A genetic linkage map of chromosome 17

We have developed a genetic linkage map of 19 markers (including nine genes) on human chromosome 17, providing 13 reference points along virtually the entire length of this chromosome. The map covers an estimated 149 cM in length (sex-averaged), with a total length of 214 cM in females and 95 cM in males. This sex difference appears to be significant along virtually the entire length of the map. This map will be useful both for providing reference points for fine structure genetic and physical mapping and for genetic linkage studies of diseases, including von Recklinghausen neurofibromatosis and Charcot-Marie-Tooth disease.

A national survey of the prevalence of chloroquine resistant Plasmodium falciparum malaria in The Gambia

In The Gambia, 760 children less than 10 years of age with Plasmodium falciparum malaria were treated with chloroquine (25 mg/kg) and followed-up 2 and 9 d after the start of treatment. 700 children (92.1%) completed the study. The level of in vivo resistance to chloroquine varied by area from 0.4% to 16.4%. Of the 28 children found to have chloroquine resistant malaria, none was ill when seen at the 9 d follow-up and only 3 (10.3%) required further treatment with alternative antimalarials because of persistent high levels of parasitaemia. However, the fact that 30.4% of the children who completed the study had chloroquine in their urine at presentation may have masked the true level of resistance and led to underestimation of the clinical significance of these findings. The blood film at day 2 did not usefully predict resistance. 67 isolates were tested in vitro for chloroquine sensitivity. The mean EC50 was 15.5 nmol/litre, an eight-fold decrease in sensitivity from that of isolates tested in 1982. 8 (11%) of the isolates had EC50s above the WHO reference value for sensitive isolates of 18.3 nmol/litre, with values ranging from 22 to 65 nmol/litre of culture medium. Gambian isolates were sensitive to quinine (mean EC50 = 49.6 nmol/litre).

The epidemiology of Haemophilus influenzae meningitis in children under five years of age in The Gambia, West Africa

Haemophilus influenzae meningitis was studied over a 2-year period in children less than 5 years of age in a population-based, prospective study in The Gambia, West Africa. A total of 77 cases were recorded. The incidence was 60 cases/100,000 children less than 5 years of age and 297 cases/100,000 children less than 1 year of age. The peak prevalence was at the age of 5 months; 83% of the children were less than 1 year old and 45% were less than 6 months old. Only 55% of cases recovered completely. The distance to the nearest hospital was an important predisposing factor for a fatal outcome. Two cases were secondary. Many patients were anemic and underweight. The observations show that H. influenzae meningitis in The Gambia has an incidence as high as that in the USA, but that it has 10-fold more devastating outcome. If the infection is to be prevented by vaccination in The Gambia, immunization will have to be given very early in life.

Cellular immune responses to Plasmodium falciparum antigens in children receiving long term anti-malarial chemoprophylaxis

Fifty-two Gambian children who had received fortnightly chemoprophylaxis with maloprim, (pyrimethamine and dapsone), and 45 receiving placebo, were studied. Cellular immune responses to malaria antigens, measured by lymphoproliferative responses and interferon production, were higher in children who had received prophylaxis than in controls, although the anti-malarial antibody levels were lower. During a one-year period after termination of prophylaxis, there was no increase in the frequency of clinical episodes of malaria in the children who had received Maloprim. These results suggest that chemoprophylaxis for 3 years may lower malaria antibody levels, but does not interfere with the development of protective immunity, perhaps by enhancing cell-mediated immune responses to malaria in protected children.

Lack of an association between acute gastroenteritis, acute respiratory infections and malaria in young Gambian children

The incidence of acute gastrointestinal and acute respiratory infections was measured in 2 groups of approximately 750 Gambian children aged 3-59 months during a 3-year period. One group of children was partially protected against malaria by fortnightly chemoprophylaxis with Maloprim whilst children in the other group were infected much more frequently. Mortality from acute gastroenteritis and from acute respiratory infections was similar in the 2 groups. The proportions of children in each group who complained of gastrointestinal or severe respiratory symptoms on morbidity surveillance were also similar. Thus, no evidence was found to suggest that malaria plays either a direct or indirect role in causing acute gastrointestinal or respiratory infections in young children in The Gambia.

