Biomedical subjects

K A Laycock

Publications and source records attributed to K A Laycock.

28 records · Page 2Linked to original sources

PubMed1994

The role of nerve growth factor in modulating herpes simplex virus reactivation in vivo.

The role of nerve growth factor (NGF) in the modulation of herpes simplex virus (HSV) latency and reactivation was investigated in a mouse model. To determine whether NGF depletion would reactivate latent virus, concentrated anti-NGF serum antibodies were administered intraperitoneally to latently infected mice for 9 consecutive days. To determine whether NGF given prophylactically could suppress UV-B-induced viral reactivation, mice were irradiated with UV-B while being treated with NGF using diverse regimes over a 4-day period. Following intraperitoneal administration of anti-NGF antibodies, viral shedding was detected in a small number (10%) of mice, but it was not possible to pharmacologically suppress UV-B-induced viral reactivation with NGF. It would appear, therefore, that HSV latency in neurons innervating the cornea can be sustained and disrupted by physiological factors independent of NGF levels.

Animals↗

PubMed1994

A structural and functional comparison of the latency-associated transcript promoters of herpes simplex virus type 1 strains KOS and McKrae.

The promoters of the latency-associated transcripts (LATs) of herpes simplex virus type 1 (HSV-1) strains KOS and McKrae were compared to examine their influence upon the reactivation phenotypes of these two strains. Unlike strain KOS, McKrae is readily reactivable using in vivo reactivation models. We found greater than 96% sequence conservation between KOS and McKrae in the LATs promoter region, and both promoters showed equivalent basal and inducible activities. An inter-strain recombinant (termed MK13) was constructed in which the LATs promoter of HSV-1 McKrae was recombined into the background of HSV-1 strain KOS. In a murine u.v. light-induced reactivation model, virus shedding was detected by eye swabbing in two of 44 (5%) mice infected with KOS, 20 of 42 (48%) mice infected with McKrae and none of 45 (0%) mice infected with MK13. These data show that the LATs promoters of these viruses are structurally and functionally similar and that transfer of the LATs promoter from McKrae into KOS is insufficient to confer a reactivatable phenotype.

Animals↗

PubMed1993

Prophylactic acyclovir effectively reduces herpes simplex virus type 1 reactivation after exposure of latently infected mice to ultraviolet B.

PURPOSE: To determine the potential efficacy and anatomic sites of action of prophylactic oral acyclovir using a murine model of ultraviolet-B-induced reactivation of herpes simplex 1 keratitis. METHODS: Latent infection with herpes simplex 1 (McKrae) was established in 80 National Institutes of Health inbred strain of mice. Forty of the mice were given acyclovir orally and the other 40 latently infected mice served as controls. Mice were exposed to 250 mJ/cm2 of ultraviolet-B radiation and killed on days 1, 2, 3, and 4 after ultraviolet-B radiation. Trigeminal ganglia and eyes from these mice were homogenized and incubated on Vero cell monolayers for recovery of reactivated virus. RESULTS: Based on the recovery of infectious virus after ultraviolet-B in treated versus control groups, acyclovir effectively reduced detectable viral reactivation at both the ocular level (P = 0.003) and the ganglionic level (P = 0.025). The numbers of viral culture-positive eye and trigeminal ganglia homogenates in the control group were 11 and 6 out of 40, respectively, compared to 1 and 0 out of 40 culture-positive eye and trigeminal ganglia homogenates in the acyclovir treated mice. Therapeutic serum levels of acyclovir were confirmed by high performance liquid chromatography. In the acyclovir-tested group, the single case of viral break-through at the ocular surface was not an acyclovir-resistant mutant. CONCLUSION: Prophylactic acyclovir effectively reduces the incidence of herpes simplex virus-1 reactivation after ultraviolet-B-induced reactivation in National Institutes of Health inbred strain of mice.

Acyclovir↗

PubMed1993

Herpes simplex virus type 1 transcription is not detectable in quiescent human stromal keratitis by in situ hybridization.

PURPOSE: The purpose of this study was to determine whether herpes simplex virus (HSV) transcripts are present in the corneas of patients with chronic herpetic stromal keratitis. METHODS: Corneal buttons from patients with a history of stromal keratitis, but no ongoing active disease, together with positive and negative control tissues, were analyzed by in situ hybridization using single-stranded RNA probes for all three classes of viral lytic cycle transcripts as well as for the latency-associated transcripts (LATs). Tissues also were screened for presence of HSV genomic DNA using the polymerase chain reaction (PCR). RESULTS: HSV DNA was detected in 7 of 13 quiescent corneas by PCR, but no viral transcripts were detected in any of these corneas by in situ hybridization. CONCLUSIONS: At the level of detection afforded by in situ hybridization, HSV persistent in scarred human corneas after stromal keratitis appears to be transcriptionally dormant. This contrasts with the situation in neurons of latently infected sensory ganglia, in which LATs are present at high levels.

Animals↗

PubMed1993

Corneal Langerhans cell dynamics after herpes simplex virus reactivation.

