Comparison of antibody and antigen response to intranasal and intramuscular EHV-1 modified-live vaccination in healthy adult horses

During neurological EHV-1 outbreaks, modified-live vaccines (MLV) are often administrated intranasally in an off-label fashion to healthy cohort horses in order to achieve rapid mucosal immunity. Thus, the goal of the present study was to determine if a commercially available EHV-1 MLV given intranasally to healthy horses would trigger a measurable systemic and/or mucosal antibody response. Eight healthy adult horses were given the EHV-1 MLV vaccine intranasally, while 8 healthy adult horses received the vaccine intramuscularly. An additional 8 healthy horses served as unvaccinated controls. EHV-1 specific antibodies (total IgG, IgG4/7, IgG1 and IgA) were measured in blood and nasal secretions prior to vaccine administration and 14- and 30-days post-vaccine administration. Further, nasal secretions and whole blood were tested for the presence of EHV-1 DNA by qPCR prior to and 5 days after vaccine administration. EHV-1 was detected by qPCR for the first 48 hours post-intranasal vaccine administration in nasal secretions in a total of three horses. Total EHV-1 IgG and IgG4/7 antibody values in serum increased only in horses receiving the intramuscular MLV. Antibody values at 14- and 30-days post vaccine administration were not different from values prior to vaccine administration in horses receiving the intranasal vaccine. The results support the intramuscular use of the EHV-1 MLV as recommended by the manufacturer. Intranasal vaccination with the study-specific EHV-1 MLV did not induce an increase in systemic or nasal antibodies, therefore, this vaccine route seems suboptimal and should not be used to vaccinate adult horses that have received multiple EHV-1 vaccinations and have pre-existing antibodies against EHV-1.

Immune and inflammatory response in horse vaccinated against equine herpesviruses 1 (EHV-1) and 4 (EHV-4) assessed by serum protein electrophoretic pattern and leukocyte population

Protection against infectious diseases can be obtained with vaccines generating immunogenic response through a combination of humoral and cellular immunity. In this study haematological and serum protein electrophoretic profiles of horses vaccinated against herpesvirus 1 (EHV-1) and 4 (EHV-4) were evaluated. Blood samples were collected from 16 horses before (T0), after 24h, 48h, 72h, 1st week, 2nd week and 3rd week (T1I, T2I, T3I, T7I, T14I and T21I) from the first EHV vaccine-dose administration as well as before (TPRE_II), and after 24h, 48h, 72h, 1st week, 2nd week, 3rd week and 4th week (T1II, T2II, T3II, T7II, T14II, T21II and T28II) from the EHV vaccine-booster. Total leukocyte values increased at T1I, T1II, T3II and T28II compared to T0 (P<0.01). Higher lymphocytes and lower neutrophils values were found after first vaccine-dose and vaccine-booster administration compared to the T0 (P<0.01). Monocytes showed higher values at T14II than T0 (P<0.01). Higher serum values of total proteins, α1-, α-2-, β1-, β2- and γ-globulins were found in horses after first vaccine-dose and vaccine-booster administration (P<0.01). Gathered results suggest that horses vaccinated against EHV1 and EHV-4 exhibited a dynamic change of WBC, lymphocytes, neutrophils and monocytes. Moreover, the analysis of serum electrophoresis pattern suggested that EHV vaccination induced the development of inflammation and antibody response in vaccinated horses as highlighted by the increase of α-, β- and γ-globulin fractions. These changes probably reflect the systemic immunological adaptation of animals to EHV vaccine.

