Indirect ELISA for the detection of HSV-2 specific IgG and IgM antibodies with glycoprotein G (gG-2)

Management of oral herpes simplex virus infections: The problem of resistance. A narrative review

Herpes Simplex Virus (HSV) type 1 (HSV-1) and type 2 (HSV-2) are among the most common human viral pathogens, affecting several billion people worldwide. Although in healthy patients clinical signs and symptoms of HSV infection are usually mild and self-limiting, HSV-infections in immunocompromised patients are frequently more aggressive, persistent, and even life-threatening. Acyclovir and its derivatives are the gold standard antiviral drugs for the prevention and treatment of HSV infections. Although the development of acyclovir resistance is a rather uncommon condition, it may be associated with serious complications, especially in immunocompromised patients. In this review, we aim to address the problem of drug resistant HSV infection and discuss the available alternative therapeutic interventions. All relative studies concerning alternative treatment modalities of acyclovir resistant HSV infection published in PubMed between 1989 to 2022 were reviewed. Long-term treatment and prophylaxis with antiviral agents predisposes to drug resistance, especially in immunocompromised patients. Cidofovir and foscarnet could serve as alternative treatments in these cases. Although rare, acyclovir resistance may be associated with severe complications. Hopefully, in the future, novel antiviral drugs and vaccines will be available in order to avoid the existing drug resistance.

Cross protective efficacy of the Non-Neurotropic live attenuated herpes simplex virus type 1 vaccine VC-2 is enhanced by intradermal vaccination and deletion of glycoprotein G

Herpes simplex virus type 1 and 2 (HSV-1 and HSV-2 respectively) cause life-long latent infections resulting in recurrent orofacial and genital blisters or sores. Ensued disease can be painful and may lead to significant mental anguish of infected individuals. Currently, there are no FDA-approved vaccines for either prophylactic or therapeutic use, and recent clinical trials of subunit vaccines failed to achieve endpoints goals. Development of a safe live-attenuated herpes simplex vaccine may provide the antigenic breadth to ultimately protect individuals from acquiring HSV disease. We have previously shown that prophylactic use of the non-neurotropic live attenuated HSV-1 vaccine, VC-2, provides potent and durable protection from genital HSV-2 disease in the guinea pig model. Here, we investigated the effects of intradermal administration as well as the deletion of the viral glycoprotein G (gG) on the efficacy of prophylactic vaccination. Vaccination with either VC-2, VC-2 gG null, or gD2 MPL/Alum offered robust protection from acute disease regardless of route of vaccination. However, both the VC-2 gG-null and the ID vaccination route were more effective compared to the parent VC2 administered by the IM route. Specifically, the VC-2 gG-null administered ID, reduced HSV-2 vaginal replication on day 2 and day 4 as well as mean recurrent lesion scores more effectively than VC2 administered IM. Most importantly, only VC-2 gG null IM and VC-2 ID significantly reduced the frequency of recurrent shedding, the most likely source for virus transmission. Similarly, while all vaccinated groups demonstrated a significant reduction in the number of animals testing PCR-positive for HSV-2 in their dorsal root ganglia following challenge only VC2 ID vaccinated animals demonstrated a significant reduction in DRG viral load. All vaccinations induced neutralizing antibodies to HSV-2 MS when compared to unvaccinated guinea pigs. Therefore, further investigation of VC-2 gG null delivered ID is warranted.

Characterization of Serum Samples With Discordant Results in 2 Herpes Simplex Virus Type 2 IgG Assays

BACKGROUND

Our laboratory system tests sera for herpes simplex virus type 2 (HSV-2) IgG using the DiaSorin Liaison chemiluminescent immunoassay (CIA), with the option to confirm positive samples by a laboratory-developed HerpeSelect inhibition assay. As part of the confirmation process, the HerpeSelect HSV-2 IgG enzyme immunoassay (EIA) is performed. This study investigated the relationship between DiaSorin HSV-2 IgG CIA-positive indices and HerpeSelect HSV-2 IgG EIA results.

METHODS

HerpeSelect HSV-2 IgG EIA results were compiled for a cohort of consecutive DiaSorin HSV-2 IgG CIA-positive (index ≥1.10) samples. To further characterize DiaSorin CIA-positive samples that were positive (concordant) or negative (discordant) by the HerpeSelect EIA, a separate composite reference study panel was constructed and also tested using the Biokit HSV-2 IgG assay and an HSV-2 IgG inhibition assay developed for the DiaSorin instrument. Samples were classified as DiaSorin HSV-2 IgG true positive or false positive based on a composite reference using HerpeSelect EIA, Biokit, and DiaSorin inhibition results.

RESULTS

Of 2305 consecutive DiaSorin HSV-2 IgG CIA-positive samples, 411 (17.8%) were HerpeSelect HSV-2 IgG EIA negative; 343 of 411 (83%) had DiaSorin indices of 1.10 to 3.00. For the composite reference study panel (N = 120), 59 of 60 discordant samples were classified as DiaSorin HSV-2 IgG false positive based on the composite reference, whereas 58 of 60 concordant samples were classified as true positive.

CONCLUSIONS

Nearly all DiaSorin HSV-2 IgG CIA-positive but HerpeSelect HSV-2 IgG EIA-negative sera are falsely positive in the DiaSorin CIA. Furthermore, most DiaSorin false-positive samples exhibit low-positive indices, suggesting that guidelines for confirmatory testing should include low-positive samples by CIA and EIA.

Diagnosis of Herpes Simplex Virus: Laboratory and Point-of-Care Techniques

Herpes is a widespread viral infection caused by the herpes simplex virus (HSV) that has no permanent cure to date. There are two subtypes, HSV-1 and HSV-2, that are known to cause a variety of symptoms, ranging from acute to chronic. HSV is highly contagious and can be transmitted via any type of physical contact. Additionally, viral shedding can also happen from asymptomatic infections. Thus, early and accurate detection of HSV is needed to prevent the transmission of this infection. Herpes can be diagnosed in two ways, by either detecting the presence of the virus in lesions or the antibodies in the blood. Different detection techniques are available based on both laboratory and point of care (POC) devices. Laboratory techniques include different biochemical assays, microscopy, and nucleic acid amplification. In contrast, POC techniques include microfluidics-based tests that enable on-spot testing. Here, we aim to review the different diagnostic techniques, both laboratory-based and POC, their limits of detection, sensitivity, and specificity, as well as their advantages and disadvantages.

The variability of the serological response to SARS-corona virus-2: Potential resolution of ambiguity through determination of avidity (functional affinity)

Data on the serological response toward severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in 16 recent reports were analyzed and a high degree of variability was shown. Immunoglobulin M (IgM) responses were either found earlier than IgG, or together with IgG, later than IgG, or were missing. Therefore, clear distinctions between early, intermediate, and past infections are obviously not possible merely on the basis of IgM and IgG determinations. A review of publications on the serology of other virus groups shows that variable IgM responses can be found as well and therefore are not unique for SARS‐CoV‐2 infections. A model to explain this variability is proposed. The inclusion of avidity determination into regular diagnostic procedures has allowed to resolve such “atypical” serological constellations. The potential use of avidity determination for the diagnosis of COVID‐19, for risk assessment, epidemiological studies, analysis of cross reactions, as well as for the control of vaccination programs is suggested and discussed.

The serological response to SARS CoV‐2 infection is highly variable.

The mere detection of specific IgM and IgG does not allow to distinguish between acute and past infection.

The variable IgM and IgG responses after SARS CoV‐2 infection are analogous to serological findings in other virus systems.

Variable IgM and IgG responses can be rationally explained by models that describe immunoglobulin production by the immune system.

Avidity determination of SARS CoV‐2 IgG is suggested for resolution of diagnostic ambiguity.

