Chemistry and biology of natural and designed enediynes

Ever since the initial reports of the enediyne anticancer antibiotics in the late 1980s, researchers from a number of disciplines have been devoting increasing attention to their chemistry, biology, and potential medical applications. Synthetic chemists and molecular designers have been engaged in attempts to synthesize these molecules and to model their unique architecture. Considerable efforts have been directed at understanding and mimicking the various processes involved in the targeting, activation, and DNA cleavage associated with these natural products. This review summarizes the main contributions to the field, with particular emphasis on work from our laboratories. Highlights include studies of the Bergman reaction, which is central to the mechanism of action of enediynes, the design and chemical synthesis of a number of these systems, and biological studies with selected molecules. Finally, the total synthesis of calicheamicin gamma 1I, the most prominent member of this class of naturally occurring compounds, is discussed.

Localization of the A1.12/9 antigen family to the neurones, putative sensory receptors and tegument of Schistosoma mansoni

The A1.12/9 antigen family were localized to the periphery of vesicle-like structures in neurones and in the putative sensory receptors of cercariae by immuno-electron microscopy. After transformation into schistosomula, the antigens were rapidly lost until, after 18 h, no immunoreactivity could be detected. Expression resumed at approximately 36 h post-transformation and had returned to high levels by 4 days post-infection. This level was maintained through to the adult worm stage. In 4 day lung schistosomula and in 14 day and 21 day liver schistosomula immunolabelling was observed within the matrix of the tegument itself and also in association with the tegumental membrane and vesicles within the tegument. These properties suggest that the A1.12/9 antigens may be involved in neuropeptide processing pathways. In particular, this family may represent the schistosome homologue of the granin family with which they share common properties and some sequence homology.

Virulence of a Bordetella pertussis strain expressing a mutant adenylyl cyclase with decreased calmodulin affinity

Bordetella pertussis, the pathogen responsible for whooping cough, produces a toxic calmodulin-sensitive adenylyl cyclase which enters animal cells and increases intracellular cAMP. A point mutant of B. pertussis with abolished adenylyl cyclase catalytic activity was over 1000-fold less pathogenic to newborn mice than wild-type bacteria, demonstrating the importance of the adenylyl cyclase for B. pertussis virulence (Gross et al.). The B. pertussis adenylyl cyclase is highly sensitive to calmodulin with an apparent Kd for calmodulin of approximately 1 nM. The importance of this high-affinity calmodulin binding for virulence in vivo was examined by the creation of a B. pertussis point mutant (Trp-242 to Glu-242) with 200-fold lower calmodulin affinity than the native enzyme. This mutant B. pertussis strain retained its virulence in a newborn mouse model of pertussis, but the time course for establishment of a lethal infection in vivo was significantly delayed for the mutant strain. These data illustrate that high-affinity calmodulin binding is not obligatory for the activity of this toxin but is important for the rate for establishment of a lethal infection.

Development and optimization of plaque assays for rat coronaviruses

Plaque assays under Sephadex or agarose overlays are described for rat coronaviruses (RCVs) grown in L2 mouse fibroblasts. A plaque assay using Sephadex was simple; however, viable plaques could not be collected for propagation, and fixation was necessary before evaluation. Plaque formation under agarose was optimized using diethylaminoethyl-dextran (DEAE-D) in the pre-treatment and absorption media and trypsin added to the absorption media and agarose overlay. The use of DEAE-D alone, trypsin alone or trypsin combined with DEAE-D significantly increased plaque numbers and visibility. Plaque numbers were highest when pre-treatment media contained DEAE-D, absorption media contained DEAE-D and trypsin, and the agarose overlay contained trypsin. The assay was useful for plaque isolation and quantification of sialodacryoadenitis virus (SDA), Parker's rat coronavirus (PRCV) and other coronavirus isolates from rats and its specificity was demonstrated by plaque-reduction neutralization testing. These methods will facilitate production of cloned virus stocks for study of RCV biology and virus quantification for in vitro and in vivo studies of RCVs.

Long-term study of cell-mediated responses to Borrelia burgdorferi in the laboratory mouse

Borrelia burgdorferi infection of disease-susceptible (C3H) and -resistant (BALB) mice resulted in impaired proliferation to both T- and B-cell mitogens up to 30 days after inoculation. Interleukin-2 and -4 production was also impaired, paralleling the T-cell response to concanavalin A. Impaired lymphocyte proliferation could not be attributed to diminished numbers of T or B cells and was found to depend on the lymphoid organ (spleen or lymph node) examined. Prostaglandin production accounted for part of this immune dysfunction. Attempts to assess antigen-specific proliferation to B. burgdorferi were inconsistent, and delayed-type hypersensitivity responses were not detected. Adoptive transfer of T-enriched cells from chronically infected donors failed to prevent infection and disease development in recipient C3H mice. The current study emphasizes caution in the study of B. burgdorferi antigen-specific assays and argues against the role of a vigorous T-cell response in Lyme borreliosis in infected laboratory mice.

Prevalence of viral antibodies and helminths in field populations of house mice (Mus domesticus) in southeastern Australia

A 13-month study of wild mice (Mus domesticus) in wheatlands in southeastern Australia contrasted changes in the seroprevalence of antibody to 13 viruses and the occurrence of helminths with changes in their population dynamics. Mice were seropositive for mouse hepatitis virus (MHV), rotavirus, minute virus of mice (MVM), mouse adenovirus (MAdV), reovirus (reo 3), and murine cytomegalovirus (MCMV). The seroprevalences of all but rotavirus varied significantly with time and increased with host density. Near the end of the study, host density declined rapidly and the seroprevalence of MVM and reo 3 increased significantly. These two viruses had low seroprevalence when host survival was high and high seroprevalence when host survival was low, indicating they may play a role in regulating mouse populations. In the case of MVM, there was evidence of a viral epizootic during the decline in mouse abundance. The prevalence of four helminths (Taenia taeniaeformis, Syphacia obvelata, and Vampirolepis spp.) differed significantly with time but showed no apparent association with host density. These findings highlight the need for further study on the effect of viruses on the population dynamics of mice.