The herpevac trial for women: Sequence analysis of glycoproteins from viruses obtained from infected subjects

The Herpevac Trial for Women revealed that three dose HSV-2 gD vaccine was 58% protective against culture-positive HSV-1 genital disease, but it was not protective against HSV-2 infection or disease. To determine whether vaccine-induced immune responses had selected for a particular gD sequence in strains infecting vaccine recipients compared with viruses infecting control subjects, genetic sequencing studies were carried out on viruses isolated from subjects infected with HSV-1 or HSV-2. We identified naturally occurring variants among the gD sequences obtained from 83 infected subjects. Unique or low frequency amino acid substitutions in the ectodomain of gD were found in 6 of 39 HSV-1-infected subjects and in 7 of 44 HSV-2-infected subjects. However, no consistent amino acid change was identified in isolates from gD-2 vaccine recipients compared with infected placebo recipients. gC and gE surround and partially shield gD from neutralizing antibody, and gB also participates closely in the viral entry process. Therefore, these genes were sequenced from a number of isolates to assess whether sequence variation may alter protein conformation and influence the virus strain’s capacity to be neutralized by vaccine-induced antibody. gC and gE genes sequenced from HSV-1-infected subjects showed more variability than their HSV-2 counterparts. The gB sequences of HSV-1 oral isolates resembled each other more than they did gB sequences rom genital isolates. Overall, however, comparison of glycoprotein sequences of viral isolates obtained from infected subjects did not reveal any singular selective pressure on the viral cell attachment protein or surrounding glycoproteins due to administration of gD-2 vaccine.

The challenge of vaccinating adults: attitudes and beliefs of the Canadian public and healthcare providers

OBJECTIVES

Vaccine coverage for recommended vaccines is low among adults. The objective of this study was to assess the knowledge, attitudes, beliefs and behaviours of adults and healthcare providers related to four vaccine-preventable diseases and vaccines (diphtheria-tetanus-pertussis, zoster, pneumococcus and influenza).

DESIGN

We undertook a survey and focus groups of Canadian adults and healthcare providers (doctors, nurses, pharmacists). A total of 4023 adults completed the survey and 62 participated in the focus groups; 1167 providers completed the survey and 45 participated in the focus groups.

RESULTS

Only 46.3% of adults thought they were up-to-date on their vaccines; 30% did not know. In contrast, 75.6% of providers reported being up-to-date. Only 57.5% of adults thought it was important to receive all recommended vaccines (compared to 87.1-91.5% of providers). Positive attitudes towards vaccines paralleled concern about the burden of illness and confidence in the vaccines, with providers being more aware of disease burden and confident in vaccine effectiveness than the public. Between 55.0% and 59.7% of adults reported willingness to be vaccinated if recommended by their healthcare provider. However, such recommendations were variable; while 77.4% of the public reported being offered and 52.8% reported being recommended the influenza vaccine by their provider, only 10.8% were offered and 5.6% recommended pertussis vaccine. Barriers and facilitators to improved vaccine coverage in adults, such as trust-mistrust of health authorities, pharmaceutical companies and national recommendations, autonomy versus the public good and logistical issues (such as insufficient time and lack of vaccination status tracking), were identified by both the public and providers.

CONCLUSIONS

Despite guidelines for adult vaccination, there are substantial gaps in knowledge and attitudes and beliefs among both the public and healthcare providers that lead to low vaccine coverage. A systematic approach that involves education, elimination of barriers and establishing and improving infrastructure for adult immunisation is required.

Immunology in the Clinic Review Series; focus on host responses: T cell responses to herpes simplex viruses

Herpes virus infections are chronic and co-exist with acquired immune responses that generally prevent severe damage to the host, while allowing periodic shedding of virus and maintenance of its transmission in the community. Herpes simplex viruses type 1 and 2 (HSV-1, HSV-2) are typical in this regard and are representative of the viral subfamily Alphaherpesvirinae, which has a tropism for neuronal and epithelial cells. This review will emphasize recent progress in decoding the physiologically important CD8(+) and CD4(+) T cell responses to HSV in humans. The expanding data set is discussed in the context of the search for an effective HSV vaccine as therapy for existing infections and to prevent new infections.

