Hildegund C.J. Ertl, M.D.

Professor and Program Leader
Immunology Program
215-898-3863, Office
ertl@wistar.org

Introduction

The laboratory of Hildegund C.J. Ertl, M.D., is developing preventive and therapeutic vaccines for an array of infectious and noninfectious diseases, including AIDS and some forms of cancer.

Research Summary

Research in the laboratory of Hildegund C.J. Ertl centers on developing vaccines for an array of diseases and conditions - including AIDS and some forms of cancer - not typically considered to be treated using this approach. These vaccines aim to protect against future infections and look to create new therapies for diseases already affecting people. Projects fall into five broad categories: HIV vaccines, human papilloma virus vaccines, rabies vaccine models, vaccines to smallpox virus, and vaccines to brain tumors. An HIV vaccine is being developed using a genetically engineered virus from chimpanzees as the vaccine carrier to induce an immune response, especially by CD8+ T cells to HIV-1. Human papilloma virus (HPV), which causes cervical cancer, is the second most common cancer in women worldwide. Two of the virus's proteins - E6 and E7 - can cause uncontrolled cell proliferation and potentially cancer. Cervical cancer cells express these two proteins, and the researchers are using these as target antigens for active immunotherapy. The group is also working on a prophylactic vaccine to HPV-16 (designed to prevent HPV infection), a sexually transmitted virus that infects more than 20% of sexually active women in the US. Experimental HPV-16 vaccines based on virus-like particles composed of the L1 protein are currently undergoing large-scale clinical trials. Over the last 12 years the reseachers have analyzed in depth immune responses to different antigens of the rabies virus. The rabies virus model is used to establish basic immunological principles pertinent for vaccine development, in particular the far more complex HIV and HPV vaccine systems. The efficacy of tumor vaccines expressing proteins aberrantly expressed in glioblastoma is also being assessed in mouse models.

Recent Scientific Advances

Human Immunodeficiency Virus Vaccine: The Ertl laboratory, in collaboration with Drs. J. Wilson, University of Pennsylvania; R. Burnett, Wistar Institute; J. Bergelson, Children's Hospital of Philadelphia; and N. Letvin, Harvard University, is developing E1-deleted adenoviral recombinant vectors of simian origin as vaccine carriers for inducing cellular and humoral immune responses to HIV-1. These novel types of vectors have distinct advantages over previously used adenoviral recombinants of the human serotype 5 used by other groups. Most importantly, the efficacy of simian adenoviral vaccine carriers is not impaired by pre-existing neutralizing antibodies to human adenovirus serotype 5 that can be detected in up to 45% of the adult human population in the US. Furthermore, simian adenoviral recombinants tested thus far have interactions with cells of the innate immune system, most notably dendritic cells, which sponsor development of strongly biased Th1 responses suited to induce potent responses of CD8+ T cells, a subset of immunocytes that is particularly important to control the spread of HIV-1.

Human Papilloma Virus Therapeutic Vaccines: Certain types of human papillomaviruses, most notably types 16 and 18, cause cervical cancer, the second most common cancer in women worldwide. Two of the viral proteins, E6 and E7, dysregulate cell cycle control by inactivating the p53 and retinoblastoma gene products, respectively, thus initiating uncontrolled cell proliferation and potentially cancer. Cervical cancer cells express these two viral oncoproteins, which thus provide suitable target antigens for active immunotherapy. The researchers developed a set of different vaccines based on viral recombinants or DNA vaccines. These vaccines express either wild-type E6 or E7 or fusion proteins thereof designed to facilitate targeting of the proteins towards the MHC class I or II processing pathway for optimized induction of CD4 or CD8 mediated immune responses which both play a role in controlling tumor progression. The efficacy of these vaccines is being assessed in mouse tumor models. One of the vaccines - the E1-deleted adenoviral recombinant to E7 - was shown to provide near complete protection through CD8+ T cell mediated immune effector mechanisms, which are currently being analyzed in more detail. The investigators are also developing vaccines based on simian serotypes of adenovirus expressing several of the early open reading frames of HPV-16 including the E6 and the E7 oncogenes.

