IntroductionA progressive reduction in CD4 ϩ T-helper lymphocytes is the main feature of HIV infection and leads to a depression in adaptive immunity. 1 Innate immunity is also important in the host response to HIV infection and can be impaired during the course of this infection. Dendritic cells (DCs) can promote HIV transmission, [2][3][4][5] and DC function 6 and number 7 decline with HIV infection. The effector functions of monocytes and macrophages, including phagocytosis and intracellular oxidative responses, can be found decreased in HIV-infected subjects 8,9 and in cultured cells in the presence of HIV. [10][11][12][13] Superoxide production by neutrophils 14 as well as natural killer cell function as measured by the lymphokineactivated killer activity and responsiveness to interferon-␣ (IFN-␣) 15,16 have been shown to be defective in HIV-infected subjects.An important part of the innate defense against virus is the production of the type I IFNs, IFN-␣, and IFN-␤. 17 IFN-␣/␤ not only directly inhibit HIV replication, 18-20 but also have important adjuvant effects on a variety of immune cell types, such as monocytes, natural killer cells, 21 and T cells. [22][23][24][25][26] The in vitro type I IFN production by total peripheral blood mononuclear cells (PBMCs) was shown to be impaired during the course of HIV infection, and this impairment was associated with the occurrence of opportunistic infections. 27,28 CD4 ϩ CD11c Ϫ lineage marker Ϫ type 2 DC precursors (pre-DC2) were recently shown to be the natural IFN-␣/␤-producing cells in human blood. 29,30 IPCs produce up to 1000 times more IFN-␣ than any other blood cell type in response to viral stimulation. 29 Whether this impairment of IFN-␣/␤ production in HIV-infected individuals is due to a functional defect or to a reduction in number of IPCs is not known.In this study, we show that blood IPCs are severely decreased in AIDS patients but increased in asymptomatic long-term survivors (LTSs). The drop in IPC number and a decrease in their induced IFN production are associated with the presence of opportunistic infections and active Kaposi sarcoma. Our findings bring a new insight into the physiopathology of HIV infection and identify the IPC count as a new parameter to monitor the status of the immune system of HIV-infected subjects. Patients, materials, and methods HIV-infected subjectsFifty-four HIV-infected subjects were recruited from 3 centers: the University of California at San Francisco (UCSF), the San Francisco General Hospital, and the Hospices Civils de Lyon, France. This study was approved by the Committee for Human Research, UCSF. Subjects were enrolled consecutively, and the only inclusion criterion was a confirmed HIVpositive serology and a written informed consent. The following conditions, which can nonspecifically affect blood cell counts, were used as exclusion criteria: previous cytotoxic chemotherapy, splenectomy, hypersplenism, and blood transfusion within the past 4 weeks. After inclusion, a full medical history was taken and physic...

Drug allergic reactions presenting as maculo-papular exanthema (MPE) are mediated by drug-specific T cells. In this study, the frequency of circulating specific T cells was analyzed by interferon-gamma (IFN-gamma) enzyme-linked immunospot assay in 22 patients with an allergic MPE to amoxicillin (amox). Amox-specific circulating T cells were detected in 20/22 patients with frequencies ranging from 1 : 8000 to 1 : 30 000 circulating leucocytes. No reactivity was observed in 46 control patients, including 15 patients with immunoglobulin E-mediated allergy to amoxicillin, 11 patients with a history of drug-induced MPE but tolerant to amoxicillin and 20 healthy individuals. Furthermore, amox-specific T cells were still detectable several years after the occurrence of the allergic reaction even after strict drug avoidance. Finally, analysis of drug-specific T cells in one patient allergic to ticarcillin (a penicillin antibiotic distinct from amox) revealed the presence of IFN-gamma-producing T cells reactive to ticarcillin and several other betalactam antibiotics, suggesting that the IFN-gamma ELISPOT assay is able to detect T cell cross-reactivity against chemically related drugs. These findings confirm that drug-induced MPE is associated with the presence of specific T cells in blood and further suggest that the IFN-gamma ELISPOT is a sensitive assay which could improve the diagnosis of betalactam allergy.

