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PubMed2005

The role of adjuvants in the development of mucosal vaccines.

It is well-established that most pathogens that cause infectious diseases enter the host via mucosal membranes of the respiratory, digestive and genital tracts. Some parenterally administered vaccines induce protection against mucosal pathogens. However, there is increasing evidence that mucosal protection is better afforded by mucosal vaccination, particularly for the induction of memory responses. Mucosal vaccines must pass several difficult hurdles before entering the host and inducing an effective and protective immune response. This review deals with present and past efforts in devising effective mucosal vaccines using delivery systems and immunopotentiating adjuvants for protein-based vaccines. The paper will conclude with the authors' opinion on how the field will or should progress in the future and what will be the required components of ideal future mucosal vaccines that can induce immunological memory.

Adjuvants, Immunologic↗
PubMed1989

Characterization of a helper T lymphocyte defect in vitamin A-deficient mice.

Vitamin A-deficient mice exhibited sharply decreased IgG1 responses to protein Ag in vivo and in vitro. We traced the cellular basis for these impaired responses to a functional defect in A-deficient Th. Ag-presenting cells and B cells from A-deficient mice showed no functional defects. The A-deficient T cells proliferated normally in response to Ag but failed to provide the B cell stimulus for Ag-specific IgG1 responses. The A-deficient mice had fewer Th by limiting dilution analysis, and retinyl acetate supplementation in vitro restored Th frequency to control levels. Because added retinyl acetate reversed the Th functional block, these vitamin A-deficient T cells must be primarily defective in activation, not in establishment of immunologic memory.

Animals↗
PubMed1996

Reduction of otherwise remarkably stable virus-specific cytotoxic T lymphocyte memory by heterologous viral infections.

Experimental analyses of the acute cytotoxic T lymphocyte (CTL) response to viruses have focused on studying these infections in immunologically naive hosts. In the natural environment, however, viral CTL responses occur in hosts that are already immune to other infectious agents. To address which factors contribute to the maintenance and waning of immunological memory, the following study examined the frequencies of virus-specific CTL precursor cells (pCTL) not only using the usual experimental paradigm where mice undergo acute infections with a single virus, and in mice immune to a single virus, but also in immune mice after challenge with various heterologous viruses. As determined by limiting dilution assays, the pCTL frequency (p/f) per CD8+ T cell specific for lymphocytic choriomeningitis virus (LCMV), Pichinde virus (PV), or vaccinia virus (VV) increased during the acute infections, peaking at days 7-8 with frequencies as high as 1/27-1/74. Acute viral infections such as these elicit major expansions in the CD8+ T cell number, which has been reported to undergo apoptosis and decline after most of the viral antigen has been cleared. Although the decline in the total number of virus-specific pCTL after their peak in the acute infection was substantial, for all three viruses the virus-specific p/f per CD8+ T cell decreased only two- to fourfold and remained at these high levels with little fluctuation for well over a year. The ratios of the three immunodominant peptide-specific to total LCMV-specific clones remained unchanged between days 7 and 8 of acute infection and long-term memory, suggesting that the apoptotic events did not discriminate on the basis of T cell receptor specificity, but instead nonspecifically eliminated a large proportion of the activated T cells. However, when one to five heterologous viruses (LCMV, PV, VV, murine cytomegalovirus, and vesicular stomatitis virus) were sequentially introduced into this otherwise stable memory pool, the stability of the memory pool was disrupted. With each successive infection, after the immune system had returned to homeostasis, the memory p/f specific to viruses from earlier infections declined. Reductions in memory p/f were observed in all tested immunological compartments (spleen, peripheral blood, lymph nodes, and peritoneal cavity), and on average in the spleen revealed a 3 +/- 0.4-fold decrease in p/f after one additional viral infection and an 8.4 +/- 3-fold decrease after two additional viral infections. Thus, subsequent challenges with heterologous antigens, which themselves induce memory CTL, may contribute to the waning of CTL memory pool to earlier viruses as the immune system accommodates ever-increasing numbers of new memory cells within a limited lymphoid population. This demonstrates that virus infections do not occur in immunological isolation, and that CD8+ T cell responses are continually being modulated by other infectious agents.

