A Noninfectious Simian/Human Immunodeficiency Virus DNA Vaccine That Protects Macaques against AIDS

Abstract

Simian/human immunodeficiency virus SHIV KU2 replicates with extremely high titers in macaques. In order to determine whether the DNA of the viral genome could be used as a vaccine if the DNA were rendered noninfectious, we deleted the reverse transcriptase gene from SHIV KU2 and inserted this DNA (⌬rtSHIV KU2 ) into a plasmid that was then used to test gene expression and immunogenicity. Transfection of Jurkat and human embryonic kidney epithelial (HEK 293) cells with the DNA resulted in production of all of the major viral proteins and their precursors and transient export of a large quantity of the Gag p27 into the supernatant fluid. As expected, no infectious virus was produced in these cultures. Four macaques were injected intradermally with 2 mg of the DNA at 0, 8, and 18 weeks. The animals developed neutralizing antibodies and low enzyme-linked immunospot assay (E-SPOT) titers against SHIV KU2 . These four animals and two unvaccinated control animals were then challenged with heterologous SHIV89.6P administered into their rectums. The two control animals developed viral RNA titers exceeding 10 6 copies/ml of plasma, and these titers were accompanied by the loss of CD4 ؉ T cells by 2 weeks after challenge. The two control animals died at weeks 8 and 16, respectively. All four of the immunized animals became infected with the challenge virus but developed lower titers of viral RNA in plasma than the control animals, and the titers decreased over time in three of the four macaques. The fourth animal remained viremic and died at week 47. Whereas the control animals failed to develop E-SPOT responses, all four of the immunized animals developed anamnestic E-SPOT responses after challenge. The animal that died developed the highest E-SPOT response and was the only one that produced neutralizing antibodies against the challenge virus. These results established that noninfectious DNA of pathogenic SHIV could be used as a vaccine to prevent AIDS, even though the immunological assays used did not predict the manner in which the challenge virus would replicate in the vaccinated animals.

Characterization of T-Cell Responses in Macaques Immunized with a Single Dose of HIV DNA Vaccine

“…However, enzyme-linked immunospot (ELISPOT) assay responses to HIV antigens before challenge were sporadic and weak (35,54). In contrast, T-cell responses specific to HIV antigens induced by our construct in immunized mice were substantially higher (21).…”

“…AY751799) and from HIV-1 SF2. The strategy of the construction of ⌬4SHIV KU2 plasmid DNA has been described previously (21,35,54). This construct carries vpx and vpr genes of SIVmac239 and gag, pro, vpu, tat, rev, env, and nef genes of HIV-1 under the transcriptional control of the SIV 5Ј LTR promoter and the poly(A) sequences of simian virus 40 (SV40).…”

Phenotypic and Functional Analysis of Immune CD8+ T Cell Responses Induced by a Single Injection of a HIV DNA Vaccine in Mice

“…The construction procedures of SHIV KU2 plasmid DNA have been described earlier (18). The inserted sequences were derived from SHIV KU2 (GenBank accession no.…”

Vaccination of Cats with Attenuated Feline Immunodeficiency Virus Proviral DNA Vaccine Expressing Gamma Interferon

“…DNA immunization has emerged as a promising approach to the development of HIV type 1 vaccines based on the induction of potent virusspecific cellular immune responses observed in DNA vaccine trials in both mice and nonhuman primates (2,18). Studies testing particular proviral DNA or multiplasmid DNA vaccines in nonhuman primates revealed protection from either virus load or disease after challenge with pathogenic virus isolates (14,19,29,34,37). Our previous studies revealed that immunization of cats with plasmid DNA containing an FIV provirus with a vif gene deletion (FIV-pPPR⌬vif) that has been shown to produce a highly attenuated virus (26) resulted in protection against infection with the wild-type (WT) homologous FIV isolate (25).…”