Exacerbation of Pneumocystis carinii pneumonia in immunodeficient (scid) mice by concurrent infection with a pneumovirus

scid mice naturally infected with Pneumocystis carinii and inoculated with a normally apathogenic pneumovirus had significantly higher P. carinii cyst counts and developed significantly more severe P. carinii-related disease than did sham-inoculated, P. carinii-infected scid mice. P. carinii-free, virus-infected scid mice survived for 2 months despite high pulmonary virus titers. These results show that a respiratory virus infection can exacerbate P. carinii disease in an immunocompromised-rodent model.

In vivo studies with an "orphan" parvovirus of mice

A virus antigenically related to, but distinct from, minute virus of mice was assessed for infectivity in neonatal and weanling random-bred mice and was equally infectious for both age groups. The virus, designated a mouse "orphan" parvovirus (OPV), was also localized in tissues of experimentally infected random-bred, inbred, and immunodeficient mice by in situ hybridization. Hybridization signal was seen in exocrine and endocrine pancreas, abdominal lymph nodes, mesentery, intestine, and sporadically in other tissues of Sencar, C3H, and DBA mice inoculated as infants. In adult BALB/c severe combined immunodeficient (scid) mice, signal was seen in lung, liver, spleen, lymph nodes, and intestine but not in pancreas. Transmission of OPV by Sencar mice inoculated as infants was intermittent, whereas transmission by Sencar mice inoculated as weanlings was consistent during the first 2 weeks both by direct contact and by exposure to soiled bedding. The longest duration of transmission was 6 weeks among mice inoculated as infants. The results implicate a role for urinary, fecal, and perhaps respiratory excretion of virus, depending on host genotype and route of virus exposure. They also suggest that evaluation of pancreatic and immune function during acute infection is warranted.

Characterization of acute rat parvovirus infection by in situ hybridization

In situ hybridization and virus titration were used to characterize early stages of rat virus (RV) infection of rat pups after oronasal inoculation. Results suggest that virus enters through the lung and that early viremia leads rapidly to pantropic infection. Cells derived from all three germ layers were infected with RV, but those of endodermal and mesodermal origin were the predominant targets. Infection of vascular endothelium was widespread and was associated with hemorrhage and infarction in the brain. Convalescence from acute infection was accompanied by mononuclear cell infiltrates at sites containing RV DNA. Viral DNA was also detected in endothelium, fibroblasts and smooth muscle myofibers four weeks after inoculation. Further examination of these cells as potential sites of persistent infection is warranted.

Lethal exacerbation of Pneumocystis carinii pneumonia in severe combined immunodeficiency mice after infection by pneumonia virus of mice

Mice homozygous for the mutant allele scid (severe combined immunodeficiency) have been described as excellent models for Pneumocystis carinii (Pc) pneumonia (PCP), a major health problem in patients with acquired immune deficiency syndrome (AIDS) and other immunodeficiency states. Other microorganisms have been shown to infect AIDS patients simultaneously with Pc, but whether one opportunist is able to directly influence the pathogenicity of another has not been determined previously. We have deliberately coinfected scid mice (with extent Pc infection) with a variety of primarily pneumotropic viruses and bacteria and have identified pneumonia virus of mice as causing a dramatic increase in the density of Pc organisms and the morbidity due to PCP in immunodeficient scid mice. This finding has clinical significance in the management of PCP, in that the identification and treatment of coinfecting pneumotropic pathogens may be as important as treatment targeted at Pc. A search for other synergistic (or antagonistic) microorganisms and determination of their mechanism(s) of action in altering the progression of PCP is indicated.

A serologic survey for viruses and Mycoplasma pulmonis among wild house mice (Mus domesticus) in southeastern Australia

Plasma samples from 267 wild house mice (Mus domesticus) trapped at 14 sites in southeastern Australia were screened for antibody to 14 viruses normally associated with laboratory-reared rodents and to Mycoplasma pulmonis. Serologic prevalence was high for murine cytomegalovirus (99%, n = 94), murine coronavirus (95%), and murine rotavirus (74%). Samples from mice collected at all sites contained antibody to these viruses. The serologic prevalence was lower for mouse adenovirus, strain K87 (37%), parvovirus (33%), and reovirus type 3 (28%), with substantial site-to-site variation. Plasma from mice collected at 12 sites contained mouse adenovirus or reovirus antibody, and samples from mice at eight sites contained parvovirus antibody. Parvovirus-antibody positive mice were typically from high density populations or from low density populations that had recently declined from high density. Antibody to lymphocytic choriomeningitis virus (LCMV) and Sendai virus occurred at only three sites, and the serologic prevalence was very low (9.6% and 1.8%, respectively). All of the LCMV-positive mice were from northeastern New South Wales. The presence of this zoonotic virus in a mouse plague-prone region raises questions about human health risks resulting from cohabitation with large numbers of mice. It appeared that mouse populations at high density or declining from high density had higher prevalence of viral antibody than populations that had been at low or moderate density for some time. Thus, viral epizootics may occur among high-density populations and may be responsible for or precipitate declines in mouse density. These data raise the possibility of rodent viruses having potential as biological control agents.

