Protective effects of nef-deleted SHIV or that having IFN-? against disease induced with a pathogenic virus early after vaccination

Protective Efficacy of Nonpathogenic Nef-Deleted SHIV Vaccination Combined with Recombinant IFN-γ Administration against a Pathogenic SHIV Challenge in Rhesus Monkeys

We previously reported that a nef-deleted SHIV (SHIV-NI) is nonpathogenic and gave macaques protection from challenge infection with pathogenic SHIV-C2/1. To investigate whether IFN-gamma augments the immune response induced by this vaccination, we examined the antiviral and adjuvant effect of recombinant human IFN-gamma (rIFN-gamma) in vaccinated and unvaccinated monkeys. Nine monkeys were vaccinated with nef-deleted nonpathogenic SHIV-NI. Four of them were administered with rIFN-gamma and the other five monkeys were administered with placebo. After the challenge with pathogenic SHIV-C2/1, CD4(+) T-cell counts were maintained similarly in monkeys of both groups, while those of the unvaccinated monkeys decreased dramatically at 2 weeks after challenge. However, the peaks of plasma viral load were reduced to 100-fold in SHIV-NI vaccinated monkeys combined with rIFN-gamma compared with those in SHIV-NI vaccinated monkeys without rIFN-gamma. The peaks of plasma viral load were inversely correlated with the number of SIV Gag-specific IFN-gamma-producing cells. In SHIV-NI-vaccinated monkeys with rIFN-gamma, the number of SIV Gag-specific IFN-gamma-producing cells of PBMCs increased 2-fold compared with those in SHIV-NI-vaccinated monkeys without rIFN-gamma, and the NK activity and MIP-1alpha production of PBMCs were also enhanced. Thus, vaccination of SHIV-NI in combination with rIFN-gamma was more effective in modulating the antiviral immune system into a Th1 type response than SHIV-NI vaccination alone. These results suggest that IFN-gamma augmented the anti-viral effect by enhancing innate immunity and shifting the immune response to Th1.

Lack of differences in HIV-1 nef functional domains in infected chinese blood donors at different stages of disease

HIV-1 nef regions were amplified by polymerase chain reaction and sequenced from DNA samples of five asymptomatic subjects and five AIDS patients from a cohort of HIV-1-infected Chinese plasma and blood donors. Sequence analysis revealed that regardless of the stage of disease, each patient's HIV-1 nef sequences belonged to the clade B' subtype. Although there are some differences between the sequences from different patients, no significant differences have been detected in nef nucleotide sequences or functional motifs in the deduced amino acid sequences from patients at different stages of the disease. Furthermore, the predicted binding motifs of HLA-A2 and HLA-A11 were highly conserved among patient nef sequences. These results will contribute to a better understanding of the pathogenesis of circulating HIV-1 in infected Chinese former blood donors and may have important implications in developing an epitope-based vaccine suitable for Chinese blood donors.

Contribution of monocytes to viral replication in macaques during acute infection with simian immunodeficiency virus

Monocytes are known as an alternative target for HIV/SIV infection, but the contribution of monocytes to viral spread in a host is unclear. In this study, CD14 monocytes were monitored in 6 macaques until six weeks postinfection (wpi) with SIVmac239 to evaluate their contribution to viral load. The monocyte count in blood significantly increased with peak viremia at 2 wpi and the expression level of CD14 on monocytes significantly decreased at 1-2 wpi, though the number of CD4(+) T cells was stable in these macaques. The number of CD14 monocytes and the expression level of CD14 on monocytes at 2 wpi were also significantly related to the extent of viremia in plasma. An increased number of monocytes at 2 wpi was associated with a lower postacute viral load, suggesting that monocytes have a role in suppressing the virus. The lower expression level of CD14 in monocytes at 2 wpi was associated with a higher viral load and greater degree of infection of monocytes. This correlation suggests that monocytes with a low level of CD14 may be more susceptible to SIV and may enhance viral replication. The analysis of monocytes in persistently infected macaques revealed that the expression level of CD14 was also significantly low during persistent infection compared with naïve macaques, though the monocyte count was within the normal range. Monocytes may suppress viruses, perhaps by their immune function, during acute infection. However, infection of monocytes may increase the viral load and spread viruses in a host.

