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Biomedical subjects

B J Ward

Publications and source records attributed to B J Ward.

At least 19 recordsLinked to original sources
PubMed2007

HIV-1 and HIV-2 prevalence and associated risk factors among postnatal women in Harare, Zimbabwe.

Studies of antenatal women form the predominant source of data on HIV-1 prevalence in Africa. Identifying factors associated with prevalent HIV is important in targeting diagnostic services and care. Between November 1997 and January 2000, 14,110 postnatal women from Harare, Zimbabwe were tested by ELISAs reactive to both HIV-1 and HIV-2; a subset of positive samples was confirmed with assays specific for HIV-1 and HIV-2. Baseline characteristics were elicited and modelled to identify risk factors for prevalent HIV infection. HIV-1 and HIV-2 prevalences were 32.0% (95% CI 31.2-32.8) and 1.3% (95% CI 1.1-1.5), respectively; 4% of HIV-1-positive and 99% of HIV-2-positive women were co-infected. HIV-1 prevalence increased from 0% among 14-year-olds to >45% among women aged 29-31 years, then fell to <20% among those aged>40 years. In multivariate analyses, prevalence increased with parity, was lower in married women than in single women, divorcees and widows, and higher in women with the lowest incomes and those professing no religion. Adjusted HIV-1 prevalence increased during 1998 and decreased during 1999. Age modified the effects of parity, home ownership and parental education. Among older women, prevalence was greater for women who were not homeowners. Among younger women, prevalence increased with parity and low parental education. None of these factors distinguished women co-infected with HIV-2 from those infected with HIV-1 alone. Prevalent HIV-1 infection is associated with financial insecurity and weak psychosocial support. The ZVITAMBO study apparently spanned the peak of the HIV-1 epidemic among reproductive women in Harare.

Adolescent↗
PubMed2006

Field evaluation of four novel enzyme immunoassays for Chagas' disease in Venezuela blood banks: comparison of assays using fixed-epimastigotes, fixed-trypomastigotes or trypomastigote excreted-secreted antigens from two Trypanosoma cruzi strains.

Many serological tests have been developed for the diagnosis of Chagas' disease, but few have been subjected to a rigorous field evaluation. We have recently described several novel enzyme immunoassays (EIAs) based on fixed-whole organisms or trypomastigote excretory-secretory antigens (TESA) from different Trypanosoma cruzi strains (Tulahuen or Brazil). This study evaluated the most promising of these novel assays (e.g. fixed-epimastigotes, fixed-trypomastigotes, TESA Brazil and TESA Tulahuen antigens) in a field study of Venezuelan blood bank specimens. The assays were tested in an operator-blinded fashion using 2038 blood bank samples obtained from low and high T.cruzi prevalence regions of Venezuela (n= 1050 and n= 988 from Bolivar and Portuguesa states, respectively). Based on National Laboratory for Chagas Immunodiagnosis (NLCI) 'gold standard' results, all novel EIAs were superior to the commercial kit currently used in Venezuela, achieving 100% sensitivity and >99% specificity at optimal cut-off values. The novel assays identified seven false-negative samples compared with the routine screening performed by the Venezuelan blood bank although two samples were also misclassified as positive. Minor differences in the performance of the four novel assays were observed at lower arbitrary cut-off values. This study confirms the potential utility of both the fixed-organism and the TESA-based assays in the diagnosis of T.cruzi infection.

Adolescent↗
PubMed2005

Randomized, double-blind clinical trial of topical imiquimod 5% with parenteral meglumine antimoniate in the treatment of cutaneous leishmaniasis in Peru.