The cellular and molecular pathogenesis of coronaviruses

Coronaviruses cause a wide spectrum of diseases in humans and animals but generally fall into two classes, with respiratory or enteric tropisms. Mouse hepatitis virus (MHV) and rat coronaviruses are the viruses most frequently encountered in the laboratory animal setting. This review focuses primarily on the cellular and molecular aspects of MHV pathogenesis. The high mutation and recombination rates of coronaviruses lead to a diverse, ever-changing population of MHV strains. The spike (S) protein is the most variable coronavirus protein and is responsible for binding to cell surface receptors, inducing cell fusion and humoral and cellular immunity. Differences within the S protein of different MHV strains have been linked to their variable tropisms. Since immunity to MHV is strain-specific, seropositive mice can be reinfected with different strains of MHV. Natural infections with MHV are acute, with persistence occurring at the population level, not within an individual mouse, unless it is immunocompromised. Age, genotype, immunologic status of the mouse, and MHV strain influence the type and severity of disease caused by MHV. Interference with research by MHV has been reported primarily in the fields of immunology and tumor biology and may be a reflection of MHV's capacity to grow in several types of immune cells. While many methods are available to diagnose coronavirus infection, serologic tests, primarily ELISA and IFA, are the most commonly used. MHV is best managed on a preventive basis. Elimination of MHV from a population requires cessation of breeding and halting the introduction of naive mice into the population.

Analysis of the complete sequence of a muscle calcium-binding protein of Schistosoma mansoni

The complete sequence of the cDNA encoding a 20 kDa calcium-binding protein of Schistosoma mansoni (Sm20) has been determined. The predicted amino acid sequence contains 4 EF hand domains but examination of the predicted secondary structure of Sm20, together with the specific residues in each calcium-binding domain, suggests that only 1 EF hand (domain IV) is functional. Sm20 is most homologous to calmodulin, troponin C and the regulatory light-chain of myosin, particularly those of invertebrates. However, troponin C and the regulatory light-chain of myosin can be distinguished from Sm20 by size and by their differential levels of expression during the life-cycle. Sm20 also appears to be distinct from calmodulin but may be functionally equivalent to the soluble sarcoplasmic calcium-binding proteins of molluscs and crustacea which may act as a reservoir for calcium in muscle. Sm20 is encoded by a small multi-gene family whose members are clustered within a 15 kb region of the genome. A 20 kDa antigen, cross-reactive with Sm20, is expressed in Schistosoma haematobium, Fasciola hepatica and Paragonomus mexicanus.

Lyme borreliosis in genetically resistant and susceptible mice with severe combined immunodeficiency

The evolution of Lyme borreliosis was examined in genetically resistant C.B-17 and susceptible C3H/He(C3H) mice homozygous for the severe combined immune deficiency (scid) gene, or their immunocompetent counterparts. The C.B-17, C.B-17-scid, C3H, and C3H-scid mice were inoculated intradermally with 10(4) Borrelia burgdorferi and examined on days 14, 21, 30, 45, and 60 after inoculation. Spirochetemia was detected through 30 days, but was cleared in all groups by 45 days. Kidney and brain were inconsistently culture positive, but spleen and ear punch samples were positive in most mice. Immunocompetent C.B-17 and C3H mice seroconverted with equivalent IgG titers to B. burgdorferi, while C.B-17-scid and C3H-scid mice did not seroconvert. Arthritis occurred in nearly all joints examined in all genotypes on day 14, was of equal severity among C.B-17, C.B-17-scid, and C3H mice, but was more severe in C3H-scid mice. By days 30 and 45, arthritis began to resolve in immunocompetent mice, with C3H mice having more severe disease than C.B-17 mice. Arthritis persisted in C.B-17-scid and C3H-scid mice. Carditis occurred to an equal degree in all groups on day 14, remained active in scid mice, but regressed in immunocompetent mice at later intervals. Many spirochetes were visualized with silver stain in inflamed synovial tissues of scid mice, and were present in other tissues in smaller numbers. These studies show that specific immunity is not involved in arthritogenesis or genetically determined susceptibility to arthritis, but is involved in arthritis and carditis regression.

Multisystem obstruction with cholestasis, pigmentary retinopathy, and cleft palate: a new syndrome?

A number of systemic abnormalities associated with cholestasis have been reported in the literature. This paper describes two unrelated patients with cholestasis and an unusual constellation of abnormalities including cleft palate/lip, hydronephrosis/hydroureter, retinal pigmentation, and intestinal septum.

Schistosoma mansoni: adult males and females differentially express antigens encoded by repetitive genomic DNA

Two repetitive DNA sequences have been characterized from Schistosoma mansoni which were transcribed into mRNAs and translated to give two families of cross-reactive proteins. One DNA element, which was present as a 230 bp Pst I fragment was arranged in tandem arrays of at least 17 copies in the genome. The second element, which could be localized to a 1800 bp Pst I fragment, was dispersed in the genome. The 1800 bp repeat was found on the mRNA encoding the 45 kDa polypeptide precursor of a potential surface antigen. This precursor was post-translationally modified to give a 50 kDa antigen (Sm50) which was expressed from the cercaria to the adult worm and in the egg. However, a proportion of this antigen was differentially modified in females and eggs to give a 60 kDa form. Two copies of the 230 bp repeat and one copy of the 1800 bp repeat were found on a second cDNA clone. The antiserum raised against the fusion protein of this clone recognized a family of cross-reactive proteins ranging from 14 to 70 kDa in size. The members of this family were also differentially expressed between the sexes. Consequently, two families of antigens have been identified which were both encoded by repetitive DNA elements and whose members were both differentially expressed in adult male and female worms.

Duration and strain-specificity of immunity to enterotropic mouse hepatitis virus

We examined the duration and strain-specificity of immunity to enterotropic mouse hepatitis virus (MHV). Two strains of enterotropic MHV (MHV-Y and MHV-RI) were determined to be distinct virus strains by serum neutralization and by enzyme immunoassay. BALB/cByJ mice immunized by oral infection with either MHV-Y or MHV-RI developed serum MHV IgG titers that remained stable for more than 6 months. The animals were protected from reinfection with the homologous virus strain at 1 and 6 months after an initial immunizing infection, based on intestinal histology and polymerase chain reaction for a 375-base-pair segment of the membrane glycoprotein gene. Immunity was also fully protective against challenge with the heterologous strain 1 month after initial immunization and partly protective after 6 months. Maternally-derived passive immunity prevented MHV infection in 1-week-old pups challenged with the homologous strain of MHV, and pups challenged with the heterologous virus strain were partially protected.

