BACKGROUND:US government organisations have identified the need for a new smallpox vaccine to replenish limited stocks of the approved, calf-lymph derived vaccine, the manufacture of which is no longer acceptable. We aimed to compare the safety and immunogenicity of the new cell-cultured smallpox vaccine (CCSV) to that of the calf-lymph derived vaccine (as a positive control) in 350 healthy, adult volunteers.METHODS:We did a randomised controlled study at the University of Kentucky Medical Center. We randomised 150 vaccinia-naive volunteers, aged 18-30 years, and 100 vaccinia-non-naive people, aged 32-65 years, to equivalent doses of either CCSV or test vaccine (2.5x10(5) plaque-forming units) by 15 puncture scarification in double-blind fashion. Immunogenicity was assessed by pock formation (take rate), humoral immune response by plaque-reduction neutralisation titres, and cellular immune response by vaccinia-specific, interferon-gamma T-cell quantification, cytotoxicity, and T-cell proliferation response. A further 100 vaccine-naive individuals, aged 18-30 years, received one of five doses of CCSV (undiluted, diluted 1 in 5, 1 in 10, 1 in 25, and 1 in 50) in single-blind fashion. Routine laboratory assessments, physical examinations, and recording of adverse events were done to assess vaccine safety. The primary endpoints were safety and reactogenicity (take rate) of CCSV.FINDINGS:349 (99.7%) of 350 volunteers developed pock lesions; one vaccinia-naive individual who received a 1 in 25 dilution of CCSV did not. The rate of adverse events related to vaccine and the extent of humoral and cellular immune responses did not differ between the vaccine groups in vaccinia-naive or non-naive people. CCSV was immunogenic in vaccine-naive volunteers at a dose 50 times lower than that approved for Dryvax.INTERPRETATION:CCSV seems to be a safe and immunogenic alternative to calf-lymph derived vaccine for both vaccinia-naive and non-naive people.

A cell culture process adaptable to produce smallpox vaccine at large scale has been developed. To achieve this, Design of Experiments (DOE) was applied to identify and optimize critical cell culture process parameters for MRC-5 cell growth and recovery during cell expansion. For cell growth, a 25−1 partial factorial (two level, five factor, 16 conditions) study was designed to evaluate the effects of basal media, seeding density, culture volume, feeding frequency and serum concentration on population doubling level (PDL) after 6–7 days in adherent T-flask cultures. Results indicated that lowering the cell density to 1×104 cells/cm2, increasing the culture volume to 0.5 ml/cm2 and increasing serum concentration to 20% significantly improved cell expansion. These findings correlated with PDLs above 2.0 and cell densities above 1×105 cells/cm2 at the end of the study period. For cell recovery at passaging, a similar DOE was used to evaluate the effect of trypsin concentration, solution temperature, duration of treatment, incubation temperature and duration of standing time between quenching and reseeding. By increasing the trypsin treatment duration to 60 min and lowering the standing time between quenching and reseeding to within 1 h, the recovery of the MRC-5 cells was greatly improved. By using these newly defined conditions, a two-fold improvement in cell expansion was consistently achieved in both roller bottles and 10 layer Nunc® Cell Factories (Cell Factories). Application of these new conditions for current Good Manufacturing Practices (cGMP) production of MRC-5 cell banks and clinical material demonstrated predictably high cell expansion as well as significantly higher production of vaccinia virus, thus providing the basis for manufacturing vaccinia virus at large scale. These findings demonstrate the need for cell culture optimization and the effectiveness of DOE to rapidly define processes suitable for cGMP manufacturing of a smallpox vaccine or other viral vaccine products.

In anticipation of large-scale smallpox vaccination, clinical trials of new vaccine candidates with improved safety profiles, and new vaccinia immune globulin (VIG) products, there is an immediate need to develop new assays to measure vaccinia-specific immune responses. The classical assay to measure vaccinia neutralization, the plaque-reduction neutralization test (PRNT), is slow, labor intensive, and difficult to validate and transfer. Here we describe the development of a novel vaccinia-neutralization assay based on the expression of a reporter gene, beta-galactosidase (beta-Gal). Using a previously constructed vaccinia-beta-Gal recombinant virus, vSC56, we developed a neutralization assay that is rapid, sensitive, and reproducible. The readout is automated. We show that the neutralizing titers, ID50, for several VIG products measured by our assay were similar to those obtained by PRNTs. A new Food and Drug Administration VIG standard was established for distribution to other laboratories. The new assay will serve as an important tool both for preclinical and clinical trials of new smallpox vaccines and for evaluation of therapeutic agents to treat vaccine-associated adverse reactions.

