Linkage disequilibrium between HLA-G*0104 and HLA-E*0103 alleles in Tswa Pygmies.

Nonclassical human leukocyte antigen (HLA)-G and -E loci are separated by approximately 660 kb on the short arm of chromosome 6. Interestingly, some functional and expression characteristics are relatively identical or associated for both molecules. For example, expression of HLA-E on the cell surface has been linked to preferential binding of nonameric leader peptides derived from the signal sequence of HLA-G. It has been suggested that these two molecules act synergistically in modulating susceptibility to infectious or chronic inflammatory diseases. A possible explanation for these observations is that HLA-E and HLA-G are evolving under analogous selective pressures and have functions that place them under selective regimes differing from classical HLA genes. The purpose of this study was to investigate the consistency of this hypothesis based on the characterization of the molecular polymorphism of these two genes and their linkage disequilibrium (LD) in three populations, i.e. Southeastern French (n = 57), Teke Congolese (n = 84) and Tswa Pygmies (n = 74). Allelic frequencies observed for HLA-G and HLA-E and for 14-bp ins/del polymorphism in the three populations were similar to those observed in the literature for populations from corresponding geographic areas. Only one of the recently described HLA-G polymorphisms (HLA-G*01:07-01:16) was found, i.e. HLA-G*01:15 in one individual from Congo. We showed that two haplotypes in Tswa Pygmies, i.e. HLA-G*01:04-E*01:03:01 and G*01:04-E*01:01, exhibited highly significant positive and negative D' values respectively. Although these LD could have functional implications, it is more likely because of the genetic drift as the two other populations did not display any significant LD.

Distribution of killer-cell immunoglobulin-like receptor (KIR) in Comoros and Southeast France.

Killer-cell immunoglobulin-like receptors (KIRs) expressed by natural killer cells are cell surface molecules able to recognize groups of HLA class I alleles. The number and distribution of KIR genes vary among individuals and populations. The aim of this study is to analyse the KIR gene content in a Comorian population in order to investigate genetic relationships with other populations and to reconstruct past migration events. The Comorian population consisted of 54 unrelated immigrants living in France and a control population consisted of 38 individuals from Southeast France. We investigated the presence or absence of 15 KIR genes, two pseudogenes expressed and non-expressed forms of KIR2DL5 and the two major subtype full-length and deleted forms of KIR2DS4. All individuals were typed positive for the framework genes, i.e. KIR2DL4, KIR3DL2 and KIR3DL3, and the two pseudogenes KIR3DP1 and KIR2DP1. The frequencies of full-length KIR2DS4 (*00101/00102/002) were lower in the French population (F = 29%) than in the Comorian population (F = 72%) (P(c) < 0.05). No significant differences were found for other KIR genes. A total of 11 genotypes were identified in the Southeast French population and 22 genotypes in the Comorian population. The most common genotype (2DL1, 2DL3, 2DL4, 3DL1, 3DL2, 3DL3 and 2DS4) accounted for 41% in the Comorian population and 34% in the Southeast French population. Principal component analysis using KIR gene data from 20 populations was performed to determine genetic differences and relations between populations. The Comorian population exhibited closest kinship with Africans and Asians. As KIR gene content is heterogeneous among ethnic groups, it can probably be used to assess the genetic relationships among populations from different geographic areas.

[Identification of Mycobacterium tuberculosis and Mycobacterium avium by non-radioactive probes: evaluation of the Snap Syngene system]. / Identification de Mycobacterium tuberculosis et des mycobactéries aviaires par sondes non radioactives: évaluation du système Snap Syngène.

We evaluated an alkaline phosphatase-labeled oligonucleotide probe for the rapid identification of Mycobacterium tuberculosis and mycobacteria belonging to the M avium and M intracellulare complex (MAIS). Sixty-two strains of mycobacteria and eight strains belonging to related genera were studied. All M tuberculosis strains hybridized with the tuberculosis probe. All M avium and M intracellulare gave a strong signal with their probes. However the 3 M xenopi strains tested hybridized with all probes for MAIS complex.

Susceptibility of Rickettsia conorii and R. rickettsii to pefloxacin, in vitro and in ovo.

The activity of pefloxacin against Rickettsia conorii and R. rickettsii was determined by several methods. The mean survival time of embryonated eggs infected with R. conorii was increased by pefloxacin 50 micrograms/egg; plaque formation in Vero cells was inhibited by 1 mg/l. In a microplate assay, the MIC of pefloxacin was 0.5 mg/l for R. conorii and 1 mg/l for R. rickettsii. The results support the use of pefloxacin in treating spotted fever rickettsioses.

In vitro susceptibility of Rickettsia conorii to ciprofloxacin as determined by suppressing lethality in chicken embryos and by plaque assay.

We tested the susceptibility of Rickettsia conorii to ciprofloxacin, a new quinolone antibiotic. A final concentration of 1 microgram/g of egg was effective in suppressing chicken embryo lethality, and a concentration of 0.25 micrograms/ml inhibited plaque formation in a plaque assay; however, a concentration of 0.5 microgram/ml was necessary to obtain rickettsiacidal activity. These results support the idea that ciprofloxacin could be of clinical use in treating Mediterranean spotted fever.