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Promising Results of Novel J&J HIV Combination Vaccine
 
 
  "In summary, our data demonstrate the proof-of-concept that vaccination can protect against acquisition of stringent, heterologous, neutralization-resistant SIVMAC251 challenges in rhesus monkeys. These findings, together with the observations of a critical requirement for Env and the distinct immunological correlates of protection against acquisition of infection and virological control, pave novel paths forward for HIV-1 vaccine development......""Our studies also demonstrate that inclusion of Env in the vaccine was required for the acquisition effect....our immunological correlates analyses (Figs 2, 4 and Supplementary Tables 1-3) suggest that Env-specific antibodies are critical for blocking acquisition of infection, whereas multiple cellular and humoral immune responses correlate with virological control, although the actual mechanisms of protection remain to be determined. In addition, the RV144 immunological correlates analyses raised the hypothesis that vaccine-elicited V1/V2-specific antibodies may reduce HIV-1 acquisition risk in humans22. Our data (Figs 2f, 4c) are consistent with this hypothesis, although it remains unclear whether V2-specific antibodies actually protect or simply represent a marker for other Env-specific antibodies or other protective factors. Our findings suggest that a substantial degree of protection can be achieved against stringent virus challenges even in the absence of high titres of tier 2 NAbs, perhaps reflecting the importance of antibody effector functions that may not be fully measured by traditional virus neutralization assays. Of note, the partial protection in the present study was observed with vectored Env and without a purified Env protein subunit boost. The degree to which an Env protein boost may further improve the protective efficacy afforded by these vaccine regimens remains to be determined."

LEIDEN, Netherlands, January 5, 2012/PRNewswire/ --

Preclinical Study Provides Strong Rationale for HIV Vaccine Clinical Trials

Results from a recent study present new insights into the immune responses underlying protection against HIV infection and provide a path forward for HIV vaccine development. Published in this week's online version of the journal Nature, the study shows that novel vaccine combinations can provide partial protection against infection by Simian Immunodeficiency Virus (SIV), a virus similar to HIV, in rhesus monkeys. In addition, the study showed in the animals that became infected, the optimal vaccine combinations also substantially reduced the amount of virus in the blood. The study was a collaboration between Crucell Holland B.V., the Beth Israel Deaconess Medical Center and Ragon Institute of MGH, MIT and Harvard, and the U.S. Military HIV Research Program at the Walter Reed Army Institute of Research.

Preclinical studies of HIV-1 vaccine candidates have typically shown post-infection virologic control, but protection against becoming infected has previously only been reported using less rigorous viral challenges. This proof-of-concept study, which tested MVA, Ad26, and Ad35 vector-based vaccines, is the first to show partial vaccine protection in the stringent animal model involving heterologous, neutralization-resistant SIVmac251 viral challenges in rhesus monkeys. The new Ad26/MVA and Ad35/Ad26 vector-based vaccine regimens resulted in more than 80% reduction in the per-exposure probability of acquisition of infection against repetitive challenges of SIV.

"This study allowed us to evaluate the protective efficacy of several prime-boost vaccine combinations, and these data will help guide the advancement of the most promising candidates into clinical trials," said Jaap Goudsmit, M.D., Ph.D., Chief Scientific Officer, Crucell Holland B.V.

Further analysis also provided insights into the immune responses that may correlate with protection, called "immune correlates." The results show that antibodies to Env (the envelope protein that makes up the outer coat of the virus) correlated with preventing infection, whereas both T cell and antibody responses correlated with control of post-infection viral replication. These distinct correlates likely reflect fundamentally different mechanisms needed to block establishment of infection compared with controlling viral replication after infection. Goudsmit also noted that "we have clearly shown that including Env in the vaccine is beneficial."

These new preclinical findings provide support for advancing the Ad26/MVA prime-boost vaccine candidate into clinical development.

The research was supported by the National Institute of Allergy and Infectious Diseases (NIAID); the Ragon Institute of MGH, MIT, and Harvard; and MHRP.