New viral vaccines

Vaccination is the most effective medical intervention against diseases caused by human viral pathogens. Viral vaccines prevent or modify the severity of illness in the individual and interrupt or reduce the transmission of the pathogens to other susceptible people. Through these mechanisms, vaccines against smallpox, polio, measles and hepatitis B have had an enormous impact on world health over the last 50 years. Advances in basic virology and understanding of human immunity promise more progress in the control of human viral diseases as the 21st century begins. Some important targets, including human immunodeficiency virus, respiratory syncytial virus and hepatitis C virus present challenges that require more basic research. The purpose of this review is to highlight four new viral vaccines that have recently, or will soon demonstrate the effective translation of basic investigations into clinical benefits for disease control in healthy and high-risk populations. These vaccines include the live attenuated vaccines against the RNA viruses, rotavirus and influenza A and B, and vaccines against human papilloma virus and varicella-zoster virus, which are DNA viruses that cause morbidity and mortality through their capacity to establish persistent infection. Although only the influenza vaccine has been licensed in the United States, these other new tools for disease prevention are likely to be introduced within the next few years, with profound effects on the diseases that they cause. Hence, as Virology celebrates its 50th anniversary, it is appropriate to examine these examples of recent advances in viral vaccines.

The epidemiology of varicella and herpes zoster in The Netherlands: implications for varicella zoster virus vaccination

We studied the epidemiology of varicella (chickenpox) and herpes zoster (shingles) in The Netherlands to assess the desirability to implement routine varicella zoster virus vaccination in The Netherlands. Data on seroprevalence of varicella zoster virus in the general population (1995-1996), consultations of general practitioners for varicella (2000-2002) and herpes zoster (1998-2001) and hospital admissions due to varicella (1994-2001) and herpes zoster (1994-2001) in The Netherlands were analysed. The seropositivity increased sharply with age from 18.4% for both 0- and 1-year-olds, to 48.9%, 59.0%, 75.7% and 93.0% for 2-, 3-, 4- and 5-year-olds, respectively, and varied between 97.5% and 100% for older age groups. The average annual incidence of GP-consultations amounted to 253.5 and 325.0 per 100,000 for varicella and herpes zoster, respectively. The incidence of hospital admission due to varicella and herpes zoster was 1.3 (2.3 including side diagnosis) and 2.7 (5.8) per 100,000, respectively. Whilst for varicella, the incidence of GP-consultations and hospital admissions were highest in childhood, for herpes zoster, these were highest in elderly. Insight into epidemiology of varicella zoster is needed for the assessment of the desirability of introduction of routine varicella zoster vaccination.

[Dermatology]

We are going over therapeutic acquisitions in a club-journal including relevant publications in different fields: mecanism of action, therapeutic perspectives in a near future, and side effects.

A live attenuated glycoprotein E negative bovine herpesvirus 1 vaccine induces a partial cross-protection against caprine herpesvirus 1 infection in goats

Taking into account the close antigenic relationship between bovine herpesvirus 1 (BoHV-1) and caprine herpesvirus 1 (CpHV-1), a live attenuated glycoprotein E (gE) negative BoHV-1 vaccine was assessed in goats with the aim to protect against CpHV-1 infection. Vaccine safety was evaluated by intranasal inoculation of two groups of goats with either a gE-negative BoHV-1 vaccine or a virulent BoHV-1. The length of viral excretion and the peak viral titre were reduced with the gE-negative vaccine. To assess the efficacy, two goats were inoculated intranasally twice 2 weeks apart with a gE-negative BoHV-1 vaccine. Four weeks later, immunised and control goats were challenged with CpHV-1. A 2 log(10) reduction in the peak viral titre was observed and the challenge virus excretion lasted 2 days more in immunised than in control goats. These data indicate the safety and the partial efficacy of a live attenuated gE-negative BoHV-1 vaccine intranasally administrated in goats.

