Biomedical subjects

Alexandra J Corbett

Publications and source records attributed to Alexandra J Corbett.

9 recordsLinked to original sources

PubMed2026

Allelic variation alters expression and antigen presentation of MR1 allomorphs.

The major histocompatibility complex (MHC) class I-related protein 1 (MR1) presents vitamin B-derived metabolites to mucosal-associated invariant T (MAIT) and other T cells. There is limited polymorphism of MR1, the functional impact of which is not understood. We examined the impact of allelic variation of MR1 on the expression, structure and function of the known MR1 allomorphs. The expression and function of MR1∗02, MR1∗03, and MR1∗06 were similar to the canonical MR1∗01. Crystal structures of four MR1 allomorphs show that their polymorphisms do not impact the three-dimensional fold of MR1. Despite the binding of 5-OP-RU to MR1∗05 and its cell surface upregulation, this allomorph was severely impaired in its ability to activate primary MAIT cells. This phenotype was controlled by two (His90Gln and Glu52Gly) of its three polymorphisms, which led to the loss of structurally stabilizing interactions. When cells expressing the MR1 allomorphs were infected with herpes simplex virus type 1 (HSV-1), the nascent expression of all allomorphs was severely impaired, but surface expression of MR1∗04:01 and MR1∗04:02 was relatively less impacted. Hence, MR1 allelic variation alters the expression and function of the MR1∗04 and MR1∗05 allomorphs, with implications for MAIT cell and diverse MR1-reactive T cell immunity.

Humans↗

PubMed2006

The interplay between host and viral factors in shaping the outcome of cytomegalovirus infection.

Cytomegalovirus (CMV) remains a major human pathogen causing significant morbidity and mortality in immunosuppressed or immunoimmature individuals. Although significant advances have been made in dissecting out certain features of the host response to human CMV (HCMV) infection, the strict species specificity of CMVs means that most aspects of antiviral immunity are best assessed in animal models. The mouse model of murine CMV (MCMV) infection is an important tool for analysis of in vivo features of host-virus interactions and responses to antiviral drugs that are difficult to assess in humans. Important studies of the contribution of host resistance genes to infection outcome, interplays between innate and adaptive host immune responses, the contribution of virus immune evasion genes and genetic variation in these genes to the establishment of persistence and in vivo studies of resistance to antiviral drugs have benefited from the well-developed MCMV model. In this review, we discuss recent advances in the immunobiology of host-CMV interactions that provide intriguing insights into the complex interplay between host and virus that ultimately facilitates viral persistence. We also discuss recent studies of genetic responses to antiviral therapy, particularly changes in DNA polymerase and protein kinase genes of MCMV and HCMV.

Antiviral Agents↗

PubMed2006

Rapid specific amplification of rat antibody cDNA from nine hybridomas in the presence of myeloma light chains.

Most monoclonal antibodies to mouse antigens have been derived from rat spleen-mouse myeloma fusions. Many resultant hybridomas express one of several myeloma kappa chain transcripts, even though the parent myeloma may have been ascribed as not expressing light chain protein. Previous reports have only differentiated against one of these mouse light chains. We have found at least three different myeloma kappa transcripts in the panel of nine hybridomas that were derived from four different myeloma parents. We have designed an amplification strategy that differentiates the rearranged rat kappa chain from all mouse light chains. Moreover, this method is expedient as it requires minimal downstream manipulation.

Amino Acid Sequence↗

PubMed2006

Functional comparison of mouse CIRE/mouse DC-SIGN and human DC-SIGN.

CIRE/mDC-SIGN is a C-type lectin we originally identified as a molecule differentially expressed by mouse dendritic cell (DC) populations. Immunostaining with a CIRE/mDC-SIGN-specific mAb revealed that CIRE/mDC-SIGN is indeed on the surface of some CD4+, CD4- 8- DCs and plasmacytoid pre-DCs, but not on CD8+ DCs. It has been proposed that CIRE/mDC-SIGN is the functional orthologue of human DC-SIGN (hDC-SIGN), a molecule that both enhances T cell responses and facilitates antigen uptake. We assessed if CIRE/mDC-SIGN and hDC-SIGN exhibit functional similarities. CIRE/mDC-SIGN is down-regulated upon activation, but unlike hDC-SIGN, incubation with IL-4 and IL-13 did not enhance CIRE/mDC-SIGN expression, indicating differences in gene regulation. Like hDC-SIGN, CIRE/mDC-SIGN bound mannosylated residues. However, we could detect no role for CIRE/mDC-SIGN in T cell-DC interactions and the protein did not bind to pathogens known to interact with hDC-SIGN, including Leishmania mexicana, cytomegalovirus, HIV and lentiviral particles bearing the Ebolavirus glycoprotein. The binding of CIRE/mDC-SIGN to hDC-SIGN ligands was not rescued when CIRE/mDC-SIGN was engineered to express the stalk region of hDC-SIGN. We conclude that there are significant differences in the fine specificity of the C-type lectin domains of hDC-SIGN and CIRE/mDC-SIGN and that these two molecules may not be functional orthologues.

Amino Acid Sequence↗

PubMed2005

Targeting lymphocyte Peyer's patch adhesion molecule-1: a relay approach to gut immunization.

