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Biomedical subjects

C Wallis

Publications and source records attributed to C Wallis.

At least 145 records · Page 8Linked to original sources
PubMed1970

Virus isolations from sewage and from a stream receiving effluents of sewage treatment plants.

In order to detect viruses in sewage or streams, it is first necessary to concentrate the virus present in the fluid sample. Available methods are not readily manageable for concentrating virus from large volumes of fluid, and have not always yielded high recovery rates. In the study described in this paper, a method for concentration of viruses by adsorption on insoluble cross-linked maleic anhydride polyelectrolytes has been utilized to survey the viral flora of sewage and of a stream receiving sewage effluents, in a residential area of Houston, Texas. On a single day the virus flow at different points along the stream varied from 304 000 to 6 014 000 PFU/min. From 84 samples each of 1 US gal, 14 520 isolates were obtained, chiefly echovirus type 7 and polioviruses of all 3 types, some of them with characteristics of virulent wild strains. With virus isolation rates as high as those achieved, it is now possible to monitor virus in natural waters more effectively.

Enterovirus B, Human↗
PubMed1969

Concentration of viruses from sewage and excreta on insoluble polyelectrolytes.

The concentration of viruses from sewage by adsorption on and elution from an insoluble cross-linked copolymer of maleic anhydride is described. Viruses either added to sewage or naturally contained in sewage were preferentially adsorbed to this polyelectrolyte at a pH range of 5.0 to 6.0 and were eluted at pH 8.0 to 9.0. In a 2-month survey of viruses in sewage in the spring (April to May 1968), when viruses are at low levels, efficient and economical detection of these agents was accomplished with the polyelectrolyte-concentration method. This method lends itself to the detection of viruses present in minute amounts in fecal samples, urine, sewage, and other natural waters. Large volumes of these fluids can be treated with the polymer described, and virus can be concentrated sufficiently for detection.

Adsorption↗
PubMed1968

Efficient filtration and sizing of viruses with membrane filters.

Untreated membrane filters retain viruses by adsorption, as well as by physical restriction which occurs when the pore diameter of the filter is smaller than that of the virus particle. As originally recommended by Elford, membranes had to be pretreated with proteinaceous material to preclude virus adsorption. However, coating materials that prevent adsorption of certain viruses do not necessarily prevent adsorption of other viruses. In contrast to proteins, salts enhance virus adsorption. Viruses treated with sodium lauryl sulfate to reduce the surface tension, or purified viruses in distilled water, are not adsorbed to membranes. A procedure is recommended by which viruses may be passed through membranes with a porosity twice the diameter of the virus. Such filtrates, which contain 50 to 100% of the initial virus concentration, should be used for sizing viruses by subsequent filtration through smaller pores. The determination of virus size would then be based on the major population of particles in the virus suspension. In the past, as little as 0.1 to 0.001% of the initial virus population was the basis for size determination, because more than 99.9% of the virus was often lost by adsorption to membranes during the clarifying procedures.

Adsorption↗
PubMed1968

Mechanism of enhancement of virus plaques by cationic polymers.

It has been assumed that plaque enhancement by cationic polymers is due to their binding of sulfated polysaccharides in agar. However, viruses that are enhanced by cationic polymers, diethylaminoethyl-dextran, and protamine were found not to be inhibited by polyanions in agar under the usual overlay conditions. In the case of adenovirus, enhancement by protamine seems to be due to the protamine serving as a source of arginine; enzymes released from the cultured cells digest the protamine and provide a reservoir of arginine for the cells. Other viruses (herpes and echovirus types 3, 4, 5, and 6) known to be susceptible to agar inhibitors were found to be enhanced by cationic polymers even under starch gel and methylcellulose overlays, which are free of polyanions. Since cationic polymers enhance the diffusion of virus through agar or starch gel, plaque enhancement seems to be the result of the gel becoming positively charged so that viruses can move effectively through them. The observation that starch gel and methylcellulose enhance plaque formation with viruses known to be inhibited under agar was also reinvestigated. When the consistency of the agar gel was reduced to the same viscosity of starch gel and methylcellulose overlays, the same plaque counts and sizes were observed under all three overlays.

Adenoviridae↗
PubMed1967

Concentration of enteroviruses on membrane filters.

Enteroviruses can be made to adsorb or to pass through membrane filters by manipulation of the suspending medium. Salts facilitate virus adsorption, but membrane-coating components (MCC) interfere. Because cells release MCC into the culture medium during viral growth, MCC must be removed before virus can be adsorbed to membranes. Adsorbed virus can be eluted with diluents containing MCC (cell extracts or serum) or agents that reduce surface tension (sodium lauryl sulfate). By membrane adsorption and elution, enteroviruses can be readily concentrated and quantitatively recovered from crude virus harvests.

Adsorption↗
PubMed1967

Virus aggregation as the cause of the non-neutralizable persistent fraction.

