Influence of infection on malaria-specific antibody dynamics in a cohort exposed to intense malaria transmission in northern Uganda.

The role of submicroscopic infections in modulating malaria antibody responses is poorly understood and requires longitudinal studies. A cohort of 249 children ≤5 years of age, 126 children between 6 and 10 years and 134 adults ≥20 years was recruited in an area of intense malaria transmission in Apac, Uganda and treated with artemether/lumefantrine at enrolment. Parasite carriage was determined at enrolment and after 6 and 16 weeks using microscopy and PCR. Antibody prevalence and titres to circumsporozoite protein, apical membrane antigen-1 (AMA-1), merozoite surface protein-1 (MSP-119 ), merozoite surface protein-2 (MSP-2) and Anopheles gambiae salivary gland protein 6 (gSG6) were determined by ELISA. Plasmodium falciparum infections were detected in 38·1% (194/509) of the individuals by microscopy and in 57·1% (284/493) of the individuals by PCR at enrolment. Antibody prevalence and titre against AMA-1, MSP-119 , MSP-2 and gSG6 were related to concurrent (sub-)microscopic parasitaemia. Responses were stable in children who were continuously infected with malaria parasites but declined in children who were never parasitaemic during the study or were not re-infected after treatment. These findings indicate that continued malaria infections are required to maintain antibody titres in an area of intense malaria transmission.

Genetics of susceptibility to Plasmodium falciparum: from classical malaria resistance genes towards genome-wide association studies.

Plasmodium falciparum represents one of the strongest selective forces on the human genome. This stable and perennial pressure has contributed to the progressive accumulation in the exposed populations of genetic adaptations to malaria. Descriptive genetic epidemiology provides the initial step of a logical procedure of consequential phases spanning from the identification of genes involved in the resistance/susceptibility to diseases, to the determination of the underlying mechanisms and finally to the possible translation of the acquired knowledge in new control tools. In malaria, the rational development of this strategy is traditionally based on complementary interactions of heterogeneous disciplines going from epidemiology to vaccinology passing through genetics, pathogenesis and immunology. New tools including expression profile analysis and genome-wide association studies are recently available to explore the complex interactions of host-parasite co-evolution. Particularly, the combination of genome-wide association studies with large multi-centre initiatives can overcome the limits of previous results due to local population dynamics. Thus, we anticipate substantial advances in the interpretation and validation of the effects of genetic variation on malaria susceptibility, and thereby on molecular mechanisms of protective immune responses and pathogenesis.

Genetic epidemiology of susceptibility to malaria: not only academic exercises.

Descriptive genetic epidemiology represents the initial step of a logical procedure of linked and consequential phases spanning from the identification of genes involved in the resistance/susceptibility to diseases, to the determination of the underlying mechanisms and finally to the possible translation of the acquired knowledge in new control tools. In malaria, the rational development and potential of this pathway is based on complementary interactions of heterogeneus disciplines going from epidemiology (the transmission, the infection, the disease) to vaccinology passing through genetics, pathogenesis, and immunology. Several epidemiological approaches can be applied in the study of the genetic susceptibility to Plasmodium falciparum malaria: intra-ethnic case-control studies comparing genetic candidates of resistance/susceptibility between subjects with different presentation of malaria (from severe disease to asymptomatic infection) and the general healthy population is the classic approach; inter-ethnic comparative analyses among populations with different genetic backgrounds, exposed to the same epidemiological context and showing different susceptibility to the disease is a further, complementary, strategy.

Haemoglobin C and S in natural selection against Plasmodium falciparum malaria: a plethora or a single shared adaptive mechanism?

