Herpes Simplex Virus Serotypes Research Articles

Modified host defence peptide GF19 slows TNT-mediated spread of corneal herpes simplex virus serotype I infection

Corneal HSV-1 infections are a leading cause of infectious blindness globally by triggering tissue damage due to the intense inflammation. HSV-1 infections are treated mainly with antiviral drugs that clear the infections but are inefficient as prophylactics. The body produces innate cationic host defence peptides (cHDP), such as the cathelicidin LL37. Various epithelia, including the corneal epithelium, express LL37. cHDPs can cause disintegration of pathogen membranes, stimulate chemokine production, and attract immune cells. Here, we selected GF17, a peptide containing the LL37 fragment with bioactivity but with minimal cytotoxicity, and added two cell-penetrating amino acids to enhance its activity. The resulting GF19 was relatively cell-friendly, inducing only partial activation of antigen presenting immune cells in vitro. We showed that HSV-1 spreads by tunneling nanotubes in cultured human corneal epithelial cells. GF19 given before infection was able to block infection, most likely by blocking viral entry. When cells were sequentially exposed to viruses and GF19, the infection was attenuated but not arrested, supporting the contention that the GF19 mode of action was to block viral entry. Encapsulation into silica nanoparticles allowed a more sustained release of GF19, enhancing its activity. GF19 is most likely suitable as a prevention rather than a virucidal treatment.

Combination of long- and short-read sequencing fully resolves complex repeats of herpes simplex virus 2 strain MS complete genome.

Herpes simplex virus serotype 2 (HSV-2) is a ubiquitous human pathogen that causes recurrent genital infections and ulcerations. Many HSV-2 strains with different biological properties have been identified, but only the genomes of HSV-2 strains HG52, SD90e and 333 have been reported as complete and fully characterized sequences. We de novo assembled, annotated and manually curated the complete genome sequence of HSV-2 strain MS, a highly neurovirulent strain, originally isolated from a multiple sclerosis patient. We resolved both DNA ends, as well as the complex inverted repeats regions present in HSV genomes, usually undisclosed in previous published partial herpesvirus genomes, using long reads from Pacific Biosciences (PacBio) technology. Additionally, we identified isomeric genomes by determining the alternative relative orientation of unique fragments in the genome of the sequenced viral population. Illumina short-read sequencing was crucial to examine genetic variability, such as nucleotide polymorphisms, insertion/deletions and sequence determinants of strain-specific virulence factors. We used Illumina data to fix two disrupted open reading frames found in coding homopolymers after PacBio assembly. These results support the combination of long- and short-read sequencing technologies as a precise and effective approach for the accurate de novo assembly and curation of complex microbial genomes.

Comparison of infectivity and spread between HSV-1 and HSV-2 based oncolytic viruses on tumor cells with different receptor expression profiles.

Herpes simplex virus (HSV) is one of the many viruses that have been modified or adapted for oncolytic purposes. There are two serotypes of HSV, HSV-1 and HSV-2. The majority of oncolytic HSVs, including T-VEC which has recently been approved by the US Food and Drug Administration (FDA) for clinical use in treating late stage melanoma patients, are derived from HSV-1. Recently, we and others have developed several HSV-2 based oncolytic viruses. During our in vitro characterization of oncolytic viruses developed from both serotypes (Baco-1 from HSV-1 and FusOn-H2 from HSV-2), we noticed there is a subpopulation of cancer cells in which both viruses could infect but only FusOn-H2 could spread from cell to cell on monolayers. This observation prompted us to investigate the virus receptor expression profiles in these and other tumor cells. Our data show the following: 1) This subpopulation of tumor cells only express nectin-2, not the other two major receptors (HVEM or nectin-1). 2) Baco-1 grows to a higher titer than FusOn-H2 in this subpopulation of tumor cells, but the latter kills these tumor cells more efficiently than the former. 3) FusOn-H2 is effective at treating tumors formed from these tumor cells while Baco-1 is completely ineffective. Our results suggest that this subpopulation of tumor cells may be intrinsically resistant to the therapeutic effect of a HSV-1 based oncolytic virus but they remain sensitive to a HSV-2 based virotherapy.

