Prevention of Liver Cancer and Cirrhosis by Vaccines

Dynamic equilibrium of Marek's disease genomes during in vitro serial passage

Attenuation of Gallid herpesvirus-2 (GaHV-2), the causative agent of Marek's disease, can occur through serial passage of a virulent field isolate in avian embryo fibroblasts. In order to gain a better understanding of the genes involved in attenuation and associate observed changes in phenotype with specific genetic variations, the genomic DNA sequence of a single GaHV-2 virulent strain (648A) was determined at defined passage intervals. Biological characterization of these "interval-isolates" in chickens previously indicated that the ability to induce transient paralysis was lost by passages 40 and the ability to induce persistent neurological disease was lost after passage 80, coincident with the loss of neoplastic lesion formation. Deep sequencing of the interval-isolates allowed for a detailed cataloguing of the mutations that exist within a single passage population and the frequency with which a given mutation occurs across passages. Gross genetic alterations were identified in both novel and well-characterized genes and cis-acting regions involved in replication and cleavage/packaging. Deletions in genes encoding the virulence factors vLipase, vIL8, and RLORF4, as well as a deletion in the promoter of ICP4, appeared between passages 61 and 101. Three mutations in the virus-encoded telomerase which predominated in late passages were also identified. Overall, the frequency of mutations fluctuated greatly during serial passage and few genetic changes were absolute. This indicates that serial passage of GaHV-2 results in the generation of a collection of genomes with limited sequence heterogeneity.

Comparative full-length sequence analysis of oncogenic and vaccine (Rispens) strains of Marek's disease virus

The complete DNA sequence of the Marek's disease virus serotype 1 vaccine strain CVI988 was determined and consists of 178 311 bp with an overall gene organization identical to that of the oncogenic strains. In examining open reading frames (ORFs), nine differ between vaccine and oncogenic strains. A 177 bp insertion was identified in the overlapping genes encoding the Meq, RLORF6 and 23 kDa proteins of CVI988. Three ORFs are predicted to encode truncated proteins. One, designated 49.1, overlaps the gene encoding the large tegument protein UL36 and encodes a severely truncated protein of 34 aa. The others, ORF5.5/ORF75.91 and ORF3.0/78.0, located in the repeat regions (diploid), encode a previously unidentified ORF of 52 aa and a truncated version of the virus-encoded chemokine (vIL-8), respectively. Subtle genetic changes were identified in the two ORFs encoding tegument proteins UL36 and UL49. Only one diploid ORF (ORF6.2/ORF75.6) present in the genomes of the three virulent strains is absent in the CVI988-BAC genome. Seventy non-synonymous amino acid substitutions were identified that could differentiate CVI988-BAC from all three oncogenic strains collectively. Estimates of the non-synonymous to synonymous substitution ratio (ω) indicate that CVI988 ORFs are generally under purifying selection (ω<1), whereas UL39, UL49, UL50, RLORF6 and RLORF7 (Meq) appear to evolve under relaxed selective constraints. No CVI988 ORF was found to be under positive evolutionary selection (ω≫1).

Hepatocellular carcinoma: updates in primary prevention

Hepatocellular carcinoma is a significant cause of mortality worldwide and a growing problem in the United States. Treatment options are often limited, and median survival is less than 1 year. Thus, prevention may provide the best opportunity to alter the natural history of this disease. Primary prevention is best exemplified by the successes of such public health measures as universal hepatitis B vaccination. Such antiviral therapies as interferon may also have a role. Lessons can be learned from complementary and alternative medicine. Nevertheless, more work is needed in understanding hepatocarcinogenesis and in developing models to assess potential chemopreventive agents.

Tumor-associated antigens: from discovery to immunity

There is a renewed enthusiasm for therapeutic vaccination as a viable treatment for patients with cancer. Early tumor vaccines were comprised of whole tumor cells, fragments of tumor cells, or protein lysate from tumor cells. Limited results with these approaches led investigators to begin developing the next generation of cancer vaccines based on defined tumor-associated antigens (TAAs). Defining and characterizing TAAs for human cancer, development of new approaches for identifying TAAs, and novel strategies to deliver the antigens as potent therapeutic vaccines have all been the focus of intense research in the past decade and will continue to be the focus for decades to come.

Immunoprophylaxis of hepatitis C virus infection

Because hepatitis C virus is etiologically involved in about half the cases of the world's most common cancer, hepatocellular carcinoma, and because this virus is likely to continue to spread in most of the developing world for many years, the authors believe that development of a prophylactic vaccine is imperative. Numerous approaches are available to overcome the many impediments which make the development of an HCV vaccine difficult. Such impediments include the many viral genotypes and quasispecies of HCV and the association of virions with host lipids. It is likely that overcoming these impediments will require a vaccine which induces a strong cell-mediated response. The most promising approach seems to be DNA-based immunization or a prime-boost regimen with DNA priming and boosting with a viral vector. Potentiation of responses with adjuvant strategies will probably be necessary. Hepatitis C virus immunization is in an early stage of development. Given the explosive growth in the understanding of immunology, progress should be rapid.

Primary and metastatic liver cancer

OBJECTIVES

To review liver physiology, the disease process, diagnostic tests, and current treatment options for primary and metastatic liver cancer.

DATA SOURCES

Research studies, review articles, and textbooks relating to liver cancer.

CONCLUSIONS

Surgical resection offers the best available treatment modality, but only a small percentage of patients are eligible. However, combined treatment of radiation therapy and chemotherapy (systemic and intra-arterial), as well as chemoembolization, cryosurgery, and transplantation, offers hope of palliation, conversion of unresectable to resectable disease, and prolonged survival.

IMPLICATIONS FOR NURSING PRACTICE

Understanding and knowledge of the disease process and treatment modalities for primary and metastatic liver cancer will assist the oncology nurse in educating patients and families during their diagnostic and treatment phases.

Is infection control an academic study?

This editorial aims to answer the question of whether infection control is an academic specialty. By considering the consequences of a lack of infection control in terms of patient morbidity and mortality and hence cost, it is easy to establish the importance of the area. Infection control embraces not only developing policies for preventing the physical spread of a micro-organism but also prophylactic therapy such as vaccination and therapeutic measures such as antibiotics. Infection control not only applies to localized infection in hospital due to antibiotic resistant microbes but also to the community. Bacteria such as Helicobacter pylori and Chlamydia pneumoniae and the viruses hepatitis B, hepatitis C, human lymphotropic virus type 1, Epstein-Barr viruses and human papilloma virus have been implicated in diseases not previously thought to have an infectious origin. Coping with these problems is clearly an academic area.