The process development challenge for a new vaccine

The challenges of vaccine development are not limited to identification of suitable antigens, adjuvants and delivery methods, but include regulatory, technical and manufacturing hurdles in translating a vaccine candidate to the clinic. Process development is the technological foundation that underlies the manufacture of new vaccines and is central to successful commercialization.

Efficacy of a live equine herpesvirus-1 (EHV-1) strain C147 vaccine in foals with maternally-derived antibody: protection against EHV-1 infection

REASONS FOR PERFORMING STUDY

Currently, there is no recommended immunoprophylaxis against febrile respiratory diseases due to equine herpesvirus-1 (EHV-1) and -4 (EHV-4) in horses below age 5-6 months. This is because of interference by maternally-derived antibody (MDA) of vaccines.

OBJECTIVE

Unweaned equine foals are an important reservoir of EHV-1 transmission; therefore, we experimentally assessed the efficacy of a live EHV-1 vaccine in foals age 1.4-3.5 months with MDA.

METHODS

Following vaccination and challenge, parameters assessed were virus shedding in nasal mucus, leucocyte-associated viraemia, circulating virus neutralising antibody activity and clinical reactions.

RESULTS

Controlled challenge showed that a single intranasal dose of the vaccine afforded partial but significant protection against febrile respiratory disease, virus shedding and viraemia due to EHV-1 infection, despite virus-neutralising MDA.

CONCLUSIONS AND POTENTIAL RELEVANCE

The prospective vaccine would be a significant step forward in reducing the incidence of the disease caused by EHV-1 infection.

New options in herpes management

Herpesviruses in the alpha group--HSV-1, HSV-2, and VZV (i.e., HSV-3)--are ubiquitous in American society. HSV-1 is associated primarily with herpes labialis, while HSV-2 is involved in about 70% of cases of genital herpes. Varicellazoster virus causes chickenpox in unvaccinated children and others, and latent virus produces shingles later in life. Since many patients with HSV-1 and HSV-2 infections are asymptomatic, testing is important in determining presence of the viruses. Several antiviral agents effective against HSV have been marketed. While the infection cannot be cured, the available medications are effective for reducing the duration of outbreaks, recurrences, and possibly viral transmission.

Vaccination prevents latent HSV1 infection of mouse brain

Herpes simplex encephalitis (HSE) is a rare but very serious disorder caused by herpes simplex type 1 virus (HSV-1). Treatment with acyclovir decreases mortality but many patients still suffer cognitive impairment subsequently. A vaccine against HSV1 would therefore be of great value. HSV-1 has been implicated also in Alzheimer's disease (AD): we established that HSV1 resides in the brain of about two thirds of AD patients and aged normal people, and that in carriers of the type 4 allele of the apolipoprotein E gene, it is a strong risk factor for AD. Thus a vaccine against HSV-1 might prevent development of AD in some cases. To find whether a vaccine of mixed HSV-1 glycoproteins (ISCOMs), which protects mice from latent HSV-1 infection of sensory ganglia, prevents HSV1 latency in the CNS, ISCOM-vaccinated or unvaccinated animals were infected with HSV-1. Using polymerase chain reaction (PCR) we detected HSV-1 in brain from 16 of 39 unvaccinated mice (41%), but only 3 of 41 vaccinated mice (7%) (P < 0.001). Thus, ISCOMs protect the CNS also, suggesting their possible future usage in humans.

Detection of bovine herpesvirus-1 in peripheral blood mononuclear cells eight months postinfection

Peripheral blood mononuclear cells (PBMCs) from 5 calves (3 controls and 2 vaccinates) used in a bovine herpesvirus 1 (BHV-1) vaccine study with a BHV-1 Cooper strain challenge were collected 6 months after challenge. The PBMCs from the control animals were positive by immunofluorescence for the BHV-1 glycoprotein D (gD) while the vaccinates were negative. The PBMC samples from 4 of the 5 animals were examined for BHV-1 DNA by polymerase chain reaction (PCR) and for gD immunofluorescence at 8 months after challenge. The BHV-1 DNA and viral antigen were detected in PBMC samples at 8 months postinfection, but no virus was isolated.

