PubMed Health⌕ Search

Biomedical subjects

B L Nahlen

Publications and source records attributed to B L Nahlen.

At least 55 records · Page 3Linked to original sources
PubMed1996

Natural immune response to the C-terminal 19-kilodalton domain of Plasmodium falciparum merozoite surface protein 1.

We have characterized the natural immune responses to the 19-kDa domain of merozoite surface protein 1 in individuals from an area of western Kenya in which malaria is holoendemic. We used the three known natural variant forms of the yeast-expressed recombinant 19-kDa fragment that are referred to as the E-KNG, Q-KNG, and E-TSR antigens. T-cell proliferative responses in individuals older than 15 years and the profile of immunoglobulin G (IgG) antibody isotypes in individuals from 2 to 74 years old were determined. Positive proliferative responses to the Q-KNG antigen were observed for 54% of the individuals, and 37 and 35% of the individuals responded to the E-KNG and E-TSR constructs, respectively. Considerable heterogeneity in the T-cell proliferative responses to these three variant antigens was observed in different individuals, suggesting that the 19-kDa antigen may contain variant-specific T epitopes. Among responses of the different isotypes of the IgG antibody, IgG1 and IgG3 isotype responses were predominant, and the prevalence and levels of the responses increased with age. We also found that a higher level of IgG1 antibody response correlated with lower parasite density among young age groups, suggesting that IgG1 antibody response may play a role in protection against malaria. However, there was no correlation between the IgG3 antibody level and protection. Furthermore, we observed that although the natural antibodies cross-reacted with all three variant 19-kDa antigens, IgG3 antibodies in 12 plasma samples recognized only the E-KNG and Q-KNG constructs and not the E-TSR antigen. This result suggests that the fine specificity of IgG3 antibodies differentiates among variant-specific natural B-cell determinants in the second epidermal growth factor domain (KNG and TSR) of the antigen.

Adolescent↗
PubMed1995

Identification of T and B cell epitopes recognized by humans in the C-terminal 42-kDa domain of the Plasmodium falciparum merozoite surface protein (MSP)-1.

The 42-kDa, C-terminal region of the merozoite surface protein-1 (MSP-1) of Plasmodium falciparum is a putative malaria vaccine candidate Ag. Nine synthetic peptides corresponding to predicted T cell sites of MSP-1 in blocks 15 and 16 and eight overlapping peptides representing the conserved block 17 were used to identify naturally immunogenic epitopes. These peptides were tested for their ability to induce proliferation of PBMC from residents in western Kenya, where malaria transmission is holoendemic. Six peptides (PL145, PL146, PL147, PL148, PL149, and PL150) from blocks 15 and 16 induced a positive proliferative response in > 30% of the individuals tested, and three peptides (PL151, PL152, and PL153) induced a proliferative response in < 25% of the donors. Among these peptides, PL146 was from the highly conserved region, PL150 was from a polymorphic region, and all other peptides were from a dimorphic region of blocks 15 and 16. In block 17, only three peptides, PL99, PL100, and PL103, induced proliferation in 30 to 37% of the volunteers. The rest of the peptides induced a proliferative response in approximately 13 to 25% of the donors. The plasma from these donors widely reacted with different allelic forms of 19-kDa recombinant proteins representing block 17 and recognized at least two linear B epitopes, PL104 and PL97. In summary, this study revealed that a majority of immunodominant T and B epitopes are localized in the conserved or dimorphic regions that are nonpolymorphic in the 42-kDa protein of MSP-1. This study suggests that incorporation of T epitopes from the dimorphic blocks 15 and 16 in a vaccine construct may be useful to ensure Ag-specific memory responses.

Amino Acid Sequence↗
PubMed1995

Influenza immunization for HIV-infected persons in Los Angeles.

We assessed the use of influenza vaccine in a cohort of HIV-infected patients during 1991 and 1992 in Los Angeles County. Influenza vaccination status and clinical and demographic data were obtained from medical records in three different outpatient clinics: a health maintenance organization (HMO), a public clinic and a private medical group. The overall proportion of patients immunized with influenza vaccine was 28%. Patients receiving medical care at the HMO were more likely to receive influenza vaccine (45%) than were patients at the public clinic (25%) or the private facility (13%). Higher immunization levels were also observed among patients with greater numbers of clinic visits for both years studied (p < 0.001). After we controlled for the number of outpatient visits, patients at the HMO and the public clinic were still more likely to receive influenza vaccine in both 1991 (adjusted relative risks 3.2 and 2.1, respectively) and 1992 (adjusted relative risks 1.7 and 1.8) compared with private clinic patients. Health-care providers should increase efforts to provide influenza vaccine to HIV-infected patients.

