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A 'nonspecific' fluorescence probably caused by immunocomplexes appears in the lung tissue of immunocompetent hosts infected with Korean hemorrhagic fever (KHF) or epidemic nephropathy (EN) viruses. Indirect immunofluorescence tests with such KHF- or EN-infected tissue as antigen are unsatisfactory for the detection of low-titer antibody or the reading of titer endpoints. Treatment of acetone-fixed lung sections at pH 3.0 followed by washing with 0.01 M phosphate-buffered saline and distilled water apparently dissolves the immunocomplexes, resulting in an effective removal of the 'nonspecific' fluorescence while the viral antigens are not significantly impaired. Lung sections of KHF-infected Apodemus agrarius coreae and EN-infected Clethrionomys glareolus, acetone-fixed and treated at pH 3.0, were used for the antigenic differentiation of the EN and KHF viruses.

Particles of the U2 strain of tobacco mosaic virus (TMV) were partly disassembled by SDS, treated with RNases and then phenol, and yielded RNA molecules one quarter to half the size of the intact virus genome. These molecules, when translated in vitro, produced the coat protein of the virus. Reassembly experiments indicated that the active messenger molecules were those that most rapidly reassembled with coat protein; the rate of reassembly was greatly diminished by treatment with spleen phosphodiesterase. Particles of sunnhemp mosaic virus (the bean strain of TMV) resist disassembly by detergent much more than those of the U2 strain of TMV.

The base composition of the genomes of bacteriophages and other viruses is, in a very general way, related to the base composition of the genomes of their hosts by the statistically significant linear regression: (phage GC%)=9.12 + 0.74 (host GC%). The significance and possible use of this relationship is discussed.

The amino acid sequences of the virion proteins of 7 definitive tobamoviruses have been compared. The results show that the proteins may be arranged unequivocally in a single dendrogram which, by analogy with similar comparisons of other sets of homologous proteins, probably reflects their phylogeny. The magnitude of the differences between these sequences suggests that the tobamoviruses are at least as old as flowering plants. The sequence differences are significantly correlated with serological differences and with differences in amino acid composition, and so the latter was used to compute a classification of 13 tobamoviruses that also probably reflects their phylogeny. The possible ages of several other virus groups are discussed.

RNAs associated with polyribosomes in plants infected with the U2 strain of tobacco mosaic virus (TMV) or with sunnhemp mosaic virus have been isolated. Most are about 0.35 × 106 daltons in

Plants mixedly infected with the U2 strain of tobacco mosaic virus (T2MV) and sunnhemp mosaic virus (SHMV) and grown at 35 degrees, yield particles of the same modal lengths (300 and 40 nm) as those found in plants singly infected with SHMV, but not in plants infected with T2MV, which yield only the long particles. At least some of the particles produced in mixedly infected plants contain coat proteins of both viruses. When RNAs from these particles are translated in vitro the coat proteins of both viruses are produced, although when a mixture of RNAs from particles of SHMV and T2MV, grown separately, are translated in vitro only SHMV protein is produced. These and other results suggest that the short particles produced in mixedly infected plants contain both coat protein messengers.

Peste des petits ruminants (PPR) is a virus disease of sheep and goats in West Africa. When first described, the virus was considered a variant of rinderpest virus. The biological and physicochemical characteristics of the virus indicate that it is closely related to measles, rinderpest and canine distemper viruses. These three viruses form the genus Morbillivirus of the Paramyxoviridae. PPR virus is sufficiently distinct from these 3 viruses to justify considering it as the fourth member of the Morbillivirus genus.

Tubulovesicular structures, measuring 20-50 nm in diameter, were found in dilated neuronal processes in brains from mice infected with the Fujisaki strain of Creutzfeldt-Jakob disease virus. These particles were similar to those observed in brains from hamsters infected with scrapie. These structures are consistently present in naturally occurring and experimentally induced spongiform encephalopathies, irrespective of the host species or virus strain. Their role in pathogenesis is undetermined.

