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Biomedical subjects

K J Maloy

Publications and source records attributed to K J Maloy.

14 recordsLinked to original sources
PubMed2001

Intralymphatic immunization enhances DNA vaccination.

Although DNA vaccines have been shown to elicit potent immune responses in animal models, initial clinical trials in humans have been disappointing, highlighting a need to optimize their immunogenicity. Naked DNA vaccines are usually administered either i.m. or intradermally. The current study shows that immunization with naked DNA by direct injection into a peripheral lymph node enhances immunogenicity by 100- to 1,000-fold, inducing strong and biologically relevant CD8(+) cytotoxic T lymphocyte responses. Because injection directly into a lymph node is a rapid and easy procedure in humans, these results have important clinical implications for DNA vaccination.

Animals↗
PubMed2001

Regulatory T cells in the control of immune pathology.

It is now well established that regulatory T (T(R)) cells can inhibit harmful immunopathological responses directed against self or foreign antigens. However, many key aspects of T(R) cell biology remain unresolved, especially with regard to their antigen specificities and the cellular and molecular pathways involved in their development and mechanisms of action. We will review here recent findings in these areas, outline a model for how T(R) cells may inhibit the development of immune pathology and discuss potential therapeutic benefits that may arise from the manipulation of T(R) cell function.

Abatacept↗
PubMed2000

CD4(+) T cell subsets during virus infection. Protective capacity depends on effector cytokine secretion and on migratory capability.

To analyze the antiviral protective capacities of CD4(+) T helper (Th) cell subsets, we used transgenic T cells expressing an I-A(b)-restricted T cell receptor specific for an epitope of vesicular stomatitis virus glycoprotein (VSV-G). After polarization into Th1 or Th2 effectors and adoptive transfer into T cell-deficient recipients, protective capacities were assessed after infection with different types of viruses expressing the VSV-G. Both Th1 and Th2 CD4(+) T cells could transfer protection against systemic VSV infection, by stimulating the production of neutralizing immunoglobulin G antibodies. However, only Th1 CD4(+) T cells were able to mediate protection against infection with recombinant vaccinia virus expressing the VSV-G (Vacc-IND-G). Similarly, only Th1 CD4(+) T cells were able to rapidly eradicate Vacc-IND-G from peripheral organs, to mediate delayed-type hypersensitivity responses against VSV-G and to protect against lethal intranasal infection with VSV. Protective capacity correlated with the ability of Th1 CD4(+) T cells to rapidly migrate to peripheral inflammatory sites in vivo and to respond to inflammatory chemokines that were induced after virus infection of peripheral tissues. Therefore, the antiviral protective capacity of a given CD4(+) T cell is governed by the effector cytokines it produces and by its migratory capability.

Adoptive Transfer↗
PubMed2000

Induction of optimal anti-viral neutralizing B cell responses by dendritic cells requires transport and release of virus particles in secondary lymphoid organs.

Dendritic cells (DC) are sentinels of the immune system, transporting antigens from the periphery to secondary lymphoid organs. This study investigates the interactions of DC with B cells for the induction of anti-viral neutralizing antibody responses. Using the vesicular stomatitis virus glycoprotein (VSV-G) as a model antigen, we show that DC contain infection with cytopathic VSV in the presence of a functional IFN system, facilitating transport and release of low levels of live virus in secondary lymphoid organs. DC exposed to live virus induced efficient neutralizing anti-viral B cell responses. In contrast, DC transporting UV-inactivated viral antigens were poor activators of anti-viral B cells, although they were capable of very efficiently inducing virus-specific Th cells. Transgenic DC expressing a membrane-bound form of VSV-G induced neutralizing B cell responses; however, this DC-induced, Th-dependent B cell response was significantly slower than the anti-viral B cell response induced by DC infected with live VSV, and was strongly dependent on concomitant priming of T help. These results suggest that DC may play a double role during infection with cytopathic virus: they transport and release live virus in secondary lymphoid tissues for optimal direct B cell induction and offer MHC class II-associated determinants for induction of T help.

Animals↗
PubMed2000

T1-deficient and T1-Fc-transgenic mice develop a normal protective Th2-type immune response following infection with Nippostrongylus brasiliensis.

The IL-1 receptor-related protein T1 is expressed on the surface of Th2, but not Th1 cells. Studies with anti-T1 monoclonal antibodies have suggested that T1 is critical for development of normal Th2-type responses. To elucidate the role of T1 in vivo, we generated T1-deficient mice and a T1-transgenic strain which secretes soluble T1-Fc fusion protein into the serum. These were analyzed for the Th2 immune response induced by infection with the parasitic nematode Nippostrongylus brasiliensis. Although Th2 cytokine production by lymph node cells was similar in all groups of N. brasiliensis-infected mice, a decrease in IL-5 production by lung lymphocytes was detected in both T1-deficient and T1-Fc-transgenic mice compared to control littermates. This difference in IL-5 production did not influence blood eosinophilia, but recruitment of eosinophils into lung tissue, especially in T1-Fc-transgenic mice was slightly decreased. However, induction of all other immune parameters was normal and both T1-deficient and T1-Fc-transgenic mice were able to clear the parasite infection within 12 days with kinetics similar to those in control mice. Therefore, in contrast to previous suggestions, we conclude that the T1 protein is not obligatory for normal development of Th2 immune responses.

