[HTLV-I/II in Switzerland: apropos of 4 case reports]

HTLV-I/II (human T-cell lymphotropic virus type I and II) infection is endemic in South Japan, Subsaharan Africa, the Caribbean and in regions of South America and of the United States. The infection almost always remains asymptomatic but is also associated with two distinct diseases: tropical spastic paraparesis (TSP), and adult T-cell leukemia (ATL). Although very rare in Europe, HTLV-I/II infection may occur in patients originating from endemic areas. We report the cases of four patients seropositive for HTLV-I/II, all of them living in Switzerland. Three of them originate from Zaire; the fourth is a Swiss female married to a Taiwanese. One patient has TSP; one has pyramidal signs along with systemic vasculitis-associated neuropathy; the third is HIV-position with stage III B infection, without symptoms of TSP or ATL; the last is entirely asymptomatic.

Epidemiological basis for clinical diagnosis of childhood malaria in endemic zone in West Africa

It is difficult to distinguish childhood malaria from other common febrile disorders by parasite count alone, because of the wide variation in tolerance of parasitaemia among individuals. We postulated that the proportion of febrile episodes among young children that can be attributed to parasitaemia varies according to simple clinical criteria. We studied 1114 children aged 2-9 years, who attended a dispensary in the Republic of Niger, with a case-control approach; each of 557 febrile children was matched with a non-febrile control by sex, age, ethnic group, and day of presentation. Febrile episodes were classified according to three clinical criteria: the presence of a likely non-malarial cause; the duration (less than 3 or more than 3 days before presentation); and the intensity (below 39 degrees C or 39 degrees C and above). There was no evidence for an association between febrile episodes and parasite count during the dry, low-transmission, season. During the rainy, high-transmission, season, by contrast, there was a highly significant relation (p less than 0.0001) between the likelihood of fever and the parasite count; each clinical criterion strengthened the association. There was no association between parasitaemia and low intensity fevers, with an obvious cause, that started 3 or more days before presentation, even in the rainy season; however, the relative risk of a fever that met all three criteria developing in those with vs those without parasitaemia was 27.5. The proportion of febrile cases attributable to detectable parasitaemia (population attributable risk) ranged from 0 to 0.92. Our results suggest that simple clinical criteria may be valuable in the selection of febrile patients for antimalarial treatment. In this geographic area, high fever of short duration and with no other obvious cause that occurs during the rainy season is most likely to be malaria.

Bullous pemphigoid autoantibodies, HIV-1 infection and pruritic papular eruption

Bullous pemphigoid (BP)-type autoantibodies were found by Western blot (WB) analysis of epidermal extracts in the serum of 38% of HIV-seropositive patients compared with 21% of HIV-seronegative patients with chronic pruritus and 76% of patients with BP. They were further identified as BP autoantibodies (BPab) by immunoprecipitation and immunoelectron microscopy. Their incidence increased from 21% in HIV infection stage II to 37% and 43% in stages III and IV, respectively. Of the patients suffering from HIV-related chronic pruritic papulovesicular eruption. 75% showed circulating BPab as compared with 29% in those without skin problems (P = 0.0066) and, among them, 30% met the diagnostic criteria for BP when histology, WB, immunofluorescence and immunoelectron microscopy techniques were used. In conclusion, this study identifies an autoimmune skin reaction that may account for, or be related to, the distressing pruritic eruptions occurring in HIV-infected patients.

Loss of antibodies against hepatitis C virus in HIV-seropositive intravenous drug users

A time-point survey of 262 ex-intravenous drug users (IVDUs) on methadone treatment showed serological evidence of hepatitis C virus (HCV) in 64%, hepatitis B virus in 74% and HIV in 36%. Analysis of previously collected frozen stored sera of the same patients showed that 31 further IVDUs had had anti-HCV antibodies in the past and had lost them in a time-dependent fashion. Most HCV seroreversion was detected in HIV-positive people: 20 out of 85 in the HIV-positive group versus 11 out of 18 in the HIV-negative group.