Amino Acid Sequence↗
PubMed2005

Identification of T cell-restricted genes, and signatures for different T cell responses, using a comprehensive collection of microarray datasets.

We used a comprehensive collection of Affymetrix microarray datasets to ascertain which genes or molecules distinguish the known major subsets of human T cells. Our strategy allowed us to identify the genes expressed in most T cell subsets: TCR alphabeta+ and gammadelta+, three effector subsets (Th1, Th2, and T follicular helper cells), T central memory, T effector memory, activated T cells, and others. Our genechip dataset also allowed for identification of genes preferentially or exclusively expressed by T cells, compared with numerous non-T cell leukocyte subsets profiled. Cross-comparisons between microarray datasets revealed important features of certain subsets. For instance, blood gammadelta T cells expressed no unique gene transcripts, but did differ from alphabeta T cells in numerous genes that were down-regulated. Hierarchical clustering of all the genes differentially expressed between T cell subsets enabled the identification of precise signatures. Moreover, the different T cell subsets could be distinguished at the level of gene expression by a smaller subset of predictor genes, most of which have not previously been associated directly with any of the individual subsets. T cell activation had the greatest influence on gene regulation, whereas central and effector memory T cells displayed surprisingly similar gene expression profiles. Knowledge of the patterns of gene expression that underlie fundamental T cell activities, such as activation, various effector functions, and immunological memory, provide the basis for a better understanding of T cells and their role in immune defense.

Cluster Analysis↗
PubMed1997

[Fluke invasion and the immune system of the snail].

This is a review article concerning an influence of trematodes infections on a defence system of snails. Changes in: snails' plasma composition, a number of hemocytes, size of a hemopoietic organ, molecules secreted by hemocytes and defence cells activities caused by the infections are discussed in detail. The differences in humoral and cellular response between susceptible and resistant strains of snails as well as between young and old snails are also presented in the article. Finally, the problem of an existence of the specific immunological memory in snails is analyzed.

Animals↗
PubMed1981

Ontogeny of transplantation immunity in the common frog, Rana temporaria L.

Viability of allografts exchanged between the field-collected individuals of the common frog, R. temporaria, was long in tadpoles grafted during and immediately after closing of operculum; median survival time (MST) was 26 and 18 days, respectively. This probably reflected the immaturity of the host immune system and temporary tolerance to weak transplantation antigens. Allograft viability was the shortest in tadpoles grafted at foot-paddle stage (MST, 11 days). It was independent from the origin and size of the grafts. Such rate of rejection might reflect a maximal immunological potential of the host and the absence of any suppressor factors in response to highly polymorphic frog transplantation antigens. A gradual prolongation of allograft viability was observed in animals grafted at final stages of metamorphosis, in froglets, and in sexually mature adults (MST: 13, 17, and 28 days, respectively). In particular age groups viability of allografts from sibling donors was longer and from nonsibling ones shorter than MST values cited above. Immunological memory of transplantation antigens did not disappear during the host metamorphosis, as MST (10 days) of second-set allografts in metamorphosing hosts sensitized during larval life was considerably shorter than the viability of the sensitizing grafts in the same age group. The ontogeny of the response to alloantigens reflecting the immunological potential and the appearance of self-tolerance can be realized in different ways, depending on a particular amphibian species.

Animals↗
PubMed2003

Cutting edge: long-term B cell memory in humans after smallpox vaccination.

Memory B cells are a central component of humoral immunity, and yet little is known about their longevity in humans. Immune memory after smallpox vaccination (DryVax) is a valuable benchmark for understanding the longevity of B cell memory in the absence of re-exposure to Ag. In this study, we demonstrate that smallpox vaccine-specific memory B cells last for >50 years in immunized individuals. Virus-specific memory B cells initially declined postimmunization, but then reached a plateau approximately 10-fold lower than peak and were stably maintained for >50 years after vaccination at a frequency of approximately 0.1% of total circulating IgG(+) B cells. These persisting memory B cells were functional and able to mount a robust anamnestic Ab response upon revaccination. Additionally, virus-specific CD4(+) T cells were detected decades after vaccination. These data show that immunological memory to DryVax vaccine is long-lived and may contribute to protection against smallpox.

