Biomedical subjects

P C Doherty

Publications and source records attributed to P C Doherty.

At least 37 records · Page 2Linked to original sources

PubMed2000

Inhibition of MHC class I-restricted antigen presentation by gamma 2-herpesviruses.

The gamma-herpesviruses, in contrast to the alpha- and beta-herpesviruses, are not known to inhibit antigen presentation to CD8(+) cytotoxic T lymphocytes (CTLs) during lytic cycle replication. However, murine gamma-herpesvirus 68 causes a chronic lytic infection in CD4(+) T cell-deficient mice despite the persistence of a substantial CTL response, suggesting that CTL evasion occurs. Here we show that, distinct from host protein synthesis shutoff, gamma-herpesvirus 68 down-regulates surface MHC class I expression on lytically infected fibroblasts and inhibits their recognition by antigen-specific CTLs. The viral K3 gene, encoding a zinc-finger-containing protein, dramatically reduced the half-life of nascent class I molecules and the level of surface MHC class I expression and was by itself sufficient to block antigen presentation. The homologous K3 and K5 genes of the related Kaposi's sarcoma-associated virus also inhibited antigen presentation and decreased cell surface expression of HLA class I antigens. Thus it appears that an immune evasion strategy shared by at least two gamma-herpesviruses allows continued lytic infection in the face of strong CTL immunity.

3T3 Cells↗

PubMed2000

The terminology problem for T cells: a discussion paper.

The school of thought that owes allegiance to Ludwig Wittgenstein teaches that language conditions perceptions. When we use the term 'cytotoxic T lymphocyte' or 'helper T cell' we tend to orientate our own thinking processes, and those of listeners or readers, down particular paths. Part of the problem is that we are often describing cell populations by functions that may either be a property of only a proportion of those that are being assayed, or are simply inferred from the expression of various cell-surface markers. The consequence can be a measure of confusion that might be avoided if we could communicate with greater clarity. Is it possible to achieve a better terminology that will be accepted generally? The following are some examples of why there may be some value in thinking about this.

Hypersensitivity, Delayed↗

PubMed2000

Postexposure vaccination massively increases the prevalence of gamma-herpesvirus-specific CD8+ T cells but confers minimal survival advantage on CD4-deficient mice.

Mice that lack CD4(+) T cells remain clinically normal for more than 60 days after respiratory challenge with the murine gamma-herpesvirus 68 (gammaHV-68), then develop symptoms of a progressive wasting disease. The gammaHV-68-specific CD8(+) T cells that persist in these I-A(b-/-) mice are unable to prevent continued, but relatively low level, virus replication. Postexposure challenge with recombinant vaccinia viruses expressing gammaHV-68 lytic cycle epitopes massively increased the magnitude of the gammaHV-68-specific CD8(+) population detectable by staining with tetrameric complexes of MHC class I glycoprotein + peptide, or by interferon-gamma production subsequent to in vitro restimulation with peptide. The boosting effect was comparable for gammaHV-68-infected I-A(b-/-) and I-A(b+/+) mice within 7 days of challenge, and took more than 110 days to return to prevaccination levels in the I-A(b+/+) controls. Although the life-span of the I-A(b-/-) mice was significantly increased, there was no effect on long-term survival. A further boost with a recombinant influenza A virus failed to improve the situation. Onset of weight loss was associated with a decline in gammaHV-68-specific CD8(+) T cell numbers, though it is not clear whether this was a cause or an effect of the underlying pathology. Even very high levels of virus-specific CD8(+) T cells thus provide only transient protection against the uniformly lethal consequences of gammaHV-68 infection under conditions of CD4(+) T cell deficiency.

Animals↗

PubMed2000

Analysis of the virus-specific and nonspecific B cell response to a persistent B-lymphotropic gammaherpesvirus.

