Detection of HIV-Gag p24-Specific Antibodies in Sera and Saliva of HIV-1-Infected Adults and in Sera of Infants Born to HIV-1-Infected Mothers

Secretory immunoglobulin A (IgA) is known to play an important role in the mucosal defense against a variety of pathogens. Although the role of IgA antibodies during sexual transmission of HIV is not clear, HIV-specific IgA antibodies have been detected in various mucosal secretions of HIV-infected individuals. Using a monoclonal antibody against human IgA, we established an ELISA system to detect anti-HIV p24 IgA antibodies in sera and saliva. We have analyzed the levels of anti-HIV p24 IgG and IgA antibodies in sera and saliva of 107 and 119 adults, respectively, with HIV infection at different clinical stages, and in the sera of 13 infants born to HIV-infected mothers. The level of anti-HIV p24 IgA antibodies was lower in sera and higher in saliva as compared to that of anti-HIV p24 IgG antibodies. Where the percentage of HIV-specific serum antibody-positive cases decreased with disease progression, that of saliva antibody-positive cases increased in AIDS patients. Among the 13 infants born to HIV-infected mothers, 7 infants were HIV-p24-specific serum IgA positive. These sera were negative for anti-HIV p24 secretory IgA, suggesting that some infants develop their own immune responses against HIV infection. Thus, the detection of HIV-specific IgA antibodies, especially in saliva, could be a simple and reliable test for the diagnosis of HIV infection.     

Glucose-6-phosphate dehydrogenase cytochemistry using a copper ferrocyanide method and its application to rapidly frozen cells

We describe an improved copper ferrocyanide-based method for cytochemical detection of glucose-6-phosphate dehydrogenase (G6PD), which was used to localize the enzyme within the ultrastructure of rat hepatocytes and adrenocortical cells. With this method, glutaraldehyde fixation and the addition of exogenous electron carriers (for example, phenazine methosulfate) to the cytochemical reaction medium were essential. Copper ferrocyanide reaction product showing the distribution of G6PD was readily recognized at the light microscopic level as Hatchett’s brown staining and at the electron microscopic level as electron-dense deposits. Within stained regions, enzyme cytochemical G6PD activity was found to be associated with ribosome-like structures. Because G6PD is a soluble, cytosolic enzyme, its displacement or extraction may occur during conventional fixation. We, therefore, combined a rapid-freezing technique with G6PD enzyme cytochemistry. The resultant rapid-freezing enzyme cytochemistry enabled us to show the subcellular distribution of G6PD in a more life-like state; the localization of G6PD in rapidly frozen cells was in substantial agreement with that in conventionally fixed cells. Accepted: 14 July 1999     

Akt is an endogenous inhibitor toward tumor necrosis factor-related apoptosis inducing ligand-mediated apoptosis in rheumatoid synovial cells

Akt is known to be activated in the rheumatoid synovial tissues. We examined here functional role of Akt during tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis in rheumatoid synovial cells. Rheumatoid synovial cells in vitro were rapidly committed to apoptosis in response to TRAIL in mitochondria-dependent manner whereas Akt and extracellular signal-regulated kinase (ERK) were also phosphorylated. TRAIL-mediated apoptosis in synovial cells was significantly increased through inactivation of Akt by LY294002, however, that process was not so changed by adding ERK inhibitor, PD98059. Platelet-derived growth factor (PDGF) clearly phosphorylated both Akt and ERK in synovial cells, and PDGF pretreatment markedly suppressed TRAIL-mediated synovial cell apoptosis. The use of not PD98059 but LY294002 abrogated PDGF-mediated inhibitory effect toward TRAIL-induced apoptosis in synovial cells. The above protective effect of Akt was confirmed by the use of short interfering RNA (siRNA)-directed inhibition of Akt. Our data suggest that Akt is an endogenous inhibitor during TRAIL-mediated synovial cell apoptotic pathway, which may explain that synovial cells in situ of the rheumatoid synovial tissues are resistant toward apoptotic cell death in spite of death receptor expression.     

Identification of amino acid residues of influenza A virus H3 HA contributing to the recognition of molecular species of sialic acid

To identify a determinant of human H3 hemagglutinin (HA) amino acid residues linked to the recognition of molecular species of sialic acid, we generated six mutant viruses possessing either the wild-type HA gene from A/Memphis/1/71 (H3N2) or a genetically single-mutated HA gene at position 137, 144, 155, 158 or 193 from a genetic backbone of A/WSN/33 (H1N1) by reverse genetics. We evaluated the binding ability with four types of synthetic sialylglycolipids. The results indicate that the amino acid substitutions Thr155 to Tyr and Glu158 to Gly in H3 HA facilitate virus binding to N-glycolylneuraminic acid.