Prophylactic vaccines to HPV-16: HPV-16 is a sexually transmitted infectious agent that infects more than 20% of sexually active women in the U.S., thus putting them at risk for the eventual development of cervical cancer. A prophylactic vaccine, designed to prevent HPV infection, should induce both systemic and mucosal neutralizing antibodies to the major capsid protein (L1) of HPV-16. Experimental vaccines based on virus-like particles composed of the L1 protein are currently undergoing large-scale clinical trials. The laboratory developed an alternative vaccine regimen based on a DNA vaccine used for priming and an E1-deleted adenoviral recombinant for an intranasal booster, a repeated immunization, both of which express the L1 of HPV-16. This vaccine regimen induces a vaginal antibody response to conformational epitopes of the L1 of HPV-16. To further augment the efficacy of these vaccines the laboratory codon-optimized the L1 gene to enhance protein expression and is currently constructing vaccine vectors based on this optimized gene.

Rabies Virus: Over the last 12 years the laboratory has analyzed in depth immune responses to different antigens of rabies virus, a negative stranded DNA virus that is endemic in carnivores in most countries. The results of these studies formed the basis for the development of vaccines to rabies virus that upon passing pre-clinical rodent efficacy tests are now in part being tested in larger mammals.

The rabies virus model, by virtue of it being a well-characterized and simple model, serves the entire laboratory to establish basic immunological principles pertinent for vaccine development. The rabies system was used to establish that DNA vaccines could induce long-lasting protective antibody responses against intracerebral challenge with a potentially lethal virus that causes a fatal encephalitis in unvaccinated individuals. This model was also used to show that vectors encoding cytokines could modulate the immune response to DNA vaccines thus establishing the principle of genetic adjuvants.

The rabies virus model served to demonstrate that intranasal immunization with E1-deleted adenoviral recombinant vaccine induces a strong genital antibody response, which is expected to be paramount for the prevention of sexually transmitted infections. The laboratory currently uses this model to test the simian adenoviral recombinants expressing the glycoprotein of rabies for induction of humoral immune responses upon systemic or mucosal immunization.

Vaccines to brain tumors: The initial aim of these studies was to determine the efficacy of dendritic-cell-based vaccines against tumors in the central nervous system (CNS) in a mouse glioblastoma model. Immunization of mice with ex vivo expanded dendritic cells pulsed with RNA from glioblastoma cells resulted in protection of mice against intracerebral challenge with the homologous tumor cells. Vaccine efficacy was improved by co-administration of interleukin (rIL)-12. The laboratory subsequently determined that certain melanoma-associated antigens are overexpressed in glioblastoma. DNA vaccines expressing one of these antigens (i.e., TRP-2) were shown to induce protective immunity against intracerebral challenge with the glioblastoma cell line mainly through induction of CD8+ T cells. A vaccinia virus recombinant expressing the same antigen lacked efficacy. An adenoviral recombinant for TRP-2 has been developed and is currently being tested in mouse models.

Selected Publications

Kowalczyk, D. and Ertl, H.C.J. 1999. Immune responses to DNA vaccines. Cell. Mol. Life Sci. 55: 751-770.

Reddy, S.T. and Ertl, H.C.J. 1999. The potential use of DNA vaccines for neonatal immunization. Current Opinion in Molecular Therapeutics Vol. 1 (E. Hutchinson Ed.) Current Drugs Ltd., Middlesex, UK, pg. 22-29.

Xiang, Z.H. and Ertl, H.C.J. 1999. Induction of mucosal immunity with a replication-defective adenoviral recombinant. Vaccine 17: 2003-2008.

Xiang, Z.Q., Pasquini, S. and Ertl, H.C.J. 1999. Induction of genital immunity by DNA priming and intranasal booster immunization with a replication-defective adenoviral recombinant. J. Immunol. 162: 6716-6723.

Pasquini, S., Deng, H., Reddy, S.T., Giles-Davis W. and Ertl, H.C.J. 1999. The effect of CpG sequences on the B cell response to a viral glycoprotein encoded by a plasmid vector. Gene Therapy. 6:1448-1455.

Irwin, D.J., Jackson, A.C., Wunner, W.H. and Ertl, H.C.J. Basis of rabies virus neurovirulence in mice: Expression of major histocompatibility complex class I and class II mRNA in mouse brains. J. NeuroVirology 5: 485-494.