Respiratory challenge of mice with murine gammaherpesvirus 68 (gammaHV68) results in acute replication in respiratory epithelial cells and persistent, latent infection of B cells and macrophages. gammaHV68 elicits virus-specific Ab, and also nonspecifically activates B cells to Ab production through a CD4+ T cell-dependent process. The current analysis characterizes virus-specific and nonspecific Ab production at the single cell level and investigates the requirements and nature of the nonspecific response. Virus-specific Ab-forming cell (AFC) numbers were dwarfed by the increase in total AFC in all sites examined, indicating substantial nonspecific Ab production. Clear increases and decreases in specific and total AFC numbers occurred in the lymph nodes draining the respiratory tract and the spleen, but AFC numbers in the bone marrow (BM) increased to a plateau and remained constant. The longevity of the BM response was reflected in a sustained increase in virus-specific and total serum Ab levels. Generally, the IgG2a and IgG2b isotypes predominated. Analysis of cytokine-deficient mice, CD40 ligand-deficient mice, and radiation BM chimeras lacking MHC class II expression specifically on B cells indicated that nonspecific Ab production is independent of IL-6 or IFN-gamma, and dependent on cognate CD4+ T cell help. Several observations were consistent with polyclonal B cell activation by gammaHV68, including the induction of durable serum levels of IgG reactive with mammalian dsDNA and murine type II collagen. Our findings indicate new directions for studies of this valuable model of gamma-herpesvirus pathogenesis.

Animals↗

PubMed2000

Diminished primary and secondary influenza virus-specific CD8(+) T-cell responses in CD4-depleted Ig(-/-) mice.

Optimal expansion of influenza virus nucleoprotein (D(b)NP(366))-specific CD8(+) T cells following respiratory challenge of naive Ig(-/-) microMT mice was found to require CD4(+) T-cell help, and this effect was also observed in primed animals. Absence of the CD4(+) population was consistently correlated with diminished recruitment of virus-specific CD8(+) T cells to the infected lung, delayed virus clearance, and increased morbidity. The splenic CD8(+) set generated during the recall response in Ig(-/-) mice primed at least 6 months previously showed a normal profile of gamma interferon production subsequent to short-term, in vitro stimulation with viral peptide, irrespective of a concurrent CD4(+) T-cell response. Both the magnitude and the localization profiles of virus-specific CD8(+) T cells, though perhaps not their functional characteristics, are thus modified in mice lacking CD4(+) T cells.

Animals↗

PubMed2000

Profound protection against respiratory challenge with a lethal H7N7 influenza A virus by increasing the magnitude of CD8(+) T-cell memory.

The recall of CD8(+) T-cell memory established by infecting H-2(b) mice with an H1N1 influenza A virus provided a measure of protection against an extremely virulent H7N7 virus. The numbers of CD8(+) effector and memory T cells specific for the shared, immunodominant D(b)NP(366) epitope were greatly increased subsequent to the H7N7 challenge, and though lung titers remained as high as those in naive controls for 5 days or more, the virus was cleared more rapidly. Expanding the CD8(+) memory T-cell pool (<0.5 to >10%) by sequential priming with two different influenza A viruses (H3N2-->H1N1) gave much better protection. Though the H7N7 virus initially grew to equivalent titers in the lungs of naive and double-primed mice, the replicative phase was substantially controlled within 3 days. This tertiary H7N7 challenge caused little increase in the magnitude of the CD8(+) D(b)NP(366)(+) T-cell pool, and only a portion of the memory population in the lymphoid tissue could be shown to proliferate. The great majority of the CD8(+) D(b)NP(366)(+) set that localized to the infected respiratory tract had, however, cycled at least once, though recent cell division was shown not to be a prerequisite for T-cell extravasation. The selective induction of CD8(+) T-cell memory can thus greatly limit the damage caused by a virulent influenza A virus, with the extent of protection being directly related to the number of available responders. Furthermore, a large pool of CD8(+) memory T cells may be only partially utilized to deal with a potentially lethal influenza infection.

