Replacement of the deletion in the genome (0.762-0.789 mu) of avirulent HSV-1 HFEM using cloned MluI DNA fragment (0.7615-0.796 mu) of virulent HSV-1 F leads to generation of virulent intratypic recombinant.

The HFEM strain of HSV-1 is apathogenic for the tree shrew by the intraperitoneal (i.p.) route because of a deletion in the genome coordinates 0.762-0.789. Insertion of the MluI DNA fragment (coordinates 0.7615-0.789) cloned from HSV-1 strain F, which is pathogenic for the tree shrew, restored the i.p. pathogenicity to strain HFEM. The recombinant designated R-M1-C1 was highly pathogenic for the tree shrew, but slightly virulent for inbred mouse strain A. It thus appears that the viral DNA sequence involved in the i.p. pathogenicity of HSV-1 is located within the genome coordinates 0.761-0.796. This sequence is recognized differently by the cellular elements involved in HSV-1 infection in the tree shrew and the mouse.

Neurovirulence of herpes simplex virus type 1 depends on age in mice and thymidine kinase expression.

The susceptibility of mice of different ages (from four to 28 days) to infection with herpes simplex virus type 1 (HSV-1) mutants inoculated onto scarified corneas was studied. The TK+ isolate from wild type virus was pathogenic in mice of all age groups. An HSV-1 mutant (designated TK1/4) with a less active thymidine kinase (TK) gene expressing 25 per cent of the TK activity of the TK+ isolate was pathogenic for mice up to 10 days of age. In older mice, virus pathogenicity was dependent on the inoculum dose: increasing the TK1/4 virus dose tenfold raised the level of TK activity and thus the virulence of the virus. A TK- mutant with no TK activity was pathogenic for four to eight day old mice that have TK activity in the brain, but not in older mice. Thus, resistance to HSV-1 that is age-dependent in mice can be determined by the extent to which the virus strain is liable to express its TK gene and by the amount of TK activity present in the brain.

Effect of the flavonoid (+)cyanidanol-3 on procollagen biosynthesis and transport in normal and ataxia telangiectasis cultured skin fibroblasts.

The synthesis and secretion of procollagen into the medium of cultures of human skin fibroblasts from normal individuals and from patients with the genetic disorder, ataxia telangiectasia, are markedly inhibited by the flavonoid (+)cyanidanol-3. Those proteins which were secreted into the medium in the presence of cyanidanol were resistant to collagenase treatment (noncollagenous proteins). Polyacrylamide gel electrophoresis revealed the presence of only one noncollagenous protein of 66,000 daltons in the medium of cyanidanol-treated cells as compared with the nine other polypeptides found in the medium of untreated cells.

HSV-1 infection inhibits procollagen and protein secretion from normal and ataxia telangiectasia cultured skin fibroblasts.

Human skin fibroblasts derived from a healthy individual and from a child with the genetic disorder ataxia telangiectasia were infected with herpes simplex virus type 1 (HSV-1). The virus infection did not affect the synthesis of procollagen but inhibited its release from the cells.

A sequence in HpaI-P fragment of herpes simplex virus-1 DNA determines intraperitoneal virulence in mice.

The virulence of herpes simplex virus-1 (HSV-1) strains by the intraperitoneal (ip) route of injection in mice depends on the presence of an intact sequence in the HpaI DNA fragment P within coordinates 0.762 to 0.787. Deletion of the HpaI-P region (e.g., strain HFEM) abrogates the ability of the virus to infect mice by the ip route without affecting pathogenicity by the intracerebral (ic) route. A recombinant virus (M1C1) derived from DNA of the HSV-1 HFEM strain and the MLUIDNA fragment (coordinates 0.761 to 0.796) spanning the HpaI-P sequence of the pathogenic strain F regained pathogenicity for mice by the ip route.

A low thymidine kinase-producing mutant of herpes simplex virus type 1 causes latent trigeminal ganglia infections in mice.

The wild type NIH strain of herpes simplex virus type 1 (HSV-1) has a mixed plaque morphology of both large and small plaques. From this virus we selected a large plaque isolate that was a high producer of thymidine kinase (TK) activity (designated TK+) and a small plaque isolate that produced 25 per cent of the TK activity of the large plaque mutant (designated TK 1/4). A TK- mutant of the large plaque virus was obtained after passage of the virus in the presence of BUdR. The pathogenicity of the TK 1/4 virus strain in relation to the TK+ and TK- strains was investigated in mice after inoculation of the virus into the eyes by corneal scarification. The TK+ strain was highly pathogenic, caused encephalitis and killed most of the mice, whereas the TK- strain did not cause latent infections in the trigeminal ganglia or kill the mice. The TK 1/4 virus strain replicated in the eyes within 24 hours after inoculation and entered the trigeminal ganglia, establishing a latent infection in almost all of the mice. By increasing the infectious dose tenfold, the TK 1/4 virus caused an active infection in the trigeminal ganglia (ganglionitis), migrated to the brain, and killed the mice. The results indicate that not only is a low level of TK required to establish latent infections in mice, but also the degree of virulence is determined by the amount of TK produced by the infecting virus.