Potential for immunotherapy in the treatment of herpesvirus infections

The concept of using immunotherapy to treat recurrent herpesvirus infections dates back to the 1930s, although many of the initial studies were seriously flawed. Since the late-1980s, however, the use of the guinea pig model of genital herpes has allowed investigators to evaluate carefully several vaccine and immunomodulatory strategies for the control of recurrent herpesvirus infections. These investigations have clearly shown that both approaches can significantly decrease recurrence rates of genital herpes, and the most effective routes, adjuvants and treatment regimens have been identified. Similar strategies have also been shown to decrease herpes simplex virus (HSV)-1 recurrences in animal models of ocular infection. To date, only moderate success has been reported for human trials, although the optimum strategies that were identified in the animal models have not yet been evaluated.

Therapeutic periocular vaccination with a subunit vaccine induces higher levels of herpes simplex virus-specific tear secretory immunoglobulin A than systemic vaccination and provides protection against recurrent spontaneous ocular shedding of virus in latently infected rabbits

Rabbits latently infected with herpes simplex virus type 1 (HSV-1) were vaccinated either periocularly or systemically with a subunit vaccine (gB2 + gD2) plus adjuvant or adjuvant alone. Tear films were collected daily to measure recurrent infectious HSV-1 shedding. After systemic vaccination, the latently infected rabbits were not protected against recurrent ocular viral shedding (HSV-1-positive tear film cultures/total cultures) compared with either the systemic or periocular adjuvant controls (systemic vaccination = 49 of 972, 5.0%; systemic control = 46 of 972, 4.7%; periocular control = 43 of 930, 4.6%; P > 0.8). In contrast, latently infected rabbits vaccinated periocularly with the same vaccine had significantly reduced recurrent shedding (20 of 1026, 2.0%) compared with controls (P < 0.001) or systemic vaccination (P = 0.0002). Thus, recurrent HSV-1 shedding was significantly reduced by therapeutic local periocular subunit vaccination but not by therapeutic systemic subunit vaccination. Neutralizing antibody titers in the serum of systemically and ocularly vaccinated rabbits was similar. In contrast, HSV-specific tear secretory immunoglobulin A was significantly higher in the ocularly vaccinated group (P < 0.01). These results strongly suggest that in the rabbit, and presumably in humans, the local ocular (mucosal) immune response is much more important than the systemic immune response for therapeutic protection against recurrent ocular HSV-1. Thus development of a therapeutic vaccine against recurrent ocular HSV-1 should be directed at enhancing the local ocular (mucosal) immune response.

Effect of IL-4 and IL-12 liposomal formulations on the induction of immune response to bovine herpesvirus type-1 glycoprotein D

Activation of different T-helper (Th) responses following immunisation has profound and specific influences on the development of the immune response and on the ability of a vaccine to confer protection. Since cytokines are capable of influencing the stimulation of distinct T-cell responses, their encapsulation in vaccines should modulate antigen-specific immune responses. Unfortunately, the use of cytokines in vivo is hampered by their rapid clearance and inactivation. One possible solution to this problem is the use of liposomes to entrap both cytokines and antigen. This approach will not only protect the cytokine but will also deliver the two components simultaneously to the same site. The authors examined, therefore, the immune responses elicited by systemic immunisation of mice with liposome formulations containing a truncated form of bovine herpesvirus type-1 glycoprotein D (tgD) together with IL-4 or IL-12. Subcutaneous immunisation with liposomes containing tgD and IL-12 significantly enhanced the induction of antigen-specific cellular and humoral immune responses. These responses were characterised by an increase in IFN-gamma secreting cells and the induction of tgD-specific IgG2a antibodies. In contrast, encapsulation of IL-4 into tgD-liposomes did not enhance the humoral immune response to gD but significantly influenced the development of antigen-specific IL-4 secreting cells. Our results indicated that encapsulation of IL-12 into the liposomes was necessary for the systemic adjuvant effect and demonstrated the feasibility of using liposome technology and cytokines to manipulate the development of different antigen-specific Th subsets in vivo.

