Lipopolysaccharide-binding protein and phospholipid transfer protein release lipopolysaccharides from gram-negative bacterial membranes.

Although animals mobilize their innate defenses against gram-negative bacteria when they sense the lipid A moiety of bacterial lipopolysaccharide (LPS), excessive responses to this conserved bacterial molecule can be harmful. Of the known ways for decreasing the stimulatory potency of LPS in blood, the binding and neutralization of LPS by plasma lipoproteins is most prominent. The mechanisms by which host lipoproteins take up the native LPS that is found in bacterial membranes are poorly understood, however, since almost all studies of host-LPS interactions have used purified LPS aggregates. Using native Salmonella enterica serovar Typhimurium outer membrane fragments (blebs) that contained (3)H-labeled lipopolysaccharide (LPS) and (35)S-labeled protein, we found that two human plasma proteins, LPS-binding protein (LBP) and phospholipid transfer protein (PLTP), can extract [(3)H]LPS from bacterial membranes and transfer it to human high-density lipoproteins (HDL). Soluble CD14 (sCD14) did not release LPS from blebs yet could facilitate LBP-mediated LPS transfer to HDL. LBP, but not PLTP, also promoted the activation of human monocytes by bleb-derived LPS. Whereas depleting or neutralizing LBP significantly reduced LPS transfer from blebs to lipoproteins in normal human serum, neutralizing serum PLTP had no demonstrable effect. Of the known lipid transfer proteins, LBP is thus most able to transfer LPS from bacterial membranes to the lipoproteins in normal human serum.

Review article: the management of Giardiasis.

Giardiasis is the intestinal infection resulting from infestation with the human parasite Giardia intestinalis, also called Giardia lamblia. The infection may be asymptomatic or present with a variety of symptoms such as diarrhoea, weight loss, abdominal cramps, and failure to thrive. Giardiasis is most often diagnosed after recent travel or in day care centres. The organism has two stages in its life cycle. It is usually ingested as a cyst with as few as 10-25 cysts being sufficient to cause infection. After excystation, the organism is a replicative trophozoite which may attach to the small bowel wall. Giardia intestinalis does not invade the bowel wall. Trophozoites may encyst and be shed in faeces for future ingestion by another host. Diagnosis of infection is by stool examination which may also eliminate other possible infectious agents. Small bowel biopsy may be necessary in difficult individual cases or to rule out non-infectious illnesses, and stool ELISA may serve for large population screening examinations. The mainstay of treatment is metronidazole 250-400 mg three times per day by mouth for 5 days.

Detection of cytomegalovirus in liver transplant biopsies. A comparison of light microscopy, immunohistochemistry, duplex PCR and nested PCR.

The polymerase chain reaction was used to detect cytomegalovirus (CMV) in 91 formalin-fixed paraffin-embedded needle biopsies from 38 liver transplant patients with allograft dysfunction. Thirty donor liver biopsies served as negative controls. PCR results were compared with light microscopy (LM), immunohistochemical staining (IH) for CMV early and late antigen, and clinical data. Primers to the major immediate early gene (MIE) and the viral DNA polymerase gene were duplex amplified. PCR product was reamplified with a nested primer set for the MIE and confirmed by electrophoretic mobilities and dot blotting. Primers for human beta-hemoglobin were used as internal controls. Seventeen of 38 patients had clinical evidence of cytomegalovirus disease, 12 of these were IH-positive, 14 were LM-positive, 15 were duplex PCR-positive and 17 were nested PCR-positive. In addition, duplex PCR was positive in one patient without other evidence of CMV disease, while nested PCR was positive in 12 such patients. The sensitivity and negative predictive value of nested PCR was 100%--however, the specificities and positive predictive values were only 42.9 and 58.6%, respectively. The control group was completely negative by LM, IH, and duplex PCR, however, 6 of 30 patients were nested PCR-positive. The number of nested-positive, duplex-negative patients without CMV disease was significantly greater in the transplant group versus the control group (12/21 vs. 6/30, P < 0.009). The incidence of IgG seropositivity was also significantly greater in the transplant group versus the controls (29/32 vs. 15/24, P < 0.02). We conclude that nested PCR may be an overly sensitive technique for the detection of clinically relevant CMV disease. A negative nested PCR assay for CMV may, however, help rule-out symptomatic CMV infection in an individual case. Duplex PCR showed little advantage over LM, while IH was confirmatory but did not add any new information in this study.

Evaluation of celiac disease biopsies for adenovirus 12 DNA using a multiplex polymerase chain reaction.

It has been postulated that celiac disease (CD) is initiated by adenovirus 12 infection (1). To test this hypothesis, we devised a PCR-based strategy to simultaneously screen for adenovirus 12 (Ad12), cytomegalovirus (CMV), and herpes simplex viruses (HSV) 1 and 2 in formalin-fixed paraffin-embedded small bowel biopsies from adult and childhood CD patients. Control groups consisted of small bowel biopsies from normal adults and children, adults with active peptic duodenitis, and children with active duodenitis. Ad12 DNA was found in two of 19 adult CD biopsies (two of 14 patients), while CMV and HSV DNA was found in one of the 19 adult CD biopsies. Ad12 and CMV DNA was not present in 19 child CD biopsies, while HSV DNA was found in two of these same biopsies. CMV and HSV DNA were not found in any of the control group patients. Ad12, CMV, and HSV DNA were not identified in significant numbers in any patient group. These findings argue against the presence of persistent adenovirus infection in CD patients but do not preclude remote Ad12 infection prior to the onset of CD. Similarly, the absence of CMV and HSV DNA in CD, active peptic disease in adults, and active duodenitis in children suggests that neither virus is involved in the persistence of these inflammatory conditions.