Browsing by Author "LOBOS, SR"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    ANTIBODIES TO PORIN ANTIGENS OF SALMONELLA-TYPHI INDUCED DURING TYPHOID INFECTION IN HUMANS
    (1986) CALDERON, I; LOBOS, SR; ROJAS, HA; PALOMINO, C; RODRIGUEZ, LH; MORA, GC
    Immunoglobulin G (IgG-)- and IgM-specific antibody titers against Salmonella typhi Ty2 porins have been measured in 30 paired typhoid sera by enzyme-linked immunosorbent assay. These studies have found that IgG serum titers of acute and convalescent sera were 625 and 5,000 times higher, respectively than the control serum titers. The same typhoid sera were titrated with S. typhi Ty2 flagellin and S. typhi lipopolysaccharide. The titers against these antigens were considerably lower than those against the porins. The highest IgM-specific titer has also been found against porins in convalescent-phase sera. However, the largest increase in IgM-specific titer compared with the control group titer was obtained against flagellin during the acute phase of typhoid. The lowest increases in antibody titer were obtained with the IgM-specific anti-lipopolysaccharide in both types of sera. This may be because many normal individuals in endemic areas already have IgM titers against lipopolysaccharide. This study has provided good evidence that porins are excellent antigens and that IgG-specific antiporin titers may be of diagnostic value in typhoid infections in endemic areas.
  • No Thumbnail Available
    Item
    CLINICAL ISOLATE OF A PORINLESS SALMONELLA-TYPHI RESISTANT TO HIGH-LEVELS OF CHLORAMPHENICOL
    (1990) TORO, CS; LOBOS, SR; CALDERON, I; RODRIGUEZ, M; MORA, GC
  • No Thumbnail Available
    Item
    THE HEMOLYTIC EFFECT OF SALMONELLA-TYPHI TY-2 PORINS
    (1984) CALDERON, I; LOBOS, SR; MORA, GC
    Two outer membrane proteins of S. typhi Ty 2 were extensively co-purified. According to their migration in dodecylsulfate/polyacrylamide gel electrophoresis and solubility characteristics, these proteins are homologous to the 35-kDa (kilodalton) and 36-kDa porins found in S. typhimurium. A porin homologous to the 34-kDa one was not found in S. typhi Ty 2. A critical step in the purification of porins is heating at 100.degree. C in 2% sodium dodecyl sulfate before Sephadex gel filtration. The absence of detergent in aqueous suspensions enhances porin aggregation, these aggregations inducing human red cell lysis. Porins obtained by an alternative procedure consisting of heating at 60.degree. C instead of 100.degree. C were also hemolytic. Using nanomolar concentration of porins a strong influence of temperature on the hemolytic effect was observed. Porin-induced hemolysis was inhibited with anti-porin serum and by treatment with phenylglyoxal, which reacts with the arginine residues of proteins. The membrane-disrupting ability of porin aggregates might explain some pathogenic characteristics of gram-negative bacterial infections.