P244 HSV serotypes in first episode genital herpes in North West Northern Ireland

Background/introduction Most populations have observed an increase in the role of HSV-1 as a cause of genital herpes simplex virus (HSV) Aims To analyse HSV serotypes in first episode genital herpes in North West Northern Ireland. Methods All patients who tested positive for HSV and were coded as C10A from 01/03/2015 – 01/03/2016 were included. Demographic details including sex, age, ethnicity and sexual identity were recorded. The confirmed serotype (HSV-1 vs HSV-2) was noted. Results A total of 36 cases of first episode genital HSV was seen. 100% were white Caucasian (35/36 White UK); 29 were female and 7 were male. All females self-reported as heterosexual and of the 2/7 men were MSM. Overall median age at diagnosis was 23 years old (range 16–40). Of the 36 positive PCR tests 83.3% (30) were HSV-1 and 6.7% (6) were HSV-2. The median age at diagnosis for HSV-1 was also 23 years (range 16–32); 26 were female and 4 male. Of the 6 positive who tested positive for HSV-2, 3 each were male and female. Conclusion It is well documented that HSV-1 is increasingly prevalent as a cause of first episode genital HSV, our rate of 83% for HSV-1 infection is notably high. Although not a significant diagnostic or management challenge this may reflect a lower prevalence of HSV-2 infection within the local sexually-active population or an increasing level of sexual risk behaviour capable of transmitting HSV-1 infection. Local clinicians need to be aware of the differences in prognosis for HSV-1 infection such that accurate information and advice can be given to help reduce stigma traditionally attached to HSV-2 infection.

The antiviral potency of Fagus sylvatica 4OMe-glucuronoxylan sulfates

Herpes simplex virus belongs to Herpesviridae family and causes infection of humans from ancient times. 4OMe-glucuronoxylans as the renewable biopolymers can be promising glycomaterials for various applications in pharmacy. Control enzymatic degradation of the native 4OMe-glucuronoxylan (GX1) followed by targeted sulfation procedure afforded a range of 4OMe-glucuronoxylan sulfates differed in the degree of sulfation (10–16%) and molecular mass (21,000–5000g/mol; GXS1>GXS2>GXS3>GXS4). Antiviral activity tests on GXS1–4 against herpes simplex virus (HSV) types 1 and 2 revealed the positive effect of all compounds against strains of herpes virus. Of them, the compounds GXS1 and GXS4 were shown to be the most active for both HSV serotypes. The antiviral activity of GXS1 and GXS4 was similar to those of heparin or dextran sulfate, used as reference compounds. It was found that GXS1 and GXS4 were active as well against Polio and dengue viruses, however, on a smaller scale. The mode of antiviral action of 4OMe-glucuronoxylan sulfates is due to inhibition of the virus binding to the cell receptors.

Synergistic effects of acyclovir and 3, 19-isopropylideneandrographolide on herpes simplex virus wild types and drug-resistant strains.

BackgroundAn andrographolide analogue, 3, 19-isopropylideneandrographolide (IPAD), exerts an inhibitory effect on replication of wild-type herpes simplex virus serotype 1 (HSV-1). In this study, we examined the anti-viral activity of IPAD on HSV wild types (HSV-1 strain KOS and HSV-2 clinical isolate) and HSV-1 drug-resistant strains (DRs). Synergistic effects of IPAD with acyclovir (ACV) were also evaluated.MethodsMTT and cytopathic effect (CPE) reduction assays were performed to determine cytotoxicity and anti-viral activities, respectively. A combination assay was used to determine synergistic effects of IPAD and ACV. Presence of viral DNA and protein in experimental cells was investigated using the polymerase chain reaction and western blotting, respectively.ResultsA non-cytotoxic concentration of IPAD (20.50 μM) completely inhibited CPE formation induced by HSV wild types and HSV-1 DRs after viral entry into the cells. The anti-HSV activities included inhibition of viral DNA and protein synthesis. The minimum inhibitory concentrations of ACV for HSV wild types and HSV-1 DRs were 20.20 and 2,220.00 μM, respectively. Combination of ACV with IPAD showed synergistic effects in inhibition of CPE formation, viral DNA and protein synthesis by HSV wild types as well as HSV-1 DRs. For the synergistic effects on HSV wild types and HSV-1 DRs, the effective concentrations of ACV were reduced.ConclusionsThese results showed the inhibitory potential of IPAD on HSV wild types and HSV-1 DRs and suggested that IPAD could be used in combination with ACV for treatment of HSV-1 DRs infections.

IgG in cervicovaginal mucus traps HSV and prevents vaginal herpes infections.