To test the hypothesis that the Staphylococcus aureus enterotoxin gene cluster (egc) can generate new enterotoxin genes by recombination, we analyzed the egc locus in a broad panel of 666 clinical isolates of S. aureus. egc was present in 63% of isolates, confirming its high prevalence. The archetypal organization of the egc locus, consisting of five enterotoxin genes plus two pseudogenes, was found in 409 of 421 egc-positive strains. The egc locus was incomplete in a few strains and occasionally harbored an insertion sequence and transposase genes. These strains may represent evolutionary intermediates of the egc locus. One strain with an atypical egc locus produced two new enterotoxins, designated SElV and SElU2, generated by (i) recombination between selm and sei, producing selv, and (ii) a limited deletion in the ent1-ent2 pseudogenes, producing selu2. Recombinant SElV and SElU2 had superantigen activity, as they specifically activated the T-cell families V␤ 6, V␤ 18, and V␤ 21 (SElV) and V␤ 13.2 and V␤ 14 (SElU2). Immunoscope analysis showed a Gaussian CDR3 size distribution of T-cell receptor V␤ chain junctional transcripts of expanded V␤ subsets in toxin-stimulated cultures, reflecting a high level of polyclonality. These data show that egc is indeed capable of generating new superantigen genes through recombination.Staphylococcus aureus produces a large variety of exotoxins, including staphylococcal enterotoxins A to E (SEA to SEE), SEG to SER, and SEU; staphylococcal enterotoxin-like toxins (SEls); and toxic shock syndrome (TSS) toxin-1 (5, 23). These toxins are responsible for specific acute clinical syndromes such as TSS (due to both TSS toxin-1 SEs and SEls), food poisoning (due to SEs), and staphylococcal scarlet fever (considered a mild form of TSS) (10,26,34).All these toxins share certain structural and biological properties, suggesting that they derive from a common ancestor (16,21). They exhibit superantigen activity, stimulating polyclonal T-cell proliferation through coligation between major histocompatibility complex class II molecules on antigen-presenting cells (APC) and the variable portion of the T-cell antigen receptor ␤ chain or ␣ chain (TCR V␤ and TCR V␣, respectively), with no need for prior APC processing (4,13,21,22,37,39). The pattern of V␤/V␣ activation is specific to each superantigen (4, 12). T-cell/APC activation by these toxins leads to the release of various cytokines/lymphokines and interferon, enhances endotoxic shock, and causes T-and B-cell immunosuppression, all of which may undermine the immune response against bacterial infection (5, 10, 25).All the genes encoding these toxins are harbored by mobile elements, including bacteriophages, pathogenicity islands, genomic islands, and plasmids (10,20,28,36). Only the enterotoxin gene cluster (egc) is organized as an operon, consisting of two enterotoxin genes (seg and sei), three enterotoxinlike genes with proven superantigenic activity but not emetic properties (selo, selm and seln), and two pseudogenes (ent1 and -2). This ...

Panton Valentine leukocidin (PVL) may be responsible for pulmonary necrosis in necrotizing Staphylococcus aureus pneumonia, a highly lethal infection. Commercial intravenous immunoglobulin (IVIg) preparations containing antibodies against PVL might have therapeutic value in this setting, as an adjunct to antimicrobial chemotherapy. To test this possibility, we determined anti-PVL antibody titers in commercial IVIg and the capacity of IVIg to prevent the cytopathic effects of PVL in vitro. Specific enzyme-linked immunosorbent assays based on purified recombinant PVL (rPVL) showed that IVIg contained specific anti-PVL antibodies. The cytotoxicity of rPVL and of crude culture supernatants of PVL-producing S. aureus strains were investigated by measuring ethidium-bromide incorporation by polymorphonuclear neutrophils (PMNs) in flow cytometric assays, as well as PMN ultrastructural changes by transmission electron microscopy. IVIg was found to neutralize pore formation and the cytopathic effect of both rPVL and S. aureus culture supernatants.

We investigated the involvement of the recently described staphylococcal enterotoxins G and I in toxic shock syndrome. We reexamined Staphylococcus aureus strains isolated from patients with menstrual and nonmenstrual toxic shock syndrome (nine cases) or staphylococcal scarlet fever (three cases). These strains were selected because they produced none of the toxins known to be involved in these syndromes (toxic shock syndrome toxin 1 and enterotoxins A, B, C, and D), enterotoxin E or H, or exfoliative toxin A or B, despite the fact that superantigenic toxins were detected in a CD69-specific flow cytometry assay measuring T-cell activation. Sets of primers specific to the enterotoxin G and I genes (seg andsei, respectively) were designed and used for PCR amplification. All of the strains were positive for seg andsei. Sequence analysis confirmed that the PCR products, corresponded to the target genes. We suggest that staphylococcal enterotoxins G and I may be capable of causing human staphylococcal toxic shock syndrome and staphylococcal scarlet fever.