Differential non-responsiveness in humans of candidate Plasmodium falciparum vaccine antigens

Synthetic subunit vaccines to sporozoites, merozoites, and gametes are being developed for malaria. The vaccine strategy assumes that the population to be immunized will respond favorably to these vaccine antigens. Using sera of 35 adults and 50 children from the The Gambia, West Africa, where Plasmodium falciparum is highly endemic, we examined the humoral immune response to candidate malaria vaccine antigens from sporozoites, merozoites, and gametes. We observed widespread restricted immunogenicity to defined parasite antigens in children and adults. HLA typing of adult lymphocytes demonstrated a marked diversity in HLA haplotypes in this population. Our results and those from our studies in mice suggest that genetic factors may partly explain the immunological non-responsiveness. This may necessitate re-evaluation of the malaria vaccine strategy.

Human T cell recognition of polymorphic epitopes from malaria circumsporozoite protein

Lymphocytes obtained from forty individuals living in a malaria endemic area of West Africa were tested for in vitro proliferative responses to peptides representing variant regions of the immunodominant T cell domain of the circumsporozoite protein (amino acids 326 to 345, referred to as Th2R, and 361 to 380, referred to as Th3R) from three distinct strains of Plasmodium falciparum. A total of 83% of the individuals responded to at least one of the six peptides tested, confirming that these epitopes are immunodominant. A much greater number of individuals than expected by chance (32% of the responders to Th2R and 27% of the responders to Th3R) reacted to all three of the variant peptides for that epitope, indicating interdependency of the T cell responses, suggestive of cross-reactivity. Nevertheless, some subjects' T cells were clearly able to distinguish each variant peptide from the others. Using EBV transformed B cells, lymphocytes from 10 of the individuals were HLA typed. In this small group, HLA DRw13 was associated with a positive response to any of the peptides, whereas there was a negative association between DQw3 and response to any of the peptides. These results, although limited by the small sample size, suggest that recognition of T epitopes may be Ir gene linked. Our findings suggest that it may be possible to broaden the immunogenicity of an anti-sporozoite malaria vaccine.

Human T cell recognition of polymorphic epitopes from malaria circumsporozoite protein

Lymphocytes obtained from forty individuals living in a malaria endemic area of West Africa were tested for in vitro proliferative responses to peptides representing variant regions of the immunodominant T cell domain of the circumsporozoite protein (amino acids 326 to 345, referred to as Th2R, and 361 to 380, referred to as Th3R) from three distinct strains of Plasmodium falciparum. A total of 83% of the individuals responded to at least one of the six peptides tested, confirming that these epitopes are immunodominant. A much greater number of individuals than expected by chance (32% of the responders to Th2R and 27% of the responders to Th3R) reacted to all three of the variant peptides for that epitope, indicating interdependency of the T cell responses, suggestive of cross-reactivity. Nevertheless, some subjects' T cells were clearly able to distinguish each variant peptide from the others. Using EBV transformed B cells, lymphocytes from 10 of the individuals were HLA typed. In this small group, HLA DRw13 was associated with a positive response to any of the peptides, whereas there was a negative association between DQw3 and response to any of the peptides. These results, although limited by the small sample size, suggest that recognition of T epitopes may be Ir gene linked. Our findings suggest that it may be possible to broaden the immunogenicity of an anti-sporozoite malaria vaccine.

Presence of a non-HLA B cell antigen in rheumatic fever patients and their families as defined by a monoclonal antibody

Numerous investigators have suspected that there is a genetic predisposition to rheumatic fever (RF). In this context we have recently produced a series of monoclonal antibodies directed against B cells obtained from RF patients one of which, labeled D8/17, identifies a B cell antigen present in 100% of all RF patients studied. While the highest percentage of positive cells were exhibited by RF probands (33.5% +/- SE), the percentage of cells in unaffected siblings and parents was 14.6 and 13%, respectively. The percentage of positive cells in APSGN probands, unaffected siblings, and parents was 2.96, 3.86, and 2.8%, respectively. A low level of B cells (5-7%) bearing the D8/17 marker was seen in control patients. The segregation pattern of the phenotypes defined by the percentage of D8/17 positive cells within HLA-typed RF families are consistent with an autosomal recessive mode of inheritance not associated with the human MHC system. We postulate that these phenotypes indicate the presence of at least one necessary genetic factor for susceptibility to RF.