Effect of microencapsulation on immunogenicity of a bovine herpes virus glycoprotein and inactivated influenza virus in mice

We previously found that aqueous-based spermine-alginate or spermine-chondroitin sulfate microcapsules enhanced rotavirus-specific humoral immune responses after intramuscular inoculation of mice. To extend our observations with whole, infectious rotavirus to vaccine strategies which include inactivated virus and purified proteins, we determined the capacity of aqueous-based microcapsules to enhance virus-specific immune responses to bovine herpes virus type 1 glycoprotein D (BHV-1-gD) or ether-treated influenza virus. We found that spermine-alginate microcapsules decreased the quantity of BHV-1-gD necessary to induce protein-specific antibodies about 5000-fold. However, spermine-alginate microcapsules did not enhance influenza virus-specific antibody responses. Microcapsules composed of spermine-chondroitin sulfate did not enhance either BHV-1-gD or influenza virus-specific immune responses. Possible mechanisms of enhancement of virus-specific antibody responses by microencapsulation are discussed.

Efficacy of a recombinant glycoprotein D subunit vaccine on the development of primary and recurrent ocular infection with herpes simplex virus type 1 in mice

The protective efficacy of a glycoprotein D subunit vaccine (gD2 SB AS4) was evaluated in a mouse model of human recurrent herpetic stromal keratitis (HSK). When administered before primary infection, gD2 SB AS4 protected mice against corneal pathology, mortality, and latency resulting from ocular viral challenge with herpes simplex virus type 1 (HSV-1) McKrae strain. In addition, gD2 SB AS4 significantly decreased postreactivation corneal disease. A control vaccine, gD2 alum, protected against acute ocular infection only. When administered after primary infection, gD2 SB AS4 vaccination decreased postreactivation ocular shedding but had no other significant effects. Vaccination with gD2 SB AS4 was associated with high anti-gD antibody responses and low delayed-type hypersensitivity responses. These results have identified a prophylactic vaccine, gD2 SB AS4, with activity against acute and recurrent HSK in mice and emphasize the need for vaccine evaluation in both primary and recurrent ocular herpetic disease models.

Defective transport of herpes simplex virus glycoprotein in interferon-treated cells: role of intracellular pH

We have investigated the mechanism(s) of interferon (IFN)-induced inhibition of assembly steps of herpes simplex virus (HSV-1) in mouse LB cells. Data showed that physiological doses of mouse IFN-beta (10-100 IU/ml) significantly inhibited the infectivity (5- to 100-fold) of HSV-1; however, viral protein synthesis was marginally inhibited (2- to 5-fold). Immunofluorescence studies showed that most of the HSV-1gD glycoprotein accumulated intracellularly in IFN-treated LB and LMtk- cells transfected with gD cDNA, as compared to untreated controls, where most of the gD was localized on the plasma membrane. Double-immunofluorescence studies demonstrated that rhodamine-labeled wheat germ agglutinin (WGA) was co-localized with gD protein, suggesting the block was in the transport from the trans-Golgi to the plasma membrane. IFN treatment of LB and LMtk- cells raised the intracellular pH as measured by DAMP distribution and SNARF-1 using laser spectroscopy; this could play an important role in the inhibition of transport of HSV-1gD.

