Evaluation of pulmonary alveolar epithelial integrity by the detection of restriction to diffusion of hydrophilic solutes of different molecular sizes.

The rate of transfer of a hydrophilic solute from the alveoli to pulmonary blood following inhalation as an aerosol depends on the molecular size of the solute and the permeability of the alveolar epithelium. The value of this measurement for assessing damage to the epithelium in lung disease is compromised by cigarette smoking, which accelerates clearance by unknown mechanisms. The rates of clearance of (99m)Tc-labelled diethylenetriaminepenta-acetic acid (DTPA) (molecular mass 492 Da) and (113m)In-labelled biotinylated DTPA (B-DTPA) (molecular mass 1215 Da) were monitored simultaneously by dynamic gamma-radiation camera imaging following simultaneous inhalation, and compared between eight normal non-smoking subjects and nine habitual cigarette smokers. The clearance rates of DTPA were 0.95 (S.D. 0.39)%/min in non-smokers and 4.13 (1.06) %/min in smokers. These were about twice the clearance rates of B-DTPA, which in the corresponding groups were 0.41 (0.26) and 2.12 (0.72)%/min respectively. The ratio of the B-DTPA/DTPA clearance rates was, in all subjects, less than the ratio (0.74) of the cube roots of the molecular masses of the solutes, assumed to correspond to the ratio of their free diffusion coefficients in water, and was not significantly different between smokers and non-smokers. As alveolar permeability increased, the ratio of clearance rates in the entire population showed a significant trend to increase in a non-linear fashion towards the value corresponding to the ratio of the free diffusion coefficients. We conclude that the diffusion of at least the larger of these two solutes through the pulmonary alveolar epithelium is restricted (i.e. associated with a reflection coefficient greater than zero). Cigarette smoking, however, does not appear to cause a loss of this restriction, and may increase solute clearance by other mechanisms, such as reducing fluid volume within the alveolus, thereby raising the local radiotracer concentration, or increasing the number of pores available for solute exchange without affecting pore size. Conversely, if restriction was lost in lung disease, the ratio of the clearance rates of two solutes of dissimilar sizes could be used to detect disease in smokers as well as non-smokers.

Genetic analysis of human immunodeficiency virus type 1 strains from patients in Cyprus: identification of a new subtype designated subtype I.

DNA sequences encoding the C2 to V3 region of envelope glycoprotein gp120 of human immunodeficiency virus type 1 (HIV-1) were amplified by PCR from uncultured peripheral blood mononuclear cells obtained from 24 of 25 HIV-1-seropositive patients from Cyprus. By using a heteroduplex mobility assay (HMA), all amplified products were studied genetically and compared with 16 previously characterized HIV-1 strains belonging to subtypes A through F. HMA results revealed that HIV-1 gp120 sequences from 15 of our patients were of subtype B of HIV-1, whereas one isolate was of subtype C. However, gp120 sequences from eight patients had no obvious similarities to the known subtypes as defined by HMA. DNA sequencing and phylogenetic analyses of molecular clones confirmed the HMA results and placed the eight undefined HIV-1 isolates into three distinct genetic clusters. On the basis of branch topology and lengths of the phylogenetic tree, we conclude that one group consisting of three clones from two patients represents a new HIV-1 env subtype, which we have termed subtype I. The remaining two sequence clusters, consisting of five sequences from four patients and two sequences from two other patients, are distally related to subtypes A and F. These data demonstrate the extensive heterogeneity of HIV-1 in Cyprus, including the presence of new subtype.

Relationship between herpes simplex virus ulceration and CD4+ cell counts in patients with HIV infection.

OBJECTIVE: To establish the incidence of herpes simplex virus (HSV) ulceration in relation to CD4+ cell counts in HIV-infected patients. DESIGN: Swabs were taken from all ulcerated lesions in HIV-infected patients and cultured for HSV. CD4+ cell counts were performed at regular intervals. SETTING: The HIV unit at a London teaching hospital (the Royal Free Hospital, London, UK). PATIENTS: All HIV-infected patients (n = 500) attending the HIV unit. RESULTS: Two hundred and twenty-three swabs were obtained from 118 patients; 83 (37.2%) swabs from 62 (52.5%) patients were positive for HSV. Of 96 swabs taken from patients with CD4+ cell counts < 50 x 10(6)/l, 56 (58.3%) were positive for HSV, compared with 27 of 127 (21.2%) swabs from patients with higher CD4+ cell counts (P < 0.0001). Of patients with CD4+ cell counts < 50 x 10(6)/l, 37 of 47 (78.7%) had positive cultures compared with 25 of 71 (35.2%) of patients with higher counts (P < 0.0001). This trend was observed with swabs from all body sites; sufficient samples were available from oral and perianal lesions to demonstrate statistical significance (P < 0.0001 and P = 0.007, respectively). CONCLUSIONS: These results show a sharp rise in the incidence of HSV with CD4+ cell counts < 50 x 10(6)/l and thus provide important data for the design of studies of anti-HSV prophylaxis. Furthermore, since nearly 60% of all ulcers in patients with such low CD4+ counts are HSV-positive, we suggest appropriate empirical therapy on presentation.