A series of novel unsymmetrical anthranilamide-containing HIV protease inhibitors was designed. The structure-activity studies revealed a series of potent P2-P3' inhibitors that incorporate an anthranilamide group at the P2' position. A reduction in molecular weight and lipophilicity is achieved by a judicious choice of P2 ligands (i.e., aromatic, heteroaromatic, carbamate, and peptidic). A systematic investigation led to the 5-thiazolyl carbamate analog 8 m, which exhibited a favorable Cmax/EC50 ratio (> 30), plasma half-life (> 8 h), and potent in vitro antiviral activity (EC50 = 0.2 microM).

Studies involving infectious, wild type HIV-1 must be performed under strict BSL-3 practice. We have employed a defective (deltaTat/Rev)MC99 and cloned 1A2 line, ie, mutated HIV-1 and Tat/Rev transfected cells to verify anti-HIV-1 activity in a BSL-2 laboratory. A number of extracts from various parts of 11 species of plants were studied. Results were correlated with those of an anti-HIV-1 reverse transcriptase (RT) assay.

Select chemokine receptors act as coreceptors for HIV-1 entry into human cells and represent targets for antiviral therapy. In this report we describe a distamycin analogue, 2,2'-[4, 4'-[[aminocarbonyl]amino]bis[N,4'-di[pryrrole-2-carboxamide- 1, 1'-dimethyl]]-6,8-naphthalenedisulfonic acid]hexasodium salt (NSC 651016), that selectively inhibited chemokine binding to CCR5, CCR3, CCR1, and CXCR4, but not to CXCR2 or CCR2b, and blocked chemokine-induced calcium flux. Inhibition was not due to nonspecific charge interactions at the cell surface, but was based on a specific competition for the ligand receptor interaction sites since the inhibitory effect was specific for some but not all chemoattractant receptors. NSC 651016 inhibited in vitro replication of a wide range of HIV-1 isolates, as well as HIV-2 and SIV, and exhibited in vivo anti-HIV-1 activity in a murine model. In contrast, a distamycin analogue with similar structure and charge and the monomeric form of NSC 651016 demonstrated no inhibitory effects. These data demonstrate that molecules which interfere with HIV-1 entry into cells by targeting specific chemokine coreceptors can provide a viable approach to anti-HIV-1 therapy. NSC 651016 represents an attractive candidate for the chemotherapeutic treatment of HIV-1 infection and as a microbicide to prevent the sexual transmisssion of HIV-1. Moreover, NSC 651016 can serve as a template for medicinal chemical modifications leading to more effective antivirals.

Nucleocapsid p7 (NCp7) proteins of human immunodeficiency virus type 1 (HIV-1) contain two zinc binding domains of the sequence Cys-(X)2-Cys-(X)4-His-(X)4-Cys (CCHC)1,2. The spacing pattern and metal-chelating residues (3 Cys, 1 His) of these nucleocapsid CCHC zinc fingers are highly conserved among retroviruses1,3,4. These CCHC domains are required during both the early5,6 and late7,8 phases of retroviral replication, making them attractive targets for antiviral agents. Toward that end, we have identified a number of antiviral chemotypes that electrophilically attack the sulfur atoms of the zinc-coordinating cysteine residues of the domains9–14. Such nucleocapsid inhibitors were directly virucidal by preventing the initiation of reverse transcription15 and blocked formation of infectious virus from cells through modification of CCHC domains within Gag precursors16. Herein we report that azodicarbonamide (ADA) represents a new compound that inhibits HIV-1 and a broad range of retroviruses by targeting the the nucleocapsid CCHC domains. Vandevelde et al. 17 also recently disclosed that ADA inhibits HIV-1 infection via an unidentified mechanism and that ADA was introduced into Phase I/II clinical trials in Europe for advanced AIDS. These studies distinguish ADA as the first known nucleocapsid inhibitor to progress to human trials and provide a lead compound for drug optimization.

