A significant number of human immunodeficiency virus epitope-specific cytotoxic T lymphocytes detected by tetramer binding do not produce gamma interferon.

Despite the seemingly important role of cytotoxic T-lymphocyte (CTL) responses in human immunodeficiency virus (HIV) disease pathogenesis, their measurement has relied on a variety of different techniques. We utilized three separate methodologies for the detection of CTLs in a cohort of HIV-infected individuals who were also human leukocyte antigen A2 (HLA-A2) positive. Among the different CTL assays, a correlation was seen only when the Gag epitope-specific HLA A*0201-restricted tetramer assay was compared with the ELISPOT assay performed after stimulation with the Gag epitope; however, this correlation was of borderline statistical significance. On average, the tetramer reagent detected a 10-fold-higher number of cells than were seen to produce gamma interferon by the ELISPOT assay. The implications of this CTL assay comparison and the possibility of phenotypic differences in HIV-specific CD8(+) T lymphocytes are discussed.

Characterization of the R572T point mutant of a putative cleavage site in human foamy virus Env.

A putative cleavage site of the human foamy virus (HFV) envelope glycoprotein (Env) was altered. Transient env expression revealed that the R572T mutant Env was normally expressed and modified by asparagine-linked oligosaccharide chains. However, this single-amino-acid substitution was sufficient to abolish all detectable cleavage of the gp130 precursor polyprotein. Cell surface biotinylation demonstrated that the uncleaved mutant gp130 was transported to the plasma membrane. The uncleaved mutant protein was incapable of syncytium formation. Glycoprotein-driven virion budding, a unique aspect of HFV assembly, occurred despite the absence of Env cleavage. We then substituted the R572T mutant env into a replication-competent HFV molecular clone. Transfection of the mutant viral DNA into BHK-21 cells followed by viral titration with the FAB (foamy virus-activated beta-galactosidase expression) assay revealed that proteolysis of the HFV Env was essential for viral infectivity. Wild-type HFV Env partially complemented the defective virus phenotype. Taken together, these experimental results established the location of the HFV Env proteolytic site; the effects of cleavage on Env transport, processing, and function; and the importance of Env proteolysis for virus maturation and infectivity.

Salmonella and Shigella species.

Salmonella and Shigella are the second and third most common causes of bacterial food-borne disease in the United States and are a major global health problem. The prevention and treatment of disease caused by these organisms are complicated by the increase in multidrug-resistant strains and the lack of an effective vaccine. This article discusses the epidemiology, clinical features, and diagnostic techniques for both enteric pathogens.

An endoplasmic reticulum retrieval signal partitions human foamy virus maturation to intracytoplasmic membranes.

Among all retroviruses, foamy viruses (FVs) are unique in that they regularly mature at intracytoplasmic membranes. The envelope glycoprotein of FV encodes an endoplasmic reticulum (ER) retrieval signal, the dilysine motif (KKXX), that functions to localize the human FV (HFV) glycoprotein to the ER. This study analyzed the function of the dilysine motif in the context of infectious molecular clones of HFV that encoded mutations in the dilysine motif. Electron microscopy (EM) demonstrated virion budding both intracytoplasmically and at the plasma membrane for the wild-type and mutant viruses. Additionally, mutant viruses retained their infectivity, but viruses lacking the dilysine signal budded at the plasma membrane to a greater extent than did wild-type viruses. Interestingly, this relative increase in budding across the plasma membrane did not increase the overall release of viral particles into cell culture media as measured by protein levels in viral pellets or infectious virus titers. We conclude that the dilysine motif of HFV imposes a partial restriction on the site of viral maturation but is not necessary for viral infectivity.

Utility of Gram's and Giemsa stains in the diagnosis of pulmonary tuberculosis.

Conflicting information in the literature regarding the staining properties of Mycobacterium tuberculosis using Gram's stain and experience in two patients with pulmonary tuberculosis in whom the diagnosis was suspected after staining with non-acid-fast bacillus stains prompted the study of Gram's stain in this disease. The main finding was that mycobacteria appear as refractile, gram-neutral, or faintly gram-positive bacilli after Gram's stain, depending upon the plane of focus in which the organisms are regarded. It is concluded that the diagnosis of mycobacterial disease may be suggested by Giemsa- and Gram-stained smears of clinical specimens. M. tuberculosis may be either gram-neutral or gram-positive.

In-vitro activity of BMY 28142, a new aminothiazolyl cephalosporin.

The in-vitro activity of BMY 28142, a new alpha-methoxyimino aminothiazolyl cephalosporin, was determined by microdilution broth techniques. The agent demonstrated excellent activity against recent clinical Enterobacteriaceae isolates with a 90% minimum inhibitory concentration (MIC90) of 0.25 mg/l or less for all but one species tested. BMY 28142 inhibited all Pseudomonas aeruginosa strains tested (MIC90 = 8.0 mg/l) as well as most other non-fermentative bacteria studied. Methicillin-susceptible Staphylococcus aureus were susceptible to BMY 28142 with MIC90 = 4.0 mg/l, while methicillin-resistant strains were generally resistant (MIC range 8- greater than 32 mg/l).

Infectious colitis endoscopically simulating inflammatory bowel disease: a prospective evaluation.

This prospective evaluation of patients presenting with mucoid bloody diarrhea and suspected idiopathic inflammatory bowel disease demonstrated a 38% incidence of infectious colitides. The infectious agents detected were Campylobacter, Salmonella, Shigella, Amoeba, and Clostridium difficile. An increased awareness and the utilization of selective culture media should allow the clinician to definitively diagnose patients who present with signs and symptoms suggestive of idiopathic inflammatory bowel disease.