The non-neutralizable or persistent fraction of virus populations has been found to be caused by aggregated virus. Detailed investigation was performed with the prototype strain of echovirus type 4 (Pesascek), as this virus is notorious for its large non-neutralizable fraction. When Pesascek virus was clarified by low-speed centrifugation, homologous antiserum hardly neutralized the virus. However, when the virus was filtered through membranes having a porosity only twice the diameter of the virus, monodispersed virus was obtained which was efficiently neutralized. Serum titers were up to 1,000 times higher if the neutralization test was carried out with monodispersed virus. Virus in non-neutralizable aggregates was found to constitute 30% of the infective units of unfiltered Pesascek virus but only 0.1% of the antigenically related DuToit strain. This explains why DuToit strain has been a more satisfactory indicator strain for detecting type 4 antibodies, regardless of the echo 4 strain used for inducing the antibodies. Clarified suspensions and ultrafiltrates of viruses belonging to the picorna-, reo-, myxo-, adeno-, herpes-, and poxvirus groups were studied. Clarified suspensions yielded persistent fractions of 0.005% for poliovirus, of 0.1% for reovirus, of 0.6% for influenza virus, of <0.001% for adenovirus, of 0.06% for herpesvirus, and of 10 to 30% for vaccinia virus. In all cases the persistent fractions were removed by membrane filters which had a pore diameter no larger than twice that of the virus under test, and the high concentration of virus in each ultrafiltrate was completely neutralized by antiserum.

Adenoviridae↗
PubMed1967

Concentration of viruses from sewage by adsorption on millipore membranes.

The authors describe a relatively simple membrane-adsorption method for the efficient concentration of viruses from sewage. Sewage, first freed of bacteria by filtration through membranes under conditions that permit virus to pass freely, is then treated with anion resins to remove organic components that adsorb to Millipore membranes and prevent virus adsorption. The salt concentration of the resin filtrates is increased with MgCl(2) to enhance virus adsorption to membranes. The sewage is next adsorbed to a Millipore membrane, from which virus is readily recovered by homogenization in small fluid volumes.The method was tested in Houston, Texas, for 7 months of 1966, during which period 2795 isolates were made from 10 concentrates of 1-US-gallon (3.78-litre) samples and only 4 from unconcentrated sewage. The isolates included types 2 and 3 poliovirus, 9 echovirus types and 2 coxsackieviruses.Examination of these type 2 poliovirus strains isolated over a 4-month period showed that 13 of 19 had d(+) markers (although none was T(+)), indicating either that the vaccine strain had reverted in the d marker, or that wild strains were circulating in the population in spite of the absence of clinical disease.

Adsorption↗
PubMed1966

Plaque enhancement of enteroviruses by magnesium chloride, cysteine, and pancreatin.

Wallis, Craig (Baylor University College of Medicine, Houston, Tex.), Fred Morales, Joycelyn Powell, and Joseph L. Melnick. Plaque enhancement of enteroviruses by magnesium chloride, cysteine, and pancreatin. J. Bacteriol. 91:1932-1935. 1966.-Plaque formation of 21 echoviruses (types 1-6, 9, 13, 15-19, 23-26, 29-32) and 8 coxsackieviruses (B1-6, A7, and A9) was enhanced by increased concentrations of MgCl(2), l-cysteine, and pancreatin in agar overlay medium. In most cases, cationic and anionic polymers (diethylaminoethyl dextran, dextran sulfate, or protamine sulfate) were ineffective. All strains of poliovirus and group B coxsackieviruses were enhanced under agar by MgCl(2). Five of the eight coxsackieviruses tested were also enhanced by cysteine or pancreatin. Certain enteroviruses, which have been difficult to assay by plaque method, can now be quantified effectively by incorporation of additives such as MgCl(2), cysteine, or pancreatin into the overlay medium.

Chlorides↗
PubMed1966

Effects of pancreatin on the growth of reovirus.

Wallis, Craig (Baylor University College of Medicine, Houston, Tex.), Joseph L. Melnick, and Fred Rapp. Effects of pancreatin on the growth of reovirus. J. Bacteriol. 92:155-160. 1966.-The influence of pancreatin and other proteolytic enzymes on the growth, plaque formation, and antigenicity of reovirus was studied. Single-cycle yields of virus in the presence of enzyme were not increased, but multiple-cycle yields of virus were greatly enhanced. Immunofluorescence studies demonstrated that the transmission of reovirus from cell to cell is more rapid in the presence of the enzyme. These findings led to the development of a rapid plaque assay system for reovirus, a virus which has previously been difficult to assay by the plaque method. In the recommended procedure, pancreatin is incorporated into the agar overlay. Monkeys immunized with enzyme-treated reovirus yielded higher antibody titers than animals receiving the same amount of untreated virus.

Adsorption↗
PubMed1965

Protection of Measles Virus by Sulfate Ions Against Thermal Inactivation.

Rapp, Fred (Baylor University College of Medicine, Houston, Tex.), Janet S. Butel, and Craig Wallis. Protection of measles virus by sulfate ions against thermal inactivation. J. Bacteriol. 90:132-135. 1965.-The infectivity of measles virus in water is rapidly destroyed at temperatures of 37 C and above. More than 50% of the infectivity is lost after 1 hr at 25 C, and almost 90% loss of infectivity occurs within 24 hr at 4 C. Magnesium chloride enhances the inactivation of the virus at all temperatures tested. Addition of either magnesium or sodium sulfate protects the virus against thermal inactivation. The stabilizing effect is demonstrable at temperatures ranging from 4 to 56 C, but is especially pronounced through 45 C. Prolonged storage (up to 6 weeks) of the virulent virus at 4 C in 1 m magnesium sulfate permits retention of substantial infectivity, whereas storage at 4 C in either water or 1 m magnesium chloride results in a loss of infectivity approximating 99% after 2 weeks. Magnesium chloride also enhances inactivation of the attenuated vaccine strain of measles virus. The attenuated virus, however, is strongly protected by magnesium sulfate against thermal inactivation, and retention of infectivity for long periods of time at 4 C seems feasible when the virus is kept in 1 m magnesium sulfate.

Journal Article↗