The CD8 ؉ T cell diaspora has been analyzed after secondary challenge with an influenza A virus that replicates only in the respiratory tract. Numbers of D b NP366-and D b PA224-specific CD8 ؉ T cells were measured by tetramer staining at the end of the recall response, then followed sequentially in the lung, lymph nodes, spleen, blood, and other organs. The extent of clonal expansion did not reflect the sizes of the preexisting memory T cell pools. Although the high-frequency CD8 ؉ tetramer ؉ populations in the pneumonic lung and mediastinal lymph nodes fell rapidly from peak values, the ''whole mouse'' virus-specific CD8 ؉ T cell counts decreased only 2-fold over the 4 weeks after infection, then subsided at a fairly steady rate to reach a plateau at about 2 months. The largest numbers were found throughout in the spleen, then the bone marrow. The CD8 ؉ D b NP366 ؉ and CD8 ؉ D b PA224 ؉ sets remained significantly enlarged for at least 4 months, declining at equivalent rates while retaining the nucleoprotein > acid polymerase immunodominance hierarchy characteristic of the earlier antigendriven phase. Lowest levels of the CD69 ''activation marker'' were detected consistently on virus-specific CD8 ؉ T cells in the blood, then the spleen. Those in the bone marrow and liver were intermediate, and CD69 hi T cells were very prominent in the regional lymph nodes and the nasal-associated lymphoid tissue. Any population of ''resting'' CD8 ؉ memory T cells is thus phenotypically heterogeneous, widely dispersed, and subject to broad homeostatic and local environmental effects irrespective of epitope specificity or magnitude.T he vertebrate immune system is dynamic, mobile, and anatomically dispersed. Mammalian immune responses are thought to develop predominantly in the circumscribed microenvironments of the secondary lymphoid tissue, the lymph nodes (LNs), spleen, and foci embedded in mucosal sites such as the Peyer's patches (PP). However, the cellular elements of immunity, particularly the CD4 ϩ and CD8 ϩ T cells, are known to move via blood and lymph through a spectrum of other organs that are not normally considered to be part of the immune system. Measuring the extent of this lymphocyte diaspora has only recently become possible with the development of tetrameric complexes of MHC class I glycoprotein ϩ peptide (tetramers) for the direct, flow cytometric identification of antigen-specific CD8 ϩ T cells (1Ϫ5). The tetramers allow us to quantitate both the CD8 ϩ T cell response to pathogens and the subsequent return to homeostasis after the elimination of the invading organism.Analysis of the diaspora effect in viral immunity should optimally distinguish between the antigen-driven dispersion of CD8 ϩ effectors to sites of virus replication and distribution profiles ref lecting the normal physiology of lymphocyte recirculation. The latter will be more characteristic of a localized infection. The inf luenza A viruses replicate only in respiratory epithelium, although they also can undergo a defective growth cycle in ot...

BackgroundMultidrug resistant Acinetobacter baumannii, (MRAB) is an important cause of hospital acquired infection. The purpose of this study is to determine the risk factors for MRAB in a city hospital patient population.MethodsThis study is a retrospective review of a city hospital epidemiology data base and includes 247 isolates of Acinetobacter baumannii (AB) from 164 patients. Multidrug resistant Acinetobacter baumannii was defined as resistance to more than three classes of antibiotics. Using the non-MRAB isolates as the control group, the risk factors for the acquisition of MRAB were determined.ResultsOf the 247 AB isolates 72% (177) were multidrug resistant. Fifty-eight percent (143/247) of isolates were highly resistant (resistant to imipenem, amikacin, and ampicillin-sulbactam). Of the 37 patients who died with Acinetobacter colonization/infection, 32 (86%) patients had the organism recovered from the respiratory tract. The factors which were found to be significantly associated (p ≤ 0.05) with multidrug resistance include the recovery of AB from multiple sites, mechanical ventilation, previous antibiotic exposure, and the presence of neurologic impairment. Multidrug resistant Acinetobacter was associated with significant mortality when compared with sensitive strains (p ≤ 0.01). When surgical patients (N = 75) were considered separately, mechanical ventilation and multiple isolates remained the factors significantly associated with the development of multidrug resistant Acinetobacter. Among surgical patients 46/75 (61%) grew a multidrug resistant strain of AB and 37/75 (40%) were resistant to all commonly used antibiotics including aminoglycosides, cephalosporins, carbepenems, extended spectrum penicillins, and quinolones. Thirty-five percent of the surgical patients had AB cultured from multiple sites and 57% of the Acinetobacter isolates were associated with a co-infecting organism, usually a Staphylococcus or Pseudomonas. As in medical patients, the isolation of Acinetobacter from multiple sites and the need for mechanical ventilation were significantly associated with the development of MRAB.ConclusionsThe factors significantly associated with MRAB in both the general patient population and surgical patients were mechanical ventilation and the recovery of Acinetobacter from multiple anatomic sites. Previous antibiotic use and neurologic impairment were significant factors in medical patients. Colonization or infection with MRAB is associated with increased mortality.

