Pulmonary gene expression profiling of inhaled ricin

Aerosol exposure to ricin causes irreversible pathological changes of the respiratory tract resulting in epithelial necrosis, pulmonary edema and ultimately death. The pulmonary genomic profile of BALB/c mice inhalationally exposed to a lethal dose of ricin was examined using cDNA arrays. The expression profile of 1178 mRNA species was determined for ricin-exposed lung tissue, in which 34 genes had statistically significant changes in gene expression. Transcripts identified by the assay included those that facilitate tissue healing (early growth response gene (egr)-1), regulate inflammation (interleukin (IL)-6, tristetraproline (ttp)), cell growth (c-myc, cytokine-inducible SH2-containing protein (cish)- 3), apoptosis (T-cell death associated protein (tdag)51, pim-1) and DNA repair (ephrin type A receptor 2 (ephA2)). Manipulation of these gene products may provide a means of limiting the severe lung damage occurring at the cellular level. Transcriptional activation of egr-1, cish-3, c-myc and thrombospondin (tsp)-1 was already apparent when pathological and physiological changes were observed in the lungs at 12 h postexposure. These genes may well serve as markers for ricin-induced pulmonary toxicity. Ongoing studies are evaluating this aspect of the array data and the potential of several genes for clinical intervention.

In vitro correlate of immunity in a rabbit model of inhalational anthrax

A serological correlate of vaccine-induced immunity was identified in the rabbit model of inhalational anthrax. Animals were inoculated intramuscularly at 0 and 4 weeks with varying doses of Anthrax Vaccine Adsorbed (AVA) ranging from a human dose to a 1:256 dilution in phosphate-buffered saline (PBS). At 6 and 10 weeks, both the quantitative anti-protective antigen (PA) IgG ELISA and the toxin-neutralizing antibody (TNA) assays were used to measure antibody levels to PA. Rabbits were aerosol-challenged at 10 weeks with a lethal dose (84-133 LD(50)) of Bacillus anthracis spores. All the rabbits that received the undiluted and 1:4 dilution of vaccine survived, whereas those receiving the higher dilutions of vaccine (1:16, 1:64 and 1:256) had deaths in their groups. Results showed that antibody levels to PA at both 6 and 10 weeks were significant (P<0.0001) predictors of survival.

Chromosomal translocations deregulating c-myc are associated with normal immune responses

Plasmacytomas induced in BALB/c mice by pristane consistently evidence chromosomal translocations involving the c-myc gene and one of the Ig loci. This observation has lead to the suggestion that c-myc deregulation is a critical event in the generation of such tumors. However, it is not clear whether c-myc translocation is related to pristane treatment or occurs in normal lymphocyte populations nor whether such translocations occur normally, and at similar frequencies, in strains genetically resistant to plasmacytoma development, such as DBA/2. In order to address these questions, a Long Distance PCR assay with single copy sensitivity was employed to assess the frequency of c-myc/IgA translocations in normal and immunized mice of both plasmacytoma resistant and susceptible lineages in the absence of pristane treatment. Our data demonstrate that spontaneous translocations occur in normal DBA/2 and BALB/c mice with no significant differences in frequency. A 3-5-fold increase in translocation frequency was observed in mice immunized with cholera toxin, a strong stimulator of IgA responses. We conclude that c-myc deregulation by chromosomal translocation is associated with normal physiological processes of B-cell differentiation and, as such, can not be the determining factor leading to malignancy.

Venezuelan equine encephalitis virus vaccines induce mucosal IgA responses and protection from airborne infection in BALB/c, but not C3H/HeN mice

Immunization with either a live-attenuated (TC-83) or formalin-inactivated (C-84) vaccine for Venezuelan equine encephalitis (VEE) virus protected BALB/c mice from lethal VEE infection acquired subcutaneously or by aerosol. While vaccinated C3H/HeN mice were also protected from parenteral infection, neither vaccine protected these mice from an aerosol infection. The apparent vaccine failures in C3H/HeN mice could not be attributed to deficiencies in virus-neutralizing antibodies in serum, as these responses were typically of equal or higher titer than those observed in protected BALB/c mice before challenge. IgG subclass analysis offered no facile explanation: profiles of IgG2 alpha dominance were observed in C3H/HeN mice given either vaccine and in BALB/c mice given the live-attenuated vaccine, whereas BALB/c antibody responses shifted toward IgGl dominance after immunization with the killed C-84 vaccine. Data from immunized congenic mice showed that the H-2 genes from the C3H/He mice were not singularly responsible for the inability of these mice to resist aerosol infection with VEE virus. VEE virus-specific IgA responses were detected more frequently in respiratory and vaginal secretions obtained from the protected BALB/c mice.

Liposomes and conjugate vaccines for antigen delivery and induction of mucosal immune responses

In this brief review, emphasis was placed on the effectiveness of liposomes as carriers/vehicles of soluble antigens and as adjuvants for use in oral vaccine development. Evidence was provided that oral administration of antigen in liposomes resulted in a mucosal response which was higher than that obtained when the oral vaccine consisted of antigen alone. Specific mucosal responses were enhanced by incorporating lipophilic MDP into the antigen/liposome vaccines. Antigens shown to be effective in inducing a protective mucosal response when given in an oral liposome vaccine were anti-idiotypic antibodies, purified S. mutans GTF, CHO and Ag I/II. Evidence is also provided that CTB may be an effective oral adjuvant when coupled to proteins or peptides by either chemical or genetic methods. Further studies, however, will be required to characterize the effectiveness and safety of CTB in conjugate vaccines for inducing specific mucosal responses and to develop practical means to prepare oral liposome vaccines for use in humans.