A comparative study of Lapudrine (chlorproguanil) and Maloprim (pyrimethamine and dapsone) as chemoprophylactics against malaria in Gambian children

A comparison has been made of Lapudrine (chlorproguanil) and Maloprim (pyrimethamine +dapsone) as malaria chemoprophylactics when given every two weeks for 3 years to Gambian children under the age of 5 years. Both drugs produced falls in spleen and malaria parasite rates and an increase in packed cell volume. Maloprim, but not chlorproguanil, significantly reduced the incidence of episodes of fever accompanied by malaria parasitaemia. Children who received Maloprim, but not those who received chlorproguanil, grew better than children in the placebo group. This finding suggests that brief clinical episodes of malaria are more important in impairing growth than more prolonged periods of asymptomatic parasitaemia. No serious side-effect attributable to either drug was observed. After chemoprophylaxis had been given for 3 malaria transmission seasons the level of resistance of Plasmodium falciparum to pyrimethamine and to chlorproguanil was about 10%.

Flanking markers for the gene causing von Recklinghausen neurofibromatosis (NF1)

The defective gene causing von Recklinghausen neurofibromatosis (NF1), one of the most common inherited disorders affecting the human nervous system, was recently mapped to chromosome 17. We have used additional DNA markers to further narrow and bracket the NF1 defect. A multipoint linkage analysis suggests that the NF1 gene is flanked by D17Z1 on the centromeric side and by EW 207 on the telomeric side of the long arm of chromosome 17. The identification of closely linked flanking markers should allow us to develop a reliable prenatal and presymptomatic diagnostic test for this serious neurological disorder and provides the basis for applying chromosome-specific cloning techniques for the isolation and characterization of the mutant gene.

Maternal administration of chloroquine: an unexplored aspect of malaria control

A health education package, designed to teach women to perceive and treat episodes of malaria, was tried in a rural area of The Gambia with no tradition of home based antimalarial therapy and a poor working knowledge of malaria. During the course of the rainy season, after a period of health education, 67.9% of the study mothers dispensed complete courses of chloroquine as instructed. Mothers were interviewed either weekly, monthly, halfway through or at the end of the 6 month study. Mothers interviewed weekly gave 65% more chloroquine than mothers interviewed less frequently. The implications of morbidity surveillance on chloroquine consumption, and of the study as a whole for Primary Health Care programmes are discussed.

An ELISA test for detecting chloroquine in urine

Two ELISA tests for detecting chloroquine in urine have been developed using polyclonal and monoclonal antibodies which react with the 7-chloro-4-amino-quinoline part of the chloroquine molecule and thus recognize chloroquine, its metabolites, and amodiaquine. The ELISAs were sensitive and specific and did not cross-react with other commonly used antimalarials. In a field trial the chloroquine ELISA performed better than the Dill Glazko or Haskins colorimetric tests. A small proportion of urines gave an apparently false positive reaction when tested at a dilution of 1:10, but not when tested at higher dilution.

Human T-cell recognition of the circumsporozoite protein of Plasmodium falciparum: immunodominant T-cell domains map to the polymorphic regions of the molecule

The definition of human T-cell antigenic sites is important for subunit vaccine development of a peptide immunogen if the goal is to allow antibody boosting during infection or to stimulate antibody-independent T-cell immunity. To identify such sites on the circumsporozoite (CS) protein of Plasmodium falciparum, 29 overlapping synthetic peptides spanning the entire CS protein were made and tested for their ability to stimulate peripheral blood lymphocytes from 35 adults living in a P. falciparum malaria-endemic region of West Africa. Three immunodominant domains were located outside the repetitive region. These domains, however, occurred in the polymorphic regions of the molecule, suggesting that parasite mutation and selection has occurred in response to immune pressure from T cells. Such polymorphism may impose an obstacle for vaccine development.

Immunity to malaria in young Gambian children after a two-year period of chemoprophylaxis

A cohort of 48 Gambian children was protected against malaria by fortnightly administration of Maloprim (pyrimethamine and dapsone) for 2 years between their 3 and 5 birthdays. A matched cohort of 47 children received placebo. During the year following the termination of prophylaxis there was no increase in the frequency of clinical attacks of malaria in the protected children compared with the control children. Antibody levels to circumsporozoite protein were measured by a radioimmunoassay and that to blood-stage antigens by a variety of techniques including an ELISA to whole blood-stage Plasmodium falciparum antigen, immunofluorescent assays (IFAT) to acetone fixed, glutaraldehyde fixed and unfixed parasites, a merozoite inhibition test and an opsonizing assay. Antibody levels were, in general, lower in protected than in control children and several differences between the two groups were statistically significant. When antibody levels were measured by ELISA and IFAT at the end of the following rainy season, when malaria transmission was intense, those in protected children had increased to comparable levels to those found in control children. Our findings suggest that chemoprophylaxis given for 2 years lowers malaria antibody levels but that it does not interfere with the development of protective immunity.