Dexamethasone and bacterial meningitis. A meta-analysis of randomized controlled trials

A meta-analysis of 5 randomized, controlled trials using dexamethasone as adjunctive therapy in the treatment of bacterial meningitis in children was done to assess the efficacy in reducing sequelae. A 6th study including both children and adults was analyzed separately. Results of the 5 pediatric studies indicated no significant difference in case-fatality rate between the placebo and dexamethasone groups. Significantly more neurologic sequelae were found in the placebo group during the period from discharge from hospital to 6 weeks after discharge (relative risk [RR] = 1.99, 95% confidence interval [CI] 1.13 to 3.53) and during the period beginning 6 months after discharge (RR = 3.90, 95% CI 1.72 to 8.85). The incidence of neurologic sequelae from 6 weeks to 6 months after discharge, though less with dexamethasone administration, did not reach statistical significance. The frequency of bilateral hearing loss was significantly greater in the placebo group (RR = 4.12, 95% CI 1.74 to 9.79), but unilateral loss was not statistically different in the two groups. Dexamethasone administration in addition to antimicrobial therapy appears to be effective in reducing neurologic sequelae and bilateral hearing loss associated with bacterial meningitis in children.

Targeted mutations that ablate either the adenylate cyclase or hemolysin function of the bifunctional cyaA toxin of Bordetella pertussis abolish virulence

Bordetella pertussis, the causative agent of whooping cough, secretes several toxins implicated in this disease. One of these putative virulence factors is the adenylate cyclase (AC) toxin that elevates intracellular cAMP in eukaryotic cells to cytotoxic levels. This toxin is a bifunctional protein comprising both AC and hemolysin (HLY) enzymatic domains. The gene encoding the AC toxin (cyaA) is expressed as part of an operon that includes genes required for secretion or activation of the toxin. Because of this genetic organization, it is difficult to create B. pertussis mutants of cyaA that are ablations of a single enzyme function by conventional means, such as transposon mutagenesis. Therefore, to clarify the role of individual toxin functions in the virulence of B. pertussis, we have used site-directed or deletion mutagenesis and genetic recombination to specifically target the cyaA gene of B. pertussis to produce mutants that lack only the AC or HLY activity of this toxin. A point mutant of B. pertussis with abolished AC catalytic activity was greater than 1000 times less pathogenic to newborn mice than wild-type bacteria, directly demonstrating the importance of the AC toxin in pertussis virulence. Similarly, an in-frame deletion mutant of B. pertussis that lacks HLY is equally avirulent, supporting observations that the HLY domain plays a critical role in AC toxin entry into cells. Furthermore, the genetically inactivated AC toxin produced by the point mutant is antigenically similar to the native toxin, suggesting that this strain may be useful in the development of pertussis component vaccines.

Fimbriation of Pseudomonas cepacia

Fimbriae (pili) on the surface of bacteria have been suggested to facilitate adherence to mucosal epithelial surfaces. Three Pseudomonas cepacia cystic fibrosis isolates were screened for their ability to agglutinate erythrocytes (HA), a characteristic of some fimbrial types. One strain, designated PC103, was HA+, while another, PC109, was HA-. A fimbriated (f+) HA+ derivative of PC109 (PC2(13)) was selected by repeated erythrocyte adsorption. The two HA+ strains were shown by transmission electron microscopy to possess fimbriae which averaged 4.8 +/- 1.36 nm in width and 200 to greater than 2,100 nm in length (PCE2(13)) and 3.4 to 11.4 nm in diameter and 280 to 720 nm in length (PC103). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of outer membrane proteins prepared from PC103, PC109, and PCE2(13) indicated that the putative fimbrial subunit had a mass of 16 kDa. Western blot (immunoblot) analysis of sheared cell supernatants indicated that the 16-kDa subunit from PC103 and PCE2(13) reacted with antibody to the P. aeruginosa PAK pilin subunit. Southern blot analysis of a SalI digest of PC103 DNA showed DNA fragments which hybridized to P. aeruginosa PAK probes containing either the pilin structural gene (pilA) or the pilin accessory genes (pilB, -C, and -D) but not the conserved N-terminal region of pilA. A 15-kb band was common to both hybridizations, indicating that this fragment contains the PC103 fimbrial gene cluster. These results indicated the presence of homology between P. aeruginosa PAK and PC103 fimbriae but also suggested that the P. cepacia fimbriae are not type IV-like. The importance of fimbriae in adherence to A549 cells (type II pneumocytes) was assessed with PC109 (f-) and PCE2(13) (f+). PCE2(13) had an approximately 20-fold-higher level of adherence to A549 cells than PC109. This suggested that fimbriation of P. cepacia is associated with increased adherence in vitro.

The pathogenesis of infection with minute virus of mice depends on expression of the small nonstructural protein NS2 and on the genotype of the allotropic determinants VP1 and VP2

Neonatal C3H/He mice were oronasally inoculated with similar doses of four genotypes of minute virus of mice (MVM). MVMp, a fibroblast-specific variant, caused an asymptomatic infection. MVM(1035), a chimera which had the allotropic determinant of virulent MVMi inserted onto an MVMp background, caused a lethal infection and renal papillary infarcts, the hallmark of MVMi infection. MVMi(NS2-1990), the virulent lymphocyte-specific variant mutated to eliminate NS2 synthesis, was infectious but caused an asymptomatic infection. Sequential virus titration, histology, in situ hybridization with a full-length MVMi genomic probe, and immunohistochemistry for viral capsid antigen were used to compare the pathogenesis of infection with the four MVM genotypes. Infectious virus was recovered from multiple organs of mice infected with MVMi, MVMp, and MVM(1035) but not from mice infected with MVMi(NS2-1990). MVMp titers were lower than MVMi titers in all organs except the intestine. MVM(1035) titers were higher than MVMi titers in all organs except the blood. MVMp was localized to connective tissue elements of the intestine, to cells in mesenteric lymph nodes, and rarely to cells in other organs. MVM(1035) was localized to multiple organs and shared the same target cells, endothelium, lymphoid cells, and hematopoietic cells, as MVMi. MVM(1035) also replicated in external germinal cells of the cerebellum and smooth muscle cells of the stomach and colon, which were not targets of MVMi or MVMp infection. MVMi(NS2-1990) replicated to a limited degree in some MVMi target organs.