Conclusive evidence exists on the protective role against clinical Plasmodium falciparum malaria of Haemoglobin S (beta 6Glu-->Val) and HbC (HbC; beta 6Glu-->Lys), both occurring in sub-Saharan Africa. However, the mechanism/s of the protection exerted remain/s debated for both haemoglobin variants, HbC and HbS. Recently, an abnormal display of PfEMP1, an antigen involved in malaria pathogenesis, was reported on HbAC and HbCC infected erythrocytes that showed reduced cytoadhesion and impaired rosetting in vitro. On this basis it has been proposed that HbC protection might be attributed to the reduced PfEMP1-mediated adherence of parasitized erythrocytes in the microvasculature. Furthermore, impaired cytoadherence was observed in HbS carriers suggesting for the first time a convergence in the protection mechanism of these two haemoglobin variants. We investigated the impact of this hypothesis on the development of acquired immunity against P. falciparum variant surface antigens (VSA) encoding PfEMP1 in HbC and HbS carriers in comparison with HbA of Burkina Faso. Higher immune response against a VSA panel and several malaria antigens were observed in all adaptive genotypes containing at least one allelic variant HbC or HbS in the low transmission urban area whereas no differences were detected in the high transmission rural area. In both contexts the response against tetanus toxoid was not influenced by the beta-globin genotype. Thus, these findings suggest that both HbC and HbS affect the early development of naturally acquired immunity against malaria. We reviewed the hypothesized mechanisms so far proposed in light of these recent results.

Very large long-term effective population size in the virulent human malaria parasite Plasmodium falciparum.

It has been proposed that the virulent human malaria parasite Plasmodium falciparum underwent a recent severe population bottleneck. In order to test this hypothesis, we estimated the effective population size of this species from the patterns of nucleotide substitution at 23 nuclear protein-coding loci, using a variety of methods based on coalescent theory. Both simple methods and phylogenetically based maximum-likelihood methods yielded the conclusion that the effective population size of this species has been of the order of at least 10(5) for the past 300,000-400,000 years.

Bronchoalveolar lavage in immunocompromised patients. Clinical and functional consequences.

Fiberoptic bronchoscopy and bronchoalveolar lavage are major tools in the diagnosis of acute pneumonia in immunocompromised patients. We conducted a prospective study to assess the morbidity associated with this procedure in 14 patients with AIDS and 16 patients with drug-induced immunosuppression. No patient had a PaO2 lower than 70 mm Hg with additional oxygen. Clinical data, chest roentgenogram, pulmonary function test, forced vital capacity, forced expiratory volume in one second, and arterial blood gases were recorded before and after bronchoscopy. Arterial oxygen saturation was monitored during the procedure, and initial, lowest, and final saturation values were noted. The patients were separated into three groups on the basis of chest roentgenographic findings. No procedure-induced pneumonia or need for tracheal intubation occurred. Minor clinical symptoms induced by the lavage in seven patients resolved spontaneously. By contrast, mean SaO2 decreased markedly during the procedure from 94 +/- 3 to 87 +/- 5 percent (p less than 0.0001) and returned to only 89 +/- 5 percent at the end of the procedure. Lowest SaO2 during the procedure and final SaO2 correlated poorly with initial SaO2 but correlated well with initial FVC and FEV1 (p less than 0.01). The PFT values were lower following bronchoscopy. O2 desaturation was more pronounced in patients with severe roentgenographic abnormalities. No significant differences were found between the three groups of patients, or between the AIDS and DII patients in terms of changes in PFT values. We conclude that in immunocompromised patients, bronchoscopy with BAL induces severe arterial oxygen desaturation which is correlated with initial PFT and chest roentgenographic findings, and most of these abnormalities are transient and do not lead to major complications.

Topical upper airway anaesthesia with lidocaine increases airway resistance by impairing glottic function.

OBJECTIVE: To assess if two different forms of upper airway topical anaesthesia induce similar changes in airway flow resistance (Rrs). DESIGN: Serial measurements of Rrs before and after topical anaesthesia with acqueous or paste lidocaine. SETTING: Lung function test laboratory. PARTICIPANTS: 9 normal men with documented normal lung function tests. INTERVENTIONS: 2 different session of topical upper airway anaesthesia with 100 mg of liquid 5% lidocaine and 100 mg of 2% lidocaine paste, respectively. MEASUREMENTS AND RESULTS: Rrs was measured by the random noise forced oscillation technique. Fiberoptic upper airway examination was performed in two subjects. Rrs increased on average by 81% after lidocaine spray and by 68% after lidocaine paste (p < 0.005, respectively) with no difference in the magnitude of Rrs increase between the two modes of anaesthesia studied. This increase lasted 13 +/- 3 min (spray) and 12 +/- 3 min (paste), respectively (p = ns). Fiberoptic examination of the two most responders showed inspiratory laryngeal collapse. CONCLUSIONS: Topical upper airway anaesthesia transiently increases Rrs with no specific effects regarding the drug presentation. Laryngeal dysfunction may be one mechanisms involved in Rrs increase following upper airway topical anaesthesia. Such findings may explain some poor respiratory tolerance reported during endoscopy.

