Tracey L. Müller

Broad, high-magnitude and multifunctional CD4 + and CD8 + T-cell responses elicited by a DNA and modified vaccinia Ankara vaccine containing human immunodeficiency virus type 1 subtype C genes in baboons

Candidate human immunodeficiency virus (HIV) vaccine regimens based on DNA boosted with recombinant modified vaccinia Ankara (MVA) have been in development for some time, and there is evidence for improved immunogenicity of newly developed constructs. This study describes immune responses to candidate DNA and MVA vaccines expressing multiple genes (gag, RT, tat, nef and env) from HIV-1 subtype C in chacma baboons (Papio ursinus). The vaccine regimen induced (i) strong T-cell responses, with a median of 4103 spot forming units per 10(6) peripheral blood mononuclear cells by gamma interferon (IFN-gamma) ELISPOT, (ii) broad T-cell responses targeting all five vaccine-expressed genes, with a median of 12 peptides targeted per animal and without any single protein dominating the response, (iii) balanced CD4(+) and CD8(+) responses, which produced both IFN-gamma and interleukin (IL)-2, including IL-2-only responses not detected by the ELISPOT assay, (iv) vaccine memory, which persisted 1 year after immunization and could be boosted further, despite strong anti-vector responses, and (v) mucosal T-cell responses in iliac and mesenteric lymph nodes in two animals tested. The majority of peptide responses mapped contained epitopes previously identified in human HIV infection, and two high-avidity HIV epitope responses were confirmed, indicating the utility of the baboon model for immunogenicity testing. Together, our data show that a combination of DNA and MVA immunization induced robust, durable, multifunctional CD4(+) and CD8(+) responses in baboons targeting multiple HIV epitopes that may home to mucosal sites. These candidate vaccines, which are immunogenic in this pre-clinical model, represent an alternative to adenoviral-based vaccines and have been approved for clinical trials.

The novel capripoxvirus vector lumpy skin disease virus efficiently boosts modified vaccinia Ankara human immunodeficiency virus responses in rhesus macaques.

Poxvirus vectors represent promising human immunodeficiency virus (HIV) vaccine candidates and were a component of the only successful HIV vaccine efficacy trial to date. We tested the immunogenicity of a novel recombinant capripoxvirus vector, lumpy skin disease virus (LSDV), in combination with modified vaccinia Ankara (MVA), both expressing genes from HIV-1. Here, we demonstrated that the combination regimen was immunogenic in rhesus macaques, inducing high-magnitude, broad and balanced CD4(+) and CD8(+) T-cell responses, and transient activation of the immune response. These studies support further development of LSDV as a vaccine vector.

Characterization of Mycobacterium tuberculosis–Specific Cells Using MHC Class II Tetramers Reveals Phenotypic Differences Related to HIV Infection and Tuberculosis Disease

A major challenge for the development of an effective vaccine against tuberculosis (TB) is that the attributes of protective CD4+ T cell responses are still elusive for human TB. Infection with HIV type 1 is a major risk factor for TB, and a better understanding of HIV-induced alterations of Mycobacterium tuberculosis–specific CD4+ T cells that leads to failed host resistance may provide insight into protective T cell immunity to TB. A total of 86 participants from a TB-endemic setting, either HIV-infected or uninfected and with latent or active TB (aTB), were screened using M. tuberculosis–specific MHC class II tetramers. We examined the phenotype as well as function of ex vivo M. tuberculosis–specific tetramer+CD4+ T cells using flow cytometry. The numbers of M. tuberculosis–specific tetramer+CD4+ T cells were relatively well maintained in HIV-infected persons with aTB, despite severe immunodeficiency. However, although HIV-uninfected persons with latent TB infection exhibited ex vivo M. tuberculosis–specific CD4+ T cells predominantly of a CXCR3+CCR6+CCR4− (Th1*) phenotype, aTB or HIV infection was associated with a contraction of this subset. Nevertheless, in individuals with aTB and/or HIV infection, circulating ex vivo M. tuberculosis–specific CD4+ T cells did not display defects in exhaustion or polyfunctionality compared with healthy HIV-uninfected individuals with latent TB infection. Collectively, these data suggest that increased susceptibility to TB disease could be related to a loss of circulating Th1* CD4+ T cells rather than major changes in the number or function of circulating CD4+ T cells.

