HIV prevention strategies and risk of infection: a model-based analysis.

Risk populations for HIV infections tend to neglect condom use, making alternative preventive approaches necessary. Accordingly, we modelled the risk of sexual HIV transmission for condom use vs. use of rapid diagnostic test (RDT) systems with subsequent exclusion of potential sexual partners with a correctly or falsely positive test from unprotected sex with and without the use of HIV pre-exposure prophylaxis (PrEP) in a bio-statistical approach. We combined a previously described model of transmission risk for HIV-exposed individuals with a newly suggested model of risk of HIV exposure for sexually active HIV-negative individuals. The model was adapted for several stages of infection and different strategies of HIV infection prevention.HIV prevention with RDTs can reduce the transmission risk by up to 97% compared with having sex without any prevention and up to 80% compared with condom use. Nevertheless, RDT-based prevention strategies demonstrate a lack of protection in several stages of infection; in particular, RNA-based RDT systems may fail under treatment. RDT-based pre-screening of potential sex partners prior to unprotected sexual contacts substantially reduces HIV transmission risk. Combination of different prevention strategies is advisable for high-risk groups.

Polymorphism of X-linked CD40 ligand gene associated with pulmonary tuberculosis in the Han Chinese population.

Among those developing tuberculosis (TB) after exposure to Mycobacterium tuberculosis, approximately 70% are males. Host genetic variation, particularly immune-related genes on the X chromosome, may contribute to sex-specific differences in TB incidences. To study whether X-linked gene variation is associated with sex-specific presentation of pulmonary TB (pTB), three single-nucleotide polymorphisms (SNPs) of the TLR8, CD40LG and IRAK1 genes on the X chromosome were genotyped in 923 patients and 1033 healthy individuals of the Han Chinese population. Frequencies of the variants were analyzed independently as well as in their combinations. CD40LG rs3092923 and its combined effects with the other two SNPs were associated with an increased risk of pTB only in males. In males, the rs3092923 genotype C/(-) conferred relative protection (odds ratio (OR): 0.52, 95% confidence interval (CI): 0.35-0.78, Pcorr.=0.0045) and the combined effects of three SNPs increased gradually as the number of risk alleles increased (OR: 2.58, 2.83 and 2.96 for one, two and three risk alleles, respectively). For the remaining SNPs, significance was obtained only for the AA genotype of IRAK1 rs3027898 in the combined and female-only analysis. Our results indicate a role of a CD40LG variant and its combined effects with distinct TLR8 and IRAK1 variants in susceptibility to pTB in males.

A general swimming response in exhausted obligate swimming fish.

Marine organisms normally swim at elevated speeds relative to cruising speeds only during strenuous activity, such as predation or escape. We measured swimming speeds of 29 ram ventilating sharks from 10 species and of three Atlantic bluefin tunas immediately after exhaustive exercise (fighting a capture by hook-and-line) and unexpectedly found all individuals exhibited a uniform mechanical response, with swimming speed initially two times higher than the cruising speeds reached approximately 6 h later. We hypothesized that elevated swimming behaviour is a means to increase energetic demand and drive the removal of lactate accumulated during capture via oxidation. To explore this hypothesis, we estimated the mechanical work that must have been spent by an animal to elevate its swim speed and then showed that the amount of lactate that could have been oxidized to fuel it comprises a significant portion of the amount of lactate normally observed in fishes after exhaustive exercise. An estimate for the full energetic cost of the catch-and-release event ensued.

National health insurance coverage and socio-economic status in a rural district of Ghana.

OBJECTIVE: To explore the association between socio-economic status (SES) and health insurance subscription to the Ghanaian National Health Insurance Scheme (NHIS) of residents of the Asante Akim North district of the Ashanti Region, Ghana. METHODS: In the course of a community survey, data on asset variables (e.g. electricity, housing conditions and other variables) and on NHIS subscription were collected on the household level in 99 villages. Using principal components analysis, households were classified into three categories of SES (20% high, 40% middle and 40% low SES). Odds ratios of NHIS subscription were calculated for all SES categories, using the low category as the reference group and adjusting for travelling time to health facilities by public transport. RESULTS: Of the 7223 households surveyed, 38% subscribed to the NHIS, of these 21% were low, 43% middle and 60% high SES households. SES was significantly associated with NHIS subscription (high SES: OR 4.9, 95% CI 4.3-5.7; middle SES: OR 2.5, 95% CI 2.2-2.9; low SES: OR 1, reference group). CONCLUSION: Four years after its introduction, the NHIS has reached subscription rates of 38% in the district surveyed. However, to achieve the aim of assuring universal access to health care facilities for all residents of Ghana, in particular for individuals living under socio-economic constraints, increasing subscription rates are necessary.