Animals↗

PubMed2000

A previously unrecognized H-2D(b)-restricted peptide prominent in the primary influenza A virus-specific CD8(+) T-cell response is much less apparent following secondary challenge.

Respiratory challenge of H-2(b) mice with an H3N2 influenza A virus causes an acute, transient pneumonitis characterized by the massive infiltration of CD8(+) T lymphocytes. The inflammatory process monitored by quantitative analysis of lymphocyte populations recovered by bronchoalveolar lavage is greatly enhanced by prior exposure to an H1N1 virus, with the recall of cross-reactive CD8(+)-T-cell memory leading to more rapid clearance of the infection from the lungs. The predominant epitope recognized by the influenza virus-specific CD8(+) set has long been thought to be a nucleoprotein (NP(366-374)) presented by H-2D(b) (D(b)NP(366)). This continues to be true for the secondary H3N2-->H1N1 challenge but can no longer be considered the case for the primary response to either virus. Quantitative analysis based on intracellular staining for gamma interferon has shown that the polymerase 2 protein (PA(224-233)) provides a previously undetected epitope (D(b)PA(224)) that is at least as prominent as D(b)NP(366) during the first 10 days following primary exposure to either the H3N2 or H1N1 virus. The response to D(b)NP(366) seems to continue for longer, even when infectious virus can no longer be detected, but there is no obvious difference in the prevalence of memory T cells specific for D(b)NP(366) and D(b)PA(224). The generalization that the magnitude of the functional memory T-cell pool is a direct consequence of the clonal burst size during the primary response may no longer be useful. Previous CD8(+)-T-cell immunodominance heirarchies defined largely by cytotoxic T-lymphocyte assays may need to be revised.

Amino Acid Sequence↗

PubMed2000

Accessing complexity: the dynamics of virus-specific T cell responses.

The cellular dynamics of the immune system are complex and difficult to measure. Access to this problematic area has been greatly enhanced by the recent development of tetrameric complexes of MHC class I glycoprotein + peptide (tetramers) for the direct staining of freshly isolated, antigen-specific CD8(+ )T cells. Analysis to date with both naturally acquired and experimentally induced infections has established that the numbers of virus-specific CD8(+) T cells present during both the acute and memory phases of the host response are more than tenfold in excess of previously suspected values. The levels are such that the virus-specific CD8(+) set is readily detected in the human peripheral blood lymphocyte compartment, particularly during persistent infections. Experimentally, it is now possible to measure the extent of cycling for tetramer (+)CD8(+) T cells during the acute and memory phases of the host response to viruses. Dissection of the phenotypic, functional, and molecular diversity of CD8(+) T cell populations has been greatly facilitated. It is hoped it will also soon be possible to analyze CD4(+) T cell populations in this way. Though these are early days and there is an enormous amount to be done, our perceptions of the shape of virus-specific cell-mediated immunity are changing rapidly.

Animals↗

PubMed1999

Reconstitution of early lymphoid proliferation and immune function in Jak3-deficient mice by interleukin-3.

