The role of cell surface heparan sulfate in herpes simplex virus (HSV) infection was investigated using CHO cell mutants defective in various aspects of glycosaminoglycan synthesis. Binding of radiolabeled virus to the cells and infection were assessed in mutant and wild-type cells. Virus bound efficiently to wild-type cells and initiated an abortive infection in which immediate-early or alpha viral genes were expressed, despite limited production of late viral proteins and progeny virus. Binding of virus to heparan sulfate-deficient mutant cells was severely impaired and mutant cells were resistant to HSV infection. Intermediate levels of binding and infection were observed for a CHO cell mutant that produced undersulfated heparan sulfate. These results show that heparan sulfate moieties of cell surface proteoglycans serve as receptors for HSV.
Infection of human epidermoid carcinoma No. 2 cells with herpes simplex virus type 1 (HSV-1) leads to a reorganization of antigens associated with both the small and heterogeneous nuclear ribonucleoprotein complexes (snRNP and hnRNP). The hnRNP core protein antigens remain associated with the host chromatin, which appears to collapse into internal aggregates and along the nuclear envelope. More striking is the formation of prominent clusters of snRNP antigens (both general and U1 snRNP specific), which appear to condense throughout the nucleus then migrate to the periphery. These snRNP clusters have been identified at the fine structure level by immuno-electron microscopy. The HSV-1 presumed transcriptional activator ICP4, DNA-binding protein ICP8, and two capsid proteins ICP5 and p40 are not detectably associated with the snRNP clusters. Similar reorganization of snRNP occurs with HSV-2 and upon infection of African green monkey VERO cells with HSV-1. We speculate that the snRNP clusters arise from an increase in size and density of the interchromatin granule region of the host cell as a result of the partial inactivation of snRNP and host pre-mRNA splicing.
Spermatozoa from several mammalian species have been dissected by chemical methods to yield free heads, tails with attached midpieces, and tails from which the mitochondrial components of the midpiece were removed. Mouse and rat spermatozoa were cleaved by brief treatment with trypsin to yield free heads and tails, while human, guinea pig, and rabbit spermatozoa were cleaved by trypsin only after incubation with 2-mercaptoethanol or dithiothreitol. Spermatozoa were also cleaved at the junction of the head and the tail by treatment with acid and base. Mitochondria were removed from intact spermatozoa or isolated tails by mechanical shear after treatment with 2-mercaptoethanol or dithiothreitol. The dissected components of spermatozoa were fractionated with good yield and high purity by density gradient centrifugation. Ultrastructural analysis indicates that proteolytic cleavage to yield separated heads and tails occurs at a specific location in the neck of the spermatozoon, leaving the basal plate attached to the head of the cell. In contrast, after acid cleavage the basal plate remains with the midpiece. Proteolytic treatment has no apparent effect on any other spermatozoan structures, whereas acid or base treatment results in damage to the plasma membrane, the acrosome, and other structures. The specificity of the proteolytic cleavage suggests that a particular protein or group of proteins may be responsible for the linkage between the sperm head and tail.