had multiple primer sets in the same tube) and could discriminate among Chlamydia pneumoniae, Chlamydia psittaci, and Chlamydia trachomatis on the basis of the molecular weight of the amplicon. The limit of detection of each of the two PCR steps was 5 inclusion-forming units. We used PCR and serologic evidence during outbreaks of psittacosis to infer that C. psittaci had been transmitted from birds purchased in pet stores to humans. We also used this method to test both live and dead birds from pet stores for infection with C. psittaci. Compared with culture, the application of PCR to avian specimens increased the rate of C. psittaci detection.

Cloning of a human homeobox gene that resembles a diverged Drosophila homeobox gene and is expressed in activated lymphocytes.

A new homeobox gene, HB24, has been isolated from a human B-lymphocyte cDNA library. Northern blot analysis of polyadenylated RNA purified from activated human B cells revealed a single mRNA transcript of approximately 2.3 kb. Two cDNA clones were sequenced and provided 2,250 nucleotides (nt) of DNA sequence information. There is a single methionine codon-initiated open reading frame of 1,458 nt in frame with a homeobox and a CAX repeat, and the open reading frame is predicted to encode a protein of 51,659 daltons. When the homeodomain from HB24 was compared to known mammalian and Drosophila homeodomains it was found to be only moderately conserved, but when it was compared to a highly diverged Drosophila homeodomain, H2.0, it was found to be 80% identical. The HB24 mRNA was absent or present at low levels in normal B and T lymphocytes; however, with the appropriate activation signal HB24 mRNA was induced within several hours even in the presence of cycloheximide. Characterization of HB24 expression in lymphoid and select developing tissues was performed by in situ hybridization. Positive hybridization was found in thymus, tonsil, bone marrow, developing vessels, and in fetal brain. HB24 is likely to have an important role in lymphocytes as well as in certain developing tissues.

Influence of thyroid hormone status on expression of genes encoding G protein subunits in the rat heart.

We have studied the influence of thyroid hormone status in vivo on expression of the genes encoding guanine nucleotide-binding regulatory protein (G protein) alpha-subunits Gs alpha, Gi alpha(2), Gi alpha(3), and both the 36-kDa form (beta 1) and the 35-kDa form (beta 2) of the beta-subunit in rat ventricle. The relative amounts of immunoactive Gi alpha(2) and Gi alpha(3) were greater in ventricular membranes from hypothyroid animals than from euthyroid animals (1.9- and 2.6-fold, respectively). A corresponding 2.3-fold increase in Gi alpha(2) mRNA was observed as well as a 1.5-fold increase in Gi alpha(3) mRNA. The relative amounts of immunoactive beta 1 and beta 2 polypeptides were also increased (2.8- and 1.8-fold, respectively) in the hypothyroid state and corresponded with comparable increases in the relative levels of beta 1 and beta 2 mRNAs. No difference was seen between the amounts of Gi alpha(2), Gi alpha(3), beta 1, and beta 2 in the euthyroid state and the hyperthyroid state. In contrast to these effects of thyroid hormone status on Gi alpha and beta, the steady-state amounts of Gs alpha protein and mRNA were not altered by thyroid hormone status. Thyroid hormone status did not alter sensitivity of adenylyl cyclase to stimulation by sodium fluoride or guanyl-5'-yl imidodiphosphate (GppNHp), nor did it influence GppNHp-induced inhibition of forskolin-stimulated enzyme activity. These results demonstrate that thyroid hormone status in vivo can regulate expression of specific G protein subunits in rat myocardium. However, the physiological consequences of these changes remain unclear.

Clinical outcomes of meningitis caused by Streptococcus pneumoniae in the era of antibiotic resistance.

