Structures of the Hepaci-, Pegi-, and Pestiviruses envelope proteins suggest a novel membrane fusion mechanism

Enveloped viruses encode specialised glycoproteins that mediate fusion of viral and host membranes. Discovery and understanding of the molecular mechanisms of fusion have been achieved through structural analyses of glycoproteins from many different viruses, and yet the fusion mechanisms of some viral genera remain unknown. We have employed systematic genome annotation and AlphaFold modelling to predict the structures of the E1E2 glycoproteins from 60 viral species in the Hepacivirus, Pegivirus, and Pestivirus genera. While the predicted structure of E2 varied widely, E1 exhibited a very consistent fold across genera, despite little or no similarity at the sequence level. Critically, the structure of E1 is unlike any other known viral glycoprotein. This suggests that the Hepaci-, Pegi-, and Pestiviruses may possess a common and novel membrane fusion mechanism. Comparison of E1E2 models from various species reveals recurrent features that are likely to be mechanistically important and sheds light on the evolution of membrane fusion in these viral genera. These findings provide new fundamental understanding of viral membrane fusion and are relevant to structure-guided vaccinology.

Granulovirus PK-1 kinase activity relies on a side-to-side dimerization mode centered on the regulatory αC helix

The life cycle of Baculoviridae family insect viruses depends on the viral protein kinase, PK-1, to phosphorylate the regulatory protein, p6.9, to induce baculoviral genome release. Here, we report the crystal structure of Cydia pomenella granulovirus PK-1, which, owing to its likely ancestral origin among host cell AGC kinases, exhibits a eukaryotic protein kinase fold. PK-1 occurs as a rigid dimer, where an antiparallel arrangement of the αC helices at the dimer core stabilizes PK-1 in a closed, active conformation. Dimerization is facilitated by C-lobe:C-lobe and N-lobe:N-lobe interactions between protomers, including the domain-swapping of an N-terminal helix that crowns a contiguous β-sheet formed by the two N-lobes. PK-1 retains a dimeric conformation in solution, which is crucial for catalytic activity. Our studies raise the prospect that parallel, side-to-side dimeric arrangements that lock kinase domains in a catalytically-active conformation could function more broadly as a regulatory mechanism among eukaryotic protein kinases.

The viral Protein Kinase-1 (PK-1) phosphorylates the regulatory protein p6.9, which facilitates baculoviral genome release. Here, the authors combine X-ray crystallography with biophysical and biochemical analyses as well as molecular dynamics simulations to characterize Cydia pomenella granulovirus PK-1, which forms a dimer with a parallel side-to-side arrangement of the kinase domains and furthermore, they provide insights into its catalytic mechanism and evolutionary relationships with other kinases.

Structure-function analyses of two plant meso-diaminopimelate decarboxylase isoforms reveal that active-site gating provides stereochemical control

meso-Diaminopimelate decarboxylase catalyzes the decarboxylation of meso-diaminopimelate, the final reaction in the diaminopimelate l-lysine biosynthetic pathway. It is the only known pyridoxal-5-phosphate-dependent decarboxylase that catalyzes the removal of a carboxyl group from a d-stereocenter. Currently, only prokaryotic orthologs have been kinetically and structurally characterized. Here, using complementation and kinetic analyses of enzymes recombinantly expressed in Escherichia coli, we have functionally tested two putative eukaryotic meso-diaminopimelate decarboxylase isoforms from the plant species Arabidopsis thaliana We confirm they are both functional meso-diaminopimelate decarboxylases, although with lower activities than those previously reported for bacterial orthologs. We also report in-depth X-ray crystallographic structural analyses of each isoform at 1.9 and 2.4 Å resolution. We have captured the enzyme structure of one isoform in an asymmetric configuration, with one ligand-bound monomer and the other in an apo-form. Analytical ultracentrifugation and small-angle X-ray scattering solution studies reveal that A. thaliana meso-diaminopimelate decarboxylase adopts a homodimeric assembly. On the basis of our structural analyses, we suggest a mechanism whereby molecular interactions within the active site transduce conformational changes to the active-site loop. These conformational differences are likely to influence catalytic activity in a way that could allow for d-stereocenter selectivity of the substrate meso-diaminopimelate to facilitate the synthesis of l-lysine. In summary, the A. thaliana gene loci At3g14390 and At5g11880 encode functional. meso-diaminopimelate decarboxylase enzymes whose structures provide clues to the stereochemical control of the decarboxylation reaction catalyzed by these eukaryotic proteins.