Pelvic tuberculosis: an uncommon gynaecological problem in Malaysia

Tuberculosis of the genital tract was diagnosed in only 12 patients during the 17 year period from March 1968 to February 1985 at the University Hospital, Kuala Lumpur, which serves as a major referral centre in Malaysia. The incidence was 0.31 per 1000 gynaecological admissions and the peak age incidence was in the age group 26 to 35 years. The surgical management was mainly conservative as infertility was the most frequent mode of presentation (50%). Evidence of previous pulmonary tuberculosis was present in only five cases. Adnexal adhesions were the commonest pelvic finding; the fallopian tubes and endometrium were affected with equal frequency. Positive cultures for Mycobacterium tuberculosis were obtained in only five of the 12 patients. All patients received combination anti-tuberculosis drugs with satisfactory response.

Pulmonary protective mechanisms in human infants

The flow of oral and nasal secretions into the pharynx is a recognized source of pulmonary aspiration during sleep in infants and adults alike. Such aspiration probably accounts for many cases of bacterial pneumonia. In infants, swallowing occurs frequently in sleep, and the rate of swallowing appears to be far greater than that of the sleeping adult. Such swallowing during sleep appears to be the major mechanism whereby oral and nasal secretions are transported to the digestive tract. Certain aspects of those swallows, such as "swallow-breaths" and their coordination with the respiratory cycle, have been documented. A brief period of airway closure is always seen during such nonfeeding swallows. Nonfeeding swallows are usually seen during mixed and obstructive apneic spells in preterm infants. The underlying reflex mechanisms responsible for such swallows during apnea are unclear. During ordinary postfeeding regurgitation, upper airway closure and swallowing occur in close temporal sequence. These events appear to be major mechanisms of airway protection during regurgitation. In certain infants, regurgitation and prolonged apnea often occur simultaneously. The mechanism underlying their association is unclear but may involve laryngeal chemoreceptors.

Interferences with potentiometry of CO2 in the Ektachem 400 Analyzer

We have investigated the Kodak Ektachem 400 Analyzer procedure for CO2 for interferences from benzyl alcohol, benzoic acid, and several compounds structurally similar to benzoic acid. Benzoic acid in plasma, at concentrations found in neonates intoxicated with benzyl alcohol, caused a large increase in the results for CO2, as did substantially above-normal concentrations of certain fatty acids and keto-acids, and toxic concentrations of aspirin. We observed a correlation between increasing benzoic acid concentrations (up to 17 mmol/L) and falsely increasing CO2 values (greater than 47 mmol/L) obtained with the Ektachem Analyzer for samples from a neonate in the intensive-care unit, who was receiving benzyl alcohol-preserved saline solutions. Although the Ektachem CO2 procedure is simple and rapid, and in most cases accurate, questionable results are occasionally encountered, as indicated by a low anion gap or a measured CO2 exceeding that calculated from blood gas measurements. Such results require the use of another method for verification.

Interferences with potentiometry of CO2 in the Ektachem 400 Analyzer

We have investigated the Kodak Ektachem 400 Analyzer procedure for CO2 for interferences from benzyl alcohol, benzoic acid, and several compounds structurally similar to benzoic acid. Benzoic acid in plasma, at concentrations found in neonates intoxicated with benzyl alcohol, caused a large increase in the results for CO2, as did substantially above-normal concentrations of certain fatty acids and keto-acids, and toxic concentrations of aspirin. We observed a correlation between increasing benzoic acid concentrations (up to 17 mmol/L) and falsely increasing CO2 values (greater than 47 mmol/L) obtained with the Ektachem Analyzer for samples from a neonate in the intensive-care unit, who was receiving benzyl alcohol-preserved saline solutions. Although the Ektachem CO2 procedure is simple and rapid, and in most cases accurate, questionable results are occasionally encountered, as indicated by a low anion gap or a measured CO2 exceeding that calculated from blood gas measurements. Such results require the use of another method for verification.

Giant 'cryptococcoma' of the lung

A case is described of cryptococcosis presenting as a large round intrathoracic lesion with superior vena caval obstruction and clubbing of the fingers. The patient was satisfactorily treated by lobectomy under cover of amphotericin B therapy.