Progressive vaccinia

A Prolonged Case of Severe Mpox as an Opportunistic Infection in Advanced AIDS

The case report discusses a 29-year-old male with advanced HIV who experienced one of the longest, confirmed cases of monkeypox (mpox) infection. Despite treatment with antivirals and supportive care, including intravenous tecovirimat and vaccinia immune globulin, the patient's condition worsened over a six-and-a-half-month period. He suffered from widespread ulcerative, necrotic lesions and multiple complications, including acute kidney injury, multi-drug resistant bacterial infections, and respiratory failure. Despite repeated treatments, including brincidofovir, the patient remained PCR-positive for monkeypox virus (MPXV) with low cycle threshold (Ct) values, indicating active infection. The case underscores the severity of mpox in immunocompromised individuals, particularly those with advanced HIV, and highlights the challenges in managing such cases. The patient's persistently low CD4 count and unsuppressed HIV viral load likely contributed to the inability to clear the virus. The report emphasizes the need for further research to optimize treatment strategies for MPXV infection, especially in people living with HIV.

Pockenvirusinfektionen in der Dermatologie: Poxvirus infections in dermatology - the neglected, the notable, and the notorious

Die Familie Poxviridae umfasst derzeit 22 Gattungen, die Wirbeltiere infizieren können. Humanpathogene Pockenviren gehören den Gattungen Ortho‐, Para‐, Mollusci‐ und Yatapoxvirus an. Bis zur Eradikation der Variola vera im Jahr 1979 waren die Pocken, im Volksmund auch Blattern genannt, eine schwerwiegende Gesundheitsbedrohung für die Bevölkerung. Noch heute sind Dermatologen mit zahlreichen Pockenvirusinfektionen konfrontiert, wie den Bauernhofpocken, die als Zoonosen nach Tierkontakten in ländlichen Gebieten oder nach Massenversammlungen auftreten können. In den Tropen können Erkrankungen durch Tanapox‐ oder Vaccinia‐Viren zu den Differenzialdiagnosen gehören. Dellwarzen sind weltweit verbreitet und werden in bestimmten Fällen als sexuell übertragbare Pockenvirusinfektion angesehen. In jüngster Zeit hatten sich Mpox (Affenpocken) zu einer gesundheitlichen Notlage von internationaler Tragweite entwickelt, die eine rasche Identifizierung und angemessene Behandlung durch Dermatologen und Infektiologen erfordert. Fortschritte und neue Erkenntnisse über Epidemiologie, Diagnose, klinische Manifestationen und Komplikationen sowie Behandlung und Prävention von Pockenvirusinfektionen erfordern ein hohes Maß an Fachwissen und interdisziplinärer Zusammenarbeit in den Bereichen Virologie, Infektiologie und Dermatologie. Dieser CME‐Artikel bietet einen aktualisierten systematischen Überblick, um praktizierende Dermatologen bei der Identifizierung, Differenzialdiagnose und Behandlung klinisch relevanter Pockenvirusinfektionen zu unterstützen.

Poxvirus infections in dermatology - the neglected, the notable, and the notorious

The family Poxviridae currently comprises 22 genera that infect vertebrates. Of these, members of the Ortho-, Para-, Mollusci- and Yatapoxvirus genera have been associated with human diseases of high clinical relevance in dermatology. Historically, smallpox had been a notorious health threat until it was declared eradicated by the World Health Organization in 1979. Today, dermatologists are confronted with a variety of poxviral infections, such as farmyard pox, which occurs as a zoonotic infection after contact with animals. In the tropics, tanapox or vaccinia may be in the differential diagnosis as neglected tropical dermatoses. Molluscum contagiosum virus infection accounts for significant disease burden worldwide and is classified as a sexually transmitted infection in certain scenarios. Recently, mpox (monkeypox) has emerged as a public health emergency of international concern, requiring rapid recognition and appropriate management by dermatologists and infectious disease specialists. Advances and new insights into the epidemiology, diagnosis, clinical manifestations and complications, treatment, and prevention of poxviral infections require a high level of expertise and interdisciplinary skills from healthcare professionals linking virology, infectious diseases, and dermatology. This CME article provides a systematic overview and update to assist the practicing dermatologist in the identification, differential diagnosis, and management of poxviral infections.

Unraveling Monkeypox: An Emerging Threat in Global Health

Monkeypox, a viral zoonotic ailment originating in the Central and West African regions, has escalated into a global health issue of growing concern. The current analysis offers an exhaustive examination of monkeypox, emphasizing its historical progression, etiology, epidemiological patterns, pathophysiological mechanisms, clinical manifestations, diagnostic methodologies, treatment modalities, and preventive strategies. The worldwide discontinuation of smallpox vaccination has contributed to an increased incidence of monkeypox, driven by the expansion of vulnerable host populations. Significant strides in diagnostic procedures, prospective antiviral treatments, and vaccine development exhibit potential in managing this affliction, yet obstacles remain in terms of disease control, prevention, and treatment. Additionally, the international propagation of monkeypox underscores the need for robust public health initiatives and the significant role played by global health institutions in disease containment. Prospective research endeavors should strive to enhance our comprehension of the natural reservoirs of monkeypox and its transmission dynamics, evaluate sustained immune responses to novel vaccines, and investigate the potential impact of One Health strategies. This analysis underscores the pressing necessity for increased research and synchronized global efforts to tackle this emergent infectious malady.

Uses and Challenges of Antiviral Polyclonal and Monoclonal Antibody Therapies

Viral diseases represent a major public health concerns and ever-present risks for developing into future pandemics. Antiviral antibody therapeutics, either alone or in combination with other therapies, emerged as valuable preventative and treatment options, including during global emergencies. Here we will discuss polyclonal and monoclonal antiviral antibody therapies, focusing on the unique biochemical and physiological properties that make them well-suited as therapeutic agents. We will describe the methods of antibody characterization and potency assessment throughout development, highlighting similarities and differences between polyclonal and monoclonal products as appropriate. In addition, we will consider the benefits and challenges of antiviral antibodies when used in combination with other antibodies or other types of antiviral therapeutics. Lastly, we will discuss novel approaches to the characterization and development of antiviral antibodies and identify areas that would benefit from additional research.

Recent Advances in Research and Management of Human Monkeypox Virus: An Emerging Global Health Threat

In 2003, the United States saw an epidemic of monkeypox that was later traced back to rodents of West Africa infected with the monkeypox virus (MPXV). Disease in the United States seemed less severe than the smallpox-like disease in the Democratic Republic of the Congo (DRC). In this study, researchers analyzed data from Central Africa: two distinct MPXV clades were confirmed by sequencing the genomes of MPXV isolates from Western Africa, the United States, and Central Africa. By comparing open reading frames across MPXV clades, scientists can infer which virus proteins might account for the observed variation in pathogenicity in humans. Monkeypox can be prevented and controlled with a better understanding of MPXV's molecular etiology and epidemiological and clinical features. In light of the current outbreaks worldwide, we provide updated information on monkeypox for medical professionals in this review.

