Viral Replication

Arenaviruses grow to high titer in cell cultures, replicating in the cytoplasm and maturing by budding from the plasma membrane. They have limited lytic

Table 32-2

Properties of Arenaviruses

Two serogroups Old World (LCM-LAS complex) and New World (Tacaribe complex) Spherical enveloped virion, 110-300 (generally 110-130) nm Virion contains nonfunctional ribosomes

Two closed-circular, loosely helical nucleocapsids with associated transcriptase

Genome comprises large (L, 7.2 kb) and small (S, 3 4 kb) segment of ssRNA, both ambisense

Viral proteins nucleoprotein (N), RNA polymerase (L), glycoproteins (G1, G2), zinc-binding protein (Z), plus poly(U) and poIy(A) polymerases, and protein kinase Replication occurs in cytoplasm, generally noncytocidal, causes persistent infection Genetic reassortment occurs during replication Maturation by budding from plasma membrane

Fig. 32-1 Arenavtridae (A) Negative stain, Tacaribe virus. (B) Lassa virus after budding from an infected cell (thin section). Bars, 100 nm (Courtesy Dr. F. A Murphy.)

capacity, usually leading to carrier cultures in which defective interfering (DI) particles are produced. After entry and uncoating of the virion, subgenomic mRNA encoding the nucleoprotein (N) is transcribed by the virion transcriptase from the minus sense {3') half of the ambisense S segment of the genome (Fig. 32-2). A short hairpin configuration in the intergenic region in the middle ol the S gene segment is thought to serve as the transcription termination signal The mRNA appears to derive its 5' cap by cap snatching from heterogeneous cellular RNA, as do orthomyxoviruses. Similarly, subgenomic mRNA encoding the transcriptase (L) is transcribed from the minus sense {3') portion of the ambisense L segment of the genome. Translation of both N and L proteins is required prior to replication of the viral genome, which requires the synthesis of full-length complementary copies of both ambisense genome


Ambisense S RNA

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