Reduce Virus Infectivity Research Articles

γ-Interferon is one of several direct B cell-maturing lymphokines

Two classes of molecules often released after the interaction of T lymphocytes, macrophages and antigen are B-cell maturation factors (BMF)1-3 and immune (gamma) interferon (IFN-gamma)4-7. BMFs directly induce the maturation of resting B lymphocytes to the state of active immunoglobulin secretion, while IFN-gamma is defined by the reduction of viral infectivity in vitro. However, interferons have been shown to have a variety of effects and they have also been reported both to increase and decrease B-cell differentiation in intact animals and complex cellular mixtures in vitro. Here we show that murine IFN-gamma produced by recombinant DNA technology shows similar biological effects to BMFs from two other sources. All three preparations induce immunoglobulin secretion by both normal resting murine splenic B cells and the comparable B-cell tumour line WEHI-279.1 (refs 1, 3). IFN-gamma and the other two BMFs are not identical, however, as anti-IFN-gamma antibodies block the effects on B cells of IFN-gamma, but not those of the other two lymphokines. IFN-gamma may be one of several molecules with a direct role in driving the maturation of resting B cells to active immunoglobulin secretion.

Identification by monoclonal antibodies of a new epitope in the glycoprotein complex of sindbis virus

Monoclonal antibodies against a deletion mutant of Sindbis virus were produced and characterized in order to determine the fine mapping and functional activities of single viral epitopes. All monoclonal antibodies so far tested showed a certain degree of reciprocal competition and were directed against an antigenic determinant which was present only on the undissociated complex of the E1 and E2 glycoproteins. A biological assay measuring viral haemagglutination showed no decrease in the titre of viral samples preincubated with monoclonal antibodies. Conversely, a reduction in viral infectivity was demonstrated, particularly with two of these antibodies. The results suggest that the antibodies which we characterized seem to recognize a new epitope which is represented on both glycoproteins on the surface of this mutant of Sindbis virus.

Effect of seed dressing sunnhemp for the prevention of tobacco mosaic virus infection

Abstract Seed soak treatment of sunnhemp (Crotalaria juncea L.) with the systemic pesticides, benomyl, methomyl, phorate and carbofuran, gave protection against infection with tobacco mosaic virus (TMV). These chemicals significantly inhibited infection on sunnhemp plants and reduced virus infectivity, as well as delaying the appearance of systemic symptoms. Benomyl was found to be the most effective chemical.

Persistence of human rhinovirus infectivity under diverse environmental conditions.

The persistence of human rhinovirus type 2 and type 14 infectivity was studied under various laboratory conditions designed to mimic those commonly found in the environment. The effects of temperature, ionic strength, protein content, and evaporation were compared. Both viruses were stable (less than 0.3-log decrease in titer) at 6 and 23 degrees c for 24 h in the liquid state regardless of salt or protein additives; a titer decrease of less than 1.0 log was noted at 37 degrees C. However, evaporation at 37 degrees C reduced virus infectivity by 3.2 to 4.5 logs in buffered water, an effect which could be significantly lessened by the addition of bovine serum albumin in saline (2.0- to 2.9-log decrease in titer). These studies support and extend observations by others that the human rhinoviruses retain sufficient infectivity after drying on hard surfaces to permit their transmission to susceptible persons upon contact.

Effects of cell culture and laboratory conditions on type 2 dengue virus infectivity.

The stability of type 2 dengue virus to exposure to a variety of laboratory conditions was determined. Suckling mouse brain passage virus was adapted for growth in BHK-21 cells, and plaque assays were performed using a tragacanth gum overlay. A three- to fourfold increase in plaque size could be obtained if monolayers were subconfluent at time of inoculation. Incubation of virus for 24 h at 37 degrees C, pH 6.5, or in buffer containing 1 mM ethylenediaminetetraacetate considerably reduced virus infectivity as compared with virus incubated for the same period at 4 degrees C, pH 8.0, or in buffer with or without 1 mM CaCl2 and 1 mM MgCl2. Multiple freezing and thawing of virus tissue culture medium containing 10% fetal calf serum did not reduce virus infectivity.

