Poliovirus infectivity

The higher than normal serum IgA in many children with protein calorie malnutrition may be related to increased synthesis of IgA by the intestinal lamina propria in resjionse to increased antigenic stimuli from bacteria and virus. This is probably supported by the observation that children with kwashiorkor were found to maintain their polio antibodies during malnutrition, and their immune mechanism seemed to be quite capable of inhibiting poliovirus infection, indicating that the intestinal receptor cell for poliovirus operates normally in kwashiorkor (B8). It is now known that polio antiliodies are mainly associated with IgA. 

Fig. I. Examples of Western blots stained with colloidal gold for total protein followed by immunostaining of individual antigensJ.anes 1—3 Proteins on a Western blot from a cytoplasmic extract of poliovirus-infected HEp-2 cells were stained with colloidal gold. The probing monoclonal antibodies, recognizing the viral proteins VP1 and precursor, VPO and VP2, and VP3, respectively, are detected by peroxidase-coupled rabbit-antimouse antibody (asterisks). Lane 4 Western blot of an E. coli lysate, containing a fusion protein composed of protein A and the poliovirus protein 2B. The fusion protein (arrowhead) is detected on the gold-stained blot by peroxidase-coupled IgG that binds to the protein A moiety.

Arita, M., Horie, H., Arita, M., and Nomoto, A. (1999). Interaction of poliovirus with its receptor affords a high level of infectivity to the virion in poliovirus infections mediated by the Fc receptor. J. Virol. 73, 1066-1074. 

A comparative study of different poliovirus capsid structures revealed a hydrophobic pocket that contained sites for cellular lipid interaction (Hogle et al, 1985 Filman et al, 1989). This lipid component, which is termed the pocket factor, may be sphingosine. Amino acids that modulate temperature sensitivity of poliovirus infectivity map to the interfaces between capsid protomers and are adjacent to the site of lipid binding. A similar lipid molecule appears to be present in some but not all... 

An inactivated trivalent vaccine developed by Jonas Salk was licensed for use in 1955. In 1987, an enhanced-potency inactivated poho vaccine (IPV) was introduced, and it has replaced the original inactivated vaccine. A live attenuated oral polio vaccine (OPV) was developed by Albert Sabin in 1962. OPV was the primary immunizing agent for poliovirus infection. Widespread OPV use is responsible for eradication of wild-type polio in most of the world. However, with no poliovirus circulation in the United States for years, IPV is the recommended vaccine for the primary series and booster dose for children. OPV will continue to be used in the areas of the world that have circulating pohovirus. The CEX7 maintains a stockpile of OPV to be used only in case of an outbreak. ... 

Table II. Predicted Log Concentrations of Poliovirus Infectivity in Equilibrium with Various Solids at pH 7.0...

Huang, A. S., and D. Baltimore. 1970. Initiation of polyribosome formation in poliovirus-infected HeLa cells. J. Molec. Biol., 47 275-292. 

Studies on the species of ENA that are inhibited after poliovirus infection have led to the conclusion that the synthesis of 45s nucleolar ribosomal precursor ENA is primarily depressed (18). The synthesis of non-ribosomal REA was not affected at early times after infection (I8). The appearance of mREA in polysomes is also not depressed in infected cells for at least 1-3 hours after infection (9f 19> 20). The conversion of the 45S ribosomal ENA precursor to the 32S and 18S ENA is inhibited or slowed (I8). The methylation of the 458 ENA was not inhibited, suggesting tha.t the virus is not exerting its action at this level (I8). 

The decrease in cellular protein synthesis could result from degradation or inactivation of cellular mRNA. Early studies (19 20), however, showed that cellular mRNA present in polysomes from poliovirus infected HeLa cells had the same sedimentation characteristics as that from uninfected cells. Because no appreciable degradation of cellular mRNA was observed, it was concluded that cellular protein synthesis inhibition does not result from an appreciable increase in endonuclease activity which would degrade cellular mRNA. 

Apparently related to the problem of host cell protein synthesis inhibition by viruses is the phenomenon of viral interference. In some cases, superinfection of a cell already infected with one virus does not affect the yield of the original virus. In other cases, however, the superinfecting virus completely inhibits translation of the original viral mRRA. Such is the case for superinfection of vesicular stomatitis virus (VSV)-infected cells by poliovirus (32). The kinetics and general properties of the shut-off of VSY protein synthesis appear to be the same as the shut-off of cellular protein synthesis after poliovirus infection... 

