Background. Nearly 20% of human cancers worldwide have an infectious etiology with the most prominent examples beinghepatitis B and C virus-associated hepatocellular carcinoma and human papilloma virus-associated cervical cancer. There is anurgent need to find new approaches to treatment and prevention of virus-associated cancers. Methodology/PrincipalFindings. Viral antigens have not been previously considered as targets for treatment or prevention of virus-associatedcancers. We hypothesized that it was possible to treat experimental HPV16-associated cervical cancer (CC) and Hepatitis Bassociatedhepatocellular carcinoma (HCC) by targeting viral antigens expressed on cancer cells with radiolabeled antibodiesto viral antigens. Treatment of experimental CC and HCC tumors with 188Re-labeled mAbs to E6 and HBx viral proteins,respectively, resulted in significant and dose-dependent retardation of tumor growth in comparison with untreated mice ormice treated with unlabeled antibodies. Conclusions/Significance. This strategy is fundamentally different from the prioruses of radioimmunotherapy in oncology, which targeted tumor-associated human antigens and promises increased specificityand minimal toxicity of treatment. It also raises an exciting possibility to prevent virus-associated cancers in chronicallyinfected patients by eliminating cells infected with oncogenic viruses before they transform into cancer.

"Virus-associated cancer" (VAC) refers to a cancer where viral infection results in the malignant transformationof the host's infected cells. Examples of viruses linked to cancers are the Epstein-Barr virus (EBV),which is associated with lymphomas, as well as nasopharyngeal and breast cancer; hepatitis B virus (HBV)and hepatitis C virus (HCV), which are both associated with hepatocellular carcinoma; and human papillomaviruses (HPVs), which are associated with cancer of the cervix. We have recently demonstrated thatHIV-1-infected cells can be eliminated in vitro and in vivo by targeting viral glycoproteins expressed on thesurface of infected cells with radiolabeled viral protein-specific monoclonal antibodies and proposed that thisapproach can be applicable to the broad range of viral infectious diseases. In VAC, the tumor cells can exhibitviral antigens both internally or on their surfaces. As a result, viral antigens in tumors represent a potentialantigenic target that is clearly different from normal tissues. In principle, these proteins could be targetedby radioimmunotherapy (RIT). In this paper, we describe the potential of this approach and reviewsome of the issues involved in the development of this approach. RIT of VAC is fundamentally different fromthe previously described uses of RIT, which have targeted tumor-associated antigens that are "self" proteins.

Borrelia burgdorferi undergoes an infectious cycle that requires adaptation to different hosts and markeddifferences in environment. B. burgdorferi copes with its different environments by regulating the expression ofproteins required for survival in specific settings. The B. burgdorferi oligopeptide permease (Opp) is one of onlya few transporters encoded by the B. burgdorferi genome. Opp proteins in other bacteria serve multipleenvironmental adaptation functions. B. burgdorferi appears to broaden the usage of this transporter by utilizingfive different substrate binding proteins (OppA proteins) that interact with the integral membrane componentsof the transporter. Expression of the OppA proteins is individually regulated and may play different roles inadaptation to host environments. Very little is known about the mechanisms used by B. burgdorferi to regulatethe expression of different OppA proteins. Here we show that the alternative sigma factors, RpoS and RpoN,regulate the expression of oppA5 but not that of other oppA genes. Using a reporter assay with Escherichia coliand gel shift binding assays, we also show that the B. burgdorferi BosR/Fur homologue interacts with the oppA4promoter and that another candidate transcription factor, EbfC, interacts with the oppA5 promoter. Bindingto the promoters was confirmed by gel shift assays. Expression of BosR/Fur in its different hosts does appearto parallel the expression of oppA4. A better understanding of the factors involved in gene regulation in B.burgdorferi will help to identify coregulated proteins that may cooperate to allow the organism to survive in aspecific environment.A

Phospholipids are an important component of bacterial membranes. Borrelia burgdorferidiffers from many other bacteria in that it contains only two major membrane phospholipids:phosphatidylglycerol (PG) and phosphatidylcholine (PC). B. burgdorferi appears to lack enzymesrequired for synthesis of PC through the well-described methylation pathway. However,B. burgdorferi does contain a gene (BB0249) with significant identity to a recently describedphosphatidylcholine synthase gene (pcs) of Sinorhizobiummeliloti.B. burgdorferi also contains a gene(BB0721) with significant identity to the gene (pgs) encoding phosphatidylglycerolphosphatesynthase, an enzyme in the synthetic pathway of PG. Activity of BB0249 was confirmed by cloningthe gene into Escherichia coli, which does not produce PC. Transformation with a plasmidcarrying BB0249 resulted in production of PC by E. coli, but only in the presence of exogenouslysupplied choline, as would be predicted for a Pcs. Because loss of Pgs activity is lethal toE. coli, activity of BB0721 was confirmed by the ability of BB0721 to complement an E. coliPgs "mutant. A plasmid containing BB0721 was transformed into a Pgs" mutant of E. coli containinga copy of the native gene on a temperature-regulated plasmid. The temperature-regulatedplasmid was exchanged for a plasmid containing BB0721 and it was shown that BB0721 wasable to replace the lost Pgs function and restore bacterial growth. This study has established theexistence and function of two critical enzymes in the synthesis of PC and PG in B. burgdorferi.Understanding of the biosynthetic pathways of PC and PG in B. burgdorferi is the first step indelineating the role of these phospholipids in the pathogenesis of Lyme disease.

The Borrelia burgdorferi genome encodes five orthologues of the substrate binding protein oligopeptidepermease A (OppA). It was previously shown that these genes are under the control of separate promoters andare differentially expressed under various environmental conditions. We were interested in determiningwhether there are also differences in substrate specificities among the proteins. The substrate specificities ofrecombinant proteins were determined by screening for high-affinity peptides by use of a combinatorial phagedisplay heptapeptide library. Different heptapeptides with high affinities for OppA-1, OppA-2, and OppA-3were identified. No heptapeptide binding OppA-4 or OppA-5 could be identified. Competitive binding assayswere performed under various conditions to determine the substrate preferences of the OppA proteins. OppA-1retained maximal activity over a broad range of pHs (5.5 to 7.5), whereas OppA-2 and OppA-3 showed peakactivities at pHs below 5.5. OppA-1 and OppA-2 showed preferences for tripeptides over dipeptides andlonger-chain peptides. Although a wide variety of amino acyl side chains were tolerated by all three OppAproteins, OppA-1 showed the broadest substrate specificity and was able to accommodate peptides composedof bulky hydrophobic residues; OppA-2 and OppA-3 showed preferences for peptides composed of smallnonpolar amino acids. All three OppA proteins showed preferences for peptides composed of L- rather thanD-amino acids. OppA-3 showed the greatest tolerance for changes in stereochemistry. Substantial differencesin the substrate specificities of the OppA proteins of B. burgdorferi suggest that they may have distinct functionsin the organism.