Particles of sunnhemp mosaic virus (SHMV) are denser than those of the U2 strain of tobacco mosaic virus (T2MV) when their densities are estimated by equilibrium centrifugation in gradients of either cesium chloride or Metrizamide; in cesium chloride the densities are 1.318 and 1.307 g/ml, and in Metrizamide they are 1.249 and 1.240 g/ml. Experiments with particles reassembled from homologous or heterologous mixtures of the RNAs and coat proteins of the viruses show that the difference in their densities is determined by their coat proteins. The disassembled coat proteins of the two viruses have the same density, but polymerized SHMV protein is less dense than polymerized T2MV protein. Particles reassembled from homologous or heterologous mixtures of the RNAs and coat proteins of the viruses have the density of the nucleoprotein particles used as the source of protein. The density difference of the two virus nucleoproteins therefore reflects the different behavior of the two proteins on assembly with RNA.

Seedlings of Kennedya rubicunda were manually inoculated with Kennedya yellow mosaic virus and planted along with comparable virus-free seedlings in a coastal bushland site where the plant and virus were common. Virus infection decreased the growth rate of the plants by about one-third; however, virus-free plants disappeared more than twice as quickly as infected plants as a result of grazing by herbivores. In palatability trials using grated carrot bait, caged young rabbits preferred bait mixed with powdered virus-free K.rubicunda leaves to that mixed with virus-infected leaf powder. However, 'polyamine extracts' of the leaves did not have a comparable effect.

The amino acid composition of the coat proteins of the following viruses is reported: Andean potato latent, clitoria yellow vein, desmodium yellow mottle, dulcamara mottle, eggplant mosaic, okra mosaic, ononis yellow mosaic, scrophularia mottle, and, as controls, cocksfoot mild mosaic and cocksfoot mottle viruses. These data, together with some already published, were used to compute classifications of the tymoviruses. These classifications show a general similarity to Koenig's serological classification of the tymoviruses, but the correlation is poor, unlike similar comparisons of tobamovirus classifications. Several possible reasons for the poor correlation have been examined and excluded, and its implications are discussed.

Particles from plants mixedly infected with two tobamoviruses, whose particles differ in density, were all of a single, intermediate density, suggesting that they contain both coat proteins and that the proteins occur in the same proportion in all particles. Plants inoculated with the genome-containing particles of one of the tobamoviruses together with the noninfective, short, coat protein messenger-containing particles of the other yielded only particles with the density of the first; there was no evidence of complementation.

The World Health Organization (WHO) convened a Scientific Group to adapt its program in virus diseases to recent progress in virology. The program consists of (a) general activities, such as reference services and the supplying of reagents by the WHO Collaborating Centres and (b) specific activities to solve problems-including the promotion of necessary research-caused by certain diseases of public health importance. The Group reviewed problems caused by influenza and other respiratory viruses, enteroviruses, gastroenteritis viruses (for which types A and B have been proposed as a convenient nomenclature), viral hepatitis, viruses in water and sewage, arboviruses, arenaviruses and Marburg virus, measles and rubella vaccination, smallpox, rabies, chronic infections, herpesviruses, oncogenic viruses, congenital infections, nosocomial infections, chlamydial and rickettsial infections, and mycoplasma infections.

Soybean virus Z is a hitherto undescribed virus of soybeans found in Australia. It has a limited host range, attains a low concentration in plants and has a thermal inactivation point of 65 degrees. It has flexuous filamentous particles with a modal length of 610 nm and forms amorphous inclusions, but no pinwheels, in infected cells. It has not been transmitted by aphids or by seed. Its genome is RNA with the composition G23, A26, C25, U26, and its coat protein weights about 2.7 X 104. This virus seems to be unrelated to previously described viruses of soybeans, and does not fall into any of the described virus groups with similar particles.

Cycloheximide, but not chloramphenicol, greatly decreases the incorporation of radioactive amino acids into the particles of broad bean mottle virus, eggplant mosaic virus, and the type and U5 strains