Nazma Mansoor

Modified vaccinia Ankara-expressing Ag85A, a novel tuberculosis vaccine, is safe in adolescents and children, and induces polyfunctional CD4+ T cells

Modified vaccinia Ankara‐expressing Ag85A (MVA85A) is a new tuberculosis (TB) vaccine aimed at enhancing immunity induced by BCG. We investigated the safety and immunogenicity of MVA85A in healthy adolescents and children from a TB endemic region, who received BCG at birth. Twelve adolescents and 24 children were vaccinated and followed up for 12 or 6 months, respectively. Adverse events were documented and vaccine‐induced immune responses assessed by IFN‐γ ELISpot and intracellular cytokine staining. The vaccine was well tolerated and there were no vaccine‐related serious adverse events. MVA85A induced potent and durable T‐cell responses. Multiple CD4+ T‐cell subsets, based on expression of IFN‐γ, TNF‐α, IL‐2, IL‐17 and GM‐CSF, were induced. Polyfunctional CD4+ T cells co‐expressing IFN‐γ, TNF‐α and IL‐2 dominated the response in both age groups. A novel CD4+ cell subset co‐expressing these three Th1 cytokines and IL‐17 was induced in adolescents, while a novel CD4+ T‐cell subset co‐expressing Th1 cytokines and GM‐CSF was induced in children. Ag‐specific CD8+ T cells were not detected. We conclude that in adolescents and children MVA85A safely induces the type of immunity thought to be important in protection against TB. This includes induction of novel Th1‐cell populations that have not been previously described in humans.

The Effect of Bacille Calmette-Guérin Vaccine Strain and Route of Administration on Induced Immune Responses in Vaccinated Infants

Vaccination with Mycobacterium bovis bacille Calmette-Guerin (BCG) has variable efficacy in preventing tuberculosis. Both BCG strain and route of administration have been implicated in determining efficacy; however, these variables are not considered in current clinical recommendations for vaccine choice. We evaluated antigen-specific immunity after percutaneous or intradermal administration of Japanese BCG or intradermal administration of Danish BCG. Ten weeks after vaccination of neonates, percutaneous Japanese BCG had induced significantly higher frequencies of BCG-specific interferon- gamma -producing CD4(+) and CD8(+) T cells in BCG-stimulated whole blood than did intradermal Danish BCG. Similarly, percutaneous vaccination with Japanese BCG resulted in significantly greater secretion of the T helper 1-type cytokines interferon- gamma, tumor necrosis factor- alpha , and interleukin-2; significantly lower secretion of the T helper 2-type cytokine interleukin-4; and greater CD4(+) and CD8(+) T cell proliferation. Thus, BCG strain and route of neonatal vaccination confer different levels of immune activation, which may affect the efficacy of the vaccine.

Bacillus Calmette Guerin Vaccination of Human Newborns Induces a Specific, Functional CD8+ T Cell Response

Mounting evidence points to CD8+ T cells playing an important role in protective immunity against Mycobacterium tuberculosis. The only available vaccine against tuberculosis, bacillus Calmette Guérin (BCG), has traditionally been viewed not to induce these cells optimally. In this study, we show that vaccination of human newborns with BCG does indeed induce a specific CD8+ T cell response. These cells degranulated or secreted IFN-γ, but not both, when infant blood was incubated with BCG. This stimulation also resulted in proliferation and up-regulation of cytotoxic molecules. Overall, the specific CD8+ T cell response was quantitatively smaller than the BCG-induced CD4+ T cell response. Incubation of whole blood with M. tuberculosis also caused CD8+ T cell IFN-γ expression. We conclude that BCG induces a robust CD8+ T cell response, which may contribute to vaccination-induced protection against tuberculosis.

Induction and Regulation of T-Cell Immunity by the Novel Tuberculosis Vaccine M72/AS01 in South African Adults

RATIONALE Tuberculosis (TB) is a major cause of morbidity and mortality worldwide, thus there is an urgent need for novel TB vaccines. OBJECTIVES We investigated a novel TB vaccine candidate, M72/AS01, in a phase IIa trial of bacille Calmette-Guérin-vaccinated, HIV-uninfected, and Mycobacterium tuberculosis (Mtb)-infected and -uninfected adults in South Africa. METHODS Two doses of M72/AS01 were administered to healthy adults, with and without latent Mtb infection. Participants were monitored for 7 months after the first dose; cytokine production profiles, cell cycling, and regulatory phenotypes of vaccine-induced T cells were measured by flow cytometry. MEASUREMENTS AND MAIN RESULTS The vaccine had a clinically acceptable safety profile, and induced robust, long-lived M72-specific T-cell and antibody responses. M72-specific CD4 T cells produced multiple combinations of Th1 cytokines. Analysis of T-cell Ki67 expression showed that most vaccination-induced T cells did not express Th1 cytokines or IL-17; these cytokine-negative Ki67(+) T cells included subsets of CD4 T cells with regulatory phenotypes. PD-1, a negative regulator of activated T cells, was transiently expressed on M72-specific CD4 T cells after vaccination. Specific T-cell subsets were present at significantly higher frequencies after vaccination of Mtb-infected versus -uninfected participants. CONCLUSIONS M72/AS01 is clinically well tolerated in Mtb-infected and -uninfected adults, induces high frequencies of multifunctional T cells, and boosts distinct T-cell responses primed by natural Mtb infection. Moreover, these results provide important novel insights into how this immunity may be appropriately regulated after novel TB vaccination of Mtb-infected and -uninfected individuals. Clinical trial registered with www.clinicaltrials.gov (NCT 00600782).