Novel severe oculocutaneous manifestations of human monkeypox virus infection and their historical analogues

WHO has declared human mpox (formerly known as monkeypox) a global public health emergency since July, 2022. When case numbers were increasing, so did clinicians' exposures to new elements of the disease. Additionally, the burden of mpox is particularly apparent in immunocompromised patients, who can have more variable and severe manifestations of disease across organ systems. In this Grand Round, we report novel and severe oculocutaneous manifestations of mpox in this population, which are both sight and life threatening. Specifically, we highlight two patients with mpox and AIDS who had refractory skin necrosis that progressed to either ocular compromise or panfacial gangrene, or both. Both patients ultimately died due to systemic complications of their infections. Through clinical analogies, we show how past experiences with related orthopoxviruses, such as variola virus (smallpox) and vaccinia virus, can add useful context for understanding and treating these new disease states. We suspect that in patients who are immunocompromised, monkeypox virus can clinically evolve not only via viraemia but also through direct intradermal spread. We propose that intradermal spread occurs by a process clinically and immunologically analogous to progressive vaccinia, a complication previously seen after conventional smallpox vaccination. We share evidence in support of this theory and implications regarding early management and post-exposure prophylaxis for at-risk populations. Content note: this Grand Round contains graphic images of mpox lesions of the eyes and face.

EPIPOX: A Resource Facilitating Epitope-Vaccine Design Against Human Pathogenic Orthopoxviruses

EPIPOX is a specialized online resource intended to facilitate the design of epitope-based vaccines against orthopoxviruses. EPIPOX is built upon a collection of T cell epitopes that are shared by eight pathogenic orthopoxviruses, including variola minor and major strains, monkeypox, cowpox, and vaccinia viruses. In EPIPOX, users can select T cell epitopes attending to the predicted binding to distinct major histocompatibility molecules (MHC) and according to various features that may have an impact on epitope immunogenicity. Among others, EPIPOX allows to discern epitopes by their structural location in the virion and the temporal expression of the counterpart antigens. Overall, the annotations in EPIPOX are optimized to facilitate the rational design of T cell epitope-based vaccines. In this chapter, we describe the main features of EPIPOX and exemplify its use, retrieving orthopoxvirus-specific T cell epitopes with features set to enhance their immunogenicity. EPIPOX is available for free public use at http://bio.med.ucm.es/epipox/ .

The Potential Role of Passive Antibody-Based Therapies as Treatments for Monkeypox

Monkeypox, a zoonosis caused by the orthopox monkeypox virus (MPXV) that is endemic to Central and West Africa, was previously linked to sporadic outbreaks and rare, travel-associated cases. An outbreak of monkeypox in 2022 has spurred a public health emergency of international concern, and this outbreak is unprecedented in terms of its scale and epidemiology. The outbreak has been focused overwhelmingly in men who have sex with men; however, the trajectory of the outbreak remains uncertain, with spread now being reported in women and children. The mortality has been low (<1%), yet the morbidity is high. Vaccines and oral antiviral agents that have been developed to protect against smallpox are available for use against monkeypox. However, the supply has been unable to match the demand during the outbreak. Passive antibody-based therapies, such as hyperimmune globulin (HIG), monoclonal antibodies, and convalescent plasma (CP), have been used against a diverse array of infectious diseases, culminating in their extensive use during the COVID-19 pandemic. Passive antibody-based therapies could play a role in the treatment of monkeypox, either as a temporizing role amid a shortfall in vaccines and antivirals or a complementary role to direct-acting antivirals. Drawing on the collective experience to date, there are regulatory, administrative, and logistical challenges to the implementation of antibody-based therapies. Their efficacy is contingent upon early administration and the presence of high-titer antibodies against the targeted pathogen. Research is needed to address questions pertaining to how to qualify HIG and CP and to determine their relative efficacy against MPXV, compared to antecedent therapies and preventative strategies. IMPORTANCE Monkeypox is an infection caused by the monkeypox virus (MPXV). The clinical findings in monkeypox include fever and rash. Historically, most cases of human monkeypox were reported in Africa. This changed in 2022, with a massive escalation in the number of cases across multiple countries, mainly affecting men who have sex with men. Although vaccines and oral antiviral medications are available for the treatment of monkeypox, their supply has been overwhelmed by the unprecedented number of cases. Antibody-based therapies (ABTs) have long been used to treat infectious diseases. They are produced in a laboratory or from plasma that has been collected from individuals who have recovered from an infection or have been vaccinated against that infection (in this case, monkeypox). ABTs could play a role in the treatment of monkeypox, either while awaiting oral medications or as a complementary treatment for patients that are at risk of severe disease.

Prevention and Treatment of Monkeypox: A Systematic Review of Preclinical Studies

The outbreak of monkeypox, coupled with the onslaught of the COVID-19 pandemic is a critical communicable disease. This study aimed to systematically identify and review research done on preclinical studies focusing on the potential monkeypox treatment and immunization. The presented juxtaposition of efficacy of potential treatments and vaccination that had been tested in preclinical trials could serve as a useful primer of monkeypox virus. The literature identified using key terms such as monkeypox virus or management or vaccine stringed using Boolean operators was systematically reviewed. Pubmed, SCOPUS, Cochrane, and preprint databases were used, and screening was performed in accordance with PRISMA guidelines. A total of 467 results from registered databases and 116 from grey literature databases were screened. Of these results, 72 studies from registered databases and three grey literature studies underwent full-text screening for eligibility. In this systematic review, a total of 27 articles were eligible according to the inclusion criteria and were used. Tecovirimat, known as TPOXX or ST-246, is an antiviral drug indicated for smallpox infection whereas brincidofovir inhibits the viral DNA polymerase after incorporation into viral DNA. The ability of tecovirimat in providing protection to poxvirus-challenged animals from death had been demonstrated in a number of animal studies. Non-inferior with regard to immunogenicity was reported for the live smallpox/monkeypox vaccine compared with a single dose of a licensed live smallpox vaccine. The trial involving the live vaccine showed a geometric mean titre of vaccinia-neutralizing antibodies post two weeks of the second dose of the live smallpox/monkeypox vaccine. Of note, up to the third generation of smallpox vaccines-particularly JYNNEOS and Lc16m8-have been developed as preventive measures for MPXV infection and these vaccines had been demonstrated to have improved safety compared to the earlier generations.