Characterization of polyclonal antibodies to Herpes Simplex Virus types 1 and 2

Infections with herpes simplex virus (HSV) types 1 and 2 have been linked to oral, facial, genital lesions, as well as some visceral organ changes in patients under immunosuppressed conditions. Immunohistochemistry (IHC) with HSV antibodies is used for identification of the viruses in tissue samples. In this study, two polyclonal antibodies, prepared separately with HSV-1 and HSV-2 immunogens, were characterized in comparison to a monoclonal antibody to HSV-1 (10A3). The polyclonal anti-HSV-1 and monoclonal antibody 10A3 were shown to be reactive to viral proteins of both HSV-1 and HSV-2 on Western blots, while the polyclonal anti-HSV-2 was reactive to HSV-2 proteins, but not to those of HSV-1. Cross-reactivity was not observed to proteins of six other frequently encountered herpes viruses. IHC characterization was performed on 29 cases of HSV-infected tissue samples, 61 samples infected with other herpes viruses and 35 samples without known infection. By IHC, the polyclonal anti-HSV-1 and a monoclonal antibody 10A3 exhibited a signal, mainly in a nuclear pattern, in all of the HSV-infected samples and not in other tissue types. A positive signal, mainly in the cytoplasm, was identified with the polyclonal anti-HSV-2 in 21 of the 29 HSV-infected samples. Genotyping analysis was successful in 14 of the HSV-infected samples, with IHC HSV-2 positivity correlative to the HSV-2 genotype. The results demonstrate that these antibodies are useful tools for identification of HSV-1 and HSV-2, and their combinatorial application may help to distinguish between these two types of infection.

Herpes simplex virus type 2 (HSV-2) IgG index values in two immunoassays in relation to HSV-2 IgG inhibition assay results

CDC guidelines recommend confirmatory testing of sera with low-positive indices (1.10-3.50) in the HerpeSelect® (HSLT) HSV-2 IgG screening assay. To determine if this recommendation is adequate for our patient population, we reviewed HSLT HSV-2 IgG screening indices for 262 screen-positive sera (index >1.10) tested in our confirmatory assay, which assesses inhibition of binding to recombinant gG2 by HSV-1- and HSV-2-infected cell lysates. To determine how the recommendation affects other screening assays, we tested these samples in the Liaison® HSV-2 IgG assay. Of 124 false-positive sera, 20% and 39% had an index >3.50 in the HSLT and Liaison screening assays, respectively. In both assays, 51% of 63 indeterminate sera (inhibition by HSV-1 lysate) had indices >3.50. Similarly, ≥75% of 75 true-positive samples exhibited indices >3.50 in both assays. Thus, confirmatory testing only of sera with low-positive HSV-2 IgG indices misses some false-positive and indeterminate samples, leading to misdiagnosis of HSV-2 infection.

Expression and characterization of the soluble form of recombinant mature HSV-2 glycoprotein G for use in anti-HSV-2 IgG serodiagnostic immunoassay

Herpes simplex virus type-2 (HSV-2) specific glycoprotein G (gG-2) is widely used as the antigen of choice for serodiagnosis of HSV-2. In order to develop an ELISA for serodetection of HSV-2 IgG in patient sera, the soluble form of the mature gG-2 antigen (mgG-2), gG283-649, was expressed using a baculovirus expression system. gG283-649 contains the complete extracellular domain of mgG-2 including the C-terminal region, which despite homology to gG-1, does not cross-react with HSV-1 antibodies present in HSV-1 positive patient sera. gG283-649 had increased performance compared to a previously described gG-2 fragment and showed high sensitivity and specificity in a method comparison with HerpeSelect 1 & 2 Immunoblot IgG, a commercially available FDA-cleared assay for serodetection of HSV-1 and 2 antibodies. A total of 234 clinical samples consisting of 134 high risk samples, including 45 samples from pregnant subjects, and a panel of 100 mixed diagnosis samples, spanning the measurable range were tested in the method comparison. Clinical sensitivity and specificity were determined to be 94.2% and 100%, respectively. We conclude that this soluble form of mgG-2 is a novel antigen of choice for developing an ELISA for type-specific serodiagnosis of HSV-2.

Vaccination with the Secreted Glycoprotein G of Herpes Simplex Virus 2 Induces Protective Immunity after Genital Infection

Herpes simplex virus 2 (HSV-2) infects the genital mucosa and establishes a life-long infection in sensory ganglia. After primary infection HSV-2 may reactivate causing recurrent genital ulcerations. HSV-2 infection is prevalent, and globally more than 400 million individuals are infected. As clinical trials have failed to show protection against HSV-2 infection, new vaccine candidates are warranted. The secreted glycoprotein G (sgG-2) of HSV-2 was evaluated as a prophylactic vaccine in mice using two different immunization and adjuvant protocols. The protocol with three intramuscular immunizations combining sgG-2 with cytosine-phosphate-guanine dinucleotide (CpG) motifs and alum induced almost complete protection from genital and systemic disease after intra-vaginal challenge with HSV-2. Robust immunoglobulin G (IgG) antibody titers were detected with no neutralization activity. Purified splenic CD4+ T cells proliferated and produced interferon-γ (IFN-γ) when re-stimulated with the antigen in vitro. sgG-2 + adjuvant intra-muscularly immunized mice showed a significant reduction of infectious HSV-2 and increased IFN-γ levels in vaginal washes. The HSV-2 DNA copy numbers were significantly reduced in dorsal root ganglia, spinal cord, and in serum at day six or day 21 post challenge. We show that a sgG-2 based vaccine is highly effective and can be considered as a novel candidate in the development of a prophylactic vaccine against HSV-2 infection.

Anti-glycoprotein g antibodies of herpes simplex virus 2 contribute to complete protection after vaccination in mice and induce antibody-dependent cellular cytotoxicity and complement-mediated cytolysis

We investigated the role of antibodies against the mature portion of glycoprotein G (mgG-2) of herpes simplex virus 2 (HSV-2) in protective immunity after vaccination. Mice were immunized intramuscularly with mgG-2 and oligodeoxynucleotides containing two CpG motifs plus alum as adjuvant. All C57BL/6 mice survived and presented no genital or systemic disease. High levels of immunoglobulin G subclass 1 (IgG1) and IgG2 antibodies were detected and re-stimulated splenic CD4+ T cells proliferated and produced IFN-γ. None of the sera from immunized mice exhibited neutralization, while all sera exerted antibody-dependent cellular cytotoxicity (ADCC) and complement-mediated cytolysis (ACMC) activity. Passive transfer of anti-mgG-2 monoclonal antibodies, or immune serum, to naive C57BL/6 mice did not limit disease progression. Immunized B‑cell KO mice presented lower survival rate and higher vaginal viral titers, as compared with vaccinated B-cell KO mice after passive transfer of immune serum and vaccinated C57BL/6 mice. Sera from mice that were vaccinated subcutaneously and intranasally with mgG-2 presented significantly lower titers of IgG antibodies and lower ADCC and ACMC activity. We conclude that anti-mgG-2 antibodies were of importance to limit genital HSV‑2 infection. ADCC and ACMC activity are potentially important mechanisms in protective immunity, and could tentatively be evaluated in future animal vaccine studies and in clinical trials.

Comparative performance of a novel herpes simplex virus type 2-specific enzyme-linked immunosorbent assay using a targeted chain oligopeptide, peptide 55

Herpes simplex virus (HSV) glycoprotein G (gG2) has been used as the basis of many serological assays for the detection of HSV type 2 (HSV-2)-specific antibodies. In the present study, an enzyme-linked immunosorbent assay (ELISA), the Pathozyme Viro HSV-2 immunoglobulin G (IgG) ELISA (Omega Diagnostics, Alva, United Kingdom), based on an immunodominant epitope of gG2 presented in a branched-chain format (peptide 55), was compared with two commercially available gG2-specific assays, the Bioelisa HSV-2 IgG assay (Biokit, S.A., Barcelona, Spain) and the HerpesSelect HSV-2 IgG assay (Focus Diagnostics, Cypress, CA). A panel of 218 well-characterized serum samples was tested. Thirty-one samples were determined to be HSV-2 IgG antibody positive and 164 samples were determined to be negative with all three kits. The levels of concordance between the tests were 95.9% between the Omega and HerpeSelect assays, 90.8% between the Omega and Bioelisa assays, and 94.5% between the HerpeSelect and Bioelisa assays. Twenty-three samples gave discordant results. Western blot results showed that of these, the results for 77% were correctly identified by the Omega assay, the results for 68% were correctly identified by the HerpeSelect assay, and the results for 13.6% were correctly identified by the Bioelisa assay. Although there was a high level of agreement between the results obtained by the three assays and no false-positive results were detected by any of the three kits, confirmation of the results for samples with discordant results by Western blotting suggested that the peptide 55-based Omega assay is the most sensitive and specific assay among the assays evaluated.

