SUMMARYVirus structural antigens were localized within a line of monkey kidney (MA104) cells infected with the simian rotavirus SA11 using electron microscopic immunoperoxidase techniques. When hyperimmune guinea-pig anti-SA11 serum was used, virus particles, membranes of virus-associated endoplasmic reticulum, and viroplasmic inclusions were most heavily labelled. A general cytoplasmic reaction (ribosomes, intracytoplasmic membranes, etc.) with anti-SA 11 serum was also observed, but nuclei were unstained. In addition, several other virus-induced structures were found to contain rotavirus proteins, including convoluted smooth membrane within the endoplasmic reticulum, aberrant virus-like particles, and 15 to 20 nm diam. cytoplasmic tubules. Monospecific antiserum to VP7 (outer capsid glycoprotein, mol. wt. 38 000) reacted strongly with virus particles and the virus-associated endoplasmic reticulum, but reacted poorly with viroplasmic inclusions. The nucleus and general cytoplasm were unstained with anti-VP7. In contrast, monospecific antisera to VP2 and VP6 (inner capsid proteins, tool. wt. 94000 and 41000 respectively) reacted very strongly with viroplasmic inclusions. Virus particles, endoplasmic reticulum and cytoplasmic ribosomes were also labelled with these sera. These results indicate that rotavirus inner capsid proteins are synthesized throughout the cytoplasm and become concentrated in viroplasmic inclusions, while the outer capsid glycoprotein is synthesized primarily on ribosomes of the rough endoplasmic reticulum. Thus, the outer capsid layer appears to be acquired during virus budding into cisternae of the endoplasmic reticulum.

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Relatively few studies have been conducted on the occurrence of enteric viruses in drinking water in developing countries. In this study, we sought to apply positively charged microporous filters to the detection of enteric viruses in the drinking water of several major Colombian cities. Finished drinking water samples were collected at several drinking water plants whose treatment included flocculat ion, sand filtration and chlorination. Drinking water samples were also collected from the taps of private homes, hotels and community taps. Viruses were concentrated by passage of 20-99 liters of water through 50S Zeta-plus or 1 MDS Virosorb positively charged filters. Adsorbed viruses were eluted with 10% tryptose phosphate broth adjusted to pH 9.5 and concentrated to a final volume of 2 ml by ultracentrifugation before assay. Enteroviruses were detected by assay on BGM cells and rotavirus by assay on MA-104 cells. Out of eight samples of finished drinking water leaving the plants studied, three were found to contain enteric viruses. Rotaviruses were detected in two samples and enterovirus in one. Two of the samples containing enteric viruses also contained greater than 100 coliforms/100 ml. Rotaviruses were isolated from three tapwater samples and enteroviruses from one. All the tapwater samples which contained enteric viruses had visible turbidity and also contained coliform bacteria.

Drinking and other types of waters in three Latin American countries were sampled for the presence of enteroviruses, rotaviruses, and coliphages. Large volumes of water and sewage were concentrated using a positively charged filter for the detection of enteric viruses. Statistical analyses indicated no correlation between the presence or absence of fecal coliforms, total coliforms, fecal streptococci, and viruses. Total coliforms and fecal streptococci were isolated in large numbers from pristine tropical rain forest streams, but no enteric viruses were detected in any of the same samples. All streams contaminated with sewage contained enteric viruses and high levels of indicator bacteria. These results indicate that at the present time there is no reliable indicator of the presence of viruses in waters. The presence of coliphages in waters seemed associated with fecal contamination. The large numbers of fecal streptococci and coliforms (both fecal and total) present in the waters sampled may not necessarily indicate that these waters are contaminated with fecal waste.

Membrane filter adsorption-elution is an efficient method for concentration and partial purification of several types of viruses from various aqueous solutions. For efficient virus adsorption to negatively charged filters, the sample is adjusted to pH 3.5 and trivalent salts are added before filtration. Since influenza virus is sensitive to extremes in pH, it cannot be concentrated by ordinary filters. Zeta Plus filters, which have a net positive charge of up to 5 or 6, were evaluated for the concentration of influenza virus from infectious allantoic fluids. Influenza virus efficiently adsorbed to Zeta Plus filters at pH 6, and addition of salts was not necessary. AdsoTbed virus was eluted in a small volume of 2% bovine serum albumin plus 1 M NaCl at pH 10. By this procedure, viruses in 100 ml of allantoic fluid were concentrated to a final volume of 8 ml, with an average recovery efficiency of 71.0%.