Adolescent↗
PubMed1987

Increased activation of antigen-primed or memory B cells by bacterial lipopolysaccharide.

Treatment with bacterial lipopolysaccharide elicits the appearance of greater numbers of background antigen-specific plaque-forming cells (PFC) in the spleens of mice previously exposed or primed to subimmunogenic amounts of various non-cross-reacting antigens so as to generate detectable immunological memory. These findings suggest that treatment with lipopolysaccharide results in the activation of increased numbers of antigen-primed or memory B cells in mice previously exposed to antigen.

Animals↗
PubMed2006

Memory T and memory B cells share a transcriptional program of self-renewal with long-term hematopoietic stem cells.

The only cells of the hematopoietic system that undergo self-renewal for the lifetime of the organism are long-term hematopoietic stem cells and memory T and B cells. To determine whether there is a shared transcriptional program among these self-renewing populations, we first compared the gene-expression profiles of naïve, effector and memory CD8(+) T cells with those of long-term hematopoietic stem cells, short-term hematopoietic stem cells, and lineage-committed progenitors. Transcripts augmented in memory CD8(+) T cells relative to naïve and effector T cells were selectively enriched in long-term hematopoietic stem cells and were progressively lost in their short-term and lineage-committed counterparts. Furthermore, transcripts selectively decreased in memory CD8(+) T cells were selectively down-regulated in long-term hematopoietic stem cells and progressively increased with differentiation. To confirm that this pattern was a general property of immunologic memory, we turned to independently generated gene expression profiles of memory, naïve, germinal center, and plasma B cells. Once again, memory-enriched and -depleted transcripts were also appropriately augmented and diminished in long-term hematopoietic stem cells, and their expression correlated with progressive loss of self-renewal function. Thus, there appears to be a common signature of both up- and down-regulated transcripts shared between memory T cells, memory B cells, and long-term hematopoietic stem cells. This signature was not consistently enriched in neural or embryonic stem cell populations and, therefore, appears to be restricted to the hematopoeitic system. These observations provide evidence that the shared phenotype of self-renewal in the hematopoietic system is linked at the molecular level.

B-Lymphocytes↗
PubMed1999

Distribution of human CMV-specific memory T cells among the CD8pos. subsets defined by CD57, CD27, and CD45 isoforms.

Chronic antigenic stimulation has been associated with peripheral blood expansions of CD8pos. T cells characterized by CD57 expression, loss of CD27 expression, and reversal of the CD45RO(bright) /RA(dim) phenotype usually associated with immunological memory towards a CD45RO(dim) /RA(bright) phenotype. However, the relationship and functional significance of these subset(s) has remained controversial. Here, this issue was addressed using a novel flow cytometric technique that allows simultaneous detection of human cytomegalovirus (HCMV)-specific CD8pos. memory T cells by rapid (< 6 h) HCMV peptide-specific induction of cytokine synthesis, and their phenotypic characterization, including CD57, CD27 and CD45RA/RO. The vast majority of resting CD8(pos.) T cells capable of rapid induction of IFN-gamma and TNF-alpha synthesis in response to HCMV peptides were found in a subset characterized by intermediate to high expression of CD57, down-regulation/loss of CD27, and varying degrees of reversal of the classical "memory" CD45RO(bright) /RA(dim) phenotype. This subpopulation likely includes the fully differentiated memory cells responsible for the long-term immune defense against HCMV reactivation.

Antigens, CD↗
PubMed2004

Impeded Th1 CD4 memory T cell generation in chronic-persisting liver infection with Echinococcus multilocularis.