Monkeypox: epidemiology, pathogenesis, treatment and prevention

Monkeypox is a zoonotic disease that was once endemic in west and central Africa caused by monkeypox virus. However, cases recently have been confirmed in many nonendemic countries outside of Africa. WHO declared the ongoing monkeypox outbreak to be a public health emergency of international concern on July 23, 2022, in the context of the COVID-19 pandemic. The rapidly increasing number of confirmed cases could pose a threat to the international community. Here, we review the epidemiology of monkeypox, monkeypox virus reservoirs, novel transmission patterns, mutations and mechanisms of viral infection, clinical characteristics, laboratory diagnosis and treatment measures. In addition, strategies for the prevention, such as vaccination of smallpox vaccine, is also included. Current epidemiological data indicate that high frequency of human-to-human transmission could lead to further outbreaks, especially among men who have sex with men. The development of antiviral drugs and vaccines against monkeypox virus is urgently needed, despite some therapeutic effects of currently used drugs in the clinic. We provide useful information to improve the understanding of monkeypox virus and give guidance for the government and relative agency to prevent and control the further spread of monkeypox virus.

Repositioning potentials of smallpox vaccines and antiviral agents in monkeypox outbreak: A rapid review on comparative benefits and risks

Background and aims

There is a sought for vaccines and antiviral agents as countermeasures for the recent monkeypox outbreak. Here, we aimed to review and discuss the repurposing potentials of smallpox vaccines and drugs in monkeypox outbreaks based on their comparative benefits and risks. Therefore, we conducted this rapid review and discussed the repurposing potentials of smallpox vaccines and drugs in monkeypox infection.

Methods

Here, we searched Google Scholar and PubMed for relevant information and data. We found many articles that have suggested the use of smallpox vaccines and antiviral drugs in monkeypox outbreaks according to the study findings. We read the relevant articles to extract information.

Results

According to the available documents, we found two replication-competent and one replication-deficient vaccinia vaccines were effective against Orthopoxvirus. However, the healthcare authorities have authorized second-generation live vaccina virus vaccines against Orthopoxvirus in many countries. Smallpox vaccine is almost 85% effective in preventing monkeypox infection as monkeypox virus, variola virus, and vaccinia virus are similar. The United States and Canada have approved a replication-deficient third-generation smallpox vaccine for the prevention of monkeypox infection. However, the widely used second-generation smallpox vaccines contain a live virus and replicate it into the human cell. Therefore, there is a chance to cause virus-induced complications among the vaccinated subjects. In those circumstances, the available Orthopoxvirus inhibitors might be a good choice for treating monkeypox infections as they showed similar efficacy in monkeypox infection in different animal model clinical trials. Also, the combined use of antiviral drugs and vaccinia immune globulin can enhance significant effectiveness in immunocompromised subjects.

Conclusion

Repurposing of these smallpox vaccines and antiviral agents might be weapons to fight monkeypox infection. Also, we recommend further investigations of smallpox vaccines and Orthopoxvirus inhibitors in a human model study to explore their exact role in human monkeypox infections.

Monkeypox: A Contemporary Review for Healthcare Professionals

The ongoing 2022 multicountry outbreak of monkeypox is the largest in history to occur outside of Africa. Monkeypox is an emerging zoonotic disease that for decades has been viewed as an infectious disease with significant epidemic potential because of the increasing occurrence of human outbreaks in recent years. As public health entities work to contain the current outbreak, healthcare professionals globally are aiming to become familiar with the various clinical presentations and management of this infection. We present in this review an updated overview of monkeypox for healthcare professionals in the context of the ongoing outbreaks around the world.

Capripoxvirus Infections in Ruminants: A Review

Lumpy skin disease, sheeppox, and goatpox are notifiable diseases of cattle, sheep, and goats, respectively, caused by viruses of the Capripoxvirus genus. They are responsible for both direct and indirect financial losses. These losses arise through animal mortality, morbidity cost of vaccinations, and constraints to animals and animal products' trade. Control and eradication of capripoxviruses depend on early detection of outbreaks, vector control, strict animal movement, and vaccination which remains the most effective means of control. To date, live attenuated vaccines are widely used; however, conferred protection remains controversial. Many vaccines have been associated with adverse reactions and incomplete protection in sheep, goats, and cattle. Many combination- and recombinant-based vaccines have also been developed. Here, we review capripoxvirus infections and the immunity conferred against capripoxviruses by their respective vaccines for each ruminant species. We also review their related cross protection to heterologous infections.

Progressive Vaccinia Acquired through Zoonotic Transmission in a Patient with HIV/AIDS, Colombia

In March 2015, a patient in Colombia with HIV/AIDS was hospitalized for disseminated ulcers after milking cows that had vesicular lesions on their udders. Vaccinia virus was detected, and the case met criteria for progressive vaccinia acquired by zoonotic transmission. Adherence to an optimized antiretroviral regimen resulted in recovery.

[Zoonotic vaccinia in Colombia: Cumulative evidence of the emergence of poxviruses in the world]

The recent occurrence of vaccinia virus infections in humans and animals in Colombia, together with that reported for this and other species of the genus Orthopoxvirus in some South American, African, Asian and European countries, is supporting evidence of the emergence and re-emergence of the genus. This fact has become of great interest for public health around the world due to its biological and an epidemiological features, as was in the past the variola virus, one of its representatives. The emergence and re-emergence of the genus Orthopoxvirus may be a consequence of stopping vaccination against the variola virus in the 1970s and 1980s. This vaccination unsuspectedly induced cross-protective immunity to other species of that genus. This is a review of the history, biology and epidemiology of the main species of the genus Orthopoxvirus, together with its clinical presentation, social context and public health impact in the past, present and future.

Preemptive Tecovirimat Use in an Active Duty Service Member Who Presented With Acute Myeloid Leukemia After Smallpox Vaccination

Smallpox vaccine is contraindicated in immunosuppression due to increased risk for adverse reactions (eg, progressive vaccinia). We describe the first-ever use of tecovirimat as a preemptive vaccinia virus treatment strategy during induction chemotherapy in an active duty service member who presented with acute leukemia and inadvertent autoinoculation after smallpox vaccination.

Regulatory aspects of quality and safety for live recombinant viral vaccines against infectious diseases in Japan

Recombinant viral vaccines expressing antigens of pathogenic microbes (e.g., HIV, Ebola virus, and malaria) have been designed to overcome the insufficient immune responses induced by the conventional vaccines. Our knowledge of and clinical experience with the new recombinant viral vaccines are insufficient, and a clear regulatory pathway is needed for the further development and evaluation of recombinant viral vaccines. In 2018, the research group supported by the Ministry of Health, Labour and Welfare, Japan (MHLW) published a concept paper to address the development of recombinant viral vaccines against infectious diseases. Herein we summarize the concept paper-which explains the Japanese regulatory concerns about recombinant viral vaccines-and provide a focus of discussion about the development of recombinant viral vaccines.

Vaccinating against monkeypox in the Democratic Republic of the Congo

Healthcare-associated transmission of monkeypox has been observed on multiple occasions in areas where the disease is endemic. Data collected by the US Centers for Disease Control and Prevention (CDC) from an ongoing CDC-supported program of enhanced surveillance in the Tshuapa Province of the Democratic Republic of the Congo, where the annual incidence of human monkeypox is estimated to be 3.5-5/10,000, suggests that there is approximately one healthcare worker infection for every 100 confirmed monkeypox cases. Herein, we describe a study that commenced in February 2017, the intent of which is to evaluate the effectiveness, immunogenicity, and safety of a third-generation smallpox vaccine, IMVAMUNE®, in healthcare personnel at risk of monkeypox virus (MPXV) infection. We describe procedures for documenting exposures to monkeypox virus infection in study participants, and outline lessons learned that may be of relevance for studies of other investigational medical countermeasures in hard to reach, under-resourced populations.