Another theory to explain the shut-off, proposed by Cooper et al. (4Q) involves the synthesis of viral proteins which have an affinity for the small ribosomal subunit and the 5 end of viral mENA. The viral protein would repress the synthesis of cellular proteins by combining with the 4OS subunit, thereby blocking its link with host mENA. By also binding to the 5 end of viral ENA, the proteins would facilitate the attachment of viral ENA to the 40s subunit and increase the translation of viral ENA. Viral proteins have been found to co-sediment with the 4OS subunits of HeLa cells infected with poliovirus (49)> of Ehrlich ascites tumor cells infected with EMC virus (50) and of L-cells infected with mengovirus (5 ) poliovirus infected cells, the viral proteins co-sedimenting with ribosomes were identified as VPO, VP1 and VP3, all structural proteins (49) Both structural and non-structural proteins were found associated with ribosomes from EMC... 

Most recently Rose et al. (55) have identified an initiation factor that is inactivated after infection of HeLa cells with poliovirus. In their experiments Rose al. (55) took advantage of the finding that translation of YSV mRNA, like host mRNA translation, is inhibited in cells superinfected with poliovirus (52, 56). They prepared extracts from poliovirus-infected and uninfected HeLa cells, and after a preincubation period and RNase treatment to eliminate endogenous mRNA translation, tested the ability of the extracts to translate exogenous poliovirus and 7SV mRNA. Poliovirus mRNA was translated by both extracts, but YSV mRNA was translated only in the extracts from uninfected cells. 

One way of searching for the presence of inhibitors of polypeptide initiation in infected cells was to add cytoplasmic fractions from virus infected cells to a cell-free system from rabbit reticulocytes. This system initiates the synthesis of new polypeptide chains at a very high rate. Cytoplasm from poliovirus infected HeLa cells, but not from uninfected cells, inhibited protein synthesis in the reticulocyte lysate (59) The inhibitor was isolated and identified as double-stranded (ds) RNA (60). To study the effect of ds RNA on host and viral protein synthesis, a cell-free system from HeLa cells was developed which initiated translation on endogenous cellular or viral mRNA. When added to this system, the ds RNA was found to inhibit the translation of both cellular and viral mRNAs (61). Furthermore, measurement of the amount of ds RNA present in cells early in infection (61, 62) revealed that an insufficient quantity was present to act as a direct agent of protein synthesis inhibition. 

Polysomes in normal and poliovirus-infected HeLa cells and their relationship to messenger-RNA. Proc. Natl. Acad. Sci. U.S.A. (1963), 4i, 654-661. 

LEIBOWITZ, R. and PENMAN, S. Regulation of protein synthesis in HeLa cells. III. Inhibition during poliovirus infection. 

KOSCHEL, K. Poliovirus infection and poly(A) sequences of cytoplasmic cellular RNA. J. Virol. (I974), IO6I-IO66. 

FERNANDEZ-MDNOZ, R. and DARNELL, J.E. Structural difference between the 5 termini of viral and cellular mRNA in poliovirus-infected cells Possible basis for the inhibition of host protein synthesis. J. Virol. (I976), 1 8, 719-726. 

HELENTJARIS, T. and EHRENFELD, E. Control of protein synthesis in extracts from poliovirus-infected cells. I. mRNA discrimination by crude initiation factors. J. Virol. (1978),... 

HUNT, T. and EHRENFELB, E. Gytoplasm from poliovirus-infected HeLa cells inhibits cell-free haemoglobin synthesis. Nature New Biology (1971)> 230. 91-94. 

The competition between viral and host mMAs was, therefore, localized at the level of a specific protein and, probably, offered the most satisfactory explanation for the molecular mechanism of the shut-off. It was also suggested that eIE-4B was specifically inactivated in poliovirus-infected cells (10). This was not in contrast with the results of the experiments mentioned above on the effect of eIF-4B on vitro translation and with the high affinity of EMC EITA for this initiation factor. However it has not definitely been established whether in infected cells eIP-4B is... 

