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Phagocytosis of horse erythrocytes treated with equine infectious anemia virus by cultivated horse leukocytes.

Horse erythrocytes treated with equine infectious anemia virus hemagglutinin were phagocytized by cultivated horse leukocytes (mainly macrophage-like cells and partly polymorphonuclear cells) after incubation with fresh horse serum but not with inactivated horse serum. The phagocytosis began as soon as the erythrocytes were added to the leukocyte cultures, and the majority of the reaction proceeded within 30 minutes. Addition of antiserum showed a slightly suppressing but no enhancing effect on the phagocytosis. Phagocytosis seemed to be caused by the recognition of the third complement component on the affected RBC with the receptors on phagocytes, but not by the recognition of immunoglobulin. Since cultivated leukocytes were able to phagocytize erythrocytes which were treated with a quantity as small as 1/16 units of hemagglutinin, and since the hemagglutinin-antibody complex also could bind to erythrocytes and induced them to become phagocytized, the reaction appears to play an important role in the mechanisms of anemia and formation of sideroleukocytes in horses infected with the equine infectious anemia virus.

Animals↗

The effect of ceruloplasmin on the multiplication and on some biological and physico-chemical characteristics of influenza virus A/PR8/34 (H0N1) cultivated on chorioallantoic membrane fragments. Note 1. Kinetics of virus multiplication and of some biological characteristics in the presence and absence of ceruloplasmin.

The presence of ceruloplasmin in the inoculum inhibits the multiplication of influenza virus A/PR8/34 (H0N1) in chorioallantoic membrane fragments. Virus corpuscles that remain uncoupled to ceruloplasmin infect the host cells and their replication results in progens whose properties differ from those of controls inoculated in the absence of ceruloplasmin. The variation in time of the characteristics of the respective virus progens is discussed.

Allantois↗

Comparison of reverse transcription-PCR with tissue culture and other rapid diagnostic assays for detection of type A influenza virus.

We applied a reverse transcription (RT)-PCR assay for influenza A virus to combined nasal wash-throat swab specimens previously obtained from an outpatient pediatric population with acute respiratory illness during concurrent epidemics of influenza A virus and respiratory syncytial virus. The results of the RT-PCR assay were compared with those previously reported with virus cultivation and commercially available rapid diagnostic kits (E.A. Dominguez, L.H. Taber, and R.B. Couch, J. Clin. Microbiol. 31:2286-2290, 1993). With virus cultivation as the "gold standard", the RT-PCR assay had a sensitivity, specificity, and efficiency of 95, 98, and 97%, respectively, compared with 75, 100, and 93%, respectively, for the best diagnostic kit (Becton Dickinson Directigen). RT-PCR is an effective alternative to virus isolation for the detection of influenza A virus in clinical specimens.

Child↗

Combination chemotherapy, a potential strategy for reducing the emergence of drug-resistant influenza A variants.

Rapid development of resistant influenza variants after amantadine treatment is one of the main drawbacks of M2 blockers. On the other hand, the emergence of variants with low susceptibility to the neuraminidase (NA) inhibitors is limited. In the present study we examined whether combination therapy with two classes of anti-influenza drugs can affect the emergence of resistant variants in vitro. We observed that virus yields of human A/Nanchang/1/99 (H1N1), A/Panama/2007/99 (H3N2), and A/Hong Kong/156/97 (H5N1) viruses in MDCK cells were significantly reduced (P<0.005) when the cells were treated with the combination of amantadine and low doses of oseltamivir carboxylate (< or =1microM). After five sequential passages in MDCK cells, the M2 protein of viruses cultivated with amantadine alone mutated at positions V27A and S31N/I. Viruses cultivated with oseltamivir carboxylate (> or =0.001microM) possessed mutations in the hemagglutinin (HA) protein. These variants showed reduced efficiency of binding to sialic acid receptors and decreased sensitivity to NA inhibitor in plaque reduction assay. Importantly, no mutations in the HA, NA, and M2 proteins were detected when the drugs were used in combination. Our results suggest that combination chemotherapy with M2 blocker and NA inhibitor reduced the emergence of drug-resistant influenza variants in vitro. This strategy could be an option for the control of influenza virus infection, and combinations with other novel drugs should be explored.

Acetamides↗

Selection of antigenically distinct variants of influenza C viruses by the host cell.

Five strains of influenza C virus were isolated and passaged in the amniotic sacs of embryonated hens' eggs, or in the HMV-II line of human malignant melanoma cells, and were tested for reactivity with a panel of monoclonal antibodies to the hemagglutinin-esterase (HE) glycoprotein. It was observed with two strains (C/Yamagata/4/88, C/Yamagata/7/88) that the HE of virus passaged in HMV-II cells was antigenically distinguishable from that of virus cultivated in eggs. Virus clones obtained after repeated passages of these two strains in HMV-II cells all showed a significant increase in the ability to replicate in the cell culture compared to clones derived from viruses grown in eggs. No difference was seen, by contrast, in the ability to grow in eggs between HMV-II- and egg-derived virus clones. It was also found that HMV-II-grown viruses but not egg-grown viruses could agglutinate glutaraldehyde-fixed chicken erythrocytes at 23 degrees. These observations, taken together, suggest that isolation and passage of influenza C virus in HMV-II cells sometimes result in selection of antigenically distinct variants which have an advantage in binding to the cell surface receptors. Sequence analyses of the HE genes revealed that compared to egg-grown viruses, HMV-II-adapted variant of the Yamagata/4/88 strain had a single amino acid substitution in the HE molecule at position 283 (Asp----Asn) and that of the Yamagata/7/88 strain had two substitutions at positions 212 (Glu----Lys) and 519 (Asn----Asp).

Animals↗

Cultivation of Tuleniy virus (strain Murman) in vitro.

In vitro culturability of Murman strain of Tuleniy flavivirus isolated recently in the northern regions of the USSR was studied. Stable PS pig kidney line was found suitable as a primary sensitive cell substrate for the isolation, proliferation and serial propagation of the virus. The pronounced pathogenicity of the virus to PS cells permits the testing of its infective activity comparable with i.c. titrations on mice, VNT in vitro and the plaquing technique. PS line is suitable for the demonstration and identification of the virus antigen and/or for the study of reproduction of the virus on cellular level using the technique of immunofluorescence.

Animals↗

African swine fever. V. Cultivation of the virus in primary pig kidney cells.

Six strains of African swine fever (ASF) virus were propagated in culture of primary pig kidney (PK) cells. The course of virus growth was followed by means of the fluorescent antibody staining technique. All 6 strains multiplied in the cultures, and 5 of these eventually showed cytopathic effects leading to cell death. Three of the strains were tested for pathogenicity in pigs at various passage levels. Each showed evidence of modification in virulence after a relatively few passages in PK cells. In one case modified virus produced resistance to challenge with homologous virulent virus. All strains rendered the PK cultures capable of hemadsorption of pig erythrocytes.

Animals↗