Selective reduction of IFN-γ single positive mycobacteria-specific CD4+ T cells in HIV-1 infected individuals with latent tuberculosis infection

Summary HIV-1 is recognized to increase the risk for tuberculosis even before CD4+ T cell deficiency is profound. To better understand how HIV-1 alters immunity to latent tuberculosis, we compared the magnitude and functional profile of mycobacteria-specific CD4+ T cells between HIV-uninfected and HIV-infected individuals, using flow cytometry. In HIV-1 infection, IFN-γ single positive mycobacteria-specific CD4+ T cells were decreased, while the frequency of polyfunctional cells (IFN-γ+IL-2+TNF-α+) remained unchanged. Moreover, the proportion of IFN-γ single positive cells correlated inversely with viral replication. Our results suggest that HIV-1 affects mycobacteria-specific cells differentially, depending on their functional capacity.

Effect of antiretroviral therapy on the memory and activation profiles of B cells in HIV-infected African women.

Human immunodeficiency virus infection induces a wide range of effects in B cells, including skewed memory cell differentiation, compromised B cell function, and hypergammaglobulinemia. However, data on the extent to which these B cell abnormalities can be reversed by antiretroviral therapy (ART) are limited. To investigate the effect of ART on B cells, the activation (CD86) and differentiation (IgD, CD27, and CD38) profiles of B cells were measured longitudinally in 19 HIV-infected individuals before (median, 2 mo) and after ART initiation (median, 12 mo) and compared with 19 age-matched HIV-uninfected individuals using flow cytometry. Twelve months of ART restored the typical distribution of B cell subsets, increasing the proportion of naive B cells (CD27−IgD+CD38−) and concomitantly decreasing the immature transitional (CD27−IgD+CD38+), unswitched memory (CD27+IgD+CD38−), switched memory (CD27+IgD−CD38− or CD27−IgD−CD38−), and plasmablast (CD27+IgD−CD38high) subsets. However, B cell activation was only partially normalized post-ART, with the frequency of activated B cells (CD86+CD40+) reduced compared with pre-ART levels (p = 0.0001), but remaining significantly higher compared with HIV-uninfected individuals (p = 0.0001). Interestingly, unlike for T cell activation profiles, the extent of B cell activation prior to ART did not correlate with HIV plasma viral load, but positively associated with plasma sCD14 levels (p = 0.01, r = 0.58). Overall, ART partially normalizes the skewed B cell profiles induced by HIV, with some activation persisting. Understanding the effects of HIV on B cell dysfunction and restoration following ART may provide important insights into the mechanisms of HIV pathogenesis.

DNA-MVA-protein vaccination of rhesus macaques induces HIV-specific immunity in mucosal-associated lymph nodes and functional antibodies

Successful future HIV vaccines are expected to generate an effective cellular and humoral response against the virus in both the peripheral blood and mucosal compartments. We previously reported the development of DNA-C and MVA-C vaccines based on HIV-1 subtype C and demonstrated their immunogenicity when given in a DNA prime-MVA boost combination in a nonhuman primate model. In the current study, rhesus macaques previously vaccinated with a DNA-C and MVA-C vaccine regimen were re-vaccinated 3.5 years later with MVA-C followed by a protein vaccine based on HIV-1 subtype C envelope formulated with MF59 adjuvant (gp140Env/MF59), and finally a concurrent boost with both vaccines. A single MVA-C re-vaccination elicited T cell responses in all animals similar to previous peak responses, with 4/7 demonstrating responses >1000 SFU/106 PBMC. In contrast to an Env/MF59-only vaccine, concurrent boosting with MVA-C and Env/MF59 induced HIV-specific cellular responses in multiple mucosal associated lymph nodes in 6/7 animals, with high magnitude responses in some animals. Both vaccine regimens induced high titer Env-specific antibodies with ADCC activity, as well as neutralization of Tier 1 viruses and modest Tier 2 neutralization. These data demonstrate the feasibility of inducing HIV-specific immunity in the blood and mucosal sites of viral entry by means of DNA and poxvirus-vectored vaccines, in combination with a HIV envelope-based protein vaccine.