Human T cell activation. Synergy between CD73 (ecto-5'-nucleotidase) and signals delivered through CD3 and CD2 molecules

Interaction of the glycosyl phosphatidylinositol-linked differentiation Ag CD73 (ecto-5'-nucleotidase) with the CD73-specific mAb 1E9 generates agonistic signals that strongly synergize with T cell activation induced by CD3 and CD2 mAb. This synergy is observed only when 1E9 is immobilized on plastic and occurs in the absence of accessory cells or exogenous lymphokines. 1E9 induces a rapid (though transient) increase in [Ca2+]i in a minor proportion (20 to 30%) of unfractionated T lymphocytes (presumably CD73+ cells). However, this [Ca2+]i mobilization is not sufficient to fully activate CD73+ T cells, as shown by the requirement of additional signals such as CD3 or CD2 stimulation to initiate T cell proliferation. These signals cannot be substituted by the exogenous lymphokines, rIL-1, rIL-2, or rIL-4, or PMA (when T cells are rigorously depleted of monocytes). These data indicate that CD73 may behave as an accessory molecule regulating interactions between T cells and antigens or APC. A comparison was carried out with mAb 9.3 to the differentiation Ag CD28, another agonistic molecule with activating properties similar to CD73. Despite their lower percentage, the ability of CD73+ T cells to amplify the proliferation induced by CD3 or CD2 mAb was equivalent or even greater than that of CD28+ T cells. Once activated, CD73+ cells may recruit the remaining (CD73-) cells primed by CD3 or CD2 stimulation. Based on these data, we suggest that CD73+ T lymphocytes may be a specialized subset to amplify immune responses originated by the CD3 and CD2 activation pathways. Finally, the functional association between CD73 and integral membrane molecules like CD3 and CD2 suggests that GPI-anchored molecules may play a role in transmembrane signaling mediated by conventional second messenger systems.

Human T cell activation. Synergy between CD73 (ecto-5'-nucleotidase) and signals delivered through CD3 and CD2 molecules

Interaction of the glycosyl phosphatidylinositol-linked differentiation Ag CD73 (ecto-5'-nucleotidase) with the CD73-specific mAb 1E9 generates agonistic signals that strongly synergize with T cell activation induced by CD3 and CD2 mAb. This synergy is observed only when 1E9 is immobilized on plastic and occurs in the absence of accessory cells or exogenous lymphokines. 1E9 induces a rapid (though transient) increase in [Ca2+]i in a minor proportion (20 to 30%) of unfractionated T lymphocytes (presumably CD73+ cells). However, this [Ca2+]i mobilization is not sufficient to fully activate CD73+ T cells, as shown by the requirement of additional signals such as CD3 or CD2 stimulation to initiate T cell proliferation. These signals cannot be substituted by the exogenous lymphokines, rIL-1, rIL-2, or rIL-4, or PMA (when T cells are rigorously depleted of monocytes). These data indicate that CD73 may behave as an accessory molecule regulating interactions between T cells and antigens or APC. A comparison was carried out with mAb 9.3 to the differentiation Ag CD28, another agonistic molecule with activating properties similar to CD73. Despite their lower percentage, the ability of CD73+ T cells to amplify the proliferation induced by CD3 or CD2 mAb was equivalent or even greater than that of CD28+ T cells. Once activated, CD73+ cells may recruit the remaining (CD73-) cells primed by CD3 or CD2 stimulation. Based on these data, we suggest that CD73+ T lymphocytes may be a specialized subset to amplify immune responses originated by the CD3 and CD2 activation pathways. Finally, the functional association between CD73 and integral membrane molecules like CD3 and CD2 suggests that GPI-anchored molecules may play a role in transmembrane signaling mediated by conventional second messenger systems.

Behavioural changes in intravenous drug users in Geneva: rise and fall of HIV infection, 1980-1989

In the early 1980s, more than 90% of intravenous drug users (IVDUs) shared needles and syringes in Geneva. The prevalence of antibodies to HIV in the sera of outpatient IVDUs increased from 6% in 1981 to 38% in 1983; it was, however, still only 37% in 1988. IVDUs starting methadone maintenance in 1987-1989 had a seroprevalence rate of 22%. In 1989 the percentage of IVDUs exchanging syringes and needles fell to only 5% of seropositive addicts. Only one seroconversion was observed in 1094 patient-months of observation in 1988-1989, which was probably due to sexual contact. The evidence suggests that, in the IDVUs studied, transmission of HIV has diminished since the early 1980s.