Monoclonal antibody to Pneumocystis carinii. Comparison with silver stain in bronchial lavage specimens

Monoclonal 3F6 anti-Pneumocystis carinii antibody (MAB-3F6) was used to stain cell blocks from 164 bronchial lavage specimens from patients with the acquired immune deficiency syndrome (AIDS) and AIDS-related complex and compared with slides stained with Grocott's modification of the Gomori methenamine silver stain. Pneumocystis organisms were present in 83 of 164 cases using MAB-3F6 stain, whereas Grocott's modified silver stain demonstrated Pneumocystis organisms in 48. MAB-3F6 demonstrated Pneumocystis organisms in 38 cases with negative silver stains, whereas silver stain identified Pneumocystis organisms in only three MAB-3F6-negative cases. Of 70 patients with clinical Pneumocystis pneumonia at the time of the specimen was obtained, 59 had MAB-3F6-positive specimens, whereas 39 had organisms detected using Grocott's modified silver stain. Of 37 patients without clinically apparent Pneumocystis pneumonia any time in their course, 4 had abundant organisms and 33 had negative stains with MAB-3F6. MAB-3F6 detected Pneumocystis organisms in 22 of 31 cases of Pneumocystis pneumonia that had no organisms identified using Grocott's silver stain (X2 = 5.76, P = 0.016). MAB-3F6 immunochemical staining is a more sensitive method than Grocott's modified silver stain to detect Pneumocystis organisms.

Nonspecific proliferative responses of murine lymphocytes to Borrelia burgdorferi antigens

Proliferative responses of naive splenocytes to Borrelia burgdorferi antigens from mice susceptible (C3H) and resistant (BALB) to Lyme borreliosis were investigated. B. burgdorferi spirochetes and recombinant outer surface proteins, OspA and OspB, were found to induce nonspecific proliferation of naive splenocytes from both strains of mice. Cell purification studies localized nonspecific proliferation to the B cell-enriched fraction. B. burgdorferi, OspA, and OspB were found to induce IgM and IgG synthesis in vitro. The mitogenic effect of B. burgdorferi was dissimilar to that of lipopolysaccharide (LPS), in that B cells from C3H/HeJ mice (LPS-unresponsive) responded at levels comparable to those from C3H/HeNCrlBr mice. These results emphasize the need for caution in the study of antigen-specific proliferation for B. burgdorferi.

Antibiotic resistance in pediatric pathogens

The prevalence of antibiotic resistance is increasing in pediatric pathogens. Methicillin resistance in Staphylococcus aureus and in S. epidermidis, and erythromycin resistance in group A streptococci are becoming major problems. Fortunately, all three species remain susceptible to vancomycin. In certain parts of the world, Haemophilus influenzae b that are resistant to a number of antibiotics are being recognized. Antibiotic therapy of pediatric infections in the future will continue to rely on yet-to-be developed agents.

Effects of acromelic acid A on the binding of [3H]-kainic acid and [3H]-AMPA to rat brain synaptic plasma membranes

1. The ability of acromelic acid A to inhibit [3H]-kainic acid and [3H]-(RS)-alpha-amino-3-hydroxy-5-methyloxazole-4-propionic acid ([3H]-AMPA) binding to rat brain synaptic plasma membranes was investigated by equilibrium radioligand binding assay. 2. Kinetic analysis of [3H]-kainic acid binding demonstrated the existence of two kainate binding sites in this tissue preparation and yielded equilibrium dissociation constants for [3H]-kainic acid of KD = 0.4 nM and KD = 20.8 nM. 3. Kainic acid and domoic acid both appeared to displace [3H]-kainic acid from a single binding site with equilibrium binding constants of KD = 19.4 nM and Ki = 14.5 nM respectively. Acromelic acid A exhibited a biphasic inhibition of [3H]-kainic acid binding to synaptic membranes with binding affinities of Ki = 15.1 nM and Ki = 1.49 microM. 4. In the absence of chaotropic ions, the order of potency of inhibition of [3H]-AMPA binding was acromelic acid A (Ki = 26 nM) greater than AMPA (KD = 184 nM) greater than domoic acid (Ki = 499 nM). 5. The inclusion of 100 mM thiocynanate ion in the [3H]-AMPA binding assay resulted in a change in the order of potency to: AMPA (KD = 160 nM) greater than acromelic acid A (Ki = 289 nM) greater than domoic acid (Ki = 9.02 microM). 6. These results show that acromelic acid A distinguishes two kainate binding sites in rat brain synaptic plasma membranes and in addition, that in the absence of chaotropic ions, acromelic acid A is the most potent displacer of [3H]-AMPA binding yet described.

Responses of mice to murine coronavirus immunization

Oral and/or intranasal inoculation of susceptible mouse genotypes with the JHM strain of mouse hepatitis virus (MHV-JHM) consistently results in T cell dysfunction as reflected by in vitro proliferative responses to mitogens or allogeneic cells. One approach to examining the mechanism responsible for the observed functional T cell suppression is to determine whether virus replication is required for its induction. To this end, mice were inoculated oronasally with MHV-JHM that was inactivated with short-wave ultraviolet light, beta-propiolactone or psoralen. Mice were also inoculated with live MHV-JHM after recovery from homotypic or heterotypic MHV infection. Spleen cells from BALB mice inoculated oronasally with inactivated MHV-JHM yielded extremely variable in vitro proliferative responses after concanavalin A stimulation. MHV-susceptible mice exposed oronasally or intraperitoneally to virus inactivated by any of the minimum effective treatments failed to seroconvert. Immunization with psoralen-treated virus intraperitoneally in Freund's complete adjuvant or oronasally failed to protect from live virus challenge, but survivors had elevated virus-specific serum IgG antibody titers compared to mock-immunized controls at two weeks post-challenge. Spleen cells from mice that were challenged after recovery from homotypic live virus infection did not exhibit the profound in vitro T cell suppression normally observed during the acute stage of primary infection. In contrast, MHV-JHM challenge of mice vaccinated with heterotypic live MHV-S resulted in significantly depressed in vitro T cell function. The combined data suggest that either virus replication or exposure to more concentrated antigen may be required for induction of the dramatic T cell dysfunction that occurs as a consequence of MHV-JHM infection as well as for a detectable MHV-specific humoral response.

