An update on concurrent malaria and typhoid fever in Cameroon.

Malaria and typhoid fever are endemic diseases in Cameroon, with overlapping signs and symptoms. While the high prevalence of malaria is an established fact, it is only within the past 5 years that an unusually high number of illnesses have been diagnosed as malaria co-existing with typhoid fever. The Widal test is widely used as the sole laboratory test for the diagnosis of typhoid fever. To investigate the extent of the malaria and typhoid fever association, we used blood and stool cultures as additional diagnostic tests for typhoid fever. We report that, of 200 patients presenting with fever, 17.0% had concurrent malaria and typhoid fever (Salmonella typhi) based on bacteriological proven diagnosis as compared with 47.9% based on the Widal test. A higher proportion of patients (32.5%) had malaria coexisting with S. typhimurium when compared to S. paratyphi (2%) and S. typhi (P < 0.05). We conclude that the number of fever cases diagnosed as malaria co-existing with typhoid fever is overestimated.

Viral induction, transmission and apoptosis among cells infected by a Human Intracisternal A-type retrovirus.

Sjogren's Syndrome, a systemic autoimmune disease, is characterized by lymphocytic infiltration of the salivary or lacrimal glands, producing xerostomia or xerophthalmia. Although definitive proof of viral etiology has not been established, a cell line containing viral particles termed Human Intracisternal A-type Particles (HIAP) resulted from co-culture with patient lip biopsies. We stimulated these chronically infected cells with phorbol myristate acetate (PMA) in an effort to enhance production of viral particles for further characterization. We report that the virus present in the HIAP cell line can be induced to become lytic when subjected to PMA and that there is a difference in the effects of PMA on H9 and HIAP cell groups, with apparent protection from apoptosis due to PMA being exerted by viral presence. Delayed apoptosis may prolong exposure of the foreign/self complex, thus enhancing an autoimmune response. Polyacrylamide gel electrophoresis (PAGE) revealed the presence of new peptides in pellets of supernatants of PMA-stimulated HIAP cells, with prominent bands at 55 and 43 kDa, and several fainter ones. HIAP infection was transferred by cell-free filtered supernatants from stimulated cells to H9 cells, which became identical to parent HIAP cells by PAGE and fluorescence activated cell sorter.

Reactivity of sera from systemic lupus erythematosus and Sjögren's syndrome patients with peptides derived from human immunodeficiency virus p24 capsid antigen.

We have previously demonstrated that about one-third of patients with either Sjögren's syndrome (SS) or systemic lupus erythematosus (SLE) react to human immunodeficiency virus (HIV) p24 core protein antigen without any evidence of exposure to, or infection with, HIV itself. Herein, we further characterize the specificity of this reaction using enzyme-linked immunosorbent assay to peptides representing fragments of p24. Characteristic epitope-specific profiles were seen for SS and SLE patients. SS patients had significantly increased responses to peptides F (p24 amino acids 69 to 86) and H (amino acids 101 to 111) and diminished reactivity to peptides A (amino acids 1 to 16) and P (amino acids 214 to 228). SLE patients had increased reactivity to peptides E (amino acids 61 to 76), H, and P. Utilization of peptide P hyporeactivity as the criterion to select for SS patients results in a screen that is moderately sensitive (64%) and specific (79.3%). Adding hyperreactivity to one other peptide (F or H) as an additional criterion yields an expected decrease in sensitivity (to 41%) while increasing specificity (to 93.1%). All sera-reactive peptides from regions of known structure of HIV p24 were located in the apex of the p24 molecule. Thus, the specificity of the peptide reactivities described here indicates a specific pattern of a nonrandom cross-reactivity between HIV type 1 p24 and autoimmune sera which may be partially syndrome specific. The future focus of our work will be to optimize assays of the peptide as diagnostic tools.

Correlation between serum levels of antibodies to the 96-kD antigen of Plasmodium falciparum and protective immunity in Cameroon: a longitudinal study.