Discrimination of antibody to herpes B virus from antibody to herpes simplex virus types 1 and 2 in human and macaque sera

The antigenic cross-reactive characteristics of herpes B virus and herpes simplex virus (HSV) type 1 (HSV-1) and HSV-2 are responsible for false-positive diagnoses by serological assays in humans and macaques. In the present study, we developed a fluorometric indirect enzyme-linked immunosorbent assay (ELISA) with recombinant herpes B virus glycoprotein D (gD) and HSV-1 and HSV-2 gG (gG-1 and gG-2, respectively) to discriminate between the three primate herpesvirus infections. The secreted form of gD, gDdTM, was used to detect antibody to herpes B virus gD. Sera positive for herpes B virus, HSV-1, and HSV-2 showed specific reactions to gD, gG-1, and gG-2, respectively. Sera collected from humans and rhesus macaques were investigated for the presence of antibodies to the recombinant proteins of the three herpesviruses. The results suggested that the approach is able to discriminate between herpes B virus and HSV infections. The ELISA was also found to be able to detect infections with multiple primate herpesviruses and may have the potential to identify a subsequent infection in individuals that have already been infected with another herpesvirus. In addition, we found evidence of a greater cross-reactivity of herpes B virus with HSV-1 than with HSV-2. It is suggested that the ELISA with the recombinant antigens is useful not only for the serodiagnosis of primate herpesvirus infections but also for elucidation of the seroprevalence of herpesviruses in humans and primates.

Herpes simplex virus type 2 (HSV-2) infection in women attending an antenatal clinic in the South Pacific island nation of Vanuatu

OBJECTIVE

The objective of this study was to estimate the prevalence and correlates of herpes simplex virus type 2 infection in women in an antenatal clinic in the South Pacific island nation of Vanuatu.

STUDY DESIGN

A prevalence survey of sexually transmitted infections of pregnant women attending an antenatal clinic at Vila Central Hospital was conducted in 1999-2000. Serum samples were tested for HSV-1 and HSV-2 antibodies by enzyme-linked immunosorbent assay. Results for other sexually transmitted infections and demographic and obstetric variables were analyzed for their association with HSV-2 serostatus.

RESULTS

HSV-2 serum antibody results were obtained on 535 women and HSV-1 results on 134. The seroprevalence of HSV-2 was 30% and HSV-1 was 100%. On multivariate analysis, the independent predictors of HSV-2 infection were age, marital status, and trichomoniasis.

CONCLUSIONS

HSV-2 was common in this sample of sexually active women in Vanuatu. This is the first study of HSV in Vanuatu and one of very few studies in the Pacific region.

Interactions and management issues in HSV and HIV coinfection

Significant synergistic interactions have been observed between HIV and herpes simplex virus (HSV). HIV-induced immune compromise can cause frequent and persistent HSV disease, while poorly controlled HSV replication may influence HIV pathogenicity and transmission. HSV-2 seroprevalence is high in HIV-infected cohorts worldwide, with rates of over 80% for HSV-1 and ranging from 33% to more than 80% for HSV-2. As seen in HIV-negative individuals, HSV-2 coinfection is associated with female gender, older age and black ethnicity. HSV infection is commonly under-diagnosed in HIV-infected individuals, although the use of PCR for HSV detection in mucocutaneous swabs and HSV type-specific serology can improve the diagnostic yield. In HIV-1-infected patients with frequent clinical episodes of HSV reactivation, suppressive antiviral therapy may prove beneficial in controlling HSV disease while also reducing HSV-mediated promotion of HIV replication. Antiretroviral therapy leads to a gradual recovery of HSV-specific T-cell responses and a reduction in HSV-related morbidity, indicating that successful management of coinfection should target both HIV and HSV replication. The aim of this review is to address the more speculative issues surrounding the management of HSV/HIV coinfection and to summarize the data that inform them.

Prevalence of antibodies against herpes simplex virus types 1 and 2 in children and young people in an urban region in Tanzania

Herpes simplex virus type 1 (HSV-1) is transmitted by close contact, both sexual and nonsexual, and infections are acquired during childhood and adolescence. Herpes simplex virus type 2 (HSV-2), however, is thought to be transmitted mainly by sexual contact. Most HSV-2 infections are consequently expected to occur after the onset of sexual activity. Recent reports indicate an increasing prevalence of HSV-2 on the African continent, but most studies have been performed on adult cohorts. In the present study, we collected sera from Tanzanian children and young persons from 1 to 20 years old, with at least 100 individuals in each age group. Antibodies against HSV-1 and HSV-2 were detected by an in-house Western blot method which was shown to perform well in comparison with a commercial Western blot assay. Type-specific antibodies were also analyzed by two noncommercial enzyme-linked immunosorbent assay methods based upon the antigenicities of branched synthetic oligopeptides corresponding to epitopes in glycoprotein G of HSV-1 or HSV-2. The prevalence of HSV-1 antibodies increased gradually from 73% for the age group of 1 to 4 years to 92% for the age group of 17 to 20 years. The prevalence of HSV-2 antibodies was unexpectedly high, as 15% of the children were infected by the age of 8 years, with the incidence increasing gradually to 40% in the age group of 17 to 20 years. The reason for this unexpectedly high frequency is not clear but could suggest that nonsexual transmission of HSV-2 is more common than previously thought. There was no statistically significant association between seropositivities for HSV-2 and human immunodeficiency virus.

Mature glycoprotein g presents high performance in diagnosing herpes simplex virus type 2 infection in sera of different tanzanian cohorts

Herpes simplex virus type 2 (HSV-2) is a common sexually transmitted infection in sub-Saharan Africa. Glycoprotein G (gG) of HSV-2 elicits a type-specific antibody response and is widely used for serodiagnosis. gG is cleaved into a secreted portion (sgG-2) and a highly O-glycosylated mature portion (mgG-2). The performances of these two native immunosorbent purified antigens were compared in an enzyme-linked immunosorbent assay (ELISA) format with a commercially available assay (FOCUS2) using sera from blood donors (n = 194) and individuals (n = 198) with genital ulcer disease (GUD) from Tanzania. Discordant results were resolved by Western blotting. The HSV-2 seroprevalence for blood donors was estimated as 42%, and that for the GUD cohort was estimated as 78%. The prevalence increased significantly with age for both cohorts and was higher among human immunodeficiency virus (HIV)-positive individuals than among HIV-negative subjects. In the GUD cohort with a high HSV-2 prevalence, all three assays showed statistically similar performances, with sensitivities between 97% and 99% and specificities in the range of 86% to 91%. In contrast, among blood donors with a lower seroprevalence, the mgG-2-based ELISA presented significantly higher specificity (97%) than the sgG-2 ELISA (89%) and FOCUS2 (74%). Overall, the mgG-2 ELISA gave a high performance, with negative and positive predictive values of 96% for blood donors and a negative predictive value of 95% and a positive predictive value of 97% for the GUD cohort. We conclude that native purified mgG-2 showed the highest accuracy for detection of HSV-2 in patient sera from Tanzania and is therefore suitable for seroprevalence studies as well as in clinical settings.

Performance of a novel test for IgM and IgG antibodies in subjects with culture-documented genital herpes simplex virus-1 or -2 -infection

Novel tests (BioPlex) for herpes simplex virus-1 (HSV-1) and HSV-2 IgG were compared with HerpeSelect HSV-1 and HSV-2 ELISAs for type-specific IgG. The sensitivity and specificity of BioPlex HSV-1 IgG were 94% (84/89) and 96% (119/124), respectively, with unselected sera, while the sensitivity and specificity of BioPlex HSV-2 IgG were 92% (109/118) and 98% (95/97), respectively. BioPlex IgM was compared with Diamedix IgM against sera from patients with culture-documented genital herpes. The test results were concordant in 81% of sera from HSV-1 patients and in 90% of sera from HSV-2 patients. Use of BioPlex IgM in addition to BioPlex IgG tests increased HSV-2 seroconversion detection from 47% of subjects to 70%. Use of Diamedix IgM in addition to Focus IgG ELISA increased HSV-2 detection from 40% of subjects to 70%. IgM was detected by BioPlex in 63% of sera from patients with early HSV-2 infection (< 30 days) and in 59% of sera by Diamedix. IgM was also detected in a large proportion of sera from subjects with established HSV-2 infection (33% by BioPlex and 29% by Diamedix). Addition of IgM testing substantially increased the ability to detect seroconversion early in infection. IgM is an indicator of recent infection only in subjects who lack detectable IgG.