Hypohaptoglobinaemia as an epidemiological and clinical indicator for malaria. Results of two studies in a hyperendemic region in West Africa

Hypohaptoglobinaemia is a common phenomenon in tropical countries, where it is probably due to malaria-induced haemolysis. Two studies were carried out in a hyperendemic zone of West Africa to test its specificity and usefulness as an epidemiological indicator for measuring malaria endemicity. The first study evaluated the prevalence of hypohaptoglobinaemia before and after courses of antimalarial chemotherapy of varying duration. The second monitored haptoglobin levels in an untreated population during a whole year to compare its seasonal variations with those of several classic indicators of malaria. These studies suggest that in regions where malaria is endemic the prevalence of hypohaptoglobinaemia could be as useful an indicator as the parasitic index but would be much easier to establish and to monitor.

[Polyclonal B cell activation in infection caused by human immunodeficiency virus (HIV)]

87 patients with anti-HIV antibodies were divided into three groups based on the classification of the Centers for Disease Control and the following parameters reflecting polyclonal B cell activation were evaluated in these patients: immunoglobulin levels, circulating immune complexes and occurrence of autoantibodies. The results reported here indicate that intense polyclonal B cell activation occurs in both asymptomatic (CDC 2) and symptomatic patients (CDC 3 and CDC 4). Moreover, serological abnormalities were detected with similar frequency in the three groups studied.

Malaria specific human T cell clones: crossreactivity with various plasmodia species

Peripheral blood mononuclear cells (PBMC) from donors with or without previous exposure to malaria in vivo were cultivated for 4 to 7 days in the presence of different malaria antigen (M.Ag) preparations: Plasmodium falciparum (P.f.Ag), P. berghei (P.b.Ag) and P. gallinaceum (P.g.Ag). All preparations induced a proliferative response in PBMC from donors with or without previous exposure to malaria. PBMC from both groups of donors were then primed with each of the three M.Ag and cloned in presence of autologous irradiated PBMC and M.Ag. All 152 clones recovered had the T4+ phenotype and required autologous antigen presenting cells (APC) in addition to M.Ag for proliferation. Species specific and crossreactive T cell clones (T cell clones proliferating in the presence of the three M.Ag preparations) were recovered following priming with each of the three M.Ag. Species specific and crossreactive T cell clones were recovered in similar percentages (approximately 50%) using PBMC from donors with or without previous exposure to malaria. These data are discussed in the context of crossreactivity at the T cell level among various plasmodia species and in relation to epitope recognition of malaria native, synthetic and fusion polypeptides.

Antigen-specific and MHC-restricted Plasmodium falciparum-induced human T lymphocyte clones

We established and analyzed human T lymphocyte clones induced by crude Plasmodium falciparum antigens of schizont-enriched asexual blood stages. Peripheral blood mononuclear cells (PBMC) were stimulated for 6 days with antigen, and the T cell blasts were separated and were transferred to limiting dilution cultures with antigen, irradiated PBMC, and recombinant interleukin 2. The following observations were made. Malaria antigen (M.Ag) induced similar proportions of T blasts in PBMC from infected individuals and noninfected controls, and the M.Ag-dependent clone frequencies (1/79 to 1/216) obtained with the blasts were similar. The majority of established clones derived from infected and noninfected subjects specifically recognized M.Ag and would not proliferate in response to red blood cells or autologous PBMC alone. They also required HLA class II determinant-compatible antigen-presenting (E-) cells. With three clones from one malaria patient, DR 1 or DR 5 specificities correlated with antigen presentation. Although T4+ and T8+ blasts were induced by M.Ag in PBMC, only T4 (Leu-3+) clones were obtained in our culture system. These clones secreted IL 2 in response to M.Ag. 4) Differential patterns of reactivity to native M.Ag, heat-stable antigens, and heat-precipitated antigens were exhibited by T cell clones, and the tested clones did not recognize Plasmodium berghei antigen. In conclusion, it is important with regard to previous observations on apparently nonspecific, mitogen-like effects of M.Ag in bulk T cell cultures that our results demonstrate specific recognition of P. falciparum by human T cells. The T cell clones obtained will be an important tool in the quest for a better understanding of the mechanisms involved in resistance to malaria infection.