Crucell Holland B.V. is one of the Janssen Pharmaceutical Companies of Johnson & Johnson.

Source: Crucell N.V

CONTACTS: Karen Manson, Media, +32-479-89-47-99 (mobile)

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Vaccine protection against acquisition of neutralization-resistant SIV challenges in rhesus monkeys

Nature 04 January 2012

Dan H. Barouch1,2, Jinyan Liu1, Hualin Li1, Lori F. Maxfield1, Peter Abbink1, Diana M. Lynch1, M. Justin Iampietro1, Adam SanMiguel1, Michael S. Seaman1, Guido Ferrari3, Donald N. Forthal4, Ilnour Ourmanov5, Vanessa M. Hirsch5, Angela Carville6, Keith G. Mansfield6, Donald Stablein7, Maria G. Pau8, Hanneke Schuitemaker8, Jerald C. Sadoff8, Erik M. Billings9, Mangala Rao9, Merlin L. Robb9, Jerome H. Kim9, Mary A. Marovich9, Jaap Goudsmit8* & Nelson L. Michael9*

1Division of Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. 2Ragon Institute of MGH, MIT, and Harvard, Boston, Massachusetts 02114, USA. 3Duke University Medical Center, Durham, North Carolina 27710, USA. 4University of California Irvine School of Medicine, Irvine, Californian 92697, USA. 5National Institute of Allergy and

Infectious Diseases, Bethesda, Massachusetts 20892, USA. 6New England Primate Research Center, Southborough, Massachusetts 01772, USA. 7EMMES Corporation, Rockville, Maryland 20850, USA. 8Crucell Holland BV, 2301 CA, Leiden, The Netherlands. 9US Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, USA.

Preclinical studies of human immunodeficiency virus type 1 (HIV-1) vaccine candidates have typically shown post-infection virological control, but protection against acquisition of infection has previously only been reported against neutralization-sensitive virus challenges1, 2, 3. Here we demonstrate vaccine protection against acquisition of fully heterologous, neutralization-resistant simian immunodeficiency virus (SIV) challenges in rhesus monkeys. Adenovirus/poxvirus and adenovirus/adenovirus-vector-based vaccines expressing SIVSME543 Gag, Pol and Env antigens resulted in an 80% or greater reduction in the per-exposure probability of infection4, 5 against repetitive, intrarectal SIVMAC251 challenges in rhesus monkeys. Protection against acquisition of infection showed distinct immunological correlates compared with post-infection virological control and required the inclusion of Env in the vaccine regimen. These data demonstrate the proof-of-concept that optimized HIV-1 vaccine candidates can block acquisition of stringent, heterologous, neutralization-resistant virus challenges in rhesus monkeys.

Despite the recent demonstration of partial HIV-1 vaccine efficacy in humans6, the immune responses required to protect against acquisition of infection have remained unclear. Preclinical studies of HIV-1 vaccine candidates have begun to elucidate immunological correlates of protection against neutralization-sensitive viruses1, 2, 3, but no study has to date reported vaccine protection against acquisition of heterologous, neutralization-resistant virus challenges1, 7, 8. Mucosal SIVMAC251 infection of rhesus monkeys represents a stringent preclinical model of a highly pathogenic, neutralization-resistant virus swarm1, 9, 10, and repetitive mucosal challenges more closely mimic sexual HIV-1 transmission in humans than do single high-dose challenges10. We therefore performed two studies to evaluate the protective efficacy of optimized adenovirus/poxvirus and adenovirus/adenovirus vector-based vaccines against repetitive, heterologous, intrarectal SIVMAC251 challenges in rhesus monkeys.