BACKGROUND: Current treatments for cutaneous leishmaniasis are limited by their toxicity, high cost, and discomfort and the emergence of drug resistance. New approaches, including combination therapies, are urgently needed. We performed a double-blind, randomized trial of therapy with parenteral antimony plus topical imiquimod, an innate immune-response modulator, versus therapy with antimony alone, in subjects with cutaneous leishmaniasis for whom an initial course of antimony therapy had failed. METHODS: Forty subjects with clinical resistance to antimony were recruited in Lima, Peru, between February 2001 and December 2002. All subjects received meglumine antimoniate (20 mg/kg/day im or iv) and were randomized to receive either topical imiquimod 5% cream (Aldara; 3M Pharmaceuticals) or vehicle control every other day for 20 days. Lesions and adverse events were evaluated during treatment and at 1, 2, 3, 6, and 12 months after the treatment period. RESULTS: The mean number of lesions was 1.2 per person; 71% of the lesions were facial and 76% were ulcerative. There were no major differences between the groups, and all but 2 subjects completed therapy. Mild adverse events were reported by 73% of the subjects, but only erythema occurred more commonly in the imiquimod group (P < or = .02). Lesions resolved more rapidly in the imiquimod group: 50% of the imiquimod group achieved cure at 1 month after the treatment period versus 15% of the vehicle cream group (P < or = .02); 61% of the imiquimod group at 2 months versus 25% of the vehicle cream group (P < or = .03); and 72% of the imiquimod group at 3 months versus 35% of the vehicle cream group (P < or = .02). Residual scarring in the imiquimod group was less prominent than in the vehicle cream group. CONCLUSIONS: Combined antimony plus imiquimod treatment was well tolerated, accelerated healing of lesions, and improved scar quality. This therapy may have particular advantages for subjects with facial lesions.

Adjuvants, Immunologic↗
PubMed2004

Measles vaccination in the presence of maternal antibodies primes for a balanced humoral and cellular response to revaccination.

Early or low dose antigen exposure can prime the immune system for subsequent responses; the so-called "prime-boost" effect. In the context of a Sudanese measles vaccine trial, we assessed whether or not such early exposure could influence the response to revaccination. Children received either Connaught high titer vaccine (CN: n = 53; 10(4.7)pfu) or meningococcal A + C vaccine as a placebo (MEN: n = 58) at 5 months of age. At 9 months of age, all received standard titer Schwarz vaccine (SCH: 10(3.9)pfu). Neutralizing antibodies were measured before initial vaccination and at 9 months of age (plaque reduction neutralization assay (PRN)) and again at 5 years of age (syncytium inhibition assay (SIA)). Lymphoproliferative responses to measles virus (MV) antigens were evaluated at 5 years of age. Eleven of the 53 CN-SCH children (21%) had sub-protective neutralizing antibody titers prior to revaccination (log PRN 1.5 +/- 0.03 versus 2.9 +/- 0.07 in the remaining 42 children; P < 0.004). Maternal antibody titers at the time of initial vaccination in these 11 were high (PRN 2.44 +/- 0.12 versus 1.9 +/- 0.04; P < 0.0001). At 5 years of age, neutralizing antibodies were comparable in the 11 CN-SCH poor responders (log SIA 2.1 +/- 0.09), the remaining CN-SCH children (2.2 +/- 0.06) and the MEN-SCH group vaccinated only once at 9 months of age (2.25 +/- 0.06). In contrast, 7/11 of the CN-SCH poor responders (64%) had stimulation indices (SI) > 3 in response to MV antigens at 5 years of age (SI 3.1 +/- 0.6) compared with only 14% in the remaining children of the CN-SCH group (2.0 +/- 0.3; P = 0.05) and 8% in the MEN-SCH group (1.4 +/- 0.2; P < 0.0003). These data suggest that early measles vaccination in the presence of maternal antibodies can sometimes prime for a balanced humoral and cellular immune response to subsequent revaccination.

Age Factors↗
PubMed2001

Intestinal amebiasis: a diagnosis not to be missed.

Entamoeba histolytica is a well-recognized cause of infectious colitis and disseminated amebic abscesses. Most prevalent in the tropics and subtropics, E. histolytica infections may also occur in the developed world. We describe a case of a North American traveler with intestinal amebiasis, a diagnosis first made by colonic biopsy. We review the available diagnostic tools and the role of the surgical pathologist in the detection of this infection.

Adult↗
PubMed2001

Wheat germ supplement reduces cyst and trophozoite passage in people with giardiasis.

