VPAC1 is a cellular neuroendocrine receptor expressed on T cells that actively facilitates productive HIV-1 infection.
OBJECTIVE
A lack of productive HIV-1 infection of Kit225 compared to Jurkat T cells, despite similar levels of CD4 and HIV-1 chemokine co-receptors, was found to correlate with the expression of vasoactive intestinal peptide/pituitary adenylate cyclase activating polypeptide receptor-1 (VPAC1). We therefore examined a role for this seven-transmembrane G protein-coupled neuroendocrine receptor in modulating HIV-1 infection.


METHODS
Reverse transcription-PCR was used to show the level of VPAC1 expression in different T-cell lines. A signal-blocking antibody to VPAC1 was used to examine its inhibiting effect on HIV-1 infection. Transfection of VPAC1 cDNA in both sense and anti-sense orientation was used to assess the role of VPAC1 in HIV-1 infection. HIV-1 infection was monitored by gag p24 ELISA using HIV-1IIIB or by luciferase activity using pseudo envelope-typed HXB2-NL4-3-luciferase. Analysis of HIV-1 gag DNA and 2-LTR circles was utilized to examine a possible mechanism for the effect of VPAC1.


RESULTS
Using VPAC1 signal blocking antibody, we showed that up to 80% of productive infection with HIV-1IIIB was inhibited. We also demonstrated that HIV-1 gp120 has sequence similarity to the natural ligand for VPAC1 and postulate that it can activate this receptor directly. Transfection of VPAC1 cDNA in the anti-sense orientation resulted in a significant loss, up to 50% of productive infection. In contrast, transfection of cells with VPAC1 in the sense orientation increased the productive infection by more than 15-fold and caused a profound increase in syncytium formation. Furthermore, stimulation of VPAC1 on primary cells facilitated in vitro infection with HIV-1 HXB2-NL4-3. Analysis of HIV-1 gag DNA indicated that VPAC1 does not affect viral entry; however, cells that show negligible expression of VPAC1 may not be productively infected as indicated by a lack of 2-LTR circle formation.


CONCLUSIONS
We have discovered a cellular receptor, VPAC1, that is a novel and potent facilitator of HIV-1 infection and thus, is a potentially important new target for therapeutic intervention.
Branch
Donald R
DR
Department of Medicine, Institute of Medical Science, University of Toronto, Ontario, Canada.
Valenta
Linda J E
LJ
Yousefi
Shida
S
Sakac
Darinka
D
Singla
Ruchi
R
Bali
Meenakshi
M
Sahai
Beni M
BM
Ma
Xue-Zhong
XZ
D001483:Base Sequence; D002460:Cell Line; D016373:DNA, Antisense / Q000235:genetics / Q000494:pharmacology; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D015699:HIV Envelope Protein gp120 / Q000276:immunology; D015658:HIV Infections / Q000209:etiology* / Q000517:prevention & control; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D019169:Jurkat Cells; D018005:Receptors, Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology* / Q000821:virology*
D016373:DNA, Antisense; D018076:DNA, Complementary; D015699:HIV Envelope Protein gp120; D018005:Receptors, Vasoactive Intestinal Peptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I