Our Science – Arthur Website

Larry O. Arthur, Ph.D.

AIDS and Cancer Virus Program Head, Retroviral Vaccine Section Associate Director SAIC-Frederick, Inc. NCI-Frederick Building 535, Suite 511 Frederick, MD 21702-1201 Phone:   301-846-1408 Fax:   301-846-5588 E-Mail:   arthur@ncifcrf.gov

Biography

Dr. Arthur obtained his Ph.D. in 1970 from Louisiana State University in Baton Rouge. He has been involved in research on retroviruses since 1973 and has been conducting research on AIDS and HIV-1 since 1984. Before becoming director of the AIDS Vaccine Program, SAIC-Frederick, he was head of the Biological Products Laboratory at NCI-Frederick. Currently, Dr. Arthur is the Principal Investigator of the OTS Contract at NCI Frederick and the Associate Director of the AIDS Vaccine Program.

Research

Most of the vaccine-directed research of the AVP is centered on the novel method for the inactivation of retroviruses that was developed by AVP scientists. While historically, killed whole particle viral vaccines have been among the most widely used and efficacious in preventing spread of viral diseases, inactivated viral vaccines have received comparatively little attention in AIDS vaccine research. This is primarily due concerns about safety, and the observation that use of conventional viral inactivation approaches (chemical cross linking, heating) applied to HIV gives largely denatured immunogens that do not induce good protective responses. The novel inactivation approach we developed was a direct result of more than a decade of basic research by our group, studying the nucleocapsid (NC) proteins of retroviruses, coupled with a fundamental interest in vaccines. The method builds on basic studies that characterized the NC proteins of retroviruses, showing their cysteines coordinate zinc and are reactive with a number of compounds, including mild oxidizing agents. We recognized that the virion internal proteins contain cysteines susceptible to oxidation while the virion surface proteins exist in disulfide linkages (S-S) and are thus already oxidized. This raised the possibility that mild oxidizing agents could be used to covalently modify and functionally inactivate key internal structural proteins, eliminating infectivity, while preserving the structural and functional integrity of the virion envelope glycoproteins. Experimental testing validated this hypothesis since mild oxidizing agents were found to eliminate virus infectivity while preserving functional envelope glycoproteins.

While numerous mild oxidizing agents have been shown effective in inactivating HIV-1 and SIV via this mechanism, we have found 2,2'-dithiodipyridine (Aldrithiol-2, AT-2) to be particularly useful, based on its activity, solubility, availability and low cost. Viruses inactivated by this process have been used extensively as reagents and as prototype immunogens in vaccine-challenge experiments in macaques by AVP scientists and investigators worldwide. Upon approval by the NCI-Frederick AIDS Reagent Committee concentrated, purified, inactivated viruses are made widely available to requesting AIDS researchers at no cost to the investigator.
HIV and SIV virions inactivated with AT-2 are being evaluated in preclinical studies as candidate vaccine immunogens. As noted above, one of the distinguishing features of this class of novel inactivated virion is the presence of functional envelope glycoproteins on the surface of the virions. The presence of native, trimeric envelope glycoproteins on these virions may serve as a preferred immunogen for the generation of neutralizing antibody responses, particularly responses to conformational epitopes. The presence of conformationally and functionally intact envelope glycoproteins also appears to be important for interactions of inactivated virions with antigen presenting cells and cross presentation. Since the mechanism of retroviral inactivation by AT-2 is a general one, the procedure can be used to inactivate any retrovirus having a zinc finger-containing nucleocapsid protein. Inactivated virions prepared from panels of selected virus isolates can thus be used to systematically analyze the influence of quantitative and qualitative modifications of the envelope glycoproteins of these inactivated virions on immunogenicity (humoral and cellular), and protective efficacy. We are therefore using AT-2 inactivated virions as a common technical platform to study the influence of virion envelope glycoprotein content, and engineered modifications of envelope glycoproteins (removal of carbohydrate attachment sites, deletion of variable loops, etc.) on immunogenicity and protective efficacy. Observations obtained in this convenient format may provide insights relevant to other vaccine strategies including perhaps protein subunit, DNA immunization, and recombinant virus vaccines. Our applied studies of inactivated virions having different envelope properties are being complemented by more basic studies of the determinants of virion envelope glycoprotein content, and investigation of the possible in vivo pathogenic consequences of different levels of virion envelope glycoprotein content.

We have demonstrated that AT-2 inactivation is a robust procedure and have documented the completeness of inactivation of detectable infectivity, both in vitro and in non-human primates. However, both regulatory requirements and prudence dictate that AT-2 inactivation be combined with at least one other inactivation method for contemplated clinical use. We are thus actively evaluating additional inactivation methods that are compatible with AT-2 treatment and, like AT-2, mediate effective inactivation, while also preserving functional envelope glycoproteins on the inactivated virions. We have identified some promising approaches that, in preliminary evaluation, seem to meet these requirements.
Our collaborators: Dr. Ron Desrosiers, Harvard Medical School/New England National Primate Research Center
Dr. James Hoxie, University of Pennsylvania
Dr. Chris Petropolous, University of California, Davis/California National Primate Research Center
Dr. James Hildreth, Johns Hopkins University Medical School
Dr. Ken Roux, Florida State University
Dr. Haynes Sheppard, Dept. of Health Services, State of California
Dr. Raoul Benveniste, NCI
Drs. Hilton White and Steve Kaye, MRC, Gambia

This page was last updated on 7/23/2008.