HLA-A*01 allele: a risk factor for dengue haemorrhagic fever in Brazil's population

Severe forms of dengue, such as dengue haemorrhagic fever (DHF) and dengue shock syndrome, are examples of a complex pathogenic mechanism in which the virus, environment and host immune response interact. The influence of the host's genetic predisposition to susceptibility or resistance to infectious diseases has been evidenced in several studies. The association of the human leukocyte antigen gene (HLA) class I alleles with DHF susceptibility or resistance has been reported in ethnically and geographically distinct populations. Due to these ethnic and viral strain differences, associations occur in each population, independently with a specific allele, which most likely explains the associations of several alleles with DHF. As the potential role of HLA alleles in the progression of DHF in Brazilian patients remains unknown, we then identified HLA-A alleles in 67 patients with dengue fever and 42 with DHF from Rio de Janeiro, Brazil, selected from 2002-2008 by the sequence-based typing technique. Statistical analysis revealed an association between the HLA-A*01 allele and DHF [odds ratio (OR) = 2.7, p = 0.01], while analysis of the HLA-A*31 allele (OR = 0.5, p = 0.11) suggested a potential protective role in DHF that should be further investigated. This study provides evidence that HLA class I alleles might be important risk factors for DHF in Brazilian patients

Nationwide surveillance program to identify diarrhea-causing Escherichia coli in children in Thailand

Escherichia coli strains isolated from children with diarrhea were collected from 16 hospitals in different districts in Thailand during 1985 and 1986 and submitted to the National Reference Laboratory. Isolates were identified by serogrouping or as enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC) adhesin factor (EAF) E. coli, or Shiga-like-toxin (SLT)-producing E. coli by DNA hybridization. EPEC strains of known serogroups were isolated from 10%, ETEC strains were isolated from 6%, EAF E. coli strains were isolated from 4%, EIEC strains were isolated from less than 1%, and SLT-producing E. coli strains were isolated from none of 393 children with diarrhea. Among 278 children whose ages were recorded, the highest rate of isolation of EAF E. coli was 11% (9 of 85) from children less than 6 months old. ETEC was isolated from 5% (4 of 85) of children less than 6 months old, from 10% (12 of 118) of children 6 to 23 months old, and from 1% (1 of 75) of children greater than 23 months old. EPEC strains of known serogroups were isolated from 18% (15 of 85) of children less than 6 months old, from 11% (13 of 118) of children 6 to 23 months old, and from 9% (7 of 75) of children greater than 23 months old. E. coli strains that hybridized with the EIEC probe were isolated from three children who were 20, 36, and 48 months old. Examining E. coli for hybridization with DNA probes for virulence determinants is a practical way of conducting nationwide surveillance of diarrhea-causing E. coli. Since only 33% (13 of 39) of EPEC serogroups hybridized with the EAF probe and none hybridized with the SLT probes, identification of EPEC by serogroups analysis, followed by serotyping, should continue to be used in the identification of EPEC.</jats:p