RTE and CTE mRNA export elements synergistically increase expression of unstable, Rev-dependent HIV and SIV mRNAs

Studies of retroviral mRNA export identified two distinct RNA export elements utilizing conserved eukaryotic mRNA export mechanism(s), namely the Constitutive Transport Element (CTE) and the RNA Transport Element (RTE). Although RTE and CTE are potent in nucleocytoplasmic mRNA transport and expression, neither element is as powerful as the Rev-RRE posttranscriptional control. Here, we found that whereas CTE and the up-regulatory mutant RTEm26 alone increase expression from a subgenomic gag and env clones, the combination of these elements led to a several hundred-fold, synergistic increase. The use of the RTEm26-CTE combination is a simple way to increase expression of poorly expressed retroviral genes to levels otherwise only achieved via more cumbersome RNA optimization. The potent RTEm26-CTE element could be useful in lentiviral gene therapy vectors, DNA-based vaccine vectors, and gene transfer studies of other poorly expressed genes

Live Attenuated Rev-Independent Nef¯SIV Enhances Acquisition of Heterologous SIVsmE660 in Acutely Vaccinated Rhesus Macaques

Background: Rhesus macaques (RMs) inoculated with live-attenuated Rev-Independent Nef¯ simian immunodeficiency virus (Rev-Ind Nef¯SIV) as adults or neonates controlled viremia to undetectable levels and showed no signs of immunodeficiency over 6-8 years of follow-up. We tested the capacity of this live-attenuated virus to protect RMs against pathogenic, heterologous SIVsmE660 challenges. Methodology/Principal Findings Three groups of four RM were inoculated with Rev-Ind Nef¯SIV and compared. Group 1 was inoculated 8 years prior and again 15 months before low dose intrarectal challenges with SIVsmE660. Group 2 animals were inoculated with Rev-Ind Nef¯SIV at 15 months and Group 3 at 2 weeks prior to the SIVsmE660 challenges, respectively. Group 4 served as unvaccinated controls. All RMs underwent repeated weekly low-dose intrarectal challenges with SIVsmE660. Surprisingly, all RMs with acute live-attenuated virus infection (Group 3) became superinfected with the challenge virus, in contrast to the two other vaccine groups (Groups 1 and 2) (P=0.006 for each) and controls (Group 4) (P=0.022). Gene expression analysis showed significant upregulation of innate immune response-related chemokines and their receptors, most notably CCR5 in Group 3 animals during acute infection with Rev-Ind Nef¯SIV. Conclusions/Significance: We conclude that although Rev-Ind Nef¯SIV remained apathogenic, acute replication of the vaccine strain was not protective but associated with increased acquisition of heterologous mucosal SIVsmE660 challenges

Evaluation of a multivalent vaccine against lymphatic filariasis in rhesus macaque model.

Lymphatic filariasis affects 120 million people worldwide and another 1.2 billion people are at risk of acquiring the infection. Chemotherapy with mass drug administration is substantially reducing the incidence of the infection. Nevertheless, an effective vaccine is needed to prevent the infection and eradicate the disease. Previously we reported that a multivalent fusion protein vaccine (rBmHAT) composed of small heat shock proteins 12.6 (HSP12.6), abundant larval transcript-2 (ALT-2) and large extracellular domain of tetraspanin (TSP LEL) could confer >95% protection against the challenge infection with Brugia malayi infective larvae (L3) in mouse and gerbil models. In this study we evaluated the immunogenicity and efficacy of rBmHAT fusion protein vaccine in a rhesus macaque model. Our results show that rBmHAT is highly immunogenic in rhesus macaques. All the vaccinated monkeys developed significant titers of antigen-specific IgG antibodies against each of the component antigens (16,000 for rBmHSP12.6), (24,000 for rBmALT-2) and (16,000 for rBmTSP-LEL). An in vitro antibody dependent cellular cytotoxicity (ADCC) assay performed using the sera samples from vaccinated monkeys showed that the anti-rBmHAT antibodies are functional with 35% killing of B. malayi L3s. Vaccinated monkeys also had antigen responding cells in the peripheral blood. Vaccine-induced protection was determined after challenging the monkeys with 500 B. malayi L3. Following challenge infection, 3 out of 5 vaccinated macaques failed to develop the infection. These three protected macaques had high titers of IgG1 antibodies and their PBMC secreted significantly high levels of IFN-γ in response to the vaccine antigens. The two vaccinated macaques that picked the infection had slightly low titers of antibodies and their PBMC secreted high levels of IL-10. Based on these findings we conclude that the rBmHAT vaccine is highly immunogenic and safe and can confer significant protection against challenge infections in rhesus macaques

Percent of eosinophils in the peripheral blood of control and vaccinated macaques.

