Surface CD4 is critical to in vitro HIV infection of human alveolar macrophages

The CD4 glycoprotein is the major cellular receptor for HIV. CD4 surface expression of monocytes decreases with time in culture while their susceptibility to HIV-1 increases. Our aim was to investigate whether this phenomenon occurs in macrophages that have differentiated in vivo by investigating CD4 expression and HIV-1 infection of human alveolar macrophages (AMs). Using flow cytometry to detect CD4 expression by Leu-3a labeled indirectly with fluorescein isothiocyanate or allophycocyanin, we found that CD4 was expressed at low but detectable levels, despite the high background autofluorescence well described in AMs. This finding was supported by the detection of CD4 mRNA in AMs using RT-PCR. T cell contamination of mRNA extracts of AMs was excluded by amplifying in parallel with primers to the constant region of the T cell receptor. Despite this low level of surface CD4, recombinant soluble CD4 and anti-CD4 antibody completely inhibited HIV-1 infection of AMs. We conclude that CD4, although expressed at low levels on the surface of AMs, appears to be critical to HIV-1 infection of these cells.

Human immunodeficiency virus type 1 replication is blocked prior to reverse transcription and integration in freshly isolated peripheral blood monocytes

Peripheral blood monocytes are resistant to productive human immunodeficiency virus type 1 (HIV-1) infection in vitro immediately after isolation. No viral cDNA (either early or late transcripts) was detected by PCR in monocytes exposed to virus on the day of isolation. In contrast, in monocytes cultured for as little as 1 day, initiated and completed reverse transcripts were readily detectable within 24 h of infection with both HIV-1(Ba-L) and primary isolates. The levels of initiated, partially completed, and completed viral DNA copies found 24 h after infection increased progressively with time in culture before infection. Unlike quiescent T lymphocytes, there appeared to be no block or delay in the integration of viral DNA into the genome of susceptible cultured monocytes. With an Alu-PCR method designed to specifically detect proviral DNA being used, integration events were found within 24 h of infection in monocytes cultured for a day or more after isolation. No integration signal was found in freshly isolated monocytes up to 7 days following exposure to the virus. Cloning and sequencing of Alu-PCR-amplified DNA confirmed integration in HIV-1-infected cultured monocytes. Our finding that in vitro replication of HIV-1 is clearly blocked prior to the initiation of reverse transcription in freshly isolated peripheral blood monocytes suggests that these cells may not be susceptible to infection in vivo. Further studies to clarify this possibility and the nature of the block to infection should provide useful information for treatment strategies against HIV-1.

Sex differences in learning and memory in mice: effects of sequence of testing and cholinergic blockade

Sexual dimorphism in spatial and cued navigation using the Morris water maze was examined in C57BL/6 mice both with and without administration of scopolamine, a cholinergic blocker. In Exp. 1, female and male mice learned to perform first a spatial, then a cued, navigation task. Both performed a spatial task similarly; males, however, performed a cued task better than females. In Exp. 2, the sequence of navigation testing was reversed. Both performed similarly on a cued task; however, males performed a spatial task better than females. In both experiments, females were more sensitive than males to the effects of scopolamine. No significant confounding sex differences were found in either spontaneous activity or passive avoidance retention. These data indicate that sex differences in spatial and cued tasks are dependent on the sequence of task presentation and implicate a role for the cholinergic system in these differences.

Managing HIV. Part 3: Mechanisms of disease. 3.1 Structure and function of HIV

The discovery of HIV in 1983 is a landmark of medical science in the 20th century. HIV is a fragile but stealthy virus that thrives within the cells of the immune system itself, subverting the body's defences against disease. Knowing the structure and life cycle of the virus is the key to understanding how it is transmitted, how it causes disease and how best to prevent or control infection.

Discontinuation of antiepileptic drug treatment after two seizure-free years in children with cerebral palsy

OBJECTIVE

The risk of seizure relapse after antiepileptic drug (AED) discontinuation in children has been reported to vary between 6% and 40%. It has been suggested that neurologic deficit and mental retardation are poor prognostic factors for seizure relapse after AED discontinuation. Because epileptic children with cerebral palsy (CP) have neurologic deficits, and many have mental retardation, it is important to know their risk for seizure relapse.