Crystal structure of protein tyrosine phosphatase-2 from Cydia pomonella granulovirus

Many viral genomes encode kinase and phosphatase enzymes to manipulate pathways that are controlled by phosphorylation events. The majority of viral phosphatase genes occur in the Baculoviridae and Poxviridae families of large DNA viruses. The corresponding protein sequences belong to four major homology groups, and structures are currently available for only two of these. Here, the first structure from the third group, the protein tyrosine phosphatase-2 (PTP-2) class of viral phosphatases, is described. It is shown that Cydia pomonella granulovirus PTP-2 has the same general fold and active-site architecture as described previously for other phosphatases, in the absence of significant sequence homology. Additionally, it has a novel C-terminal extension in an area corresponding to the interface of dimeric poxvirus phosphatases belonging to the Tyr-Ser protein phosphatase homology group.

The purification, crystallization and preliminary X-ray diffraction analysis of two isoforms of meso-diaminopimelate decarboxylase from Arabidopsis thaliana

Diaminopimelate decarboxylase catalyses the last step in the diaminopimelate-biosynthetic pathway leading to S-lysine: the decarboxylation of meso-diaminopimelate to form S-lysine. Lysine biosynthesis occurs only in microorganisms and plants, and lysine is essential for the growth and development of animals. Thus, the diaminopimelate pathway represents an attractive target for antimicrobial and herbicide treatments and has received considerable attention from both a mechanistic and a structural viewpoint. Diaminopimelate decarboxylase has only been characterized in prokaryotic species. This communication describes the first structural studies of two diaminopimelate decarboxylase isoforms from a plant. The Arabidopsis thaliana diaminopimelate decarboxylase cDNAs At3g14390 (encoding DapDc1) and At5g11880 (encoding DapDc2) were cloned from genomic DNA and the recombinant proteins were expressed and purified from Escherichia coli Rosetta (DE3) cells. The crystals of DapDc1 and DapDc2 diffracted to beyond 2.00 and 2.27 Å resolution, respectively. Understanding the structural biology of diaminopimelate decarboxylase from a eukaryotic species will provide insights for the development of future herbicide treatments, in particular.

Does splenectomy in cystic fibrosis related liver disease improve lung function and nutritional status? A case series

AIMS

To review the effect of total splenectomy on lung function and nutrition in children with cystic fibrosis related liver disease (CFLD) and associated portal hypertension. The stated indications for surgery and the short and long term risks of the procedure were also documented.

METHOD

Over a 25 year period from January 1980 to June 2005, approximately 650 patients with cystic fibrosis (CF) were treated at the Royal Children's Hospital, Melbourne, Australia. Nine patients with CFLD who underwent a splenectomy during that time were identified and their medical records were reviewed.

RESULTS

FEV1% predicted dropped by -16+/-11% in the two years pre-splenectomy. This contrasts with the increase in FEV1% predicted of 2+/-16% in the two years post-splenectomy (p = 0.05). The cumulative gain in WAZ score (DeltaWAZ pre) over the two years prior to splenectomy of 0.045+/-0.69 was not significantly different from the cumulative gain in WAZ score (DeltaWAZ post) for the two years after splenectomy of 0.15+/-0.36 (p = 0.65). The average age at splenectomy was 14.8 years (SD = 3 years). The average weight of an excised spleen was 983 g (SD = 414 g). There were no deaths associated with splenectomy. The median length of follow up post-splenectomy was 6.0 years (range 0.7-15.8). There were no episodes of bacterial peritonitis or overwhelming sepsis.

CONCLUSIONS

Splenectomy may have a beneficial effect on lung function although this may not manifest itself until the second year post-splenectomy. Splenectomy in patients with CFLD appears to be a safe procedure.