In the first study, 40 Indian-origin rhesus monkeys (Macaca mulatta) that did not express the class I alleles Mamu-A*01, Mamu-B*08, and Mamu-B*17 associated with spontaneous virological control11, 12, 13 were immunized by the intramuscular route with the following vaccine regimens expressing SIVSME543 Gag-Pol and Env immunogens (N = 8 per group): (1) DNA prime, modified vaccinia Ankara (MVA) boost; (2) MVA prime, MVA boost; (3) adenovirus serotype 26 (Ad26) prime, MVA boost; (4) MVA prime, Ad26 boost; and (5) sham controls. Groups were balanced for susceptible and resistant TRIM5α alleles1, 14. Monkeys were primed once at week 0 with 2 x 1010 viral particles of Ad26 vectors or 108 plaque-forming units (p.f.u.) of MVA vectors, or three times at weeks 0, 4, and 8 with 5 mg of DNA vaccines. Animals were then boosted once at week 24 with 2 x 1010 viral particles of Ad26 vectors or 108 p.f.u. of MVA vectors.

The vaccine regimens elicited distinct profiles of cellular and humoral immune responses, as measured by IFN-γ ELISPOT assays (Fig. 1a and Supplementary Fig. 1), multiparameter intracellular cytokine staining (ICS) assays8, 15, 16, 17 (Fig. 1b and Supplementary Fig. 2), cellular immune breadth (Supplementary Fig. 3), SIVMAC251 Env-specific binding antibody ELISAs (Fig. 1c), tier 1 neutralizing antibody (NAb) assays against tissue culture laboratory adapted (TCLA) tier 1 SIVSME660 (CP3C-P-A8) and SIVMAC251 (TCLA) pseudoviruses (Fig. 1d), and antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cell-mediated virus inhibition (ADCVI) assays (Supplementary Fig. 4). Tier 2 NAb responses against neutralization-resistant SIVSME660 (CR54-PK-2A5) and SIVMAC251 (SIVMAC251.30) pseudoviruses, however, were below the 50% neutralization cutoff for positivity, although positive trends were observed in all vaccinated groups (Supplementary Fig. 4).

To evaluate the protective efficacy of these vaccine regimens, all monkeys were challenged repetitively beginning at week 52 (six months following the boost immunization) with six intrarectal inoculations of the heterologous virus SIVMAC251 using a 1:1,000 dilution (930 half-maximal tissue-culture infectious dose (TCID50)) of our challenge stock9. After the first challenge, 75% of sham control monkeys became infected, compared with only 12-25% of the animals that received the heterologous vector regimens DNA/MVA, Ad26/MVA, and MVA/Ad26 (Fig. 1e). The percentage of uninfected animals declined proportionately with each challenge, and the majority of vaccinees and all controls were infected by the end of the challenge protocol. Monkeys that received the Ad26/MVA and MVA/Ad26 vaccines required three challenges to infect 50% of animals in each group, whereas only one challenge was required to infect 50% of animals in the control group (P = 0.004 and P = 0.006, respectively, Wald tests, proportional hazard model). The heterologous vector regimens also showed decreased hazard ratios of 0.17 (95% confidence interval (CI) 0.05-0.57) to 0.20 (CI 0.06-0.63) compared with the controls, corresponding to an 80-83% reduction in the per-exposure probability of infection (Fig. 1f; vaccine efficacy VE = 1 - hazard ratio), as previously described4, 5. These data demonstrate vaccine protection against acquisition of infection following repetitive, heterologous, intrarectal SIVMAC251 challenges.

Control monkeys showed peak viral loads on day 14 following infection and then relatively stable mean set point viral loads of 5.85 log SIV RNA copies per millilitre (Supplementary Fig. 5). The Ad26/MVA and the MVA/Ad26 vaccines resulted, respectively, in at least 2.32 and 1.08 log reductions of mean set point viral loads compared with sham controls for over 250 days (P = 0.0037 for each vaccine versus sham, Wilcoxon rank-sum tests) (Fig. 1g and Supplementary Fig. 5). Moreover, half the animals in the Ad26/MVA group either demonstrated rapid and durable virological control to undetectable levels (Fig. 1g; N = 3) or remained uninfected (Fig. 1e; N = 1). The Ad26/MVA and MVA/Ad26 vaccines also afforded a survival advantage as compared with the controls (P = 0.025, log-rank test) (Supplementary Fig. 6).