METHODS

AED treatment was discontinued in 65 children with CP and histories of epilepsy after 2 seizure-free years. All of the patients were followed until they had seizure relapses or for at least 2 years without seizures after AEDs were stopped. Multiple factors were analyzed for possible association with seizure relapse.

RESULTS

Twenty-seven patients (41.5%) had seizure relapses. Patients with spastic hemiparesis had the highest relapse rate (61.5%), and those with spastic diplegia had the lowest rate (14.3%). No other factor correlated significantly with the risk of seizure relapse.

CONCLUSIONS

Discontinuation of AEDs in children with CP can, and should, be practiced when possible after patients have been seizure-free for at least 2 years. AED discontinuation in patients with spastic hemiparesis is significantly more likely to lead to seizure relapse than in patients with other CP types, but no other factor is yet known to increase the chance of relapse.

Recombinant baculovirus-expressed NS3 proteinase of hepatitis C virus shows activity in cell-based and in vitro assays

Recombinant baculoviruses have been constructed which express the hepatitis C virus (HCV) NS3 proteinase and its substrates in insect cells. The expressed proteinase has been shown to carry out trans-cleavage at the NS3/4A, NS4A/4B, NS4B/5A and NS5A/5B junctions in a cell-based assay. When assayed in a cell-free system using in vitro translated substrates, the proteinase could perform trans-processing of the NS4A/4B and NS5A/5B junctions, but only when coexpressed with NS4A, either as an NS3-4A precursor or by co-infection of cells with NS3- and NS4A-expressing recombinant baculoviruses. Possible reasons for the absolute requirement of the NS3 proteinase for NS4A in vitro are discussed.

Client-centred practice: what does it mean and does it make a difference?

During the past 15 years, occupational therapists in Canada, through the Canadian Association of Occupational Therapists, have worked to develop and implement guidelines for practice of a client-centred approach to occupational therapy. One of the difficulties with the current Guidelines for the Client-Centred Practice of Occupational Therapy is the lack of a definition and discussion of the concepts and issues fundamental to client-centred practice. In this paper, key concepts of client-centred practice: individual autonomy and choice, partnership, therapist and client responsibility, enablement, contextual congruence, accessibility and respect for diversity are discussed. Two practice examples are used to illustrate these ideas and raise issues about obstacles to the practice of client-centred occupational therapy. Research evidence about the effectiveness of client-centred concepts in enhancing client satisfaction, functional outcomes and adherence to health service programmes is reviewed.

Genomic structure of an attenuated quasi species of HIV-1 from a blood transfusion donor and recipients

A blood donor infected with human immunodeficiency virus-type 1 (HIV-1) and a cohort of six blood or blood product recipients infected from this donor remain free of HIV-1-related disease with stable and normal CD4 lymphocyte counts 10 to 14 years after infection. HIV-1 sequences from either virus isolates or patient peripheral blood mononuclear cells had similar deletions in the nef gene and in the region of overlap of nef and the U3 region of the long terminal repeat (LTR). Full-length sequencing of one isolate genome and amplification of selected HIV-1 genome regions from other cohort members revealed no other abnormalities of obvious functional significance. These data show that survival after HIV infection can be determined by the HIV genome and support the importance of nef or the U3 region of the LTR in determining the pathogenicity of HIV-1.

Sex differences in learning and memory in mice: effects of sequence of testing and cholinergic blockade

Sexual dimorphism in spatial and cued navigation using the Morris water maze was examined in C57BL/6 mice both with and without administration of scopolamine, a cholinergic blocker. In Exp. 1, female and male mice learned to perform first a spatial, then a cued, navigation task. Both performed a spatial task similarly; males, however, performed a cued task better than females. In Exp. 2, the sequence of navigation testing was reversed. Both performed similarly on a cued task; however, males performed a spatial task better than females. In both experiments, females were more sensitive than males to the effects of scopolamine. No significant confounding sex differences were found in either spontaneous activity or passive avoidance retention. These data indicate that sex differences in spatial and cued tasks are dependent on the sequence of task presentation and implicate a role for the cholinergic system in these differences.