A structural variant of the human interferon-gamma gene.

The first structural IFNG variant, G54D (c.287G>A, ss105106770), located in the second exon, was identified.

Effects of food type on diel behaviours of common carp Cyprinus carpio in simulated aquaculture pond conditions.

In order to better understand behaviour patterns of common carp Cyprinus carpio in aquaculture ponds, their diel grazing, swimming, resting and schooling behaviours were observed in six 1 m(2) tanks under simulated pond conditions. Each tank was fertilized to stimulate natural food production before starting experiments, and then stocked with three C. carpio. Fish behaviours were compared among three treatments: (1) tanks with plankton only, (2) tanks with plankton and benthic macroinvertebrates and (3) tanks with plankton, benthic macroinvertebrates and artificial feed. Overall C. carpio grazed more frequently during daytime than at night and exhibited the reverse pattern for non-feeding swimming behaviour. A significant negative relationship (r(2) = 0.99, P < 0.01, n = 48) was observed between total per cent grazing time and total per cent swimming time. Fish dispersed to graze individually during daytime but schooled at night and did not display any agonistic behaviours. Diel variations in the vertical swimming behaviour of C. carpio were related to food types available. In tanks containing plankton only, fish grazed in the water column, whereas when benthic macroinvertebrates were present, they spent more time near the tank bottom. Resting behaviour was only seen in tanks with artificial feed and even then was rare (2-5% of total time). Results suggest that C. carpio growth and feed utilization efficiency in semi-intensive aquaculture systems could be optimized by using a combination of plankton, benthic macroinvertebrates and artificial feed, and feeding fish twice per day (at c. 0730 and c. 1630 hours).

No associations of human pulmonary tuberculosis with Sp110 variants.

BACKGROUND: After a recent report on the role of the Ipr1 gene in mediating innate immunity in a mouse model of Mycobacterium tuberculosis infection, the human Ipr1 homologue, Sp110, was considered a promising candidate for an association study in human tuberculosis. METHODS: In a sample of >1000 sputum positive, HIV negative West African patients with pulmonary tuberculosis and >1000 exposed, apparently healthy controls, we have genotyped 21 Sp110 gene variants that were either available from public databases, including HapMap data, or identified by DNA re-sequencing. RESULTS: No significant differences in the frequencies of any of the 21 variants were observed between patients and controls. This applied also for HapMap tagging variants and the corresponding haplotypes, when including sliding window analyses with three adjacent variants, and when stratifying controls for positivity and negativity according to the results of intradermal tuberculin (purified protein derivative, PPD) skin tests. DNA re-sequencing revealed 13 novel Sp110 variants in the 5'-UTR, exons, and adjacent intronic regions. CONCLUSIONS: Based on the results obtained in this case-control study, the hypothesis that Sp110 variants and haplotypes might be associated with distinct phenotypes of human M tuberculosis infection is doubtful.

Human leukocyte antigens in tuberculosis and leprosy.

Human mycobacterial infections are characterized by a spectrum of clinical and immunological manifestations. Specific human leukocyte antigen (HLA) factors are associated with the subtypes of leprosy that develop and the course of tuberculosis after infection. The identification of protective mycobacterial antigens presented by a broad variety of HLA molecules will have important implications for the design of vaccines.

Pre-treatment with chloroquine and parasite chloroquine resistance in Ghanaian children with severe malaria.

BACKGROUND: Self-medication with anti-malarial drugs is widespread, and chloroquine (CQ) resistance is increasing. The effect of these factors on the incidence and presentation of severe malaria is uncertain. AIM: To investigate subtype of severe malaria, duration of illness, previous CQ treatment and prevalence of Plasmodium falciparum CQ-resistance markers among children presenting with severe malaria to a teaching hospital in Ghana. DESIGN: Prospective clinical study. METHODS: Consecutive patients (n = 189) presenting with severe malaria were examined clinically, and blood was taken for routine haematology and malaria films. Plasma and blood cells were stored and subsequently analysed by ELISA for CQ levels (n = 168) and by PCR and restriction digest for P. falciparum chloroquine resistance transporter gene (pfcrt) mutations (n = 139). RESULTS: Of 47 presenting with cerebral malaria, 21 had severe anaemia and 13 respiratory distress (RDS). Twenty-nine had prostration or RDS alone, 41 severe anaemia with prostration or RDS, and 72 severe anaemia not associated with coma, prostration or RDS. Of the patients studied, 77% had CQ in their plasma, and 88% were carrying P. falciparum with a CQ-resistance genotype. Significant associations were found (i) between the CQ-resistance genotype of parasites and plasma CQ levels, (ii) between the presence of CQ in plasma and the reported duration of illness, and (iii) between the reported duration of illness and the occurrence of severe but otherwise uncomplicated anaemia. DISCUSSION: There was extensive prior CQ use in our patients presenting with severe malaria, and a high prevalence of parasites with the CQ-resistance genotype. CQ resistance in P. falciparum may contribute to the development of severe but otherwise uncomplicated anaemia in this setting.