We next evaluated the immunological correlates of protection against acquisition of infection, defined as the number of challenges required to establish infection, and virological control, defined as set point viral loads. Our pre-specified primary immunological correlates analysis (Supplementary Table 1) demonstrated that protection against acquisition of infection was best correlated with Env-specific binding ELISA antibody responses (Fig. 2a; P < 0.0001, Spearman rank-correlation test) and tier 1 NAb titres (Fig. 2b; P = 0.0034) immediately before challenge. Protection against acquisition of infection also correlated with V2-specific antibodies that presumably represented a subset of total Env-specific binding antibodies (Fig. 2e, f; P < 0.0001). Virological control was correlated with Gag ELISPOT breadth (Fig. 2c; P = 0.0002) and magnitude (Fig. 2d; P = 0.0058) immediately before challenge, consistent with our previous observations18.

In our exploratory immunological correlates analysis, we evaluated 35 humoral and cellular immune parameters at both peak and memory time points before challenge as possible immunological correlates of acquisition and virological control following challenge. No additional immune parameters were significantly correlated with protection against acquisition of infection in this analysis after multiple comparison adjustments (Supplementary Table 2). Gag-, Pol- and Env-specific effector memory CD8+ T-lymphocyte responses exhibited trends towards protection against acquisition, but did not achieve statistical significance according to our pre-specified criteria. In contrast, multiple humoral and cellular immune responses were significantly correlated with virological control (Supplementary Table 3), including Env ELISA, NAb and ADCC responses as well as Gag ELISPOT magnitude and breadth, Pol ELISPOT magnitude and Env CD4+ effector memory responses. These data support a model in which protection against acquisition of infection is correlated with vaccine-elicited Env antibody responses, whereas virological control is correlated with both T-lymphocyte and antibody responses. These distinct immunological correlates probably reflect fundamentally different biologic requirements for blocking establishment of infection at the mucosal site of inoculation compared with controlling viral replication after infection has become disseminated19. However, the actual mechanisms of protection remain to be determined.

We next evaluated directly the hypothesis that Env was critical for blocking acquisition of infection in this system. In the second study, 40 rhesus monkeys that did not express the class I alleles Mamu-A*01, Mamu-B*08 and Mamu-B*17 were immunized by the intramuscular route with Ad35 prime20, Ad26 boost21 vaccine regimens expressing (1) SIVSME543 Gag-Pol (N = 16), (2) SIVSME543 Gag-Pol and Env (N = 16) and (3) sham controls (N = 8). Groups were balanced for susceptible and resistant TRIM5α alleles1, 14. Monkeys were primed once at week 0 with 2 x 1010 viral particles of Ad35 vectors and boosted once at week 24 with 2 x 1010 viral particles of Ad26 vectors. Cellular immune responses were assessed by IFN-γ ELISPOT assays (Fig. 3a and Supplementary Fig. 7) and multiparameter ICS assays in both the periphery (Fig. 3b and Supplementary Fig. 8) and in colorectal mucosa (Supplementary Fig. 9). Env-specific humoral immune responses were assessed by ELISAs in both the periphery (Fig. 3c) and in colorectal mucosa (Supplementary Fig. 10), tier 1 NAb assays (Fig. 3d) and ADCC assays (Supplementary Fig. 11). Only marginal tier 2 NAb responses were observed (Supplementary Fig. 11).