Antigen-specific and MHC-restricted Plasmodium falciparum-induced human T lymphocyte clones

We established and analyzed human T lymphocyte clones induced by crude Plasmodium falciparum antigens of schizont-enriched asexual blood stages. Peripheral blood mononuclear cells (PBMC) were stimulated for 6 days with antigen, and the T cell blasts were separated and were transferred to limiting dilution cultures with antigen, irradiated PBMC, and recombinant interleukin 2. The following observations were made. Malaria antigen (M.Ag) induced similar proportions of T blasts in PBMC from infected individuals and noninfected controls, and the M.Ag-dependent clone frequencies (1/79 to 1/216) obtained with the blasts were similar. The majority of established clones derived from infected and noninfected subjects specifically recognized M.Ag and would not proliferate in response to red blood cells or autologous PBMC alone. They also required HLA class II determinant-compatible antigen-presenting (E-) cells. With three clones from one malaria patient, DR 1 or DR 5 specificities correlated with antigen presentation. Although T4+ and T8+ blasts were induced by M.Ag in PBMC, only T4 (Leu-3+) clones were obtained in our culture system. These clones secreted IL 2 in response to M.Ag. 4) Differential patterns of reactivity to native M.Ag, heat-stable antigens, and heat-precipitated antigens were exhibited by T cell clones, and the tested clones did not recognize Plasmodium berghei antigen. In conclusion, it is important with regard to previous observations on apparently nonspecific, mitogen-like effects of M.Ag in bulk T cell cultures that our results demonstrate specific recognition of P. falciparum by human T cells. The T cell clones obtained will be an important tool in the quest for a better understanding of the mechanisms involved in resistance to malaria infection.

In vivo time course of synthesis and processing of major schizont membrane polypeptides in Plasmodium falciparum

A rapid method of separating membrane co-sedimentable and soluble components of Plasmodium infected erythrocytes is presented. We propose a nomenclature for major P. falciparum polypeptides, applicable to different isolates and based on their cellular location and stage specificity. For four of these polypeptides (185 kDa = Mp1; 120 kDa = Mp3; 76 kDa = Mp5; 90 kDa= Sp2) supposed to play a role in protective immunity, monospecific antibodies were available. We have studied their fate at the time of merozoïte release and reinvasion, and the possible correlations between these polypeptides, by pulse-chase experiments.

[Paroxysmal nocturnal hemoglobinuria secondary to an extracorpuscular elutable factor (immunoglobulin)]

A case is reported of Coombs-negative hemolytic anemia in the form of transitory PNH associated with acquired immunohemolytic anemia (AIHA). The patient, a 43-year-old man, was admitted to hospital because of jaundice and hemoglobinuria. Investigations revealed hemolytic anemia with the characteristics of PNH (positive Ham test, 50% hemolysis with the sucrose test) and of AIHA (microspherocytosis, survival of isologous red blood cells t1/2 = 9.5 days). The titer of cold agglutinins was not significant. Pre-incubation of the patient's red blood cells with anti-human F (ab')2 caused marked inhibition of hemolysis during the sucrose test. Isologous red blood cells, pre-incubated with an eluate obtained from the patient's erythrocytes, became sensitive to hemolysis during the sucrose test. The sucrose test is pathognomonic for PHN. The "false" positivity in the present case is possibly due to an immunoglobin conferring on the erythrocytes the characteristic property of PNH cells by blocking the activity of the decay accelerating factor.

Identification and expression in Escherichia coli of merozoite stage-specific genes of the human malarial parasite Plasmodium falciparum

The key steps in the development of a malaria vaccine through gene cloning are the identification of the proteins involved in host protective immunity and the cloning, identification, and expression of the genes coding for these proteins. Recent data have indicated that certain proteins synthesized at the late schizont-merozoite stage of Plasmodium falciparum play a major role in malaria immunity. This paper reports the identification, in a cDNA library, of recombinant clones corresponding to genes expressed specifically during the late schizont-merozoite stage of P. falciparum development. The 132 cDNA clones thus identified out of 10,000 were found to correspond to only 12 different genes, probably representing most of the major schizont-merozoite specific genes. The stage-specific cDNAs can be efficiently expressed in Escherichia coli cells. The protein products of some of these clones are recognized by monoclonal antibodies specific for late schizont-merozoite proteins. We conclude that only a small set of genes is specifically induced in the schizont-merozoite stage and that the stage-specific cDNA clones we have isolated are very likely to include the genes coding for the immunologically relevant proteins of P. falciparum.