A branched, synthetic oligopeptide corresponding to a region of glycoprotein G of HSV-1 reacts sensitively and specifically with HSV-1 antibodies in an ELISA

Herpes simplex viruses types 1 and 2 (HSV-1 and HSV-2), which are common worldwide, are so similar that antibodies directed against one serotype may crossreact with antigens from the other one. Methods for specific detection of antibodies against HSV-1 or HSV-2 are based upon the antigenicities of glycoproteins G. However, due to the cost, the available commercial methods may not readily be used in developing countries. A different enzyme-linked immunosorbent assay (ELISA) method, based upon a synthetic oligopeptide corresponding to an immunogenic region in glycoprotein G of HSV-2, has been used recently and successfully for detection of HSV-2 antibodies. In the present study, the sequences of a newly identified immunogenic and type-specific region in glycoprotein G of HSV-1 was used to synthesize three different, branched oligopeptides. The performances of these peptides in an ELISA were investigated by testing Scandinavian and African sera which were characterized by commercial ELISA and Western blotting methods and divided into four groups either lacking HSV antibodies, containing antibodies against one or the other virus, or against both types. The peptide which corresponded in sequence to the immunodominant region was as specific and sensitive by an ELISA as were the commercial methods. The method is inexpensive and reliable.

HSV type specific serology in sexual health clinics: use, benefits, and who gets tested

OBJECTIVES

To determine which sexual health clinic clients were tested for herpes simplex virus (HSV) type specific antibodies and whether this test was useful for patient management.

METHODS

Demographic, sexual and reproductive history, reasons for performing type specific serology, results, and benefits were derived from patient records from Parramatta Sexual Health Clinic for all patients who were tested between 13 September1993 and 31 December 2001. The value of serology was defined under five categories-diagnostic, counselling, initiating suppressive antiviral therapy, pregnancy counselling, and not useful. To establish whether patients tested for HSV were representative of clinic attendees, a sex matched "control" group was randomly selected.

RESULTS

382/886 (43.1%) were HSV-2 antibody positive and 774/884 (80.8%) were HSV-1 positive. The commonest reasons for requesting serology were having a partner with genital herpes (30%), undiagnosed recurrent genital ulceration (26%), and first episode of genital ulceration (22%). The test was of value in confirming the diagnosis in 57% of men and 60% of women with recurrent genital ulceration and in 28% of men and 40% of women with first episode genital herpes. In patients with a partner with genital herpes the test was of value in making a diagnosis in 27% men and 50% of women and in counselling 50% of women and 73% of men. Patients offered serology were older and more likely to have had genital herpes in the past than controls.

CONCLUSION

Type specific serology should be recommended for the management of couples where one has genital herpes and the other apparently does not and in individuals with genital complaints suggestive of herpes.

Secreted portion of glycoprotein g of herpes simplex virus type 2 is a novel antigen for type-discriminating serology

The secreted portion of glycoprotein G (sgG-2) of herpes simplex virus type 2 (HSV-2) was evaluated as a novel antigen in an enzyme-linked immunosorbent assay (ELISA) format for detection of type-specific immunoglobulin G (IgG) antibodies in HSV-2-infected patients. The results were compared with those obtained by a commercially available assay, the HerpeSelect 2 ELISA (the FOCUS2 assay). Five different panels of sera were analyzed: panel A consisted of 109 serum samples from patients with a culture-proven HSV-1 infection that were Western blotting (WB) negative for HSV-2; panel B consisted of 106 serum samples from patients with a culture-proven recurrent HSV-2 infection that were WB positive for HSV-2; panel C consisted of 100 serum samples with no detectable IgG antibodies against HSV-1 and HSV-2; panel D consisted of 70 HSV-2 negative "tricky" serum samples containing antinuclear IgG antibodies or IgM antibodies against other viruses or bacteria; and panel E consisted of consecutive serum samples from 21 patients presenting with a first episode of HSV-2-induced lesions. When sera in panels A to C were analyzed, the sgG-2 ELISA and the FOCUS2 assay both showed sensitivities and specificities of >or=98%. In total, among the samples in panel D, 13 serum samples (19%) were false positive by the FOCUS2 assay and 1 serum sample (1.4%) was false positive by the sgG-2 ELISA. When the sera in panel E were analyzed, the sgG-2 ELISA detected seroconversion somewhat later than WB or the FOCUS2 assay did. We conclude that sgG-2 induces an HSV-2 type-specific antibody response and can be used for type-discriminating serology.

Is HSV serology useful for the management of first episode genital herpes?

BACKGROUND

First episode genital herpes simplex virus (HSV) infections can be classified into three groups, primary genital herpes (no previous exposure to HSV), non-primary first episode (IgG antibody to HSV of the non-presenting type), and first episode with pre-existing IgG HSV antibodies. The use of IgM to classify first episode genital herpes has not been evaluated.

OBJECTIVE

To evaluate the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of HSV-1 and HSV-2 IgM antibodies for the diagnosis of first episode genital herpes, when compared with clinical diagnosis.

METHODS

Patients with a first clinical episode of genital herpes were recruited. Sera were tested for IgG antibodies to HSV-2 using an indirect enzyme linked immunosorbent assay (ELISA). Equivocal results were resolved by western blot. HSV-1 IgG and IgM and HSV-2 IgM antibodies were detected using western blot.

RESULTS

157 patients were recruited. 31 were excluded (missing data or no detectable antibodies and negative viral isolation). Therefore, 126 patients were included in the analysis. 23 (18.3%) had primary genital herpes, 34 (27.0%) non-primary first episode, and 69 (54.8%) had pre-existing genital herpes. The specificity and PPV of HSV IgM was 100%; the sensitivity was 79% and the NPV 85%.

CONCLUSION

IgM HSV serology may be useful in the management of some patients with first episode genital herpes and provide an indication of the source of infection. Drawbacks include the low sensitivity and NPV, lack of availability, IgM antibodies may occasionally be produced in response to recurrent infection and, finally, IgM antibodies may take up to 10 days to develop and last 7-10 days.

Performance characteristics of a glycoprotein G based oligopeptide (peptide 55) and two different methods using the complete glycoprotein as assays for detection of anti-HSV-2 antibodies in human sera

Assays for serological diagnosis of HSV-2 infection in clinical settings have been generally available only recently. We wanted to investigate and compare the diagnostic utility of three different ELISAs for detection of anti-HSV-2 IgG antibodies, using intact glycoprotein G or an oligopeptide from a portion of the protein as antigens. HSV-1 negative/HSV-2 negative sera (n = 32), HSV-1 positive/HSV-2 negative sera (n = 30) and sera from HSV-2 culture positive individuals (n = 36), collected at least 6 months after culture verified HSV-2 genital infection were examined. Cut-off values were determined according to the manufacturer's instructions, and also by establishing new cut-off values at the level of highest diagnostic efficiency. Sensitivities and specificities were compared for each assay. In addition, test accuracies were compared using receiver-operating characteristics (ROC) methodology. Establishment of new cut-off values increased the performance characteristics for all three tests. At similarly set cut-off values, the peptide 55 assay showed the highest diagnostic sensitivity (100%) and specificity (98%). All three assays displayed high efficiency and also high agreement between the tests (kappa > 0.85 for all comparisons). The performance of all three assays were satisfactory although the highest efficiency and accuracy was obtained with the peptide 55 assay.

Herpes simplex virus type-2 infection in pregnancy: no risk of fetal death: results from a nested case-control study within 35,940 women

OBJECTIVE

The aim of this study was to assess the association of fetal death with herpes simplex virus type-2 (HSV-2) antibody status during pregnancy: 1. presence of antibodies in first trimester; 2. appearance of antibodies (incident infection); 3. increase in antibody titre; and 4. loss of antibodies.

DESIGN

Prospective study.