Construction of an attenuated Tian Tan vaccinia virus strain by deletion of TA35R and TJ2R genes

rVTT-TA35-TJ, an attenuated vaccinia virus Tian Tan strain (VTT), was constructed by knocking out two non-essential gene fragments (TA35R and TJ2R) related to virulence, immunomodulation, and host range; and by combining double marker screening with exogenous and endogenous selectable marker knock-out techniques. Here, the shuttle plasmids pSK-TA35 and pSK-TJ were constructed, containing two pairs of recombinant arms: early and late strong promoter pE/L and EGFP as an exogenous selectable marker. The recombinant vaccinia virus rVTT-TA35-TJ without exogenous selection markers was then obtained through homologous recombination technology and the Cre/loxP system. Knocking out the two gene fragments does not affect the replication ability of the virus and displays a good genetic stability. Furthermore, a series of in vivo and in vitro experiments demonstrate that although virulence of rVTT-TA35-TJ is attenuated significantly, high immunogenicity was maintained. These results support the potential development of rVTT-TA35-TJ as a safe viral vector or vaccine.

Inhibition of vaccinia virus replication by nitazoxanide

Nitazoxanide (NTZ) is an FDA-approved anti-protozoal drug that inhibits several bacteria and viruses as well. However, its effect on poxviruses is unknown. Therefore, we investigated the impact of NTZ on vaccinia virus (VACV). We found that NTZ inhibits VACV production with an EC₅₀ of ~2 μM, a potency comparable to that reported for several other viruses. The inhibitory block occurs early during the viral life cycle, prior to viral DNA replication. The mechanism of viral inhibition is likely not due to activation of intracellular innate immune pathways, such as protein kinase R (PKR) or interferon signaling, contrary to what has been suggested to mediate the effects of NTZ against some other viruses. Rather, our finding that addition of exogenous palmitate partially rescues VACV production from the inhibitory effect of NTZ suggests that NTZ impedes adaptations in cellular metabolism that are needed for efficient completion of the VACV replication cycle.

Isolation and identification of compounds from Kalanchoe pinnata having human alphaherpesvirus and vaccinia virus antiviral activity

CONTEXT

Kalanchoe pinnata (Lam.) Pers. (Crassulaceae) is a succulent plant that is known for its traditional antivirus and antibacterial usage.

OBJECTIVE

This work examines two compounds identified from the K. pinnata plant for their antivirus activity against human alphaherpesvirus (HHV) 1 and 2 and vaccinia virus (VACV).

MATERIALS AND METHODS

Compounds KPB-100 and KPB-200 were isolated using HPLC and were identified using NMR and MS. Both compounds were tested in plaque reduction assay of HHV-2 wild type (WT) and VACV. Both compounds were then tested in virus spread inhibition and virus yield reduction (VYR) assays of VACV. KPB-100 was further tested in viral cytopathic effect (CPE) inhibition assay of HHV-2 TK-mutant and VYR assay of HHV-1 WT.

RESULTS

KPB-100 and KPB-200 inhibited HHV-2 at IC₅₀ values of 2.5 and 2.9 μg/mL, respectively, and VACV at IC₅₀ values of 3.1 and 7.4 μg/mL, respectively, in plaque reduction assays. In virus spread inhibition assay of VACV KPB-100 and KPB-200 yielded IC₅₀ values of 1.63 and 13.2 μg/mL, respectively, and KPB-100 showed a nearly 2-log reduction in virus in VYR assay of VACV at 20 μg/mL. Finally, KPB-100 inhibited HHV-2 TK- at an IC₅₀ value of 4.5 μg/mL in CPE inhibition assay and HHV-1 at an IC₉₀ of 3.0 μg/mL in VYR assay.

DISCUSSION AND CONCLUSION

Both compounds are promising targets for synthetic optimization and in vivo study. KPB-100 in particular showed strong inhibition of all viruses tested.

Development of an animal model of progressive vaccinia in nu/nu mice and the use of bioluminescence imaging for assessment of the efficacy of monoclonal antibodies against vaccinial B5 and L1 proteins

Bioluminescence imaging (BLI) was used to follow dissemination of recombinant vaccinia virus (VACV) expressing luciferase (IHD-J-Luc) in BALB/c nu/nu mice treated post-challenge with monoclonal antibodies (MAbs) against L1 and B5 VACV proteins in a model of Progressive Vaccinia (PV). Areas Under the flux Curve (AUC) were calculated for viral loads in multiple organs in individual mice. Following scarification with 10⁵ pfu, IHD-J-Luc VACV undergoes fast replication at the injection site and disseminates rapidly to the inguinal lymph nodes followed by spleen, liver, and axillary lymph nodes within 2-3 days and before primary lesions are visible at the site of scarification. Extension of survival in nude mice treated with a combination of anti-B5 and anti-L1 MAbs 24 h post challenge correlated with a significant reduction in viral load at the site of scarification and delayed systemic dissemination. Nude mice reconstituted with 10⁴ T cells prior to challenge with IHD-J-Luc, and treated with MAbs post-challenge, survived infection, cleared the virus from all organs and scarification site, and developed anti-VACV IgG and VACV-specific polyfunctional CD8⁺ T cells that co-expressed the degranulation marker CD107a, and IFNγ and TNFα cytokines. All T cell reconstituted mice survived intranasal re-challenge with IHD-J-Luc (10⁴ pfu) two months after the primary infection. Thus, using BLI to monitor VACV replication in a PV model, we showed that anti-VACV MAbs administered post challenge extended survival of nude mice and protected T cell reconstituted nude mice from lethality by reducing replication at the site of scarification and systemic dissemination of VACV.

Seven major genomic deletions of vaccinia virus Tiantan strain are sufficient to decrease pathogenicity

Attenuated strain TTVAC7, as a multi-gene-deleted vaccinia virus Tiantan strain (VTT), was constructed by knocking out parts of non-essential genes related to virulence, host range and immunomodulation of VTT, and by combining double marker screening with exogenous selectable marker knockout techniques. In this study, shuttle vector plasmids pTC-EGFP, pTA35-EGFP, pTA66-EGFP, pTE-EGFP, pTB-EGFP, pTI-EGFP and pTJ-EGFP were constructed, which contained seven pairs of recombinant arms linked to the early and late strong promoter pE/L, as well as to enhanced green fluorescent protein (EGFP) as an exogenous selectable marker. BHK cells were co-transfected/infected successively with the above plasmids and VTT or gene-deleted VTT, and homologous recombination and fluorescence plaque screening methods were used to knock out the gene fragments (TC: TC7L ∼ TK2L; TA35: TA35L; TA66: TA66R; TE: TE3L ∼ TE4L; TB: TB13R; TI: TI4L; TJ: TJ2R). The Cre/LoxP system was then applied to knock out the exogenous selectable marker, and ultimately the gene-deleted attenuated strain TTVAC7 was obtained. A series of in vivo and in vitro experiments demonstrated that not only the host range of TTVAC7 could be narrowed and its toxicity weakened significantly, but its high immunogenicity was maintained at the same time. These results support the potential of TTVAC7 to be developed as a safe viral vector or vaccine.