Vitamin C elevates red blood cell glutathione in healthy adults.

We examined the effect of supplemental ascorbic acid on red blood cell glutathione. Subjects consumed self-selected vitamin C-restricted diets, and, under double-blind conditions, ingested placebo daily for week 1 (baseline), 500 mg L-ascorbate/d for weeks 2-3, 2000 mg L-ascorbate/d for weeks 4-5, and placebo daily for week 6 (withdraw). Mean red blood cell glutathione rose nearly 50% (P < 0.05) after the 500-mg period compared with baseline, and the changes from baseline for individual subjects ranged from +8% to +84%. However, the increases in plasma vitamin C and red blood cell glutathione were not correlated (r = 0.22). At the 2000-mg dosage, mean red blood cell glutathione was not significantly different from the value obtained at the 500-mg dosage. After the placebo-controlled withdraw period, red blood cell glutathione did not differ from baseline. These data indicate that vitamin C supplementation (500 mg/d) maintains reduced glutathione concentrations in blood and improves the overall antioxidant protection capacity of blood.

Direct sequencing of variable HLA gene segments after in vitro amplification and allele separation by temperature-gradient gel electrophoresis.

Previously unrecognized variants of human leukocyte antigens (HLA) are currently being analyzed by in vitro amplification and sequencing of the variable gene segments. In heterozygous individuals, molecular cloning is required to separate the two concomitantly amplified haplotypic gene segments. A method is presented which facilitates the procedure of separating the two haplotypic gene segments by using a temperature-gradient gel electrophoresis (TGGE). The procedure comprises PCR amplification of the variable HLA gene segments, allele separation by TGGE, re-amplification of each of the separated allelic segments, and direct DNA sequencing using the PCR primers.

Liver transplantation for cholangiocarcinoma: results in 207 patients.

BACKGROUND: Because of the high incidence of recurrent tumor, many surgeons have become disenchanted with transplantation as a treatment for cholangiocarcinoma. METHODS: The Cincinnati Transplant Tumor Registry database was used to examine 207 patients who underwent liver transplantation for otherwise unresectable cholangiocarcinoma or cholangiohepatoma. Specific factors evaluated included tumor size, presence of multiple nodules, evidence of tumor spread at surgery, and treatment with adjuvant chemotherapy and/or radiation therapy. Incidentally found tumors were compared to tumors that were known or suspected to be present before transplantation. RESULTS: The 1, 2, and 5-year survival estimates using life table analysis were 72, 48, and 23%. Fifty-one percent of patients had recurrence of their tumors after transplantation and 84% of recurrences occurred within 2 years of transplantation. Survival after recurrence was rarely more than 1 year. Forty-seven percent of recurrences occurred in the allograft and 30% in the lungs. Tumor recurrence, and evidence of tumor spread at the time of surgery, were negative prognostic variables. There were no positive prognostic variables. Patients with incidentally found cholangiocarcinomas did not have improved survival over patients with known or suspected tumors. A small number of patients survived for more than 5 years without recurrence. However, this group had no variable in common that would aid in the selection of similar patients in the future. CONCLUSIONS: Because of the high rate of recurrent tumor and lack of positive prognostic variables, transplantation should seldom be used as a treatment for cholangiocarcinoma. For transplantation to be a viable treatment in the future, more effective adjuvant therapies are necessary.

Hepatitis G virus RNA and hepatitis G virus antibodies in renal transplant recipients: prevalence and risk factors.