Characterisation of foscarnet-resistant strains of human immunodeficiency virus type 1

Foscarnet is a broad-spectrum viral DNA polymerase inhibitor active in vitro and in vivo against human immunodeficiency virus type 1 (HIV-1). Strains of HIV-1 resistant to foscarnet were selected by in vitro passage in increasing concentrations of drug. Reduced susceptibility to foscarnet was evident at the levels of both HIV-1 replication and reverse transcriptase. Biologically cloned, foscarnet-resistant strains with distinct genotypes were hypersensitive to zidovudine, azidodeoxyuridine, nevirapine, and R82913 but had unchanged susceptibility to zalcitibine and didanosine. The reverse transcriptase of foscarnet-resistant strains had unique substitutions Glu89-Lys, Leu92-Ile, or Ser156-Ala, the third being associated with six polymorphic changes. Introduction of these mutations into wild-type HIV-1 by site-directed mutagenesis confirmed their role in foscarnet resistance. In the three-dimensional structure of the reverse transcriptase enzyme these amino acids are located close to the template strand of the template primer and far away from the putative pyrophosphate binding site, suggesting that the mechanism by which HIV-1 becomes resistant to foscarnet is indirect. Foscarnet resistance is thus likely to be mediated through an altered interaction of the mutant enzyme with the template strand of the template primer which distorts the geometry of the polymerase active site and thereby decreases foscarnet binding.

Maternal smoking, alcohol drinking, caffeine consumption, and fetal growth: results from a prospective study

In a prospective study of 712 pregnancies, we examined associations between maternal smoking, alcohol, and caffeine consumption and fetal growth. We interviewed patients at entry into care [12.9 +/- 4.3 (standard deviation) weeks], and at 28 and 36 weeks of gestation. We found the expected reductions in adjusted birthweight among women who smoked throughout pregnancy: 168 gm [95% confidence limits (CL) = -326, -10] for low/moderate amounts (< or = 15 cigarettes per day); 288 gm (95% CL = -491, -84) for heavy smoking (> 15 cigarettes per day). We also found a decrease in birthweight (-179 gm; 95% CL = -364, 7) among smokers who reported quiting early in pregnancy. First trimester alcohol consumption (average: four drinks per week) was associated with a 155-gm reduction in fetal growth (95% CL = -324, 15), even after adjustment for number of cigarettes smoked. The association, observed with all types of alcohol consumption, was stronger among smokers (-270 gm) but was also present in nonsmokers (-115 gm). Caffeine consumption showed no relation to fetal growth, even among heavy consumers, although they were relatively few. This study implicates heavy maternal smoking at any point in pregnancy, including solely in the early months, and possibly moderate alcohol drinking as causes of low birthweight.

Views of mixed sex wards: a survey of patients, carers and nurses

This paper describes the design and implementation of a survey carried out at Wharfedale General Hospital, related to the potential development of mixed sex wards. The survey of patients, carers and ward nurses, carried out in December 1992, demonstrated a general consensus of views on mixed sex ward options, and identified a number of key areas which need to be addressed before both sexes can be nursed satisfactorily on wards which have historically been used for males or females only. The recommendations arising from the survey are now being taken up by the hospital managers for further action.

Treatment of herpes simplex and varicella zoster infections

The introduction of antiviral agents such as acyclovir has had a remarkable impact on management of patients with viral infections. In this article the authors outline the management of herpes simplex and varicella zoster infections, giving specific guidelines for treatment with acyclovir.

HIV infection of monocyte-derived macrophages in vitro reduces phagocytosis of Candida albicans

HIV-1 infection of peripheral blood monocyte-derived macrophages (MDMs) is unrelated to the level of CD4 expression on the surface of the cell, is associated with considerable donor variability, causes minimal cytopathology, and results in peak viral antigen production after 2 weeks of infection. Phagocytosis of opsonized Candida albicans by MDMs infected in vitro with several strains of HIV was compared with that of uninfected cells from the same donors; the proportion of MDMs containing the fluorescein isothiocyanate-labeled yeast was determined by flow cytometry and phase contrast microscopy. The intracellular localization of C. albicans was confirmed by confocal microscopy. Using paired MDMs from nine donors, 81% of uninfected and 53% of HIV-infected MDMs phagocytosed C. albicans. In addition, the number of yeast per cell was significantly higher in uninfected MDMs than in HIV-infected cells (mean 6.1 versus 2.5). These findings may partially explain the high incidence of mucocutaneous candidiasis in HIV-infected patients with advanced disease.