Expansion of early lymphoid progenitors requires interleukin-7 (IL-7), which functions through gamma(c)-mediated receptor activation of Jak3. Jak3 deficiency is a cause of severe combined immunodeficiency (SCID) in humans and mice. IL-3 activates many of the same signaling pathways as IL-7, such as Stat5, but achieves this effect through the activation of Jak2 rather than Jak3. We hypothesized that expansion of an IL-7-responsive precursor population through a Jak3-independent pathway using IL-3 may stimulate early lymphoid progenitors and restore lymphopoiesis in Jak3(-/-) mice. Newborn Jak3(-/-) mice that were injected with IL-3 demonstrated thymic enlargement, a 2- to 20-fold increase in thymocyte numbers, and up to a 10-fold expansion in the number of CD4(+), CD8(+), and B220(+)/IgM(+) splenic lymphocytes, consistent with an effect upon an early lymphoid progenitor population. In contrast to control mice, IL-3-treated Jak3(-/-) mice challenged with the allogeneic major histocompatibility complex (MHC) class I-bearing tumor P815 developed a specific CD8-dependent cytotoxic T lymphocyte (CTL) response. IL-3-treated mice also mounted influenza-specific CTL responses and survival was prolonged. The beneficial effects of IL-3 are proposed to be produced by stimulation of a lymphoid precursor population of IL-7Ralpha(+)/IL-3Ralpha(+) cells that we identified in wild-type bone marrow. In vitro, we show that an early IL-7R(+) lymphoid progenitor population expresses IL-3R and proliferates in response to IL-3 and that IL-3 activates Stat5 comparably to IL-7. Clinically, IL-3 may therefore be useful treatment for X-linked and Jak3-deficient SCID patients who lack bone marrow donors.

Animals↗

PubMed1999

A gamma-herpesvirus sneaks through a CD8(+) T cell response primed to a lytic-phase epitope.

To determine whether established CD8(+) T cell memory to an epitope prominent during the replicative phase of a gamma-herpesvirus infection protects against subsequent challenge, mice were primed with a recombinant vaccinia virus expressing the p56 peptide and then boosted by intranasal exposure to an influenza A virus incorporating p56 in the neuraminidase protein. Clonally expanded populations of functional, p56-specific CD8(+) T cells were present at high frequency in both the lung and the lymphoid tissue 1 month later, immediately before respiratory challenge with gammaHV-68. This prime-and-boost regime led to a massive reduction of productive gammaHV-68 infection in the respiratory tract and, initially, to much lower levels of latency in both the regional lymph nodes and the spleen. The CD8(+) T cell response to another epitope (p79) was diminished, there was less evidence of B cell activation, and the onset of the CD4(+) T cell-dependent splenomegaly was delayed. Within 3-4 weeks of the gammaHV-68 challenge, however, the extent of latent infection in the lymph nodes and spleen was equivalent, and both groups developed the prominent infectious mononucleosis-like syndrome that is characteristic of this infection. The reverse protocol (influenza then vaccinia) seemed to be slightly less effective. Even though immune CD8(+) T cells may be present at the time and site of virus challenge, establishing a high level of CD8(+) T cell memory to lytic-phase epitopes alone does not protect against the longer-term consequences of this gammaHV infection.

Animals↗

PubMed1999

In vivo proliferation of naïve and memory influenza-specific CD8(+) T cells.

The virus-specific CD8(+) T cell response has been analyzed through the development, effector, and recovery phases of primary and secondary influenza pneumonia. Apparently, most, if not all, memory T cells expressing clonotypic receptors that bind a tetrameric complex of influenza nucleoprotein (NP)(366-374) peptide+H-2D(b) (NPP) are induced to divide during the course of this localized respiratory infection. The replicative phase of the recall response ends about the time that virus can no longer be recovered from the lung, whereas some primary CD8(+)NPP(+) T cells may proliferate for a few more days. The greatly expanded population of CD8(+)NPP(+) memory T cells in the lymphoid tissue of secondarily challenged mice declines progressively in mean prevalence over the ensuing 100 days, despite the fact that at least some of these lymphocytes continue to cycle. The recall of cell-mediated immunity thus is characterized by massive proliferation of the antigen-specific CD8(+) set, whereas the extent of lymphocyte turnover in the absence of cognate peptide is variable, at a low level, and can be influenced by intercurrent infection.

Animals↗

PubMed1999

CD4(+) T cell-mediated control of a gamma-herpesvirus in B cell-deficient mice is mediated by IFN-gamma.