[T-cell-induced prevention of HSV-1 keratitis by immunization with the synthetic peptide of glycoprotein D]

C.AL-20 mice susceptible to herpes simplex virus (HSV) were protected against HSV keratitis (HSK) and encephalitis by subcutaneous immunization with synthetic peptide corresponding to the N-terminal amino acid residues 5-23 of HSV glycoprotein D, which is a dominant immunogen of HSV-1. Protection against HSV was related to a potent humoral anti-HSV response. FACScan analysis revealed that CD4+V beta 8(1.2)+ cells in the spleen were markedly decreased 2 days after HSV challenge, and CD8+ cells were increased. Numerous CD4+ and V beta 8(1.2)+ cells were found in the corneal tissue from HSV-infected sham-immunized mice; no such cells were seen in gD(5-23) immunized mice. No cytotoxic cells were detected in the corneas or spleens of gD(5-23) immunized mice, and these mice had decreased DTH responses. Protection against HSV through immunization with gD(5-23) involves humoral and cellular immune mechanisms. CD4+V beta 8(1.2)+ maybe critical in mediating the pathology of HSK. CD8+ cells may be protective by non-cytotoxic mechanisms. Our results suggest that gD peptides may be potent as vaccines against HSV.

Comparison of the effects of adjuvants and adjuvant doses on the quantitative and qualitative antibody response to selected antigens in New World squirrel monkeys Saimiri sciureus

The effect of several adjuvants and of adjuvant doses on the quantitative and qualitative antibody response to tetanus toxoid (TT) and a recombinant herpes simplex virus peptide (HSVgD) was evaluated in the New World monkey Saimiri sciureus. All adjuvant formulations were effective in inducing a strong antibody response to these antigens. The qualitative antibody response, as defined by monoclonal antibodies 3A2/G6 and 4G3/B5, was determined. Only 3A2/G6+ antibodies were induced after immunization with HSVgD irrespective of the adjuvant used and after immunization with TT alone. However, both types of antibodies were induced against TT in the presence of the adjuvants tested. These data suggest that both adjuvant and antigens can intervene in driving the quality of the antibody response induced after immunization. Strong antibody response to TT was induced at any adjuvant dose tested, suggesting that lower doses are as effective as higher doses. These findings can have implications on the design of future trials of vaccine candidate constructs in monkeys and eventually in human beings.

Effects of in vivo depletion of immunocyte populations on herpes simplex virus glycoprotein D vaccine-induced resistance to HSV2 challenge

BALB/c mice, preimmunized with a protective dose of native herpes simplex virus type 1 glycoprotein D (ngD1) vaccine, were depleted of selected immunocyte populations in vivo using monoclonal antibodies directed at Thy1+, L3T4+, or Lyt2+ cells. Following immunization and depletion, animals were inoculated with varied challenge levels of herpes simplex virus type 2 (HSV2) in the footpad and were monitored for disease. Both depleted undepleted gD-immunized mice were significantly protected when compared with placebo controls. T-cell-independent protection in Thy1 and L3T4-depleted ngD1-immunized animals was effective at low and moderate levels of HSV2 challenge levels, high levels of HSV2 giving high symptom scores in immunized and depleted mice. Depletion of Lyt2+ cells had no significant effect on the outcome of HSV2 infection. Depleted and nondepleted animals also were assessed in parallel for cellular and humoral responsiveness to ngD1 and to HSV antigens in vitro. Lymphoproliferative responses were abrogated in gD-immunized mice treated with anti-Thy1 or anti-L3T4, anti-Lyt2 treatment having little effect. Postimmunization T-cell depletion did not undermine ELISA or neutralizing antibody responses. These findings suggest that at low to moderate levels of virus challenge vaccine-elicited antibody plays a primary role in limiting the severity of infection, T-cell-mediated protective responses being of enhanced significance only at high levels of virus challenge.