Survival of Infectious Hematopoietic Necrosis Virus Held Under Various Environmental Conditions

Dehydration of infectious hematopoietic necrosis virus (IHNV) from water at 4 and 10 °C resulted in only partial inactivation, but dehydration from Hanks' balanced salt solution (HBSS) and homogenized fish tissue resulted in total loss of virus infectivity within 7 days. Survival was not affected by pH between 6 and 8, but virus infectivity was significantly reduced at pH 5 and 9. Water hardness from 20 to 250 mg/ℓ (as CaCO3) did not significantly reduce virus infectivity. Salinity distinctly affected IHNV survival: storage in artificial seawater, filtered ocean water, HBSS. and Earle's balanced salt solution (EBSS) equally reduced virus titers. The addition of protein to deionized water and EBSS and HBSE resulted in increased survival. Survival of IHNV was inversely proportional to HBSS concentration and was highest when it was frozen in media supplemented with 10% calf serum. Virus survival was good at −70 and −20 °C, but virus infectivity decreased sharply with an increase of temperature above 4 °C; increasingly poor survival occurred at 15. 21, 28, and 32 °C. Freezing and thawing of IHNV had no effect if the media contained 10% protein; however, freezing in deionized water resulted in a significant loss of virus infectivity. Key words: virology, virus survival, laboratory storage, environmental effects

The effects of UK2054 on the multiplication of influenza viruses.

The isoquinoline compound UK2054 prevents the uptake of influenza virus by susceptible cells. Pre-incubation of virus particles with 500 mug./ml. UK2054 at 37 degrees C. for 2 hr. does not reduce virus infectivity. Host cells vary in their responsiveness to the inhibitory effect of UK2054; virus multiplication is inhibited in chick allantoic cells by lower concentrations than those required to inhibit virus growth in chick embryo fibroblasts. The effectiveness of UK2054 is reduced by the presence of serum.It is concluded that inhibition of influenza virus multiplication by UK2054 might result from interaction of the inhibitor with both virus and cells. Any direct combination between inhibitor and virus is completely reversible.

Effects of Lindane and Carbaryl on Insects, Soil and Plant Nitrogen, and Grain Yield of Rice

SummaryExperiments were conducted during three crop seasons to determine the effects of lindane and carbary1, applied to the irrigation water or incorporated in the soil, on the control of insects, on the nitrogen status of the soil and plant, and on grain yield of lowland rice. In two crop seasons the highest grain yield was obtained from three applications of lindane to the irrigation water and carbaryl sprays at 7- to 10-day intervals, and in the third season from 20 kg/ha. carbaryl incorporated in the soil without any lindane treatment or carbaryl spray. In two seasons, soil-incorporated carbaryl at 20 kg/ha. active ingredient gave a significantly higher yield than the no-insecticide control, and in one season the increase in grain yield was just below the significant level. Most of the grain yield increase with 20 kg/ha. carbaryl incorporated into the soil was caused by better control of stem borer and leafhopper and a significant reduction in virus infection.

Separation of a highly active antiviral factor from virus-infected plants

An antiviral factor (AVF), which occurs in plants infected with tobacco mosaic virus, was separated by means of column chromatography. This inhibitor was eluted from diethylaminoethylcellulose by 0.56–0.58 M NaCl. At this concentration antiviral material was not eluted when extracts of healthy plants were used. This AVF is very active in reducing virus infectivity even at extremely low concentrations. Rough calculations indicated that the procedure of fractionation followed in this work, resulted in an increase of about 5000 times in AVF activity per unit protein, as compared to the starting material.

A SIMPLE PATTERN METHOD FOR THE SERUM NEUTRALIZATION TEST WITH HERPES SIMPLEX VIRUS IN CHICK EMBRYO MONOLAYERS.

A simple method for the serum neutralization with herpes simplex virus was developed utilizing the ability of this virus to form plaques in chick embryo monolayers. A constant virus-varying serum system was adopted. The new device was the use of eight small agar cover slips (ACS), prepared by punching out of a solidified thin layer of an agar overlay solution, for inoculation of virus-serum mixtures onto a monolayer dish, so that each serum sample could be titrated on one monolayer dish. Reduction of virus infectivity was evidenced by changes in the pattern from confluent to negative or a small number of scattered plaques. When a certain dilution of seed virus was used constantly, a fairly high reproducibility of serum endpoints was demonstrated, which were comparable to those obtained by other routine neutralization methods. Serum samples from 39 normal healthy persons were tested by this method and by complement fixation tests, and the serum endpoints obtained by the two tests showed a good parallelism.