The American Journal of Tropical Medicine and Hygiene - Volume 36, Issue 3, 1987

This list terminated as of 28 February 1987, when the May issue of the Journal was completed. Each of the 94 articles in Volume 36 has been seen by two or more of the colleagues listed below. These referees also have seen manuscripts that are still under review or have been rejected.

Current members of the Editorial Board are A. S. Benenson, Charles H. Calisher, Allen W. Cheever, Joel M. Dalrymple, Carter L. Diggs, James L. Hardy, Rodney C. Jung, Llewelyn J. Legters, Edgar J. Martin, Thomas P. Monath, Harry Most, Franklin A. Neva, S. Michael Phillips, Robin D. Powell, Alexis Shelokov, Robert E. Shope, Diane W. Taylor, Harold Trapido, Thomas H. Weller, and Thomas M. Yuill. Despite heavy teaching and research programs, field trips, and illnesses each of these individuals has seen and served as referee on an average of 5 manuscripts, one having seen as many as 13.

I have known this remarkable human for 25 years. In less than five minutes, I am supposed to summarized his curriculum vitae, communicate his personality inventory, and embarrass him modestly. There are only two ways to modestly embarrass Franz: The first is to tell him the truth about himself, and the second is to give him something. I shall try to do both.

Franz was born into the medical aristocracy of Vienna, Austria. His grandfather was knighted for starting the speciality of otorhinolaryngology, and his father, the first Professor of Urology at the University of Berlin, created the technique of intravenous pyelography. Franz was born in 1919 in Miskolc, Hungary. He started medical school in Vienna in 1937, but school was interrupted by the cataclysm that enveloped Europe, and Franz and his family fled, spending a year in a refugee camp in Greece. He completed his M.D. degree in Mexico City in 1945.

A year of presidency is also an opportunity to gain a better understanding of the Society to which one belongs and I thought my farewell address would be the time to share with you some thoughts on who we are and what brings us together. The better we understand the demographics of our membership and the spectrum of our collective research experiences and aspirations, the easier it should be for our community to mesh and thrive. Also, a survey of the last decade's trends in our own scientific program and in the biomedical world at large should be of some help in planning for the future. Other presidents have chosen themes related to their own work as investigators or have given us an overview of progress in specific disease entities, but looking at the dense and rich scientific program before you I felt I should provide a little relief from serious research.

An enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody that recognizes a repetitive epitope on the circumsporozoite protein of Plasmodium falciparum was used in Kenya to assess malaria infections in Anopheles gambiae s.l. and An. funestus. The ELISA confirmed that 88% of 44 sporozoite-positive gland dissections were P. falciparum. The ELISA infection rate of 18.6% (n = 736) for individually tested mosquitoes for both species was significantly higher than the 10.4% (n = 537) salivary gland sporozoite rate determined by dissection. This difference was due to ELISA detection of medium and large sized oocysts on the midguts of infected mosquitoes which did not contain salivary gland sporozoites. From a series of 379 Anopheles that were cut at the thorax, ELISA tests on “head” and “body” portions showed that 29.5% of 95 positive mosquitoes contained circumsporozoite antigen in the body portion in the absence of salivary gland infections. This field evaluation demonstrates that the ELISA can most accurately be used to estimate sporozoite rates by cutting mosquitoes at the thorax and testing anterior portions.

Chloroquine, in a single dose of 10 mg of base/kg, was given orally to Togolese children <5 years of age as primary therapy for Plasmodium falciparum malaria. A simplified World Health Organization in vivo method was used, as was a sequential analysis procedure for determining if the drug trial was a success or failure. A total of 178 children in 3 regions were treated; 174 (98%) responded successfully, which required a ≥75% reduction in parasites by day 2 and elimination of parasites by day 7. All 4 failures had low blood levels of chloroquine and desethylchloroquine at day 7. A single dose of chloroquine for treating malaria can be considered for those areas of Africa where the efficacy of such therapy is documented, and where an antimalarial drug sensitivity monitoring system is operating.