IgG is the predominant immunoglobulin in cervicovaginal mucus (CVM), yet how IgG in mucus can protect against infections is not fully understood. IgG diffuses rapidly through cervical mucus, slowed only slightly by transient adhesive interactions with mucins. We hypothesize this almost unhindered diffusion allows IgG to accumulate rapidly on pathogen surfaces, and the resulting IgG array forms multiple weak adhesive crosslinks to mucus gel that effectively trap (immobilize) pathogens, preventing them from initiating infections. Here, we report herpes simplex virus serotype 1 (HSV-1) readily penetrated fresh, pH-neutralized ex vivo samples of CVM with low or no detectable levels of anti-HSV-1 IgG, but was trapped in samples with even modest levels of anti-HSV-1 IgG. In samples with little or no endogenous anti-HSV-1 IgG, addition of exogenous anti-HSV-1 IgG, affinity purified from intravenous immunoglobulin, trapped virions at concentrations below those needed for neutralization and with similar potency as endogenous IgG. Deglycosylating purified anti-HSV-1 IgG, or removing its Fc component, markedly reduced trapping potency. Finally, a non-neutralizing IgG against HSV-gG significantly protected mice against vaginal infection, and removing vaginal mucus by gentle lavage abolished protection. These observations suggest IgG-Fc has a glycan dependent “muco-trapping” effector function that may provide exceptionally potent protection at mucosal surfaces.

A dual reporter cell assay for identifying serotype and drug susceptibility of herpes simplex virus

A dual reporter cell assay (DRCA) that allows real-time detection of herpes simplex virus (HSV) infection was developed. This was achieved by stable transfection of cells with an expression cassette that contains the dual reporter genes, secreted alkaline phosphatase (SEAP) and enhanced green fluorescent protein (EGFP), under the control of an HSV early gene promoter. Baby hamster kidney (BHK) and Chinese hamster ovary (CHO) cell lines were used as parental cell lines because the former is permissive for both HSV serotypes, HSV-1 and HSV-2, whereas the latter is susceptible to infection only by HSV-2. The DRCA permitted differential detection of HSV-1 and HSV-2 by observation of EGFP-positive cells, as substantiated by screening a total of 35 samples. The BHK-based cell line is sensitive to a viral titer as low as a single plaque-forming unit with a robust assay window as measured by a chemiluminescent assay. Evaluations of the DRCA with representative acyclovir-sensitive and acyclovir-resistant HSV strains demonstrated that their drug susceptibilities were accurately determined by a 48-h format. In summary, this novel DRCA is a useful means for serotyping of HSV in real time as well as a rapid screening method for determining anti-HSV susceptibilities.

APPLICATION OF POLYMERASE CHAIN REACTION TO DIFFERENTIATE HERPES SIMPLEX VIRUS 1 AND 2 SEROTYPES IN CULTURE NEGATIVE INTRAOCULAR ASPIRATES

Purpose: To standardize and apply a polymerase chain reaction (PCR) on the glycoprotein D gene to differentiate Herpes simplex virus (HSV) 1 & 2 serotypes in culture negative intraocular specimens. Methods: Twenty-one intraocular fluids collected from 19 patients were subjected to cultures for HSV and uniplex PCR (uPCR) for DNA polymerase gene. To differentiate HSV serotypes, as 1 & 2, a seminested PCR (snPCR) targeting the glycoprotein D gene was standardised and applied onto 21 intraocular fluids. The specificity of the snPCR was verified by application onto ATCC strains of HSV 1 and 2, clinical isolates and DNA sequencing of the amplified products. All specimens were also tested for the presence of cytomegalovirus (CMV) and varicella zoster virus (VZV) by nucleic acid amplification methods. Results: Four of the 21 intraocular fluids were positive for HSV by uPCR. snPCR detected HSV in three additional specimens (total of seven specimens), and identified three as HSV 1 and four as HSV 2. DNA sequencing of PCR products showed 100% homology with the standard strains of HSV 1 and 2 respectively. None of the samples were positive in culture. Among the other patients, CMV DNA was detected in two and VZV DNA in five others. Conclusions: The standardized snPCR can be applied directly onto the culture negative specimens for rapid differentiation of HSV serotypes.

Herpes simplex virus.

