Résumé
Objective To study the variation and characteristics of HIV-1 tat exon 1 gene from a patient with AIDS dementia complex( ADC), so as to research the pathogenesis of ADC. Methods The tat gene was amplified with nested PCR from genomic DNA which was extracted from lymph node, spleen and different brain tissues( meninges, grey matter from frontal cortex, white matter from frontal cortex, temporal cortex and basal ganglia) of a patient who died of ADC. PCR products were cloned into the pGEM-T vector,after transformation and selection by ampicillin and blue/white spotting. Five of positive clones were sequenced. HIV-1 tat sequences were processed with BioEdit and MEGA4. With the softwares, Neighbor-Joining tree, p-Distances, values of ds/dn, and analysis of amino acid motifs were all done. Results The samples were all identified as HIV-1 B and genetic variation exists in HIV-1 tat isolated from different tissue;Compared with HXB2, sixteen sites of the amino acid seque nce coded by the HIV-1 tat gene which was isolated from the patient changed. In addition, part of the changes were different between periphery and brain,especially, the five Q54R changes from basal ganglia and one Q54R change from temporal cortex are deserve to follow with interest. Conclusion Variations exist in the HIV-1 tat genes extracted from the ADC patient and the variations from peripheral and central nerve tissues were different, whether the variations concerned with the pathogenesis of ADC need more research.
Résumé
Significant neurodegeneration leading to neurocognitive disorder and dementia has been observed in the central nervous system (CNS) of patients with HIV infection. Part of the neurodegenerative cascade in AIDS dementia may involve glial cells, perhaps through inhibiting the release of glial factors that protect neurons from variety of insults. Here, in an effort to find the mediators of HIV-induced brain damage, we examined the possible effect of a HIV-1 transmenbrane protein gp41 peptide (583-599) on expression and metabolism of amyloid precursor protein (APP) using human astroglial cell line. RT-PCR analysis demonstrated that gp 41 peptide did not significantly change expression patterns of APP mRNAs in lipopolysaccharide (LPS) activated astroglial cells for 6h. In contrast, gp41 peptide remarkably downregulated the level of secreted from of APP (sAPPa), which has been recently demonstrated as a potent neuroprotective factor. The reverse peptide, used as control had no such effect. The mechanism of gp41 peptide-induced down regulation of sAPPa production appears to be TGF-beta independent. These results implicate that gp41 peptide could be one of the mediator involved in the modulation of APP secretion within CNS, possibly contributing to the neuronal degeneration in HIV-1 associated neurological disease.