Viremic dissemination of mouse hepatitis virus-JHM following intranasal inoculation of mice

Using a sensitive infant mouse bioassay to detect infectious virus, the pattern of mouse hepatitis virus (MHV) JHM dissemination in blood and other tissues was examined during the first 5 days following intranasal inoculation. MHV replicated in nasal turbinates of both susceptible BALB and resistant SJL mice from days 1 through 5, but BALB mice had higher titers on days 1 and 2. Viremia was detectable on days 1 through 5 in BALB mice, but only on days 3 and 5 in SJL mice. Transient virus replication occurred in the lungs of both mouse genotypes at 1 and 2 days, then ceased. This correlated with more consistently demonstrable virus in blood collected from the left atrium of the heart, compared to jugular vein, portal vein and right atrial blood. Virus was associated equally with the plasma and cellular fractions of blood on day 3, but was primarily in the buffy coat of the cellular fraction on day 5. Interferon-alpha/beta was detected in serum and spleen, but not liver or brain of BALB mice or in any tissue of SJL mice. BALB serum and spleen interferon was first detected at 36 h, peaked between 48 and 72 h, and was undetectable by 108 h. The distribution of virus in nose, cervical, axillary and mesenteric lymph nodes, spleen, Peyer's patch, thymus, bone marrow and liver was examined at 1, 2, and 3 days. The resulting pattern suggested lymphatic spread of virus to cervical lymph node and mesenteric lymph node as pathways of dissemination in addition to viremia.

Detection of rodent coronaviruses in tissues and cell cultures by using polymerase chain reaction

A polymerase chain reaction (PCR) method was developed for the detection of rodent coronaviruses in biological material by using reverse transcriptase and two primers which flanked an M gene sequence of 375 bp. PCR detected all of 11 different strains of mouse hepatitis virus (MHV) as well as rat sialodacryoadenitis virus but not bovine coronavirus or human coronavirus strains OC43 and 229E. The M gene sequences of bovine coronavirus and human coronavirus OC43 are homologous to that of MHV, but minor differences exist in the primer regions, preventing annealing of the primers. For detecting MHV-Y in tissue samples, PCR was faster than and at least as sensitive as either of the two bioassays (infant mouse bioassay and mouse antibody production test) currently used for MHV diagnostic purposes.

Disposition of drugs in cystic fibrosis. III. Acetaminophen

The disposition of acetaminophen after oral administration was investigated in adults with cystic fibrosis (n = 5) and in age-matched healthy control subjects (n = 5). The total plasma clearance of acetaminophen was found to be greater (p less than 0.025) in subjects with cystic fibrosis (0.362 +/- 0.081 L/hr/kg) than in control subjects (0.247 +/- 0.022 L/hr/kg). This difference in clearance was found to be primarily attributable to a greater metabolic clearance of acetaminophen to acetaminophen sulfate (0.080 +/- 0.023 L/hr/kg for subjects with cystic fibrosis and 0.045 +/- 0.008 L/hr/kg for control subjects; p less than 0.05) and to a greater metabolic clearance of acetaminophen to acetaminophen glucuronide (0.189 +/- 0.051 L/hr/kg for subjects with cystic fibrosis and 0.114 +/- 0.017 L/hr/kg for control subjects; p less than 0.05) in persons with cystic fibrosis. Of the mechanisms that may be responsible for these differences, the most likely is enhanced activity (in subjects with cystic fibrosis) of the transferases that mediate the metabolism of acetaminophen to acetaminophen sulfate and acetaminophen glucuronide, respectively.

Inability to express fimbriae results in impaired ability of Haemophilus influenzae b to colonize the nasopharynx

We cloned into the structural fimbrial subunit gene from a fimbriated Haemophilus influenzae b a 1.5-kb kanamycin resistance gene. The resultant strain (RKAW5) was tested by Southern analysis, hemagglutination, and electron-micrographic examination to confirm gene inactivation. In comparison with the parent, RKAW5 exhibited a significant decrease in adherence to human buccal epithelial cells and in nasal colonization of yearling rhesus monkeys.

Orientational Disorder in Solvent-Free Solid C 70

The high-temperature structure of solvent-free C(70) has been determined with high-resolution x-ray powder difraction and electron microscopy. Samples crystallized from solution form hexagonal close-packed crystals that retain an appreciable amount of residual toluene, even after prolonged heating. Samples prepared by sublimation, which contain no detectable solvent, are primarily face-centered cubic with some admixture of a hexagonal phase. The relative volume of the hexagonal phase can be further reduced by annealing. The structures of both phases are described by a model of complete orientational disorder. The cubic phase contains an appreciable density of stacking faults along the [111] direction.

Schistosoma mansoni: immuno-localization of the calcium binding protein Sm20

The 20 kDa calcium binding protein of Schistosoma mansoni, Sm20, is expressed in all stages of the life cycle from the cercaria to the adult worm and in the egg, with equal levels of Sm20 present in adult male and female worms. Localization of Sm20 by immuno-electron microscopy using Sm20-specific antisera and the protein A gold technique demonstrated that the majority of Sm20 is expressed in muscle but that it may also be expressed at low levels in the tegument. These results suggest that Sm20 plays a role in the calcium mediated regulation of muscle contraction. However, it is not clear whether Sm20 acts as a reservoir for calcium in muscle or is directly involved in the regulatory mechanisms of contraction.

