Adoptive transfer of protection against Trypanosoma cruzi with lymphocytes and macrophages.

Female C57BL/6J mice were infected with Trypanosoma cruzi and subsequently given macrophages or lymphocytes from syngeneic donors which had recovered from the acute infection. Mice which received immune peritoneal macrophages, splenic lymphocytes, or lymph node lymphocytes developed lower mean parasitemias and cumulative mortalities than did recipients of nonimmune cells. Neither peritoneal lymphocytes nor splenic macrophages were protective, however. These studies indicate that splenic and lymph node lymphocytes are effective in transferring protection against T. cruzi, whereas the macrophage is somewhat less effective.     

Detectability in computed tomographic images.

The detection limitations inherent in statistically limited computed tomographic (CT) images are described through the application of signal detection theory. The detectability of large-area, low-contrast objects is shown to be chiefly dependent upon the low-frequency content of the noise power spectral density. For projection data containg uncorrelated noise, the resulting ramplike, low-frequency behavior of the noise power spectrum of CT reconstructions may be conveniently characterized by the number of noise-equivalent x-ray quanta (NEQ) detected in the projection measurements. The NEQ for a given image may be determined either from a measurement of the noise power spectrum or from the noise granularity computed with an appropriate weighting function. A measure of the efficiency of scanner dose utilization is proposed which compares the average dose to that required by an ideal scanner to obtain the same NEQ.     

A new PAX6 mutation in familial aniridia.

Aniridia (lack of iris) is caused by loss of function mutations in one copy of the PAX6 gene. Here we present a new PAX6 splice mutation in a family with autosomal dominant aniridia. The mutation is a single nucleotide change which, although occurring within an exon, affects the splice junction consensus and results in skipping of that exon.     

Expression of the heat-modifiable major outer membrane protein of Haemophilus influenzae type b is unrelated to virulence.

The heat-modifiable major outer membrane protein (P1) of Haemophilus influenzae type b (Hib) has been shown to be both exposed on the cell surface and capable of inducing the synthesis of antibodies protective against experimental Hib disease. Chemical mutagenesis of a recombinant plasmid containing the Hib gene encoding P1 resulted in inactivation of P1 expression by this plasmid. The mutated P1 gene was transformed into Hib to obtain an isogenic mutant lacking only the ability to synthesize this surface protein. In addition, the P1 gene was inserted into a plasmid shuttle vector and used to construct a recombinant Hib strain that overexpressed the P1 protein. Lack of P1 expression did not affect the ability of Hib to grow in vitro. Neither the absence nor the overproduction of P1 affected expression of capsular polysaccharide and lipooligosaccharide by Hib. The P1-negative mutant and the P1-overexpressing strain were both as susceptible to the bactericidal activity of pooled normal human serum as was the wild-type parent strain, while the P1-negative mutant was as resistant to the bactericidal activity of normal infant rat serum as was the wild-type parent strain. The P1-negative mutant was no less virulent than was the wild-type parent strain in an animal model system, such that both the numbers of animals infected by this mutant and the mean magnitudes of the resultant bacteremias were essentially identical to those obtained with challenge by the wild-type parent strain. Similarly, overexpression of P1 did not detectably affect the virulence of Hib. These data indicate that this protective protein antigen plays no detectable role in the expression of virulence by Hib, as assessed in an animal model system.     

Biochemical identification of citrobacteria in the clinical laboratory.

We biochemically identified 235 Citrobacter strains to the species level on the basis of the recently proposed taxonomic changes of Brenner et al. (D. J. Brenner, P. A. D. Grimont, A. G. Steigerwalt, G. R. Fanning, E. Ageron, and C. F. Riddle, Int. J. Syst. Bacteriol. 43:645-658, 1993). Citrobacter isolates were initially identified as C. koseri or as members of the C. freundii complex or C. amalonaticus group on the basis of indole production, formation of H2S, malonate utilization, and acid production from D-arabitol and adonitol. On the basis of the results of these tests, 68% of the Citrobacter strains were identified as members of the C. freundii complex, 25% were C. koseri, and 8% were members of the C. amalonaticus group. By using a 15-test system recently proposed by Brenner et al. (D. J. Brenner, P. A. D. Grimont, A. G. Steigerwalt, G. R. Fanning, E. Ageron, and C. F. Riddle, Int. J. Syst. Bacteriol. 43:645-658, 1993) to help identify new species in the C. freundii complex and C. amalonaticus group, 81% of the C. freundii complex strains and 100% of the C. amalonaticus strains could be definitively assigned to one of the previously established or recently designated species or hybridization groups of the genus Citrobacter. Within the C. freundii complex, C. freundii predominated overall (37%), followed by C. youngae (24%), C. braakii (13%), and C. werkmanii (6%). Only one strain each of C. sedlakii and Citrobacter DNA group 11 was identified in this study. Among C. amalonaticus complex members, all were identified as C. amalonaticus with the singular exception of one fecal isolate of C. farmeri. C. freundii and C. koseri were the two Citrobacter species most commonly (80 of 93 [86%]) isolated from extraintestinal sources (genitourinary tract, wounds, blood).     

Aberrant T-cell function in vitro and impaired T-cell dependent antibody response in vivo in vitamin A-deficient rats.