Ertl, H.C.J. 1999. Clinical Simulations: In the Management of Rabies Exposure. Sponsored by Albert Einstein College of Medicine & Montefiore Medical Center. 1: 1-16.

He, Z., Wlazlo, A.P., Kowalczyk, D., Cheng, J., Xiang, Z.Q., Giles-Davis, W. and Ertl, H.C.J. 2000. Viral Recombinant Vaccines to the E6 and E7 Antigens of HPV-16. Virology, 270: 146-161.

Oyaski, M. and Ertl, H.C.J. 2000. DNA Vaccines. Science & Medicine. 7: 30-43.

Otvos, L. Jr., Pease, A.M., Bokonyi, K., Giles-Davis, W., Rogers, M.E., Hintz, P.A., Hoffmann, R. and Ertl, H.C.J. 2000. In situ identification of T helper cell hybridoma with a cellulose-bound peptide antigen. J. Immuno. Meth. 233: 95-105.

Fields, P.A., Kowalczyk, D.W., Arruda, V.R., McCleland, M.L., Armstrong, E., Hagstrom, J.N., Pasi, K.J., Ertl, H.C.J., Herzog, R.W., High, K.A. 2000. Role of vector in activation of T cell subsets in immune responses against the secreted transgene product factor IX. Mol. Ther: J. Am. Soc. Gene Ther. 1(3): 225-35.

Tims, T. Briggs, D. J., Davis, R., Moore, S.M., Xiang, Z.Q. Ertl, H.C.J., Fu, Z.F. 2000. Dogs vaccinated with recombinant adenovirus glycoprotein develop high titers of neutralizing antibodies. Vaccine. 18(25): 2804-7.

Kowalczyk, D., Wlazlo, A.P., Giles-Davis, W., Ertl, H.C.J. 2000. Staining of antigen activated lymphocytes (SAAL): A highly specific method for amplification of tumor-specific CD8+ T cells. J. Immunol. Meth. 241: 131-139.

Otvos, Jr., L., Bokonyi, K., Varga, I., Otvos, B.I., Hoffmann, R., Ertl, H.C.J., Wade, J.D., McManus, A.M., Craik, D.J., Bulet, P. 2000. Insect peptides with improved protease-resistance protect mice against bacterial infection. Protein Science. 9: 742 - 749.

Wlazlo, A.P. Giles-Davis, W., Clements, A., Strubble, G., Marmorstein, R. and Ertl, H.C.J. 2001. Generation and characterization of monoclonal antibodies against the E6 and E7 oncoproteins of HPV-16. Hybridoma, 20: 257- 263.

Kowalczyk, D., Wlazlo, A.P., Shane, S., Ertl, H.C.J. 2001.Vaccine regimen for prevention of sexually transmitted human papillomavirus type 16. Vaccine 19: 3583-3590.

Reyes-Sandoval, A. and Ertl, H.C.J. 2001. DNA Vaccines. Curr. Mol. Med. 1: 217-243.

Wlazlo, A.P. and Ertl, H.C.J. 2001. DNA Tumor Vaccines. AITE 49:1-11.

Kowalczyk, D., Wlazlo, A., Blaszczyk-Thurin, M., Xiang, Z.Q., Giles-Davis, W., Ertl, H.C.J. 2001. A method that allows easy characterization of tumor-infiltrating lymphocytes. J. Immuno. Meth. 253: 163-175.

Farina, S.F., Gao, G., Xiang, Z.Q., Rux, J.J., Burnett, R.M., Alvira, M.R., Marsh, J., Ertl, H.C.J., Wilson, J.M. 2001. A replication defective vector based on a chimpanzee adenovirus. J. Virol. 75: 11603-13.

Xiang, Z.Q., Gao, G., Reyes-Sandoval, A., Cohen, C.J., Li, Y., Bergelson, J.M., Wilson, J.M., Ertl, H.C.J. 2002. Novel, adenoviral vaccine carrier based on the chimpanzee serotype 68 for induction of antibodies to a transgene product. J. Virol. 76: 2667-2675.