Dose-Finding Study of the Novel Tuberculosis Vaccine, MVA85A, in Healthy BCG-Vaccinated Infants

BACKGROUND BCG, the only licensed tuberculosis vaccine, affords poor protection against lung tuberculosis in infants and children. A new tuberculosis vaccine, which may enhance the BCG-induced immune response, is urgently needed. We assessed the safety of and characterized the T cell response induced by 3 doses of the candidate vaccine, MVA85A, in BCG-vaccinated infants from a setting where tuberculosis is endemic. METHODS  Infants aged 5-12 months were vaccinated intradermally with either 2.5 × 10(7), 5 × 10(7), or 10 × 10(7) plaque-forming units of MVA85A, or placebo. Adverse events were documented, and T-cell responses were assessed by interferon γ (IFN-γ) enzyme-linked immunospot assay and intracellular cytokine staining. RESULTS The 3 MVA85A doses were well tolerated, and no vaccine-related serious adverse events were recorded. MVA85A induced potent, durable T-cell responses, which exceeded prevaccination responses up to 168 d after vaccination. No dose-related differences in response magnitude were observed. Multiple CD4 T cell subsets were induced; polyfunctional CD4 T cells co-expressing T-helper cell 1 cytokines with or without granulocyte-macrophage colony-stimulating factor predominated. IFN-γ-expressing CD8 T cells, which peaked later than CD4 T cells, were also detectable. CONCLUSIONS MVA85A was safe and induced robust, polyfunctional, durable CD4 and CD8 T-cell responses in infants. These data support efficacy evaluation of MVA85A to prevent tuberculosis in infancy. Clinical Trials Registration. NCT00679159.

The novel tuberculosis vaccine, AERAS-402, is safe in healthy infants previously vaccinated with BCG, and induces dose-dependent CD4 and CD8T cell responses

BACKGROUND Efforts to reduce risk of tuberculosis disease in children include development of effective vaccines. Our aim was to test safety and immunogenicity of the new adenovirus 35-vectored tuberculosis vaccine candidate AERAS-402 in infants, administered as a boost following a prime with the Bacille Calmette-Guerin vaccine. METHODS In a phase 1 randomised, double-blind, placebo-controlled, dose-escalation trial, BCG-vaccinated infants aged 6-9 months were sequentially assigned to four study groups, then randomized to receive an increasing dose-strength of AERAS-402, or placebo. The highest dose group received a second dose of vaccine or placebo 56 days after the first. The primary study outcome was safety. Whole blood intracellular cytokine staining assessed immunogenicity. RESULTS Forty-two infants received AERAS-402 and 15 infants received placebo. During follow-up of 182 days, an acceptable safety profile was shown with no serious adverse events or discontinuations related to the vaccine. AERAS-402 induced a specific T cell response. A single dose of AERAS-402 induced CD4T cells predominantly expressing single IFN-γ whereas two doses induced CD4T cells predominantly expressing IFN-γ, TNF-α and IL-2 together. CD8T cells were induced and were more likely to be present after 2 doses of AERAS-402. CONCLUSIONS AERAS-402 was safe and immunogenic in healthy infants previously vaccinated with BCG at birth. Administration of the highest dose twice may be the most optimal vaccination strategy, based on the induced immunity. Multiple differences in T cell responses when infants are compared with adults vaccinated with AERAS-402, in the same setting and using the same whole blood intracellular cytokine assay, suggest specific strategies may be important for vaccination for each population.

Qualification of a whole blood intracellular cytokine staining assay to measure mycobacteria-specific CD4 and CD8 T cell immunity by flow cytometry.