Present serological methods differentiate poorly between acute and chronic toxoplasmosis in pregnant women, particularly when immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies to Toxoplasma gondii are present simultaneously. In the present study, a simple test for discriminating between high-avidity antibodies, which are usually present in chronic infections, and low-avidity antibodies, typical of acute infection, was evaluated. Sera were evaluated for Toxoplasma gondii antibodies using a commercial enzyme immunoassay, but a duplicate well was washed in 6M urea to disrupt low-avidity complexes. Results are expressed as the percentage of antibodies resisting elution by urea. Equivocal sera (n = 493) containing both IgG and IgM Toxoplasma gondii antibodies from 309 pregnant women whose status as chronically or acutely infected had been independently determined using standard methods were evaluated for antibody avidity. A value of > 35% elution-resistant antibodies was always associated with chronic infection and could absolutely exclude a recent (< 3 months) infectious incident. Values of < 35% require repeat testing four weeks later to confirm the patient's status, since a proportion of individuals with chronic toxoplasmosis maintain low-avidity antibodies over long periods. This inexpensive, simple method can provide reassurance to clearly chronically infected individuals and avoids the need for repeated testing in these cases.

The parasite Toxoplasma gondii can infect most mammals and birds, sometimes causing severe pathology. Primary infection during pregnancy can result in abortion or fetal defects. Host immunity, particularly cellular immunity towards antigenic peptides, can control infection, but an efficient vaccine is not yet available. We have evaluated T-cell responses to a crude soluble toxoplasma antigen (ST-Ag) and to five recombinant peptide antigens of cells in whole-blood cultures from 22 pregnant women with preexisting infections and from 7 pregnant negative controls. Cells from all infected patients but from none of the controls responded specifically to ST-Ag by expressing surface CD25 on culture. Responses to the recombinant antigens showed considerable variation between individuals. rGRA1 elicited a response in 16 of the 22 samples (73%), rSAG1 in 13, rGRA7 in 9, rGRA6-CT in 4, and rGRA6-NT in only 1. Most responding cells were CD4؉ . Cells from infected subjects cultured with ST-Ag all released high levels of gamma interferon (IFN-␥) into the culture supernatant (4,343 ؎ 2,536 pg/ml). Cells from 12 patients released IFN-␥ after culture with rGRA1 (130 ؎ 98 pg/ml), those from 10 patients released it after culture with rSAG1 (183 ؎ 128 pg/ml), and those from 4 patients released it after culture with rGRA7 (324 ؎ 374 pg/ml). Intensity of IFN-␥ production in response to the latter two recombinant antigens correlated with responses to ST-Ag (r ‫؍‬ 0.61 and 0.53, respectively; P < 0.01). Interleukin-4 was always absent from supernatants of cells stimulated with toxoplasma antigens. The heterogeneity of human responses to individual recombinant toxoplasma antigens should be considered in the design of potential vaccines.The protozoan parasite Toxoplasma gondii infests a wide range of mammalian hosts and some birds, usually with few pathological consequences. Human infestation is widespread and originates mainly, but not only, with cats. Incidence varies widely between geographical sites, but disease is rare, except in immunodepressed individuals and, especially, as a result of congenital infection. Cellular immunity provides an essential component of protection against T. gondii, and J. K. Frenkel (reviewed by Darcy and Santoro [2]) first demonstrated the key role played by T lymphocytes. Infection during pregnancy, especially during the third trimester, carries a high risk of mother-to-fetus transmission with severe consequences for the child. Immunocompetent mothers infected before pregnancy do not pass the parasite to their offspring in utero, even if reexposure to the parasite occurs during the critical period. The crucial T-cell responses to T. gondii may be measured (10), and we have recently determined that cytofluorimetric detection of CD25 expression after stimulation of whole-blood cultures with T. gondii antigen for 7 days is a sensitive and specific test, comparable to the 3 H-thymidine incorporation assay (5). The assay, which uses a crude soluble T. gondii antigen preparation (ST-Ag), was found to be useful ...

Background: Quinolone hypersensitivity reactions are being more frequently reported. Skin tests in investigations of patients are known to not be fully reliable. The provocation test thus remains the gold standard in the definitive diagnosis of allergy, despite the risks involved. The aim of this study was to evaluate basophil activation tests (BATs) in the diagnosis of immediate-type reactions to quinolones. Methods: Thirty-four patients who presented an immediate-type hypersensivity reaction less than an hour after quinolone administration were studied. The allergologic workup of these patients consisted of a careful clinical history, a skin test and a BAT with the culprit quinolone. If not contraindicated, and in the case of high probability of a nonallergic reaction, provocation tests were performed to assess the nonimmunologic nature of the hypersensitivity. Results: Among the 34 patients studied, 17 (50%) presented a negative BAT to the suspected quinolone, while the other 17 (50%) patients presented a positive BAT for quinolone at the time of their reaction. Among the 17 patients with negative BATs, 15 (2 of whom had had positive skin tests) had quinolone successfully reintroduced. Conclusions: Our report suggests that the BAT, if negative for the culprit quinolone, is a valuable tool in the decision whether or not to perform provocation tests in patients with a history of immediate-type reaction to quinolones, in order to exclude an allergic reaction.