Replicating Ad-recombinants encoding non-myristoylated rather than wild-type HIV Nef elicit enhanced cellular immunity.
OBJECTIVE
To determine if immunization with non-myristoylated nef would elicit enhanced cellular immune responses resulting from improved presentation of Nef peptides by MHC-I on the cell surface, and enhanced T-cell help.


METHODS
The myristoylation site of HIV and SIV Nef is required for several Nef functions that modulate the immune response in an infected host, including downregulation of MHC-I, MHC-II, and CD4, and increased expression of the invariant chain on the cell surface. We constructed replication-competent Ad5- and Ad7-HIV recombinants encoding wild-type nef (nefWT) or a nef mutant (nefNM) lacking 19 amino-terminal amino acids, including the myristoylation site, and sequentially immunized chimpanzees mucosally, first with Ad5-HIVnef recombinants and subsequently with Ad7-HIVnef recombinants.


METHODS
Peripheral blood lymphocytes were evaluated over the immunization course for Nef-specific cellular immune responses by interferon (IFN)-gamma ELISPOT and T-cell proliferation assays. Nef-specific CD4 and CD8 memory T cells that produced intracellular IFN-gamma, interleukin-2, and tumor necrosis factor (TNF)-alpha were assessed by flow cytometry.


RESULTS
In comparison to immunization with Ad-HIVnefWT, Ad-HIVnefNM elicited statistically significant increases in numbers of IFN-gamma-secreting cells after the Ad7-HIVnefNM immunization and increased T-cell proliferative responses following both Ad5- and Ad7-HIVnefNM immunizations. Nef-specific CD4 and CD8 memory T-cell populations secreting TNF-alpha were also significantly increased in the Ad-HIVnefNM immunization group.


CONCLUSIONS
The results support the hypothesis that immunization with Ad-recombinants encoding HIVnefNM rather than HIVnefWT elicits enhanced cellular immunity resulting from improved antigen presentation and greater T-cell help.
Peng
Bo
B
Vaccine Branch, Center for Cancer Research, National Cancer Institute, 41 Medlars Drive, Bethesda, MD 20892, USA.
Voltan
Rebecca
R
Cristillo
Anthony D
AD
Alvord
W Gregory
WG
Davis-Warren
Alberta
A
Zhou
Qifeng
Q
Murthy
Krishna K
KK
Robert-Guroff
Marjorie
M
D016915:AIDS Vaccines; D000256:Adenoviridae; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D015536:Down-Regulation; D005260:Female; D015693:Gene Products, nef / Q000276:immunology*; D015658:HIV Infections / Q000276:immunology*; D007111:Immunity, Cellular; D007156:Immunologic Memory; D008297:Male; D002679:Pan troglodytes; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D054311:nef Gene Products, Human Immunodeficiency Virus
D016915:AIDS Vaccines; D015693:Gene Products, nef; D014409:Tumor Necrosis Factor-alpha; D054311:nef Gene Products, Human Immunodeficiency Virus