A longitudinal study was conducted in the Yaounde area of Cameroon that involved 211 individuals in June 1990, and 70 individuals for the follow-up study in December 1990. Sera from these subjects were tested against the recombinant 96-thermoresistant antigen of Plasmodium falciparum and the kinetics of antibody production to this protein show that titers tend to increase with age and are also related to antigen exposure. The increase in antibody titers with age correlates positively with the ability of the individual to prevent development of a high parasitemia. Adults who maintained stable high titers generally did not experience clinical attacks during the study period. The data suggest that antibodies against the 96-kD antigen participate in conferring some immunity to falciparum malaria.

Sera from Cameroon induce crisis forms during Plasmodium falciparum growth inhibition studies in vitro.

Sera collected from 176 children and adults from 3 different regions of Cameroon were used in inhibition assays against Plasmodium falciparum in vitro. The individuals had been classified clinically as malarious or non-malarious. Of the 58 non-malarious persons questioned, 39 claimed never to have had symptoms of the disease. Sera were tested for inhibitory effects on either merozoite entry and retardation of growth or inhibition of intraerythrocytic growth. The sera from malarious individuals showed only 9% and 29% mean inhibition values at 24 and 48 h, respectively, while those from the non-malarious persons showed 59% and 73% inhibition for the same periods. Of the 58 sera from non-malarious persons, 34 produced typical crisis forms by 24-36 h. Some sera also inhibited merozoite entry into erythrocytes. Our data suggest an important relationship between acquired immunity to P. falciparum in Cameroon and the types of inhibition described here.

Shared polypeptides from various strains of Plasmodium falciparum recognized by Cameroon sera.

Sera collected from 176 individuals residing in three malaria-endemic regions of Cameroon, West Africa, were tested against Plasmodium falciparum isolates from different areas of the world by enzyme-linked immunosorbent assay (ELISA), growth inhibition studies, and immunoprecipitation assays. A wide range of parasite proteins with apparent molecular weights of 14 to 250 kilodaltons (Kd) were immunoprecipitated by the sera. Of these, two polypeptides of 41 and 96 Kd could be associated with parasite growth inhibition in vitro.

The effects of cortisone on immunity during chronic rodent malaria.

The temporal effects were studied of a single dose of hydrocortisone acetate on the development and expression of immune responses to Plasmodium berghei in mice with chronic infections. Cortisone administration prior to primary infection reduced malaria-specific secondary humoral and cellular responses, as well as the ability to survive parasite challenge. Once protective humoral immunity was established after chemotherapy of primary infection, cortisone treatment did not disrupt its expression. Administration of cortisone during subpatent chronic infection resulted in a transient recrudescence of parasitemia not apparent in untreated mice. Clearance of recrudescence or parasite challenge was associated with a rapid cortisone-resistant antibody response. During subpatent chronic infection, malaria-specific antibody levels were reduced, whereas delayed-type hypersensitivity (DTH) to malaria antigens and heterologous antigens was well developed. At least two systems of immunity to malaria appear to be present during chronic infection. Recrudescence of parasitemia may be prevented by antibody-independent, cortisone-sensitive cellular immunity. Once parasitemia becomes overt after cortisone treatment, or parasites are reintroduced with challenge, cortisone-resistant humoral immunity appears to mediate parasite clearance. Regulation of these systems may be a dose-dependent phenomenon which results in the persistence of parasites, albeit at subpatent levels.

Competitive inhibition by soluble erythrocyte glycoproteins of penetration by Plasmodium falciparum.