Animals↗
PubMed1999

Qualitative and quantitative requirements for CD4+ T cell-mediated antiviral protection.

CD4+ Th cells deliver the cognate and cytokine signals that promote the production of protective virus-neutralizing IgG by specific B cells and are also able to mediate direct antiviral effector functions. To quantitatively and qualitatively analyze the antiviral functions of CD4+ Th cells, we generated transgenic mice (tg7) expressing an MHC class II (I-Ab)-restricted TCR specific for a peptide derived from the glycoprotein (G) of vesicular stomatitis virus (VSV). The elevated precursor frequency of naive VSV-specific Th cells in tg7 mice led to a markedly accelerated and enhanced class switching to virus-neutralizing IgG after immunization with inactivated VSV. Furthermore, in contrast to nontransgenic controls, tg7 mice rapidly cleared a recombinant vaccinia virus expressing the VSV-G (Vacc-IND-G) from peripheral organs. By adoptive transfer of naive tg7 CD4+ T cells into T cell-deficient recipients, we found that 105 transferred CD4+ T cells were sufficient to induce isotype switching after challenge with a suboptimal dose of inactivated VSV. In contrast, naive transgenic CD4+ T cells were unable to adoptively confer protection against peripheral infection with Vacc-IND-G. However, tg7 CD4+ T cells that had been primed in vitro with VSV-G peptide were able to adoptively transfer protection against Vacc-IND-G. These results demonstrate that the antiviral properties of CD4+ T cells are governed by the differentiation status of the CD4+ T cell and by the type of effector response required for virus elimination.

Adoptive Transfer↗
PubMed1999

Variable immune response against a developmentally regulated self-antigen.

We studied the reactivity of T and B cells against a soluble form of the glycoprotein of vesicular stomatitis virus (VSV-G) which was expressed in a transgenic mouse (line 23) under the control of the hormone regulated beta-lactoglobulin promoter. Transgenic mice expressed VSV-G in the thymus, spleen, mammary gland and lung. VSV-G transcripts in the thymus varied with age, i.e., expression was high early in life and decreased with age. VSV-G transgenic mice immunized with recombinant vaccinia virus expressing VSV-G exhibited normal VSV-G-specific IgM levels, but a 30-fold reduction in IgG response, indicating functional VSV-G-specific B cell activity but impaired T helper cell responses. Interestingly, VSV-G-specific T helper cell activity was reduced only early (4-10 weeks) and late in life (>40 weeks) but was normal in between. Double transgenic mice expressing VSV-G and a VSV-G-specific TCR (line 23x7) demonstrated that TCR transgenic CD4(+) T cells were partially deleted in early life, but then gradually repopulated the periphery and remained constant. These findings suggest that in line 23 two different mechanisms regulated levels of the immune response: clonal reduction/deletion of VSV-G-specific T cells during early life followed by peripheral anergy at a later stage.

Aging↗
PubMed1998

Interferon gamma-producing gammadelta T cell-dependent antibody isotype switching in the absence of germinal center formation during virus infection.

Ig class switching usually occurs as a consequence of cognate interactions between antigen-specific B cells and CD4(+) alphabeta T cells. Vesicular stomatitis virus (VSV) infection of immunocompetent mice induces a rapid T-independent neutralizing IgM response followed by a long-lived T-dependent IgG response. Surprisingly, alphabeta T cell-deficient (TCRalpha-/-) mice also produced neutralizing IgG antibodies when infected with live VSV or with a recombinant vaccinia virus expressing the VSV glycoprotein (Vacc-IND-G), but not when immunized with UV-inactivated VSV (UV-VSV). The neutralizing IgG responses did not require the presence of NK cells or complement, but were crucially dependent on IFN-gamma and were predominantly of the IgG2a isotype. IgG production depended on residual CD3(+) non-alphabeta T cell populations present in the TCRalpha-/- mice, which produced IFN-gamma upon in vitro stimulation. A key role for gammadelta T cells was confirmed by the fact that TCRbeta-/- mice also generated strong neutralizing IgG responses to VSV, whereas TCRbeta-/-delta-/- mice produced very low titers. The neutralizing IgG responses of TCRalpha-/- mice were accompanied by the development of memory B cells, but not by antigen-specific germinal center (GC) formation. Thus, during viral infection of alphabeta T cell-deficient mice, gammadelta T cells may provide the signals that are required for isotype switching.

Animals↗
PubMed1995

Induction of Th1 and Th2 CD4+ T cell responses by oral or parenteral immunization with ISCOMS.

