The binding affinity of double‐stranded RNA motifs to HIV‐1 Tat protein affects transactivation and the neutralizing capacity of anti‐Tat antibodies elicited after intranasal immunization

Abstract

In this study we examined the hypothesis that the binding affinity of two doublestranded (ds) RNA motifs to HIV-1 Tat protein might affect transactivation and the type of anti-Tat immune responses. Using surface plasmon resonance technology we demonstrated the capacity of the poly(A):poly(U) (pA:pU) motif to bind with high affinity to a totally synthetic Tat protein and to inhibit more efficiently the Tat/ transactivation response element (TAR) RNA interaction as compared to the poly(I):poly(C) (pI:pC) motif. Furthermore, the pA:pU motif was tenfold more effective in inhibiting Tat-driven transactivation than the pI:pC motif. Following intranasal immunization of mice, both dsRNA motifs enhanced the antibody (serum and mucosal) and cellular responses to Tat. However, only the serum samples of mice immunized with Tat + pI:pC inhibited Tat-driven transactivation. The profile of serum antibody subclasses together with the secreted cytokines by Tat-stimulated splenocyte cultures indicated that both dsRNA motifs favored the induction of a balanced Th1 and Th2 immune response. The demonstration in this study that two dsRNA motifs had a marked effect on Tat/TAR RNA interaction and on the neutralizing capacity of anti-Tat specific antibody responses highlights their potential for biological applications and the importance of selecting the appropriate motif as an adjuvant for vaccine design.

Nasal Immunization with Anthrax Protective Antigen Protein Adjuvanted with Polyriboinosinic–Polyribocytidylic Acid Induced Strong Mucosal and Systemic Immunities

“…3 indicate that, similar to previous reports (31,32), the Ab response induced by pI:C as an adjuvant was more IgG1/IgG2a-balanced, because both anti-PA IgG1 and IgG2a were induced, in contrast to the more IgG1-biased immune responses induced when Alum or CT were used as adjuvants. For example, the anti-PA IgG1/ IgG2a ratio was changed from 0.8 in naïve mice to 6.6Y25.6 in mice immunized by s.c injection of rPA admixed with Alum, and to 5.4Y7.6 in mice nasally dosed with rPA admixed with CT (Fig.…”

“…For example, Ichinohe et al (31) reported that nasal immunization of mice with an inactivated hemaglutinin (HA) admixed with pI:C protected the mice against an influenza viral infection (31). Similarly, Partidos et al (32) reported the induction of specific serum and mucosal Abs, as well as cellular responses, to the HIV TAT protein when the molecular complex of TAT and pI:C was nasally administered into mice (32).…”

HIV-1 Tat-Based Vaccines: An Overview and Perspectives in the Field of HIV/AIDS Vaccine Development

“…In addition, evidence exists that natural IgM antibodies reacting with Tat may provide an early initial defense against the pathological effects of Tat after HIV infection and influence the course of AIDS progression [131,132]. Similarly, immunization with Tat elicits antibody responses in rodents, monkeys, and humans able to block the activity of extracellular Tat on cellular entry, gene expression, and replication [4,84,[133][134][135][136][137][138][139][140][141][142]. Moreover, strong anti-Tat antibody responses correlated with an efficient reduction in plasma viremia and long-term protection in Tat protein-vaccinated monkeys challenged intrarectally with an heterologous SHIV virus [143].…”

Nasal immunization with the mixture of PA63, LF, and a PGA conjugate induced strong antibody responses against all three antigens

“…Poly(I:C) was known to have adjuvant activity (Park & Baron, 1968; Herman & Baron, 1971). In a couple of recent studies, poly(I:C) was dosed intranasally to induce anti‐HIV Tat and antihemaglutinin immune responses (Ichinohe et al , 2005; Partidos et al , 2005). Poly(I:C) is an agonist of Toll‐like receptor 3 (TLR3) and was shown to have multiple mechanisms to promote the induction of immune responses (Alexopoulou et al , 2001; Le Bon et al , 2003; Schulz et al , 2005).…”

“…A synthetic double‐stranded RNA (dsRNA), poly(I:C), was used as a vaccine adjuvant. Data from recent studies have shown that the poly(I:C) was a safe and potent nasal vaccine adjuvant (Ichinohe et al , 2005; Partidos et al , 2005; Asahi‐Ozaki et al , 2006; Sloat & Cui, 2006a, b). This study showed that strong and functional immune responses against all three antigens were induced after only 2 or 3 intranasal doses with this prototypic triantigen vaccine candidate, and that the anti‐PA Abs induced were as strong as that induced by s.c. injection of rPA83 adsorbed onto aluminum hydroxide gel (Alum).…”