The anti-HIV sulfonated dye, resobene, was found to be a potent inhibitor of the attachment of HIV to target cells, the fusion of envelope- and CD4-expressing cells, and the cell-to-cell transmission of virus. Resobene inhibited the infection of phenotypically distinct, established human cell lines and fresh human peripheral blood lymphocytes and macrophages by laboratory-derived isolates of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2), and a panel of biologically diverse primary clinical isolates, including syncytium-inducing and non-syncytium-inducing viruses and strains representative of the various virus clades found worldwide. The compound was also active against all drug-resistant virus isolates tested. Cell-based and biochemical mechanism of action studies demonstrated that the compound inhibits the attachment of infectious virus and fusion of virus-infected cells to uninfected target cells by binding to the cationic V3 loop of the envelope glycoprotein. Resobene effectively inhibited the infection of cell populations which do and do not express cell surface CD4. Resobene prevented infection of the cervical epithelial cell line ME180, suggesting the compound may effectively act as a topical microbicide to prevent the sexual transmission of HIV.

The bovine immunodeficiency virus (BIV) and human immunodeficiency virus types 1 and 2 (HIV-1 and -2) are members of the lentivirus genus of retroviruses. Although DNA sequences of these viruses have diverged considerably, the BIV genome organization, function of structural and regulatory genes, and replication cycle are very similar to that of HIV-1, making BIV a potentially useful model to study compounds with anti-HIV-1 activity. A cell culture-based antiviral assay was developed to test compounds for inhibition of BIV replication. The assay uses an embryonic rabbit epithelial (EREp) cell line that is highly sensitive to BIV infection and cytopathology. The 50% effective concentrations (EC50) at which the virus was inhibited in EREp cells were determined for 13 nucleoside analog, non-nucleoside, tumor-suppressive, or membrane-surface inhibitory compounds. The nucleoside analogs (3′-azido-2′,3′-dideoxythymidine, 2′,3′-dideoxyinosine and 2′,3′-dideoxycytosine), surface-membrane inhibitors (dextran sulfate, hypericin, Chicago Sky Blue and quinobene), the nucleoside reductase inhibitor (hydroxyurea), and a tumor-suppressive phorbol ester (prostratin) inhibited BIV with EC50 values similar to those derived in HIV-1 lymphocyte (CD4+)-based assays. BIV was markedly more resistant to inhibition with HIV-1-specific non-nucleoside reverse transcriptase inhibitors (NNRTIs) (thiazolobenzimidazole, oxathiin carboxanilide and thiocarbamate) than was HIV-1, which parallels results with NNRTIs in HIV-2 assays.

A biologically contained cytoprotection assay was developed to screen inhibitors of the human immunodeficiency virus without the need for high level containment or practices. The virus used has multiple point mutations that have destroyed its ability to produce both Rev and Tat, proteins essential for virus replication in vitro. The original cell line employed (CEM-SSTART) contains a genetic construct that allows for the continuous expression of both Rev and Tat, and a subclone (1A2) was developed that provides for maximum acute cytopathic effect. The National Cancer Institute's AIDS drug screening assay was used to test known drugs with both HIVIIIBvirus in the T4 lymphocytic cell line CEM-SS and mutant virus in the 1A2 subclone. This cell-based assay uses the tetrazolium salt, XTT, as an indicator of cellular metabolism after the cells have been infected with virus. The results of extensive testing have shown that the assay using mutant virus is comparable to the current NCI AIDS drug screen. After 42 days in 1A2 or CEM-SS cell culture, the virus or the integrated genome did not revert to wild-type, and the virus produced in 1A2 cells was unable to replicate in PBMCs. Mutant viral stocks were devoid of wild-type virus as determined by a PCR assay that would have found 60–600 copies of mutant RNA. These materials, which are now available to the scientific community (NIH AIDS Research and Reference Reagent Program), should be useful tools to screen and test compounds for potential inhibition of HIV in laboratories not equipped to maintain and use wild-type infectious virus.

