Functions of glycoprotein G of herpes simplex virus type 2

Background: Herpes simplex virus type 2 (HSV-2) is a common sexually transmitted infection with more than 500 million individuals infected world-wide. A major global health problem is that HSV-2 infection facilitates the spread of HIV. This epidemiological situation warrants the development of a vaccine to reduce the spread of HSV-2. As HSV-2 often is transmitted without symptoms type specific serology is valuable in diagnosis of the infection. The envelope glycoprotein G (gG-2) of HSV-2 is cleaved intracellularly into a membrane bound portion (mgG-2) and a secreted portion (sgG-2). Although the function of mgG-2 is unknown the protein induces a type specific antibody response. This feature is utilized in several serological HSV-2 type specific assays. A general problem is that assays which are reliable in Western world country populations show lower performance for sera from African countries. Aims: To evaluate sgG-2 as type specific antigen in ELISA for detection of HSV-2 infection in a Swedish cohort and define the performance for both sgG-2 and mgG-2 in ELISA for high HSV-2 prevalence cohorts in Tanzania (paper I and II). To elucidate the function of mgG-2, using HSV-2 mutants, in a genital mouse model (paper III) and to evaluate mgG-2 as a vaccine candidate against genital HSV-2 infection in mice (paper IV). Methods: Natively produced sgG-2 and mgG-2 proteins were purified by immunosorbent columns from HSV-2 infected cell cultures. For the vaccine studies mgG-2 was purified using Helix pomatia lectin affinity chromatography. A frame shift HSV-2 mutant devoid of mgG-2 and an emerald green fluorescent protein labelled sgG-2 and mgG-2 negative HSV-2 were used for functional studies in C57BL/6 mice. Viral load was estimated by virus isolation and by real time PCR. C57BL/6 mice were immunized with mgG-2 and CpG as adjuvant and challenged genitally with wild type HSV-2. Results: We showed that sgG-2 is a novel antigen that can be used for type specific serological diagnosis of HSV-2 infection and that an ELISA based on mgG-2 can improve the detection of HSV-2 infected individuals from Africa. Both mgG-2 deficient HSV-2 mutants were severely attenuated and all mice survived a genital infection. The viral mutants infected the genital mucosa but did not induce genital disease and were not propagated to the sensory ganglia or to the CNS. Finally, mice immunized with mgG-2 and adjuvant were highly protected against a lethal dose of wild type HSV-2. Protection was associated with an enhanced Th1 response and IFN-γ production in re-stimulated CD4+ T cells. Conclusion: Native sgG-2 and mgG-2 proteins induce type specific antibody responses and perform well in ELISA in low as well as in high HSV-2 prevalence populations. The mgG-2 protein has an important function in the ability of HSV-2 to infect nervous tissue. As vaccination with mgG-2 protects mice from lethal disease mgG-2 constitutes a promising vaccine candidate against HSV-2 infection. In human trials detection of anti-sgG-2 antibodies may be a valuable tool to discriminate between vaccine induced immunity and natural HSV-2 infections

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

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 ≥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

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

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

Seroprevalences of Herpes Simplex Virus Type 2, Five Oncogenic Human Papillomaviruses, and Chlamydia trachomatis in Katowice, Poland▿

Herpes simplex virus type 2 (HSV-2), human papillomaviruses (HPVs), and Chlamydia trachomatis are the most common pathogens causing sexually transmitted infections (STIs). There is limited information about the prevalences of these STIs in Poland. Here, we estimated the occurrence of immunoglobulin G (IgG) antibodies against HSV-2, HPV, and C. trachomatis in 199 blood donors and 110 patients of both genders attending an STI clinic in Katowice in southern Poland. The seroprevalences of HSV-2 were 5% for blood donors and 14% in the STI cohort. The seroprevalences of the five potentially oncogenic HPV types 16, 18, 31, 35, and 51 were 15%, 7%, 5%, 5%, and 17%, respectively, in blood donors and 37%, 8%, 12%, 5%, and 21%, respectively, in the STI cohort. The majority of HPV-infected individuals showed antibodies against more than one type, i.e., had been infected with multiple HPV types. Anti-C. trachomatis IgG antibodies were detected in 6% of blood donors and 13% of individuals attending the STI clinic. The relatively high prevalence of HPV-51 may have implications for future vaccine programs, as the newly introduced HPV vaccines are based on the potentially oncogenic HPV types 16 and 18