Adel A. F. Mahmoud

Global health 2035: a world converging within a generation

Prompted by the 20th anniversary of the 1993 World Development Report a Lancet Commission revisited the case for investment in health and developed a new investment frame work to achieve dramatic health gains by 2035. The report has four key messages each accompanied by opportunities for action by national governments of low-income and middle-income countries and by the international community. Conclusion 1: there is a very large payoff from investing in health. Conclusion 2: a grand convergence is achievable within our lifetime. Conclusion 3: scale-up of low-cost packages of interventions can enable major progress in NCDs and injuries within a generation. Conclusion 4: progressive universalism is an effi cient way to achieve health and fi nancial protection.

GIARDIASIS IN THE MOUSE: AN ANIMAL MODEL

An animal model for giardiasis was developed using Giardia muris in Swiss albino mice. Intraesophageal inoculation of G. muris cysts caused a reproducible pattern of infection, with trophozoite and cyst counts reaching a maximum on days 5 to 14 after cyst inoculation and thereafter showing a progressive decline. Spontaneous resolution of infection occurred in most mice after 21 to 28 days. When compared to uninfected controls, Giardia-infected mice had significant impairment of weight gain and a significant reduction in the villus to crypt ratio of jejunal mucosa. Although maximal trophozoite and cyst counts were independent of the size of the cyst inoculum, those mice receiving inoculations of larger numbers of cysts showed earlier attainment of maximal counts, greater impariment of weight gain, and earlier and more severe small bowel changes than mice receiving inoculations of smaller numbers of cysts. This model offers unique opportunities for study of this poorly understood gastrointestinal parasite.

HIV vaccine research: the way forward.

The need to broaden research directed at answering fundamental questions in HIV vaccine discovery through laboratory, nonhuman primate (NHP), and clinical research has recently been emphasized. In addition, the importance of attracting and retaining young researchers, developing better NHP models, and more closely linking NHP and clinical research is being stressed. In an era of a level budget for biomedical research at the U.S. National Institutes of Health (NIH), HIV/AIDS vaccine research efforts will need to be carefully prioritized such that resources to energize HIV vaccine discovery can be identified. This article summarizes progress and challenges in HIV vaccine research, the priorities arising from a recent summit at NIAID, and the actions needed, some already under way, to address those priorities.

Drugs Five Years Later: Praziquantel

PURPOSE To identify advances in knowledge of the pharmacokinetics, mechanism of action, clinical use, and side effects of the antihelminthic drug praziquantel in the 5 years since its introduction in the United States. DATA IDENTIFICATION Studies reported from 1983 to July 1988 were identified by computer searches of MEDLINE and TOXLINE, and review of textbooks and review articles. STUDY SELECTION Of 57 articles originally identified, 39 were selected by two readers. DATA EXTRACTION Study quality and significance were independently assessed by each reader. RESULTS OF DATA ANALYSIS The pharmacokinetics and clinical efficacy of praziquantel have been well documented. Yet, despite extensive in vivo and in vitro laboratory studies, the drugs mechanism of action in killing parasites is unknown. Although the efficacy of praziquantel was first established for treating schistosomiasis, in the last 5 years its clinical use has been expanded to the treatment of intestinal, tissue, and lung flukes, and intestinal and tissue cestode infections, including neurocysticercosis. The introduction of praziquantel was a significant advance in antihelminthic therapy, in that it was effective therapy for several parasites that had been previously considered untreatable. Availability of a safe, effective broad-spectrum oral antihelminthic agent consolidated the central role of chemotherapy in population-based control of many trematode and cestode parasites. Randomized trials have shown, however, that older, cheaper agents may be more cost-effective in controlling Schistosoma mansoni and Schistosoma haematobium in some endemic areas. CONCLUSIONS Although praziquantel is the treatment of choice for most human trematode and cestode infections, cost factors have limited its use in developing countries.

Suppression of cell-mediated immunity by metronidazole.

Metronidazole administered orally in doses of 20 and 200 mg/kg daily suppressed granuloma formation around Schistosoma mansoni eggs which were injected intravenously and lodged in the pulmonary microvasculature of mice. The same doses did not suppress granuloma formation in animals which had previously been sensitized to the eggs. Nonspecific granulomatous inflammation around divinyl benzene copolymer beads was unaffected by the drug. In a daily dose of 20 mg/kg, metronidazole inhibited delayed footpad reactions to soluble schistosome egg antigen, but 200 mg/kg on alternate days failed to suppress skin allograft rejection. The drug appears to suppress selectively some aspects of cell-mediated immunity.

Role of Cell-generated Hydrogen Peroxide in Granulocyte-mediated Killing of Schistosomula of Schistosoma mansoni In Vitro