The lack of B cells and antibody does not prevent mice from dealing effectively with a pathogenic gamma-herpesvirus. Both CD4(+) and CD8(+) T cells contribute to the control of virus replication in the respiratory tract, with the depletion of either lymphocyte subset leading to increased titers in the lung. However, the further neutralization of IFN-gamma diminishes the effectiveness of the CD4(+) T cell response and causes substantially increased mortality. Experiments with bone marrow radiation chimeras indicate that the immune CD4(+) effectors operate optimally when there is the potential for direct interaction with virus-infected targets expressing MHC class II glycoproteins, suggesting that the IFN-gamma produced by these lymphocytes is functioning at short range. The numbers of latently infected cells in the spleens of carrier mice are also significantly increased by the concurrent depletion of both the CD4(+) population and IFN-gamma. These experiments raise the possibility that the defective control of intercurrent gamma-herpesvirus infections in patients with AIDS not only is due solely to the absence of helper T cells but also reflects the loss of an important set of CD4(+) effectors.

Animals↗

PubMed1999

Virus-specific immunity after gene therapy in a murine model of severe combined immunodeficiency.

Human severe combined immunodeficiency (SCID) can be caused by defects in Janus kinase 3 (JAK3)-dependent cytokine signaling pathways. As a result, patients are at high risk of life-threatening infection. A JAK3 -/- SCID mouse model for the human disease has been used to test whether transplant with retrovirally transduced bone marrow (BM) cells (JAK3 BMT) could restore immunity to an influenza A virus. The immune responses also were compared directly with those for mice transplanted with wild-type BM (+/+ BMT). After infection, approximately 90% of the JAK3 BMT or +/+ BMT mice survived, whereas all of the JAK3 -/- mice died within 29 days. Normal levels of influenza-specific IgG were present in plasma from JAK3 BMT mice at 14 days after respiratory challenge, indicating restoration of B cell function. Influenza-specific CD4(+) and CD8(+) T cells were detected in the spleen and lymph nodes, and virus-specific CD8(+) effectors localized to the lungs of the JAK3 BMT mice. The kinetics of the specific host response correlated with complete clearance of the virus within 2 weeks of the initial exposure. By contrast, the JAK3 -/- mice did not show any evidence of viral immunity and were unable to control this viral pneumonia. Retroviral-mediated JAK3 gene transfer thus restores diverse aspects of cellular and humoral immunity and has obvious potential for human autologous BMT.

Animals↗

PubMed1999

Changing patterns of dominance in the CD8+ T cell response during acute and persistent murine gamma-herpesvirus infection.

The murine gamma-herpesvirus MHV-68 causes an acute, transient pneumonitis, followed by an infectious mononucleosis (IM)-like illness with splenomegaly, widespread latent infection of B lymphocytes and an expansion of Vbeta4+ CD8+ T cells. CD8+ T cells specific for an H-2Db-restricted epitope were prominent during the acute respiratory infection, but their prevalence declined rapidly during the mononucleosis. In contrast, CD8+ T cells specific for an H-2Kb-restricted epitope, apparently expressed by virus-infected B lymphocytes, were most numerous during the mononucleosis illness and were maintained at relatively high frequencies thereafter. The prevalence of all peptide-specific CD8+ T cells decreased during the expansion of the Vbeta4+ CD8+ population, which did not recognize any peptide epitopes identified and was apparent also in an MHC class I-deficient environment. The CD8+ T cell population recognizing productively infected epithelial cells thus differed substantially from that responding during the IM illness.

Acute Disease↗

PubMed1999

Feline penile erection induced by transurethral administration of sodium nitroprusside.