EPIPOX: Immunoinformatic Characterization of the Shared T-Cell Epitome between Variola Virus and Related Pathogenic Orthopoxviruses

Concerns that variola viruses might be used as bioweapons have renewed the interest in developing new and safer smallpox vaccines. Variola virus genomes are now widely available, allowing computational characterization of the entire T-cell epitome and the use of such information to develop safe and yet effective vaccines. To this end, we identified 124 proteins shared between various species of pathogenic orthopoxviruses including variola minor and major, monkeypox, cowpox, and vaccinia viruses, and we targeted them for T-cell epitope prediction. We recognized 8,106, and 8,483 unique class I and class II MHC-restricted T-cell epitopes that are shared by all mentioned orthopoxviruses. Subsequently, we developed an immunological resource, EPIPOX, upon the predicted T-cell epitome. EPIPOX is freely available online and it has been designed to facilitate reverse vaccinology. Thus, EPIPOX includes key epitope-focused protein annotations: time point expression, presence of leader and transmembrane signals, and known location on outer membrane structures of the infective viruses. These features can be used to select specific T-cell epitopes suitable for experimental validation restricted by single MHC alleles, as combinations thereof, or by MHC supertypes.

Enhanced efficacy of cidofovir combined with vaccinia immune globulin in treating progressive cutaneous vaccinia virus infections in immunosuppressed hairless mice

The treatment of progressive vaccinia in individuals has involved antiviral drugs, such as cidofovir (CDV), brincidofovir, and/or tecovirimat, combined with vaccinia immune globulin (VIG). VIG is costly, and its supply is limited, so sparing the use of VIG during treatment is an important objective. VIG sparing was modeled in immunosuppressed mice by maximizing the treatment benefits of CDV combined with VIG to determine the effective treatments that delayed the time to death, reduced cutaneous lesion severity, and/or decreased tissue viral titers. SKH-1 hairless mice immunosuppressed with cyclophosphamide and hairless SCID mice (SHO strain) were infected cutaneously with vaccinia virus. Monotherapy, dual combinations (CDV plus VIG), or triple therapy (topical CDV, parenteral CDV, and VIG) were initiated 2 days postinfection and were given every 3 to 4 days through day 11. The efficacy assessment included survival rate, cutaneous lesion severity, and viral titers. Delays in the time to death and the reduction in lesion severity occurred in the following order of efficacy: triple therapy had greater efficacy than double combinations (CDV plus VIG or topical plus parenteral CDV), which had greater efficacy than VIG alone. Parenteral administration of CDV or VIG was necessary to suppress virus titers in internal organs (liver, lung, and spleen). The skin viral titers were significantly reduced by triple therapy only. The greatest efficacy was achieved by triple therapy. In humans, this regimen should translate to a faster cure rate, thus sparing the amount of VIG used for treatment.

Vaccine-induced protection against orthopoxvirus infection is mediated through the combined functions of CD4 T cell-dependent antibody and CD8 T cell responses

Antibody production by B cells in the absence of CD4 T cell help has been shown to be necessary and sufficient for protection against secondary orthopoxvirus (OPV) infections. This conclusion is based on short-term depletion of leukocyte subsets in vaccinated animals, in addition to passive transfer of immune serum to naive hosts that are subsequently protected from lethal orthopoxvirus infection. Here, we show that CD4 T cell help is necessary for neutralizing antibody production and virus control during a secondary ectromelia virus (ECTV) infection. A crucial role for CD4 T cells was revealed when depletion of this subset was extended beyond the acute phase of infection. Sustained depletion of CD4 T cells over several weeks in vaccinated animals during a secondary infection resulted in gradual diminution of B cell responses, including neutralizing antibody, contemporaneous with a corresponding increase in the viral load. Long-term elimination of CD8 T cells alone delayed virus clearance, but prolonged depletion of both CD4 and CD8 T cells resulted in death associated with uncontrolled virus replication. In the absence of CD4 T cells, perforin- and granzyme A- and B-dependent effector functions of CD8 T cells became critical. Our data therefore show that both CD4 T cell help for antibody production and CD8 T cell effector function are critical for protection against secondary OPV infection. These results are consistent with the notion that the effectiveness of the smallpox vaccine is related to its capacity to induce both B and T cell memory.

IMPORTANCE

Smallpox eradication through vaccination is one of the most successful public health endeavors of modern medicine. The use of various orthopoxvirus (OPV) models to elucidate correlates of vaccine-induced protective immunity showed that antibody is critical for protection against secondary infection, whereas the role of T cells is unclear. Short-term leukocyte subset depletion in vaccinated animals or transfer of immune serum to naive, immunocompetent hosts indicates that antibody alone is necessary and sufficient for protection. We show here that long-term depletion of CD4 T cells over several weeks in vaccinated animals during secondary OPV challenge reveals an important role for CD4 T cell-dependent antibody responses in effective virus control. Prolonged elimination of CD8 T cells alone delayed virus clearance, but depletion of both T cell subsets resulted in death associated with uncontrolled virus replication. Thus, vaccinated individuals who subsequently acquire T cell deficiencies may not be protected against secondary OPV infection.

Orthopoxvirus inhibitors that are active in animal models: an update from 2008 to 2012

Antiviral agents are being sought as countermeasures for the potential deliberate release of smallpox (variola) and monkeypox viruses, for the treatment of naturally acquired monkeypox virus infections, and as therapy for complications due to smallpox (live-attenuated vaccinia virus) vaccination or accidental infection after exposure to vaccinated persons. Reviews of the scientific literature spanning 1950-2008 have documented the progress made in developing small-animal models of poxvirus infection and identifying novel antiviral agents. Compounds of considerable interest include cidofovir, CMX001 and ST-246® (tecovirimat; SIGA Technologies, NY, USA). New inhibitors have been identified since 2008, most of which do not exhibit the kind of potency and selectivity required for drug development. Two promising agents include 4'-thioidoxuridine (a nucleoside analog) and mDEF201 (an adenovirus-vectored interferon). Compounds that have been effectively used in combination studies include vaccinia immune globulin, cidofovir, ST-246 and CMX001. In the future there may be an increase in experimental work using active compounds in combination.

