Lyssaviruses and rabies: current conundrums, concerns, contradictions and controversies

Lyssaviruses are bullet-shaped, single-stranded, negative-sense RNA viruses and the causative agents of the ancient zoonosis rabies. Africa is the likely home to the ancestors of taxa residing within the Genus Lyssavirus, Family Rhabdoviridae. Diverse lyssaviruses are envisioned as co-evolving with bats, as the ultimate reservoirs, over seemingly millions of years. In terms of relative distribution, overt abundance, and resulting progeny, rabies virus is the most successful lyssavirus species today, but for unknown reasons. All mammals are believed to be susceptible to rabies virus infection. Besides reservoirs among the Chiroptera, meso-carnivores also serve as major historical hosts and are represented among the canids, raccoons, skunks, mongooses, and ferret badgers.  Perpetuating as a disease of nature with the mammalian central nervous system as niche, host breadth alone precludes any candidacy for true eradication. Despite having the highest case fatality of any infectious disease and a burden in excess of or comparative to other major zoonoses, rabies remains neglected. Once illness appears, no treatment is proven to prevent death. Paradoxically, vaccines were developed more than a century ago, but the clear majority of human cases are unvaccinated. Tens of millions of people are exposed to suspect rabid animals and tens of thousands succumb annually, primarily children in developing countries, where canine rabies is enzootic. Rather than culling animal populations, one of the most cost-effective strategies to curbing human fatalities is the mass vaccination of dogs. Building on considerable progress to date, several complementary actions are needed in the near future, including a more harmonized approach to viral taxonomy, enhanced de-centralized laboratory-based surveillance, focal pathogen discovery and characterization, applied pathobiological research for therapeutics, improved estimates of canine populations at risk, actual production of required vaccines and related biologics, strategies to maximize prevention but minimize unnecessary human prophylaxis, and a long-term, realistic plan for sustained global program support to achieve success in disease control, prevention, and elimination.

Immune surveillance of human cancer: if the cytotoxic T-lymphocytes play the music, does the tumoral system call the tune?

Accumulating evidence indicates that the innate and adaptive immune systems participate in the recognition and destruction of cancer cells by a process known as cancer immunosurveillance. Tumor antigen-specific cytotoxic T-lymphocytes (CTL) are the major effectors in the immune response against tumor cells. The identification of tumor-associated antigen (TAA) recognized primarily by CD 8(+) T-lymphocytes has led to the development of several vaccination strategies that induce or potentiate specific immune responses. However, large established tumors, which are associated with the acquisition of tumor resistance to specific lysis, are usually not fully controlled by the immune system. Recently, it has become clear that the immune system not only protects the host against tumor development but also sculpts the immunogenic phenotype of a developing tumor and can favor the emergence of resistant tumor cell variants. Moreover, it has become obvious that the evasion of immunosurveillance by tumor cells is under the control of the tumor microenvironment complexity and plasticity. In this review, we will focus on some new mechanisms associated with the acquisition of tumor resistance to specific lysis during tumor progression, involving genetic instability, structural changes in cytoskeleton, and hypoxic stress. We will also discuss the interaction between CTLs and tumor endothelial cells, a major component of tumor stroma.

Expression patterns and predictive value of phosphorylated AKT in early-stage breast cancer

BACKGROUND

AKT phosphorylation is a critical step in the activation of growth factor receptors and can mediate tumor resistance to anthracyclines. We evaluated the expression patterns and predictive value of phosphorylated AKT (pAKT) in breast cancer tissues.

PATIENTS AND METHODS

pAKT expression was assessed by immunohistochemistry in 823 tumors from patients with early breast cancer enrolled in two randomized trials. The distribution of pAKT expression was correlated with HER2 and epidermal growth factor receptor (EGFR) expression. The predictive value of pAKT for the efficacy of adjuvant chemotherapy was determined by test for interaction.

RESULTS

pAKT, EGFR, and HER2 were expressed in 119 of 781 (15%), 118 of 758 (16%), and 99 of 775 (13%) assessable tumors. Staining was positive for pAKT in 28 of 99 (28%) and 90 of 676 (13%) HER2+ and HER2- tumors (P < 0.001). pAKT was expressed in 15 of 94 (16%) and 75 of 563 (13%) HER2-/EGFR+ and HER2-/EGFR- tumors, respectively (P = 0.49). A positive staining for pAKT did not correlate with prognosis (P = 0.94), and did not predict the resistance to anthracyclines (test for interaction, P = 0.70).

CONCLUSIONS

AKT phosphorylation is associated with HER2 expression but not EGFR expression in patients with early breast cancer. pAKT is not predictive for the efficacy of anthracycline-based adjuvant chemotherapy.

