Browsing by Author "MORA, GC"

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    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.
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    CLINICAL ISOLATE OF A PORINLESS SALMONELLA-TYPHI RESISTANT TO HIGH-LEVELS OF CHLORAMPHENICOL
    (1990) TORO, CS; LOBOS, SR; CALDERON, I; RODRIGUEZ, M; MORA, GC
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    HETEROLOGOUS EXPRESSION OF ESCHERICHIA-COLI PORIN GENES IN SALMONELLA-TYPHI TY2 - REGULATION BY MEDIUM OSMOLARITY, TEMPERATURE AND OXYGEN AVAILABILITY
    (1995) CONTRERAS, I; MUNOZ, L; TORO, CS; MORA, GC
    Electrophoretic analysis of outer membrane proteins showed that Salmonella typhi OmpC expression is not reciprocally regulated relative to OmpF as described for Escherichia coli and S. typhimurium. When bacteria were grown in minimal media, both OmpC and OmpF were repressed as the osmolarity increased. However, in Luria broth, expression of OmpC was slightly induced by osmolarity up to 0.3 osmM, Plasmids bearing E. coli ompC-lacZ or ompF-lacZ gene fusions were studied for their expression in S. typhi and E. coli. Under anaerobic growth conditions, expression of ompC-lacZ in S. typhi was maximal at 0.16 osmM, while in E. coli expression was maximal at 0.7 osmM. ompF-lacZ expression was similarly repressed by medium osmolarity and anaerobiosis in both species. In contrast, a drastic difference in the regulation of OmpF by temperature was observed; at 37 degrees C ompF-lacZ expression was repressed in E. coli, while in S. typhi it was induced.
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    IMMUNOGENIC CAPACITY OF RIBOSOMES OF SALMONELLA-TYPHI INTERFERED WITH BY A FLAGELLIN-LIKE MATERIAL CONTAMINANT
    (1978) COFRE, G; CALDERON, I; MORA, GC
    The double-immunodiffusion technique and sodium dodecyl sulfate-polyacrylamide electrophoresis were used to demonstrate the presence of flagellin-like material strongly attached to ribosomes of S. typhi Ty 2. This flagellin-like material contaminating the ribosome preparation interfers with the induction of [rabbit] antiribosome serum, promoting the formation of antisera reacting either only with flagellin or in some cases with flagellin and ribosomes, but giving a very weak reaction with the latter. The interference is also observed when purified ribosomes from a nonflagellated mutant of S. typhi (S. typhi O-901) mixed with purified S. typhi Ty 2 flagellin are utilized as antigens. The antirosome sera obtained with ribosomes from S. typhi O-901 have a considerably higher titer than those that are interfered with. These sera were able to react with ribosomes obtained from several related species and did not react with flagella-derived flagellin of S. typhi Ty 2.
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    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.