POPULATION

The source population was a cohort of 35,940 pregnant women in Norway.

METHODS

Nested case-control study within the cohort. Cases were all women in the study population who experienced a fetal death after the 16th weeks of gestation (n = 281), and controls were 961 randomly selected women with a live born child.

MAIN OUTCOME MEASURES

HSV-2 antibody status.

RESULTS

Twenty-nine percent (82/281) of women with a fetal death and 27% (256/961) of the controls had of HSV-2 antibodies present in the first trimester (odds ratio 1.1, 95% CI 0.8-1.5). HSV-2 antibodies appeared in 2% (3/136) of initially seronegative cases and 3% (16/623) of the controls during pregnancy (odds ratio 0.9, 95% CI 0.2-3.0). An increase in HSV-2 antibodies occurred in 4% (2/55) of initially seropositive cases and 7% (16/231) of the controls (odds ratio 0.5, 95% CI 0.1-2.3). Loss of HSV-2 antibodies in initially seropositive women was not associated with fetal death, 42% (23/55) of the cases and 45% (104/231) of the controls seroreverted (odds ratio 0.8, 95% CI 0.5-1.6). Differences in follow up time, age and parity were controlled and did not influence the comparisons between cases and controls.

CONCLUSION

This study provides no evidence of an association between HSV-2 infection during pregnancy and fetal death.

Detection of HSV-2 in genital ulcers from STD patients in Dar es Salaam, Tanzania

BACKGROUND

Genital ulcer disease (GUD) is common in many developing countries. Several reports indicate that there is an association with HIV infection. Analysis by polymerase chain reaction (PCR) has demonstrated that the ulcers are frequently caused by herpes simplex type 2 (HSV-2), although HSV-1 is becoming increasingly important in many parts of the world. Comparable studies have not been performed in Tanzania.

OBJECTIVES

To determine the prevalence of HSV-2 and HSV-1 in genital ulcers in Dar es Salaam, Tanzania and determine their possible association with HIV infection.

STUDY DESIGN

Samples were collected from 70 consecutive patients with GUD attending a clinic for sexually transmitted diseases. Specimens from ulcers were analysed by PCR for the presence of HSV-2 and HSV-1, and sera were examined for antibodies against HSV-2 and HIV.

RESULTS AND DISCUSSION

HSV-2 DNA was detected in 64% of the specimens from ulcers while HSV-1 DNA was not found in any of them. Antibodies to HSV-2 and HIV were detected in 79.7 and 42% of the patients' sera, respectively. Although there was a significant positive association between HIV and HSV-2 seropositivity, HSV-2 DNA in genital ulcers was not more prevalent among HIV seropositive than among HIV seronegative individuals.

CONCLUSION

The prevalence of HSV-2 antibodies among Tanzanian patients with genital ulcers is very high, and HSV-2 is detected in most of the ulcers. There is an association between infections with HIV and HSV-2, but the relationship is not clear.

Evaluation of confirmatory strategies for detection of type-specific antibodies against herpes simplex virus type 2

In this study, the optimal combination of three commercial glycoprotein G-2 (gG-2)-based herpes simplex virus type 2 (HSV-2) type-specific enzyme-linked immunosorbent assays (Euroimmun anti-HSV-2 immunoglobulin G [IgG] ELISA [Eu2], Gull HSV-2-specific IgG ELISA [Gu2], and Radim HSV-2 IgG ELISA [Ra2]) and one gG-2-based HSV-2-specific immunoblot (Euroimmun anti-HSV-1/HSV-2 gG Western blot [EuW]) was determined with regard to diagnostic performance and cost efficiency. Two hundred fifty serum samples were included in this study, 194 of which were from female prostitutes. When a formal primary "gold standard" was defined based on majority agreement of the commercial tests, with EuW being decisive in stand-off situations, the sensitivity and specificity of the assays in the samples from prostitutes were as follows: Eu2, 100 and 89.22%; Gu2, 94.44 and 96.08%; Ra2, 61.18 and 95.10%; and EuW, 98.90 and 100%. The most cost-effective confirmatory strategy in the samples from prostitutes was screening with Eu2, retesting positive and equivocal samples with Gu2, and resolving the remaining discordant results with EuW (estimated additional costs per sample, 79.02%; sensitivity, 100%; positive predictive value, 96.81%). Applying a self-developed gG-2-independent assay to the discordant and concordant negative samples in the samples from prostitutes suggested that the primary gold standard may have missed six HSV-2-positive samples. In conclusion, confirmatory strategies based on commercial gG-2-dependent seroassays result in an increase in the specificity of HSV-2-specific serology. However, further improvement of the sensitivity of current HSV-2-specific serology may require the additional exploitation of the gG-2-independent type-specific antibody response.

Monoclonal antibodies and human sera directed to the secreted glycoprotein G of herpes simplex virus type 2 recognize type-specific antigenic determinants

Glycoprotein G-2 (gG-2) of herpes simplex virus type 2 (HSV-2) is cleaved to a secreted amino-terminal portion (sgG-2) and to a cell-associated carboxy-terminal portion which is further O-glycosylated to constitute the mature gG-2 (mgG-2). In contrast to mgG-2, which is known to elicit a type-specific antibody response in the human host, information on the immunogenic properties of sgG-2 is lacking. Here the sgG-2 protein was purified on a heparin column and used for production of monoclonal antibodies (mAbs). Four anti-sgG-2 mAbs were mapped using a Pepscan technique and identified linear epitopes which localized to the carboxy-terminal part of the protein. One additional anti-sgG-2 mAb, recognizing a non-linear epitope, was reactive to three discrete peptide stretches where the most carboxy-terminally located stretch was constituted by the amino acids (320)RRAL(323). Although sgG-2 is rapidly secreted into the cell-culture medium after infection, the anti-sgG-2 mAbs identified substantial amounts of sgG-2 in the cytoplasm of HSV-2-infected cells. All of the anti-sgG-2 mAbs were HSV-2 specific showing no cross-reactivity to HSV-1 antigen or to HSV-1-infected cells. Similarly, sera from 50 HSV-2 isolation positive patients were all reactive to sgG-2 in an enzyme immunoassay whilst no reactivity was seen in 25 sera from HSV-1 isolation positive patients or in 25 serum samples from HSV-negative patients suggesting that sgG-2 is a novel antigen potentially suitable for type-discriminating serodiagnosis.

Sexual and demographic risk factors for herpes simplex type 1 and 2 in women attending an antenatal clinic

OBJECTIVE

To establish risk factors for the presence of HSV-2 and HSV-1 infections in pregnant women. DESIGN, POPULATION, AND SETTING: A prospective study of 3306 women attending the antenatal department Westmead Hospital, Sydney, between June 1995 and April 1998.

METHODS

Women completed a self administered questionnaire to establish risk factors for the presence of HSV-2 and HSV-1. Sera were tested for antibodies to HSV-2 and HSV-1. Data were analysed using SPSS and SAS.

MAIN OUTCOME MEASURES

Seroprevalence of and risk factors for HSV-2 and HSV-1.

RESULTS

375 (11.3% (95% CI 10.3-12.5)) women were HSV-2 antibody positive. Increasing age, Asian country of birth, lower education level, public hospital status, confirmed genital herpes, a partner with genital herpes, early age of first sex, more than one lifetime sexual partner, and previous chlamydia infection were independently associated with HSV-2 seropositivity. Of 408 women tested for HSV-1 antibodies, 323 (79.2% (95% CI 74.9-83.0)) were positive. Oral herpes, oral blisters or sores, and being HSV-2 seropositive were independently associated with HSV-1 seropositive status. When the logistic regression model was rerun without HSV-2 status, parity of two or more and one or more sexual partners in the past 3 months were significant predictors of HSV-1 seropositivity.

CONCLUSIONS

The presence of antibodies to HSV-2 and HSV-1 is related to a number of sexual and demographic risk factors. Public health campaigns directed at encouraging young people to delay the onset of sexual activity and reduce the number of sexual partners need to be evaluated. However, the possible availability of an HSV-2 vaccine that is able to protect over 70% of women offers the best hope for control of genital herpes.

Is preeclampsia an infectious disease?