5,8-disubstituted indolizidines: a new class of noncompetitive blockers for nicotinic receptor-channels

A series of 8-methyl-5-substituted indolizidines inhibit binding of the noncompetitive blocking agent [3H]perhydrohistrionicotoxin to muscle-type nicotinic acetylcholine receptor-channels in membranes from Torpedo electroplax. The Ki values range from 0.16 to 1.12 microM, making these alkaloids among the most potent ligands for this site. Unlike most noncompetitive blockers, the potencies of the 8-methyl-5-substituted indolizidines are reduced in the presence of carbamylcholine. Indolizidine 205A (8-methyl-5-(4-pentynyl)indolizidine) is unique in enhancing binding of [3H]perhydrohistrionicotoxin by 1.5-fold. The enhancement is at a maximum at 0.01 to 0.1 microM, followed by progressive inhibition with an IC50 of about 20 microM. In the presence of carbamylcholine, which itself enhances binding of [3H]perhydrohistrionicotoxin, indolizidine 205A causes only an inhibition of binding with an IC50 of about 10 microM. Indolizidines with a hydroxy substituent on the 8-methyl group have very low activity. None of the indolizidines affect binding of [125I]alpha-bungarotoxin to acetylcholine recognition sites. In pheochromocytoma PC12 cells, indolizidine 205A has no agonist activity, but only inhibits carbamylcholine-elicited 22Na+ influx. The profile of potencies for the 8-methyl-5-substituted indolizidines is similar in electroplax membranes and PC12 cells. Indolizidines 205A and 209B (8-methyl-5-pentylindolizidine) have no apparent effect on desensitization of receptors in PC12 cells. The 5,8-disubstituted indolizidines appear to represent an atypical and potent class of noncompetitive blockers for muscle-type and ganglionic nicotinic receptor-channels.

Pneumocystis carinii pneumonia in the rat model

Groups of barrier-raised but not certified virus-free Sprague-Dawley rats, obtained from the same source over the course of several years, were placed on an identical immunosuppressive regimen. This caused reactivation of latent Pneumocystis carinii infection, manifest as P. carinii pneumonia (PCP) of varying severity. Rats were euthanized after 9-12 wk of immunosuppression. An assessment of the severity of the induced PCP was made, based on the total number of organisms extracted from the lungs and their ability to proliferate in short-term cell culture. Serum samples obtained at sacrifice were tested by indirect immunofluorescence for antibodies to coronavirus, parvovirus, Sendai virus, pneumonia virus of mice (PVM) and Mycoplasma pulmonis. A total of 60 rats were examined. Thirty-four of these (57%) developed moderate or severe PCP. No antibodies were detected to either coronavirus or Mycoplasma pulmonis in any of the rats. Although antibodies were detected to parvovirus in 13/60 (22%), to PVM in 29/60 (48%), and to Sendai virus in 47/60 (78%), there was no apparent correlation between the presence or absence of antibodies to these agents and the severity of PCP. Sequential observations during the course of immunosuppression are needed to clarify the role of concomitant infections in the development of PCP.

Laser-induced plasma formation in Xe, Ar, N(2), and O(2) at the first four Nd:YAG harmonics

Irradiance values have been measured for the onset of laser-induced plasma formation in Xe, Ar, N(2), and O(2) at pressures from 760 to 25 Torr at wavelengths of 1.064, 0.532, 0.355, and 0.266 microm. These values have been compared with the results of other workers who used similar experimental setups. There is agreement within a factor of 4 when irradiance values are compared and within a factor of 2 when ratios of irradiance values for different gasses are compared. Comparisons among workers who used widely different pulse lengths indicate that the onset of plasma formation is measured better by energy fluence than by irradiance.

Disposition of drugs in cystic fibrosis. II. Hepatic blood flow

To determine whether the increased clearance of high extraction-ratio drugs in cystic fibrosis is caused by an increase in hepatic blood flow, the blood flow in main branches of the hepatic vein and portal vein was measured by use of noninvasive duplex ultrasound scanning in 10 adult subjects with cystic fibrosis and in 10 healthy age-, gender-, and height-matched control subjects. No statistically significant differences between subjects with cystic fibrosis and control subjects were detected in either the hepatic vein (217 +/- 103 ml/min for subjects with cystic fibrosis versus 211 +/- 135 ml/min for control subjects) or the portal vein (205 +/- 114 ml/min for subjects with cystic fibrosis versus 190 +/- 101 ml/min for control subjects) blood flows. These data indicate that a large (greater than or equal to 100%) increase in the clearance of high extraction-ratio drugs in patients with cystic fibrosis is unlikely to be primarily caused by an increase in hepatic blood flow. It is probable that alternative mechanisms such as enhanced secretory or metabolic pathways account in large part for increases in clearance of high extraction-ratio drugs.

Persistent rat parvovirus infection in individually housed rats

The duration of infection with rat virus (RV), an autonomous rodent parvovirus, was examined at multiple intervals over 6 months in rats inoculated by the oronasal route at 2 days of age or 4 weeks of age and individually housed after weaning to prevent cross-infection. Infectious virus was recovered by explant culture from 32 of 80 rats inoculated as pups and was detected as late as 6 months after inoculation. Rats inoculated as juveniles developed acute infection, but virus was not detected beyond 7 weeks after inoculation. Tissues from rats in both age groups were surveyed for RV DNA by Southern blotting using a double-stranded DNA probe made from a 1700 bp cloned fragment of RV spanning map units 0.19-0.52. Band patterns representative of acute infection (juvenile rats) were consistent with the replicating form of RV DNA, whereas patterns representative of persistent infection (rats inoculated as pups) were suggestive of defective or non-productive viral replication.