We have previously reported that vitamin A deficiency resulted in a reduced IgA antibody response to cholera toxin (CT) after per-oral immunization. In the present investigation we have studied the in vivo and in vitro immune response in vitamin A-deficient rats to two parenterally applied antigens, beta-lactoglobulin (beta-LG) and picrylsulphonic acid (TNP)-Ficoll. The serum IgG and IgM antibody responses to the T-cell dependent antigen beta-LG were significantly lower in the vitamin A-deficient rats than in the pair-fed control rats. No such differences were seen with the IgG and IgM responses to the T-cell independent antigen TNP-Ficoll. However, the biliary IgA and the serum IgE antibodies against both antigens were decreased in the vitamin A-deficient rats. In vitro lymphocyte stimulation with concanavalin A (Con A) or beta-LG gave higher T-cell proliferation rates in the vitamin A-deficient than in the control rats. Interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) levels in supernatants from Con A-stimulated mesenteric lymph node cells were also higher in the vitamin A-deficient rats, while IL-6 levels were decreased, which is consistent with an up-regulated Th1 activity. Proliferation studies on purified accessory cells and T cells from the deficient and the control rats, mixed in different combinations, showed that the T cells, but not the accessory cells, were disturbed in the vitamin A-deficient rats. Despite the increased T-cell activity in vitro the vitamin A-deficient rats had a lower delayed-type hypersensitivity (DTH) reaction than the pair-fed control rats. In conclusion, the increased IL-2 and IFN-gamma levels may reflect an up-regulation of Th1 cell function, while the decreased IgA, IgE and IL-6 levels indicate a suppression of Th2 cells. The disturbed T-lymphocyte function is manifested in vivo as a decreased DTH reaction and suppressed antibody production, the latter possibly due to a lack of B-cell switching and proliferation factors in vitamin A-deficient rats.     

Secretory IgA and IgM antibodies to E. coli O and poliovirus type I antigens occur in amniotic fluid,meconium and saliva from newborns. A neonatal immune response without antigenic exposure: a result of anti-idiotypic induction?

Antibodies to E. coli O-antigens and poliovirus type I antigen as well as total SIgA were analysed using enzyme-linked immunosorbent assay (ELISA), in amniotic fluid and in meconium, urine and saliva from neonates. Secretory IgA and IgM antibodies to E. coli and poliovirus antigens were found in saliva as well as in most meconium samples taken during the first day of life. SIgA could be quantified in all types of samples including amniotic fluid. The finding of secretory IgA and IgM antibodies to E. coli and poliovirus type I antigens in early samples from an infant of a hypogammaglobulinaemic mother, given regular intravenous (i.v.) immunoglobulin prophylaxis, but still lacking IgA and IgM antibodies, supports a fetal origin for at least part of the secretory antibodies detected in the different samples. Since it is unlikely that the fetus has been exposed to poliovirus, which is rare in Sweden, it is hypothesized that the stimulus inducing the SIgA and IgM antibodies found in the neonate could be anti-idiotypic antibodies from the mother.     

Human leukocyte antigen-DQ8 transgenic mice: a model to examine the toxicity of aerosolized staphylococcal enterotoxin B

Staphylococcal enterotoxins (SEs) belong to a large group of bacterial exotoxins that cause severe immunopathologies, especially when delivered as an aerosol. SEs elicit the release of lethal amounts of cytokines by binding to major histocompatibility complex (MHC) class II and cross-linking susceptible T-cell receptors. Efforts to develop effective therapeutic strategies to protect against SEs delivered as an aerosol have been hampered by the lack of small animal models that consistently emulate human responses to these toxins. Here, we report that human leukocyte antigen-DQ8 (HLA-DQ8) transgenic (Tg) mice, but not littermate controls, succumbed to lethal shock induced by SEB aerosols without potentiation. Substantial amounts of perivascular edema and inflammatory infiltrates were noted in the lungs of Tg mice, similar to the pathology observed in nonhuman primates exposed by aerosol to SEB. Furthermore, the observed pathologies and lethal shock correlated with an upsurge in proinflammatory cytokine mRNA gene expression in the lungs and spleens, as well as with marked increases in the levels of proinflammatory circulating cytokines in the Tg mice. Unlike the case for littermate controls, telemetric evaluation showed significant hypothermia in Tg mice exposed to lethal doses of SEB. Taken together, these results show that this murine model will allow for the examination of therapeutics and vaccines developed specifically against SEB aerosol exposure and possibly other bacterial superantigens in the context of human MHC class II receptors.     

Impaired mucosal antibody response to cholera toxin in vitamin A-deficient rats immunized with oral cholera vaccine.

To investigate the importance of vitamin A in the ability to respond to oral antigen administration, rats were fed a vitamin A-free diet. The animals were immunized perorally three times with a mixture of cholera toxin (CT) and a commercial cholera vaccine. The total immunoglobulin A (IgA) concentration as well as the specific IgA anti-CT antibody levels in serum and bile was significantly lower in the vitamin A-deficient animals than in the paired fed controls (animals that were fed a normal commercial diet in an amount equal to the amount the deficient animals consumed), while the levels of total and specific anti-CT IgG were not affected to the same extent by the vitamin A deficiency. The number of IgA anti-CT antibody-producing cells in the mesenteric lymph nodes after immunization was also significantly lower in the vitamin A-deficient rats than in the control rats. Supplementation of the diet with retinyl palmitate restored the ability to mount an IgA antibody response to the antigen, since the level of specific IgA anti-CT antibodies in relation to the total IgA concentration was as high in the vitamin A-supplemented group as in the paired fed control group. Restricted diet intake by itself did not affect the ability to respond adequately to the antigen since there was no difference in IgA anti-CT antibody level between paired fed rats and those being fed ad libitum. Assessment of transforming growth factor beta in cell cultures revealed no difference between vitamin A-deficient and paired fed animals. In summary, vitamin A deficiency resulted in a decreased number of IgA-producing cells, decreased IgA production, and a reduced ability to respond with IgA antibodies to the oral cholera vaccine.