Glycophorin, the major sialoglycoprotein of the erythrocyte membrane, was extracted from human erythrocyte ghosts by the lithium diiodosalicylate phenol (LIS) or chloroform-methanol (CM) methods. The products (LISgp and CMgp) were examined for their capacity to inhibit invasion of erythrocytes by Plasmodium falciparum in vitro. In the presence of either glycoprotein, parasitemia was significantly less than in control cultures, indicating competitive inhibition of attachment. Desialylation resulted in only partial loss of this inhibitory potency. Neither crystalline NANA nor the dialyzates of either hydrolyzed glycoprotein had any inhibitory effect. We conclude that the receptor for merozoites of P. falciparum probably resides in the protein portion of glycophorin, in which NANA plays a secondary role, possibly related to hydration of the cell surface. The parasite itself contains no detectable neuraminidase activity.

Effect of Plasmodium berghei on membranes of murine erythrocytes.

Membranes from normal and Plasmodium berghei-infected mice were analyzed to determine: 1) if any antigenic changes were present; and 2) the nature of these changes. Polyacrylamide gel electrophoresis (PAGE), immunological and biochemical analyses were performed on whole ghosts and glycoprotein fractions extracted from whole ghosts by chloroform-methanol. PAGE profiles and biochemical analyses revealed quantitative, but not qualitative, differences between membrane proteins and glycoproteins of normal and infected membranes. No antigenic changes were detected. The data presented here suggest that productive infection with P. berghei brings about an imbalance in the protein composition of the erythrocyte membrane, but does not result in the insertion of new proteins or glycoproteins.

Immune electron microscopy of cross-reactions between Mycoplasma pneumoniae and human erythrocytes.

Respiratory infection with Mycoplasma pneumoniae evokes immunoglobulin M autoantibody which agglutinates human erythrocytes at 4 degrees C (cold agglutinin) and is specific for I antigen. Cross-reactions between surface antigens of M. pneumoniae and human erythrocytes, previously examined by serological analysis, were examined by transmission and scanning electron microscopy. Ferritin-labeled human antimycoplasmal and rabbit antisera to erythrocyte membrane components reacted with antigens on the surface of both M. pneumoniae and erythrocytes. Adsorption of human erythrocytes to M. pneumoniae was blocked by the same antisera without ferritin label. It is proposed that the cross-reactive specificity lies in peripheral areas of the mycoplasmal cell, probably in a surface carbohydrate which has antigenic identity with erythrocyte glycoprotein.

Removal of unbound sodium dodecyl sulfate (SDS) from proteins in solution by electrophoresis through triton x-100-agarose.

Residual sodium dodecyl sulfate (SDS) introduces artifacts into immuno- and counterimmunoelectrophoretic analysis of proteins which have been eluted from preparative SDS-polyacrylamide gels. Unbound SDS can be removed by electrophoretic passage of eluted solutions through a barrier of Triton X-100 in agarose in which the anionic and non-ionic detergents interact to form micelles.

Plasmalemmal modifications of Entamoeba histolytica in vivo.

We used electron microscopy to study Entamoeba histolytica trophyozoites in rectal and liver lesions. The amebal surface had bleblike structures. Also noted were subplasmalemmal vacuoles and plasmalemmal extensions generally similar to the "surface lysosome" and "trigger" previously described. We found on serial sections that the plasmalemmal extensions were dendritic complexes enfolding the membrane of the subplasmalemmal vacuole and extending to contact host tissue. We postulate that membrane-bound cytotoxic hydrolases enter the plasmalemmal extension via the translocation of the subplasmalemmal vacuole membrane and thus are available to act at contact sites. The small blebs may provide an alternate method for membrane-bound hydrolase activity.

Hepatitis A: aislamiento "in vitro" de un agente con raras propiedades de proliferación, en un caso clínico ocurrido en Costa Rica / Hepatitis A: "in vitro" isolation of an agent with unusual growth requirements from a clinical case occurring in Costa Rica

Se aisló "in vitro" un agente enteroviroide que poseía propiedades distintas de las de este tipo de virus. Se hallaron indicaciones de infección en pares de sueros de un caso de hepatitis ocurrido en Costa Rica. Muchas de las propiedades concuerdan con las descritas acerca de los agentes de hepatitis aislados en monos tití y observados en heces humanas (AU)