Identification of a peptide-pheromone that enhances Listeria monocytogenes escape from host cell vacuoles

Listeria monocytogenes is a Gram-positive facultative intracellular bacterial pathogen that invades mammalian cells and escapes from membrane-bound vacuoles to replicate within the host cell cytosol. Gene products required for intracellular bacterial growth and bacterial spread to adjacent cells are regulated by a transcriptional activator known as PrfA. PrfA becomes activated following L. monocytogenes entry into host cells, however the signal that stimulates PrfA activation has not yet been defined. Here we provide evidence for L. monocytogenes secretion of a small peptide pheromone, pPplA, which enhances the escape of L. monocytogenes from host cell vacuoles and may facilitate PrfA activation. The pPplA pheromone is generated via the proteolytic processing of the PplA lipoprotein secretion signal peptide. While the PplA lipoprotein is dispensable for pathogenesis, bacteria lacking the pPplA pheromone are significantly attenuated for virulence in mice and have a reduced efficiency of bacterial escape from the vacuoles of nonprofessional phagocytic cells. Mutational activation of PrfA restores virulence and eliminates the need for pPplA-dependent signaling. Experimental evidence suggests that the pPplA peptide may help signal to L. monocytogenes its presence within the confines of the host cell vacuole, stimulating the expression of gene products that contribute to vacuole escape and facilitating PrfA activation to promote bacterial growth within the cytosol.

Identification of protein components of egg masses indicates parental investment in immunoprotection of offspring by Biomphalaria glabrata (gastropoda, mollusca)

The macromolecules contributed by the freshwater gastropod Biomphalaria glabrata, intermediate host of Schistosoma mansoni, to developing offspring inside egg masses are poorly known. SDS-PAGE fractionated egg mass fluids (EMF) of M line and BB02 B. glabrata were analyzed by MALDI-TOF (MS and tandem MS). A MASCOT database was assembled with EST data from B. glabrata and other molluscs to aid in sequence characterization. Of approximately 20 major EMF polypeptides, 16 were identified as defense-related, including protease inhibitors, a hemocyanin-like factor and tyrosinase (each with possible phenoloxidase activity), extracellular Cu-Zn SOD, two categories of C-type lectins, Gram-negative bacteria-binding protein (GNBP), aplysianin/achacin-like protein, as well as versions of lipopolysaccharide binding protein/bacterial permeability-increasing proteins (LBP/BPI) that differed from those previously described from hemocytes. Along with two sequences that were encoded by "unknown" ESTs, EMF also yielded a compound containing a vWF domain that is likely involved in defense and a polypeptide with homology to the Aplysia pheromone temptin. Further study of B. glabrata pheromones is warranted as these could be useful in efforts to control these schistosome-transmitting snails. Several of the EMF polypeptides were contained in the albumen gland, the organ that produces most EMF. Thus, parental investment of B. glabrata in immunoprotection of its offspring is indicated to be considerable.

Female scent signals enhance the resistance of male mice to influenza

Background

The scent from receptive female mice functions as a signal, which stimulates male mice to search for potential mating partners. This searching behavior is coupled with infection risk due to sniffing both scent marks as well as nasal and anogenital areas of females, which harbor bacteria and viruses. Consideration of host evolution under unavoidable parasitic pressures, including helminthes, bacteria, viruses, etc., predicts adaptations that help protect hosts against the parasites associated with mating.

Methods and Findings

We propose that the perception of female signals by BALB/c male mice leads to adaptive redistribution of the immune defense directed to protection against respiratory infection risks. Our results demonstrate migration of macrophages and neutrophils to the upper airways upon exposure to female odor stimuli, which results in an increased resistance of the males to experimental influenza virus infection. This moderate leukocyte intervention had no negative effect on the aerobic performance in male mice.

Conclusions

Our data provide the first demonstration of the adaptive immunological response to female odor stimuli through induction of nonspecific immune responses in the upper respiratory tract.

Tissue localization of bovine dander allergen Bos d 2

BACKGROUND

Domestic mammals are important sources of indoor allergens. However, the origin at the tissue level and the biologic function of mammalian allergens are largely unknown.

OBJECTIVE

The aim of this study was to localize the source of the major bovine dander allergen, Bos d 2, in bovine tissues.

METHODS

Samples from several organs were tested for the presence of mRNA encoding Bos d 2 and Bos d 2 protein by using the reverse transcriptase polymerase chain reaction and immunohistochemical staining, respectively.

RESULTS

Skin proved to be the only tissue where mRNA encoding Bos d 2 was detected. This observation was confirmed by immunohistochemistry with a monoclonal anti-Bos d 2 antibody as the primary antibody. In the skin sections, Bos d 2 was found in the secretory cells of apocrine sweat glands and the basement membranes of the epithelium and hair follicles. Bos d 2 belongs to the family of lipocalins comprising a number of pheromone carrier proteins that are present, for example, in the secretions of the apocrine sweat glands.

CONCLUSION

Together with earlier data, our findings suggest that Bos d 2 is produced in sweat glands and transported to the skin surface as a carrier of the pheromone ligand. Because dander allergens of a number of mammalian species are lipocalins, the common biologic function of being pheromone carriers seems to be a common feature of an important group of aeroallergens.