BACKGROUND: Hepatitis G virus (HGV/GBV-C) RNA indicating current infection has been frequently isolated from the sera of transplant recipients and other multitransfused individuals. Lifetime exposure to the virus, however, is unknown. We carried out a study to determine the prevalence and risk factors of HGV antibodies and of HGV RNA among renal transplant recipients, and to investigate possible associations between HGV RNA and immunosuppressive treatment. METHODS: HGV RNA was detected by reverse transcriptase-polymerase chain reaction, and HGV antibodies (anti-E2) by a newly developed immunoassay. To assess risk factors for HGV exposure, univariate and multivariate analysis was performed. RESULTS: Of the 221 patients, 14% were HGV RNA positive and 40% had HGV antibodies. Both HGV RNA and anti-HGV were present in only two individuals. Thus, the overall HGV exposure prevalence was 53%. It increased significantly with the number of blood transfusions. In logistic regression, the adjusted HGV exposure prevalence odds ratio was 5.7 (95% confidence interval [CI]: 2.2-15) among patients with > or =10 transfusions (baseline: no transfusions). Other independent risk factors were a longer duration of hemodialysis and a longer time interval since transplantation. HGV viremia was not associated with the type of immunosuppressive treatment. Alanine aminotransferase levels were not significantly increased among HGV RNA-positive patients. CONCLUSIONS: Much higher proportions of renal transplant recipients were exposed to HGV than is suggested by HGV RNA detection alone. The majority of infected individuals apparently eliminate the virus over time. Contaminated blood transfusions have to be regarded as a main risk factor for HGV infection.

A silent mutation in HLA-DPB1*0101 and its evolutionary implications.

A novel HLA-DPB1 allele (DPB1*/A6) has been identified in West Africa, and the occurrence of the recently reported allele DPB1*4001 (DPB1*BRI-5) in Negroid populations has been confirmed DPB1*WA6 differs from DPB1*0101 by a silent nucleotide exchange at codon position 43 only. It constitutes, thereby, a link to DPB1*1101, *1501, and *2601 and suggests and evolutionary relationship with these alleles. Carrying the same silent mutation, DPB1*1101, *1501, and *2601 may, by recombinations, have evolved from DPB1*WA6. An apparently older evolutionary branch arose directly from DPB1*0101 and comprises the closely related alleles DPB1*2701 and DPB1*4001 reported only from individuals of African descent.

Short report: high prevalence and imbalanced age distribution of the Plasmodium falciparum dihydrofolate reductase gene Asn108 mutation in an area of low pyrimethamine usage in Nigeria.

Resistance of Plasmodium falciparum to pyrimethamine is associated with a non-silent point mutation of the parasite dihydrofolate reductase (DHFR) gene (Ser108 --> Asn108). Wide-scale use of antimalarials is thought to contribute to the emergence of drug resistance. In 131 P. falciparum-infected children in rural Nigeria, the frequency of the resistant Asn108 genotype was assessed by enzymatic restriction digestion of polymerase chain reaction-amplified DHFR sequences and compared with residual pyrimethamine blood levels. The prevalence of the Asn108 variant was 41.2%. In 18.3% of the isolates, both the Asn108 and the wild-type alleles were present. In contrast to the high prevalence of resistant genotypes, residual pyrimethamine blood levels were detected in only 4%. Furthermore, age was found to be a determinant of the parasite genotype since the proportion of Asn108 variants decreased with age (P < 0.05). These findings indicate that additional, unidentified factors, rather than selection by residual drug levels alone, might be responsible for the emergence of pyrimethamine-resistant parasite genotypes.

High rate of mixed and subpatent malarial infections in southwest Nigeria.

The rate of malarial parasitemia in children and adults was assessed by microscopy and the polymerase chain reaction in a holoendemic area in Nigeria. A high rate of subpatent Plasmodium falciparum parasitemia (19.6%) was found. Plasmodium malariae and P. ovale infections were common in a rural area (26.1% and 14.8%) but were observed sporadically in individuals from an urban area. Simultaneous infections with P. falciparum, P. malariae, and P. ovale were frequent in the rural area (11.7% triple infections). The rate of triple infections was higher than expected from the prevalences of each species (P < 0.00001). Spleen enlargement was associated with mixed infections of P. falciparum and P. malariae (odds ratio [OR] = 5.9, 95% confidence interval [CI] 3.0-11.7) and less frequently observed in individuals without detectable parasitemia (OR = 0.06, 95% CI = 0.01-0.3). Spleen enlargement and titers of antibodies to schizonts were positively correlated with parasite densities. The results also suggest that in some individuals a long-lasting subpatent parasitemia might occur.

HLA-DP control of human Schistosoma haematobium infection.

