Increased multiplication of dengue virus in mouse peritoneal macrophage cultures by treatment with extracts of Ascaris-Parascaris parasites.

Methylcellulose-elicited peritoneal macrophages from BALB/c mice were cultivated in vitro and inoculated with dengue virus (DV). At intervals thereafter portions of the culture fluids were taken and titrated for viral infectivity. Extracts from Ascaris suum and Parascaris equorum, either crude or Sephadex G-100 fractionated, were examined for effects on the multiplication of DV. The macrophage cultures treated with the above substances produced larger amounts of DV compared with untreated control cultures. The enhancing effect of the substances depended on doses added and duration of treatment and was suppressed by co-treatment with carrageenan, a specific macrophage-inhibiting agent, but was not related to the viability of cultured cells. In fluorescent antibody (FA) as well as infectious center assay experiments, it was shown that the DV-infected cells were found more frequently in treated cultures than in untreated control cultures. In the treated cultures phagocytosis by cultured cells was also of a higher magnitude than that in untreated cultures. In cocultures of macrophages and splenocytes from the same line of mice, no additive effect of splenocytes was noted. The limulus amebocyte lysate clotting enzyme reaction (Limulus test) indicated that involvement of bacterial lipopolysaccharides in the enhancement phenomena was negligible. The data so far obtained suggest that the enhancing effect was due to direct action of the parasitic extracts on macrophages. Four Sephadex G-100 fractions from the crude extracts showed similar activities; however, the effects of fractions I and III appeared to be comparatively strong. Significance of the findings in relation to the pathogenesis of DV infection was discussed.

Antibody-mediated enhancement of dengue virus infection in mouse macrophage cell lines, Mk1 and Mm1.

Antibody-mediated enhancement of dengue type 2 virus (D2V) replication in murine macrophage cell lines (Mk1 and Mm1) was studied. While both Mk1 and Mm1 supported D2V replication in the absence of enhancing antibodies, virus production was enhanced when both cell lines were inoculated with D2V in the presence of dengue type 1 virus (D1V)-hyperimmune rabbit IgG, D1V-hyperimmune mouse ascitic fluids, or D2V-hyperimmune mouse ascitic fluids at subneutralizing concentrations. The enhancement ratios were greater in Mk1 than in Mm1. Type-specific neutralizing monoclonal anti-D2V antibody also mediated D2V replication enhancement in Mk1 to the same extent as mediated by three other enhancing antibodies described above. In contrast, however, the same monoclonal antibody mediated only a slight and smaller magnitude of D2V replication enhancement in Mm1 than did the other enhancing antibodies. Fluorescent antibody observations revealed that virus replication enhancement in both Mk1 and Mm1 was due primarily to an increase in the numbers of virus-infected cells. D2V infection enhancement in Mk1 by the anti-D2V mouse ascitic fluids at a dilution showing nearly 50% plaque-reduction activity was markedly suppressed by addition of complement to the inocula, whereas that by the monoclonal antibody, which has been identified as mouse IgG1, was not. Phagocytoses of tritiated thymidine-labeled bacteria by Mk1 and Mm1 were also enhanced when the bacteria had been opsonized with antibody. The phagocytosis enhancement ratios were again greater in Mk1 than in Mm1.

Dengue type 2 virus infection in human peripheral blood monocyte cultures.

Dengue type 2 virus (D2V) infection in cultured human monocytes was studied. D2V permissiveness of the monocytes was enhanced when the cells were inoculated with D2V in the presence of either polyclonal or type-specific monoclonal anti-dengue antibody. The enhancement of D2V permissiveness mediated by the antibodies was more clearly demonstrated when the monocytes had been treated with trypsin before virus inoculation, though treatment of the cells with trypsin alone decreased D2V permissiveness. The enhancement of infection by type-specific neutralizing monoclonal antibody suggests that the D2V particles possess at least two antigenic determinants closely associated with virus infectivity. Infectious center assays revealed that the infection enhancement in the presence of the antibodies was due primarily to an increase in the number of D2V-infected cells, and that only a small proportion of the monocyte population supported D2V replication. The virus-permissive monocytes did not bear HLA-DR antigens on their cell surface. The presence of nonadherent lymphocytes in the monocyte cultures before D2V inoculation did not affect the D2V permissiveness of the monocytes. Treatment of cultured monocytes with the synthetic adjuvants N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and its lipophilic derivative, [B30]-MDP, did not significantly affect the D2V permissiveness of the cells.

An oral electrolyte solution (Pedialyte) in the treatment of acute infantile gastroenteritis.

PIP: During a 3-month period, 35 pediatric patients with infantile acute gastroenteritis were treated with a premixed oral glucose electrolyte solution. The study group consisted of 17 boys and 18 girls with a mean age of 12.4 months (range of 5.5-20 months). 13 patients (37%) had mild dehydration, 16 (46%) had moderate dehydration, and 6 (17%) had normal hydration. 29 (83%( had isotonic dehydration and only 6 (17%) presented with hypotonic dehydration. Almost all of the patients were admitted for a hospital stay of 3 days and on discharge, all were in good condition. None developed severe dehydration or needed intravenous fluid treatment. The mean weight gain during hospitalization was 147 gm with a range of 100-400 gm. Unexpectedly, pathogenic bacteria organisms were discovered in 24 (68.7%) of the total cases, but all the children recovered very well with the oral electrolyte solution only without the need for antibiotics. From clinical, chemical, and other observations, it could be concluded that this ready-to-feed oral electrolyte solution can be used safely and effectively for the treatment of acute infantile gastroenteritis both with or without mild or moderate dehydration. No complications were observed in this study.^ieng