Presence Of Herpes Simplex Virus Type 1 DNA Research Articles

Herpes simplex virus type 1 shedding in the oral cavity of seropositive patients

Investigate the frequency of herpes simplex virus type 1 (HSV-1) reactivation in the oral cavity of seropositive patients with previous history of recurrent herpes labialis (recrudescent group) compared with those without any history of recrudescent lesions (asymptomatic HSV-1 infection). In addition, the relation between recrudescence and the presence of the virus in the saliva was assessed. Fourteen individuals with previous history of herpes labialis (recrudescent group) and 11 HSV-1 seropositive asymptomatic volunteers were included in the study. Swabs were performed periodically in all subjects and the presence of HSV-1 DNA was identified by nested PCR. All the 25 subjects enrolled in the study, revealed at least one positive swab for HSV-1. The frequency of HSV-1 positivity in the group with recrudescent herpes labialis was not statistically different from the other group. Ten subjects of the recrudescent group presented with herpes labialis at least once during the study. HSV-1 shedding in the oral cavity occurs independently of herpes labialis recrudescence.

Specific and Nonspecific Immune Stimulation of MHC-II-Deficient Mice Results in Chronic HSV-1 Infection of the Trigeminal Ganglia Following Ocular Challenge

Ocular herpes simplex virus type 1 (HSV-1) infection of MHC-II-deficient mice (AO/Oβ mice) or their parental C57BL/6J wild-type mice resulted in the establishment of typical HSV-1 latent infections in the trigeminal ganglia (TG) of the surviving mice by day 28 postinfection. Latency was characterized by the complete absence of infectious virus in TG extracts, the ability to recover latent virus only following prolonged tissue culture cultivation of explanted TG, and the presence of HSV-1 DNA in TG extracts. When mice were vaccinated prior to ocular HSV-1 challenge, latency appeared unaltered in the C57BL/6J wild-type mice. However, in AO/Oβ mice, clearance of virus from the TG appeared to be seriously impaired, resulting in a chronic productive infection, rather than a latent infection. Infectious virus was readily detected in TG extracts of vaccinated AO/Oβ mice until at least 63 days postinfection. Glycoprotein B mRNA was also readily detected, confirming continued viral transcription. These chronic infections occurred regardless of whether the AO/Oβ mice were vaccinated with HSV-1-specific antigens (i.e., live HSV-1 strain KOS, recombinantly expressed HSV-1 glycoprotein D plus Freund's adjuvant, or a mixture of seven recombinantly expressed HSV-1 glycoproteins plus adjuvant) or non-HSV-1-specific antigens (i.e., tissue culture medium plus 5% fetal bovine serum, the expression vector plus adjuvant, or adjuvant alone). Passive transfer of HSV-1 neutralizing antibody to vaccinated AO/Oβ mice between days 0 and 28 post-ocular challenge did not clear infectious virus from the TG. Passive transfer of anti-HSV-1 antibody or purified naive mouse serum to unvaccinated AO/Oβ mice on days 3 or 6 post-HSV-1 ocular challenge also resulted in chronic, rather than latent, infection of the TG. Passive transfer of naive sera from B-cell-deficient mice or injection of keyhole limpet hemocyanin or purified IgG, but not PBS or dextran, 3 days after HSV-1 challenge also resulted in chronic infection of the TG.

Human corneal cells and other fibroblasts can stimulate the appearance of herpes simplex virus from quiescently infected PC12 cells.

A two-cell system for the stimulation of herpes simplex virus type 1 (HSV-1) from an in vitro model of long-term (quiescent) infection is described. Rat pheochromocytoma (PC12) cells differentiated with nerve growth factor were infected with HSV-1 strain 17. Little, if any, cytotoxicity was observed, and a quiescent infection was established. The long-term infection was characterized by the absence of all detectable virus in the culture medium and little, if any, detectable early or late viral-gene expression as determined by reverse transcriptase PCR analysis. The presence of HSV-1 DNA was determined by PCR analysis. This showed that approximately 180 viral genomes were present in limiting dilutions where as few as 16 cells were examined. The viral DNA was infectious, since cocultivation with human corneal fibroblasts (HCF) or human corneal epithelial cells (HCE) resulted in recovery of virus from most, if not all, clusters of PC12 cells. Following cocultivation, viral antigens appeared first on PC12 cells and then on neighboring inducing cells, as determined by immunofluorescent staining, demonstrating that de novo viral protein synthesis first occurred in the long-term-infected PC12 cells. Interestingly, the ability to induce HSV varied among the cell lines tested. For example, monkey kidney CV-1 cells and human hepatoblastoma HepG2 cells, but not mouse neuroblastoma cells or undifferentiated PC12 cells, mediated stimulation. This work thus shows that (i) quiescent HSV infections can be maintained in PC12 cells in vitro, (ii) HSV can be induced from cells which do not accumulate significant levels of latency-associated transcripts, and (iii) the activation of HSV gene expression can be induced via neighboring cells. The ability of adjacent cells to stimulate HSV gene expression in neuron-like cells represents a novel area of study. The mechanism(s) whereby HCF, HCE, and HepG2 and CV-1 cells communicate with PC12 cells and stimulate viral replication, as well as how this system compares with other in vitro models of long-term infection, is discussed.

Long term herpes simplex virus type 1 infection of nerve growth factor-treated PC12 cells

The behaviour of herpes simplex virus type 1 (HSV-1) strain 17 in tissue cultures of PC12 cells treated with nerve growth factor (NGF) was studied. PC12 cells respond to NGF by ceasing to proliferate and extending long neurites. After differentiation with NGF, cultures were infected with HSV-1 and maintained in the presence of the hormone for several weeks. These long-term infected cultures were tested for HSV DNA, transcripts and the ability to produce virus, before and after NGF removal. Before NGF removal, the cultures were characterized by little or no virus production and the presence of HSV-1 DNA in a predominantly endless form. In situ analysis of long-term infected cultures revealed latency-associated transcript expression in only a portion of the cells. However, as shown by an infectious centre assay, virus was present in almost all cells in the population. Moreover, removal of NGF from long-term cultures resulted in the appearance of significantly increased amounts of virus in the media. The degree to which this system resembles HSV latency in vivo is discussed.