The DPA1 and DPB1 alleles of the major histocompatibility complex (MHC) class II were determined in 110 patients and 120 healthy controls of a Gabonese population from an area endemic for Schistosoma haematobium infection. The MHC-DP alleles of the variable second exons and their human leukocyte antigen (HLA) epitopes were correlated with egg excretion, interleukin-4 and interferon-gamma patterns, and bladder abnormalities, as detected by ultrasonography. A methionine at position 11 of the DP alpha molecule (Met-11) and DPA1*0301 were associated with schistosomiasis when compared with controls (phenotypic gene frequencies = 0.791 versus 0.583 and 0.555 versus 0.375, respectively). Met-11 homozygosity occurred more often in patients, whereas healthy controls were more frequently homozygous for an alanine at position 11 (Ala-11). The combination of the DPB1-epitope DEAV (positions 84-87 of the DP beta molecule) and Met-11 positive DPA1 alleles was more frequent in patients than in controls (0.573 versus 0.316). Two years after antischistosomal treatment, the rate of reinfection as examined in 55 of the 110 former patients was higher in DPA1*0301-positive individuals than in those not possessing this allele (P < 0.001). Ala-11 positive individuals showed less frequently ultrasonographic signs of bladder pathology than Ala-11 negative individuals (P < 0.05). Our results suggest a role of MHC-DP elements in the manifestation of disease in S. haematobium infection.

Impact of subpatent multi-species and multi-clonal plasmodial infections on anaemia in children from Nigeria.

Childhood anaemia in sub-Saharan Africa is often caused by Plasmodium falciparum malaria. The influence of subpatent, multi-species and polyclonal infections with malaria parasites on haematological parameters was assessed in 1996/97 in clinically healthy children in Nigeria. Of the 228 children studied, 64% were anaemic by the WHO age-dependent criteria. A univariate analysis of risk factors indicated that the prevalence of anaemia was dependent on the number of Plasmodium species detected by species-specific PCR (P < 0.0001). Furthermore, the prevalence of anaemia increased gradually with the complexity (P < 0.003) as well as with the extent of P. falciparum parasitaemia (P < 0.0001). A logistic regression analysis revealed that individuals with an enlarged spleen tended to be anaemic. The number of Plasmodium species by which an individual was infected was independently associated with anaemia (P < 0.03). ANOVA revealed that the age-corrected values for haemoglobin (Hb) and red blood cells (RBCs) were mainly influenced by the occurrence of mixed infections. Haematological parameters were also influenced by the number of different P. falciparum clones by which an individual was infected. Hb levels and RBC counts were further diminished by additional infections with P. malariae and/or P. ovale. However, the effect of multi-species infections on haematological parameters exceeded that of multi-clonal infections.

Spleen size determined by ultrasound in patients with sickle cell trait, HbAC trait and glucose-6-phosphate-dehydrogenase deficiency in a malaria hyperendemic area (Ashanti Region, Ghana).

The occurrence of enlarged spleens and its age distribution has long been used as a crude measure to estimate malaria endemicity in cross-sectional surveys. Spleen size, however, is influenced by several variables that should be considered if they are observed in a population under study. We hypothesized that spleen indices are dependent on distinct red blood cell polymorphisms. Accordingly, we expected a lower prevalence of splenomegaly among patients with the sickle-cell trait (HbAS), HbAC trait and G6PD deficiency than in patients without red cell disorders, possibly due to the lower incidence of malaria attacks in these individuals. In our survey, however, spleen rates and sizes did not differ significantly between HbAA-, HbAS- and HbAC-positive individuals. Furthermore, enlargement of spleens was found at similar frequencies in persons with and without glucose-6-phosphate-dehydrogenase (G6PD)-deficiency (G6PD-A(-)).

Polymorphisms of transporter associated with antigen processing type 1 (TAP1), proteasome subunit beta type 9 (PSMB9) and their common promoter in African children with different manifestations of malaria.

The distribution of gene variants of the antigen processing proteins transporter associated with antigen processing type 1 (TAP1) and proteasome subunit beta type 9 (PSMB9) and of their shared bidirectional promoter was assessed in children with either mild or severe malaria. The genetic study was performed on samples collected during a longitudinal study on malariometric indices in an area hyperendemic for Plasmodium falciparum malaria in Gabon. The allele frequencies of the genes did not differ between the mild and the severe malaria groups. The distributions of alleles among children with distinct phenotypes of severe malaria were similar. A negative association of hypoglycaemia with the PSMB9 promoter variant PSMB9-R was found (odds ratio 0.01; chi2=12.1; P<0.0005; Pc<0.03). The promoter allele TAP1-446G was associated with hyperparasitaemia and absence of hypoglycaemia. TAP1, PSMB9, and TAP1/PSMB9 promoter alleles were in strong linkage disequilibrium. DNA sequencing of the TAP1/PSMB9 promoter region revealed a previously unrecognized single nucleotide polymorphism 455 bp upstream of the TAP1 transcription start site.