Ewert Linder

Fibroblast surface antigen: A new serum protein

Abstract Material solubilized from the surface of cultured chick embryo fibroblasts contains a major antigen also present in normal chicken serum. Fluorescent antiserum stains the fibroblast membrane but not that of other cells. The antigen is synthesized by fibroblasts. [ 35 S]Methionine is incorporated into the molecule in cell cultures and the antigen is present in cells cultivated in heterologous serum for an extended period of time. In serum it has a high molecular weight and is an α-globulin. It seems to be a previously unrecognized serum protein. We suggest the name fibroblast surface antigen for it.

Free-living amoebae promote growth and survival of Helicobacter pylori

Transmission routes of Helicobacter pylori remain poorly understood. The finding of bacterial DNA in water suggests the involvement of environmental factors. Here we report successful co-cultivation of H. pylori with Acanthamoeba castellanii, which circumvents the requirement of this bacterium for precise microaerobic conditions and a large supply of nutrients in order to grow. H. pylori was able to propagate and remain viable for several weeks in the presence of amoebae under experimental conditions. Intact, metabolically active bacteria could be demonstrated in vacuoles. The putative dependence of H. pylori on free-living amoebae in nature could be important with respect to transmission and prevalence, as shown for some other pathogenic bacteria.

Uptake and replication of Salmonella enterica in Acanthamoeba rhysodes

ABSTRACT The ability of salmonellae to become internalized and to survive and replicate in amoebae was evaluated by using three separate serovars of Salmonella enterica and five different isolates of axenic Acanthamoeba spp. In gentamicin protection assays, Salmonella enterica serovar Dublin was internalized more efficiently than Salmonella enterica serovar Enteritidis or Salmonella enterica serovar Typhimurium in all of the amoeba isolates tested. The bacteria appeared to be most efficiently internalized by Acanthamoeba rhysodes. Variations in bacterial growth conditions affected internalization efficiency, but this effect was not altered by inactivation of hilA, a key regulator in the expression of the invasion-associated Salmonella pathogenicity island 1. Microscopy of infected A. rhysodes revealed that S. enterica resided within vacuoles. Prolonged incubation resulted in a loss of intracellular bacteria associated with morphological changes and loss of amoebae. In part, these alterations were associated with hilA and the Salmonella virulence plasmid. The data show that Acanthamoeba spp. can differentiate between different serovars of salmonellae and that internalization is associated with cytotoxic effects mediated by defined Salmonella virulence loci.

Autoantibody to “intermediate filaments” in infectious mononucleosis

Abstract By employing indirect immunofluorescent staining we detected autoantibodies against circulating lymphoblasts in the sera of two patients with acute infectious mononucleosis (IM). The target structures were identified as intermediate filaments (IMF) by their antigenic and biochemical properties. High titers of anti-IMF autoantibody were detected in 32 of 48 (67%) IM patient sera but not in control sera. The antibodies were usually of IgM class. The presence of anti-IMF antibodies did not correlate with anti-smooth muscle antibodies, and absorption studies revealed that the specificity of these antibodies differed from that of heterophilic (Paul-Bunnell) antibodies. The results may be interpreted as suggesting that the rapid turnover of lymphocytes in IM may be associated with a release of autoimmunogenic cytoplasmic intermediate(-sized) filaments.

A Solid Phase Enzyme‐linked Immunosorbent Assay (ELISA) for the Demonstration of Antibodies against Denatured, Single‐stranded DNA in Patient Sera

A solid phase enzyme‐linked‐immunosorbent assay (ELISA) for the determination of antibodies against denatured, single‐stranded (ss‐) DNA is described. Polystyrene cuvettes coated with ss‐DNA were incubated with serum samples and the anti‐ss‐DNA antibodies bound were detected by means of an anti‐IgG‐alkaline phosphatase conjugate. The binding of anti‐ss‐DNA antibodies in individual sera was expressed as units calculated as % of the absorbance in relation to the absorbance value obtained with a reference pool. Absorption experiments showed that the assay is specific for antibodies against denatured DNA. By using immunologically purified anti‐ss‐DNA antibodies the assay was shown Co detect specific antibodies in concentrations down to 1 ng/ml. Antibodies against DNA could be detected in 94% of sera with antinuclear antibodies.

Intestinal parasites in HIV-2 associated AIDS cases with chronic diarrhoea in Guinea-Bissau.

