Low level expression of human papillomavirus type 16 (HPV16) E6 in squamous epithelium does not elicit E6 specific B- or T-helper immunological responses, or influence the outcome of immunisation with E6 protein

Mice transgenic for E6/E7 oncogenes of Human Papillomavirus type 16 display life-long expression of E6 in lens and skin epithelium, and develop inflammatory skin disease late in life, which progresses to papillomata and squamous carcinoma in some mice. We asked whether endogenous expression of E6 induced a specific immunological outcome, i.e. immunity or tolerance, or whether the mice remained immunologically naïve to E6. We show that prior to the onset of skin disease, E6 transgenic mice did not develop a spontaneous E6-directed antibody response, nor did they display T-cell proliferative responses to dominant T-helper epitope peptides within E6. In contrast, old mice in which skin disease had arisen, developed antibodies to E6. We also show that following immunisation with E6, specific antibody responses did not differ significantly among groups of E6-transgenic mice of different ages (and therefore of different durations and amounts of exposure to endogenous E6), and non-transgenic controls. Additionally, E6 immunisation-induced T-cell proliferative responses were similar in E6-transgenic and non-transgenic mice. These data are consistent with the interpretation that unimmunised E6-transgenic mice that have not developed inflammatory skin disease remain immunologically naïve to E6 at the B- and Th levels. There are implications for E6-mediated tumorigenesis in humans, and for the development of putative E6 therapeutic vaccines.

Acetylation of HIV-1 Tat by CBP/P300 increases transcription of integrated HIV-1 genome and enhances binding to core histones

The HIV-1 Tat protein is required for viral replication and is a potent stimulator of viral transcription. Although Tat has been extensively studied in various reductive paradigms, to date there is little information as to how this activator mediates transcription from natural nucleosomally packaged long terminal repeats. Here we show that CREB-binding protein (CBP)/p300 interacts with the HIV-1 Tat protein and serves as a coactivator of Tat-dependent HIV-1 gene expression on an integrated HIV-1 provirus. The site of acetylation of Tat was mapped to the double-lysine motif in a highly conserved region, (49)RKKRRQ(54), of the basic RNA-binding motif of Tat. Using HLM1 cells (HIV-1(+)/Tat(-)), which contain a single copy of full-length HIV-1 provirus with a triple termination codon at the first AUG of the Tat gene, we find that only wild type, and not K50A, K51A, or K50A/K51A alone or in combination of ectopic CBP/p300, is able to produce full-length infectious virions, as measured by p24 gag ELISAs. Tat binds CBP/p300 in the minimal histone acetyltransferase domain (1253-1710) and the binding is stable up to 0.85 M salt wash conditions. Interestingly, wild-type peptide 41-54, and not other Tat peptides, changes the conformation of the CBP/p300 such that it can acquire and bind better to basal factors such as TBP and TFIIB, indicating that Tat may influence the transcription machinery by helping CBP/p300 to recruit new partners into the transcription machinery. Finally, using biotinylated wild-type or acetylated peptides, we find that acetylation decreases Tat's ability to bind the TAR RNA element, as well as to bind basal factors such as TBP, CBP, Core-Pol II, or cyclin T. However, the acetylated Tat peptide is able to bind to core histones on a nucleosome assembled HIV-1 proviral DNA.

[Long-term influence of associated arthrodesis on adjacent segments in the treatment of lumbar stenosis: a series of 127 cases with 9-year follow-up]

PURPOSE OF THE STUDY

Little is known about the impact of posterolateral arthrodesis on adjacent levels. In order to examine this question, we analyzed the radiological evolution of the lumbar spine in patients treated for lumbar stenosis, comparing cases where posterolateral arthrodesis was used with the other cases. Our aim was to determine whether the long-term radiographical modifications were affected by the arthrodesis.