Four- to six-week-old hamsters were infected with 1.5 × 107 Plasmodium berghei-parasitized hamster red blood cells by intraperitoneal injection. Cheek pouch circulation was observed microscopically in the anesthetized animal; the brain and contralateral pouch were collected for histopathologic examination on days 3–12 post-challenge. Cheek pouch vascular lesions, observed in vivo, appear to involve three phenomena; early (beginning 3–4 days) adhesion of pigment-laden mononuclear cells to endothelium within venous vessels and loss of function of the small capillaries supplying the skeletal muscle fibers and, later (6–9 days), the apparent attraction of erythrocytes to venular and venous endothelium and to adherent monocytes. The aggregation of formed elements on endothelial walls leads to progressive occlusion of venules and small veins and contributes to the observed disruption of flow through capillary networks. Histopathology of the brain and pouch shows vascular changes similar to those seen in vivo; in addition, multifocal hemorrhages are seen commonly in the brain and occasionally in the pouch on postmortem. In severe disease, evidence of cerebral edema is seen in the brain. The data suggest that failure of capillary flow and disruption of venous outflow tracts by cell aggregates are central to vascular failure in both the cheek pouch and brain of the P. berghei infected hamster. This hamster model of human cerebral malaria allows the in vivo observation, still and video photomicrography, and manipulation of the peripheral vascular pathogenesis of a disease process similar to that seen in humans.

The subcellular localization of the 150/130 Kd antigen in Plasmodium falciparum-infected erythrocytes was determined by electron microscopy using monoclonal antibody 9B11 and immuno-gold labeling. We now find that this antigen may be associated with the membrane of newly-infected human erythrocytes and the cytoplasm of ring stage parasites. During differentiation of the parasite to the trophozoite stage, the antigens are no longer detectable on the erythrocyte membrane, while gold particles become more numerous within the parasite and in the erythrocyte cytoplasm adjacent to the parasite. As the parasites develop into schizonts, more antigen appears within the parasites, and some of it appears in the erythrocyte cytoplasm. At the segmented schizont stage, many intraparasitic gold particles are associated with rhoptries and micronemes of developing merozoites. Likewise, gold particles are associated with elements of the rhoptry-microneme complex in free merozoites. No gold particles are detected on the surface of merozoites. These antigens are found most abundantly in erythrocytes infected with gametocytes, revealing a localization pattern similar to that of mature trophozoite-infected erythrocytes. These subcellular localization patterns are similar to those described for the ring-infected erythrocyte surface antigen.

Seven methods of diagnosing leishmaniasis were compared in 177 patients presenting with lesions of the skin (165) or mucosa (12) in Tumaco and Cali, Colombia. The three methods of visualizing amastigotes in tissue samples (histological staining of tissue sections, impression smears of punch biopsies, and smears of dermal scraping from slits in the lesion margins) were less sensitive than the four Leishmania isolation methods (aspiration of lesion border cultured in biphasic media, aspirate inoculated into hamster nasal tissue, culture of punch biopsy macerate, and hamster inoculation of macerate). The aspirate-culture and biopsy-hamster methods employed in this study proved most sensitive of the four methods for the recovery of parasites. The combined overall sensitivity of the 7 methods was 67% for all enrolled patients and 75% for Montenegro skin test-positive patients. The individual sensitivities for the methods for all patients and Montenegropositive patients, respectively, were: histopathology 14% and 16%, impression smear 19% and 21%, dermal scraping 22% and 26%, aspirate-culture 58% and 64%, aspirate-hamster 38% and 41%, biopsy-culture 50% and 55%, and biopsy-hamster 52% and 57%. All methods were less sensitive in lesions of greater than 6 months duration than in lesions of more recent onset. Mucosal lesions were best diagnosed by the culture or hamster inoculation of a macerated mucosal biopsy. The diagnosis by inoculation of hamsters was achieved within 2 to 12 weeks, a mean of 34.5 days. Promastigotes were seen on Senekjie's medium within 3–8 days. Based on these results we recommend dermal scraping smears for immediate diagnosis and culture of aspirates for a definitive parasitological diagnosis of cutaneous lesions. Culture and hamster inoculation of macerated biopsies are recommended for the diagnosis of mucosal lesions.