We assessed protective efficacy of these vaccine regimens against repetitive, heterologous, intrarectal SIVMAC251 challenges as described in the first study. After the first challenge, 50% of sham control monkeys became infected, compared with only 12% of the animals that received the Gag-Pol-Env vaccine (Fig. 3e). The monkeys that received the Gag-Pol-Env vaccine required four challenges to infect 50% of animals in each group, whereas only one challenge was required to infect 50% of animals in the control group (Fig. 3f; P = 0.002, Wald test, proportional hazard model). Moreover, the Gag-Pol-Env vaccine resulted in a decreased hazard ratio of 0.20 (CI 0.07-0.55), corresponding to an 80% reduction in the per-exposure probability of infection. In contrast, the Gag-Pol vaccine afforded only a marginal protective effect, demonstrating the critical role of Env in blocking acquisition of infection in this model. The Gag-Pol and Gag-Pol-Env vaccines resulted in, respectively, at least 1.59 log and 2.18 log reductions of set point viral loads compared with controls (Fig. 3g and Supplementary Fig. 12; P = 0.0006 and 0.0002, respectively, Wilcoxon rank-sum tests). Immunological correlates of protection against acquisition of infection were consistent with the first study, and both peripheral (Fig. 4a-c) and rectal (Fig. 4d) Env-specific IgG correlated with reduced acquisition risk.

Taken together, these data demonstrate that optimized adenovirus/poxvirus and adenovirus/adenovirus vector-based vaccines afforded significant protection against acquisition of infection following highly pathogenic, heterologous, neutralization-resistant SIVMAC251 challenges in rhesus monkeys (Figs 1e, 3e and Supplementary Fig. 13). Although several studies have previously shown partial protection against acquisition of neutralization-sensitive virus challenges1, 2, 3, no HIV-1 vaccine candidate has to date blocked acquisition of heterologous, difficult-to-neutralize virus challenges, including Ad5 (ref. 7), DNA/Ad5 (ref. 1) and cytomegalovirus8 vaccines. In particular, a recent study demonstrated that a DNA/Ad5 vaccine afforded partial protection against acquisition of SIVSME660, which is a neutralization-sensitive tier 1A virus in TZM-bl neutralization assays, but the same vaccine afforded no efficacy against neutralization-resistant SIVMAC251 (ref. 1), highlighting important differences in the stringencies between these two SIV challenge models as well as potentially important phenotypic differences between adenovirus serotypes17. However, we note that the acquisition effect in the present study was relative rather than absolute, and that the majority of vaccinees became infected by the end of the challenge protocol.

Our studies also demonstrate that inclusion of Env in the vaccine was required for the acquisition effect (Fig. 3e), despite an 18% difference in the Env amino acid sequences between the vaccine strain and challenge virus. Moreover, our immunological correlates analyses (Figs 2, 4 and Supplementary Tables 1-3) suggest that Env-specific antibodies are critical for blocking acquisition of infection, whereas multiple cellular and humoral immune responses correlate with virological control, although the actual mechanisms of protection remain to be determined. In addition, the RV144 immunological correlates analyses raised the hypothesis that vaccine-elicited V1/V2-specific antibodies may reduce HIV-1 acquisition risk in humans22. Our data (Figs 2f, 4c) are consistent with this hypothesis, although it remains unclear whether V2-specific antibodies actually protect or simply represent a marker for other Env-specific antibodies or other protective factors.

Considerable efforts are currently underway to identify and to reverse engineer potent, broadly reactive monoclonal antibodies23, 24. Although the induction of such NAb responses by a vaccine would presumably be highly desirable, no Env immunogens have to date been developed that can elicit these responses. Our findings suggest that a substantial degree of protection can be achieved against stringent virus challenges even in the absence of high titres of tier 2 NAbs, perhaps reflecting the importance of antibody effector functions that may not be fully measured by traditional virus neutralization assays. Of note, the partial protection in the present study was observed with vectored Env and without a purified Env protein subunit boost. The degree to which an Env protein boost may further improve the protective efficacy afforded by these vaccine regimens remains to be determined.

In summary, our data demonstrate the proof-of-concept that vaccination can protect against acquisition of stringent, heterologous, neutralization-resistant SIVMAC251 challenges in rhesus monkeys. These findings, together with the observations of a critical requirement for Env and the distinct immunological correlates of protection against acquisition of infection and virological control, pave novel paths forward for HIV-1 vaccine development.

 
 
 
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