MATERIAL AND METHODS

Among our series of patients presenting with lumbar stenosis between 1984 and 1992, we retained two groups: patients in group 1 (n=46) who underwent single-level decompressions at L4-L5 or L4-L5 and L5-S1 level; and patients in group II (n=81) who underwent decompressions on the same levels associated with posterolateral arthrodesis extending from L4 to the sacrum with or without instrumentation. We compared the course of the two levels above the decompression (L2-L3 and L3-L4) between the two groups. We compared three radiological parameters: disc height, intervertebral slipping, and intersegmental mobility. We also examined the correlations between radiological modifications and functional outcome. Mean follow-up for these 127 patients was 9 years.

RESULTS

The two groups were comparable for age, gender, follow-up, and presurgical functional score, disc height and intervertebral slipping at equivalent levels. At last follow-up, disc narrowing was observed at L2-L3 and L3-L4; it was significantly greater in the group with complementary arthrodesis. At L3-L4, intervertebral slipping also worsened more in the arthrodesis patients. Use of osteosynthesis significantly increased the risk of developing such radiological lesions. These lesions were associated, solely in the arthrodesis group, with poorer functional outcome.

CONCLUSION

Our findings allow the conclusion that, despite the effect of physiological aging, the observed long-term degenerative lesions in patients undergoing treatment of lumbar stenosis are related to the associated arthrodesis which increases their frequency and severity, deteriorating the functional outcome.

Significance of minimal or no intraperitoneal fluid visible on CT scan associated with blunt liver and splenic injuries: a multicenter analysis

BACKGROUND

The use of ultrasound (U/S) for the evaluation of patients with blunt abdominal trauma is gaining increasing acceptance. Patients who would have undergone computed tomographic (CT) scan may now be evaluated solely with U/S. Solid organ injuries with minimal or no free fluid may be missed by surgeon sonographers.

OBJECTIVE

The purpose of this study was to describe the incidence and clinical importance of liver and splenic injuries with minimal or no free intraperitoneal fluid visible on CT scan. We hypothesized that these solid organ injuries occur infrequently and are of minor clinical significance.

METHODS

Patient records and CT scans were reviewed for the presence of and outcome associated with blunt liver and splenic injuries with minimal (<250 mL) or no free fluid detected by an attending radiologist. Data were collected from six major trauma centers during a 4-year period before the introduction of U/S and included demographics, grade of injury (American Association for the Surgery of Trauma scale), need for operative intervention, and outcome.

RESULTS

A total of 938 patients with liver and splenic injuries were identified. In this group, 11% of liver injuries and 12% of splenic injuries had no free fluid visible on CT scan and could be missed by diagnostic peritoneal lavage or U/S. Of the 938 patients, 267 (28%) met the inclusion criteria; 161 had injury to the spleen and 125 had injury to the liver. In the 267 patients studied, 97% of the injuries were managed nonoperatively. However, 8 patients (3%) required operative intervention for bleeding. Compared with the liver, the spleen was significantly more likely to bleed (p = 0.01), but the grade of splenic injury was not related to the risk for hemorrhage (p = 0.051).

CONCLUSION

Data from this study suggest that injuries to the liver or spleen with minimal or no intraperitoneal fluid visible on CT scan occur more frequently than predicted but usually are of minimal clinical significance. However, patients with splenic injuries may be missed by abdominal U/S. We found a 5% associated risk of bleeding. Therefore, abdominal U/S should not be used as the sole diagnostic modality in all stable patients at risk for blunt abdominal injury.

Osmotic behavior of in vitro produced bovine blastocysts in cryoprotectant solutions as a potential predictive test of survival

The osmotic behavior of bovine blastocysts produced in vitro was filmed during exposure to and dilution of cryoprotectant solutions used for vitrification. The relationship between the changes in the diameter of embryos and their subsequent survival was assessed. Embryos collected on Day 6 and Day 7 postinsemination were exposed to 10% glycerol (GLY) for 5 min, 10% GLY + 20% ethylene glycol (EG) for 5 min, and 25% Gly + 25% EG for 30 s, before dilution in 0.85 M galactose and finally in embryo transfer freezing medium (ETF). Embryos that had a higher probability of survival behaved as perfect osmometers, shrinking, reexpanding, or swelling according to an identical pattern, whereas embryos that deviated from this standard usually did not survive. The initial embryo diameter, duration of shrinkage and expansion in 10% glycerol, duration of reexpansion in ETF, and final embryo diameter were clearly predictive of the ability to hatch after culture in vitro. On a given day postinsemination, larger blastocysts were more likely than smaller blastocysts to survive and hatch after exposure to cryoprotectants with or without vitrification.

