Biomedical subjects

Alan Huett

Publications and source records attributed to Alan Huett.

5 recordsLinked to original sources

PubMed2004

Impaired immunity to intestinal bacterial infection in stromelysin-1 (matrix metalloproteinase-3)-deficient mice.

Infection of mice with the intestinal bacterial pathogen Citrobacter rodentium results in colonic mucosal hyperplasia and a local Th1 inflammatory response similar to that seen in mouse models of inflammatory bowel disease. Matrix metalloproteinases (MMPs) have been shown to mediate matrix remodeling and cell migration during tissue injury and repair in the intestine. We have previously shown enhanced pathology in infected TNFRp55-/-, IL-12p40-/-, and IFN-gamma-/- mice, and here we show that this is associated with an increase in stromelysin-1 (MMP3) transcripts in colonic tissues. We have therefore investigated the role of MMP3 in colonic mucosal hyperplasia and the local Th1 responses using MMP3-/- mice. In MMP3-/- mice, similar mucosal thickening was observed after infection as in wild-type (WT) mice. Colonic tissues from MMP3-/- mice showed a compensatory increase in the expression of other MMP transcripts, such as MMP7 and MMP12. However, MMP3-/- mice showed delayed clearance of bacteria and delayed appearance of CD4+ T lymphocytes into intestinal lamina propria. CSFE-labeled mesenteric lymph node CD4+ T lymphocytes from infected WT mice migrated in fewer numbers into the mesenteric lymph nodes and colon of MMP3-/- mice than into those of WT mice. These studies show that mucosal remodeling can occur in the absence of MMP3, but that MMP3 plays a role in the migration of CD4+ T lymphocytes to the intestinal mucosa.

Animals↗

PubMed2004

Organ specificity, colonization and clearance dynamics in vivo following oral challenges with the murine pathogen Citrobacter rodentium.

Citrobacter rodentium belongs to a family of human and animal enteric pathogens that includes the clinically significant enterohaemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC). These pathogens use attaching and effacing (A/E) lesions to colonize the host gastrointestinal tract. In this study we have used bioluminescence imaging (BLI) to investigate the organ specificity, dynamics of colonization and clearance of mice by C. rodentium in situ and in real time. The bioluminescent C. rodentium derivative, strain ICC180, expresses the luxCDABE operon from the entemopathogenic nematode symbiont Photorhabdus luminescens and light levels accurately reflect bacterial numbers both in vitro and in vivo. We have demonstrated that primary colonization of the mouse by C. rodentium takes place within the caecum, specifically within the specialized patch of lymphoid tissue known as the caecal patch. Following colonization of the caecum C. rodentium established a colonic infection. Clearance of C. rodentium ICC180 parallels the colonization dynamics, i.e. the caecum was first to be cleared followed by the colon. A bioluminescent eae (encoding the outer membrane adhesin intimin) C. rodentium mutant failed to establish long-term colonization, although low levels of bacteria could be recovered for up to 3 days post challenge from the caecum.

Adhesins, Bacterial↗

PubMed2004

Mucosal vaccination against serogroup B meningococci: induction of bactericidal antibodies and cellular immunity following intranasal immunization with NadA of Neisseria meningitidis and mutants of Escherichia coli heat-labile enterotoxin.

Conjugated polysaccharide vaccines protect against serogroup C meningococci. However, this approach cannot be applied to serogroup B, which is still a major cause of meningitis. We evaluated the immunogenicity of three surface-exposed proteins from serogroup B Neisseria meningitidis (App, NhhA, and NadA) identified during whole-genome sequencing. Mice were immunized intranasally with individual proteins in the presence of wild-type Escherichia coli heat-labile enterotoxin (LTwt), LTR72, a partially inactivated mutant, or LTK63, a completely nontoxic mutant, as the adjuvant. Each of the meningococcal proteins induced significant cellular responses; NhhA and NadA induced strong antibody responses, but only NadA induced bactericidal antibody when administered intranasally with mucosal adjuvants. In addition, immunoglobulin A and bactericidal antibodies were detected in the respiratory tract following intranasal delivery of NadA. Analysis of antigen-specific cytokine production by T cells from immunized mice revealed that intranasal immunization with NadA alone failed to generate detectable cellular immune responses. In contrast, LTK63, LTR72, and LTwt significantly augmented NadA-specific gamma interferon, interleukin-4 (IL-4), IL-5, and IL-10 production by spleen and lymph node cells, suggesting that both Th1 and Th2 cells were induced in vivo. The strongest cellular responses and highest bactericidal antibody titers were generated with LTR72 as the adjuvant. These findings demonstrate that the quality and magnitude of the immune responses generated by mucosal vaccines are influenced by the antigen as well as the adjuvant and suggest that nasal delivery of NadA with mucosal adjuvants has considerable potential in the development of a mucosal vaccine against serogroup B meningococci.

Animals↗

PubMed2002

Host/pathogen interactions at mucosal surfaces: immune consequences.

The mucosal immune system has evolved to protect the host against the establishment of infections at or through the mucosal surfaces of the body. Protective immunity must be activated to specific pathogenic agents or their products but inappropriate immune responses to food/environmental antigens must be avoided. Thus, the mucosal immune system is under tight regulation. Pathogenic bacteria and their products can be exploited as specific probes of mucosal immune responses. Bacterial enterotoxins such as cholera toxin are potent mucosal immunogens and adjuvants that activate both mucosal and systemic immune responses. Infection models involving microorganisms such as Citrobacter rodentium can also be used to investigate the consequences of mucosal colonisation that lead to immune disfunction.

Animals↗

PubMed2002

Vaccines against human enteric bacterial pathogens.

The development of vaccines against enteric bacterial pathogens presents a challenge because of the large number of pathogens capable of causing disease and the requirement to induce immunity that is effective in the gut. A new generation of enteric vaccines based either on live or non-living antigens delivered orally or by injection are reaching the clinic in the early phases of evaluation. However, considerable technical barriers have to be overcome before these vaccines reach the general population.

Administration, Oral↗