Female↗
PubMed1994

Health insurance coverage among persons with AIDS: results from a multistate surveillance project.

To determine factors associated with health insurance coverage among persons with acquired immunodeficiency syndrome (AIDS), we interviewed 1958 persons 18 years of age or older who were reported to have AIDS in 11 states and cities. Overall, 25% had no insurance, 55% had public insurance, and 20% had private insurance. Factors associated with lack of insurance varied by current employment status. Employed persons with an annual household income of less than $10,000 were 3.6 times more likely to lack insurance than employed persons with a higher income. Unemployed persons diagnosed with AIDS for less than 1 year were two times more likely to lack health insurance than unemployed persons diagnosed for a longer time. Making insurance available to persons identified as most likely to lack insurance should improve access to care for persons with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1993

HIV wasting syndrome in the United States.

OBJECTIVE: To describe the characteristics of individuals > or = 13 years of age with HIV wasting syndrome in the United States and US territories. DESIGN: Retrospective review of national AIDS case surveillance data. METHODS: Data for the 147,225 individuals with AIDS reported to the Centers for Disease Control from 1 September 1987 to 31 August 1991 were reviewed. The frequency of HIV wasting syndrome and its association with demographic and exposure category variables and with other AIDS-indicator diseases were assessed. RESULTS: A total of 10,525 (7.1%) had wasting syndrome as the only AIDS-indicator condition, and 15,726 (10.7%) had wasting syndrome plus at least one other AIDS-indicator condition. Patients with wasting syndrome as the only AIDS diagnosis were more likely to be female, to be black or Hispanic, and to have a mode of HIV exposure reported as injecting drug use, heterosexual contact, or transfusion/hemophilia. The proportion of AIDS patients reported with wasting syndrome varied by geographic distribution, ranging from 11% in the northeastern United States to 47% in Puerto Rico. The association between HIV wasting syndrome and Hispanic ethnicity was due to the much higher prevalence of wasting syndrome reported in Puerto Rican AIDS patients. The other AIDS-indicator conditions most strongly associated with wasting syndrome were isosporiasis, pulmonary candidiasis, esophageal candidiasis, HIV encephalopathy, chronic mucocutaneous herpes simplex, and coccidioidomycosis. CONCLUSIONS: The association between HIV wasting syndrome and injecting drug use, and the significant racial/ethnic and geographic differences in prevalence of this AIDS diagnosis may reflect differences in diagnostic and reporting practices and/or access to medical care.

AIDS-Related Opportunistic Infections↗
PubMed1990

Transmission of Plasmodium vivax malaria in San Diego County, California, 1986.

Between 18 June and 20 September 1986, 28 cases of Plasmodium vivax malaria were documented in Carlsbad, California, a coastal town north of San Diego. Malaria occurred in 1 local resident who had no risk factors, a second local resident who had traveled to a malarious area 9 months earlier, and 26 Mexican migrant workers (MWs). Among the 28 cases, 27 lived in a square mile marshy area where Anopheles hermsi, a newly described American species of the Anopheles maculipennis group, was known to be breeding. An investigation of MWs residing in the affected area was done to determine the extent of the outbreak and to identify risk factors for acquiring malaria. We interviewed and drew blood from 304 healthy MWs and 17 (65%) of the MWs with malaria. Fluorescent antibody titers to P. vivax greater than or equal to 1:256 occurred in 14 (82%) of the 17 MWs with malaria tested and 9 (3%) of the healthy MWs. The principal risk factor identified for contracting malaria was sleeping outside on a hillside adjacent to the marshy area. Malaria in a local resident with no malaria risk factors and the clustering in time and place of 26 cases suggest that P. vivax malaria was introduced and local transmission was sustained through several generations, producing the largest outbreak of introduced malaria in the United States since 1952.

Adolescent↗
PubMed1990

Sensitivity of Plasmodium falciparum to chloroquine and sulfadoxine/pyrimethamine in Nigerian children.