18F-labeled FECNT: a selective radioligand for PET imaging of brain dopamine transporters

Fluorine-18 labeled 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nort ropane (FECNT) was synthesized in the development of a dopamine transporter (DAT) imaging ligand for positron emission tomography (PET). The methods of radiolabeling and ligand synthesis of FECNT, and the results of the in vitro characterization and in vivo tissue distribution in rats and in vivo PET imaging in rhesus monkeys of [18F]FECNT are described. Fluorine-18 was introduced into 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nort ropane (4) by preparation of 1-[18F]fluoro-2-tosyloxyethane (2) followed by alkylation of 2beta-carbomethoxy-3beta-(4-chlorophenyl)nortropane (3) in 21% radiochemical yield (decay corrected to end of bombardment [EOB]). Competition binding in cells stably expressing the transfected human DAT serotonin transporter (SERT) and norepinephrine transporter (NET) labeled by [3H]WIN 35428, [3H]citalopram, and [3H]nisoxetine, respectively, indicated the following order of DAT affinity: GBR 12909 > CIT >> 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(3-fluoropropyl) nortropane (FPCT) > FECNT. The affinity of FECNT for SERT and NET was 25- and 156-fold lower, respectively, than for DAT. Blocking studies were performed in rats with a series of transporter-specific agents and demonstrated that the brain uptake of [18F]FECNT was selective and specific for DAT-rich regions. PET brain imaging studies in monkeys demonstrated high [18F]FECNT uptake in the caudate and putamen that resulted in caudate-to-cerebellum and putamen-to-cerebellum ratios of 10.5 at 60 min. [18F]FECNT uptake in the caudate/putamen peaked in less than 75 min and exhibited higher caudate- and putamen-to-cerebellum ratios at transient equilibrium than reported for 11C-WIN 35,428, [11C]CIT/RTI-55, or [18F]beta-CIT-FP. Analysis of monkey arterial plasma samples using high performance liquid chromatography determined that there was no detectable formation of lipophilic radiolabeled metabolites capable of entering the brain. In equilibrium displacement experiments with CIT in rhesus monkeys, radioactivity in the putamen was displaced with an average half-time of 10.2 min. These results indicate that [18F]FECNT is a radioligand that is superior to 11C-WIN 35,428, [11C]CIT/RTI-55, [18F]beta-CIT-FP, and [18F]FPCT for mapping brain DAT in humans using PET.

IS1397 is active for transposition into the chromosome of Escherichia coli K-12 and inserts specifically into palindromic units of bacterial interspersed mosaic elements

We demonstrate that IS1397, a putative mobile genetic element discovered in natural isolates of Escherichia coli, is active for transposition into the chromosome of E. coli K-12 and inserts specifically into palindromic units, also called repetitive extragenic palindromes, the basic element of bacterial interspersed mosaic elements (BIMEs), which are found in intergenic regions of enterobacteria closely related to E. coli and Salmonella. We could not detect transposition onto a plasmid carrying BIMEs. This unprecedented specificity of insertion into a well-characterized chromosomal intergenic repeated element and its evolutionary implications are discussed.

Beta-lactam-dependent coagulase-negative staphylococcus associated with urinary-tract infection

Beta-lactam-dependent Staphylococcus saprophyticus was isolated from midstream urine from a patient treated with repeated courses of amoxycillin for recurrent urinary-tract infection.