Efficacy of adjuvant chemotherapy according to Prion protein expression in patients with estrogen receptor-negative breast cancer

BACKGROUND

Prion protein (PrPc) has been previously reported to be associated with resistance to proapoptotic stimuli. We evaluated whether the expression of PrPc was associated with the resistance to adjuvant chemotherapy in patients with estrogen receptor (ER) -negative breast cancer.

PATIENTS AND METHODS

The expression of PrPc by primary tumors was assessed by immunohistochemistry in a series of 756 patients included in two randomized trials that compared anthracycline-based chemotherapy to no chemotherapy. The PrPc expression was correlated with ER expression and the benefit of adjuvant chemotherapy was assessed according to PrPc expression in patients with ER-negative tumors.

RESULTS

Immunostaining analysis showed that PrPc was mainly expressed by myoepithelial cells in normal breast tissue. Tissue microarray analysis from 756 breast tumors showed that PrPc was associated with ER-negative breast cancer subsets (P < 0.001). Adjuvant chemotherapy was not associated with a significant risk reduction for death in patients with ER-negative/PrPc-positive disease [adjusted hazard ratio (HR) for death = 0.98, 95% confidence interval (CI) 0.45-2.1, P = 0.95], while it decreased the risk for death (HR = 0.39, 95% CI 0.2-0.74, P = 0.004) in patients with ER-negative/PrPc-negative tumors.

CONCLUSION

These data indicate that ER-negative/PrPc-negative phenotype is associated with a high sensitivity to adjuvant chemotherapy.

Imatinib enhances human melanoma cell susceptibility to TRAIL-induced cell death: Relationship to Bcl-2 family and caspase activation

In order to define genetic determinants of primary and metastatic melanoma cell susceptibility to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), we have applied oligonucleotide microarrays to TRAIL-sensitive primary T1 cells and TRAIL-resistant metastatic G1 cells treated or not with TRAIL. T1 and G1 cells are isogenic melanoma cell subclones. We examined 22 000 spots, 4.2% of which displayed differential expression in G1 and T1 cells. Cell susceptibility to TRAIL-mediated apoptosis was found to be correlated with gene expression signatures in this model. Some of the differentially expressed genes were identified as involved in ATP-binding and signaling pathways, based on previously published data. Further analysis provided evidences that c-kit was overexpressed in G1 cells while it was absent in T1 cells. The c-kit inhibitor, imatinib, did not restore TRAIL sensitivity, excluding a role for c-kit in TRAIL resistance in G1 cells. Surprisingly, imatinib inhibited cell proliferation and TRAIL-mediated apoptosis in melanoma cells. We investigated the possible involvement of several molecules, including c-ABL, platelet-derived growth factor receptor (PDGFR), cellular FADD-like interleukin-1 alpha-converting enzyme-like inhibitory protein (c-FLIP)(L/S), Fas-associated DD kinase, p53, p21(WAF1), proteins of B-cell leukemia/lymphoma 2 (Bcl-2) family and cytochrome c. Imatinib did not modulate the expression or activation of its own targets, such as c-ABL, PDGFRalpha and PDGFRbeta, but it did affect the expression of c-FLIP(L), BCL2-associated X protein (Bax) and Bcl-2. Moreover, c-FLIP(L) knockdown sensitized T1 cells to TRAIL-mediated apoptosis, with a sensitivity similar to that of cells previously treated with imatinib. More notably, we found that the resistance to TRAIL in G1 cells was correlated with constitutive c-FLIP(L) recruitment to the DISC and the inhibition of caspase 8, 3 and 9 processing. Moreover, c-FLIP(L) knockdown partly restored TRAIL sensitivity in G1 cells, indicating that the expression level of c-FLIP(L) and its interaction with TRAIL receptor2 play a crucial role in determining TRAIL resistance in metastatic melanoma cells. Our results also show that imatinib enhances TRAIL-induced cell death independently of BH3-interacting domain death agonist translocation, in a process involving the Bax:Bcl-X(L) ratio, Bax:Bcl-X(L)/Bcl-2 translocation, cytochrome c release and caspase activation. Our data indicate that imatinib sensitizes T1 cells by directly downregulating c-FLIP(L), with the use of an alternative pathway for antitumor activity, because PDGFRalpha is not activated in T1 cells and these cells do not express c-kit, c-ABL or PDGFRbeta. Caspase cascade activation and mitochondria also play a key role in the imatinib-mediated sensitization of melanoma cells to the proapoptotic action of TRAIL.