The protozoan parasite Giardia lamblia is a major cause of waterborne enteric disease worldwide. Lectins are proteins that bind to carbohydrate (sugar) moieties. Potential targets for lectins are found on the surface of most single-celled organisms. Modest concentrations of wheat germ agglutinin (WGA) have been shown to inhibit G. lamblia excystation and trophozoite growth in vitro and can reduce cyst passage in mice infected with the closely related protozoan parasite, G. muris. Commercial preparations of wheat germ (WG) contain 13-53 microg of WGA per gram. We performed a double-masked, placebo-controlled study of dietary supplementation with WG in 63 subjects with giardiasis in Montreal and Lima (25 asymptomatic patients passing cysts; 38 patients with symptoms). Asymptomatic subjects received WG (2 g, 3 times a day) or placebo (cornstarch, 2 g, 3 times a day) for 10 days, followed by metronidazole (250 mg 3 times a day) for 7 days. Symptomatic subjects received metronidazole (250 mg 3 times a day) plus either WG or placebo for 7 days. Stool specimens were collected every day (Montreal) or every other day (Lima) for 10 days and on Day 35 for microscopic examination and coproantigen determination. Subjects kept a diary of symptoms for 10 days after recruitment. In asymptomatic subjects, both cyst passage and coproantigen levels were reduced by approximately 50% in those taking WG compared with the placebo group (P < 0.01 and P = 0.06, respectively). In symptomatic subjects, cyst passage and coproantigen levels fell precipitously in response to metronidazole therapy, and there were no clinically important differences between those receiving supplemental WG or placebo. However, symptoms appear to have resolved more rapidly in the subjects taking WG in addition to metronidazole. The WG supplement was well tolerated in both symptomatic and asymptomatic subjects. These data suggest that components of WG, possibly WGA, either alone or in combination with antiprotozoal agents, can influence the course of human giardiasis.

Adult↗
PubMed2001

Immune response to measles vaccine in Peruvian children.

OBJECTIVE: To evaluate the immune response in Peruvian children following measles vaccination. METHODS: Fifty-five Peruvian children received Schwarz measles vaccine (about 10(3) plaque forming units) at about 9 months of age. Blood samples were taken before vaccination, then twice after vaccination: one sample at between 1 and 4 weeks after vaccination and the final sample 3 months post vaccination for evaluation of immune cell phenotype and lymphoproliferative responses to measles and non-measles antigens. Measles-specific antibodies were measured by plaque reduction neutralization. FINDINGS: The humoral response developed rapidly after vaccination; only 4 of the 55 children (7%) had plaque reduction neutralization titres <200 mlU/ml 3 months after vaccination. However, only 8 out of 35 children tested (23%) had lymphoproliferative responses to measles antigens 3-4 weeks after vaccination. Children with poor lymphoproliferative responses to measles antigens had readily detectable lymphoproliferative responses to other antigens. Flow cytometric analysis of peripheral blood mononuclear cells revealed diffuse immune system activation at the time of vaccination in most children. The capacity to mount a lymphoproliferative response to measles antigens was associated with expression of CD45RO on CD4+ T-cells. CONCLUSION: The 55 Peruvian children had excellent antibody responses after measles vaccination, but only 23% (8 out of 35) generated detectable lymphoproliferative responses to measles antigens (compared with 55-67% in children in the industrialized world). This difference may contribute to the less than uniform success of measles vaccination programmes in the developing world.

Antibodies, Viral↗
PubMed2000

Development and durability of measles antigen-specific lymphoproliferative response after MMR vaccination.

