Cloning of gag gene of HIV-1 subtype C (Indian strain) into a mammalian expression vector and in vitro expression studies.
OBJECTIVE
Acquired immunodeficiency syndrome caused by HIV-1 is one of the biggest health problems we are facing today. It is required to concentrate efforts towards designing a safe, effective and affordable vaccine candidate in the context of the growing epidemic worldwide. Recently the approach of DNA based immunogen has evoked a lot of enthusiasm in the preclinical models.


METHODS
This study was designed towards a subtype C based gag DNA construct in the expression vector pJW4304. The gag and protease genes of HIV-1 subtype C were cloned into a mammalian expression vector pJW4304. The cloning strategy was designed so as to express a naturally processed form of the protein. Expression of gag protein by the construct pJWgagprotease49587 was evaluated by western blotting, p24 antigen capture ELISA and electron microscopy.


RESULTS
Gag p24 was detected both in the supernatant and in the transfected cells. Extra cellular p24 protein was estimated by p24 antigen capture ELISA. Immunoblotting using HIV positive polyclonal sera further confirmed the expression and processing of gag gene. The 24kDa band has been observed in cell lysates, which indicates that the proper processing is taking place in the presence of protease. Virus like particles were seen budding from the cell membrane 24 and 48 hours post transfection by transmission electron microscopy.


CONCLUSIONS
The recombinant construct pJWgagprotease49587 has shown good expression in vitro and therefore is a good candidate to study immunogenicity of the construct. Immunogenicity testing in mice is being carried out currently with this construct.
Chugh
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Department of Microbiology, All India Institute of Medical Sciences, New Delhi - 110 029, India.