Assessment of the protective effect of Imvamune and Acam2000 vaccines against aerosolized monkeypox virus in cynomolgus macaques

To support the licensure of a new and safer vaccine to protect people against smallpox, a monkeypox model of infection in cynomolgus macaques, which simulates smallpox in humans, was used to evaluate two vaccines, Acam2000 and Imvamune, for protection against disease. Animals vaccinated with a single immunization of Imvamune were not protected completely from severe and/or lethal infection, whereas those receiving either a prime and boost of Imvamune or a single immunization with Acam2000 were protected completely. Additional parameters, including clinical observations, radiographs, viral load in blood, throat swabs, and selected tissues, vaccinia virus-specific antibody responses, immunophenotyping, extracellular cytokine levels, and histopathology were assessed. There was no significant difference (P > 0.05) between the levels of neutralizing antibody in animals vaccinated with a single immunization of Acam2000 (132 U/ml) and the prime-boost Imvamune regime (69 U/ml) prior to challenge with monkeypox virus. After challenge, there was evidence of viral excretion from the throats of 2 of 6 animals in the prime-boost Imvamune group, whereas there was no confirmation of excreted live virus in the Acam2000 group. This evaluation of different human smallpox vaccines in cynomolgus macaques helps to provide information about optimal vaccine strategies in the absence of human challenge studies.

The mature virion of ectromelia virus, a pathogenic poxvirus, is capable of intrahepatic spread and can serve as a target for delayed therapy

Orthopoxviruses (OPVs), which include the agent of smallpox (variola virus), the zoonotic monkeypox virus, the vaccine and zoonotic species vaccinia virus, and the mouse pathogen ectromelia virus (ECTV), form two types of infectious viral particles: the mature virus (MV), which is cytosolic, and the enveloped virus (EV), which is extracellular. It is believed that MVs are required for viral entry into the host, while EVs are responsible for spread within the host. Following footpad infection of susceptible mice, ECTV spreads lymphohematogenously, entering the liver at 3 to 4 days postinfection (dpi). Afterwards, ECTV spreads intrahepatically, killing the host. We found that antibodies to an MV protein were highly effective at curing mice from ECTV infection when administered after the virus reached the liver. Moreover, a mutant ECTV that does not make EV was able to spread intrahepatically and kill immunodeficient mice. Together, these findings indicate that MVs are sufficient for the spread of ECTV within the liver and could have implications regarding the pathogenesis of other OPVs, the treatment of emerging OPV infections, as well as strategies for preparedness in case of accidental or intentional release of pathogenic OPVs.

Progressive vaccinia: case description and laboratory-guided therapy with vaccinia immune globulin, ST-246, and CMX001

Progressive vaccinia (PV) is a rare but potentially lethal complication that develops in smallpox vaccine recipients with severely impaired cellular immunity. We describe a patient with PV who required treatment with vaccinia immune globulin and who received 2 investigational agents, ST-246 and CMX001. We describe the various molecular, pharmacokinetic, and immunologic studies that provided guidance to escalate and then successfully discontinue therapy. Despite development of resistance to ST-246 during treatment, the patient had resolution of PV. This case demonstrates the need for continued development of novel anti-orthopoxvirus pharmaceuticals and the importance of both intensive and timely clinical and laboratory support in management of PV.

Vaccinia viruses: vaccines against smallpox and vectors against infectious diseases and tumors

Less than 200 years after its introduction, widespread use of vaccinia virus (VACV) as a smallpox vaccine has eradicated variola virus. Along with the remarkable success of the vaccination program, frequent and sometimes severe adverse reactions to VACV were encountered. After eradication, VACV has been reserved for select populations who might be at significant risk for orthopoxvirus infections. Events over the past decade have renewed concerns over the potential use of variola virus as a biological weapon. Accordingly, interest in VACV and attenuated derivatives has increased, both as vaccines against smallpox and as vectors for other vaccines. This article will focus on new developments in the field of orthopoxvirus immunization and will highlight recent advances in the use of vaccinia viruses as vectors for infectious diseases and malignancies.

Eczema vaccinatum

Eczema vaccinatum (EV) is a complication of smallpox vaccination that can occur in persons with eczema/atopic dermatitis (AD), in which vaccinia virus disseminates to cause an extensive rash and systemic illness. Because persons with eczema are deferred from vaccination, only a single, accidentally transmitted case of EV has been described in the medical literature since military vaccination was resumed in the United States in 2002. To enhance understanding of EV, we review its history during the era of universal vaccination and discuss its relationship to complications in persons with other diseases or injuries of the skin. We then discuss current concepts of the pathophysiology of AD, noting how defective skin barrier function, epidermal hyperplasia, and abnormal immune responses favor the spread of poxviral infection, and identify a number of unanswered questions about EV. We conclude by considering how its occurrence might be minimized in the event of a return to universal vaccination.

Zoonotic Brazilian Vaccinia virus: from field to therapy

Vaccinia virus (VACV), the prototype species of the Orthopoxvirus (OPV) genus, causes an occupational zoonotic disease in Brazil that is primarily associated with the handling of infected dairy cattle. Cattle and human outbreaks have been described in southeastern Brazil since 1999 and have now occurred in almost half of the territory. Phylogenetic studies have shown high levels of polymorphisms among isolated VACVs, which indicate the existence of at least two genetically divergent clades; this has also been proven in virulence assays in a mouse model system. In humans, VACV infection is characterized by skin lesions, primarily on the hands, accompanied by systemic symptoms such as fever, myalgia, headache and lymphadenopathy. In this review, we will discuss the virological, epidemiological, ecological and clinical aspects of VACV infection, its diagnosis and compounds that potentially could be used for the treatment of severe cases.

Adverse events post smallpox-vaccination: insights from tail scarification infection in mice with Vaccinia virus

Adverse events upon smallpox vaccination with fully-replicative strains of Vaccinia virus (VACV) comprise an array of clinical manifestations that occur primarily in immunocompromised patients leading to significant host morbidity/mortality. The expansion of immune-suppressed populations and the possible release of Variola virus as a bioterrorist act have given rise to concerns over vaccination complications should more widespread vaccination be reinitiated. Our goal was to evaluate the components of the host immune system that are sufficient to prevent morbidity/mortality in a murine model of tail scarification, which mimics immunological and clinical features of smallpox vaccination in humans. Infection of C57BL/6 wild-type mice led to a strictly localized infection, with complete viral clearance by day 28 p.i. On the other hand, infection of T and B-cell deficient mice (Rag1^−/−) produced a severe disease, with uncontrolled viral replication at the inoculation site and dissemination to internal organs. Infection of B-cell deficient animals (µMT) produced no mortality. However, viral clearance in µMT animals was delayed compared to WT animals, with detectable viral titers in tail and internal organs late in infection. Treatment of Rag1^−/− with rabbit hyperimmune anti-vaccinia serum had a subtle effect on the morbidity/mortality of this strain, but it was effective in reduce viral titers in ovaries. Finally, NUDE athymic mice showed a similar outcome of infection as Rag1^−/−, and passive transfer of WT T cells to Rag1^−/− animals proved fully effective in preventing morbidity/mortality. These results strongly suggest that both T and B cells are important in the immune response to primary VACV infection in mice, and that T-cells are required to control the infection at the inoculation site and providing help for B-cells to produce antibodies, which help to prevent viral dissemination. These insights might prove helpful to better identify individuals with higher risk of complications after infection with poxvirus.