The correlates of long-term protection from measles infection are poorly understood. We followed the development of measles-specific antibody and lymphoproliferative (LP) responses in 60 children for 6 months after MMR vaccination. Prevaccine plaque reduction neutralization antibody (PRN Ab) values were low (mean+/-SEM 9.9+/-1. 1). Ninety-three percent (56/60) had excellent PRN values at 6 months (PRN 1816+/-207). Prevaccine LP activity was also low (stimulation index (SI)=1.4+/-0.1) but increased rapidly (SI 10. 7+/-4.5 at 2-3 weeks; p<0.05). However, only 61% (37/60) of the children had both significant cellular and antibody responses (SI>/=3 and PRN>/=120: Ab(hi)CMI(hi)). One child had a strong LP response (SI=6.7) despite little antibody production (PRN=19 at 6 months: Ab(lo)CMI(hi)). We also conducted a cross-sectional study in a separate group of 87 children 5-13 years after MMR vaccination. PRN values >/=120 were present in most children at 5-8 (n=28) and 9-13 years (n=59) after vaccination (PRN 550+/-120 and 360+/-60, respectively) but a significant minority had either undetected or 'subprotective' values (29 and 34%, respectively). LP responses (SI>/=3) were detectable in 19/28 (66%) and 36/59 (56%) of the children 5-8 and 9-13 years after vaccination (SI 11.4+/-2.4 and 7. 75+/-1.9, respectively). Almost two thirds (18/28) of the children in the cross-sectional study with low or absent antibody titers (PRN 41+/-6) had strong LP responses to measles antigens (SI 6.8+/-1.3). These data suggest that LP responses may be better sustained than antibody titers in some children. The susceptibility of Ab(lo)CMI(hi) children to infection and the value of the early LP response for predicting the durability of immunity remain to be determined.

Adolescent↗
PubMed2000

Contraction in cardiac endothelial cells contributes to changes in capillary dimensions following ischaemia and reperfusion.

OBJECTIVE: Ischaemia followed by reperfusion brings about a reduction in cardiac capillary cross-sectional dimensions which is consistent with constriction. The aim of this study was to test the hypothesis that the reduction in cardiac capillary dimensions that occurs in ischaemia and reperfusion is caused by endothelial cell contraction and that modulating the endothelial cell contractile apparatus reduces microvascular reperfusion injury. METHODS: In isolated rat hearts we used phalloidin to stabilise the endothelial actin filaments in order to prevent the dimensional changes during ischaemia. The changes in endothelial cell dimensions were quantified by measuring whole capillary and luminal cross-sectional areas, abluminal and luminal membrane lengths. We have also used resin casts of the coronary vasculature coupled with scanning electron microscopy to examine the structural changes along the length of the capillaries in ischaemia-reperfusion. RESULTS: We found that the reduction in capillary dimensions was prevented by the addition of phalloidin and, in the resin casts, that ischaemia-reperfusion cause focal narrowings along the capillaries which are consistent with constriction. CONCLUSIONS: (1) The endothelial contractile apparatus is involved in the reduction in cross-sectional dimensions. (2) This implies that the capillary bed may have a greater role in the local control of flow than was previously thought and that modulation of the actomyosin contractile system in cardiac capillary endothelial cells may be useful in reducing 'no reflow' injury which results from reperfusion.

Analysis of Variance↗
PubMed2000

Rubella susceptibility predicts measles susceptibility: implications for postpartum immunization.

Measles and mumps antibody titers were measured in 262 pregnant women who were either positive (n=128) or negative (n=134) for rubella antibodies. Susceptibility to measles and mumps was detected in 4.6% (12/262) and 7.6% (14/184) of the women, respectively. Of the rubella-susceptible group, 8.2% were also measles susceptible, whereas only 0.8% of the rubella-immune women were measles susceptible. Susceptibility to mumps was evenly divided between rubella-susceptible (7.8%) and rubella-immune (7.4%) groups.

Adult↗
PubMed2000

Performance of indirect immunoglobulin M (IgM) serology tests and IgM capture assays for laboratory diagnosis of measles.