BACKGROUND

Studies have suggested a strong paternal factor in the etiology of preeclampsia. If preeclampsia is caused by an infectious agent transmitted by the woman's partner, seronegative women who may experience primary infection in pregnancy should be at increased risk of preeclampsia as compared to previously infected women. The aim of this study was to assess the impact of being seronegative for some viruses transmitted by close contact on the risk of developing preeclampsia.

METHODS

Nine hundred and seventy-eight women were randomly drawn from a basic study population of 35,940 pregnant women in Norway. A serum sample drawn at the first antenatal visit was analyzed for specific IgG antibodies against herpes simplex virus type-2, cytomegalovirus and Epstein-Barr virus. For comparison, antibody status against Toxoplasma gondii was also assessed. Information on preeclampsia in pregnancy was obtained through linkage to the Medical Birth Registry of Norway.

RESULTS

Thirty-three (3%) women developed preeclampsia. The risk of developing preeclampsia seemed to be increased for women who were seronegative for the viruses studied. Seronegativity for Toxoplasma gondii did not show such a pattern.

INTERPRETATION

Women who are seronegative for antibodies against viral agents transmitted through close contact seem more likely to develop preeclampsia. This finding indicates that women who are seronegative to such agents may acquire primary infection in pregnancy, and subsequently be at increased risk of preeclampsia. This hypothesis could represent a new approach to the causes of preeclampsia, and encourage search for yet unidentified microbes as a possible causal factor.

Rising incidence and prevalence of herpes simplex type 2 infection in a cohort of 26 year old New Zealanders

OBJECTIVES

To examine changes in the incidence and prevalence of herpes simplex type 2 (HSV-2) infection in a birth cohort of 26 year old New Zealanders in whom seroprevalence had been measured at 3.4% at age 21.

METHODS

Sera from 869 cohort members were tested using an indirect IgG enzyme linked immunoassay specific to the HSV-2 glycoprotein G. Serological results were compared with detailed sexual histories.

RESULTS

In all, 96 participants (11%) were seropositive for HSV-2, including at least 56 who seroconverted after their 21st birthday. Among those known to be seronegative at age 21, the annual seroconversion rate was 13.5 cases per 1000 per year, compared with 8.1 cases per 1000 per sexually active year before age 21. New infections were associated with female sex and an early age of first intercourse. The average rate of partner change was lower in the cohort after age 21, and was only modestly increased among those who acquired new HSV-2 infections between ages 21 and 26.

CONCLUSIONS

HSV-2 seroprevalence has risen sharply in this sexually active cohort, despite a reduction in the overall level of partner change. Increased rates of HSV-2 acquisition after age 21 may be due to a higher prevalence of infection in the pool of potential partners encountered during the third decade of life. Factors related to partner choice may have more influence on the risk of HSV-2 infection than the number of sexual partners alone.

Sorting out the new HSV type specific antibody tests

This review will delineate performance characteristics and limitations, as far as they are known, of the new glycoprotein G based, type specific HSV serologies. Several of these tests have been FDA approved in the United States for use in adults. With the departure of Gull/Meridian from the HSV serology market, it is important for clinicians to understand the sources and claims of the remaining type specific tests. Moreover, inaccurate tests using crude antigen preparations remain on the market. These tests are identified based on product insert information provided by company representatives.

Conservation of type-specific B-cell epitopes of glycoprotein G in clinical herpes simplex virus type 2 isolates

Glycoprotein G (gG-2) of herpes simplex virus type 2 (HSV-2) is cleaved to a secreted amino-terminal portion and to a cell-associated, heavily O-glycosylated carboxy-terminal portion that constitutes the mature gG-2 (mgG-2). The mgG-2 protein is commonly used as a type-specific antigen in the serodiagnosis of HSV-2 infection. As the amino acid sequence variability of mgG-2 in clinical isolates may affect the performance of such assays, the gG-2 gene was sequenced from 15 clinical HSV-2 isolates. Few mutations were identified, and these were mostly localized outside the epitope regions described earlier. Five isolates were identical to different laboratory strains, indicating that the gG-2 gene is highly conserved over time. In the search for HSV-2 isolates harboring mutations within the immunodominant region of mgG-2, a pool of 2,400 clinical HSV-2 isolates was tested for reactivity with two anti-mgG-2 monoclonal antibodies (MAbs). Ten MAb escape HSV-2 mutants, which all harbored structurally restricted single- or dual-point mutations within the respective epitopes explaining the loss of binding, were identified. Sera from corresponding patients were reactive to mgG-2, as well as to a peptide representing the immunodominant region, suggesting that the point mutations detected did not diminish seroreactivity to mgG-2. The conservation of the gG-2 gene reported here further supports the use of mgG-2 as a type-specific antigen in the diagnosis of HSV-2 infections.

Neonatal herpes prevention: a minor public health problem in some communities

BACKGROUND

Neonatal herpes is a condition with high morbidity and mortality. The greatest risk occurs when the mother acquires herpes simplex virus (HSV) towards the end of pregnancy. A study from Seattle has suggested that the risk of acquisition of HSV during pregnancy was 3.7%. In Australia, HSV-2 infection is less common in pregnant women than in the United States. Consequently we conducted a study to establish HSV seroprevalence and the rate of HSV seroconversion in this population.

METHODS

The study was conducted at Westmead Hospital, Sydney, between June 1995 and April 1998. Women completed a questionnaire covering risk factors for the acquisition of genital herpes. A serum sample during pregnancy and a specimen of cord blood were obtained and tested for antibodies to HSV-2 using a type specific indirect enzyme linked immunosorbent assay (ELISA). Equivocal results were resolved by western blot. A subset of the paired sera was tested for antibodies to HSV-1. The data were analysed using SPSS.

RESULTS

326 of the 2616 (12.5%) women were HSV-2 seropositive. Three women (0.15%) acquired HSV-2 infection during pregnancy. None of the three babies of these mothers developed neonatal herpes. 416 maternal cord pairs were tested for HSV-1 antibodies and 330 (79.3%) were positive. No HSV-1 seroconversions occurred.

CONCLUSIONS

In this population, HSV acquisition was uncommon (0.34% per year) and neonatal herpes was rare. A cost effective analysis suggested that type specific serology to screen pregnant women and their partners in low prevalence communities was not cost effective.

Peptide based enzyme-linked immunoassays for detection of anti-HSV-2 IgG in human sera

Glycoprotein G of HSV-2 (gG2) and a peptide, corresponding to a previously recognised immunodominant epitope spanning residues 561-578 of the protein, were compared directly for type-specific serodiagnosis of HSV-2. The protein was affinity purified and obtained in a commercially available EIA kit while the peptide, previously designated as peptide 55, was made as a multiple antigenic peptide. A panel of 100 characterised serum samples (60 HSV-2 positive, 20 HSV-1 positive and 20 HSV negative) was screened using the two antigens. The intact protein and peptide 55 showed the same sensitivity for antibodies in the serum of HSV-2 infected individuals, reacting with 96.7% (58/60) of the samples. The peptide did not react with any of the HSV-1 positive or HSV negative sera. In contrast, gG2 gave a number of false positive results, reacting with 20% (4/20) of the HSV-1 positive sera and 10% (2/20) of the HSV negative sera. The superior performance of peptide 55, together with the very much lower costs of its production, compared with gG2 suggest that the peptide will become the antigen of choice in enzyme immunoassays for type-specific serodiagnosis of HSV-2.

First episodes of genital herpes in a Swedish STD population: a study of epidemiology and transmission by the use of herpes simplex virus (HSV) typing and specific serology

OBJECTIVES

To determine the proportion of herpes simplex virus type 1 (HSV-1) and HSV type 2 (HSV-2) in first episodes of genital herpes. To evaluate the use of HSV specific serology for classifying first episodes of genital herpes and for defining HSV serostatus in the patients' sexual partners.

METHODS

108 consecutive patients with first episodes of genital herpes seen at three STD clinics in Sweden from 1995 to 1999 were included in the study. HSV culture and typing were performed and serum was tested for antibodies against a type common HSV antigen and a type specific HSV-2 antigen, glycoprotein G2 (gG2). A structured interview including questions about sexual behaviour and sexual partners was taken. "Steady" partners were offered a blood test for HSV serology and counselling.

