Human RNA Viruses - ICGEB

Differential Transactivation and Apoptotic
abilities of Vpr C variants: their Implication
in HIV Pathogenesis
1 Aalia S. Bano, 1 Vikas Sood, 1 Ujjwal Neogi, 2 Nidhi Goel,
2 Vijesh Sreedhar Kuttiat, 2 Ajay Wanchu and 1 Akhil C. Banerjea
1 National Institute of Immunology, New Delhi, India
2 Post Graduate Institute of Medical Education and Research, Chandigarh, India
e-mail: aalia@nii.res.in
For the development of effective vaccines and therapeutics we need to understand the biology
of HIV-1 pathogenesis with respect to different subtypes and recombinant strains. Vpr, an
accessory HIV-1 protein influences variety of cellular functions such as transactivation of the
long terminal repeat and certain heterologous promoters, nuclear import of preintegration
complexes, induction of cell cycle arrest in G2 phase, and induction of apoptosis in infected
cells. Most of these studies have been carried out with respect to the subtype B genes, while
the predominant HIV-1 strain circulating in India is subtype C. Information related to subtype
C Vpr is missing which is relavent in Indian context. Therefore, we carried out studies
regarding the transactivation potential, cellular viability and apoptotic abilities of Subtype C
Vpr (93In905, Indian isolate) gene. Vpr-C was able to cause transactivation moderately in
comparison to subtype B but effective laddering was observed in DNA isolated from HEK
293 cells transfected with Vpr C. The enhanced capability of Vpr C to induce apoptotic
laddering and cell death is being investigated further by computational biology approach.
Recently there have been reports of HIV-1 B/C recombinants from India. Thus a genetic and
functional analysis of the Vpr gene from HIV-1 infected individual from North India was
carried out. Vpr gene from 6 out of the 8 samples had an L64P mutation (located at the
predicted 3 rd alpha helix) while the other two were novel recombinants with genetic
architecture B/D-C-D-C and B/D-C-D-B. The recombinants were competent in causing
transactivation but the L64P mutants activated LTR promoter poorly. Also, the two
recombinants and the L64P mutants were able to cause a decrease in cell viability. Most of
our samples (7/8) possessed Q at position 77 which was earlier reported important for long
term non-progression and impaired induction of apoptosis for subtype B. This was clearly not
the case with all our infected individuals who showed normal progression to HIV/ AIDS. We
also engineered L64P mutation in subtype C background which adversely affected its ability
to transactivate. In contrast, L22A mutation in subtype C resulted in augmented LTR
transactivation-an observation common with subtype B. Thus our study highlights the
importance of studying Vpr biology with reference to evolving variants to understand the
pathophysiological outcome of this rapidly evolving virus.
32 � ICGEB–IUBMB Workshop on Human RNA Viruses
P6