Smallpox vaccine safety is dependent on T cells and not B cells

The licensed smallpox vaccine, ACAM2000, is a cell culture derivative of Dryvax. Both ACAM2000 and Dryvax are administered by skin scarification and can cause progressive vaccinia, with skin lesions that disseminate to distal sites. We have investigated the immunologic basis of the containment of vaccinia in the skin with the goal to identify safer vaccines for smallpox. Macaques were depleted systemically of T or B cells and vaccinated with either Dryvax or an attenuated vaccinia vaccine, LC16m8. B cell depletion did not affect the size of skin lesions induced by either vaccine. However, while depletion of both CD4(+) and CD8(+) T cells had no adverse effects on LC16m8-vaccinated animals, it caused progressive vaccinia in macaques immunized with Dryvax. As both Dryvax and LC16m8 vaccines protect healthy macaques from a lethal monkeypox intravenous challenge, our data identify LC16m8 as a safer and effective alternative to ACAM2000 and Dryvax vaccines for immunocompromised individuals.

Evaluation of imiquimod for topical treatment of vaccinia virus cutaneous infections in immunosuppressed hairless mice

Imiquimod is an immune response modifier prescribed as a topical medication for a number of viral and neoplastic conditions. We evaluated the antiviral activity of imiquimod against vaccinia virus (WR strain) cutaneous infections in immunosuppressed (with cyclophosphamide) hairless mice when administered after virus exposure. Primary lesions progressed in severity, satellite lesions developed, and infection eventually killed the mice. Once daily topical treatment with 1% imiquimod cream for 3, 4, or 5 days were compared to twice daily topical treatment with 1% cidofovir cream for 7 days. Survival time of mice in all treated groups was significantly prolonged compared to placebo controls. The mean day of death for the placebo group, 3-day imiquimod, 4-day imiquimod, 5-day imiquimod, and cidofovir groups were 15.5, 20.0, 20.5, 19.5, and 20.5 days post-infection, respectively. All treatment groups showed significant reductions in primary lesion size and in the number of satellite lesions. The cidofovir and 4-day imiquimod treatments delayed the appearance of lung virus titers by 3 and 6 days, respectively, although cutaneous lesion and snout virus titers were not as affected by treatment. Benefits in survival and lesion reduction were observed when imiquimod treatment was delayed from 24, 48, and 72 h post-infection. However, increasing the treatment dose of imiquimod from 1% to 5% led to a significant decrease in antiviral efficacy. These results demonstrate the protective effects of topically administered imiquimod against a disseminated vaccinia virus infection in this mouse model.

Postexposure prevention of progressive vaccinia in SCID mice treated with vaccinia immune globulin

A recently reported case of progressive vaccinia (PV) in an immunocompromised patient has refocused attention on this condition. Uniformly fatal prior to the licensure of vaccinia immune globulin (VIG) in 1978, PV was still fatal in about half of VIG-treated patients overall, with a greater mortality rate in infants and children. Additional therapies would be needed in the setting of a smallpox bioterror event, since mass vaccination following any variola virus release would inevitably result in exposure of immunocompromised people through vaccination or contact with vaccinees. Well-characterized animal models of disease can support the licensure of new products when human studies are not ethical or feasible, as in the case of PV. We chose vaccinia virus-scarified SCID mice to model PV. As in immunocompromised humans, vaccinia virus-scarified SCID animals develop enlarging primary lesions with minimal or no inflammation, eventual distal virus spread, and lethal outcomes if left untreated. Postexposure treatment with VIG slowed disease progression, caused local lesion regression, and resulted in the healthy survival of most of the mice for more than 120 days. Combination treatment with VIG and topical cidofovir also resulted in long-term disease-free survival of most of the animals, even when initiated 7 days postinfection. These results support the possibility that combination treatments may be effective in humans and support using this SCID model of PV to test new antibody therapies and combination therapies and to provide further insights into the pathogenesis and treatment of PV.

Impact of ST-246® on ACAM2000™ smallpox vaccine reactogenicity, immunogenicity, and protective efficacy in immunodeficient mice

Although a highly effective vaccine against smallpox, vaccinia virus (VV) is not without adverse events, some of which can be life-threatening, particularly in immunocompromised individuals. We have recently demonstrated that the immunogenicity and protective efficacy of Dryvax(®) in immunocompetent mice is preserved even when co-administered with ST-246, an orally bioavailable small-molecule inhibitor of orthopoxvirus egress and dissemination. In addition, ST-246 markedly reduced the reactogenicity of the smallpox vaccine ACAM2000 and the highly neurovirulent VV strain Western Reserve (VV-WR). Here, we evaluated the impact of ST-246 co-administration on ACAM2000 reactogenicity, immunogenicity, and protective efficacy in seven murine models of varying degrees of humoral and cellular immunodeficiency: BALB/c and B-cell deficient (JH-KO) mice depleted of CD4(+) or CD8(+) or both subsets of T cells. We observed that ST-246 reduced vaccine lesion severity and time to complete resolution in all of the immunodeficient models examined, except in those lacking both CD4(+) and CD8(+) T cells. Although VV-specific humoral responses were moderately reduced by ST-246 treatment, cellular responses were generally comparable or slightly enhanced at both 1 and 6 months post-vaccination. Most importantly, in those models in which vaccination given alone conferred protection against lethal VV challenge, similar levels of protection were observed at both time points when vaccination was given with ST-246. These data suggest that, with the exception of individuals with irreversible, combined CD4(+) and CD8(+) T-cell deficiency, ST-246 co-administered at the time of vaccination may help reduce vaccine reactogenicity--even in those lacking humoral immunity--without impeding the induction of protective immunity.

Direct TLR2 signaling is critical for NK cell activation and function in response to vaccinia viral infection

Natural killer (NK) cells play an essential role in innate immune control of poxviral infections in vivo. However, the mechanism(s) underlying NK cell activation and function in response to poxviruses remains poorly understood. In a mouse model of infection with vaccinia virus (VV), the most studied member of the poxvirus family, we identified that the Toll-like receptor (TLR) 2-myeloid differentiating factor 88 (MyD88) pathway was critical for the activation of NK cells and the control of VV infection in vivo. We further showed that TLR2 signaling on NK cells, but not on accessory cells such as dendritic cells (DCs), was necessary for NK cell activation and that this intrinsic TLR2-MyD88 signaling pathway was required for NK cell activation and played a critical role in the control of VV infection in vivo. In addition, we showed that the activating receptor NKG2D was also important for efficient NK activation and function, as well as recognition of VV-infected targets. We further demonstrated that VV could directly activate NK cells via TLR2 in the presence of cytokines in vitro and TLR2-MyD88-dependent activation of NK cells by VV was mediated through the phosphatidylinositol 3-kinase (PI3K)-extracellular signal-regulated kinase (ERK) pathway. Taken together, these results represent the first evidence that intrinsic TLR signaling is critical for NK cell activation and function in the control of a viral infection in vivo, indicate that multiple pathways are required for efficient NK cell activation and function in response to VV infection, and may provide important insights into the design of effective strategies to combat poxviral infections.