Transplantation of encapsulated bovine chromaffin cells in the sheep subarachnoid space: a preclinical study for the treatment of cancer pain

Chromaffin cells have been shown to release a combination of pain-reducing neuroactive compounds including catecholamines and opioid peptides. The allogeneic transplantation of chromaffin cells in the subarachnoid space has been shown to alleviate pain in various rodent models and possibly in terminal cancer patients. Because of the shortage of human cadaver donor tissue, we are investigating the possibility of transplanting xenogeneic cells in polymer capsules. In this technique, cells are surrounded by a permselective synthetic membrane whose pores are suitably sized to allow diffusion of nutrients, neurotransmitters and growth factors, but restrict the diffusion of the large molecules of the immune system and prevent contact with immunocompetent cells. The encapsulation technique therefore allows transplantation of xenogeneic tissue between species as well as retrieval of transplanted cells. Previously we have reported that encapsulated bovine chromaffin cells survive and alleviate pain in various rodent models. The purpose of the present study was to assess the feasibility of implanting a human sized device in a large animal model. Adrenals from 5 calves were surgically removed; chromaffin cells were isolated from these glands using a collagenase-based digestion-filtration technique. Cells were loaded into acrylic-based tubular (5 cm long, 920 microns wide) permselective capsules attached to silicone tethers. The capsules were maintained in vitro for at least 7 days following the encapsulation procedure. Nicotine evoked release was analyzed in a defined subgroup from each batch. One capsule was then implanted using a guiding cannula system in the lumbar subarachnoid space of each sheep for 4 (n = 5) and 8 (n = 1) wk. All capsules were retrieved intact by gentle pulling on the silicone tether. Except for one capsule, the evoked catecholamine release of the retrieved capsules was in the same range as that of other capsules from the same cohort that had been maintained in vitro. All retrieved capsules were devoid of host cell reaction. Clusters of viable cells dispersed in an alginate immobilizing matrix were observed throughout all the implanted capsules. This study demonstrates the feasibility of transplanting functional encapsulated xenogeneic chromaffin cells into the cerebrospinal fluid of a large animal model using a capsule of appropriate dimensions for human implants. We believe that these results suggest the appropriateness of human clinical trials in patients suffering from refractory terminal cancer pain.

Diagnostic X-ray and ultrasound exposure and risk of childhood cancer

In a population-based case-control study of 642 childhood cancer cases and the same number of matched controls in Shanghai, China, we evaluated the relationship between diagnostic X-ray (preconception, pre- and post-natal) and antenatal ultrasound exposure and the subsequent risk of developing three major types of childhood cancer (acute leukaemia, lymphoma and brain tumours) and all childhood neoplasms combined. Consistent with previous studies, prenatal X-ray exposure was found to be associated with an 80% increased risk of childhood cancers, although the estimation was based on 4% and 2% exposed cases and controls and was only marginally statistically significant (P = 0.08). Post-natal X-ray exposure was also linked with a small elevation in the risk of all cancers and the major categories of malignancies in children. Little evidence, however, was found to relate parental preconception X-ray exposure with the subsequent cancer risk in offspring, regardless of the exposure window and the anatomical site of X-ray exposures. This study adds further to the growing literature indicating that antenatal ultrasound exposure is probably not associated with an increased risk of childhood cancer.