As progress is made toward elimination of measles, the laboratory confirmation of measles becomes increasingly important. However, both false-positive and false-negative results can occur with the routinely used indirect measles immunoglobulin M (IgM) serology tests. The measles IgM capture assay is considered to be more specific, and therefore, its use is indicated for confirmatory testing, but its relative performance has not been fully assessed. Four commercial indirect measles IgM serology test kits (the Behring, Clark, Gull, and PanBio assays) and a commercial IgM capture assay (the Light Diagnostics assay) were evaluated for their abilities to detect measles virus-specific IgM antibody with a total of 308 serum samples from patients involved in a measles outbreak and with confirmed cases of measles and 454 samples from subjects without measles. The Centers for Disease Control and Prevention (CDC) IgM capture assay was also used in a part of the evaluation. Among the indirect assays, the overall sensitivities ranged from 82.8% (Clark assay) to 88.6% (Behring assay) and specificity ranged from 86.6% (PanBio assay) to 99.6% (Gull assay). These rates were 92.2 and 86. 6%, respectively, for the Light Diagnostics capture assay and 87.0 and 94.8%, respectively, for the CDC capture assay. While the Light Diagnostics capture assay had the best detection rate (80%) with the acute-phase samples compared with those for the rest of the tests (CDC capture assay, 77%; Behring assay, 70%; Gull assay, 69%; PanBio assay, 58%; and Clark assay, 57%), all tests showed a significantly improved sensitivity in the range of 92% (Clark and PanBio assays) to 97% (Light Diagnostics and CDC capture assays) with the convalescent-phase samples, as expected. The best seropositivity rates (in the range of 92 to 100%) were observed with samples collected 6 to 14 days after the onset of symptoms. The Gull assay showed the highest positive predictive value (99.6%), followed by the Behring assay (97.8%) and the CDC capture assay (96.1%). Overall, the Gull and Behring assays were found to be as good as or better than the capture assays. In conclusion, laboratory diagnosis of measles based on IgM serology varies depending on the timing of specimen collection and the test used, and the case for the use of the IgM capture assay as the confirmatory test appears to be uncertain.

Antibodies, Viral↗
PubMed2000

Vaccine adverse events in the new millennium: is there reason for concern?

As more and more infectious agents become targets for immunization programmes, the spectrum of adverse events linked to vaccines has been widening. Although some of these links are tenuous, relatively little is known about the immunopathogenesis of even the best characterized vaccine-associated adverse events (VAAEs). The range of possible use of active immunization is rapidly expanding to include vaccines against infectious diseases that require cellular responses to provide protection (e.g. tuberculosis, herpes viral infections), therapeutic vaccines for chronic infections (e.g. human immunodeficiency virus (HIV) infection, viral hepatitis B and C), and vaccines against non-infectious conditions (e.g. cancer, autoimmune diseases). Less virulent pathogens (e.g. varicella, rotavirus in the developed world) are also beginning to be targeted, and vaccine use is being justified in terms of societal and parental "costs" rather than in straightforward morbidity and mortality costs. In the developed world the paediatric immunization schedule is becoming crowded, with pressure to administer increasing numbers of antigens simultaneously in ever simpler forms (e.g. subcomponent, peptide, and DNA vaccines). This trend, while attractive in many ways, brings hypothetical risks (e.g. genetic restriction, narrowed shield of protection, and loss of randomness), which will need to be evaluated and monitored. The available epidemiological and laboratory tools to address the issues outlined above are somewhat limited. As immunological and genetic tools improve in the years ahead, it is likely that we shall be able to explain the immunopathogenesis of many VAAEs and perhaps even anticipate and avoid some of them. However, this will only happen if the human and financial resources needed for monitoring and studying vaccine safety stay in step with the accelerating pace of vaccine development. Failure to make such a commitment would put all immunization programmes at risk.

Adverse Drug Reaction Reporting Systems↗
PubMed2000

Trypanosoma cruzi infection of squirrel monkeys: comparison of blood smear examination, commercial enzyme-linked immunosorbent assay, and polymerase chain reaction analysis as screening tests for evaluation of monkey-related injuries.

BACKGROUND AND PURPOSE: Wild-caught New World monkeys (NWM) from Central or South America are often infected with Trypanosoma species, including T. cruzi. In humans, T. cruzi causes Chagas' disease. Even in closed monkey colonies, T. cruzi can be propagated by blood-to-blood exposure, sexual activity, and transplacental transmission. Animal handlers and laboratory staff who deal with blood and tissues from infected NWM are at riskfor acquiring Chagas' disease via accidental exposure. METHODS: We screened 162 blood samples from wild-caught Saimiri sp. monkeys for Trypanosoma species infections by use of blood smear examination, ELISA, and polymerase chain reaction (PCR) analysis. Blood samples from 19 employees with recent history of monkey-associated injuries also were tested. RESULTS: Six percent (10/162) of the monkey samples were T. cruzi positive on the basis of blood smear examination results, 10.4% (17/162) were positive by ELISA results, and 26.5% (43/162) were positive by PCR results. Other organisms identified by PCR analysis included T. rangeli in two animals, Plasmodium spp. in two animals (P. malariae confirmed by PCR results) and microfilariae in one animal (morphologically, Mansonella perstans). Evidence of trypanosome infection was not found in the 19 employee samples on the basis of results of any of the three aforementioned tests. CONCLUSIONS: Close attention must be paid to worker safety where wild-caught NWM are used. The PCR analysis has a clear advantage over conventional techniques (ELISA, blood smear) for screening NWM for trypanosome infections during quarantine and after employee injury.