Contribution of bronchoalveolar lavage to the diagnosis of posttraumatic pulmonary fat embolism.

OBJECTIVE: To verify whether the determination of the percentage of cells recovered by bronchoalveolar lavage and containing fat inclusions is a useful diagnostic tool of posttraumatic pulmonary fat embolism. DESIGN: Prospective study. SETTING: Surgical Intensive Care Units in two university hospitals. PATIENTS: 56 successive trauma patients needing prolonged postinjury mechanical ventilation, including 4 with clinical definite fat embolism syndrome, 5 in whom the diagnosis had been clinically suspected but was impossible to confirm or exclude before bronchoscopy, and 47 with no clinical evidence of the syndrome. Control groups included 8 patients without previous trauma who developed ARDS and 6 healthy surgical patients. METHODS: Bronchoalveolar lavage was performed within the first post-traumatic 3 days in trauma patients, at the beginning of the pulmonary disease in non trauma ARDS patients and just after anesthesic induction in healthy ortopedic patients. The magnitude of lipid content in alveolar cells was compared with the clinical pattern of the pulmonary fat embolism syndrome retrospectively evaluated at the seventh day postinjury in trauma patients. RESULTS: All the patients with definite fat embolism syndrome had more than 70% of lavage cells containing fat droplets. The group of patients in whom the diagnosis of the fat embolism syndrome was suspected had percentages of fat cells above 30% in 4 out of 5 patients. A percentage of fat cells above 30% was only observed in 7 out of the 47 patients without clinical evidence of the syndrome. The percentage varied between 0% to 35% in the group of non trauma ARDS patients and between 0 to 5% in healthy surgical patients. CONCLUSION: Lipid inclusions in alveolar cells are common during traumatic and non-traumatic respiratory failure. Determination of the percentage of cells recovered by bronchoalveolar lavage and containing fat droplets may contribute to the diagnosis of the fat embolism syndrome in mechanically-ventilated trauma patients with respiratory failure provided that the significant threshold would be 30%.

Natural selection on apical membrane antigen-1 of Plasmodium falciparum.

The Apical Membrane Antigen-1 (AMA-1) is a protein localized in the apical organelles of the merozoite, one of the stages in the life cycle of malaria parasites (Plasmodium spp.) that infects the vertebrate host. This antigen, which is encoded by a single polymorphic locus, plays a role in evading immune detection and mediating invasion into target host cells. We found evidence of positive Darwinian selection on immunogenic regions of P. falciparum AMA-1 favoring genetic diversity in the T-cell epitopes and in regions likely to interact with host antibodies. These results support the hypothesis that polymorphism at the AMA-1 locus in maintained by balancing selection arising from host immune recognition.

Biased amino acid composition in repeat regions of Plasmodium antigens.

Many malarial antigens contain extensive arrays of tandemly repeated short amino acid sequences, and much of the antibody response induced by malaria infections is directed against these repeats. Indeed, it has been hypothesized that these repeats function to elicit a relatively ineffective T-cell-independent antibody response by the host. In order to test this hypothesis, tandem repeats of Plasmodium species were examined for a bias in composition favoring amino acids likely to form epitopes for the antibody. The genome of Plasmodium is very A+T-rich, and nucleotide compositional bias will, in itself, lead to a high proportion of hydrophilic amino acids. When this bias was controlled for, Plasmodium antigens did not show a higher proportion of hydrophilic amino acids than expected, but there was a significant reduction in the proportion of hydrophobic amino acids in the repeats of the antigens. The amino acid composition of the repeats was thus strikingly different from those seen both in the remainder of the antigens and in a sample of Plasmodium falciparum housekeeping genes.

[Value of the LDH level in pneumocystis carinii pneumonia in patients infected with human immunodeficiency virus]. / Intérêt de la détermination du taux des LDH au cours de la pneumopathie à Pneumocystis carinii chez les patients infectés par le virus de l'immunodéficience humaine.