Populations of peripheral blood T lymphocytes from patients with Kenyan visceral leishmaniasis were studied using specifically defined antisera (monoclonal antibodies, Ortho-mune® OKT3, OKT4, OKT6, and OKT8). The levels of total T lymphocytes and circulating thymocytes were within the same range as those of clinically normal individuals. However, the proportions of the helper/inducer T cells were lower in untreated patients than in the controls (18.9% vs. 39.7%) while the levels of suppressor/cytotoxic T cells were higher than in the controls (40.5% vs. 27.8%). After successful antileishmania treatment these levels showed a gradual return towards normal over a period of one year. It was concluded that immunosuppression observed is due to the levels of peripheral blood helper/inducer and suppressor/cytotoxic T lymphocytes.

Adherent cells and serum components from Kenyan patients with visceral leishmaniasis were examined with the view to evaluating their contribution to cell-mediated immune suppression. Mitogens (phytohemagglutinin and concanavalin A) and antigens (purified protein derivative, streptokinase-streptodornase, and leishmania) were used as stimulants. Compared to the controls, the contribution of serum components to suppression in presence of any of the mitogens and antigens was not significant. The same applied to adherent cells, except in the presence of leishmania antigen where adherent cells contributed significantly (P < 0.001). Removal of adherent cells from peripheral blood mononuclear cells of patients and controls considerably increased in vitro lymphocyte responses to both mitogens and antigens (by about twice), suggesting that in this study, the inhibition of in vitro lymphocyte responses to antigens and mitogens by adherent cells was a general phenomenon independent of the presence of the disease.

The lack of an adequate system for the in vitro cultivation of Cryptosporidium spp. has forced researchers to work on infected feces or tissues. Molecular and immunological analyses of Cryptosporidium stages must be preceded by complex preparatory steps involving the concentration, storage, purification, excystation of oocysts, and purification of sporozoites. This paper describes two new procedures for the purification of Cryptosporidium. The first, consisting of pretreatment of oocysts with sodium hypochlorite followed by concentration using a Percoll gradient, is suitable for nucleic acid analyses. The second, a concentration of untreated oocysts using a Cesium chloride gradient, is suitable for biochemical and immunological studies, but requires “fresh” oocysts.

Although Toxoplasma gondii is the most commonly recognized cause of central nervous system mass lesions in patients with acquired immune deficiency syndrome, published investigations have provided little information about criteria for diagnosis of toxoplasmosis or the response to therapy. In this series the method of diagnosis and response to therapy were assessed in 14 patients who had evidence for toxoplasmosis based on routine histopathology, immunoperoxidase staining, or mouse inoculation. These patients presented with clinical and radiologic findings that did not clearly distinguish them from patients with other infectious or neoplastic processes. Excisional biopsies usually showed tachyzoites on routine histology, but needle biopsies were usually negative unless mouse inoculation or immunoperoxidase staining was employed. Response to pyrimethamine and sulfadiazine therapy was often prompt, but therapy had to be continued for long periods of time to maintain a clinical response, and no alternative regimen of one or more drugs appeared to be effective in patients unable to tolerate both pyrimethamine and sulfadiazine.

Seemingly intact cysts and sequential stages of disintegrating cysts of Toxoplasma were identified immunohistologically within developing microglial nodules in a Panamanian night monkey (Aotus lemurinus). This monkey had been successfully immunized and challenged 5 months earlier. This supports the hypothesis that glial nodules unassociated with Toxoplasma tachyzoites may represent the tombstone of a Toxoplasma cyst. Disintegration of cysts may give rise to clinical encephalitis in the presence of apparently adequate immunity.