Targeting vaccines to dendritic cells (DCs) can enhance responses to weak vaccine antigens. Although there are molecules that are relatively specific for the various DC subsets, there are none that are both region-specific and DC-specific. This has provided some limitation to targeting regional DC populations. We proposed that these limits could be overcome by targeting antigens not to the DC subsets directly but to cells that persistently seek out and closely interact with DCs, namely lymphocytes. To investigate this hypothesis, we targeted antigens to a unique population of gut-homing lymphocytes and then looked at the induction of immune responses at this site. Using an anti-LPAM-1 (Lymphocyte Peyer's patch adhesion molecule-1; alpha(4)beta(7) integrin) monoclonal antibody (mAb) as a model antigen, we found that targeting gut-homing lymphocytes could significantly elevate the gut mucosal IgA response. Moreover, such a strategy greatly elevated the systemic IgG as well as IgA response. We found that LPAM-1-targeting enhanced the localization of antigen to both the systemic and mucosal lymphoid compartments where both IgA and IgG responses were induced. We also found that any parenteral route of delivery sufficed. Overall, targeting unique populations of lymphocytes may provide a strategy for ferrying antigen to sites that such lymphocytes home to.

Animals↗

PubMed2005

Antigen delivery via two molecules on the CD8- dendritic cell subset induces humoral immunity in the absence of conventional "danger".

Targeting antigen to dendritic cells (DC) in vivo might be an effective method of modulating immune responses. Given the functional specializations among DC subsets, we investigated how targeting different receptors on different DC subsets may influence antibody (Ab) production. We show here that targeting FIRE (F4/80-like receptor) or CIRE (C-type lectin receptor), two molecules expressed on the surface of immature CD8- DC in the mouse, increases Ab production 100-1000-fold over a non-targeted control. This response was equivalent to that achieved with CpG adjuvant. In contrast, targeting CD205, which is primarily expressed on CD8+ DC, did not elicit an Ab response unless an adjuvant was added. Strong Ab responses in FcRgamma-/- mice, and with the use of F(ab')2 fragments, confirmed that FIRE and CIRE targeting was due to specific rather than FcR or complement binding. Our findings may reflect differences in the ability of CD8+ and CD8- DC subsets to stimulate immune responses in vivo. Although the consensus view is that Ag presentation on DC in their steady state leads to tolerance, the Ab enhancement from FIRE and CIRE targeting in the apparent absence of any "danger" or inflammatory signal would suggest that targeting certain DC molecules can supplant the need for external adjuvants for eliciting immune responses.

Animals↗

PubMed2004

Bypassing luminal barriers, delivery to a gut addressin by parenteral targeting elicits local IgA responses.

Induction of mucosal immunity, particularly to subunit vaccines, has been problematic. The primary hurdle to successful mucosal vaccination is the effective delivery of vaccine antigen to the mucosal associated lymphoid tissue. Physical and chemical barriers restrict antigen access and, moreover, immune responses induced in the mucosa can be biased towards tolerance or non-reactivity. We proposed that these difficulties could be circumvented by targeting antigen to the gastrointestinal associated lymphoid tissue via systemic (parenteral) rather than alimentary routes, using antibodies specific for the mucosal addressin cellular adhesion molecule-1 (MAdCAM). After intravenous or intramuscular injection of such rat antibodies in mice, we found a greatly enhanced (up to 3 logs) anti-rat antibody response. MAdCAM targeting induces a rapid IgA antibody response in the gut and vastly improves the systemic antibody response. Targeting also enhanced T cell proliferation and cytokine responses. Parenteral targeting of mucosal addressins may represent a generic technique for bypassing mucosal barriers and eliminating the need for adjuvants in the induction of proximal and systemic immunity.

Animals↗

PubMed2002

Anti-CD45RB antibody deters xenograft rejection by modulating T cell priming and homing.

Pancreatic islet xenotransplantation has been advocated as a way of overcoming the shortage of human donor tissue for the treatment of type 1 diabetes. However, the potent immune response against xenografts is a major barrier to their use. We show that a short course of the anti-CD45RB antibody, MB23G2, prolongs survival of fetal pig pancreas grafts in mice. To investigate this effect further we used an i.p. xenograft model in which both donor pig cells and host inflammatory cells can be expediently recovered and analyzed. Graft prolongation was associated with reduced T cell and macrophage infiltration, and reduced production of both T(h)1 and T(h)2 cytokines at the graft site. Graft survival was further increased and T cell infiltration further reduced by combining anti-CD45RB antibody with co-stimulation blockade. The primary effect of anti-CD45RB antibody may be on CD4 T cells, in keeping with the marked reduction in T cell cytokine production in both spleen and graft sites. This concurs with previous studies in allogeneic models that indicate that this antibody perturbs T cell responses by modifying signaling via the TCR. In addition, anti-CD45RB treatment led to reduced expression of LFA-1 and CD62 ligand (CD62L) on CD4 T cells, independent of antigenic challenge. LFA-1 may enhance co-stimulation, and both LFA-1 and CD62L are involved in T cell trafficking. Their reduced expression provides an explanation why the T cell pool is reduced in lymph nodes. We conclude that modulation of inflammation against xenografts by anti-CD45RB antibody is due to effects on both T cell priming and trafficking.

Abatacept↗

PubMed2002

A single buffer that universally serves both restriction digestion and loading.

Restriction digestion is routinely performed in a buffer compatible with the restriction enzyme used. To load the samples on agarose gels for electrophoresis it is then necessary to add a loading buffer. A 10X loading buffer is often used, and consists of a dye to track the electrophoresis and a dense solution so that the digestion mixture sinks into the well. We describe a new buffer, which acts as a universal digestion buffer as well as a loading buffer. This avoids double handling of samples, which wastes both time and consumables. Importantly, the efficiency of digestion was found not to be significantly decreased in this new buffer.

Buffers↗