LDH levels were measured in 30 AIDS patients with P. carinii pneumonia (PCP), evidenced by bronchoalveolar lavage, and 12 HIV 1-infected patients with P. carinii-negative bronchial or pulmonary manifestations, constituting the control group. Extrapulmonary causes of elevated LDH levels were eliminated. In the case of bronchopneumopathy, the sensitivity and the specificity of an abnormal LDH level for suggesting PCP were both 83%. For an interstitial pneumopathy, the sensitivity was the same but the specificity was 100%. During a one year period, the prevalence of PCP in our department was 69%. The positive and negative predictive values of increased LDH levels in HIV-infected patients were, respectively: 92 and 63% for bronchopneumopathy, and 100 and 73% for interstitial pneumopathy. Furthermore, the lowering and then the normalization of the LDH value were observed in all PCP cases with a favorable outcome. This simple yet highly sensitive laboratory analysis should be used for the diagnosis and monitoring of all bronchopneumopathies in HIV-infected patients.

Do nasal ciliary changes reflect bronchial changes? An ultrastructural study.

Ciliary dyskinesia is characterized by recurrent respiratory tract infections secondary to abnormal ciliary structure and function. The diagnosis of ciliary dyskinesia is based on the detection of axonemal ultrastructural abnormalities (AUA) is respiratory mucosa samples. In most cases, the diagnosis of AUA is made on samples obtained from nasal ciliated cells with little discomfort to the patient. However, no studies have been performed in the same patient to confirm whether nasal samples reflect bronchial ciliary changes. To answer this question and to determine whether it is necessary to sample bronchial cells for the diagnosis of ciliary dyskinesia, we investigated 12 patients (between the age of 5 and 63 yr) with chronic sputum production. The presence of situs inversus, bronchiectasis, chronic sinusitis, and sterility was investigated to determine an inherited disorder. Two groups were established: Group 1 = six patients with an inherited disorder and Group 2 = six patients without evidence of an inherited disorder. Samples were obtained by brushing or biopsy of nasal and bronchial mucosa and were processed for transmission electron microscopy. In Group 1, the mean AUA was 65.2 +/- 11.4%. The following predominant axonemal defects were found: absence of dynein arms (DA) (four patients), central complex abnormalities (CC) (one patient), and various AUA (one patient). Nasal and bronchial samples correlated significantly for total AUA (r' = 1, p < 0.01) and for outer DA defects (r' = 0.96, p < 0.05). A good but not significant correlation was found for inner DA (r' = 0.83) and peripheral microtubule (PM) defects (r' = 0.71). In Group 2, the mean AUA was 9.6 +/- 2.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Ciliary abnormalities in bronchial epithelium of smokers, ex-smokers, and nonsmokers.

Although respiratory changes induced by tobacco smoke have been extensively described, no study has focused on ciliary abnormalities associated with chronic smoking. Ciliary ultrastructure was studied in 37 adults with chronic sputum production (CSP) consisting of 13 current smokers (Group 1), 5 ex-smokers (Group 2), and 19 nonsmokers (Group 3). Five healthy nonsmokers constituted the control group (Group 4). Clinical and radiologic data and respiratory function tests were recorded. Acute respiratory infection was diagnosed by culture of tracheobronchial secretions obtained during bronchoscopy. Bronchial ciliated cells were obtained and processed for transmission electron microscopy. Within each group, the percentages of abnormal cilia were similar in patients with either chronic bronchitis or bronchiectasis and in patients with or without acute infection. The percentage of axonemal ultrastructural abnormalities (AUA) was higher in smokers (16.5% +/- 2.7%) and ex-smokers (17.5% +/- 7%) than in nonsmokers (5.2% +/- 1%) or control subjects (0.7% +/- 0.2%) (p < 0.0002). The AUA were polymorphic, characteristic of acquired ultrastructural changes. These results suggest that chronic smoking may induce an increased number of abnormal cilia which could participate in impairment of tracheobronchial clearance and which appears to be independent of the etiology of CSP.

Bronchoalveolar disease in dyskeratosis congenita.