Limited data are available on clinical outcomes of meningitis due to cefotaxime-nonsusceptible Streptococcus pneumoniae. We analyzed data from 109 cases of pneumococcal meningitis in Atlanta, Baltimore, and San Antonio, which were identified through population-based active surveillance from November 1994 to April 1996. Pneumococcal isolates from 9% of the cases were resistant to cefotaxime, and isolates from 11% had intermediate susceptibility. Children were more likely to have cephalosporin-nonsusceptible pneumococcal meningitis, but mortality was significantly higher among adults aged 18-64 years. Vancomycin was given upon admission to 29% of patients, and within 48 h of admission to 52%. Nonsusceptibility to cefotaxime was not associated with the following outcomes: increased mortality, prolonged length of hospital or intensive care unit (ICU) stay, requirement of intubation or oxygen, ICU care, discharge to another medical or long-term-care facility, or neurological deficit. Empirical use of vancomycin, current prevalence of drug-resistant S. pneumoniae, and degree of nonsusceptibility to cefotaxime may have influenced these findings.

Detection of chlamydiosis in a shipment of pet birds, leading to recognition of an outbreak of clinically mild psittacosis in humans.

Avian chlamydiosis was detected in a shipment of > 700 pet birds from a Florida bird distributor that were sold to nine Atlanta-area pet stores in August 1995. Respiratory illness among persons who had recently acquired birds from this shipment was reported to local public health officials. The attack rate of acute respiratory illness was 10.7% among persons in households exposed to birds from the implicated flock vs. 1.8% among control households (odds ratio, 6.60; 95% confidence interval, 1.39-31.2). Illness and serological evidence of infection in the absence of symptoms were more common among persons in households with recently purchased birds that were sick or that had died and among persons who had had direct contact with the birds. Clinical psittacosis or serological evidence of Chlamydia psittaci infection was found in 30.7% of households with birds from the infected flock. Mild illnesses and asymptomatic infections in exposed persons were unusual features of this outbreak.

Clinical outcomes of bacteremic pneumococcal pneumonia in the era of antibiotic resistance.

Limited data are available about the impact of antimicrobial resistance on clinical outcomes in cases of pneumococcal pneumonia. This was studied in 146 persons hospitalized with invasive pneumonia due to Streptococcus pneumoniae (minimum inhibitory concentration of cefotaxime, > or = .25 microg/mL) who were identified through population-based active surveillance for the period of November 1994 through April 1996. Compared with matched control subjects who had infection with more-susceptible S. pneumoniae, the proportion of subjects who died or who were admitted to an intensive care unit did not differ significantly. Multivariable analysis showed no significant contribution of antimicrobial resistance to mortality or the requirement for care in an intensive care unit. The ability to detect an effect of antimicrobial resistance on these important outcome measures may have been influenced by aggressive multidrug empirical therapy in this group of hospitalized patients. Factors other than resistance, such as severity of illness at presentation and advance directive status ("do not resuscitate" orders), appear to have a stronger influence on pneumococcal pneumonia outcomes.

An outbreak of acute respiratory disease caused by Mycoplasma pneumoniae and adenovirus at a federal service training academy: new implications from an old scenario.

Outbreaks of Mycoplasma pneumoniae and adenovirus have been reported in military institutions for several decades. During a recent outbreak in a federal service training academy, we performed an epidemiological and laboratory investigation to better characterize and control the outbreak. Of 586 students responding to a questionnaire, 317 (54%) reported having a respiratory illness during the outbreak period. Among 42 students who underwent complete laboratory testing, 24 (57%) had evidence of M. pneumoniae infection, 8 (19%) had evidence of adenovirus infection, and 4 (10%) had evidence of both. Polymerase chain reaction testing of oropharyngeal swabs revealed more acute M. pneumoniae infections (57% positive) than did serology or culture. Multivariate analysis revealed that visiting the campus health clinic >3 times for a nonrespiratory condition, such as injury, was a significant risk factor for illness among freshmen early in the course of the outbreak, whereas having an ill roommate was a risk factor throughout the duration of the outbreak.