Restriction enzyme fragment length polymorphisms of amplified herpes simplex virus type-1 DNA provide epidemiologic information

Divergence and genotyping of human alpha-herpesviruses: an overview

Herpesviruses are large DNA viruses that are highly disseminated among animals. Of the eight herpesviruses identified in humans, three are classified into the alpha-herpesvirus subfamily: herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), which are typically associated with mucocutaneous lesions, and varicella-zoster virus (VZV), which is the cause of chicken pox and herpes zoster. All three viruses establish lifelong infections and may also induce more severe symptoms, such as neurological manifestations and fatal neonatal infections. Despite thorough investigation of the genetic variability among circulating strains of each virus in recent decades, little is known about possible associations between the genetic setups of the viruses and clinical manifestations in human hosts. This review focuses mainly on evolutionary studies of and genotyping strategies for these three human alpha-herpesviruses, emphasizing the ambiguities induced by a high frequency of circulating recombinant strains. It also aims to shed light on the challenges of establishing a uniform genotyping strategy for all three viruses.

Recent progress in herpes simplex virus immunobiology and vaccine research

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) cause prevalent, chronic infections that have serious outcomes in some individuals. Neonatal herpes may occur when the infant traverses the cervix during maternal genital herpes. Genital herpes is a major risk factor for human immunodeficiency virus type 1 transmission. Considerable efforts have been made to design and test vaccines for HSV, focusing on genital infection with HSV-2. Several protein subunit vaccines based on HSV-2 envelope glycoproteins have reached advanced-phase clinical trials. These antigens were chosen because they are the targets of neutralizing-antibody responses and because they elicit cellular immunity. Encouraging results have been reported in studies of treatment of HSV-seronegative women with a vaccine consisting of truncated glycoprotein D of HSV-2 and a novel adjuvant. Because most sexual HSV transmission occurs during asymptomatic shedding, it is important to evaluate the impact of vaccination on HSV-2 infection, clinically apparent genital herpes, and HSV shedding among vaccine recipients who acquire infection. There are several other attractive formats, including subunit vaccines that target cellular immune responses, live attenuated virus strains, and mutant strains that undergo incomplete lytic replication. HSV vaccines have also been evaluated for the immunotherapy of established HSV infection.

Amplification of reiterated sequences of herpes simplex virus type 1 (HSV-1) genome to discriminate between clinical HSV-1 isolates

Herpes simplex virus type 1 (HSV-1)-related disease ranges from a localized, self-limiting illness to fatal disease in immunocompromised individuals. The corneal disease herpetic keratitis may develop after reactivation of a latent virus or reinfection with an exogenous herpesvirus. Molecular analysis of the virus involved may allow distinction between these two options. The HSV-1 genome contains several hypervariable regions that vary in numbers of reiterating regions (reiterations I to VIII [ReI to ReVIII]) between individual strains. Twenty-four HSV-1 clones, derived by subcloning of HSV-1 (strain F) twice in limiting dilutions, were tested in a PCR-based assay to analyze the stabilities of ReI, ReIII, ReIV, and ReVII. ReI and ReIII proved to vary in size upon subcloning, whereas ReIV and ReVII were stable. Subsequently, 37 unrelated isolates and 10 sequential isolates from five patients, all with HSV-1-induced keratitis, were genotyped for ReIV and ReVII. Of the 37 unrelated samples, 34 (92%) could be discriminated, while the genotypes of the viruses in sequential samples were identical for each individual. Conclusively, the data show that the approach presented allows the rapid and accurate discrimination of HSV-1 strains in studies that address the transmission and pathogenesis of HSV-1 infections.

Detection of human cytomegalovirus in peripheral blood leukocytes by the polymerase chain reaction and a nonradioactive probe

This study evaluated the effectiveness of polymerase chain reaction (PCR) combined with a nonradioactive probe for the early detection of cytomegalovirus (CMV) in buffy-coat specimens of immunocompromised patients. Dot-blot hybridization with a digoxigenin-labeled probe was used to detect a 262-bp PCR amplified fragment of the major immediate-early gene of CMV DNA. The results were compared with tissue cultures isolation of CMV. The study included 172 buffy-coat specimens from 72 immunocompromised patients. All 28 buffy-coat specimens positive by culture were also positive by PCR. The remaining 144 specimens were negative by culture; however, 47 of these were positive by PCR. Consequently, PCR was in agreement with culture results in 72% of the samples. Of the 47 PCR-positive-culture-negative specimens, 23 were from patients who had positive buffy-coat cultures at other times during their treatment. Chart review showed that an additional 16 of the PCR-positive-culture-negative samples were from patients with clinical evidence of active CMV disease. The eight remaining specimens were from five patients without signs of active disease. Specimens from 11 healthy volunteers were negative by PCR. In this study PCR was shown to be more sensitive than culture because it allowed earlier detection of viremia and demonstrated CMV in buffy-coat specimens that were negative by culture.