1. Linda A. Waggoner-Fountain, MD* 2. Leigh B. Grossman, MD† 1. *Assistant Professor of Pediatrics, Division of Infectious Diseases 2. †Professor of Pediatrics and Head, Division of Infectious Diseases, University of Virginia School of Medicine, Charlottesville, VA After completing this article, readers should be able to: 1. Describe the epidemiology of herpes simplex virus (HSV) and the distinctive epidemiologic features of HSV type 1 and type 2. 2. Characterize the pathogenesis, diagnosis, treatment, and outcome of HSV infections in the neonate. 3. Explain the variety of clinical manifestations and methods of diagnosis of HSV infections in older children and adolescents. 4. Discuss the appropriate potential prevention and therapy of HSV infections in infants, children, and adolescents. Herpes simplex infections have various presentations, depending on the immune status, the age of the host, and the route of transmission. Herpes simplex viruses (HSVs) are enveloped, double-stranded DNA viruses. The two serotypes of HSV are classified as HSV-1 and HSV-2. Infections with HSV-1 usually involve the face and skin “above the waist,” although HSV-1 also can cause genital infection. Infections with HSV-2 usually involve the genitalia and skin “below the waist” in sexually active adolescents and adults. Most HSV disease in neonates is due to HSV-2. HSV-2 also causes oral lesions in approximately 25% of the infected population. Throughout this article, we categorize HSV disease by the specific host. ### Neonatal The incidence of neonatal HSV infection is estimated at 1 per 3,000 to 20,000 live births. Between 20% and 40% of infants infected with HSV are born preterm. In the United States, approximately 75% of neonatal infections are due to HSV-2, with the remainder due to HSV-1. HSV infection develops in 33% to 50% of exposed infants born vaginally to mothers who have primary genital infection. The risk to an infant born to a mother shedding HSV as a result of reactivated infection is much lower (0 to 5%). More than 75% of infants who acquire HSV infection have been born to women who had no signs or symptoms suggestive of HSV infection before or …

Phenotypic and genotypic methods for the detection of herpes simplex virus serotypes

Typing of herpes simplex virus (HSV) into its serotypes plays a major role in epidemiology and management of reactivation. To develop and evaluate a polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) was employed using Hae III and Taq I against neutralization test, allele-specific PCR and DNA sequencing for the detection of HSV serotypes. Neutralization test, allele-specific PCR, DNA sequencing and PCR-based RFLP were applied simultaneously to 2 standard strains (HSV-1 and HSV-2) and 23 clinical isolates. PCR-based RFLP was applied further to 20 culture negative PCR positive clinical specimens. The 179 bp product of the clinical isolates and specimens amplified using the type-common primers of HSV was subjected to DNA sequencing and PCR-based RFLP. Allele-specific PCR was absolutely specific and highly sensitive. All the typing methods differentiated concordantly 23 clinical isolates into 12 HSV-1 and 11 HSV-2. DNA sequencing did not reveal any nucleotide variations within the serotypes among the isolates sequenced. PCR-based RFLP typed a further 20 culture negative clinical specimens into 15 HSV-1 and 5 HSV-2. PCR-based RFLP was a reliable, less laborious and cost-effective molecular biological tool for the determination of HSV serotypes both for the clinical isolates and culture negative specimens.

An appraisal of screening for maternal type-specific herpes simplex virus antibodies to prevent neonatal herpes

Almost all neonatal herpes simplex virus infections occur as a result of first-episode maternal infection during late pregnancy when delivery occurs before the development of protective maternal antibodies. Screening of pregnant women for the presence of type-specific herpes simplex virus antibodies has therefore been suggested as a means of identifying women vulnerable to herpes simplex virus acquisition and subsequent transmission of herpes simplex virus to their neonates. Couples in whom herpes simplex virus serotype discordance is identified could be counseled regarding sexual behavior modification to avoid maternal herpes simplex virus infection. However, the ramifications of routine screening for herpes simplex virus susceptibility during pregnancy could be profound in terms of costs, prenatal care delivery, and even social duress. The recent US Food and Drug Administration approval of type-specific herpes simplex virus antibody assays for clinical use lends temporal urgency to the need for a critical examination of the relevant data. After we performed such an evaluation and created a decision analysis model to assess the potential cost-effectiveness of herpes simplex virus antibody screening, we concluded that screening for maternal type-specific herpes simplex virus antibodies cannot be recommended to prevent neonatal herpes. (Am J Obstet Gynecol 2000;183:400-6.)

Characterization of a type-common human recombinant monoclonal antibody to herpes simplex virus with high therapeutic potential.