HIV replication in chronically infected macrophages is not inhibited by the Tat inhibitors Ro-5-3335 and Ro-24-7429

Human immunodeficiency virus infects different cell types including CD4+ lymphocytes and monocyte-derived macrophages (MDMs). We have examined the activity of the HIV-1 Tat inhibitors Ro-5-3335 and Ro-24-7429 in cultured human peripheral MDMs. Monocytes were isolated from HIV-seronegative donors by gradient centrifugation and plastic adherence. MDMs and unfractionated peripheral blood mononuclear cells (PBMCs) were infected with HIV Ba-L and then treated with drug either immediately (acute infection) or after 4 days (PBMCs) or 14 days (MDMs) (chronic infection). Inhibition of HIV replication by each drug was assessed by quantitation of HIV p24 antigen in culture supernatant using an enzyme immunoassay. In acutely infected MDMs, Ro-5-3335 (10 microM) and Ro-24-7429 (10 microM) resulted in 77% and 99% mean inhibition, respectively, of HIV replication with a clear dose response at lower concentrations; chronically infected MDMs were much less susceptible to these drugs, with both compounds inhibiting p24 antigen production by less than 50% at 10 microM. The drugs had no deleterious effect on cell viability at any concentration tested. In acutely infected PBMCs Ro-5-3335 and Ro-24-7429 resulted in 68% and 68.5% mean inhibition at 10 microM; when the compounds were added 4 days after infection inhibition was less than 50% compared with controls. Thus, the Tat inhibitors were effective in inhibiting acute HIV infection in MDMs but not in chronically infected cells, findings that differ from those of published studies using continuous lymphoblastoid cell lines.

Thrombocytopenia secondary to high valproate levels in children with epilepsy

We reviewed the frequency of valproate-induced thrombocytopenia in children with epilepsy in our institution. Sixty-four (21%) of 306 children taking valproate developed thrombocytopenia. Thirty-two of these 64 patients had at least one platelet count lower than 100 x 10(3)/mm3. Eight patients developed signs of bleeding. Low platelet levels were typically noted in patients with serum valproate levels of over 140 micrograms/mL, and reduction of the medication dose usually resulted in a prompt increase in the number of platelets. Only one patient developed thrombocytopenia unrelated to high serum drug levels, and her platelet count did not improve until the drug was discontinued. Neither the age of the patient nor the use of additional antiepileptic medication correlated with the platelet count. However, duration of valproate use was related. These data suggest that, although valproate may cause thrombocytopenia via more than one mechanism, by far the most common factor is the presence of high valproate levels. Thus, the medication can be safely lowered in most patients with thrombocytopenia rather than discontinued altogether. Platelet counts should probably be monitored more carefully in patients known to have higher drug levels.

Correlation between response to acyclovir and foscarnet therapy and in vitro susceptibility result for isolates of herpes simplex virus from human immunodeficiency virus-infected patients

In vitro susceptibility testing of herpes simplex virus (HSV) isolates will play an increasingly important role in guiding the clinical management of immunocompromised hosts who have lesions that are poorly responsive to therapy with standard antiviral agents. We assessed the correlation between the in vitro susceptibility result using a plaque reduction assay in Vero cells and the response to antiviral therapy with acyclovir or foscarnet for 243 clinical isolates of HSV collected from 115 human immunodeficiency virus-infected patients. The in vitro results and clinical responses were highly associated for both acyclovir and foscarnet (P < 0.001 and P < 0.001, respectively). The predictive values of a susceptible result (50% effective concentrations, < 2 micrograms/ml for acyclovir and < 100 micrograms/ml for foscarnet) for complete healing of lesions were 62% for acyclovir and 82% for foscarnet; the predictive values of a resistant result for failure to heal were 95% for acyclovir and 88% for foscarnet. Thus, in vitro testing has clinical utility in guiding therapy, although the 1 to 2 weeks required to derive a definitive result by the plaque reduction assay is a major limitation.

Workload measurement: A survey of computerized data collection

The results of a national survey which examined current computer usage and occupational therapist direct entry of Workload Measurement Data is presented. Results indicated an almost equal distribution of departments using computers versus not using computers. A variety of software packages are used for the purposes of collecting workload measurement data, but the majority of departments use customized in-house programmes. The most common method of data entry was a clerk in a central location, however, a number of departments are considering a switch to therapist direct entry. Advantages and disadvantages of both methods were described by survey respondents.