Alveolar macrophage populations are distorted in immunocompromised patients with pneumonitis.

Alveolar macrophages (AM) were obtained by bronchoalveolar lavage (BAL) from patients presenting with pneumonitis: 30 human immunodeficiency virus (HIV)-infected individuals and 12 transplant recipients. Nine normal volunteers acted as controls. The cells were washed and cytospins prepared. Monoclonal antibodies (MoAbs) and immunoperoxidase methods were used to analyse the expression of HLA-DR molecules as well as phenotypic macrophage markers. P values apply to the differences between medians using the Mann-Whitney test. Median percentages of macrophages, lymphocytes and neutrophils were similar in all three groups. No differences were found in the median percentages of macrophages expressing the monocyte phenotype (MoAb UCHM1, CD14). However, in HIV-infected patients and transplant recipients a median of only 45% of macrophages expressed the pan-macrophage phenotype identified by MoAb EBM11 (CD68) in contrast with 98% in the normal volunteers. The AM population expressing the dendritic cell marker (MoAb RFD1) was also markedly reduced in both groups of immunocompromised patients (2 vs 28% in normal volunteers). Transplant recipients had significantly more phagocytic cells identified by MoAb RFD7 than the HIV-infected patients (25 vs 2%), but the numbers were still low when compared with the volunteers (48%). HLA-DR expression on BAL cells was reduced by 90% in both immunocompromised groups. For the transplant recipients, severity of pneumonitis was correlated with expression of dendritic cell marker RFD1, (Spearman's rank correlation r = 0.538, p less than 0.05) and pan-macrophage marker EBM11 (r = 0.581, p less than 0.05), while no such correlation was found in HIV-infected patients. These results suggest that a defective macrophage population is probably a serious factor contributing to immunosuppression.

Severe cytomegalovirus pneumonitis in HIV infected patients with higher than average CD4 counts.

BACKGROUND: Cytomegalovirus may replicate within the lungs both of recipients of transplants and of patients infected with the human immunodeficiency virus (HIV). A hypothesis formulated by this group was that a host damaging immune response might be provoked by cytomegalovirus infection and cause a severe pneumonitis in recipients of allogeneic transplants, whereas the progressive impairment of cellular immunity in patients with HIV disease would preclude a damaging immune response in the lungs, and thus protect these patients from severe cytomegalovirus pneumonitis. This study set out to discover whether severe cytomegalovirus pneumonitis arises in HIV infected patients. METHODS: Data were prospectively collected on severity of pneumonitis and infectious agents identified in consecutive respiratory episodes in HIV infected patients undergoing diagnostic bronchoalveolar lavage during 20 months. RESULTS: Eighty five episodes of pneumonitis occurred in 68 patients. Cytomegalovirus was identified as the only infectious agent in nine episodes (nine patients). Seven of the episodes were mild; all these patients had CD4 counts below 0.1 x 10(9)/1. The remaining two episodes were severe and ventilatory support was required. In both cases the CD4 counts were above 0.2 x 10(9)/1 and HIV infection appeared to have been acquired shortly before presentation. CONCLUSION: Although rare, severe cytomegalovirus pneumonitis may occur in HIV infected patients. Both patients with severe pneumonitis in this series had relatively well preserved immune function. These findings support the hypothesis that severe cytomegalovirus pneumonitis is an immunopathological condition.

Open access clinic providing HIV-I antibody results on day of testing: the first twelve months.

OBJECTIVES: To determine the sociodemographic profile, risk category, and prevalence of HIV-I infection among people attending a clinic providing counselling, medical advice, and results of HIV-I antibody testing on the day of consultation; to determine the stage of infection and peripheral blood CD4 cell count among attenders with detectable HIV-I antibodies. DESIGN: Analysis of prospectively collected data for the 12 months from March 1989. SETTING: Same day testing clinic run by the HIV/AIDS team at an urban teaching hospital. PATIENTS: 561 consecutive people choosing to attend and proceeding to HIV-I testing. RESULTS: The demand for the service caused it to run to capacity within six months. The median age of those attending was 28 years and 65% (364 patients) were male. The overall prevalence of HIV-I infection was 3.9% (22 patients). The greatest prevalence was in men reporting their primary risk as homosexual contact (11.9%, 13/109). The median CD4 cell count in the 22 patients who had detectable HIV-I antibodies was 0.31 x 10(9) cells/l (normal range 0.5 x 10(9)/l to 1.2 x 10(9)/l). Twenty of these patients were asymptomatic (Centers for Disease Control stages II or III), 14 had CD4 cell counts below 0.5 x 10(9)/l. CONCLUSIONS: There is a recognisable demand for a service providing rapid results of HIV-I antibody testing in this setting. The overall seroprevalence of 3.9% is comparable with the 5.8% reported from freestanding clinics in the United States. Most patients with HIV-I antibodies detected in this way are asymptomatic but could benefit from early medical intervention because of low CD4 cell counts.