Memory T cells of the CD4 lineage coordinate immune responses against pathogens via the antigen-induced secretion of potent effector cytokines. The efficacy of these responses is thought to depend on both the overall number of pathogen-specific memory T cells and the particular array of cytokines that these cells are programmed to secrete. It is unknown to what extent cellular immunity can be induced by Echinococcus multilocularis infection. To examine the immunological memory provided by the adaptive cellular immune system in control of the chronic-persisting infection, peripheral lymphocytes of patients with alveolar echinococcosis (AE) were studied ex vivo. Stimulation of memory cells was performed with E. multilocularis vesicular fluid, purified protein derivative as recall antigen and phytohemagglutinin. Cytomegalovirus latency served as disease control. Frequencies of circulating CD4(+) T cells secreting IFN-gamma, IL-2, tumor necrosis factor-alpha, IL-4, IL-5 and IL-10 were determined by both cytokine flow cytometry and ELISPOT assays. Most strikingly, in chronic AE the frequencies of E. multilocularis antigen-specific cells committed to T(h)1-cytokine production were low (mean 0.5% of CD4(+) T cells). However, an E. multilocularis-specific response of CD4(+) T cells at frequencies of >/=0.1% was detected in the majority of AE patients (68%). Low numbers of cells committed to T(h)1 cytokine secretion were invariably seen in patients with active and inactive disease. Interestingly, the number of specific CD4(+) memory T cells was not increased in cured AE patients after complete surgical removal of the metacestode. Hyporesponsiveness during the chronic helminth infection was E. multilocularis specific. Thus, our results demonstrate that antigen-specific memory function against E. multilocularis is markedly different from that against viral or bacterial pathogens. Whether the antigen-specific cellular hyporesponsiveness with impeded T(h)1 CD4(+) memory T cell generation is a cause or a result of the progressive metacestode activity remains to be determined.

Adult↗
PubMed1997

Distinct costimulatory molecules are required for the induction of effector and memory cytotoxic T lymphocytes.

A successful T cell immune response has two major products: effector T cells which directly or indirectly remove the antigens, and memory T cells, which allow a faster and more efficient recall response when challenged by related antigens. An important issue is whether costimulatory molecules on the antigen-presenting cells are involved in determining whether T cells will differentiate into effector or memory cells after antigenic stimulation. To address this issue, we have produced mice with targeted mutations of either the heat-stable antigen (HSA), or both HSA and CD28. We show that CD28/B7 and HSA provide two alternative costimulatory pathways for induction of immunological memory to influenza virus. Furthermore, our results revealed that B7 is essential for the generation of effector T cells from either naive or memory T cells, while HSA is not necessary for the generation of effector T cells. Our results demonstrate that the induction of memory T cells and effector T cells can utilize distinct costimulatory molecules. These results have important implications on lineage relationship between effector and memory T cells.

Animals↗
PubMed2006

Critical roles of memory T cells and antidonor immunoglobulin in rejection of allogeneic bone marrow cells in sensitized recipient mice.

BACKGROUND: Allosensitization is a major risk factor for graft failure in clinical bone marrow transplantation, even with an human leukocyte antigen (HLA)-matched combination under radiation-based conditioning regimens. The critical components of immunological memory in donor bone marrow graft rejection in allosensitized hosts remain unclear at present. METHODS: C57BL/6-recipient mice, which had been intraperitoneally injected with splenocytes from donor C3H mice on day -35 (sensitized recipients), had been lethally irradiated with 10-Gy whole-body irradiation and were intravenously injected with T-cell-depleted bone marrow cells (TCD-BMC) from C3H mice or third-party SJL mice. RESULTS: Lethally irradiated recipient mice, which had been sensitized by donor splenocytes 5 weeks before the transplantation of TCD-BMC, completely rejected the donor-BMC in a donor-specific manner, whereas none of the nonsensitized recipient mice, all of which showed full allogeneic chimerism, rejected the donor TCD-BMC. Antibody-mediated T cell and/or Natural Killer (NK) cell depletion did not improve the ability of the sensitized recipients to overcome the rejection even when a megadose of TCD-BMC was administered to the sensitized recipients. Furthermore, BMC rejection occurred in sensitized B cell-deficient mice. In adoptive transfer experiments, naive mice, which received a transfer of purified T cells from sensitized mice, rejected the donor BMC, but not those from nonsensitized mice. Moreover, naive mice, which received a transfer of serum containing antidonor immunoglobulin, rejected the donor BMC. CONCLUSIONS: These findings suggest that alloreactive memory T cells and antidonor immunoglobulin independently function to reject donor BMC in sensitized recipients.