Under properly defined conditions picomaviruses interrupt host RNA and protein synthesis (1 ) and subvert the cellular machinery to production of viral protein and ENA. By feeding radiolabeled amino acids to virus-infected cells after cessation of host-protein synthesis, viral protein can be selectively labeled. In a pioneering study, which introduced the now widely used SDS-polyacrylamide gel electrophoresis technique. Summers et al. (2) identified some 14 different virus-specified polypeptides in extracts of poliovirus infected HeLa cells. The net mass of these polypeptides exceeded two-fold or more the known coding capacity of the viral genome. 

Pigure 7. Proposed relationships among the major polypeptides produced in poliovirus-infected cells. The values enclosed in parentheses to the right of each polypeptide name refer to the apparent molecular weight of that polypeptide in the Mahoney strain. Not all polioviams strains produce detectable amounts of polypeptides Jc,... 

Approximately 25% of the total polysomes in poliovirus-infected and uninfected HeLa cells are membrane-bound (10). The membrane-bound polysomes are about five times more active in translation per unit mass than free polysomes, as determined by incorporation of amino acids in cell-free extracts (11). The exact role of the membrane in this process has not yet been defined. 

If one examines the pattern of proteins synthesized in cells infected for three to four hours with a picomavirus, the only proteins synthesized are viral, for by this time the synthesis of most host proteins has ceased. In the earliest studies carried out by Summers et al. (I4) in poliovirus-infected HeLa cells, about I4 different virus-specified polypeptides were identified by SDS-polyacrylamide gel electrophoresis. The net mass of these viral polypeptides, however, exceeded the coding capacity of the viral genome by a factor of 2. This finding was incompatible with what was then known about the translation of the small RNA bacteriophages such as Q6 and R17 In these cases, each of the three cistrons was found to have its own initiation and termination signals (15) ... 

Similar results were obtained with mengovirus. In the presence of p-fluorophenylalanine, canavanine and azetidine-2-carboxylic acid, two precursors larger than polypeptide A were detected (22). If these analogues plus ethionine were present, then a small amount of a polypeptide equivalent in size to poliovirus NCVP-00 was observed (23). Figure 4 shows the pattern of labeling obtained from mengovirus-infected L-cells (upper panel) and poliovirus-infected HeLa cells (lower panel) in the presence of the analogues. 

SDS-polyacrylamide gels of lysates of L and HeLa cells pulse labeled with 3H-amino acids in the presence of the amino acid analogues mentioned in the text. The positions of mengovirus capsid proteins are also shown. Upper panel mengovirus infected L-cells pulse labeled for 30 Diin at 6 hr post infection. Lower panel poliovirus infected HeLa cells pulse labeled for 30 min at 3 br post infection. Modified from Paucha ad. (25) ... 

Paucha and Colter (59) also observed that from early to late log phase of virus production, there was a progressive increase in the ratio of capsid to non-capsid polypeptides synthesized both in mengovirus and poliovirus infected cells (see Figure IO). They suggested that the synthesis of polio and mengovirus proteins may be under some sort of translational control. 

CHATTERJEE, N.K., KOCH, G. and WEISSBACH, H. Initiation of protein synthesis in vivo in poliovirus-infected HeLa cells. Arch. Biochem. Biophys. (l975)> 154 43I-437. 

Comparison of polysomal structures of uninfected and poliovirus infected HeLa cells. Virology (l97l), 44, 259-248. 

Recent evidence points to the presence of protease activity-associated with polysomes and ribosomes when extracts of uninfected cells are assayed (refs. 27 32, Figure j). Characteristic of infection of cells by poliovirus is drastic, rapid inhibition of protein synthesis. Poliovirus infection also depresses the ribosomal protease activity (27, 29, 55) Ribosomes from uninfected cells have been reported to possess an autoproteolytic activity (31, 32), and this has been confiimed by two-dimensional gel analysis (Figure 4) Poliovirus infection of HeLa cells reduces the autoproteolysis of isolated 808 ribosomes markedly (not shown). The inhibition of HeLa cell ribosomal protease activity requires protein synthesis, but proceeds in the presence of guanidine (55) ... 

Production of the new protease in poliovirus infection requires viral RHA synthesis, since the activity is not present in guanidine-treated cells (33) Protein synthesis is also necessary for production of the protease, because cycloheximide blocks its appearance. When amino acid analogs are added to poliovirus-infected cells at mid-cycle of replication, virus yields are greatly diminished by comparison there is a virtually normal yield of protease. However, the protease produced is heat sensitive, compared to the enzyme from untreated cells (Figure 7) This indicates the... 

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