Abstract:
Vaccinia recombinant virus carrying foreign gene insert sequences derived from
several infectious agents have been implicated in vaccine development or assays for humoral
and/or cell-mediated immune response. The present study aimed to: 1) construct a vaccinia
recombinant virus that contained HIV-1 gp41 DNA insert; and 2) apply this recombinant
virus in the test for CTL (Cytotoxic T lymphocyte) activity against gp41 epitopes by classic
51Cr released bulk culture killing assay in HIV infected cases.
HIV-1 strain DA5 CRF 01_ AE was used as the gene donor to provide gp41 DNA
portion of the Env gene. The gp41 DNA was amplified and the PCR products were cloned
into pGEM-T Easy plasmid, and subsequently introduced into E. coli competent cells to
generate numerous copies of gp41 DNA. Subsequently, the purified gp41 DNA was inserted
into pSC11, the expression plasmid vector designed especially for construction of vaccinia
recombinant viruses. Then, gp41/pSC11 recombinant vector was used to transfect TK- cells
that were pre-infected with the parental vaccinia virus, or wild-type vaccinia virus vaccine
strain Lister. The HIV-1 gp41 DNA is integrated into vaccinia virus genome by the
mechanism of homologous recombination. The recombinant virus was selected and purified
by plaque purification technique; and an expression of gp41 DNA insert was determined by
Western blot and indirect immunofluorescence.
The constructed HIV-1 gp41/vaccinia recombinant virus was applied to CTL assay in
HIV infected cases and compared with the other two recombinant vaccinia viruses containing
whole gp160 Env gene insert: vP1536 (containing gp160 derived from HIV-1 CRF01_AE)
and KPS-env (containing gp160 derived from HIV-1 strain DA5). The result showed that
frequency of HIV infected cases who had CTL activity against gp160 were equal, as assayed
either by one of the two HIV-1 gp160 recombinant viruses, i.e., 12 (63.2%) of 19 subjects
tested were positive. However, only 6 (50%) of these 12 cases had CTL activity to gp41
domain.
The study demonstrated the success in construction of HIV-1 gp41 recombinant
vaccinia virus that could be successfully applied to CTL assay. This provides implications in
the study on immune status in HIV infected cases and an evaluation of vaccine efficiency in an
immune induction in the vaccinees. In addition, it can be applied as a source of gp41 protein
screening antigen in monoclonal antibody research