Adoptive Transfer↗
PubMed2003

Response to smallpox vaccine in persons immunized in the distant past.

CONTEXT: There is renewed interest in use of smallpox vaccine due to the potential for a bioterrorist attack. This would involve vaccinating health care workers who were previously vaccinated. OBJECTIVE: To evaluate the use of diluted vaccinia virus in vaccination of previously vaccinated (non-naive) participants. DESIGN, SETTING, AND PARTICIPANTS: Eighty non-naive participants, aged 32 to 60 years, were randomized in a single-blinded study to receive either undiluted or diluted (1:3.2, 1:10, or 1:32) doses of smallpox vaccine. A comparison group, aged 18 to 31 years, of 10 vaccinia-naive participants received undiluted vaccine. Participants were enrolled between April 1 and May 15, 2002, at the National Institute of Allergy and Infectious Diseases Vaccine and Treatment Evaluation Unit at Saint Louis University, St Louis, Mo. INTERVENTION: Smallpox vaccine was administered by scarification using 15 skin punctures in the deltoid region of the arm. MAIN OUTCOME MEASURES: Presence of a major reaction, defined as a vesicular or pustular lesion or area of palpable induration surrounding a central lesion following vaccination, and measures of viral shedding and antibody titers. RESULTS: Initial vaccination resulted in a major reaction in 64 of 80 non-naive participants. Ninety-five percent of non-naive participants had major reactions in the undiluted group, 90% in the 1:3.2 dilution group, 81% in the 1:10 dilution group, and 52.6% in the 1:32 dilution group. All (n = 10) of the vaccinia-naive participants had major reactions. Compared with vaccinia-naive participants, non-naive participants had significantly smaller skin lesions (P =.04) and significantly less incidence of fever (P =.02). Preexisting antibody was present in 76 of 80 non-naive participants. Antibody responses were significantly higher and occurred more rapidly in the non-naive participants compared with the vaccinia-naive participants (P =.002 for day 28 and P =.003 for 6 months). Vaccinia-naive participants shed virus from the vaccination site 2 to 6 days longer and had significantly higher peak mean viral titers when compared with the non-naive participants (P =.002). CONCLUSIONS: Previously vaccinated persons can be successfully revaccinated with diluted (<or=1:10) smallpox vaccine. Fewer adverse reactions were observed in this study of non-naive participants when compared with events in vaccinia-naive participants, which may be due to immunologic memory.

Adult↗
PubMed1978

Competition of the actions of antigen and polyclonal B-cell activator in the induction and amplification of B-memory cell function.

Using the capsular polysaccharide of Klebsiella pneumoniae (CPS-K) as a polyclonal B-cell activator (PBA) and sheep red blood cells (SRBC) as a T-dependent antigen, the correlation of the actions of PBA and T-dependent antigen on B cells in induction and amplification of immunological memory was studied. B-memory cell function, as judged by anti-SRBC responsiveness in vitro of spleen cells of CPS-K, was amplified by the secondary injection of SRBC into SRBC-primed mice, whereas it was decreased markedly by injection of CPS-K. When CPS-K was injected simultaneously with, or 1 or 2 days before the secondary injection of SRBC, B-memory cell function was also decreased markedly. On the other hand, CPS-K did not inhibit induction of B-memory cell function when injected simultaneouly with the primary injection of SRBC. However, CPS-K inhibited induction of B-memory cell function when injected 3 days before the primary injection of SRBC. The inhibition by CPS-K of amplification of B-memory cell function in response to SRBC when CPS-K was injected simultaneously with the secondary injection of SRBC occurred markedly in mice primed with SRBC 8 days or longer before the secondary injection, whereas it was not detectable in mice primed 3 days before. It is concluded that the CPS-K-mediated signal and the SRBC-mediated signal act competitively on the same subpopulations of B cells in induction and amplification of memory, and that the susceptibility of B cells to the CPS-K-mediated negative signal changes correspondingly with their maturation stage.