Nitric oxide (NO) is an important mediator in the relaxation of cavernosal smooth muscle. The aim of this study was to investigate the in vivo feline erectile response after transurethral administration of sodium nitroprusside (SNP), a NO donor drug. Erectile responses after administration of transurethral SNP were compared with those elicited by an intracavernosal control triple-drug combination (1.65 mg papaverine, 25 microg phentolamine, and 0.5 microg prostaglandin E1). SNP was administered via a 20-gauge Jelco intravenous catheter in a volume of 200 microl and changes in intracavernosal pressure, penile length, and systemic blood pressure were monitored. The control triple-drug combination was administered via a 30-gauge needle at the end of each experiment to serve as a control reference. Transurethral administration of SNP (1-4 mg) induced penile erection in a dose-dependent manner with minimal changes in systemic blood pressure. The maximum increase in intracavernosal pressure and penile length after transurethral administration of SNP (4 mg) was significantly less than after the intracavernosal injection of the control triple-drug combination (P<0.01). These data suggest that transurethral administration of SNP can induce an erectile response in cats with minimal side effects.

Alprostadil↗

PubMed1999

Burnet Oration: living in the Burnet lineage.

Scientific discoveries are not made in isolation. Innovation depends on resources, both intellectual and physical. A primary requirement is the development and maintenance of appropriate institutions. Such structures do not emerge by chance, but arise from opportunity, political will and the continued efforts and commitment of many people over long periods. Suitable buildings, laboratories and state-of-the-art equipment are obviously necessary, but hardware alone is of little value in the absence of a vibrant research culture. The key characteristics of the latter are intellectual foment, open debate and a body of wisdom and knowledge about the particular subject area. Rolf Zinkernagel and 1 played a part in triggering a paradigm shift in the understanding of T cell recognition, a contribution recognized by the 1996 Nobel Prize for Physiology or Medicine. In our Nobel lectures, we both discussed briefly why it was that the John Curtin School of Medical Research (JCSMR) of 1973-75 provided a milieu that facilitated the emergence of the underlying experiments and ideas. My intention here is to discuss in more detail the scientific lineages that put this physical and intellectual environment in place, focusing particularly on the influence of Sir Frank Macfarlane (Sir Mac) Burnet as we celebrate his centenary year.

Academies and Institutes↗

PubMed1999

Immunological control of a murine gammaherpesvirus independent of CD8+ T cells.

Adult thymectomized C57 BL/6J mice were depleted of T cell subsets by MAb treatment either prior to, or after, respiratory challenge with murine gammaherpesvirus-68. Protection against acute infection was maintained when either the CD4+ or the CD8+ T cell population was greatly diminished, whereas the concurrent removal of both T cell subsets proved invariably fatal. The same depletions had little effect on mice with established infection. The results indicate firstly that both CD4+ and CD8+ T cells play a significant part in dealing with the acute infection, and secondly that virus-specific antibody contributes to controlling persistent infection with this gammaherpesvirus.

Animals↗

PubMed1999

Requirement for CD40 ligand, CD4(+) T cells, and B cells in an infectious mononucleosis-like syndrome.

Respiratory challenge with the murine gammaherpesvirus 68 (gammaHV-68) results in productive infection of the lung, the establishment of latency in B lymphocytes and other cell types, transient splenomegaly, and prolonged clonal expansion of activated CD8(+) CD62L(lo) T cells, particularly a Vbeta4(+) CD8(+) population that is found in mice with different major histocompatibility complex (MHC) haplotypes. Aspects of the CD8(+)-T-cell response are substantially modified in mice that lack B cells, CD4(+) T cells, or the CD40 ligand (CD40L). The B-cell-deficient mice show no increase in Vbeta4(+) CD8(+) T cells. Similar abrogation of the Vbeta4(+) CD8(+) response is seen following antibody-mediated depletion of the CD4(+) subset, through the numbers of CD8(+) CD62L(lo) cells are still significantly elevated. Virus-specific CD4(+)-T-cell frequencies are minimal in the CD40L(-/-) mice, and the Vbeta4(+) CD8(+) population remains unexpanded. Apparently B-cell-CD4(+)-T-cell interactions play a part in the gammaHV-68 induction of both splenomegaly and non-MHC-restricted Vbeta4(+) CD8(+)-T-cell expansion.

Animals↗