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e so-called accessory genes of HIV have recently been found to be of
cance with roles in viral replication and pathogenesis. Th
e trans-membrane viral protein
U of HIV causes CD4 down-regulation and is also involved in release of the virus (as a counter
protein to overcome the host restriction by tetherin). Th
e present study was carried out to
determine the genetic characteristics of the trans-membrane and cytoplasmic domain of the
vpu protein of HIV during pregnancy. In addition we also studied BST-2 m-RNA expression at
the time of pregnancy and post-partum (preliminary results).
Materials and Methods:
Blood samples were obtained from 53 HIV sero-positive patients (28
from antenatal risk group; 22 from other risk groups; 3 samples post partum). Amplifi
gene was followed by sequencing. Sequence analysis was performed with the help of MEGA
and Bioedit. Homology modeling using Swift
Modeler was used to construct models from the
deduced amino acid sequences. VMD (Visual Molecular Dynamics) version 1.9 was used to
understand the molecular features of the membrane protein. Phylogenetic analysis based on
sequence and structural homology was carried ou
t. Sequence variability was also determined
using Entropy tool from Los Alamos Database. I-Mutant 2.0 and Membrane Protein Explorer
were used to study the eff
ect of mutations, stability and hydrophobicity of the trans-membrane
e mRNA expression levels of BST-2 were examined using Real Time PCR.
cant decrease in sequence variability in the pregnant risk group was observed.
Phylogenetic results confi
rmed that our isolates belonged to subtype C. Multiple structural
alignments of sequences from antenatal risk group revealed increased entropy in the trans-
membrane domain, whereas the cytoplasmic domain was much conserved. Structural homology
values indicated a higher structural simila
rity in the trans-membrane region as
compared to the cytoplasmic domain. Th
e post partum group exhibited mRNA expression of
BST-2, in contrast to its absence in other risk groups.
Pregnancy being an interferon depressed physiology, vpu doesn?t have to put much
ort to antagonize tetherin. It maintains a signifi
cantly conserved amino acid sequence with
the trans-membrane domain being comparatively more variable than the cytoplasmic domain,
but none of the variations in the amino acid sequence of the trans-membrane region alter the
protein structurally and therefore allows an optimum viral extrication. Th
e host restriction
protein BST-2 is able to counteract for the action of vpu post-partum. Th
e expression seems to
coincide with the beginning of the interferon induced physiology i.e. labor and post partum, a
host strategy to control virus release and alleviate the possibility of virus transmission at the time
of delivery when the fetus is in contact with maternal secretions, and also during breastfeeding.
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