Association of body composition and lung function in children with cystic fibrosis

Survival in cystic fibrosis has improved significantly in the last 30 years, with major therapeutic goals of delaying the progressive loss of pulmonary function and maintaining normal growth. Dual-energy X-ray absorptiometry (DEXA) was performed in children with cystic fibrosis (CF) to assess both bone mineral density and body composition. We hypothesised that there would be an association between body composition and pulmonary function in children with CF. Fifty subjects with CF (28 males), mean age 12.7 years, participated in the study. Body composition was determined by DEXA. Body mass index (BMI) was calculated from the ratio of weight/height2 (kg/m2). Lung function was assessed by spirometry. Most patients (78%) had mild lung disease. The mean forced expired volume in 1 sec percent predicted (FEV1% predicted) for the 50 patients was 79.2% (range, 24-117%). There was a strong association between FEV1% predicted and BMI (R=0.59, P=0.0001). Fat-free mass had positive association with pulmonary function tests (R=0.30, P=0.03). Although fat mass showed a positive correlation with pulmonary function, this association did not reach statistical significance. In our group of children with CF and mild lung disease, pulmonary function was more strongly associated with BMI than with fat and fat-free mass.

Effect of gluten-free diet and adherence on growth and diabetic control in diabetics with coeliac disease

AIMS

To study the effect of gluten-free diet on growth and diabetic control of children with type 1 diabetes mellitus and coeliac disease.

METHODS

Twenty one children (mean age 7.5 years, range 1.6-12.9) with type 1 diabetes, primarily initially identified on the basis of symptoms and consecutively diagnosed with coeliac disease by biopsy over a 10 year period, were matched by sex, age at onset, and duration of diabetes with two diabetic controls without coeliac disease. Weight, height, haemoglobin A1c, and insulin requirements were measured before and for 12 months after the diagnosis and treatment of coeliac disease. Dietary awareness and adherence were assessed by structured questionnaire.

RESULTS

A gluten-free diet resulted in a significant increase in weight-for-age z scores at 12 months after diagnosis (mean increase in z score 0.33) and in BMI (mean increase in z score 0.32). Increases in height did not achieve statistical significance. Controls showed no significant changes in weight, height, or BMI over the same period. Insulin dosage at diagnosis was less in coeliacs than in controls (mean difference 0.16 units/kg/day), but was similar to controls once a gluten-free diet had been established. Questionnaires were obtained in 20 patients. There appeared to be a relation between dietary awareness/adherence and growth parameters, but the small number of patients with "poor/fair" dietary adherence prevented meaningful analysis of this group.

CONCLUSION

Identification and dietary treatment of coeliac disease in children with diabetes improved growth and influenced diabetic control. Evaluation of the outcome of treatment of coeliac disease in diabetics should include assessments of gluten intake.

Ranitidine-enhanced 99mtechnetium pertechnetate imaging in children improves the sensitivity of identifying heterotopic gastric mucosa in Meckel's diverticulum

Meckel's diverticulum is the most common congenital gastrointestinal anomaly. (99m )Technetium pertechnetate imaging (Meckel's scan) is the best noninvasive method used to diagnose this condition when heterotopic gastric mucosa (HGM) is present. Although cimetidine enhancement has been shown to improve sensitivity of the Meckel's scan, ranitidine enhancement has also been advocated; however, this recommendation is based on unpublished data. Thirty-seven children with confirmed Meckel's diverticulum were reviewed retrospectively. Of eight children with HGM in the Meckel's diverticulum who presented with profuse rectal bleeding and underwent the conventional Meckel's scan, three of them (37.5%) had a false negative study. Ranitidine, when administered either intravenously or orally for 24 h prior to the Meckel's scan, enhanced the sensitivity of this test to 87.5% in our patient cohort.

Carbohydrate-deficient glycoprotein syndrome 1b: a new answer to an old diagnostic dilemma

A patient with carbohydrate-deficient glycoprotein syndrome type 1b (CDGS1b) is reported. The patient presented at 5 months of age with failure to thrive, prolonged diarrhoea, hepatomegaly and elevated serum liver transaminases. Liver biopsy showed steatosis. A low serum albumin and elevated serum liver transaminases persisted throughout childhood during which he had repeated infectious illnesses. From the age of 10 years he had oesophageal and duodenal ulceration together with recurrent bacterial cholangitis. Liver biopsy demonstrated hepatic fibrosis. CDGS1b was suspected, supported by the finding of a protein-losing enteropathy and finally confirmed by showing a reduced phosphomannoseisomerase activity. This case illustrates a rare condition with a wide range of presentations.