<p>Percent of eosinophils were evaluated in the peripheral blood of macaque pre- and post- challenge. Following challenge there was an increase in the frequency of eosinophils in animals that were microfilaremic as determined by Knott’s technique. Each line represents the eosinophil count of individual macaque on weeks −13, −9, −5, −1 before challenge, on day of challenge (week 0) and at weeks 1, 5, 10, and 14 post challenges. The levels of eosinophils in Mf positive animals are represented by a solid line. Levels of eosinophils in Mf negative animals are represented as a dotted line. # Macaques immunized with r<i>Bm</i>HAT. Significant at **P<0.001 high number of eosinophils.</p

Correlates of protection in macaques vaccinated with r<i>Bm</i>HAT.

<p>The three vaccinated macaques that did not show any evidence of infection had high titer of anti- r<i>Bm</i>HAT IgG antibodies and their PBMC secreted significantly high levels of IFN-γ but low levels of IL-10 as determined by an ELISPOT assay. Ratio of IFN-γ: IL-10 secreting cells was calculated for each macaque. These analyses also confirmed that there is a clear difference between the infected macaques and the three vaccinated macaques that did not show any infection. These findings coupled with the ADCC data clearly suggest that the three vaccinated macaques that did not show any signs of infection were protected.</p><p>#PBMC collected before challenge and stimulated with r<i>Bm</i>HAT.</p><p>Correlates of protection in macaques vaccinated with r<i>Bm</i>HAT.</p

r<i>Bm</i>HAT specific antibodies isotypes in the sera of macaques.

<p>Levels of IgG1, IgG2, IgG3, IgA and IgE antibodies against A) r<i>Bm</i>HSP, B) r<i>Bm</i>ALT-2, C) r<i>Bm</i>TSP and D) r<i>Bm</i>HAT were determined in the sera (collected one month after the final dose of vaccine) of each rhesus macaque using an indirect ELISA. IgG1 antibodies were predominantly present in the immunized animals against all the four antigens tested. Each bar represents mean ±S.D of 5 animals. Significant **P<0.001 titer of antibodies observed compared to other animals.</p

Detection of Mf in the macaques challenged with <i>B. malayi</i> L3.

<p>The appearance of Mf in the peripheral blood of macaques during weeks 11–20 post challenge was detected by Knott and PCR techniques. 3 macaques in control group and 2 macaques in the immunized group were found to be microfilaremic.</p><p>Detection of Mf in the macaques challenged with <i>B. malayi</i> L3.</p

PBMC were isolated 10 weeks post challenge from each macaque and cultured at 2×10⁵ cells per well in triplicate wells of a 96 wells plate.

<p>PBMC were stimulated <i>in vitro</i> with 1 µg/ml of r<i>Bm</i>HAT for 72 hrs at 37°C and analyzed for proliferation using cell counting kit (CCK-8). Con A was used as positive control. Stimulation index (S.I.) was calculated from the unstimulated control wells.</p><p><i>Significant proliferation of PBMC **(P<0.001) compare to PBMC from other macaques.</i></p><p>PBMC were isolated 10 weeks post challenge from each macaque and cultured at 2×10⁵ cells per well in triplicate wells of a 96 wells plate.</p

All 10 monkeys challenged with <i>B. malayi</i> L3 were screened for the appearance of Mf in the peripheral blood circulation by Knott technique and PCR analysis.

<p>A) Results from Knott technique showed the presence of mf in the blood that was stained with methylene blue. B) Mf specific <i>Hha I</i> gene was amplified and analyzed in 1% agarose gel.</p