NK cells are an important component of innate immunity in fighting against poxviral infections in vivo. However, how NK cells are activated and exert their function in controlling poxviruses remains poorly understood. In this paper, we found that VV, the most studied member of the poxvirus family, could directly activate TLR2 on NK cells and that the direct TLR2 stimulation was critical for NK cell activation and function in the control of VV infection in vivo. We further showed that TLR2-dependent NK cell activation by VV was mediated through the PI3K-ERK pathway. In addition, we demonstrated that the activating receptor NKG2D was also required for efficient NK cell activation and function. Collectively, these results represent the first evidence that direct TLR signaling is crucial to NK cell activation and function in the control of a viral infection in vivo, indicate that multiple pathways are required for efficient NK cell activation, and may provide important insights into the design of effective strategies to combat poxviral infections.

Epidermal injury and infection during poxvirus immunization is crucial for the generation of highly protective T cell-mediated immunity

Variola major (smallpox) infection claimed hundreds of millions lives before it was eradicated by a simple vaccination strategy: epicutaneous application of the related orthopoxvirus vaccinia virus (VACV) to superficially injured skin (skin scarification, s.s.). However, the remarkable success of this strategy was attributed to the immunogenicity of VACV rather than to the unique mode of vaccine delivery. We now show that VACV immunization via s.s., but not conventional injection routes, is essential for the generation of superior T cell-mediated immune responses that provide complete protection against subsequent challenges, independent of neutralizing antibodies. Skin-resident effector memory T cells (T(EM) cells) provide complete protection against cutaneous challenge, whereas protection against lethal respiratory challenge requires both respiratory mucosal T(EM) cells and central memory T cells (T(CM) cells). Vaccination with recombinant VACV (rVACV) expressing a tumor antigen was protective against tumor challenge only if delivered via the s.s. route; it was ineffective if delivered by hypodermic injection. The clinically safer nonreplicative modified vaccinia Ankara virus (MVA) also generated far superior protective immunity when delivered via the s.s. route compared to intramuscular (i.m.) injection as used in MVA clinical trials. Thus, delivery of rVACV-based vaccines, including MVA vaccines, through physically disrupted epidermis has clear-cut advantages over conventional vaccination via hypodermic injection.

Acyclic nucleoside phosphonates with 5-azacytosine base moiety substituted in C-6 position

Two methods for preparation of 6-substituted derivatives of anti DNA-viral agent 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (HPMP-5-azaC) were developed: (1) ammonia mediated ring-opening reaction of diisopropyl esters of HPMP-5-azaC (4) to carbamoylguanidine derivatives followed by ring-closure reaction with orthoesters and (2) condensation reaction of 6-substituted 5-azacytosines with diisopropyl (1S)-[2-hydroxy-1-tosyloxymethyl)ethoxy]methylphosphonate (15). Deprotection of diisopropyl esters to free phosphonic acids was performed with bromotrimethylsilane in acetonitrile followed by hydrolysis. In contrast to parent compound HPMP-5-azaC, a substantial decrease of antiviral activity in case of 6-substituted analogues occurred. Surprisingly, N-3 isomer of 6-methyl-HPMP-5-azaC in the form of isopropyl ester revealed activity against RNA viruses (Sindbis virus).

Diverse recognition of conserved orthopoxvirus CD8+ T cell epitopes in vaccinated rhesus macaques

Vaccinia virus (VACV) induces a vigorous virus-specific CD8+ T cell response that plays an important role in control of poxvirus infection. To identify immunodominant poxvirus proteins and to facilitate future testing of smallpox vaccines in non-human primates, we used an algorithm for the prediction of VACV peptides able to bind to the common macaque MHC class I molecule Mamu-A*01. We synthesized 294 peptides derived from 97 VACV ORFs; 100 of these peptides did not contain the canonical proline at position three of the Mamu-A*01 binding motif. Cellular immune responses in PBMC from two vaccinia-vaccinated Mamu-A*01+ macaques were assessed by IFNgamma ELISPOT assays. Vaccinated macaques recognized 17 peptides from 16 different ORFs with 6 peptides recognized by both macaques. Comparison with other orthopoxvirus sequences revealed that 12 of these epitopes are strictly conserved between VACV, variola, and monkeypoxvirus. ELISPOT responses were also observed to eight epitopes that did not contain the canonical P3 proline. These results suggest that the virus-specific CD8+ T cell response is broadly directed against multiple VACV proteins and that a subset of these T cell epitopes is highly conserved among orthopoxviruses.

Ethacrynic and alpha-lipoic acids inhibit vaccinia virus late gene expression

Smallpox was declared eradicated in 1980. However recently, the need of agents effective against poxvirus infection has emerged again. In this paper, we report an original finding that two redox-modulating agents, the ethacrynic and α-lipoic acids (EA, LA), inhibit growth of vaccinia virus (VACV) in vitro. The effect of EA and LA was compared with those of β-mercaptoethanol, DTT and ascorbic acid, but these agents increased VACV growth in HeLa G cells. The inhibitory effects of EA and LA on the growth of VACV were further confirmed in several cell lines of different embryonic origin, in epithelial cells, fibroblasts, macrophages and T-lymphocytes.

Finally, we have analyzed the mechanism of action of the two agents. They both decreased expression of VACV late genes, as demonstrated by western blot analysis and activity of luciferase expressed under control of different VACV promoters. In contrast, they did not inhibit virus entry into the cell, expression of VACV early genes or VACV DNA synthesis.

The results suggest new directions in development of drugs effective against poxvirus infection.

Antiviral activity of triazine analogues of 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (cidofovir) and related compounds

Treatment of 5-azacytosine sodium salt with diisopropyl [(2-chloroethoxy)methyl]phosphonate followed by removal of ester groups with BrSi(CH3)3 afforded 1-[2-(phosphonomethoxy)ethyl]-5-azacytosine (3). Reaction of 5-azacytosine with [(trityloxy)methyl]-(2S)-oxirane followed by etherification with diisopropyl (bromomethyl)phosphonate and removal of ester groups gave 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-5-azacytosine (1). The synthesis of 6-azacytosine congener 2 was analogous using N4-benzoylated intermediates. Compound 1 was shown to exert strong activity against a broad spectrum of DNA viruses including adenoviruses, poxviruses, and herpesviruses (i.e., herpes simplex viruses, varicella zoster virus, and human cytomegalovirus). Decomposition of 1 in alkaline solutions resulted in products 17 and 18. While the N-formylguanidine derivative 17 proved active, the carbamyolguanidine derivative 18 was devoid of antiviral activity.