Delayed presentation of an ingested foreign body causing gastric perforation

Ingested foreign bodies may lead to perforation of the gastrointestinal tract. We present a case of a 14-month-old boy who presented with an unusual abdominal mass secondary to ingesting a foreign body 4 months previously. Abdominal computerized tomography scan was valuable in making this diagnosis.

Gastrointestinal transit and anorectal manometry in children with colonic substance P deficiency

BACKGROUND AND AIMS

Severe intractable constipation in children may be associated with a reduction of substance P (SP)- containing fibers in colonic circular muscle. The aim of this study was to characterize gastrointestinal transit (GIT), anorectal manometry (ARM) and electromyographic (EMG) changes in these children.

METHODS

Seromuscular laparoscopic biopsies of the colon were obtained from 35 children with severe constipation. Immunofluorescent staining for SP and vasoactive intestinal peptide (VIP) were then performed on these specimens. The cohort of patients studied included a SP-deficient group (SPD, n = 25) who had reduced numbers of SP-immunoreactive nerve fibers. The other group consisted of patients with normal staining for both SP and VIP (SPN, n = 10). Gastrointestinal transit studies (gastric emptying, orocecal and colonic transit) suitable for analysis were available for 17 patients (SPD, n = 9 and SPN, n = 8). The colon was divided into segments and radioactivity counts in each segment were expressed as a percentage of the total colonic count at each time point (6, 24, 32 and 48 h). The geometric center (GC), ARM, EMG, clinical and demographic data characteristics of both groups of patients were compared.

RESULTS

There were no differences in demographic data, gastric emptying, orocecal transit or geometric center of transit in the colon between the two patient groups. The ARM and EMG studies suggested that the SPN group have a higher mean threshold volume of balloon distension required to initiate a rectoanal inhibitory reflex, and a higher incidence of anismus; however, this did not reach statistical significance.

CONCLUSIONS

These data suggest a trend that the SPN patients have a greater problem with obstructive defecation and abnormal rectal sensation than those with SPD. We were unable to confirm any defect in colonic transit in the SPD patients compared with the SPN group.

Ataxia with isolated vitamin E deficiency: a clinical, biochemical and genetic diagnosis

A case of ataxia with isolated vitamin E deficiency, in conjunction with supportive genetic studies, is reported. This is a neurodegenerative condition that involves a mutation in the tocopherol (alpha) transfer protein gene (TTPA). Measurement of serum vitamin E concentration should be included as part of the investigations in children with progressive ataxia, even in the absence of fat malabsorption. Early treatment with vitamin E may protect such patients against further neurological damage.

Elevated aminotransferase as a presenting finding in a patient with occult muscle disease

We report a patient with occult muscle disease who presented with raised serum aminotransaminases. This case report emphasises the importance of considering muscle disease in the differential diagnosis of raised serum aminotransaminases, as it may negate the need for invasive investigations such as liver biopsy.

Case report: Colonic duplication: a rare cause of obstruction

Complete duplication of the entire large bowel with partial ileal involvement is very rare and diagnosis can often be difficult as illustrated by this case report. We also review the other clinical associations of this rare condition and briefly discuss the embryology of duplications of the gastrointestinal tract.

An unusual cause of rectal bleeding in a patient with cystic fibrosis

Here we identify a previously unreported cause of rectal bleeding (juvenile polyposis) in a patient with cystic fibrosis (CF). We believe this patient most likely has two coexisting genetic diseases. It also raises many issues about organ transplantation in a patient with medical conditions that individually increase the risk of gastrointestinal malignancy and stresses the diagnostic value of endoscopy in CF patients with rectal bleeding.

Colonic and jejunal motor disturbances after colonic antigen challenge of sensitized rat

BACKGROUND & AIMS

Inflammation in the colon may alter motility in the proximal gut and potentiate clinical symptoms. The aim of this study was to characterize the effect of colonic anaphylaxis on local (colonic) and remote (small intestinal) motility and identify the mechanism and mediators involved.

