Intradermal Administration of the Type II Heat-Labile Enterotoxins LT-IIb and LT-IIc of Enterotoxigenic Escherichia coli Enhances Humoral and CD8+ T Cell Immunity to a Co-Administered Antigen

Abstract

Vaccinations are extremely effective at combating infectious diseases. Many conserved antigen (Ag) targets, however, are poorly immunogenic. Protein subunit vaccines frequently elicit only humoral immune responses and fail to confer protection against serious intracellular pathogens. These barriers to vaccine development are often overcome by the use of appropriate adjuvants. Heat-labile enterotoxins (HLT) produced by enterotoxigenic strains of Escherichia coli are potent adjuvants when administered by mucosal or systemic routes. The efficacy of the type II HLT, however, has not been well-defined when administered by the intradermal (ID) route. Using a murine ID immunization model, the adjuvant properties of LT-IIb and LT-IIc, two type II HLTs, were compared with those of LT-I, a prototypical type I HLT. While all three HLT adjuvants enhanced Ag-specific humoral responses to similar levels, LT-IIb and LT-IIc, in contrast to LT-I, induced a more vigorous Ag-specific CD8+ T cell response and proffered faster clearance of Listeria monocytogenes in a challenge model. Additionally, LT-IIb and LT-IIc induced distinct differences in the profiles of the Ag-specific CD8+ T cell responses. While LT-IIc stimulated a robust and rapid primary CD8+ T cell response, LT-IIb exhibited slower CD8+ T cell expansion and contraction kinetics with the formation of higher percentages of effector memory cells. In comparison to LT-I and LT-IIc, LT-IIb evoked better long-term protection after immunization. Furthermore, LT-IIb and LT-IIc enhanced the total number of dendritic cells (DC) in the draining lymph node (DLN) and expression of costimulatory molecules CD80, CD86, and CD40 on DCs. In contrast to LT-I, LT-IIb and LT-IIc induced less edema, cellular infiltrates, and general inflammation at the site of ID injection. Thus, LT-IIb and LT-IIc are attractive comprehensive ID adjuvants with unique characteristic that enhance humoral and cellular immunity to a co-administered protein Ag.

Near-Infrared 1064 nm Laser Modulates Migratory Dendritic Cells To Augment the Immune Response to Intradermal Influenza Vaccine

“…A broad range of transdermal and intradermal vaccination technologies (51, 52) would benefit from the inclusion of an adjuvant, but use of conventional chemical or biological adjuvants in the confines of the skin results in unacceptable inflammatory responses (53, 54). Consequently only a small number of proposed adjuvants are ideally suited for use in the skin (55, 56). In the present study, both of the representative clinical adjuvants, Alum and AddaVax, (an oil-in-water emulsion adjuvant with a formulation similar to MF59®), induced significant upregulation of influenza-specific IgE in the context of intradermal influenza vaccination (fig 1f), which may lead to an adverse response induced by vaccination.…”

Comparative Adjuvant Effects of Type II Heat-Labile Enterotoxins in Combination with Two Different Candidate Ricin Toxin Vaccine Antigens

“…Edema was determined by taking two orthogonal measurements (M 1 and M 2 , M 1 Ͼ M 2 ) of the edema diameter and then multiplied by an estimated depth, which was arbitrarily set at M 2 because of the difficulty in accurately measuring the depth of swelling, especially at early time points. Hence, edema volume was calculated as M 1 ϫ M 2 ϫ M 2 , and values were reported as cubic millimeters as done previously (9).…”

“…The type II enterotoxins, on the other hand, are less well characterized and more diverse than CT or LT (7,8). The beststudied type II HLTs are LT-IIa, LT-IIb, and LT-IIc, each of which has been shown to enhance antigen-specific immune responses when coadministered with a model antigen like ovalbumin (OVA) (9). Adjuvant activities of the type I and II HLTs are due to a combination of the A subunit's ability to stimulate intracellular cyclic AMP (cAMP) levels through ADP-ribosylation of Gs␣ regulatory proteins and the pentameric B subunit's tropism for specific cell types.…”

“…Each member of the type II HLTs stimulates a different pattern of cytokines and different degrees of lymphocyte activation, resulting in potentially differential adjuvant activities (7). Four of the type II HLTs, LT-IIa, LT-IIb, and LT-IIc and a genetically detoxified mutant of LT-IIb known as LT-IIb T13I , have been tested as adjuvants in conjunction with a variety of antigens, including OVA (7,9,10), AgI/II from Streptococcus mutans (10), and ESAT-6 from Mycobacterium tuberculosis antigen (11). However, a systematic side-by-side comparison among the HLTs has never been done.…”

A pilot clinical trial of a near‐infrared laser vaccine adjuvant: safety, tolerability, and cutaneous immune cell trafficking

“…Few substances have proven both safe from reactogenicity and effective in amplifying immune effects; the U.S. Food and Drug Administration (FDA) has approved only 6 adjuvants over 80 yr, and the European Medicines Agency has approved only 7 adjuvants. Fewer still are ideally suited to use in the skin (2,3), which is richly supplied with antigenpresenting cells and pain nerves (4)(5)(6). Development of new intradermal adjuvants is in keeping with the National Institute of Allergy and Infectious Diseases mission to develop new and improved vaccines against infectious diseases (7).…”