Virus-like particles: designing an effective AIDS vaccine

Viruses that infect eukaryotic organisms have the unique characteristic of self-assembling into particles. The mammalian immune system is highly attuned to recognizing and attacking these viral particles following infection. The use of particle-based immunogens, often delivered as live-attenuated viruses, has been an effective vaccination strategy for a variety of viruses. The development of an effective vaccine against the human immunodeficiency virus (HIV) has proven to be a challenge, since HIV infects cells of the immune system causing severe immunodeficiency resulting in the syndrome known as AIDS. In addition, the ability of the virus to adapt to immune pressure and reside in an integrated form in host cells presents hurdles for vaccinologists to overcome. A particle-based vaccine strategy has promise for eliciting high titer, long-lived, immune responses to a diverse number of viral epitopes against different HIV antigens. Live-attenuated viruses are effective at generating both cellular and humoral immune responses. However, while these vaccines stimulate immunity, challenged animals rarely clear the viral infection and the degree of attenuation directly correlates with protection from disease. Further, a live-attenuated vaccine has the potential to revert to a pathogenic form. Alternatively, virus-like particles (VLPs) mimic the viral particle without causing an immunodeficiency disease. VLPs are self-assembling, non-replicating, non-pathogenic particles that are similar in size and conformation to intact virions. A variety of VLPs for lentiviruses are currently in preclinical and clinical trials. This review focuses on our current status of VLP-based AIDS vaccines, regarding issues of purification and immune design for animal and clinical trials.

A genetically engineered live-attenuated simian-human immunodeficiency virus that co-expresses the RANTES gene improves the magnitude of cellular immunity in rhesus macaques

Regulated-on-activation-normal-T-cell-expressed-and-secreted (RANTES), a CC-chemokine, enhances antigen-specific T helper (Th) type-1 responses against HIV-1. To evaluate the adjuvant effects of RANTES against HIV vaccine candidate in SHIV-macaque models, we genetically engineered a live-attenuated SHIV to express the RANTES gene (SHIV-RANTES) and characterized the virus's properties in vivo. After the vaccination, the plasma viral loads were same in the SHIV-RANTES-inoculated monkeys and the parental nef-deleted SHIV (SHIV-NI)-inoculated monkeys. SHIV-RANTES provided some immunity in monkeys by remarkably increasing the antigen-specific CD4+ Th cell-proliferative response and by inducing an antigen-specific IFN-gamma ELISpot response. The magnitude of the immunity in SHIV-RANTES-immunized animals, however, failed to afford greater protection against a heterologous pathogenic SHIV (SHIV-C2/1) challenge compared to control SHIV-NI-immunized animals. SHIV-RANTES immunized monkeys, elicited robust cellular CD4+ Th responses and IFN-gamma ELISpot responses after SHIV-C2/1 challenge. These findings suggest that the chemokine RANTES can augment vaccine-elicited, HIV-specific CD4+ T cell responses.

Vaccination of cats with attenuated feline immunodeficiency virus proviral DNA vaccine expressing gamma interferon

A feline immunodeficiency virus (FIV) provirus with a vif gene deletion (FIVDelta vifATGgamma) that coexpresses feline gamma interferon (IFN-gamma) was tested as a proviral DNA vaccine to extend previous studies showing efficacy with an FIV-pPPRDelta vif DNA vaccine. Cats were vaccinated with either FIVDelta vifATGgamma or FIV-pPPRDelta vif proviral plasmid DNA or with both FIV-pPPRDelta vif DNA and a feline IFN-gamma expression plasmid (pCDNA-IFNgamma). A higher frequency of FIV-specific T-cell proliferation responses was observed in cats immunized with either FIVDelta vifATGgamma or FIV-pPPRDelta vif plus pCDNA-IFNgamma, while virus-specific cytotoxic-T-lymphocyte responses were comparable between vaccine groups. Antiviral antibodies were not observed postvaccination. Virus-specific cellular and humoral responses were similar between vaccine groups after challenge with a biological FIV isolate (FIV-PPR) at 13 weeks postimmunization. All vaccinated and unvaccinated cats were infected after FIV-PPR challenge and exhibited similar plasma virus loads. Accordingly, inclusion of plasmids containing IFN-gamma did not enhance the efficacy of FIV-pPPRDelta vif DNA immunization. Interestingly, the lack of protection associated with FIV-pPPRDelta vif DNA immunization contrasted with findings from a previous study and suggested that multiple factors, including timing of FIV-pPPRDelta vif inoculations and challenge, as well as route of challenge virus delivery, may significantly impact vaccine efficacy.

Induction of immune response in macaque monkeys infected with simian-human immunodeficiency virus having the TNF-alpha gene at an early stage of infection

TNF-alpha has been implicated in the pathogenesis of, and the immune response against, HIV-1 infection. To clarify the roles of TNF-alpha against HIV-1-related virus infection in an SHIV-macaque model, we genetically engineered an SHIV to express the TNF-alpha gene (SHIV-TNF) and characterized the virus's properties in vivo. After the acute viremic stage, the plasma viral loads declined earlier in the SHIV-TNF-inoculated monkeys than in the parental SHIV (SHIV-NI)-inoculated monkeys. SHIV-TNF induced cell death in the lymph nodes without depletion of circulating CD4(+) T cells. SHIV-TNF provided some immunity in monkeys by increasing the production of the chemokine RANTES and by inducing an antigen-specific proliferation of lymphocytes. The monkeys immunized with SHIV-TNF were partly protected against a pathogenic SHIV (SHIV-C2/1) challenge. These findings suggest that TNF-alpha contributes to the induction of an effective immune response against HIV-1 rather than to the progression of disease at the early stage of infection.