METHODS

Rats were sensitized by intraperitoneal injection of 10 microg egg albumin and surgically prepared with electrodes in jejunum and colon and a colostomy tube. Colonic and jejunal myoelectric activity were recorded in fasted animals before and after colonic antigen challenge without and then after pretreatment with specific antagonists.

RESULTS

Colonic antigen challenge of sensitized rats was associated with significant (1) increase in colonic myoelectric spike activity, (2) disruption of fasting jejunal motility and initiation of aborally propagating spike complexes, and (3) increase in plasma rat mast cell protease II levels with a decrease in granulated mast cells in colon but not jejunum. The myoelectric disturbance in both colon and jejunum was inhibited significantly by pretreatment with atropine and hexamethonium, doxantrazole, cyclooxygenase, and lipoxygenase inhibitors. Methysergide inhibited only the jejunal disturbance.

CONCLUSIONS

Colonic antigen challenge of sensitized animals results in local mast cell activation and the release of mediators that modulate neural pathways to initiate both a local colonic and a remote jejunal myoelectric disturbance.

Intestinal anaphylaxis induces Fos immunoreactivity in myenteric plexus of rat small intestine

Fos immunohistochemistry was used to identify myenteric neurons activated as a consequence of intestinal anaphylaxis in Hooded-Lister rats sensitized to egg albumin (EA 10 micrograms ip). After incubation in test solutions, or after in vivo challenge, jejunal tissues were processed for immunohistochemistry with an anti-Fos antibody (1:500, TF161). The neuronal identity of the Fos-labeled nuclei was confirmed by double labeling with neuron-specific enclose (1:1,000). In in vitro studies, exposure of control tissue to 50 mM K(+)-Krebs-EA (2 x 10(-5) M) solutions significantly increased Fos immunoreactivity in the myenteric plexus, whereas a basal level of Fos was seen in control tissue incubated in Krebs solution, sham-sensitized tissue exposed to bovine serum albumin (BSA, 2 x 10(-5) M), or EA and sensitized tissue exposed to BSA. Pretreatment of sensitized tissue with doxantrazole (10(-4) M) markedly reduced Fos immunoreactivity observed after EA exposure. In in vivo studies, there was negligible Fos immunoreactivity in the myenteric plexus of control, sham-sensitized, or sensitized rats challenged with saline. A low level of Fos was seen in neurons of sham-sensitized rats challenged with BSA or EA and in sensitized rats challenged with BSA. Significantly greater levels of Fos were observed in the myenteric plexus of sensitized animals challenged with EA, even after pretreatment with capsaicin (125 mg/kg). These results suggest a role for myenteric neurons in intestinal anaphylaxis. In sensitized rats, activation of myenteric neurons is dependent on antigen-induced mast cell activation and occurs independently of capsaicin-sensitive afferent nerves.

Colonic motor response to IgE-mediated mast cell degranulation in the Hooded-Lister rat

After challenge of sensitized individuals, food protein-induced colonic anaphylaxis may contribute to the symptom of diarrhoea. The aim of this study was to characterize the effect of food protein-induced anaphylaxis on colonic circular muscle in vitro, identify the mediators involved, and then evaluate the effect of antigen challenge on colonic transit in vivo. Hooded-Lister rats were sensitized by intraperitoneal injection of egg albumin and controls were sham-sensitized with saline. Rings of distal colonic tissue were suspended in standard tissue baths (mucosa intact) and circular muscle contractility was measured in response to antigen or other agents on day 14. In conscious animals, Na2(51)CrO4 was instilled alone, or with antigen, via proximal colostomy and the geometric centre of distribution of51Cr calculated. Following antigen challenge, a contractile response occurred only in animals that were sensitized (specific IgE antibody levels > or = 1:64), and was specific for the sensitizing antigen. Mast cell involvement was suggested when (1) concanavalin A (a degranulator of both mucosal and connective tissue mast cells) mimicked the antigen-induced response, and (2) Ag-induced contraction was significantly inhibited by mast cell stabilizers. The Ag-induced response was significantly and independently inhibited by a lipo-oxygenase enzyme inhibitor and by LTD4 and platelet activating factor receptor antagonists. The antigen-induced response was resistant to histamine and 5-hydroxytryptamine receptor antagonists, indomethacin, atropine and tetrodotoxin. The geometric centre of distribution of 51Cr was significantly more distal in sensitized animals challenged with antigen rather than placebo, and only sensitized animals challenged with antigen developed diarrhoea. These results suggest that colonic antigen challenge of sensitized rats is associated with IgE-mediated mast cell activation, the release of membrane derived mediators which, in vitro, act directly on smooth muscle to induce contraction, and in vivo result in an increased rate of aboral transit and diarrhoea.

