Partial deletion of the second hypervariable region from the envelope of the primary-like SF162 virus increases the exposure of certain neutralization epitopes and renders the virus, SF162⌬V2, highly susceptible to neutralization by clade B and non-clade B human immunodeficiency virus (HIV-positive) sera (L. Stamatatos and C. Cheng-Mayer, J. Virol. 78:7840-7845, 1998). This observation led us to propose that the modified, SF162⌬V2-derived envelope may elicit higher titers of cross-reactive neutralizing antibodies than the unmodified SF162-derived envelope. To test this hypothesis, we immunized rabbits and rhesus macaques with the gp140 form of these two envelopes. In rabbits, both immunogens elicited similar titers of binding antibodies but the modified immunogen was more effective in eliciting neutralizing antibodies, not only against the SF162⌬V2 and SF162 viruses but also against several heterologous primary HIV type 1 (HIV-1) isolates. In rhesus macaques both immunogens elicited potent binding antibodies, but again the modified immunogen was more effective in eliciting the generation of neutralizing antibodies against the SF162⌬V2 and SF162 viruses. Antibodies capable of neutralizing several, but not all, heterologous primary HIV-1 isolates tested were elicited only in macaques immunized with the modified immunogen. The efficiency of neutralization of these heterologous isolates was lower than that recorded against the SF162 isolate. Our results strongly suggest that although soluble oligomeric envelope subunit vaccines may elicit neutralizing antibody responses against heterologous primary HIV-1 isolates, these responses will not be broad and potent unless specific modifications are introduced to increase the exposure of conserved neutralization epitopes.Analysis of the crystal structure of the gp120 human immunodeficiency virus (HIV) envelope subunit indicated that neutralization epitopes are primarily clustered in one face of this protein, which is naturally occluded within the oligomeric envelope form, i.e., that present on the surface of virions and infected cells (16,37). These structural observations are supported by numerous immunochemical and virological studies (1,24,25,27,28,31,35,38,40).Several reports have indicated that specific modifications (such as deglycosylations and loop deletions) introduced in the envelope glycoproteins of HIV and simian immunodeficiency virus (SIV) may increase the exposure of neutralization epitopes. Wyatt et al. demonstrated that on the background of the HXB2 virus, a laboratory-adapted CXCR4-using (X4-using) virus, deletions of the first, second, and third hypervariable regions (V1, V2, and V3 loops, respectively) of the gp120 envelope subunit increase the exposure of epitopes participating in HIV envelope-CD4 and -coreceptor binding (38,40). Subsequently, it was demonstrated that the simultaneous deletion of the V1 and V2 loops from the envelope of this virus increases it susceptibility to neutralization by anti-V3 loop and certain CD4-induced monoclonal antibodies...

Human cytomegalovirus (HCMV) genome replication requires host DNA damage responses (DDRs) and raises the possibility that DNA repair pathways may influence viral replication. We report here that a nucleotide excision repair (NER)-associatedfactor is required for efficient HCMV DNA replication. Mutations in genes encoding NER factors are associated with xeroderma pigmentosum (XP). One of the XP complementation groups, XPE, involves mutation in ddb2, which encodes DNA damage binding protein 2 (DDB2). Infectious progeny virus production was reduced by >2 logs in XPE fibroblasts compared to levels in normal fibroblasts. The levels of immediate early (IE) (IE2), early (E) (pp65), and early/late (E/L) (gB55) proteins were decreased in XPE cells. These replication defects were rescued by infection with a retrovirus expressing DDB2 cDNA. Similar patterns of reduced viral gene expression and progeny virus production were also observed in normal fibroblasts that were depleted for DDB2 by RNA interference (RNAi). Mature replication compartments (RCs) were nearly absent in XPE cells, and there were 1.5-to 2.0-log reductions in viral DNA loads in infected XPE cells relative to those in normal fibroblasts. The expression of viral genes (UL122, UL44, UL54, UL55, and UL84) affected by DDB2 status was also sensitive to a viral DNA replication inhibitor, phosphonoacetic acid (PAA), suggesting that DDB2 affects gene expression upstream of or events associated with the initiation of DNA replication. Finally, a novel, infection-associated feedback loop between DDB2 and ataxia telangiectasia mutated (ATM) was observed in infected cells. Together, these results demonstrate that DDB2 and a DDB2-ATM feedback loop influence HCMV replication.

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6570 Vidaza and thalidomide were administered to 29 patients with MDS or AML. Vidaza was given at a dose of 75mg/kg subq × 5 days q28 days and Thalidomide starting at 50mg/day and increasing to 100mg. Therapy was well tolerated. Median age was 70 years, and there were 16 males. Two patients had RA, 2 RARS, 9 RAEB, 4 CMMoL, 10 AML and 2 Unknowns. According to IPSS, 1 had low, 7 had Int-1, 5 had Int-2 and 4 had high risk disease, and 2 unclassified (10 had AML). Eleven patients had normal, 14 abnormal and 4 unknown for cytogenetics. Seven patients went off the study due to disease progression (5) or refused therapy (1), died within a week of treatment initiation (1) while 2 are on the first cycle and too early for evaluation. Twenty-five patients are evaluable for outcome. Ten patients received 5 or more cycles of Vidaza. HI was seen in 14/25 (56%), and stable disease in 6/25 (24%) while 5/25 (20%) had disease progression. Six patients experienced complete remission (CR) and are still receiving therapy (24%), 1 experienced HI-E, 2 HI-ANC, 3 HI-P, and 2 had a bilineage improvement (HI-P and ANC and HI-E and ANC). Of 10 AML patients, three went off study due to disease progression, 1 had stable disease, 6 responded with 4 complete remissions (CR), 1 HI-ANC and 1 HI-P. Interestingly, 6/10 AMLs had a history of prior MDS, 3/6 achieved CR, 2/6 had HI (ANC and platelets) and 1 has stable disease (continuing treatment). Among the 4 de novo AMLs, 1 had CR and 3 showed disease progression. We conclude that a combination of low dose Vidaza and thalidomide is well tolerated, and highly effective therapy for the treatment of patients with MDS as well as AML arising from a prior MDS. The ability to treat secondary MDS as out-patient and achieve such a high response rate represents a paradigm shift in AML therapy. No significant financial relationships to disclose.