Effect of antigen form on local immunoglobulin A memory response of intestinal secretions to Shigella flexneri

Abstract

An enhanced memory response, as shown by increased titers of specific immunoglobulin A (IgA), was seen in intestinal secretions from isolated Thiry-Vella loops in rabbits primed orally with live, locally invasive Shigella sp. X16 and challenged 60 days later with a single oral dose of the same antigen. Heat-killed shigella preparations, when used as either the priming or challenge antigen, did not elicit such a memory response in this system. In the present study, the role of antigen form and dosage in eliciting the enhanced local IgA response was investigated. A noninvasive strain, Shigellaflexneyi 2457-0, was capable of significantly enhancing the mucosal IgA memory response, whereas heat-killed Shigella sp. X16 was unable to augment the local IgA response, even when the priming dose was increased 100-fold. A proposed mucosal adjuvant, DEAE-dextran, given orally with live Shigella sp. X16, did not enhance the local IgA response. Viable, noninvasive shigellae were effective priming agents in enhancing the local IgA memory response. The poor mucosal response to heat-killed shigella preparations is thought to be related to an ineffective delivery of nonviable bacterial antigens into gut-associated lymphoid tissues. The ability of the live, noninvasive strain to elicit a vigorous local IgA memory response when given orally to rabbits was consistent with previous findings that live preparations elicit the best mucosal IgA response.

Oral immunization with Toxoplasma gondii antigens in association with cholera toxin induces enhanced protective and cell-mediated immunity in C57BL/6 mice

“…We have recently reported that CT significantly enhances the anti-T. gondii secretory IgA response following oral immunization of mice with TSo and CT (2). This enhancement of the intestinal secretory IgA response is of great interest because IgA antibodies have been considered, in some cases, to be protective against oral infection with parasites, bacteria, or viruses (10,24,28). The protective immune response following a primary T. gondii infection is complex and probably involves humoral as well as cellular mechanisms.…”

Antibody responses to Toxoplasma gondii in sera, intestinal secretions, and milk from orally infected mice and characterization of target antigens

“…Previous reports have demonstrated intestinal IgA antibodies (1, 7, 16, 17, 26, 28) and milk IgA antibodies (4, 5, 15, 21, 33) following bacterial, viral, or parasitic infection. In some cases, the presence of pathogen-specific IgA antibodies has been associated with protection against infection by the pathogen (2,5,14,17,26,28). McLeod and Mack (23) first demonstrated the production of intestinal IgA antibodies to T. gondii and later suggested that IgA may play a protective role against toxoplasmosis (22).…”

Immunoprotective oral whole cell vaccine for enterotoxigenic Escherichia coli diarrhea prepared by in situ destruction of chromosomal and plasmid DNA with colicin E2

“…Various strategies have been employed in attempts to develop vaccines against bacterial enteropathogens such as Shigella, Salmonella, V. cholerae and ETEC, and various degrees of success have been achieved. The approaches differ primarily in the form of antigen chosen for oral administration; i.e., living attenuated strains [5,[9][10][11], whole bacteria killed by either heat and/or chemicals [28,29], purified toxoids to provoke anti-toxin immunity [7,13,14] and purified fimbrial CFAs to provoke immunity against intestinal colonization [12,[16][17]. Candidate vaccines have been designed for each pathogen mainly on the basis of recognized mechanisms of pathogenesis, antigenicity of killed cell preparations or purified virulence factors, and in consideration of the risk of minor but undesirable responses to living attenuated strains.…”