Chemical and immunological analysis of prey-derived vomeronasal stimulants

We have isolated seven proteins from earthworm preparations that are chemoattractive to garter snakes. Three of these proteins have been purified to homogeneity: two from aqueous earthworm wash (EWW) and one from electric shock-induced earthworm secretion (ESS). One of the two highly purified proteins from EWW has a relative molecular mass of 20 kDa and contains free sulfhydryl groups that appear to play a functional role in its chemoattractivity. The other purified protein from EWW has a molecular mass of 3 kDa (low molecular weight protein, LMW). The highly purified chemoattractive protein (ES20) from ESS is a glycoprotein having a minimum molecular mass of 15.4 kDa calculated from its amino acid and carbohydrate contents. It consists of a single polypeptide chain. The sequence of terminal 15 amino acid residues from its amino (NH2-) terminal has been determined. It binds specifically to the membranes of vomeronasal sensory epithelium in a saturable and reversible fashion with a Kd value of about 0.3 microM and Bmax value of 0.4 nmol/mg of protein. This protein causes an increase in firing rate of individual neurons in the accessory olfactory bulb of garter snakes, the projection site for vomeronasal neurons. All the isolated chemoattractive proteins from both earthworm preparations can be divided immunologically into three groups: (i) those closely related to the ES20 snake-attractive protein, (ii) those closely related to the LMW snake-attractive protein, and (iii) those unrelated to either ES20 or the LMW protein.

The use of polyclonal activators in the production of murine monoclonal and polyclonal antibodies

We propose a new immunization method to stimulate a strong immune response against weak or diluted antigens. This technique is based on stimulation with polyclonal activators before exposure to the antigens. We also discuss the efficiency of various types of mitogen with particular regard to their capacity to produce monoclonal antibodies and serum antibodies. A specific immune response against soluble antigens is increased by pretreating mice with PPD. This preactivation permitted us to obtain monoclonal antibodies against weak antigens in a few days. No monoclonal antibodies were obtained by inoculating weak antigens or the activators by themselves.

Specific and common epitopes in mating pheromones of Euplotes raikovi revealed by monoclonal antibodies

Polypeptide mating pheromones Er-1 and Er-2, purified from the supernatant of Euplotes raikovi cultures of mating type I and mating type II, respectively, were used to immunize mice and obtain monoclonal antibodies. Five hybridoma clones producing antibodies specific to the mating pheromones were selected. They were analyzed for immunospecificity by immunoperoxidase assay, immunoblotting, and for their efficacy in inhibition of mating pheromone activity. Monoclonal antibodies from two hybridoma clones recognized only the mating pheromone used as antigen: those from the other three clones reacted, to comparable extents, with both mating pheromones. On the basis of these results it was assumed that two immunogenic sites exist in Er-1 and Er-2, one specific and the other common to both mating pheromones.

Monoclonal antibodies to cell surface antigens involved in sex pheromone induced mating in Streptococcus faecalis

Hybridoma cell lines producing monoclonal antibodies to Streptococcus faecalis cell surface antigens were constructed. Some of the antibodies isolated were directed against surface components involved in pheromone-induced mating. This paper describes the use of the monoclonal antibodies to identify antigenically related surface components detected by immunoprecipitation and Western blotting, their use in pheromone response assays, and their use as functional inhibitors in mating experiments.

Antibodies against the alpha-factor pheromone of Saccharomyces cerevisiae

The mating pheromone of baker's yeast, the alpha-factor, is a dodeka-/tridecapeptide, which is not antigenic by itself. It was coupled to succinylated thyroglobulin by the carbodiimide procedure to facilitate selective coupling of the alpha-factor mainly by its N-terminal region. Antibodies against this conjugate were raised in rabbits. After selective precipitation of the rabbit antiserum with succinylated carrier prior to the radial double diffusion test (Ouchterlony) specific antibodies against the coupled alpha-factor could be detected.

Plasmid content of Streptococcus faecalis strain 39-5 and identification of a pheromone (cPD1)-induced surface antigen

Streptococcus faecalis 39-5 is a haemolytic, bacteriocinogenic strain harbouring six plasmids. One of these plasmids, pPD1 (36.4 MDal) determines a bacteriocin and encodes a conjugative response to the sex pheromone cPD1 excreted by recipient (plasmid-free) strains. The pheromone response is characterized by the formation of mating aggregates of donors (responders) with recipients. Aggregation required the presence of phosphate and divalent cations and was inhibited by agents or conditions that destroy protein structure. Aggregation was postulated to be due to synthesis of a new proteinaceous molecule on the donor cell surface. Referred to as 'aggregation substance', such a material was identified and found to exhibit antigenic properties not associated with uninduced cells; it could be detected by immunoelectron microscopy. Aggregation substance could be extracted from induced cells but not uninduced cells as demonstrated by crossed immunoelectrophoresis. Antibody raised against the aggregation substance controlled by pPD1 cross-reacted with aggregation substance determined by other plasmid systems which respond to pheromones unrelated to cPD1.