Risk of Helicobacter pylori infection among long-term residents in developing countries.

The seroprevalence and incidence of Helicobacter pylori infection were determined among 312 North American missionaries who were serving in developing countries between 1967 and 1984. The majority (81%) resided in sub-Saharan Africa. When initially evaluated, the missionaries had a mean age of 40 years, 65% were female, and all were of white race/ethnicity. An ELISA showed that the initial prevalence of IgG antibody to H. pylori was 17%. After a mean of 7.4 years of service (1917 person-years of exposure), 37 (14%) of 259 initially seronegative subjects seroconverted to anti-H. pylori, giving an annual incidence of 1.9%. These data indicate a relatively higher risk of H. pylori infection among missionaries compared with an annual incidence of seroconversion of 0.3-1.0% in industrialized nations. Long-term residents in developing countries should be evaluated for H. pylori infection when gastrointestinal symptoms develop.

Leishmanial protein kinases phosphorylate components of the complement system.

Externally oriented protein kinases are present on the plasma membrane of the human parasite, Leishmania. Since activation of complement plays an important role in the survival of these parasites, we examined the ability of protein kinases from Leishmania major to phosphorylate components of the human complement system. The leishmanial protein kinase-1 (LPK-1) isolated from promastigotes of L. major was able to phosphorylate purified human C3, C5 and C9. Only the alpha-chain of C3 and C5 was phosphorylated. The beta-chain appeared not to be a substrate for this enzyme. C3b which is formed by proteolytic cleavage of C3 was not phosphorylated by LPK-1. Trypsin treatment of phosphorylated C3 (P-C3) resulted in the disappearance of 32P from the alpha-chain. This was correlated with the conversion of the C3 alpha-chain to the alpha'-chain of C3b, and the appearance of a 9 kDa 32P fragment comigrating with the C3a fragment of C3. P-C3 was more resistant to cleavage by trypsin than nonphosphorylated C3. LPK-1 phosphorylated purified C3a and two synthetic peptides, C3a21R and YA-C3a10R, derived from its COOH-terminal end, which contain the C3a binding site to leukocytes and platelets. LPK-1 did not phosphorylate C3a8R. Phosphoamino acid analysis of the synthetic peptides indicated that serine 71 of C3a was phosphorylated by LPK-1. Treatment of C3 with either methylamine or freeze-thaw C3 (H2O) prevented phosphorylation by the LPK-1 suggesting that substrate conformation may be involved in recognition by the leishmanial enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for the existence of ganglioside molecules in the antigen of Entamoeba histolytica.

Gangliosides were found to be present in Entamoeba histolytica. They were extracted from lyophilized trophozoites of the pathogenic strain HM-1:IMSS and purified by high performance thin-layer chromatography. Two resorcinol-positive bands, comigrating with GM2 and GD1a were demonstrated, revealing the existence of ganglioside molecules in Entamoeba histolytica. The GM2 content, determined as lipid-bound sialic acid, was 1.5 micrograms/10(8) amoebae, the content of the GD1a comigrating band was 0.32 microgram/10(8) amoebae. The identity of the GM2 comigrating band was confirmed by TLC immunostaining, using the monoclonal anti-GM2 antibody GMB28. Furthermore, six out of ten anti-amoeba positive sera selectively reacted with the GM2 comigrating band, as revealed by immunostaining on TLC plates. Absorption tests revealed that preincubation of anti-amoeba positive sera with standard GM2 was followed by a significant decrease in the reaction with amoeba trophozoites by indirect immunofluorescence. These results demonstrate that a GM2 comigrating component of Entamoeba histolytica may be one of the antigens responsible for the appearance of circulating antibodies in patients with amoebiasis.

Childhood leukemia in Belarus before and after the Chernobyl accident: continued follow-up.

Earlier assessments led to the conclusion that due to the added radiation after the Chernobyl accident, childhood leukemia in Belarus was not recognisably increased in the years 1987-1994 compared to the years 1982-1986, i.e. the period before the accident. The present paper gives the data of the continued follow-up (1995-1998) which was conducted by the Institute of Haematology and Blood Transfusion, Minsk. In line with the earlier observations no increase has been identified. The incidence rates have been compared to the data of the newly established Belarussian Childhood Cancer Registry and a tentative explanation is given for apparent differences between the rates from our follow-up and the data reported earlier by the Belarussian Childhood Cancer Registry.

Protection of mice against Plasmodium yoelii sporozoite challenge with P. yoelii merozoite surface protein 1 DNA vaccines.

Immunization of mice with DNA vaccines encoding the full-length form and C and N termini of Plasmodium yoelii merozoite surface protein 1 provided partial protection against sporozoite challenge and resulted in boosting of antibody titers after challenge. In C57BL/6 mice, two DNA vaccines provided protection comparable to that of recombinant protein consisting of the C terminus in Freund's adjuvant.