Hepatic mucormycosis in a bone marrow transplant recipient who ingested naturopathic medicine

This case report describes a bone marrow transplant recipient in whom hepatic zygomycosis developed after ingestion of multiple naturopathic medicines. Mucor was isolated from the patient's liver aspirate and from one of the naturopathic medicines. Arbitrary-primed polymerase chain reaction (PCR) analyses were performed on the Mucor isolates from the patient's liver aspirate and from his naturopathic medicine to see if they were genotypically related. Mucor indicus was the species identified in both the patient's liver aspirate and the naturopathic medicine. Arbitrary-primed PCR analysis revealed that these isolates were genotypically identical. We conclude that this bone marrow transplant recipient acquired hepatic mucormycosis from ingestion of a naturopathic medicine containing Mucor.

Intestinal anaphylaxis: mediation of the response of colonic longitudinal muscle in rat

Colonic smooth muscle function may be altered in food protein hypersensitivity reactions and could contribute to the clinical manifestation of diarrhea. To characterize such functional changes and elucidate the mediators and mechanisms involved. Hooded-Lister rats were sensitized by intraperitoneal injection of egg albumin (10 micrograms), and controls were sham sensitized with saline. Fourteen days later the contractility of longitudinally oriented distal colonic segments (mucosa intact) were studied in standard tissue baths in response to antigen (Ag) or other agents. After Ag exposure, a contractile response was documented in animals that were sensitized [specific immunoglobulin E (IgE) antibody levels > or = 1:64] and was specific for the sensitizing Ag. Mast cell involvement was suggested by a significant reduction in the number of granulated mucosal mast cells in sensitized tissues after Ag challenge and in the magnitude of the Ag-induced contractile response in the presence of mast cell stabilizers. The antigen-induced response was significantly and independently inhibited by both cyclooxygenase and lipoxygenase enzyme inhibitors and by leukotriene D4 and platelet activating factor receptor antagonists. The Ag-induced response was resistant to histamine and the 5-hydroxytryptamine antagonists, atropine and tetrodotoxin. These results suggest that the food protein-induced contraction of colonic longitudinal smooth muscle in the sensitized rat is due to IgE-mediated mast cell activation with the subsequent production and release of membrane-derived mediators that, in vitro, act directly on the smooth muscle.

IgM secreted by human T lymphoma virus-I-infected and transformed human B cell clones recognize a 66-kilodalton host-encoded protein

It has previously been determined that transformed human B cells may be infected by and retain integrated human T cell lymphotropic virus, type I (HTLV-I). Although HTLV-I is primarily associated with transformation of human T lymphocytes, immortalized B cell populations have arisen after cocultivation of normal B cells and irradiated HTLV-I-infected T cells. To test whether HTLV-I infection might be involved in this B cell transformation process, we characterized five independent HTLV-I-infected and -immortalized human B cell clones. All five clones contained clonal HTLV-I integrations, expressed cell surface IgM, and secreted IgM in quantities varying from 0.1 to 4.0 micrograms/ml. Immunoblotting and immunoprecipitation of metabolically labeled cell lysates failed to detect synthesis of HTLV-I gag, env, or tat gene products, and cellular RNA dot blot analysis detected varying levels of HTLV-I gene transcripts in only three of the five clones. The secreted IgM from culture supernatants were affinity purified, and were found to selectively immunoprecipitate an acidic protein (isoelectric point = 5.0) of 66,000 m.w. (p66) from purified radioiodinated HTLV-I virions. This p66 copurified with metabolically labelled HTLV-I-infected B cell IgM from HKA-3 cells. Although HTLV-I RNA transcripts were present at low levels, the absence of HTLV-I proteins in HKA-3 cells made it unlikely that p66 was related to the major HTLV-I envelope glycoprotein, gp62. Anti-idiotypic mAb directed against the IgM produced by one B cell clone (HKA-3), as well as purified HTLV-I virions (containing p66), stimulated HKA-3 cell proliferation. Preincubating the anti-Id antibody or HTLV-I with excess HKA-3 IgM abolished the binding of either to HKA-3 cells. These data suggest that HTLV-I infected cells produce a cellular protein (p66), which is incorporated into and copurifies with HTLV-I virions, and which in at least one case (HKA-3) may act as a mitogenic stimulus, potentially contributing to the HTLV-I mediated transformation process.