A plant lignan, 3'-O-methyl nordihydroguaiaretic acid (3'-O-methyl NDGA, denoted Malachi 4:5-6 or Mal.4; molecular weigth 316), was isolated from Larrea tridentata and found to be able to inhibit human immunodeficiency virus (HIV) Tat-regulated transactivation in vivo, induce protection of lymphoblastoid CEM-SS cells from HIV (strain IIIB) killing, and suppress the replication of five HIV-1 strains (WM, MN, VS, JR-CSF, and IIIB) in mitogen-stimulated peripheral blood mononuclear cells, all in a dose-dependent manner. Mal.4 inhibits both basal transcription and Tat-regulated transactivation in vitro. The target of Mal.4 has been localized to nucleotides -87 to -40 of the HIV long terminal repeat. Mal.4 directly and specifically interferes with the binding of Sp1 to Sp1 sites in the HIV long terminal repeat. By inhibiting proviral expression, Mal.4 may be able to interrupt the life cycles of both wild-type and reverse transcriptase or protease mutant viruses in HIV-infected patients.

A series of novel distamycin-related polyanionic compounds were compared for their anti-HIV activity. Several were highly potent inhibitors of HIV virus-induced cell killing and viral replication of a wide variety of laboratory isolates, as well as a monocytotropic virus and a clinical isolate in human peripheral:blood lymphocytes. These compounds are structurally different from other sulfonic acid containing compounds reported to be potent inhibitors of the human immunodeficiency virus (HIV) in two respects: (1) they are structurally related to the non-toxic minor groove DNA binder distamycin; and (2) a number of them contain the aromatic phosphonic acid group. The compounds that were evaluated can be categorized into monomeric or dimeric ureido structural classes incorporating the bisamido-N-methylpyrrolenaphthalene-sulfonic acid group, with differences in the number and position of the sulfonic acids on the naphthalene rings. Broader structure-activity studies were made possible through the synthesis and evaluation of the compounds containing only a single N-methylpyrrole unit, those incorporating the N-methylpyrazole structure, and compounds having the isosteric phosphonic acid group substituted for the sulfonic acid group. One of the most potent of the inhibitors was 2,2'[4,4'[[aminocarbonyl]amino]bis[N,4'-di[pyrrole-2-carboxamide-1,1'-dimethyl]]-4,6,8 naphthalenetrisulfonic acid] hexasodium salt, NSC 651015. This compound, the phosphonic acid analog NSC 662162, and the monomeric compound NSC 651018 were studied to determine the mechanism of their inhibitory activity. Mechanistic studies revealed that inhibition was due to the disruption of virus attachment to CD4 + -susceptible cells and a further restraint on fusion of virus and cell membranes. The relative tolerance of these compounds in mice suggests that sufficient antiviral concentrations could be reached in vivo and thus may prove valuable in the treatment of AIDS patients.

Guided by the structure of HIV PR complexed with 2S,3R,4S,5S-2,5-bis[N,N'-((3-hydroxy-2-methylphenyl)carbonyl)amino] -3,4-dihydroxy-1,6-diphenyl hexane (1), a novel, achiral, non-peptidic anthranil (Ant) group was designed as a P2/P2' ligand. Symmetry-based inhibitors containing N-(2-pyridinylmethoxy-carbonyl)anthranil group are potent anti viral agents. Compounds 12 and 14 exhibited protease inhibitory activity of 60 and 70 pM, anti viral activity of 13 and 56 nM and cellular toxicity of >10 uM respectively.

Cosalane (3), a novel anti-HIV agent having a disalicylmethane unit linked to C-3 of cholestane by a three-carbon linker, was synthesized from commercially available starting materials by a convergent route. Cosalane proved to be a potent inhibitor of HIV with a broad range of activity against a variety of laboratory, drug-resistant, and clinical HIV-1 isolates, HIV-2, and Rauscher murine leukemia virus. The cytotoxicity of cosalane is relatively low as reflected by an in vitro therapeutic index of > 100. Although cosalane inhibits HIV-1 reverse transcriptase and protease, time of addition experiments indicate that it prevents the cytopathic effect of HIV by acting earlier than reverse transcription in the viral replication cycle. The available evidence indicates that the primary mechanism of action of cosalane involves inhibition of gp120-CD4 binding as well as inhibition of a postattachment event prior to reverse transcription.