Drugs in development for herpes simplex and varicella zoster virus.

The alpha-herpesviruses varicella zoster virus (VZV) and herpes simplex virus (HSV) share common features including lifelong persistence in sensory ganglia and the risk of recurrences. For both HSV and VZV, standard-of-care (SoC) is based on nucleoside analogs (NAs), which require specific activation in infected cells. These existing drugs exhibit substantial limitations, warranting the development of new and more effective drugs.

Assessment of oncolytic HSV efficacy following increased entry-receptor expression in malignant peripheral nerve sheath tumor cell lines.

Limited expression and distribution of nectin-1, the major herpes simplex virus (HSV) type-1 entry-receptor, within tumors has been proposed as an impediment to oncolytic HSV (oHSV) therapy. To determine whether resistance to oHSVs in malignant peripheral nerve sheath tumors (MPNSTs) was explained by this hypothesis, nectin-1 expression and oHSV viral yields were assessed in a panel of MPNST cell lines using γ134.5-attenuated (Δγ134.5) oHSVs and a γ134.5 wild-type (wt) virus for comparison. Although there was a correlation between nectin-1 levels and viral yields with the wt virus (R=0.75, P =0.03), there was no correlation for Δγ134.5 viruses (G207, R7020 or C101) and a modest trend for the second-generation oHSV C134 (R=0.62, P=0.10). Nectin-1 overexpression in resistant MPNST cell lines did not improve Δγ134.5 oHSV output. While multistep replication assays showed that nectin-1 overexpression improved Δγ134.5 oHSV cell-to-cell spread, it did not confer a sensitive phenotype to resistant cells. Finally, oHSV yields were not improved with increased nectin-1 in vivo. We conclude that nectin-1 expression is not the primary obstacle of productive infection for Δγ134.5 oHSVs in MPNST cell lines. In contrast, viruses that are competent in their ability to counter the antiviral response may derive benefit with higher nectin-1 expression.

Clinical assessment of assays for diagnosis of herpes simplex infection.

It is becoming increasingly clear that the herpes simplex viruses (HSVs) 1 and 2 constitute a major, global, public health problem, particularly as genital herpes is implicated in the causation of a significant percentage of onwards transmission of the HIV virus. A major factor in the transmission of HSV is that most carriers are unaware of their diagnosis. In the last few years, the development of nucleic acid amplification technology and type-specific antibody serology to test for HSV-1 and -2 has contributed significantly to the accurate diagnosis of these infections. Despite guidance to the contrary, there is still much use of less sensitive tests such as viral culture and antibody testing based on crude antigen. It is essential that we use the most sensitive and specific diagnostic tests if we are to curb this epidemic.

In vivo experimentation with simian herpesviruses: assessment of biosafety and molecular contamination.

In vivo studies with highly pathogenic viruses prompt concerns regarding the persistence of infectious virus in pathology specimens. Although formalin fixation of tissues may inactivate infectious virus, fixation may also degrade viral nucleic acid and antigens, thereby limiting detection of virus in tissues by polymerase chain reaction (PCR) amplification or immunohistochemistry (IHC). We sought to: 1) assess the rate of inactivation of infectious virus in tissue specimens during formalin fixation, 2) assess IHC recognition of viral antigens and PCR detection of viral DNA after long-term (14 d) formalin fixation, and 3) investigate microtome contamination by DNA carry-over to subsequently sectioned tissues. Infectious baboon herpesvirus HVP2 could be recovered from fresh tissues of infected mice but not those fixed in formalin for >/=24 h. The intensity of IHC staining of viral antigen was unaffected by the duration of formalin fixation. PCR detection of viral DNA was negatively impacted by formalin fixation and/or heat inherent to paraffin processing; however, amplification of very short DNA sequences using real-time PCR was not affected. Lastly, microtome contamination by viral DNA was demonstrated by PCR screening of uninoculated control tissues that were sectioned after sectioning infected tissues. In summary, infectious virus is inactivated after only 24 h of formalin fixation whereas IHC staining remains sensitive in tissues fixed for up to 14 d. Formalin fixation does degrade DNA, but viral DNA can be detected by PCR amplification of very short DNA sequences. In addition, viral DNA can contaminate a microtome knife such that subsequently sectioned uninoculated control tissues exhibit false positive PCR amplification.

The assessment of IgG avidity in the evaluation of perinatal herpes simplex virus infection.

Classical serologic assays are not useful for the diagnosis of perinatal herpes simplex virus (HSV) infection during the acute phase of the disease. We report two cases of neonatal HSV infection that highlight the diagnostic value of HSV-specific IgG avidity and its contribution for further characterization of neonatal HSV infection.

Comparison of Cultureset and primary rabbit kidney cell culture for the detection of herpes simplex virus.

Herpes simplex virus isolation by conventional cell culture in primary rabbit kidney cells (RK) was compared with Cultureset (CS). At 24 h CS was more sensitive (31 versus 25 of 55 isolates detected) than RK, but at 48 h there was little difference (43 detected by CS, 46 by RK). CS stained at 48 h was significantly less sensitive (78.2%) than RK observed for 1 week. CS stained at 24 or 48 h was not an acceptable substitute for RK observed for 1 week.