Cannabinoid ligands and their effects on learning and performance in rhesus monkeys

To characterize the role of CB1 receptors in mediating the acquisition of new behavior or learning, delta 9-THC (delta 9-tetrahydrocannabinol), WIN 55,212-2 (R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpho-linyl)methyl]pyrol - (1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl)methanone monomethanesulfonate), SR141716A (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlor- phenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride) and cannabidiol were administered to monkeys responding under a multiple schedule of repeated acquisition and performance of conditional discriminations. SR141716A, a putative antagonist at CB1 receptors, was also administered in combination with delta 9-THC. In one component of the multiple schedule, subjects acquired a different complex discrimination each session (acquisition component), whereas in the other component the discrimination remained the same each session (performance component). Correct responding in each component was maintained by food presentation under a variable-ratio (VR) schedule, whereas incorrect responding (errors) produced a time-out. Administered prior to the start of the session, delta 9-THC and WIN 55,212-2 dose-dependently decreased overall response rate in both the acquisition and performance components. Both drugs also selectively increased the percentage errors in the acquisition component, but only at higher doses. SR141716A and cannabidiol also dose-dependently decreased overall response rate in both schedule components, but neither drug increased the percentage of errors. Decreases in response rate were also observed 24 hours after administration of SR141716A at doses greater than 1 mg/kg. When lower doses of SR141716A (0.1-1 mg/kg) were administered in combination with delta 9-THC, there was a dose-dependent antagonism of the rate-decreasing and error-increasing effects of delta 9-THC (i.e. the dose-effect curves for delta 9-THC-induced disruptions in responding were shifted rightward). In summary, CB1-receptor agonists such as delta 9-THC and WIN 55,212-2 were more disruptive to the rate and accuracy of learning in old-world monkeys than the CB1-receptor antagonist SR141716A or cannabidiol.

Human papillomavirus type 16 E7 oncoprotein expressed in peripheral epithelium tolerizes E7-directed cytotoxic T-lymphocyte precursors restricted through human (and mouse) major histocompatibility complex class I alleles

Mice which coexpress human papillomavirus type 16 E7 and HLA A2.1 in peripheral squamous epithelium and thymic cortical epithelium are tolerant at the cytotoxic T-lymphocyte (CTL) level to E7 epitopes restricted through HLA A*0201 and H-2(b) (T. Doan, M. Chambers, M. Street, G. J. Fernando, K. Herd, P. Lambert, and R. Tindle, Virology 244:352-364, 1998). Here we used bone marrow-reconstituted radiation chimeras to distinguish whether E7-directed CTL tolerance was mediated peripherally by E7 expression in skin or centrally by E7 expression in thymus. In chimeric mice expressing E7 in skin and reconstituted with E7-naïve bone marrow and E7-naïve thymus, CTL responses to vaccine-administered E7 epitopes were not restored, i.e. , the mice remained tolerant. In contrast, chimeric mice not expressing E7 in skin and reconstituted with E7-naïve bone marrow and E7-expressing thymus had full E7-directed CTL responses. These results demonstrate that E7 protein expression in peripheral squamous epithelium is sufficient to tolerize the E7-directed CTL precursor repertoire. The data have implications for E7-mediated tumorigenesis and for the development of E7-based immunotherapeutic strategies, since peripheral immunological tolerance of tumor-associated antigens may create a barrier to effective immunotherapy.

Alveolar clearance in horses with chronic obstructive pulmonary disease

OBJECTIVE

To assess sensitivity of scintigraphic alveolar clearance rate as an indicator of alveolar epithelium damage in horses.

ANIMALS

5 healthy horses (group A) and 5 with chronic obstructive pulmonary disease (COPD; group B).

PROCEDURE

Horses underwent clearance rate (k [%/min]) determination. Clearance rate of group-B horses was determined after remission of the disease following 2 months at pasture (remission 1), stabling in a controlled environment (remission 2), and during crisis induced by exposure to moldy hay and straw. Methacholine challenge test was performed at each investigation period to determine nonspecific pulmonary airway hyperresponsiveness. Pulmonary function tests (PFT) also were performed, and cell populations in bronchoalveolar lavage (BAL) fluid were determined on another occasion.