BACKGROUND Qualified or validated assays are essential in clinical trials. Short-term stimulation of whole blood and intracellular cytokine staining assay is commonly used to measure immunogenicity in tuberculosis vaccine clinical trials. Previously, the short-term stimulation process of whole blood with BCG was optimized. We aimed to qualify the intracellular cytokine staining process and assess the effects of long-term cryopreservation. Our hypotheses were that the assay is robust in the measurement of the mycobacteria-specific T cells, and long-term cryopreservation of fixed cells from stimulated whole blood would not compromise reliable measurement of mycobacteria induced CD4 T cell immunity. METHODS Whole blood from healthy adults was collected in sodium heparinized tubes. The blood was left unstimulated or stimulated with mycobacterial antigens or mitogens for 12h. Cells were harvested, fixed and multiple aliquots from each participant cryopreserved. Later, mycobacteria-specific CD4 and CD8 T cells expressing IFN-γ, TNF-α, IL-2 and IL-17 were quantitated by flow cytometry. Assay performance characteristics evaluated included limit of quantification and detection, reproducibility, precision, robustness, specificity and sensitivity. To assess the effects of long-term cryopreservation, fixed cells from the stimulated bloods were analysed one week post-cryopreservation and at 3-month intervals over a 3-year period. RESULTS The limit of quantification for the different cytokines was variable: 0.04% for frequencies of IFN-γ- and IL-2-expressing T cells and less than 0.01% for TNF-α- and IL-17-expressing T cells. When measurement of the mycobacteria-specific T cells was assessed at levels above the detection limit, the whole blood intracellular cytokine assay showed high precision that was operator-independent. The assay was also robust: variation in staining conditions including temperature (4 °C or 20-23 °C) and time (45, 60 or 90 min) did not markedly affect quantification of specific T cells. Finally, prolonged periods of cryopreservation also did not significantly influence quantification of mycobacteria-specific CD4 T cells. CONCLUSIONS The whole blood intracellular cytokine assay is robust and reliable in quantification of the mycobacteria-specific T cells and is not significantly affected by cryopreservation of fixed cells.

Significantly skewed memory CD8+ T cell subsets in HIV-1 infected infants during the first year of life.

HIV-1 infection causes a severe T cell compromise; however, little is known about changes in naive, memory, effector and senescent T cell subsets during the first year of life. T cell subsets were studied over the first year of life in blood from 3 infant cohorts: untreated HIV-infected, HIV-exposed but uninfected, and HIV-unexposed. In HIV-infected infants, the frequency of CCR7(+)CD45RA(+) naive CD8(+) T cells was significantly decreased, while the frequency of CCR7(-)CD45RA(-) effector memory CD8(+) T cells was increased, compared with the control cohorts. A larger population of CD8(+) T cells in HIV-infected infants displayed a phenotype consistent with senescence. Differences in CD4(+) T cell subset frequencies were less pronounced, and no significant differences were observed between exposed and unexposed HIV-uninfected infants. We concluded that the proportion of naive, memory, effector and senescent CD8(+) T cells during the first year of life is significantly altered by HIV-1 infection.

Distinct T-Cell Responses When BCG Vaccination Is Delayed From Birth to 6 Weeks of Age in Ugandan Infants

BACKGROUND In Uganda, the tuberculosis vaccine BCG is administered on the first day of life. Infants delivered at home receive BCG vaccine at their first healthcare facility visit at 6 weeks of age. Our aim was to determine the effect of this delay in BCG vaccination on the induced immune response. METHODS We assessed CD4(+) and CD8(+) T-cell responses with a 12-hour whole-blood intracellular cytokine/cytotoxic marker assay, and with a 6-day proliferation assay. RESULTS We enrolled 92 infants: 50 had received BCG vaccine at birth and 42 at 6 weeks of age. Birth vaccination was associated with (1) greater induction of CD4(+) and CD8(+) T cells expressing either interferon γ (IFN-γ) alone or IFN-γ together with perforin and (2) induction of proliferating cells that had greater capacity to produce IFN-γ, tumor necrosis factor α (TNF-α), and interleukin 2 together, compared with delayed vaccination. CONCLUSIONS Distinct patterns of T-cell induction occurred when BCG vaccine was given at birth and at 6 weeks of age. We propose that this diversity might impact protection against tuberculosis. Our results differ from those of studies of delayed BCG vaccination in South Africa and the Gambia, suggesting that geographical and population heterogeneity may affect the BCG vaccine-induced T-cell response.

HIV-Specific Gag Responses in Early Infancy Correlate with Clinical Outcome and Inversely with Viral Load

Many HIV-infected infants progress to AIDS during the first year of life when antiretroviral therapy (ART) is not given. The immune determinants of progression to AIDS are not known. We hypothesized that distinct HIV-specific T cell responses correlate with viral load and survival over the first year of life. Whole blood of infants at 3, 6, 9, and 12 months of age was incubated with HIV antigens Gag and Env. The frequency of specific T cells producing interferon (IFN)-γ was then measured by flow cytometry. Viral load and CD4% in HIV(+) infants were determined at each time point. ART was not available for this population at the time of sample collection. Those infants who survived to 12 months of age (n=12) had lower viral loads and higher Gag-specific CD8(+) T cell responses at 3 months, compared with infants who died (n=8). Furthermore, the frequency of Gag-specific CD4(+) T cells correlated inversely with viral load at 3 and 6 months of age. Together these data indicate that the early presence of quantitatively higher Gag-specific T cell responses in HIV-infected infants is associated with lower viral loads and decreased mortality in the first year of life. Our data support the design of a vaccine that preferentially elicits Gag responses, which may result in lower levels of viremia and possibly improve outcome.