PURPOSE: The authors investigated the progressive changes in the distribution of corneal Langerhans cells (LC) after reactivation of latent herpes simplex virus type 1 (HSV-1) in mice. METHODS: After corneal inoculation of National Institutes of Health inbred mice with HSV-1 and the establishment of latency, viral reactivation was induced by irradiating the ocular surface with 250 mJ/cm2 of ultraviolet B (UV-B) light. RESULTS: Subsequent viral replication in the cornea was followed by the migration of the LC toward the paracentral and central corneal epithelium. These areas are normally devoid of LC. The number of LC in the paracentral and central regions of the eye reached a peak at day 14 post-UV-B irradiation. After UV-B irradiation of mice latently infected with HSV-1, the development of corneal stromal opacification and neovascularization closely followed the migration of LC toward the central cornea and paralleled the influx of T-cells into the corneal stroma. This pattern was not observed in irradiated uninfected mice. CONCLUSIONS: LC migrate centrally in the corneal epithelium after viral reactivation. There is a direct correlation between the number of LC in the cornea and the degree of persistent stromal opacification.

Animals↗

PubMed1992

The use of polymerase chain reaction for the detection of chlamydial keratoconjunctivitis.

Ocular swabs from 30 consecutive patients with follicular conjunctivitis were screened for Chlamydia trachomatis, herpes simplex virus, and adenovirus by a variety of laboratory techniques. For the detection of C. trachomatis, we compared two polymerase chain reaction methods, McCoy cell culture isolation, and the direct fluorescein-conjugated monoclonal antibody test. Four of 30 patients tested positive for C. trachomatis by using both conventional and biotinylated polymerase chain reaction methods. Two of the four patients were also McCoy cell culture-positive for C. trachomatis and one of four patients tested positive by using a fluorescein-conjugated chlamydial monoclonal antibody test. All four patients responded to oral antibiotic treatment. On follow-up testing, all four patients were polymerase chain reaction-negative, McCoy cell culture-negative, and fluorescein-conjugated antibody test-negative for C. trachomatis. The polymerase chain reaction appears to be an equally specific and more sensitive method than McCoy cell culture or fluorescein-conjugated antibody testing for the detection of C. trachomatis from ocular specimens.

Adenoviridae Infections↗

PubMed1992

Reactivation of latent herpes simplex virus by excimer laser photokeratectomy.

We tested whether excimer laser photorefractive and phototherapeutic keratectomy may reactivate latent herpes simplex and cause recurrent keratitis in mice. Two of ten latently infected mice that were treated with ten excimer laser pulses to the corneal epithelium shed herpes simplex virus type 1, as did four of ten mice that were treated with 50 excimer laser pulses. Ocular shedding of herpes simplex virus was detected in four of ten mice that were treated with ethylenediamine-tetraacetic acid (EDTA) scraping of the corneal epithelium without laser keratectomy, and in six of ten mice on which combined EDTA-facilitated epithelial removal was performed followed by the application of ten excimer laser pulses. In both EDTA-treated groups, viral shedding was prolonged and 18 of 20 mice developed marked corneal opacification or neovascularization, or both. Corneal photoablation with the excimer laser may induce reactivation of latent herpes simplex virus, even in mice with clear and smooth-appearing corneas, and should be considered in the differential diagnosis of humans with persistent corneal epithelial defects after refractive or therapeutic excimer procedures.

Animals↗

PubMed1991

Characterization of a murine model of recurrent herpes simplex viral keratitis induced by ultraviolet B radiation.

The authors characterized a murine model of herpes simplex virus (HSV) reactivation in which recurrent herpetic keratitis was obtained in up to 80% of animals. Five weeks after ganglionic latency was established in National Institutes of Health inbred mice after corneal inoculation, HSV type 1 (HSV-1) was reactivated by irradiating the previously inoculated eye with ultraviolet (UV) light. Comparison of different UV wavelengths showed UVB to be optimal for reactivation, with peak viral recurrence being induced by a total exposure of approximately 250 mJ/cm2. Reactivated infectious virus generally began to appear in trigeminal ganglia 2 days postirradiation and was subsequently detectable in the cornea by both corneal swabbing and immunostaining for viral antigens. Two consecutive outbreaks of viral recurrence at the ocular surface were induced in selected animals by serial exposure to UVB. Advantages of this model over other models of recurrent keratitis are discussed.

Animals↗

PubMed1989

Detection of latent virus mRNA in tissues using the polymerase chain reaction.

The polymerase chain reaction (PCR) has been adapted for use in gene expression studies. Using this technique, we have been able to specifically detect Herpes simplex virus gene expression in the amount of RNA equivalent to that present in a single mouse ganglion. We have also detected specific transcription of the ras oncogene in biopsies of hepatocellular carcinoma tissue. The single tube RNA PCR reaction should be readily adaptable for use as a rapid screening tool in virus diagnosis; it is capable of detecting several virus infections simultaneously using extremely small tissue biopsies.

Animals↗

PubMed1989

Detection of herpes simplex virus type 1 gene expression in latently and productively infected mouse ganglia using the polymerase chain reaction.

The polymerase chain reaction (PCR) was employed to detect herpes simplex virus (HSV) sequences in the DNA, and HSV gene expression in total cell RNA, extracted from cervical and trigeminal ganglia of mice during productive and latent infection with HSV-1, strain SC16. Such gene expression was detected in 1 microgram or less of RNA, the quantity anticipated to be present in one or two cervical ganglia. Within the limits of the primers available, gene expression during latency appeared to be restricted to the latency-associated transcript (LAT). The 195 base portion of the LAT amplified by the PCR was sequenced and found to contain several base changes and deletions with respect to published sequences for different HSV strains. These mutations, within the putative open reading frame 2 of the LAT, formed stop or terminator signals, which suggests that the LAT does not act to establish or maintain latency through translation to a protein. The primers for the LAT also amplified a 300 bp fragment from any murine and some other mammalian RNAs. Apart from the oligonucleotide primers, this fragment did not show any homology with HSV.

Animals↗