We report the characterization of a type-common human recombinant monoclonal antibody previously isolated by antigen selection from a phage-displayed combinatorial antibody library established from a herpes simplex virus (HSV)-seropositive individual. Competition with well-characterized murine monoclonal antibodies and immunodetection of gD truncations revealed that this antibody recognizes the group Ib antigenic site of glycoprotein D, a highly conserved and protective type-common determinant. To our knowledge, this is the first human group Ib monoclonal antibody ever described. The antibody also displayed first-order neutralization kinetics and a high neutralization rate constant, was capable of completely inhibiting syncytium formation by a fusogenic strain of HSV type 1, and efficiently neutralized low-passage clinical isolates of both HSV serotypes. Taken together with our earlier observations of the in vivo antiviral activities of this human recombinant antibody in animal models of HSV infection, the present results support the high therapeutic potential of this antibody.

Rapid DNA diagnosis of herpes simplex virus serotypes

The presence of nucleotide sequences specific for each of herpes simplex virus (HSV) serotypes was demonstrated. These sequences were applied for dot DNA-DNA hybridization and for PCR for rapid DNA diagnosis of HSV infections. These sequences were found by molecular cloning of HSV-DNA fragments after digestion of DNA by KpnI enzyme. The type 1-specific sequence was found around the 5' end of BamHI B-fragment in the L region of type 1 DNA (corresponds to α gene 27, promotor-regulatory region) and the type 2-specific sequence was around the junction region of the L and S of type 2 DNA (corresponds to a' sequence). Both simple dot blot hybridization and PCR of HSV DNA's, employing these type-specific nucleotide sequences, were proven to be much more useful than immunofluorescence in terms of type-specific diagnosis of HSV infections.

Initial interaction of herpes simplex virus with cells is binding to heparan sulfate

We have shown that cell surface heparan sulfate serves as the initial receptor for both serotypes of herpes simplex virus (HSV). We found that virions could bind to heparin, a related glycosaminoglycan, and that heparin blocked virus adsorption. Agents known to bind to cell surface heparan sulfate blocked viral adsorption and infection. Enzymatic digestion of cell surface heparan sulfate but not of dermatan sulfate or chondroitin sulfate concomitantly reduced the binding of virus to the cells and rendered the cells resistant to infection. Although cell surface heparan sulfate was required for infection by HSV types 1 and 2, the two serotypes may bind to heparan sulfate with different affinities or may recognize different structural features of heparan sulfate. Consistent with their broad host ranges, the two HSV serotypes use as primary receptors ubiquitous cell surface components known to participate in interactions with the extracellular matrix and with other cell surfaces.

Identification of herpes simplex virus type 1 (HSV-1) glycoprotein gC as the immunodominant antigen for HSV-1-specific memory cytotoxic T lymphocytes.

The frequency and fine specificity of herpes simplex virus (HSV)-reactive cytotoxic T lymphocytes (CTL) of C57BL/6 mice was investigated in limiting dilution culture. The reactivity patterns of virus-specific CTL were assayed on target cells infected with HSV type 1, strain KOS, HSV type 2, strain Mueller, and mutants of HSV-1 (KOS) antigenically deficient or altered in glycoproteins gC or gB, two of the four major HSV-1-encoded cell surface glycoprotein antigens. Most CTL clones recognized type-specific determinants on target cells infected with the immunizing HSV serotype. In addition, the majority of HSV-1-specific CTL did not cross-react with cells infected with syn LD70, a mutant of HSV-1 (KOS) deficient for the presentation of cell surface glycoprotein gC. These data are the first demonstration of the clonal specificity of HSV-1-reactive CTL, and they identify gC as the immunodominant antigen. The fine specificity of gC-specific CTL clones was analyzed on target cells infected with mutant viruses altered in the antigenic structure of gC. These mutants were selected by resistance to neutralization with monoclonal antibodies, referred to as monoclonal antibody-resistant (mar) mutants. Most mar mutations in gC did not affect recognition by the majority of CTL clones. This indicated that most epitopes recognized by CTL are distinct from those defined by antibodies. The finding, however, that one mar mutation in gC affected both CTL and antibody recognition of this antigen may help to define antigenic sites important to both humoral and cell-mediated immunity to herpesvirus infection.