The objective of the present study was to determine the relationship between concentrations of antibodies in serum and those in gingival crevicular fluid (GCF) of patients with juvenile periodontitis and severe periodontitis. Most antigens used to quantitate antibodies were obtained from a panel of bacteria associated with juvenile periodontitis or severe periodonititis. We further investigated variation in antibody titer among different periodontal sites and the extent to which antibody in GCF is locally derived. Titers of antibody, total immunoglobulin G (IgG), and human serum albumin were determined with sensitive radioimmunoassays. The relationship between serum and GCF antibody was complex. Both person-to-person variability and marked variability within the same subject were found among different sites of similar clinical status. The site-to-site variability was found not only for ailtibody reactive with periodontal organisms, but also for antitetanus toxoid, total IgG, and even human serum albumin. Generally the variability was in the degree of depression of the level in GCF relative to that in serum. However, anti-Bacteroides gingivalis and anti-Actinobacillus actinomycetemcomitans in GCF often exceeded the level in serum. When antibody titers in serum and GCF were calculated per milligram of human serum albumin, most of the apparent depressions of antibody in GCF disappeared. The ratio of antibody in serum to that in GCF approached unity for all organisms except B. gingivalis and A. actinomycetemcomitans Y4, which were markedly elevated. Furthermore, the level of IgG per milligram of human serum albumin in GCF was about twice the level in serum. We believe that human serum albumin reflects serum contribution to the GCF, and we therefore attribute the increased level of IgG per milligram of albumin in GCF to local synthesis. It appears that anti-B. gingivalis and anti-A. actinomycetemcomitans represent an important portion of this local antibody synthesis, since most seropositive patients with severe or juvenile periodontitis had at least one site elevated, and the magnitudes of the elevations were large in many sites. Those sites yielding elevated antibody exhibited no obvious differences in clinical parameters of probeable depth or attachment level as compared with sites in which antibody levels in GCF were similar to serum levels. Elevated antibody in GCF may relate to changes in disease activity that are not detectable by usual clinical measures.

The compounds 4-amino-Neu5Ac2en (5-acetylamino-2,6-anhydro-4-amino-3,4,5- trideoxy-D-glycerol-D-galacto-non-2-enoic acid) and 4-guanidino-Neu5Ac2en (5-acetylamino-2,6-anhydro-4-guanidino-3,4,5- trideoxy-D-glycerol-D-galacto-non-2-enoic acid), which selectively inhibit the influenza virus neuraminidase, have been tested in vitro for their ability to generate drug-resistant variants. NWS/G70C virus (H1N9) was cultured in each drug by limiting-dilution passaging. After five or six passages in either compound, there emerged viruses which had a reduced sensitivity to the inhibitors in cell culture. Variant viruses were up to 1,000-fold less sensitive in plaque assays, liquid culture, and a hemagglutination-elution assay. In addition, cross-resistance to both compounds was seen in all three assays. Some isolates demonstrated drug dependence with an increase in both size and number of plaques in a plaque assay and an increase in virus yield in liquid culture in the presence of inhibitors. No significant difference in neuraminidase enzyme activity was detected in vitro, and no sequence changes in the conserved sites of the neuraminidase were found. However, changes in conserved amino acids in the hemagglutinin were detected. These amino acids were associated with either the hemagglutinin receptor binding site, Thr-155, or the left edge of the receptor binding pocket, Val-223 and Arg-229. Hence, mutations at these sites could be expected to affect the affinity or specificity of the hemagglutinin binding. Compensating mutations resulting in a weakly binding hemagglutinin thus seem to be circumventing the inhibition of the neuraminidase by allowing the virus to be released from cells with less dependence on the neuraminidase.

In the present study we sought to determine whether serum antibody was present against microorganisms which predominate in the subgingival flora of young adults with generalized severe periodontitis (SP). Subjects with SP were often seropositive for Eubacterium brachy, Fusobacterium nucleatum E3C22, and Peptostreptococcus micros, whereas subjects with juvenile periodontitis (JP) and subjects with healthy periodontium (HP) were not. Both SP and JP subjects were more frequently seropositive for Bacteroides gingivalis, F. nucleatum D52B16, and F. nucleatum ElDl than were HP subjects. The data were most striking for B. gingivalis, for which both the incidence and the magnitude of specific antibody was clearly elevated for SP and JP subject groups. However, SP subjects generally had either a high antibody titer or no detectable titer. In contrast, JP and HP subjects generally had at least very small amounts of antibody. Except at very low levels of antibody, neither SP nor JP groups differed significantly from the HP group for antibody to Eubacterium nodatum, Bacteroides intermedius (homology group 4197 or 8944), or Lactobacilus minutus antibody. There was a high frequency of antibody to.E. nodatum, with very high titers in all groups despite the fact that this organism is rarely found in HP subjects. For Eubacterium timidum, the JP group was clearly more frequently seropositive than the HP group. Despite high levels of L. minutus in subgingival flora, none of the 50 SP subjects had a detectable antibody titer, and only four of the HP and JP subjects had detectable antibody. These results indicate that many organisms in the subgingival flora elicit antibody responses. B. gingivalis is probably the best example among the species tested. However, some organisms that are present in high concentration, e.g., L. minutus, apparently fail to induce significant antibody responses.