RESULTS

Group-B horses had significantly faster mean clearance rate during crisis (k = 4.30+/-0.95%/min), compared with that for remission 1(k = 1.98+/-0.55%/min), which did not differ from the rate in group-A horses (k = 1.95+/-0.33%/min). Despite lack of clinical signs of COPD during remission when stabled in a controlled environment, an intermediate value was found (k = 3.20+/-0.72%/min).

CONCLUSIONS

This technique allowed grading of lung damage induced by COPD, whereas use of PFT and determination of BAL fluid cell populations failed to differentiate between remission 1 and remission 2.

CLINICAL RELEVANCE

Determination of alveolar clearance rate by use of scintigraphy is a sensitive indicator of lung damage. A modified clearance rate was found despite the lack of clinical and functional changes.

RTI-113 administration reduces cocaine self-administration at high occupancy of dopamine transporter

RTI-113 [3beta-(4-chlorophenyl)tropan-2beta carboxylic acid phenyl ester hydrochloride], one of many phenyltropanes potent at and selective for DAT, inhibited self-administration of cocaine in rat at doses that did not alter responding maintained by food. The doses that inhibited cocaine intake produced significant levels of occupancy of DAT.

Scintigraphical evaluation of alveolar clearance in horses

This study proposed a standardized method for measuring alveolar epithelium membrane permeability in the horse. The normal rate of clearance (%.min-1) from lung into blood of nebulized 99mTc-DTPA has been established for healthy horses (Group A) compared with values obtained with horses suffering from chronic obstructive pulmonary disease (COPD; Group B). The 99mTc-DTPA clearance was measured in the caudoventral (R1) and in the half caudal (R2) parts of the left lung during different time intervals. The two regions aimed to define the influence of the airways on measured clearance (R2 contained proportionally more conducting airways than R1). It was concluded that a comparison of groups of subjects may be performed in R2 and on data collected during a 20 min period. The normal clearance rate in R2 was 1.80 +/- 0.46%.min-1 (T1/2R2 = 40.99 +/- 12.45 min) in Group A. In Group B, a significantly faster 99mTc-DTPA transfer rate was found (4.17 +/- 0.83%.min-1 or T1/2R2 = 17.17 +/- 3.38min). Bronchoalveolar lavage (BAL) suggested that the increased permeability measured in Group B could be the result of lung inflammatory responses. Our results have demonstrated the ability of the 99mTc-DTPA clearance test to detect alveolar epithelial damage in horses. Furthermore, we were able to show that a regional analysis of the alveolar-capillary barrier integrity may be performed satisfactorily in the equine patient.

[Long-term outcome at adjacent levels of lumbar arthrodesis]

Posterolateral lumbar fusion is commonly recognized to have a significant effect upon the more proximal unfused segments. Wether these effects are clinically significant remains unclear. Long term studies with standardized follow-up are scarce. The purpose of this study was to examine the long term roentgenographic and clinical effects of posterolateral fusion upon the 3 cephalad unfused segments. The levels below a floating fusion were also examined. The factors promoting the occurrence of degenerative changes on standard or dynamic x rays were also investigated with a multivariate analysis model. 102 patients who underwent a posterolateral fusion were retrospectively reviewed with an average follow-up of 8.9 years. 39 patients (group I) were fused for low back pain caused by isthmic lysis spondylolisthesis, 15 (group II) for degenerative disc disease and 48 (group III) in addition to a posterior decompression for a lumbar spinal stenosis. Pre and postoperative standard and dynamic roentgenograms were compared in order to study: evolution of the disc space height, modifications in the angular and antero-posterior mobility, modifications in the antero-posterior displacement of the vertebral bodies. Degenerative changes were frequent. 49 per cent of the patients demonstrated a severe disc space narrowing, 30 per cent developed a degenerative spondylolisthesis, 32 per cent an angular hypermobility and 35 per cent an antero-posterior hypermobility. Only one factor was found to increase significantly the occurrence of degenerative changes: the indication of lumbar fusion. Degenerative changes were significantly more frequent in group III's patients. However, no significant correlation was found between the roentgenographic findings and the final functional results and only 8 patients required a new surgery. These results may suggest that posterolateral fusion accelerates the development of degenerative changes in adjacent discs if the fusion is performed on a degenerative spine.