Human as well as murine granulocytes have been shown to kill the larval stages of helminth parasites; the mechanism of this cell-mediated cytotoxicity is, however, poorly understood. The present study was designed to assess the role of peroxidative processes in killing of schistosomula of Schistosoma mansoni by human granulocytes in vitro. The rate of H(2)O(2) production by human neutrophils, eosinophils, and basophils was measured upon incubation with schistosomula alone or in the presence of specific antibody or complement. Opsonized parasites (antibody and/or complement) increased the rate of H(2)O(2) production by neutrophils, eosinophils, and basophils by respective percentages of 500, 500, and 371. The rate of H(2)O(2) release was directly related to the number of granulocytes and to the proportion of cells attached to the surface of the schistosomula. Increased hydrogen peroxide release occurred by 10 min of incubation and was demonstrable up to 16 h after addition of leukocytes to schistosomula. The primary source of this oxygen product was found to be the granulocytes adherent to the schistosomula and not those that remained unattached. Hydrogen peroxide production by neutrophils and eosinophils was quantitatively similar (schistosomula coated with antibody plus complement stimulated 5 x 10(6) neutrophils and eosinophils to release H(2)O(2) at respective rates of 0.35 and 0.40 nmol/min). Granulocyte-mediated parasite killing correlated with rate of H(2)O(2) generation; both processes were inhibited by catalase. To define further the role of oxidative metabolites, neutrophils and eosinophils of two subjects with chronic granulomatous disease were used; marked reduction of granulocyte-mediated parasite mortality was observed. Peroxidase was required for H(2)O(2)-mediated killing. Addition of the peroxidase inhibitors azide (1 mM), cyanide (1 mM), or aminotriazole (1 cM) to neutrophilschistosomula mixtures significantly reduced parasite cytotoxicity (P < 0.01); similar reduction was observed when eosinophils were used (P < 0.01). Fixation of halide (iodide) to trichloroacetic acid-precipitable protein (2.4-6.0 nmol/h per 10(7) neutrophils) was demonstrated in the presence of granulocytes, opsonins, and parasites; this process was completely inhibited by 1 mM azide. These data indicate that contact between the surfaces of human granulocytes and schistosomula results in release of cellular hydrogen peroxide and iodination. The generation of H(2)O(2) and its interaction with peroxidase appear to be crucial in effecting in vitro granulocyte-mediated parasite cytotoxicity.

Induction of resistance to Schistosoma mansoni infection in mice by purified parasite paramyosin.

Freeze-thaw (FT)-disrupted schistosomula or their membrane extract induced significant resistance in mice to Schistosoma mansoni infection (34 and 25%, respectively) without the use of adjuvant. Antigens identified in schistosome extracts by sera from immunized animals were then evaluated for protective potential. Immunization with schistosomal antigens of 97 and 68-70 kD resulted in significant protection that was equivalent to that obtained by FT schistosomula. Since the 97-kD antigen was suggested to be parasite paramyosin, we used a biochemical technique to purify this muscle protein. Purified schistosome paramyosin ran as a single band on 10% SDS-PAGE and was recognized both by sera from mice immunized with FT schistosomula and a polyclonal antiserum raised against the 97-kD parasite protein. Preincubation of schistosome paramyosin with sera from mice immunized with FT schistosomula resulted in the removal of reactivity with the 97-kD protein in crude worm extracts. Paramyosin was identified by Western blotting to be in the tegument of schistosomula. The purified schistosome paramyosin resulted in significant protection in three separate experiments (24, 46, and 53%) without the use of adjuvant. Addition of BCG to paramyosin resulted in enhanced protection.

Induced and spontaneous diabetes mellitus and suppression of cell-mediated immunologic responses. Granuloma formation, delayed dermal reactivity and allograft rejection.

These investigations delineate the recently described suppression of a form of cellular hypersensitivity in mice with streptozotocin-induced diabetes mellitus using a variety of cell-mediated immunologic responses in animals with several different forms of diabetes. Streptozotocin- and alloxan-induced diabetic mice and db/db genetically determined diabetic mice showed reductions in the areas of inflammation around Schistosoma mansoni eggs injected into the pulmonary vasculature of 68, 70, 77%, respectively. In contrast, streptozotocin-induced diabetes had no effect on the nonimmunologic foreign body granuloma around divinyl benzene copolymer beads injected into the pulmonary arterioles. Animals protected from diabetes by treatment with nicotinamide before streptozotocin administration did not develop hyperglycemia and had normal areas of immunologic granuloma formation around schistosome eggs. Treatment with insulin reversed the suppression of schistosome egg granuloma formation in both streptozotocin- and alloxan-diabetic animals. Two additional in vivo parameters of cellular immunologic reactivity were examined in streptozotocin-induced diabetes: delayed footpad swelling was essentially eliminated; skin graft survival across the H-2 area was significantly prolonged from 10.2 days in the controls to 14.4 days in moderately diabetic A/J mice. These observations suggest that diabetes mellitus is associated with suppression of cell-mediated reactions in vivo and that the defect is reversible with insulin treatment.

Establishing a Global Vaccine-Development Fund

An international vaccine-development fund could provide the resources and momentum to carry vaccines from their conception to their development and licensure — thereby helping to avert a repetition of the Ebola crisis.

Eosinophilopoietin. A circulating low molecular weight peptide-like substance which stimulates the production of eosinophils in mice.

In earlier studies, methods were developed to raise specific antibodies in rabbits against purified suspensions of mouse or human eosinophils. On administration of antieosinophil serum (AES) to mice, the mature eosinophils in tissues, peripheral blood, and bone marrow were depleted, while the immature eosinophil pool in the bone marrow was observed to proliferate. The current investigations explore the generation of eosinophilopoietic factors during AES-induced eosinophilopenia. Mice received three injections of AES, one every other day. As the peripheral eosinophil counts started to recover after the last AES injection, the serum was collected and transferred to normal animals. Within 2 days the recipients showed an increase in peripheral blood as well as in bone marrow eosinophils. The rise in bone marrow eosinophils was due to newly formed cells as evidenced by increased uptake of [(3)H]thymidine. The generation of eosinophilopoietic activity was specifically related to depletion of eosinophils but not neutrophils. The eosinophilopoietic activity was: (a) dependent on the volume of serum transferred, (b) lost on dialysis, and (c) largely heat labile. The activity eluted as a low molecular weight substance on G-25 Sephadex and was digested by pronase but not by trypsin. Active fractions collected from G-25 columns were not chemotactic for the eosinophils in vitro. Thus, specific depletion of mature eosinophils generates a low molecular weight peptide which stimulates eosinophilopoiesis in vivo. It is suggested that this substance be named eosinophilopoietin.