Blaszczyk-Thurin, M., O, I., Ertl, H.C.J. 2002. An experimental vaccine expressing wild-type p53 for prevention of cancer. Scand. J. Immunol. 56: 361-375.

Cohen, C.J., Xiang, Z.Q., Gao, G.P., Ertl, H.C.J., Wilson, J.M., and Bergelson, J.M. 2002. Chimpanzee adenovirus 68 adapted as a gene delivery vector interacts with the coxsackievirus and adenovirus receptor. J. Gen. Virol. 83: 151-155.

Kammer, A.R. and Ertl, H.C.J. 2002. Rabies Vaccines: From the Past to the 21st Century. Hybridoma and Hybridomics 21: 123-127.

Lees, C.Y., Briggs, D.J., Wu, X., Davis, R.D., Moore, S.M., Gordon, C., Xiang, Z., Ertl, H.C., Tang, de C.C., Fu, Z.F. 2002. Induction of protective immunity by topic application of a recombinant adenovirus expressing rabies virus glycoprotein. Veterinary Microbiology. 85: 295-303.

Cudic, M., Ertl, H.C.J., and Otvos, Jr., L. 2002. Synthesis, conformation and T-Helper cell stimulation of an O-linked glycoprotein epitope containing extended carbohydrate side-chains. Bioorganic and Medicinal Chem. 10: 3859-3870.

O, I., Ku, G., Ertl, H.C.J. and Blaszczyk-Thurin, M. 2002. A dendritic cell vaccine induces protective immunity to intracranial growth of glioma. Anticancer Res. 22: 613-621.

Cudic, M., Ertl, H.C.J., Otvos. L. 2002. Synthesis, conformation and T helper cell stimulation of an o-linked glycopeptide epitope containing extended carbohydrate side-chains. Bioorg. Med. Chem. 10: 3859 - 38-70.

Ertl, H.C.J. 2002. Viral Immunology. In Fundamental Immunology, W.E. Paul, ed. Lippincott, Williams and Wilkins, Philadelphia, PA.

Vinner, L., Wee, E.G.T., Patel, S., Corbet, S., Gao, G.P., Therrien, D., Nielsen, C., Wilson, J.M., Ertl, H.C., Hanke, T., Fomsgaard, A. 2002. Immunogenicity in Mamu-A01 Rhesus Macques of a CR5-Tropic HIV-1 envelop from the primary isolate (Bx08) after synthetic DNA prime and recombinant adenovirus-5 boost. Statens Serum Institut web communiqué.

Deng, H., Kowalczyk, D.W., O, I., Blaszczyk-Thurin, M., Xiang, Z.Q., Giles-Davis, W., and Ertl, H.C.J. 2002. A modified DNA vaccine to p53 induces protective immunity to challenge with a chemically induced sarcoma cell line. Cell. Immunol. 215: 20-31.

Ertl, H.C.J. 2003. Cytokines and immunomodulatory ligands as genetic adjuvants. DNA Vaccines, Ertl, H.C.J., ed. Landes Biosciece, Houston, TX & Kluwer Academic, Plenum Publishers, New York, NY.

DNA Vaccines. 2003. Ertl, H.C.J., ed. Landes Biosciece, Houston, TX & Kluwer Academic, Plenum Publishers, New York, NY.

Jackson, A.C., Mary J. Warrell, M.J., Rupprecht, C.E., C. J. Ertl, H.C., Dietzschold, B., O'Reilly, M., Leach, R.P., Fu, Z.F., Wunner, W.H., Bleck, T.P., and Wilde, H. 2003. Management of rabies in humans. Clin. Infect. Dis. 36: 60-63.

Fitzgerald, J., Gao, G.P., Reyes-Sandoval, A., Pavlakis, G.N., Xiang, Z.Q., Wlazlo, A.P., Giles-Davis, W., Wilson, J., and Ertl, H.C.J. 2003. A simian replication-defective adenoviral recombinant vaccine to HIV-1 gag. J. Immunol 170: 1416-1422.

Z. Q. Xiang, G. P. Gao, Y. Li, J. M. Wilson, and H. CJ. Ertl. 2003. T Helper cell-independent antibody responses to the transgene product of the E1-deleted adenoviral vaccine require NK1.1 T cells. Virology, 305: 397-405.