Mice expressing the E7 oncogene of HPV16 in epithelium show central tolerance, and evidence of peripheral anergising tolerance, to E7-encoded cytotoxic T-lymphocyte epitopes

In order to derive mice which expressed both the E7 open reading frame transgene of human papillomavirus type 16 in skin and MHC class 1 restriction elements for several E7-encoded cytotoxic T-lymphocyte (CTL) epitopes, K14.HPV16E7 mice which express E7 in basal keratinocytes were crossed to the F1 generation with A2.1 Kb transgenic mice which express the MHC binding cleft domains of human HLA A*0201, and murine H-2b. F1 mice (denoted K14E7 x A2.1) expressed E7 in the thymus at least as early as 2-5 days before birth. Immunisation of FVB x A2.1 control mice (transgenic for HLA A*0201 and H-2b but not for E7), with two HLA A*0201-restricted epitopes of E7 and one H-2b-restricted CTL epitope of E7, gave strong primary CTL responses recognising epitope-pulsed or constitutively E7-expressing syngeneic target cells. In contrast, in immunised K14E7 x A2.1 mice, the CTL responses to the H-2b epitope and one of the HLA A*0201 CTL epitopes were strongly down-regulated, and to the other HLA A*0201 epitope, completely abolished, as demonstrated by percentage specific killing by bulk splenocyte cultures in cytotoxicity assays, and by CTL precursor frequency analysis. In thymus-transplanted bone marrow radiation chimeras in which the immune system of K14E7 x A2.1 mice was replaced by a FVB x A2.1 immune system, specific immunisation did not result in reemergence of strong E7-directed CTL responses. In agreement with these in vitro findings, specific immunisation failed to significantly alter the course of E7-associated tumour development in K14E7 x A2.1 mice. These data are consistent with a model of central deletional CTL tolerance to E7-encoded epitopes recognised in the context of two distinct MHC class 1 restriction elements, and with the possibility of peripheral T-cell anergy maintained by expression of E7 in the skin.

On the appropriateness of marginal models for repeated measurements in clinical trials

Although models developed directly to describe marginal distributions have become widespread in the analysis of repeated measurements, some of their disadvantages are not well enough known. These include producing profile curves that correspond to no possible individual, possibly showing that a treatment is superior on average when it is poorer for each individual subject, implicitly generating complex and implausible physiological explanations, including underdispersion in subgroups, and sometimes corresponding to no possible probabilistic data generating mechanism. We conclude that such marginal models may sometimes be appropriate for descriptive observational studies, such as sample surveys in epidemiology, but should only be used with great care in causal experimental settings, such as clinical trials.

High level expression of the capsid protein of hepatitis E virus in diverse eukaryotic cells using the Semliki Forest virus replicon

The capsid protein of hepatitis E virus (HEV) is encoded by open reading frame 2 (ORF 2) and exhibits variable processing when expressed in insect and COS cells, but nothing is known of its processing in cells relevant to its replication. The full-length ORF 2 protein was expressed at high levels in mammalian cells by insertion of ORF 2 in the Semliki Forest virus (SFV) replicon to generate rSFV/HEV ORF 2K. Expression of the capsid protein was detected readily by metabolic labelling and indirect immunofluorescence in BHK-21 cells transfected with RNA transcripts derived from rSFV/HEV ORF 2K. ORF 2 protein was also expressed at high levels in cells of diverse origin, including liver-derived cell lines Huh7 and HepG2, following infection with recombinant virus derived from cotransfection of BHK-21 cells with the rSFV/HEV ORF 2K and helper SFV replicon RNAs. The addition of hypertonic KCl during metabolic labelling reduced the level of host cell protein synthesis and enhanced the detection of intermediates in ORF 2 protein processing. The wide host range and high level expression directed by SFV replicon particles has particular utility in the analysis of cell-specific factors in the protein processing and assembly of non-cultivable viruses such as HEV.

