Altered thermoregulation in the iguana disposaurus dorsalis following exercise

1. 1.|Seven desert iguanas ran on a motorized treadmill for 20-min periods. Before, during and after exercise, the iguanas were in a thermal gradient which allowed them to thermoregulate behaviourally.2. 2.|For several hours following exercise, the iguanas selected warmer ambient temperatures, resulting in small, but statistically significant, increases in body temperature.3. 3.|The increases in temperature were proportional to the exercise intensity.4. 4.|These changes were not observed if exercised was preceded by administration of the antipyretic drug, sodium salicylate.5. 5.|These data support the hypothesis that exercise causes a change in central thermoregulatory control which may be similar to fever caused by infection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25757/1/0000318.pd

Down-regulation of CD46 by Piliated Neisseria gonorrhoeae

Human membrane cofactor protein (CD46) protects host cells against complement attack and may function as a receptor for pathogenic Neisseriae. We assessed CD46 expression in the human cervical cell line ME-180 after exposure to Neisseria gonorrhoeae. Piliated but not nonpiliated gonococci adhered to cells and produced up to an 80% reduction in CD46 surface expression by 6 h that persisted for at least 24 h. This response required a minimum multiplicity of infection of 10 and was not prevented by antibodies to CD46. CD46 down-regulation was not attributable to intracellular retention or a global or specific shutdown of mRNA or protein synthesis. Substantial quantities of CD46 were found in the supernatants, indicating a specific shedding of this protein. Adherent gonococci lacking the pilus retraction protein PilT did not down-regulate CD46 but de-repression of pilT expression restored CD46 down-regulation. After experimental infection of human volunteers with a gonococcal variant incapable of inducing CD46 down-regulation, variants of this strain were reisolated that exhibited CD46 down-regulation. Pilus-mediated interactions of gonococci with human epithelial cells results in a pathogen-induced manipulation of the host cell environment in which a membrane protein is removed from epithelial cells by liberation into the surrounding milieu

Beta-turn formation in the processing region is important for efficient maturation of Escherichia coli maltose-binding protein by signal peptidase I in vivo.

Signal peptidase I (also called leader peptidase) is the endopeptidase that removes the signal peptides of most secreted proteins during or after translocation in Escherichia coli. Precursor recognition is contingent in part on the presence of small, uncharged residues in the -3 and -1 positions relative to the cleavage site, and may also depend on the structure of the processing region. Most precursor processing regions include residues likely to form a beta-turn. Mutations were introduced into the processing region of maltose-binding protein (MBP) that altered the prediction of beta-turn formation in this region. MBP species with a decreased probability of beta-turn formation were processed slowly or not at all, whereas MBP species with an increased probability of beta-turn formation were processed efficiently. Mutations altering the prediction of beta-turn formation in the MBP processing region were also made in cis to a proline in the +1 position. Cleavage at the normal processing site is blocked by proline in the +1 position; this MBP species, MBP27-P, inhibits processing of other proteins by signal peptidase I. Decreasing the probability of beta-turn formation in the processing region of MBP27-P eliminated the inhibition of signal peptidase I, and these MBP27-P derivatives remained unprocessed, suggesting that the formation of a beta-turn in the MBP processing region was necessary for recognition by signal peptidase I. Increasing the probability of beta-turn formation in cis to proline at +1 in MBP did not alter recognition of the protein by the processing enzyme. The results presented here are consistent with the hypothesis that the efficiency of recognition and processing by signal peptidase I is increased by the formation of a beta-turn in the processing region of the MBP signal peptide

Antigenic and structural differences among six proteins II expressed by a single strain of Neisseria gonorrhoeae.

Gonococci express a family of related outer membrane proteins designated protein II (P.II), which undergo both phase and antigenic variation. Six P.II proteins have been identified in strain FA1090. We developed monoclonal antibodies specific for each P.II protein. Using these antibodies as probes, we purified the six different P.II proteins of this strain. Despite the relatedness of the proteins, we could not purify all of them by a single purification scheme. Four P.II proteins were purified by chromatofocusing, and the remaining two proteins were purified by hydrophobic interaction chromatography on phenyl-Sepharose. The N-terminal amino acid sequence of the proteins showed a high degree of sequence conservation. However, there was variability at specific amino acid residues, giving each P.II protein a unique N-terminal amino acid sequence. Thus P.II proteins of one strain differ among themselves not only in antigenic determinants and primary structure, but also in other characteristics affecting their properties in different chromatographic systems

Mouse genetic locus Lps influences susceptibility to Neisseria meningitidis infection.