Previous studies from African countries where HIV-1 infection is prevalent have shown that infections with Cryptosporidium parvum, Isospora belli and microsporidia are frequently associated with chronic diarrhoea in AIDS patients. The information about the occurrence of these parasites in HIV-2 associated AIDS cases with chronic diarrhoea is limited. We have performed a study of stool parasites in patients from Guinea-Bissau, the country with the highest prevalence of HIV-2 in the world. Stool specimens from 52 adult patients with chronic diarrhoea of which 37 were HIV-positive and fulfilling the clinical criteria of AIDS (five HIV-1, 28 HIV-2 and four dually infected with HIV-1 and HIV-2) were screened for parasitic infections. Twenty five percent of the HIV-2 positive patients were infected with C. parvum, 11% with I. belli and 11% with microsporidia, all three parasites were seen only in HIV-positive patients. The three patients with microsporidiosis, all HIV-2 infected, are to our knowledge the first cases reported from Guinea-Bissau. Other stool parasites such as Blastocystis hominis, hookworm and Strongyloides stercoralis were observed both among HIV-positive and HIV-negative patients.

Detection of Pneumocystis carinii DNA by filtration of air.

The high incidence of pneumonia caused by Pneumocystis carinii in immunosuppressed patients makes it the most important parasite in non-tropical geographical regions. It has recently been shown to be a fungus, but several aspects of this organism are still poorly understood. A major question of clinical relevance is the nature of transmission and, thereby, the related problem of prevention. The mode of P. carinii transmission is thought to be air, but this is based on circumstantial evidence, the transmissive stage has not been identified. We attempted to capture P. carinii by filtration of air in the vicinity of cages containing P. carinii infected Wistar rats. Using nested polymerase chain reaction amplification of the thymidylate synthase gene to demonstrate P. carinii we were able to demonstrate P. carinii DNA on such filters. This strongly supports the suggested mechanism of transmission of Pneumocystis by means of airborne spores and suggests an approach to their isolation and characterization.

Characterization of human smooth muscle autoantibodies reacting with cytoplasmic intermediate filaments.

Abstract Human smooth muscle antibodies (SMA) reacting with cytoplasmic intermediate filaments were characterized by the indirect immunofluorescence technique. These antibodies were noted to comprise a major type of SMA. When cultured human embrynic fibroblasts treated with a microtubulus-disrupting drug, vinblastine, were used, the SMA reacting with intermediate filaments (IMF-SMA), could be readily distinguished from other types of SMA by the immunofluorescence staining pattern. Absorption studies with intermediate filaments prepared from cultured human embryonic fibroblasts and from bovine smooth muscle tissue indicated that there are more than one autoantigen in the intermediate filaments of smooth muscle. The major subunit protein of intermediate filaments having a molecular weight of 55,000 was enriched in the antigenically active preparations of intermediate filaments. Five of 26 patients positive for IMF-SMA had signs of liver diseases and only two had chronic hepatitis.

Antibodies in Mother's Milk Protect Children Against Giardiasis

The protective effect of anti-Giardia antibodies in mothers milk on the acquisition of Giardia infection in their children during the first 2 y of life was analysed as part of a prospective study on infant diarrhoea in a group of 307 mothers and children in Leòn, Nicaragua. Among 24 children acquiring infection within the first 6 months, 23 were born to mothers lacking antibodies. These children also developed more severe diarrhoea. A significant difference between children born to mothers with and without antibodies with respect to the age at which the first Giardia infection was acquired was demonstrated by survival analysis and log rank test (p=0.036). In conclusion, children born to non-immune mothers are at significantly higher risk of acquiring Giardia infection and developing giardiasis with more severe symptoms compared with children of immune mothers.

Seroepidemiology of Toxoplasma gondii among pregnant women in different parts of Sweden

Surveys of pregnant women in four areas of Sweden in 1987–88, reveal a significant trend for decrease inToxoplasma seroprevalence from Gotland island (26%, n=467) in the south through Örebro county (18%, n=1413) and Stockholm area (18%, n=939), to Northern Sweden (12%, n=837). No within area differences were observed between samples from rural and urban localities. Quantitative antibody data indicate marginally higher levels in the north than in the south, and a significant declining trend by age only in Örebro county. Incidence models are used to describe age-seroprevalence profiles for each area, using different assumptions about age- and time-specific infection rates, and to estimate the risk of maternal infection at the time of the survey. It is shown that the patterns of seroprevalence with age in Örebro county and Northern Sweden, but not Gotland island or Stockholm, strongly implicate time-dependent changes inToxoplasma incidence, consistent with a declining incidence in the past which has possibly been reversed in recent years. The estimates ofToxoplasma incidence and risk of maternal toxoplasmosis are strongly dependent upon the underlying assumption of temporal change in incidence, with wide ranges in the predicted values. These studies demonstrate the difficulties in interpretation of horizontal cross-sectional data and the need for longitudinal studies of age-prevalence and seroconversion in the determination of the true risk of maternal toxoplasmosis.