RESULTS

Of 108 patients, 11 had a negative HSV culture. Of the 97 who were HSV culture positive, 44% (43/97) were typed as HSV-1 and 56% (54/97) as HSV-2. For 86 of these 97 patients, HSV serology from the initial visit was available. Of 52 primary infections, thus initially seronegative, 64% were HSV-1 infections and of 19 female primary infections 16 (84%) were HSV-1. In 17% the first episode of genital herpes corresponded to the first clinical recurrence of an infection acquired earlier in life. There was a significant correlation between having orogenital sex and being infected with HSV-1 and also a history of labial herpes in the partner. Only 20% of partners of patients with an HSV-2 infection had a history of genital herpes.

CONCLUSIONS

Almost half of first episodes of genital herpes are caused by HSV-1. In young women with a primary genital infection, HSV-1 is much more frequent than HSV-2. Besides HSV typing, we found specific HSV serology of value for classifying first episodes and for diagnosing a subclinical HSV-2 infection in partners. Anamnestic data supported the suggestion that the orogenital route of transmission was common in genital HSV-1 infections.

A monoclonal blocking EIA for herpes simplex virus type 2 antibody: validation for seroepidemiological studies in Africa

A competitive type-specific enzyme-linked immunosorbent assay (ELISA) for herpes simplex virus type 2 (HSV-2) antibody was developed using an infected cell antigen and a monoclonal antibody to glycoprotein G-2. This assay has been validated for use for epidemiological studies using a large panel of sera collected in rural Uganda and a panel of 143 sera characterised previously by Western blotting, the 'gold standard' for HSV type-specific serology. This evaluation was found to have a sensitivity of 96% and a specificity of 91% in comparison with Western blot on 143 sera from clinic patients. The ELISA had a sensitivity of 93% and a specificity of 91% in comparison with Western blot on 495 sera collected in Uganda. The assay showed good reproducibility and a low percentage of sera gave equivocal results, indicating its suitability for epidemiological studies.

Detection of human serum antibodies against type-specifically reactive peptides from the N-terminus of glycoprotein B of herpes simplex virus type 1 and type 2 by surface plasmon resonance

A single-step surface plasmon resonance protocol for the detection of antibodies against herpes simplex virus type 1 and type 2 (HSV-1, HSV-2) in human sera was established using the BIAcore system. Two peptides from corresponding segments of the N-terminus of HSV-1 and HSV-2 glycoprotein B (gB), i.e. peptide gB-1 (60-73) (GAAPTGDPKPKKNK) and peptide gB-2 (55-68) (SPATTKARKRKTKK), were identified as immunogenic. Employing both peptides as diagnostic antigens in the surface plasmon resonance assay, a sensitivity for the detection of HSV-1 and HSV-2 type-specific antibodies of 83 and 86%, respectively, was achieved as compared with immunoblotting as a reference method. Peptide gB-1 (60-73) allowed the discrimination between HSV-1 and HSV-2 type-specific antibodies with a specificity of 67%, whereas peptide gB-2 (55-68) reacted in a strictly HSV-2 type-specific manner. It is concluded that peptides from the N-terminus of gB-1 and gB-2 are recognized predominantly by human sera in an HSV-specific manner. Peptide gB-2 (55-68) can be employed successfully for the determination of type-specific antibodies against HSV-2.

Glycoprotein G of herpes simplex virus type 1: identification of type-specific epitopes by human antibodies

Serological diagnosis of herpes simplex virus (HSV) infections requires assays based on antigens that expose type-specific determinants. This study was designed to outline the B-cell epitopes of the type-specific glycoprotein G-1 (gG-1) of HSV type 1 (HSV-1), by investigating the reactivity of human anti-gG-1 antibodies, purified from 21 HSV-1-isolation-proven patient sera, to cellulose-bound synthetic peptides spanning the entire gG-1 sequence. The epitope mapping demonstrated that these antibodies bound preferentially to antigenic determinants that localized to regions with a high degree of amino acid similarity to the corresponding glycoprotein in HSV-2, gG-2. In spite of this, the purified anti-gG-1 antibodies were found to be non-reactive to native gG-2 antigen, as well as to overlapping gG-2 peptides, thus supporting the role of gG-1 as a prototype HSV-1 type-specific antigen. One immunodominant region, delimited by amino acids 112-127, reacted with all purified anti-gG-1 antibodies and may be of interest for the further development of a peptide-based HSV-1 type-specific seroassay.

Evaluation of an enzyme immunoassay system for measuring herpes simplex virus (HSV) type 1-specific and HSV type 2-specific IgG antibodies

MRL Diagnostics has developed a dual enzyme immunoassay (EIA) system that employs the recombinant Herpes Simplex Virus (HSV) type-specific glycoproteins G1 (HSV1) and G2 (HSV2) to detect HSV type-specific IgG antibodies. This system was evaluated using 155 consecutive sera previously tested in a conventional dual EIA system (Zeus) that employs multiple HSV1 and HSV2 proteins to detect type-common as well as type-specific antibodies. Sera were also analyzed by Western blot to determine the true HSV type-specific IgG reactivity pattern. Of 110 sera giving concordant reactivity patterns in the MRL and Zeus EIA systems, 108 (98%) also displayed concordant Western blot patterns; two sera gave false positive HSV2 reactivity in both EIA systems. Of 45 sera giving discordant MRL and Zeus EIA reactivity patterns, 41 (91%) displayed a Western blot reactivity pattern that matched the MRL reactivity pattern. Both the HSV1 IgG component and the HSV2 IgG component of the MRL EIA system were 100% sensitive and > 95% specific. In contrast, the Zeus HSV1 IgG EIA was 98% sensitive and 79% specific, and the Zeus HSV2 IgG EIA was 85% sensitive and 79% specific. An analysis of the distribution of index values in the MRL EIA system showed that low-positive values (1.0-3.0) were rare, but, when detected, often represented false positive results; only 11 MRL low-positive results were observed, but all 6 MRL false positive results were found within this low-positive subgroup. These findings show that the MRL dual EIA system effectively detects HSV type-specific IgG antibodies.

Whole cell lysate enzyme immunoassays vs. recombinant glycoprotein G2-based immunoassays for HSV-2 seroprevalence studies

Seroepidemiology studies of herpes simplex virus type 2 (HSV-2) infections have been difficult to carry out because antibodies to HSV type 1 (HSV-1) show an extensive cross-reactivity with HSV-2 antigens. Many kits available currently are not entirely type specific for serodiagnosis of HSV-2 infections and therefore do not allow reliable discrimination of past exposure to these closely related alphaherpes viruses. Attempts to develop type-specific antigens have focused on the envelope glycoproteins, particularly glycoprotein G (gG). A cross-sectional study was carried out to examine the seroprevalence of antibodies to HSV-2 among healthy university students, using different methods: a whole cell lysate enzyme-linked immunosorbent assay (ELISA), two different ELISAs, and a newly developed immunoblot assay, the last three based on recombinant gG2. HSV-2 prevalence was 24 times higher with the whole cell lysate ELISA (31%; 95% confidence interval [CI]: 27-35%) than the ELISAs and the immunoblot assay based on recombinant gG2 (1.3%; 95% CI: 0.1-2.5%), thus showing the inaccuracy of commercial tests based on whole-antigen preparations for epidemiological studies. Laboratories should be cautious and ensure that commercial tests for HSV typing are based on type-specific glycoproteins.

Herpes simplex virus type 2 glycoprotein G-negative clinical isolates are generated by single frameshift mutations

Herpes simplex virus (HSV) codes for several envelope glycoproteins, including glycoprotein G-2 (gG-2) of HSV type 2 (HSV-2), which are dispensable for replication in cell culture. However, clinical isolates which are deficient in such proteins occur rarely. We describe here five clinical HSV-2 isolates which were found to be unreactive to a panel of anti-gG-2 monoclonal antibodies and therefore considered phenotypically gG-2 negative. These isolates were further examined for expression of the secreted amino-terminal and cell-associated carboxy-terminal portions of gG-2 by immunoblotting and radioimmunoprecipitation. The gG-2 gene was completely inactivated in four isolates, with no expression of the two protein products. For one isolate a normally produced secreted portion and a truncated carboxy-terminal portion of gG-2 were detected in virus-infected cell medium. Sequencing of the complete gG-2 gene identified a single insertion or deletion of guanine or cytosine nucleotides in all five strains, resulting in a premature termination codon. The frameshift mutations were localized within runs of five or more guanine or cytosine nucleotides and were dispersed throughout the gene. For the isolate for which a partially inactivated gG-2 gene was detected, the frameshift mutation was localized upstream of but adjacent to the nucleotides coding for the transmembranous region. Thus, this study demonstrates the existence of clinical HSV-2 isolates which do not express an envelope glycoprotein and identifies the underlying molecular mechanism to be a single frameshift mutation.