Species- and stage-specific antigens in exoerythrocytic stages of Plasmodium falciparum

Numerous exoerythrocytic forms of Plasmodium falciparum ( PFEEF ) were obtained from the liver of the South American monkey, Cebus apella, for analysis of the antigens on this stage. As antigen for the fluorescent assay, 5-micron sections of liver fragments collected on day 5 following sporozoite inoculation and fixed in Carnoy's solution or kept in liquid nitrogen were used. Two types of fluorescent labeling of the PFEEF were identified: diffuse and peripheral. Each of 23 sera from individuals with P. falciparum infection acquired naturally by mosquito bite showed the diffuse and peripheral patterns of fluorescence at low serum dilutions (i.e., 1:10-1:100), but only peripheral staining at higher serum dilutions (i.e., 1:200-1:1,600). All other polyclonal sera tested showed only the diffuse pattern of fluorescence whatever the serum dilution used; this was true for P. falciparum infections acquired accidentally by blood transfusion, heterologous human infections with P. vivax, P. ovale, P. malariae or P. cynomolgi, and experimental animal infections with P. berghei, P. gallinaceum, or P. cynomolgi. Fluorescent antibody titers on PFEEF were generally 1-4 dilutions lower than on blood stages. No age-dependent pattern of fluorescence titers was found in 30 sera from individuals ranging in age from 2-78 years living in a malaria-endemic area. Twenty-six monoclonal antibodies directed to P. falciparum blood stages which reacted at high titers with rings, schizonts, merozoites, and gametocytes did not react with PFEEF antigen even when using the undiluted ascitic fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

The diagnosis of malaria infection using a solid-phase radioimmunoassay for the detection of malaria antigens. Application to the detection of Plasmodium berghei infection in mice

A method has been devised to show that malaria parasites can be detected serologically in infected blood with a high degree of sensitivity. Using a murine malaria model, parasites were demonstrated in a solid-phase radio-immunoassay which measured antibody-binding inhibition. Lysed red blood cells (r.b.c.) were incubated with labelled specific antibody and were then reacted in antigen-coated tubes. The degree of inhibition of antibody binding in the tubes correlated with the level of parasitaemia in the test blood. Using homologous antisera the test detected infection at a level of 1 parasite/million r.b.c. The specificity of the method was shown by comparison of antibody-binding inhibition in normal and infected r.b.c. and in r.b.c. from non-infected mice with induced reticulocytosis. The sensitivity was shown in vitro in tests of serially diluted blood of high parasitaemia and in vivo for the detection of early infection. The presence of antibody in the test blood did not significantly affect the sensitivity of parasite detection.

[Pseudothrombopenia (proceedings)]

Two cases of spurious thrombocytopenia are reported, one induced by platelet satellitism and the other by platelet aggregation. These phenomena occur in vitro, only in the presence of EDTA and are linked with the presence of IgG in the patients' sera.

Quantitative Studies of the Conversion of C3PA (GBG) to C3A (GGG)

Quantitative methods were set up to measure the conversion of C3PA or GBG to C3A or GGG. The results were compared to those of hemolytic tests by using glutathion-treated red cells. The kinetics of C3PA conversion induced in serum either spontaneously by addition of magnesium, or by various natural activators, was studied. Particular interest was given to the activation of C3PA by immune complexes. It was found that some small complexes formed in large antigen excess can activate the C3A system. Similar results were obtained with complexes formed of IgA immunoglobulins and DNP-substituted antigens. The C3-converting activity of some “nephritic factors” isolated from sera of membrano-proliferative glomerulonephritis patients seems to be related to a similar activation process of the alternate pathway. (Work supported by Swiss National Research Foundation (Grant 3.617.71) and the Annette Kade Foundation.)