The in vivo sensitivity of Plasmodium falciparum to chloroquine and sulfadoxine/pyrimethamine was evaluated in children under 5 years of age in two areas of southern Nigeria in 1987. A modification of the WHO Standard Field and Extended Tests (in vivo) was used, with follow-up on days, 2, 3, 7, and 14 after treatment with 25 mg chloroquine per kg body weight given over 3 days, or with standard doses of sulfadoxine/pyrimethamine. Clinical and parasitological evaluations were performed. At Igbo Ora, in Oyo State, where by day 7 chloroquine was clinically successful in 94.4% of 36 children and sulfadoxine/pyrimethamine in 91.7% of 36 children, there were no parasitological failures in either treatment group. Fever regressed significantly more rapidly with chloroquine than with sulfadoxine/pyrimethamine. At Oban, in Cross River State, initial parasite densities decreased markedly with the chloroquine regimen but 63.6% of 44 children were parasitological failures on days 3, 7, or 14; and all of the 26 children who failed parasitologically and completed follow-up were successfully treated with sulfadoxine/pyrimethamine. By day 7, clinical success was demonstrated for 77.3% of the children treated with chloroquine. The in vitro sensitivity to chloroquine, quinine, and mefloquine at Igbo Ora indicated that isolates of P. falciparum were sensitive to chloroquine and quinine, but had reduced sensitivity to mefloquine. Because of its continued clinical efficacy, chloroquine remains the recommended treatment for children with uncomplicated malaria in Nigeria. Health providers are, however, encouraged to maintain supplies of sulfadoxine/pyrimethamine as an alternative and to refer patients promptly if necessary.

Animals↗
PubMed1989

Lack of efficacy of pyrimethamine prophylaxis in pregnant Nigerian women.

To evaluate the efficacy of pyrimethamine on the blood stage (suppressive prophylaxis) and liver stage (causal prophylaxis) of Plasmodium falciparum in pregnant women, in vivo and in vitro field studies were conducted in Ilorin, Nigeria, from Jan 1 to June 30, 1988. For pregnant women with P falciparum infections who received 25 mg of pyrimethamine weekly for suppressive prophylaxis, 67% (59/88) of in vivo and 60% (6/10) of in vitro tests showed pyrimethamine resistance. A second group of parasitaemic and parasite-free pregnant women was enrolled to evaluate the efficacy of pyrimethamine as a primary tissue schizonticide; after receiving a curative dose of chloroquine (25 mg/kg), half the women were given 25 mg of pyrimethamine weekly and half received no prophylaxis. Parasitologic failure rates did not differ between the pyrimethamine-treated (8/34) and the control (11/37) groups during the 16-week follow-up. Thus, pyrimethamine is not effective for suppressive or causal prophylaxis in pregnant women in Ilorin.

Adolescent↗
PubMed1989

Adaptations of the Saker-Solomons test: simple, reliable colorimetric field assays for chloroquine and its metabolites in urine.

Two field-adapted colorimetric methods for measuring the antimalarial drug chloroquine in urine are described. Both are modifications of the method of Saker and Solomons for screening urine for phencyclidine and other drugs of abuse, using the colour reagent tetrabromophenolphthalein ethyl ester. One method is semiquantitative, detecting the presence of chloroquine (Cq) and its metabolites in urine with a 1 microgram/ml detection limit; it is more sensitive and reliable than the commonly used Dill-Glazko method and is as easy to apply in the field. The second method uses a hand-held, battery-operated filter photometer to quantify Cq and its metabolites with a 2 microgram/ml detection limit and a linear range up to 8 micrograms/ml. The first method was validated in the field using a published quantitative colorimetric method and samples from a malaria study in Nigeria. The second method was validated in the laboratory against high-performance liquid chromatographic results on paired samples from the Nigerian study. Both methods may be used in remote locations where malaria is endemic and no electricity is available.

Child, Preschool↗
PubMed1987

Field-adapted method for high-performance thin-layer chromatographic detection and estimation of chloroquine and desethylchloroquine in urine.

A high-performance thin-layer chromatographic (HPTLC) method which can be used in remote field locations lacking electricity has been developed for selective and sensitive detection and estimation of chloroquine (Cq), desethylchloroquine (DECq) and two other antimalarial compounds in urine. The method requires a single extraction step and has a detection limit of 0.25 micrograms/ml for both Cq and DECq. The HPTLC method was coupled with a colorimetric field assay for Cq and metabolites in urine and a field-interfaced, laboratory-based, high-performance liquid chromatographic assay of Cq and DECq in finger-stick blood to survey antimalarial drug use practices in Esmeraldas Province in northwestern Ecuador. Fourteen of 66 patients from whom urine samples were obtained were found to have detectable Cq and DECq. Results of the three assays are compared for these individuals, and the role of the HPTLC method in field studies is assessed.

Child, Preschool↗
PubMedDate not supplied

Reassessment of blood donor selection criteria for United States travelers to malarious areas.