We surveyed a number of inbred mouse strains for susceptibility to meningococcemia. Mice of all strains became bacteremic after intraperitoneal injection of a serogroup C, serotype 2a human disease isolate, but the strains differed in levels of bacteremia, indicating influences of the host genome on susceptibility. There was no significant correlation between level of bacteremia and differences at major histocompatibility or immunoglobulin loci; the Salmonella susceptibility locus, Ity; the complement C5 locus, Hc; the antibody response locus, xid; or the transferrin locus, Trf. However, the Lps locus, which influences a range of host cellular responses to endotoxin and affects susceptibility to Salmonella typhimurium, did influence susceptibility to meningococcemia. There were significant differences in levels of bacteremia between C3H/HeJ (Lpsd) mice and each of the other strains (all Lpsn). We confirmed the association of the Lpsd genotype with susceptibility by using coisogenic strains from two widely separated mouse lineages: C3H and B10. Lpsd mice experienced a 1,000-fold proliferation of bacteria and were bacteremic for days before clearing the infection. In contrast, Lpsn mice cleared the bacteremia in less than 1 day. There was no difference in meningococcal growth in vitro in serum from C3H/HeJ and coisogenic C3H/HeN (Lpsn) mice, suggesting that the Lps-related difference in susceptibility may involve a cellular response

Characterization of Neisseria gonorrhoeae protein II phase variation by use of monoclonal antibodies.

The protein II (P.11) outer membrane proteins of Neisseria gonorrhoeae, which have been implicated in gonococcal pathogenesis, have been previously shown to undergo a type of phase variation in which expression of any of several different forms of the proteins may be switched on or off. We identified six electrophoretically distinct forms of P.11 proteins (designated P.IIa through P.11f) within strain FA1090, and we isolated colonial variants of FA1090 that expressed only one of the six different P.11 protein forms. Two monoclonal antibodies that bound specifically and differentially to P.11 proteins were produced. One antibody bound to proteins P.IIb and P.Ild and was bactericidal for all colonial variants expressing P.IIb. The second antibody bound to P.IIa and was bactericidal for colonial variants expressing P.IIa. P.JI protein profiles of survivors of antibody killing indicated that multiple P.11 protein species may be expressed on a single bacterium and that P.11 protein switching in the gonococcus is nonrandom

Resistance to meningococcemia apparently conferred by anti-H.8 monoclonal antibody is due to contaminating endotoxin and not to specific immunoprotection.

We evaluated the ability of a monoclonal antibody directed against the common H.8 antigen of pathogenic Neisseria sp. to confer passive protection against meningococcal disease in mice. The apparent protection conferred by antibody purified from tissue culture supernatant was actually the result of endotoxin contamination of buffers and tissue culture media. Endotoxin-free anti-H.8 antibody was not protective. The possibility of endotoxin contamination should be considered when evaluating immunity conferred by passively administered antibody in animal models

Rapid Publication Multiple Gonococcal Pilin Antigenic Variants Are Produced during Experimental Human Infections

Abstract Gonococcal pilin variation is thought to allow immune evasion and change the adherence properties of the pilus. We have examined the process of pilin antigenic variation in human volunteers inoculated with strain FA1090. Our data show that pilin variation occurred throughout the process of infection, that at each time sampled after inoculation multiple pilin variants were present, and that later pilin variants appear to be recombinants between previously expressed genes and the silent storage pilin copies. Thus, during infection a large repertoire of proteins are available to the population to help avoid immune responses, to provide pili with varying functions, and to transmit to a new host. (J. Clin. Invest. 1994. 93:2744-274

Multiple gonococcal opacity proteins are expressed during experimental urethral infection in the male

The opacity (Opa) proteins of Neisseria gonorrhoeae are a family of outer membrane proteins demonstrating phase and antigenic variation. N. gonorrhoeae strain FA0190 has 11 opa loci that encode at least 8 antigenically distinct Opa proteins. To determine if expression of one Opa protein or a subset of them is favored during gonococcal infection, we inoculated Opa-negative variants of strain FA1090 intraurethrally into male volunteers. The Opa phenotype of gonococci isolated from urine and urethral swab cultures from nine infected subjects was determined. Opa proteins were expressed in a large proportion of the reisolates from the infected subjects. Gonococci cultured from urine or urethral swab samples from six of the subjects were uniformly Opa positive, with the predominant Opa variants differing among subjects. Three different Opa proteins were represented as the predominant type in at least one subject each. In three subjects, there was more heterogeneity in Opa phenotype of the reisolates, including the presence of Opa-negative variants. An increase in the proportion of isolates expressing multiple Opa proteins occurred over time in most subjects. Passage of the inoculum in vitro did not result in similar changes in Opa expression. There was no detectable difference in infectivity of an Opa-negative variant and one expressing an Opa protein (OpaF) that was highly represented in reisolates from the original nine subjects. Reisolates from three infected volunteers inoculated with the OpaF variant showed continued expression of OpaF alone or in conjunction with other Opa proteins. These results demonstrate that there is strong selection for expression of one or more Opa proteins by strain FA1090 in vivo, but that no single protein is preferentially expressed during early infection in the male urethra