Comparison of the Scott Selecticult-HSV kit with conventional culture and direct immunoperoxidase staining for detection of herpes simplex virus in cultures of clinical specimens

In a comparative study, clinical specimens were cultured for herpes simplex virus (HSV). The presence of virus was noted by the appearance of characteristic cytopathic effect, as determined by standard direct immunofluorescence techniques, by using a direct immunoperoxidase stain for viral antigen, or by using the Selecticult-HSV (SC-HSV) stain for viral antigen. There was 100% correlation between the SC-HSV stain and immunofluorescence staining in recognizing HSV-infected cells (81 of 81 positive specimens). In comparison with observation of cytopathic effect, the SC-HSV system and conventional culture detected 93 and 78% of positive cultures at 48 h postinoculation and 76 and 32%, respectively, at 24 h. By 5 days postinoculation, SC-HSV detected 100% of the positive specimens. As compared with the direct immunoperoxidase stain, SC-HSV stain was slightly more sensitive and gave less background stain. HSV serotypes 1 and 2 were both detected by the SC-HSV stain. The Scott SC-HSV kit appears to be an effective system for the diagnosis of HSV infections.

Herpes Dating Services

To the Editor.— We wish to comment on herpes dating services, a new social phenomenon that has recently emerged in many large cities (eg, New York, Chicago, Los Angeles). In our opinion, such services are not only unnecessary, but they actually may be detrimental from both medical and psychosocial points of view. Recent surveys have shown that genital herpes simplex infections may be caused by either of the two major serotypes of herpes simplex virus (type 1 and type 2). 1 Type 2 genital first infections are followed by recurrent episodes in about 60% of cases as compared with the 14% recurrence rate after type 1 virus caused first genital infections. 2 By means of restriction endonuclease analysis, it further has been shown that within each of the two major serotypes, numerous genetically different strains exist. A person can become exogenously infected or reinfected in similar or different areas with

Solid-phase enzyme-immunoassay for the detection of herpes simplex virus antigens in clinical specimens

An indirect solid-phase enzyme-immunoassay (EIA) for the detection of herpes simplex virus (HSV) antigens in clinical specimens was developed. Rabbits and guinea pigs were hyperimmunized with highly purified nucleocapsids of HSV type 1. Microtitre plates were coated with 0.25 μg of guinea pig anti-herpes simplex type 1 immunoglobulins per well. Clinical specimens, diluted in phosphate buffered saline containing fetal calf serum and detergents, were sonicated and incubated in the test wells overnight at 37°C. Rabbit anti-HSV immunoglobulins were added as a secondary antibody at a concentration of 3.2 μg per well, and peroxidase conjugated swine antibodies against rabbit immunoglobulins, diluted 1:1,000, were used as a fourth layer. Clinical specimens which were sent for virus isolation or for isolation of Chlamydia trachomatis were tested by the developed assay and 20 out of 27 isolation positive specimens were found positive by EIA. Five out of 67 specimens negative by isolation gave positive results by EIA. The specificity of the results was confirmed by a control test using wells coated with normal guinea pig immunoglobulins. The test detected antigens from both serotypes of HSV. Cross reactions with varicella-zoster- or with cytomegalovirus were not found, and antigens from uninfected cells did not result in false positive results.

Control of expression of the herpes simplex virus-induced deoxypyrimidine triphosphatase in cells infected with mutants of herpes simplex virus types 1 and 2 and intertypic recombinants.

Infection of cells with herpes simplex virus type 1 (HSV-1) induces high levels of deoxypyrimidine triphosphatase. The majority of the enzyme activity is found in infected cell nuclei. A similar activity is induced by HSV type 2 (HSV-2) which, in contrast to the HSV-1 enzyme, fractionates to more than 99% in the soluble cytoplasmic extract. Of a series of temperature-sensitive mutants of HSV-1 studied, only the immediate-early mutants in complementation group 1-2 (strain 17 mutants tsD and tsK and strain KOS mutant tsB2) induced reduced levels of triphosphatase at nonpermissive temperature. Of a series of temperature-sensitive mutants of HSV-2 strain HG52, ts9 and ts13 failed to induce wild-type levels of the enzyme at nonpermissive temperature; ts9 was the most defective mutant with regard to triphosphatase expression of both herpes simplex virus serotypes. After shift-up from permissive to nonpermissive temperature, triphosphatase activity in cells infected with ts9 decreased rapidly, whereas all other mutants continued to exhibit enzyme levels comparable with controls kept at the permissive temperature. The type 1-specific nuclear expression of the triphosphatase was mapped physically by the use of HSV-1 x HSV-2 intertypic recombinants, based on enzyme levels different by more than two orders of magnitude found in nuclei of HSV-1- and HSV-2-infected cells. The locus for the type-specific expression maps between 0.67 and 0.68 fractional length on the HSV genome.