Activity of protein MalE (maltose-binding protein) fused to cytoplasmic and periplasmic regions of an Escherichia coli inner membrane protein

We analysed the properties of mature MBP (maltose-binding protein or MalE protein) fused to an integral cytoplasmic membrane protein of Escherichia coli. Fusion of MalE to the first MalG periplasmic loop enabled a strain defective in the malE gene to utilize maltose. In contrast, fusion of MalE to a cytoplasmic loop did not complement the malE delta 444 deletion. We obtained results highly correlated with those obtained by using alkaline phosphatase as a reporter for the topology of MalG. We discuss the possibility of genetically determining the topology of cytoplasmic membrane proteins by a method based on engineered fusions to MBP.

E7 oncoprotein of human papillomavirus type 16 expressed constitutively in the epidermis has no effect on E7-specific B- or Th-repertoires or on the immune response induced or sustained after immunization with E7 protein

A line of FVB (H-2q) mice transgenic for the E6/E7 open reading frames of Human Papillomavirus type 16 driven from the alpha-A crystallin promoter expresses E7 mRNA in lens and skin epithelium. E7 protein is detectable in adult skin, coinciding with the development of inflammatory skin disease, which progresses to papillomata and squamous carcinomata in some mice. By examining the outcome of parenteral immunization with E7 protein, we sought to determine whether endogenous expression of E7 in skin had induced a preexisting immune outcome, i.e., specific immunity or tolerance, or whether the mice remain naive ("ignorant") to E7. Our data show that the antibody response to defined E7 B-epitopes, the proliferative response to Th epitopes, and the delayed-type hypersensitivity (DTH) response to whole E7 did not differ between groups of young and old E6/E7 transgenic mice (likely having different degrees of lifetime exposure to E7 protein) or between E6/E7-transgenic and nontransgenic parental strain control mice. Although an E7-specific CTL response could not be induced in the H-2q background of these mice, incorporation of a Db allele into the genome allowed comparison of Db-restricted CTL responses in E6/E7 transgenic and nontransgenic mice. Experiments indicated that the E7-immunization-induced CTL response did not differ significantly between E6/E7 transgenic and nontransgenic mice. We interpret these results to indicate that in spite of expression of E7 protein in adult skin, E6/E7 transgenic mice remain immunologically naive (ignorant) of E7 epitopes presented by immunization.

Constitutive expression of p50 homodimer in freshly isolated human monocytes decreases with in vitro and in vivo differentiation: a possible mechanism influencing human immunodeficiency virus replication in monocytes and mature macrophages

Human immunodeficiency virus type 1 (HIV-1) replicates more efficiently in vitro in differentiated macrophages than in freshly isolated monocytes. We investigated whether this may be partly explained by changes in expression of NF-kappaB with monocyte differentiation. We demonstrated that constitutive expression of NF-kappaB in primary human monocytes changed significantly with differentiation in vitro to monocyte-derived macrophages (MDMs) and differentiation in vivo to alveolar macrophages (AMs). Freshly isolated monocytes constitutively expressed high levels of transcriptionally inactive p50 homodimer which decreased with time in culture in favor of the transcriptionally active p50/p65 and p50/RelB heterodimers. As in MDMs, AMs constitutively expressed p50/p65 and p50/RelB although at lower levels. HIV infection of fresh monocytes failed to induce p50/p65 as seen in MDMs. The replacement of p50 homodimers with transcriptionally active heterodimers following time in culture may partially explain the progressive increase in susceptibility of monocytes to HIV infection during in vitro culture. The change in NF-kappaB components with monocyte differentiation in vivo may also explain the different transcriptional activities of these cell populations in HIV-infected individuals.