We examined the ability of oral or parenteral immunization with immune stimulating complexes containing ovalbumin (ISCOMS-OVA) to prime T cell proliferative and cytokine responses. A single subcutaneous immunization with ISCOMS-OVA primed potent antigen-specific proliferative responses in the draining popliteal lymph node, which were entirely dependent on the presence of CD4+ T cells. CD8+ T cells did not proliferate in vitro even in the presence of the appropriate peptide epitope and exogenous interleukin (IL)-2. Primed popliteal lymph node cells produced IL-2, IL-5 and interferon (IFN)-gamma, but not IL-4 when restimulated with OVA in vitro. Serum antigen-specific IgG1 and IgG2a antibody responses were also primed by subcutaneous immunization with ISCOMS-OVA, confirming the stimulation of both Th1 and Th2 cells in vivo. Spleen cells from subcutaneously primed mice produced a similar pattern of cytokines, indicating that disseminated priming had occurred. Oral immunization with ISCOMS-OVA also primed local antigen-specific proliferative responses in the mesenteric lymph node and primed an identical pattern of systemic cytokine responses in the spleen. The ability of ISCOMS to prime both Th1 and Th2 CD4+ T cell responses may be central to their potent adjuvant activities and confirm the potential of ISCOMS as future oral vaccine vectors.

Administration, Oral↗
PubMed1994

Induction of mucosal and systemic immune responses by immunization with ovalbumin entrapped in poly(lactide-co-glycolide) microparticles.

We have examined the range of mucosal and systemic immune responses induced by oral or parenteral immunization with ovalbumin (OVA) entrapped in poly(D,L-lactide-co-glycolide) (PLG) microparticles. A single subcutaneous immunization with OVA-PLG primed significant OVA-specific IgG and delayed-type hypersensitivity (DTH) responses. The DTH responses were of similar magnitude to those obtained using immunostimulating complexes (ISCOMS) as a potent control adjuvant, although ISCOMS stimulated higher serum IgG responses. Both vectors also primed OVA-specific in vitro proliferative responses in draining lymph node cells following a single immunization and strong OVA-specific CTL responses were found after intraperitoneal (i.p.) immunization. ISCOMS were more efficient in inducing cytotoxic T lymphocytes (CTL), requiring much less antigen and only ISCOMS could stimulate primary OVA-specific CTL responses in the draining lymph nodes. Multiple oral immunizations with OVA in PLG microparticles or in ISCOMS resulted in OVA-specific CTL responses and again ISCOMS seemed more potent as fewer feeds were necessary. Lastly, multiple feeds of OVA in PLG microparticles generated significant OVA-specific intestinal IgA responses. This is the first demonstration that PLG microparticles can stimulate CTL responses in vivo and our results highlight their ability to prime a variety of systemic and mucosal immune responses which may be useful in future oral vaccine development.

Adjuvants, Immunologic↗
PubMed1993

Immune-stimulating complexes as adjuvants for inducing local and systemic immunity after oral immunization with protein antigens.

Orally active synthetic vaccines containing purified antigens would have many benefits for immunizing against systemic and mucosal diseases. However, several factors have limited the development of such vaccines, including the poor immunogenicity of purified proteins and their usual ability to induce tolerance when given orally. Here, we show that incorporation of ovalbumin (OVA) into immune-stimulating complexes (ISCOMS) containing saponin prevents the induction of oral tolerance in mice. In parallel, the spleen and mesenteric lymph node of mice fed OVA ISCOMS are primed for class I major histocompatibility complex (MHC)-restricted cytotoxic T-cell activity which recognizes physiologically processed epitopes on OVA. Oral immunization with OVA ISCOMS also stimulates high secretory IgA antibody responses in the intestine itself, as well as serum IgG antibodies. None of these active immune responses are detectable in mice fed OVA alone. Despite the potent priming of mucosal priming by OVA ISCOMS, re-exposure to antigen does not induce the intestinal immunopathology found in other systems after the breakdown of oral tolerance. Thus, ISCOMS have several unique properties as vectors for oral immunization and could provide a basis for future mucosal vaccines.

Adjuvants, Immunologic↗
PubMed1991

Phenotypic heterogeneity of intraepithelial T lymphocytes from mouse small intestine.

We have used two-colour flow cytometry to examine the heterogeneity of intraepithelial lymphocytes (IEL) from mouse small intestine. We have confirmed the predominance of CD3+ Thy 1- CD8+ IEL and show that a substantial but variable proportion of CD8+ IEL does not express the alpha beta T-cell receptor (TcR) for antigen. Simultaneous analysis of the co-expression of the alpha and beta chains of the CD8 heterodimer and of the alpha beta TcR revealed three populations of CD8+IEL. The first of these expressed both CD8 alpha and beta chains and had normal expression of V beta families and so represented conventional CD8+ alpha beta TcR+ T cells. The second population comprised alpha beta TcR- T cells (presumed gamma delta TcR+) which expressed only the alpha chain of the CD8 molecule. Finally, we identified a second, unique population of alpha beta TcR+ CD8+ IEL which were also CD8 beta-. Gamma delta + IEL predominated in mice aged less than 8 weeks, but there was a rapid increase in both populations of alpha beta TcR+ CD8+ IEL in older mice. CD8+ IEL were similar to peripheral CD8+ T cells in having high expression of the CD45RB molecule, but CD4+ IEL had generally lower expression of CD45RB than their peripheral counterparts, despite having normal expression of TcR. These findings emphasize the heterogeneity of IEL and underline the need to study phenotypically defined populations.

Aging↗