A stock of Trypanosoma cruzi was recovered from a Triatoma dimidiata from Tegucigalpa, Honduras. This stock was shown to be capable of development and transmission by native California Triatoma protracta protracta. Isozyme analysis indicated that this T. cruzi is closely related to the Tehuantepec strain and to a lesser extent the Miles' zymodeme 1 strain. The potential public health significance of development and transmission of exotic stocks of T. cruzi by native reduviids is discussed.

We report in this paper significant differences in the virulence of insect-derived and cultured metacyclic forms of Trypanosoma cruzi which are morphologically indistinguishable. Mice infected intraperitoneally with 103 metacyclic T. cruzi isolated from Rhodnius prolixus showed average parasitemia levels greater than 2 × 105 organisms/ml around day 10 post-infection (when first measured) and peak levels recorded on day 16 post-infection exceeded 4 × 107 organisms/ml. None of these animals survived after 30 days post-infection. In contrast, in mice infected with 103 or 104 metacyclic forms from axenic cultures the highest average parasitemia was approximately 104 organisms/ml and occurred around day 19 post-infection. In these animals, parasitemias declined with time to become undetectable and no mortality was recorded over the 100-day observation period. There was also a marked difference in the 50% lethal dose of insect- and culture-derived metacyclics. The value for the former was 670 parasites whereas none of the mice infected intraperitoneally with up to 106 cultured metacyclics died. These results point to a marked difference in the biological properties of insect-borne and cultured T. cruzi metacyclics under our experimental conditions and caution against extending results obtained with the latter to vector-transmissible metacyclics, at least in infectivity and virulence studies.

The relationship between the growth rate of Trypanosoma brucei gambiense and its virulence was investigated. A cloned, monomorphic, slow growing, and relatively avirulent line of T. b. gambiense was serially passaged at 3- to 5-day intervals through immunosuppressed mice. The growth rate measured within the first 2 patent days of infection did not vary significantly through the first 25 passages but by passage 50 had decreased significantly from 11.9 ± 1.1 hr to 9.0 ± 0.7 hr. A clone from passage 50 and three different second peak heterologous variants all had statistically similar growth rates, indicating that the rate of proliferation was a stable trait. With the faster rate of proliferation there was a corresponding increase in virulence. The inoculum necessary to kill 50% of normal outbred mice in the first peak of parasitemia (LD50) dropped significantly from 3 × 106 first passage parasites to 4 × 105 passage 50 parasites. The lethal load for both fast and slow growing organisms was the same (> 2 × 109 trypanosomes/ml of blood). To further link virulence and growth rate, a strong correlation (r = 0.89) was measured when generation times of 10 closely related lines of T. b. gambiense, and 2 lines of pleomorphic T. b. rhodesiense were compared to their LD50 values. While the rate of trypanosomal proliferation was similar between the day of inoculation through the second patent day, it slowed to 64% of that level once parasitemias exceeded 3 × 108 organisms/ml of host blood. This inhibition of growth occurred to similar degrees in both monomorphic and pleomorphic lines of trypanosomes, at about the same level of parasitemia, in both immunosuppressed or immunologically intact mice. Virulence could not be correlated to the growth rate measured late in the first peak of parasitemia, a pleomorphism of the trypanosomal line, or its variant antigen type.