Immune responses to herpes simplex virus in guinea pigs (footpad model) and mice immunized with vaccinia virus recombinants containing herpes simplex virus glycoprotein D

Vaccinia virus recombinants containing the herpes simplex virus (HSV) gene for glycoprotein D type 1 (gD-1) under control of an early (VP176) or late (VP254) vaccinia virus promoter or for HSV glycoprotein type 2 (gD-2) under control of the early promoter (VP221) were studied for their ability to induce protective immunity to HSV-2 in the guinea pig model of cutaneous recurrent disease and the mouse model of fatal disease. Titers of HSV-specific neutralizing antibody were similar in the two groups of immunized animals, but HSV-specific T cell responses were significantly higher in VP176-immunized than in VP254-immunized animals, as determined by lymphoproliferation (P less than .005) and delayed-type hypersensitivity (P less than .01) responses. The reduced responses correlated with poor expression of the gD protein and its impaired processing in infected antigen-presenting cells (splenic adherent and epidermal cells). VP176 immunization protected against primary (P much less than .001) and recurrent (P much less than .001) cutaneous HSV-2 lesions and ganglionic latency (62% protection) in the guinea pig and against zosteriform skin lesions and fatal disease in the mouse. Immunization with VP254 was not protective. In guinea pigs VP221 did not protect against primary HSV-2 cutaneous disease but did reduce the proportion of animals with recurrent disease (P less than .05). This partial protection appears to be associated with the role of type-specific antigenic determinants in gD-2 immunoregulation.

Native herpes simplex virus glycoprotein D vaccine: immunogenicity and protection in animal models

Mice, guinea pigs, and rhesus monkeys were immunized with immunoaffinity-purified native glycoprotein D (gD) derived from herpes simplex virus type 1 (HSV1). The native glycoprotein has evoked significant in vivo responses even at low doses. Thus, mice immunized with doses as low as 1 microgram were significantly protected from the morbidity and mortality of lethal HSV2 challenge and from establishment of latent HSV2 infection. Protection was dose-related and correlated with prechallenge serum neutralizing antibody titres to HSV. Similarly, immunized guinea-pigs demonstrated significant reductions in the frequency, severity and duration of genital lesions induced by HSV2 vaginal challenge. In long term immunogenicity studies, immunized rhesus monkeys exhibited significant serum neutralizing antibody responses to both HSV1 and HSV2. In vitro stimulation of monkey peripheral blood leucocytes with purified gD resulted in a significant cellular proliferative response. The results obtained in these animal models with a gD subunit vaccine provide an appropriate foundation for the initiation of human studies.

Immunoselection of recombinant baculoviruses expressing high levels of biologically active herpes simplex virus type 1 glycoprotein D

The DNA sequence encoding the complete herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) was inserted into a baculovirus transfer vector under control of the polyhedrin gene promoter of the baculovirus Autographa california nuclear polyhedrosis virus (AcNPV). After co-transfection of Spodoptera frugiperda (Sf9) insect cells with wild-type AcNPV DNA and the recombinant transfer vector DNA, polyhedrin-negative recombinants that expressed high levels of HSV-1 gD were isolated using immunoaffinity selection with antibody coated magnetic particles followed by plaque purification. These recombinant baculoviruses expressed a protein that was slightly smaller than virion HSV-1 gD made in Vero cells. This recombinant protein was expressed at high levels. The expressed protein was glycosylated, was found on the membrane of Sf9 cells, and reacted with gD specific antibodies. Antibodies raised in mice to the recombinant gD neutralized HSV-1 as measured by plaque reduction assays. Mice inoculated with the recombinant baculovirus were completely protected from lethal challenge with HSV-1.

Native HSV glycoprotein D subunit vaccine: analysis of in vitro T-cell activation and antigen presentation

Native herpes simplex virus (HSV) glycoprotein D (ngD1) subunit vaccine, a potential human vaccine candidate, was examined to determine responsive murine lymphocyte populations in vitro. This vaccine preparation has been shown to protect against HSV challenge in mice and guinea pigs and to elicit humoral and cellular responses in rodents and primates. Immunized BALB/c mice were used in splenocyte lymphoproliferative studies to analyze the cellular response. After in vivo sensitization, the in vitro proliferative response observed appears to be resultant of Class II-restricted T-cell division in response to gD presented in the context of macrophage-expressed Ia.