Dyskeratosis congenita (DC) is an unusual familial disorder primarily affecting the skin and its appendages. We report the case of a DC patient with chronic respiratory tract involvement, confirming the features previously reported by a small number of authors: 1) chronic bronchoalveolar involvement is not unusual in this disorder; 2) the main features are early sputum production with subsequent bronchial and alveolar destruction; 3) after onset of dyspnoea the course is rapidly fatal, with progressive respiratory failure. Immune deficiency and repeated bronchoalveolar infections may be involved in the pathogenesis of these manifestations.

Modified epithelial cell distribution in chronic airways inflammation.

Although airway epithelium is known to be modified during chronic respiratory diseases, epithelial cells have rarely been precisely quantified. We therefore intended to evaluate epithelial cell distribution in inflammatory airways, using a cytological approach. Nasal airway cells in 12 patients with nonallergic chronic rhinitis were sampled by brushing, quantified after cytocentrifugation and compared to those from eight controls. Cell populations were quantified after May-Grünwald Giemsa staining and alpha-tubulin immunolabelling to demonstrate ciliary differentiation. When compared to controls, rhinitis patients exhibited lower percentages of ciliated cells (59 +/- 4 versus 32 +/- 2%, respectively), and higher percentages of goblet (24 +/- 3 versus 37 +/- 2%) and basal cells (9 +/- 1 versus 18 +/- 2%). After tubulin immunolabelling, positive staining was specifically detected in cells with cilia (LC+), and in the cytoplasm of some small round cells without obvious cilia (LC-). Fewer immunolabelled cells were detected in rhinitis patients than in controls (with significantly lower percentages of LC+ and higher percentages of LC-). Nasal brushing is an effective technique for quantification of airway epithelial cells. Tubulin immunolabelling is useful to detect ciliated cells and distinguishes another cell population, possibly preciliated cells. These cytological findings suggest the presence of modifications of epithelial differentiation and proliferation, possibly related to local chronic inflammation.

Effect of increased pressure on tracheal ciliary beat frequency.

Effects of increased ambient pressure on mucociliary clearance have been poorly investigated. The effects of increasing pressures on ciliary beat frequency (CBF) of guinea-pig tracheal rings were studied in vitro. Increased pressures of 25 and 100 kPa induced a significant and equivalent enhancement of CBF from 30 min after the pressure increase. The increase in CBF observed after a pressure increase of 50 kPa (inspiratory oxygen fraction = 21%), was significantly greater than that observed with an equivalent oxygen tension at atmospheric pressure, i.e. with a gas mixture containing 30% oxygen. Addition of N(G)-nitro-L-arginine methylester (L-NAME) inhibited the enhancement in CBF observed after the 25 kPa pressure increase. Addition of L-arginine reversed the effect of L-NAME. These results demonstrate that a pressure increase applied to tracheal rings, in vitro, induces an enhancement of ciliary beat frequency and that generation of nitric oxide may be involved in this ciliary stimulation.

Effects of local anaesthetics (lidocaine) on the structure and function of ciliated respiratory epithelial cells.

Sampling for nasal or bronchial ciliated cells requires the use of anaesthetic agents, but such drugs may interfere with the morphological or functional results. Lidocaine is the most frequently used local anaesthetic. In order to study the morphological and functional effects of lidocaine hydrochloride, we designed an experimental study on ciliated cells from guinea pig and bovine trachea. On guinea pig tracheal specimens, different lidocaine concentrations (0.05, 0.25 and 1%) were tested. Tracheal rings were immersed in either culture medium alone (control) or in different lidocaine concentrations. Measurements of ciliary beat frequency (CBF) were performed by the stroboscopic method. Tracheal rings were consecutively incubated in culture medium alone and a second set of measurements was performed. Tracheal rings were studied by light microscopy after incubation in either 1% lidocaine or in culture medium alone. On bovine tracheal specimens, a cotton wool swab impregnated with different lidocaine concentrations (0, 0.25, 1, 2.5 and 5%) was placed in contact with the tracheal mucosa. Three different kinds of samples were collected: the first one was used to study CBF, the second one (0.1 and 5%) was studied by scanning electron microscope (SEM) and the third (0.1 and 5%) by transmission electron microscopy (TEM). The results on guinea pig specimens show a significant but reversible CBF diminution for concentrations of 0.25 and 1% lidocaine and cellular lesions for the concentration of 1%.(ABSTRACT TRUNCATED AT 250 WORDS)