Human monocytes maintained in culture lose microbicidal activity against intracellular protozoa which has been correlated with attenuation of the respiratory burst. The granule enzyme myeloperoxidase, which can markedly amplify hydrogen peroxide-pendent antimicrobial activity, is also lost in vitro. Adherent monocytes were examined immediately, 3 and 10–14 days following explanation, for the magnitude of the stimulated respiratory burst and for cellular myeloperoxidase. Fresh cells generated 254 ± 38 nmol O2 -/mg protein as compared to a peak of 782 ± 45 nmol O2 -/mg at 3 days and < 100 nmol O2 -/mg after 10–14 days. The myeloperoxidase content of the cells also decreased; over 85% was lost after 3 days. Fresh monocytes killed over 90% of ingested Toxoplasma gondii or Leishmania major. In contrast, 10–14 day explanted monocytes killed only 12% of ingested Toxoplasma and 33% of Leishmania, and surviving organisms replicated readily. The 3-day monocytes were significantly less able to kill protozoa than were fresh cells despite their nearly 3-fold greater generation of O2 -. If peroxidase was reintroduced into 3-day monocytes by coating organisms with eosinophil peroxidase prior to phagocytosis, their antiprotozoa activity was nearly restored to that of freshly explanted cells.

Because dual infection with Schistosoma mansoni and hepatitis B may lead to severe liver disease, populations living in schistosomiasis-endemic areas might benefit if effectively immunized against hepatitis B. To determine whether a plasma-derived hepatitis B vaccine is immunogenic in patients with schistosomiasis, 32 individuals infected with S. mansoni were given three 20-µg doses of Heptavax-B vaccine and treated with praziquantel. Antibody to hepatitis B surface antigen developed in 90.6% of the study subjects after three doses of vaccine. Five patients (15.6%) had a weak response to the vaccine, and three patients (9.4%) failed to develop antibody. A weak or failed response to the vaccine was significantly associated with the presence of hepatosplenomegaly. A plasma-derived vaccine is immunogenic for persons infected with S. mansoni; however, vaccine response is diminished in hepatosplenic schistosomiasis.

We developed a sandwich enzyme-linked immunosorbent assay to detect circulating parasite antigens in human lymphatic filariasis. The assay utilizes a polyclonal rabbit antifilarial antiserum to capture, and a monoclonal antibody to identify, circulating parasite antigen. Using this assay, we found that >95% of sera from microfilaremic donors with bancrofitian or brugian filariasis, approximately 60% of sera from amicrofilaremic patients with hydroceles, chyluria, or elephantiasis, and 15%–20% of sera from asymptomatic residents of filariasis-endemic areas evidently contain filarial antigens. Antigen was also detected in the urine of some microfilaremic patients. Serum levels of antigen detected with one monoclonal antibody, ES34, correlated well with microfilarial density in night blood. In contrast, < 5% of sera from residents of areas where lymphatic filariasis is not endemic reacted in the assay, even though approximately one-third of the donors whose sera were tested were known to be infected with intestinal nematodes. The assay was designed to be flexible enough to allow the parallel use of multiple monoclonal antibodies with different specificities and simple enough to be applicable in most areas where lymphatic filariasis is endemic.

Black fly vectors of onchocerciasis from three ecologically different Simuliid breeding habitats in the Firestone Rubber Plantation at Harbel, Liberia, were surveyed by human-biting collections conducted at weekly intervals over a 13-month period. Black flies were identified morphologically and the monthly and seasonal contribution of different vector species to the transmission of Onchocerca volvulus at each site was determined.

Simulium yahense was identified as the predominant vector species at each site. Greatest populations of this species occurred during wet season (May–Oct), but its impact on transmission of onchocerciasis was most profound during dry season (Nov–Apr) when parity, infection, and infectivity were high. S. sanctipauli was the only other vector species captured, but biting populations of this species were small, and during wet season confined primarily to the vicinity of its breeding site in the Farmington River. Dry season populations of S. sanctipauli were also characterized by lower human-biting rates, and by higher rates of parity, infection, and infectivity.

Monthly transmission potentials at each site were attributed primarily to S. yahense, with peak monthly transmission occurring during the dry season months of January–April. Against the WHO standard of 100 as a “tolerable” annual level of onchocerciasis transmission, annual transmission potentials for the three sampling sites were 94, 1,877, and 4,900, with highest values being calculated for S. yahense breeding sites.