Annual and Interim Progress Report Summaries
Principal Investigator: Thomas Lehner
Project: Allogeneic – HIV Mucosal Vaccine Strategy Against HIV, Utilizing Innate and Adaptive Immunity
Submitted March 5, 2010 - Final Report
The aim of the project was to establish if xeno-immunization (using human HLA) and allo-immunization (using macaque Mamu) MHC antigens can prevent or contain infection after challenge with SHIVSF162. In the xeno-immunization experiment the vaccine consisted of HLA-class I and HLA-class II and/or HIVgp140, SIVp27 and HSP70 formulated with dextran into Dextramers, mixed with a co-adjuvant (Titermax) and administered subcutaneously (x4) to 4 groups (one without Titermax) and 1 control group, each consisting of 8 macaques, over a period of 16 weeks. The macaques were challenged IV with SHIVSF162P4, 4 weeks after the last immunization and the viral load was monitored. The results showed significant decrease in viral load or total prevention of infection against the heterologous SHIVSF162P4 in one group of macaques, compared with the unimmunized controls over the post-challenge period of 10 weeks (p<0.001 to p<0.05). Importantly, the protected group of macaques was the one immunized with all vaccine components and the Titermax adjuvant. Protection was not achieved in the other 3 immunized groups, suggesting that excluding HLA, HIVgp140, SIVp27 or the adjuvant failed to elicit significant protection.
These promising results were then evaluated by examining a number of immune functions. High titres of complement-dependent neutralizing antibodies were elicited in 3 of the immunized groups with the adjuvant compared to pre-immunization (p<0.0001). Indeed, significant inverse correlation was found between the cumulative viral load (over the 10 weeks of post-viral challenge) and neutralizing antibodies (p<0.05). High levels of antibodies were induced to the immunizing HLA-class I (A1, A2, A3 and A11) and HLA-class II (DR4) antigens (p<0.01), demonstrating that the recombinant HLA antigens are potent immunogens. As with the neutralizing antibodies, a significant inverse correlation was found between cumulative viral load and the HLA-I antibodies and this appeared to be specific to the protected group of macaques (p<0.001-p<0.05).
Among the innate anti-viral factors APOBEC3G was found to be significantly increased in the immunized groups, again with an inverse correlation with the cumulative viral load (p<0.0001). Thus, both antibodies and innate cellular factors were identified in immunized macaques. To confirm that serum antibodies were responsible for the protection passive transfer of immune serum from the 2 previously protected macaques was administered to 2 new macaques and challenged IV (x6) with low dose SHIV SF162.P4. This elicited complete protection, unlike transfer of control serum, which resulted in infection.
Another group of macaques was used for systemic immunization (SC x3) with the HLA vaccine, followed by repeated low dose (x10) rectal challenge with SHIV SF162.P4 (25MID50). In immunized macaques 4/9 and in controls 2/10 were not infected. The cumulative viral load in all macaques (p<0.05), infected animals only (p=0.02) and sequential viral load (p<0.05-p<0.01) showed significant differences between the immunized and control macaques. These data are consistent with significant protection being achieved with the HLA constructs when challenged rectally by repeated low doses of SHIV (x10).
Rectal mucosal immunization was then attempted with the HLA vaccine (x2) using CPG C as the mucosal adjuvant, followed by SC immunization (x2) with the candidate vaccine. This showed that although 2/9 immunized macaques were not infected, this also applied to 2/10 controls. However, the cumulative viral load was 54.5+11.5 in the controls, compared with 30.7+8.2 in the immunized macaques failed to reach statistical significance (p=0.059), unlike analysis of the infected macaques only (p=0.037) or the sequential viral loads (p<0.05-p<0.02).
Allogeneic immunization with recombinant macaque Mamu class-I and class-II antigens and the other components was then pursued. Systemic immunization was carried out with the Mamu vaccine (x3) followed by rectal challenge with repeated low dose (x10) SHIV SF162.P4 (25 TCID50), grown in Mamu A1-DRB*W1/W2 PBMC expressing the immunizing class I and cross-reacting class II alleles. The vaccine induced complete protection in 3/9 macaques, and significant decrease in cumulative, peak and sequential viral load (p<0.05), compared with the 9 infected controls. Analysis of the immune responses are delayed, as the Chinese permit for shipping the blood samples is pending. Finally, rectal mucosal immunization with the Mamu vaccine but exchanging CPG C adjuvant for Titermax, followed by SC immunization (x2) with the vaccine + Titermax and challenge (x10) rectally by the low dose SHIV SF162.P4 failed to show significant protection. Only 1/9 of the immunized and 2/10 control macaques remained uninfected and the cumulative viral load also showed no significant difference between them.
Conclusions: Systemic immunization with a novel HLA-HIV-SIV-HSP70-dextran linked construct and adjuvant SC (x4) elicited total protection in 2/8 macaques and significant decrease in cumulative and peak (p<0.05), as well as sequential viral load (p<0.01), when challenged IV (x1) or rectally (x10) with repeated low doses of SHIV SF162.P4.
Systemic alloimmunization with the recombinant Mamu-HIV-SIV-HSP70 dextran linked construct and adjuvant, challenged by the rectal mucosal route (x10) with low dose SHIV SF162.P4 also elicited total protection in 3/9 macaques and resulted in significant decrease in the cumulative (p<0.05) and peak viral loads (p<0.05), compared with 9 infected controls. However, rectal mucosal immunization with the HLA Mamu vaccine failed to induce protection.
We have established the proof of concept that systemic alloimmunization with a novel recombinant Mamu construct will elicit significant protection in macaques challenged with repeated low doses of SHIV.SF162.P4.