In the United States (US), travelers who have had malaria or who have taken antimalarial chemoprophylaxis are deferred as blood donors for 3 years to prevent transfusion-transmitted malaria. To assess the impact of shortening this 3-year exclusion period, national malaria surveillance data from 1972 to 1988 were reviewed. The average annual rate of transfusion-transmitted malaria is 0.25 cases per million units of blood collected. Of 45 reported cases, 38 percent were caused by Plasmodium malariae, 29 percent by P. falciparum, 24 percent by P. vivax, and 9 percent by P. ovale. Thirty-two donors were implicated in 34 cases of transfusion-transmitted malaria. Of 30 implicated donors whose native country was identified, 23 (77%) were foreign nationals and 7 (23%) were from the US. In a review of all imported malaria cases by species and by interval between date of entry and onset of illness, 98 percent of P. falciparum, 86 percent of P. malariae, 76 percent of P. vivax, and 74 percent of P. ovale infections became symptomatic within 6 months of the patient's arrival in the US, regardless of the use of prophylaxis. Shortening to 6 months the donor exclusion period for US travelers to malarious areas would result in a minimum of 70,000 additional blood donors' being made available, with a maximum annual increase of 0.03 additional cases of transfusion-transmitted malaria. The potential benefit of bringing healthy travelers back into the donor pool after a shorter period of exclusion merits consideration by the blood banking industry.

Adult↗
PubMedDate not supplied

Cost-effectiveness of sulfadoxine-pyrimethamine for the prevention of malaria-associated low birth weight.

Prevention of placental malaria through administration of antimalarial medications to pregnant women in disease-endemic areas decreases the risk of delivery of low birth weight (LBW) infants. In areas of high Plasmodium falciparum transmission, two intermittent presumptive treatment doses of sulfadoxine-pyrimethamine (SP) during the second and third trimesters of pregnancy are effective in decreasing the prevalence of placental malaria in human immunodeficiency virus (HlV)-negative women, while HIV-positive women may require a monthly SP regimen to reduce their prevalence of placental parasitemia. A decision-analysis model was used to compare the cost-effectiveness of three different presumptive SP treatment regimens with febrile case management with SP in terms of incremental cost per case LBW prevented. Factors considered included HIV seroprevalence, placental malaria prevalence, LBW incidence, the cost of SP, medical care for LBW infants, and HIV testing. For a hypothetical cohort of 10,000 pregnant women, the monthly SP regimen would always be the most effective strategy for reducing LBW associated with malaria. The two-dose SP and monthly SP regimens would prevent 172 and 229 cases of LBW, respectively, compared with the case management approach. At HIV seroprevalence rates greater than 10%, the monthly SP regimen is the least expensive strategy. At HIV seroprevalence rates less than 10%, the two-dose SP regimen would be the less expensive option. When only antenatal clinic costs are considered, the two-dose and monthly SP strategies cost US $11 and $14, respectively, well within the range considered cost effective. Presumptive treatment regimens to prevent LBW associated with malaria and the subsequent increased risk of mortality during the first year of life are effective and cost effective strategies in areas with both elevated HIV prevalence and malaria transmission rates.

Adult↗
PubMedDate not supplied

All-cause mortality among young children in western Kenya. VI: the Asembo Bay Cohort Project.

Although all-cause mortality has been used as an indicator of the health status of childhood populations, such data are sparse for most rural areas of sub-Saharan Africa, particularly community-based estimates of infant mortality rates. The longitudinal follow-up of more than 1,500 children enrolled at birth into the Asembo Bay Cohort Project (ABCP) in western Kenya between 1992 and 1996 has provided a fixed birth cohort for estimating all-cause mortality over the first 5 yr of life. We surveyed mothers and guardians of cohort children in early 1999 to determine survival status. A total of 1,260 households were surveyed to determine the survival status of 1,556 live births (99.2% of original cohort, n = 1,570). Most mothers (66%) still resided but 27.5% had migrated, and 5.5% had died. In early 1999, the overall cumulative incidence of all-cause mortality for the entire 1992-1996 birth cohort was 26.5% (95% confidence interval, 24.1-28.9%). Neonatal and infant mortality were 32 and 176 per 1,000 live births, respectively. These community-based estimates of mortality in the ABCP area are substantially higher than for Kenya overall (nationally, infant mortality is 75 per 1,000 live births). The results provide a baseline description of all-cause mortality among children in an area with intense Plasmodium falciparum transmission and will be useful in future efforts to monitor changes in death rates attributable to control programs for specific diseases (e.g., malaria and HIV/AIDS) in Africa.

Adolescent↗