Helicobacter pylori infection in children

Helicobacter pylori was sought prospectively by culture of antral biopsy, histology and serology (IgG and IgA) in 440 consecutive endoscopies on children to determine the prevalence, clinical presentation and histological features of H. pylori infection in our population. Twenty-eight patients had H. pylori (8% overall). The mean age of infected patients was significantly higher than that of non-infected patients (P less than 0.0001). No patient under 5 years of age had H. pylori isolated. Overall, there was no significant difference in clinical presentation between those with and those without H. pylori infection, but 23% of patients 5 and 26 years of age who presented with abdominal pain as the indication for their endoscopy had H. pylori isolated. Macroscopic changes ranged from no abnormality to frank ulceration, but the typical antral mamilliform changes were 100% predictive of infection. Fifty-eight per cent of patients with duodenal ulcers, but only 17% with gastric ulcers had H. pylori infection. Histological gastritis was present in 144 patients (including all H. pylori positive patients). None of the patients with another definable cause for gastritis had H. pylori isolated. In conclusion, H. pylori is an important cause of primary gastritis in our population, occurring in children over 5 years of age. Culture of an antral biopsy should be performed in children over this age undergoing endoscopy for the investigation of abdominal pain and, more particularly, in those with peptic ulceration.

Pathogenesis of infection with a virulent allotropic variant of minute virus of mice and regulation by host genotype

Neonates of various inbred strains of mice expressed three susceptibility phenotypes in response to infection with the lymphocyte-specific variant of minute virus of mice (MVMi). MVMi caused asymptomatic infections in C57BL/6 (B6) mice, lethal infections with intestinal hemorrhage in DBA/2 mice, and lethal infections with renal papillary hemorrhage in BALB/c, SWR, SJL, CBA, and C3H (H) mice. Sequential virus titration, histology, in situ hybridization with a full-length MVMi genomic probe, and immunohistochemistry for viral capsid antigen were used to compare the pathogenesis of MVMi infection in B6 and H mice. Peak infectious virus titers in heart, lung, liver, spleen, kidney and intestine did not differ between strains but brains of B6 mice, unlike H mice, were refractory to infection. Lesions in H mice consisted of renal papillary infarcts and accelerated involution of hepatic erythropoietic foci. No lesions were seen in B6 mice. In situ hybridization and immunohistochemistry indicated that three cell types were primary targets of MVMi; endothelium, lymphocytes, and hepatic erythropoietic precursors. Renal papillary infarcts in H mice were associated with virus replication in endothelial nuclei of the vasa recta. In contrast to the parity of infectious virus titers between strains, fewer cells in target organs of B6 mice were labeled with the MVMi probe then were labeled in H mice and fewer cells expressed viral capsid antigen. These results indicate (a) that the allotropic variants of minute virus of mice may be useful tools to dissect molecular mechanisms of parvovirus virulence, (b) that the virulence of MVMi for neonatal mice does not reside in its lymphotropism, and (c) that genetic susceptibility to lethal MVMi infection may result from overproduction of noninfectious virus products.

Feasibility of semen collection and cryopreservation during chemotherapy

Collection and cryopreservation of semen was undertaken in a 40-year-old man undergoing combination cyclophosphamide-doxorubicin-vincristine-prednisone chemotherapy for diffuse large cell lymphoma. Semen samples worthy of cryopreservation could be obtained through 39 days of therapy, with azoospermia observed after 70 days. Although pregnancy has not been attempted in the current case, reports by others suggest that normal outcomes can be expected with thawed semen collected during chemotherapy.

Predictive value of oropharyngeal cultures for identifying lower airway bacteria in cystic fibrosis patients

Identifying lower respiratory pathogens in young, non expectorating cystic fibrosis (CF) patients has been problematic. Bronchial secretions are difficult to obtain, and little is known about lower airway flora in these patients. We collected simultaneous bronchial and oropharyngeal specimens in 43 CF patients in optimal respiratory status, including both expectorating (17) and nonexpectorating (26) patients, to determine the predictive value of oropharyngeal cultures for identifying lower airway pathogens. An additional goal was to characterize the lower respiratory flora of these patients. Predictive values were defined as the proportion of oropharyngeal culture results that accurately reflected the results of bronchial cultures. Predictive values of positive oropharyngeal cultures in nonexpectorating patients were 83% (95% confidence interval 36 to 100%) for Pseudomonas aeruginosa and 91% (59 to 100%) for Staphylococcus aureus. Predictive values of negative oropharyngeal cultures were lower: 70% (48 to 86%) for R aeruginosa and 80% (52 to 96%) for S. aureus. A relatively high proportion of nonexpectorating CF patients less than 10 yr old had R aerusginosa (11 of 24, 46%) or Klebsiella species (5 of 24, 21%) in their lower airways. The isolation of Klebsiella was associated with younger age (p = 0.03) and recent administration of antistaphylococcal antibiotics (p = 0.05). Our results suggest that oropharyngeal cultures yielding R aeruginosa or S. aureus are highly predictive, but such cultures lacking these organisms do not rule out the presence of these pathogens in the lower airways of CF patients.

Superovulation fails to increase human blastocyst yield after uterine lavage

Uterine lavage affords the potential for non-invasive human blastocyst recovery, with obvious potential for preimplantation genetic diagnosis. In an effort to duplicate in women the multiple blastocyst recovery per cycle that can be achieved in several other species, we initiated a programme in which fertile women underwent superovulation, followed by lavage and embryo collection. We superovulated 15 fertile women, aged 21-40, in 29 cycles using one of four regimens. Insemination was by either intercourse or artificial intracervical donor insemination with cryopreserved sperm from men of proven fertility. In 28 of 29 cycles, the uterus was lavaged daily for 1, 2, or 3 days between 5 and 10 days after human chorionic gonadotropin (hCG) administration or luteinizing hormone (LH) surge. Almost total fluid volume was recovered in every lavage. There were no retained pregnancies and no complications. Surprisingly, only two morulae, one blastocyst, and four unfertilized ova were recovered. Thus, alterations in ovulation induction, insemination timing, or lavage techniques must be contemplated in order to increase the blastocyst yield and thus fulfil the potential of uterine lavage for preimplantation diagnosis.