IgM secreted by human T lymphoma virus-I-infected and transformed human B cell clones recognize a 66-kilodalton host-encoded protein

It has previously been determined that transformed human B cells may be infected by and retain integrated human T cell lymphotropic virus, type I (HTLV-I). Although HTLV-I is primarily associated with transformation of human T lymphocytes, immortalized B cell populations have arisen after cocultivation of normal B cells and irradiated HTLV-I-infected T cells. To test whether HTLV-I infection might be involved in this B cell transformation process, we characterized five independent HTLV-I-infected and -immortalized human B cell clones. All five clones contained clonal HTLV-I integrations, expressed cell surface IgM, and secreted IgM in quantities varying from 0.1 to 4.0 micrograms/ml. Immunoblotting and immunoprecipitation of metabolically labeled cell lysates failed to detect synthesis of HTLV-I gag, env, or tat gene products, and cellular RNA dot blot analysis detected varying levels of HTLV-I gene transcripts in only three of the five clones. The secreted IgM from culture supernatants were affinity purified, and were found to selectively immunoprecipitate an acidic protein (isoelectric point = 5.0) of 66,000 m.w. (p66) from purified radioiodinated HTLV-I virions. This p66 copurified with metabolically labelled HTLV-I-infected B cell IgM from HKA-3 cells. Although HTLV-I RNA transcripts were present at low levels, the absence of HTLV-I proteins in HKA-3 cells made it unlikely that p66 was related to the major HTLV-I envelope glycoprotein, gp62. Anti-idiotypic mAb directed against the IgM produced by one B cell clone (HKA-3), as well as purified HTLV-I virions (containing p66), stimulated HKA-3 cell proliferation. Preincubating the anti-Id antibody or HTLV-I with excess HKA-3 IgM abolished the binding of either to HKA-3 cells. These data suggest that HTLV-I infected cells produce a cellular protein (p66), which is incorporated into and copurifies with HTLV-I virions, and which in at least one case (HKA-3) may act as a mitogenic stimulus, potentially contributing to the HTLV-I mediated transformation process.

Ventilatory response to increased dead spaces in the first week of life

We have developed a method for quantitatively assessing respiratory control in a group of 10 full-term healthy babies, mean age at test 5 days, by measuring their ventilatory response to added external dead spaces. The dead spaces were equal to 0.5, 1, 2, and 3 anatomic dead spaces (2.2 ml/kg body weight), respectively. Tidal volumes were measured by a nasal mask and a 200-I rigid container. End-tidal CO2 was monitored via a tube in the nostril by a mass spectrometer. Baseline measurements were made during a 10-minute period, after which similar recordings were obtained with each of the dead space tubes. The system was calibrated against a 20-ml syringe. The mean baseline ventilation was 602 ml/minute. On the addition of 0.5, 1, 2, and 3 dead spaces, minute ventilations were increased by 37.5, 74.7, 150.7, and 273.6%, respectively. These increases were due to rises in tidal volume rather than respiratory rate. End-tidal CO2 rose by 1.8 and 4 mmHg on the addition of 2 and 3 dead spaces. When the results were compared with expected minute ventilations--based on the baseline recordings and corrected for the added dead spaces and for changes in anatomic dead space ventilation due to alterations in respiratory rate--the results were within 10% of expected values.