Evaluating potential T-cell epitope peptides for detecting HIV-specific T cell responses in a highly diverse HIV-1 epidemic from Cameroon.

HIV genetic diversity is a major obstacle for vaccine development. To define whether potential T-cell epitope (PTE) peptide usage improves the detection of T cell responses in a highly diverse HIV-1 epidemic, we compared the magnitude, breadth and depth of group M PTE peptide responses to consensus M peptides in Gag and Nef proteins. Gag PTE responses were detected at a higher magnitude, more Nef PTE responses were detected at a cohort (but not individual) level and depth was detected in both Gag and Nef responses.

Effect of HIV on the Frequency and Number of Mycobacterium tuberculosis–Specific CD4+ T Cells in Blood and Airways During Latent M. tuberculosis Infection

Human immunodeficiency virus infection leads to lower frequencies of CD4+ T cells specific for Mycobacterium tuberculosis in blood and lungs. However, an influx of T cells to the lungs results in similar absolute numbers of specific CD4+ T cells, compared with uninfected individuals.

A single dose of SAAVI MVA-C reboosts rhesus macaques after more than 3 years post DNA-MVA prime-boost vaccination

Background We have previously reported induction of robust immune responses in rhesus macaques following a prime boost immunization with candidate HIV-1 vaccines, SAAVI DNA-C (DNA) and SAAVI MVA-C (MVA). These vaccines are already in clinical evaluation. In the current study, we investigated whether re-boosting these animals with as ingle MVA inoculation after more than 3y ears was sufficient to restore previous magnitudes of HIVspecific immune responses. Methods Seven rhesus macaques which had been vaccinated with three doses of DNA vaccine (4mg DNA/dose) and two doses of MVA (10 9 pfu MVA/dose) in a past study, >3 years previously, were re-boosted with a single dose of MVA. HIV-1-specific responses were quantified in the peripheral blood using an IFN-gamma ELISPOT assay. Results A peak magnitude of response (1146±240 sfu/10 6 PBMC) was reached 1 week after vaccination with the first dose of MVA. The second MVA inoculation did not increase these responses which declined to undetectable levels by 1 year post vaccination. After re-boosting with MVA after 3.5 years post the second MVA, all animals responded, with a peak response (1824±672 sfu/10 6 PBMC) being reached 1 week after vaccination. Although the mean magnitude of the second peak was not significantly higher than the one seen in the first peak, boosting of responses in 3 of 7 animals with an apparent broadening of the breadth of responses was observed. Conclusion These preliminary data suggest a long-term preservation of vaccine memory following a prime-boost vaccination regimen with SAAVI DNA-C and SAAVI MVA-C vaccines.

Infrequent, low magnitude HIV-specific T cell responses in HIV-uninfected participants in the 1% tenofovir microbicide gel trial (CAPRISA004)

Background Macaque studies of antiretroviral-containing microbicide gels administered rectally or vaginally followed by SIV challenge have documented priming of SIV-specific T cell responses in the blood of protected animals. This concept has been termed “chemo-vaccination”, where aborted viral replication is thought to leave an immune footprint of exposure, which may augment protection provided by microbicides/PrEP. We investigated whether T cell responses were detectable in women participating in CAPRISA004 1% tenofovir microbicide trial, which showed 39% efficacy in reducing HIV acquisition.