Variability of the glycoprotein G gene in clinical isolates of herpes simplex virus type 1

Glycoprotein G (gG) of herpes simplex virus type 1 (HSV-1) has been used as a prototype antigen for HSV-1 type-specific serodiagnosis, but data on the sequence variability of the gene coding for this protein in wild-type strains are lacking. In this study, direct DNA sequencing of the gG-1 genes from PCR products was performed with clinical HSV-1 isolates from 11 subjects as well as with strains Syn 17(+), F, and KOS 321. The reference strains Syn 17(+) and F showed a high degree of conservation, while KOS 321 carried 13 missense mutations and, in addition, 12 silent mutations. Three clinical isolates showed mutations leading to amino acid alterations: one had a mutation of K(122) to N, which is a gG-1-to-gG-2 alteration; another contained all mutations which were observed in KOS 321 except two silent mutations; and the third isolate carried five missense mutations. Two clinical isolates as well as strain KOS 321 showed a mutation (F(111)-->V) within the epitope of a gG-1-reactive monoclonal antibody (MAb). When all viruses were tested for reactivity with the anti-gG-1 MAb, the three strains with the F(111)-->V mutation were found to be unreactive. Furthermore, gG-1 antibodies purified from sera from the two patients carrying strains mutated in this epitope were less reactive when they were tested by an HSV-1-infected-cell assay. Therefore, our finding that the sequence variability of the gG-1 gene also affects B-cell epitope regions of this protein in clinical isolates may have consequences for the use of this protein as a type-specific antigen for serodiagnosis.

Changes in prevalence of herpes simplex virus type 1 and 2 antibodies from 1973 to 1993 in the rural districts of Japan

Using the gG-capture ELISA, changes in the seroprevalence of HSV-1 and HSV-2 from 1973 to 1993 were studied for 614 sera collected from general adults living in rural Japan. The HSV-1 seroprevalence for men and women decreased from 75.3 and 80.6% in 1973 to 54.4 and 59.6%, respectively, in 1993. The HSV-2 seroprevalence also decreased from 10.2 and 9.9% in 1973 to 1.8 and 1.2%, respectively, in 1993. Although the decrease in HSV-2 prevalence seemed to be correlated with the general decrease of sexually transmitted diseases in Japan since the 1950s, these findings should not be interpreted as typical, as HSV-2 infections are particularly known to distribute unevenly among populations, according to sexual activity and cohorts.

Ability of a rapid serology test to detect seroconversion to herpes simplex virus type 2 glycoprotein G soon after infection

Sera (n = 188) from 29 patients with first-episode genital herpes simplex virus type 2 (HSV-2) infections were tested by POCkit-HSV-2 and Western blot (WB) to determine the speed of seroconversion. The median time to detection of HSV-2 antibody was 13 days (range, 3 to 102 days) by the POCkit-HSV-2 test versus 13 days (range, 2 to 58 days) for WB.

Evaluation of three glycoprotein G2-based enzyme immunoassays for detection of antibodies to herpes simplex virus type 2 in human sera

Three new glycoprotein G-based enzyme immunoassays (ETI-HSVK-G 2, Sorin Diagnostics Biomedica [assay A]; HSV Type 2 Specific IgG ELISA, Gull Laboratories, Inc. [assay B]; Cobas Core HSV-2 IgG EIA, Roche [assay C]) for the detection of herpes simplex virus (HSV) type 2 (HSV-2)-specific antibodies were evaluated. By testing sera from 25 individuals with culture-proven HSV-2 infection, the assays showed a sensitivity of 96%. The specificities, evaluated with sera from 70 HSV antibody-negative children, 75 HSV antibody-positive children, and 69 HSV antibody-negative adults, were 100% for assay A, 96.2% for assay B, and 97.8% for assay C, respectively. Discrepant results by any of the three assays, i.e., reactivity of a specimen in only one or two assays, occurred with similar frequencies for HSV-seronegative individuals as well as HSV-seropositive children and adults. For sera with discrepant results, the positive reactivity was mostly low. Thus, for determination of the prevalence of HSV-2 antibodies, only concordantly positive results were considered. On the basis of the results obtained with sera from 41 adults with culture-proven HSV-1 infection and from 173 HSV-antibody-positive pregnant women, the HSV-2 seroprevalence was 9. 8%. The results show that the new glycoprotein G2-based enzyme immunoassays are useful tools for the detection of type-specific HSV-2 antibodies. However, if only one assay is performed, careful interpretation of the results is indicated, especially if the exhibited reactivity is low, and for determination of the definitive HSV-2 serostatus, confirmatory assays may still be necessary.

The use of peptides from glycoproteins G-2 and D-1 for detecting herpes simplex virus type 2 and type-common antibodies

BACKGROUND

identification and discrimination of latent herpes simplex virus (HSV) infection relies on antibody identification. The inclusion of synthetic peptides with HSV glycoproteins provides means for stable and discriminatory assays for population studies.

OBJECTIVE

to determine whether virus-specific synthetic peptides might identify HSV type 2 (HSV-2) antibodies in the presence of the cross-reactive and more common HSV type 1 (HSV-1) antibodies.

STUDY DESIGN

the capacity of synthetic peptides as HSV antigens was analyzed in enzyme immunoassay (EIA) using well characterized human serum cohorts. The HSV peptide assays were evaluated in comparison with two commercial HSV-2 assays.

RESULTS

a combination of two C-terminal HSV-1 glycoprotein D (gD-1) peptides detected type-common HSV immunoglobulin G (IgG) with high sensitivity (95%) and specificity (93%). Peptides derived from the C-terminus of HSV-2 glycoprotein G (gG-2) had a high HSV-2 type-specificity. Inclusion of both gD-1 and gG-2 peptides gave a sensitivity for human anti-HSV-2 IgG that was similar to that of assays including different amounts of native gG-2. With western blotting as a standard, the sensitivity of the peptide assay ranged between 86% for HSV-2 seropositive persons and 61% for HSV-2 seroconverters. Addition of a small amount of native gG-2 to the peptide assay tended to increase the specificity.

CONCLUSION

HSV gG and gD peptides show promise as type-specific and type-common HSV antigens. These peptides are more stable and reproducibly prepared than native or recombinant glycoproteins and may be considered for inclusion in future HSV serodiagnostic assays.

Kaposi's sarcoma-associated herpesvirus: a sexually transmissible infection?

We examined sexual behavior as a risk factor for Kaposi's sarcoma-associated herpesvirus (KSHV) infection and examined the relation between KSHV seropositivity and development of KS in cross-sectional and cohort studies of 130 homosexual men diagnosed with AIDS in Sydney, Australia during the period from 1991 to 1993. KSHV serology was measured using antibody tests to latency-associated nuclear antigen (LANA) and lytically expressed open reading frame (ORF) 65.2. In the cross-sectional analysis, 52% (68) of study subjects were KSHV-seropositive by either assay. KSHV-seropositive men were significantly more likely to be seropositive to both herpes simplex type 2 (odds ratio [OR] 3.0; 95% confidence interval [CI], 1.2-7.5 for LANA and OR 2.8; 95% CI, 1.3-6.0 for ORF 65) and hepatitis A virus (OR 2.2; 95% CI, 1.1-4.5 for ORF 65). KSHV-seropositive men reported nonsignificantly more casual sexual partners and were nonsignificantly more likely to report insertive oroanal contact with casual partners. These data suggest that KSHV might be sexually transmitted among homosexual men. Men were observed until October 1996 for development of KS. Those seropositive to either KSHV assay at baseline were more likely than the seronegative to develop KS during follow-up (rate ratio [RR] 4.4; 95% CI, 1.9-10.2). Of those seropositive for KSHV, 53% developed KS.