Animal Husbandry↗
PubMed1999

Measurement of measles virus-specific neutralizing antibodies: evaluation of the syncytium inhibition assay in comparison with the plaque reduction neutralization test.

Plaque reduction neutralization (PRN) is the "gold-standard" for the measurement of measles-specific neutralizing antibodies. However, it is a complicated assay and tends to be operator-dependent. It has been suggested that the simpler syncytium inhibition assay (SIA) can give results comparable to the PRN test. We compared these two assays using 594 serum or plasma samples obtained from children at various times after natural infection, primary measles immunization, and measles revaccination. The results of the two assays correlated well overall (r = .86; p < 0.0001). The strain of challenge virus (wild-type versus vaccine strain) did not significantly influence SIA titers and the assay performed equally well with serum and plasma. PRN titers > or = 120 and > 800 are thought to indicate protection against clinical illness and infection respectively. The equivalent SIA cut-off values using 125 plaque-forming units as the challenge inoculum were > or = 16 and > 128 respectively. At low PRN titers (< 200), the correlation between PRN and SIA values was reasonable (r = 0.60; p < 0.001) when a challenge inoculum of 12.5 plaque-forming units was used. At the lowest PRN titers (< 100), 15% of the samples gave divergent results. These data confirm the utility of the SIA in the determination of measles-specific neutralizing antibodies when antibody titers are high. However, the PRN assay remains the test of choice when maximum sensitivity at low titers is required.

Adolescent↗
PubMed1999

Mycobacterium ulcerans infection (Buruli ulcer): first reported case in a traveler.

A chronic, painless sore developed over a 2-month period on the left calf of a Canadian man traveling for 8 months in Africa. A presumptive diagnosis of a Mycobacterium spp. infection was made despite initially negative biopsy and culture results, after failure of several courses of anti-bacterial antibiotics. Mycobacterium ulcerans was eventually isolated and the lesion progressed despite treatment with multiple anti-mycobacterial agents. The lesion finally responded to wide and repeated excision, aggressive treatment with anti-mycobacterial antibiotics, and split-thickness skin grafting. The isolation and treatment of this unusual organism are discussed.

Adult↗
PubMed1998

Measles vaccines: a review of adverse events.

A great deal of controversy has recently been generated over the publication of several articles implicating measles vaccine in the induction of Crohn's disease and autism. The publication of this work has already had a negative impact on measles vaccine acceptance in the UK. These allegations are particularly troubling because they arise in the context of increased use of measles vaccine as global control of measles nears and the international community considers strategies for a drive towards eradication. In 1994, the US Institute of Medicine reviewed the world literature and published a comprehensive review of adverse events associated with measles-containing vaccines. Reviewing the literature published between 1994 and the present day, reveals that there is considerable new data suggesting that modified gelatin rather than egg proteins is responsible for most episodes of anaphylaxis following measles vaccination. New work weakens the possible links between measles vaccine and subacute sclerosing panencephalitis and Guillain-Barré syndrome, but strengthens the rare association of measles-containing vaccines with post infectious encephalomyelitis. The alleged associations between measles vaccination and Crohn's disease and autism are based upon weak science and have largely been refuted by a large volume of stronger work. A review of the data generated in the last 4 years amply demonstrates the continued efforts of the scientific community to monitor and understand true measles vaccine-associated adverse events. The rapidity and clarity of this same community's debunking of the spurious associations with Crohn's disease and autism suggests that those charged with vaccination programmes have learned from past mistakes. During 30 years of worldwide use, measles vaccination has proven to be one of the safest and most successful health interventions in the history of mankind. It is not a 'perfect' vaccine, but the benefits of measles vaccination far outweigh the risks even in countries with low incidence of measles and high rates of measles vaccine coverage.

Child↗