Potent, Persistent Induction and Modulation of Cellular Immune Responses in Rhesus Macaques Primed with Ad5hr-Simian Immunodeficiency Virus (SIV) env/rev , gag , and/or nef Vaccines and Boosted with SIV gp120

Abstract

Immunity elicited by multicomponent vaccines delivered by replication-competent Ad5hr-simian immunodeficiency virus (SIV) recombinants was systematically investigated. Rhesus macaques were immunized mucosally at weeks 0 and 12 with Ad5hr-SIV smH4 env/rev, with or without Ad5hr-SIV mac239 gag or Ad5hr-SIV mac239 nef, or with all three recombinants. The total Ad5hr dosage was comparably adjusted among all animals with empty Ad5hr-⌬E3 vector. The macaques were boosted with SIV gp120 in monophosphoryl A-stable emulsion adjuvant at 24 and 36 weeks. Controls received Ad5hr-⌬E3 vector or adjuvant only. By ELISPOT analysis, all four SIV gene products elicited potent cellular immune responses that persisted 42 weeks post-initial immunization. Unexpectedly, modulation of this cellular immune response was observed among macaques receiving one, two, or three Ad5hr-SIV recombinants. Env responses were significantly enhanced throughout the immunization period in macaques immunized with Ad5hr-SIV env/rev plus Ad5hr-SIV gag and tended to be higher in macaques that also received Ad5hr-SIV nef. Macaques primed with all three recombinants displayed significant down-modulation in numbers of gamma interferon (IFN-␥)-secreting cells specific for SIV Nef, and the Env-and Gag-specific responses were also diminished. Modulation of antibody responses was not observed. Down-modulation was seen only during the period of Ad5hr-recombinant priming, not during subunit boosting, although SIV-specific IFN-␥-secreting cells persisted. The effect was not attributable to Ad5hr replication differences among immunization groups. Vaccine delivery via replication-competent live vectors, which can persistently infect new cells and continuously present low-level antigen, may be advantageous in overcoming competition among complex immunogens for immune recognition. Effects of current multicomponent vaccines on individual immune responses should be evaluated with regard to future vaccine design.

Vaccine-Elicited Antibodies Mediate Antibody-Dependent Cellular Cytotoxicity Correlated with Significantly Reduced Acute Viremia in Rhesus Macaques Challenged with SIVmac251

“…Protective efficacy has also been observed in rhesus macaques that have been challenged vaginally or rectally with pathogenic SIV (19,20,22,25). In our most recent Ad-SIV/gp120 vaccine efficacy study, a strong level of protection against an intrarectal SIV mac251 challenge was achieved (24,25). Notably, gp120-binding Ab titers and anti-envelope and anti-Rev cellular immune responses significantly correlated with reduced acute and setpoint viral loads, respectively (25).…”

Replicating adenovirus vector prime/protein boost strategies for HIV vaccine development

“…Significant Env, Rev, Gag and Nef specific cellular immune responses were elicited according to immunization groups throughout the priming and boosting phases of the vaccine regimen [93]. Interestingly, the addition of Ad5hr-SIVgag to the Ad5hr-HIVenv immunization regimen enhanced Env-specific responses, whereas Nef-specific responses were transiently downmodulated in the priming phase when all three recombinants were given together.…”

“…For example, chimpanzees have been administered 10 7 to 10 8 plaque forming units (pfu) intranasally [77,116,127] while a safe dose in humans is no more than 10 4 [128]. Similarly, using the Ad5hr vector in macaques, doses of 10 9 have been administered intranasally and intratracheally with no clinical consequences [88,93,102]. Duration of shedding of Ad vector in stool samples is also used to estimate Ad replicability in vivo.…”

Comparative study of Tat vaccine regimens in Mauritian cynomolgus and Indian rhesus macaques: Influence of Mauritian MHC haplotypes on susceptibility/resistance to SHIV89.6P infection

“…PBMCs secreting gamma interferon (IFN-γ) in response to overnight stimulation with a single pool of Tat 15-mers (1 μg/ml each) were enumerated using ELISPOT kits (U-Cytech, Utrecht, The Netherlands) as described [50]. Assays were performed in triplicate; background spots in wells containing only medium (RPMI 1640 containing 5% fetal calf serum, 1 mM L-glutamine, 100 U/ml penicillin, and 100 μg/ml streptomycin) were subtracted.…”

“…Freshly isolated PBMC (10 5 cells/well) were cultured for five days in triplicate in 200 μl of RPMI 1640 medium containing 10% fetal calf serum (FCS), 1mM L-glutamine and 100 U/ml penicillin, 100μg/ml streptomycin (R-10) with 1μg of oxidized Tat /well at 37°C. On the fifth day, cells were pulsed overnight with 3 H-thymidine (1μCi/well), harvested and counted as described [50]. Stimulation indices (SI) were calculated by dividing mean counts per minute (cpm) with Tat by mean cpm with R-10 plus degassed buffer.…”