Animals↗
PubMed1993

A theoretical framework for immune responses and predisposition to helminth infection.

Many field studies of human helminth infections have reported a positive correlation between parasite burdens and the rate of re-establishment of infection following chemotherapy, i.e., predisposition. Some studies have also reported the relationships between re-establishment and exposure and immune responses. The interpretation of these data is made difficult by the complexity of the underlying immunoepidemiological processes. In this paper, simple mathematical models are used to explore expected patterns, especially in relation to host age. These patterns are determined by rates of infection, parasite life expectancy, the level of immunological responsiveness, the duration of immunological memory, and may be greatly affected by the immunogenic roles of different parasite stages. In general, acquired immunity is predicted to reduce the degree of predisposition. This reduction is age-dependent and may generate 'negative predisposition' in some age classes. Age-dependent reductions in the correlation between re-establishment and exposure are also predicted. The correlation between re-establishment and protective immune responses is also predicted to be age-dependent, but may remain positive for all ages despite significant acquired immunity. The results suggest that great care is needed in the interpretation of immunoepidemiological data from treatment-reinfection studies.

Adolescent↗
PubMed1994

The secondary B cell lineage for phosphorylcholine is conserved in CBA/CaHN-xid/J mice.

In order to determine the mechanism of generation of immunological memory, we used the splenic focus assay to analyze primary and in vitro generated secondary phosphorylcholine (PC)-specific B cell precursors in CBA/CaHN-xid/J mice (CBA/N) expressing an X-linked immune defect (xid). A quantitative analysis of the kinetics of the appearance of these precursors over the time of the culture period was performed. The precursors were analyzed for TEPC15 idiotype expression and epitope specificity. We found that there was a significantly reduced total frequency of PC-specific precursors in CBA/N female and (CBA/CaHN-xid/J female x BALB/cRos male)F1 (NBF1) male mice (xid phenotype), relative to BALB/c and NBF1 female mice (normal phenotype). Memory precursors representing a distinct lineage of B cells, however, were present at normal levels in CBA/N female and NBF1 male mice. These results help explain the reported characteristics of the serum antibody responses induced in these mice and also better our understanding of the mechanism of B cell memory generation.

Animals↗
PubMed2002

Vaccinology for control of apicomplexan parasites: a simplified language of immune programming and its use in vaccine design.

Most mammalian immune systems and parasites have co-evolved over the millennia, interacting within a common environment and communicating through a common language. This language is comprised of copious dialects in which a variety of host innate and acquired immune pathways actively interact with a multitude of parasite-specific survival strategies. Nonetheless, a simplified language is likely present since the same basic molecular and cellular mechanisms are associated with resistance or susceptibility to parasite infection. Protective immunity against protozoa within the phylum Apicomplexa (e.g. Cryptosporidia, Eimeria, Neospora, Plasmodia and Toxoplasma) is generally CD4+ T cell-dependent and elicited along the IL-12/IFN-gamma/iNOS effector axis. This simplified language can be decoded in part by significant advances in understanding naïve T cell activation, differentiation and generation of immunologic memory. Vaccine adjuvants and new immunisation strategies for generation of more potent immunity can also be viewed through this common language lens. The aim of this paper is to summarise recently published fundamental immunology studies, their relevance through examples in specific coccidian-host immune dialects, and how this simplified language can be used for the more rationale design of parasite vaccine control strategies.

Adjuvants, Immunologic↗