Vaccines for emerging pathogens: from research to the clinic

In this two-part series of reviews, we have invited experts in their fields to contribute articles on the status of vaccine research and development for emerging pathogens. This topic has been brought into sharp focus in recent years following significant outbreaks of viral diseases such as those causing severe acute respiratory syndrome and Middle East respiratory syndrome, as well as devastating outbreaks of diseases caused by the Ebola, Marburg, Zika and Lassa fever viruses, to name only a few examples. Additionally, bacterial infections leading to bubonic and pneumonic plague, most notably in Madagascar in 2018, as well as malaria in many tropical countries, melioidosis in south east Asia and tularaemia in northern Europe and North America, have incurred significant morbidity and mortality. In this review series, the life cycle of these pathogens and the epidemiology of disease have been reviewed in the context of potential points of intervention for the prevention of human infection. Many of the emerging pathogens are zoonoses and, as such, there is scope for intervention at the animal/insect/environmental reservoir. Other pathogens covered in this review series are considered to be re-emerging, such as multi-drug resistant tuberculosis.

[Investigation of hepatitis G virus prevalence in hemodialysis patients and blood donors in Denizli, Turkey]

This study focuses on the prevalence of hepatitis G virus (GBV-C/HGV) in hemodialysis patients and blood donors in Denizli (located at Aegean region of Turkey). A total of 100 patients (mean age: 56.8 +/- 13.3 years; 46 female) receiving hemodialysis and 100 blood donors (mean age: 31.3 +/- 8.1 years; 8 female) were included in the study. The presence of GBV-C/HGV RNA was determined in all patients by reverse transcriptase-PCR and the presence of GBV-C/HGV anti-E2 antibodies was determined by a commercial enzyme immunoassay (Diagnostic Automation, INC). Viral RNA positivity was determined in 14 (14%) of the hemodialysis patients and 2 (2%) of the blood donors, the difference being statistically significant (p < 0.05). GBV-C/HGV anti-E2 antibodies were detected in 1 (1%) of the hemodialysis patients and 3 (3%) of the blood donors. Anti-E2 positive patient also revealed positive result for viral RNA. There was no statistically significant difference between the two groups in terms of anti-E2 positivity. The prevalence of GBV-C/HGV was 14% in hemodialysis patients and 5% in blood donors (p < 0.05). There was no significant difference in terms of duration of hemodialysis, serum ALT levels, age or gender between GBV-C/HGV positive and negative hemodialysis patients. In conclusion, since hemodialysis patients are at an increased risk of parenteral transmission, they have significantly higher GBV-C/HGV viremia rates and prevalence when compared to blood donors. However, the prevalence of GBV-C/HGV and coexistence between GBV-C/HGV and hepatitis C virus have been decreasing in our region owing to increased hygienic precautions in hemodialysis units, avoidance of unnecessary blood transfusions and more widespread use of erythropoietin.

Recent advances in the treatment of viral hepatitis

The viral hepatitis viruses and the diseases they cause are presented in terms of their importance to the practice of dentistry. Each virus will be discussed in terms of its epidemiology, risk of transmission in dentistry, and steps that can be taken to avoid transmission. The scope of this review emphasizes publications from 1996-1999.

[Investigation of hepatitis G virus and human immunodeficiency virus infections in 831 healthy youths]

Antibodies to hepatitis G virus(HGV) and human immunodeficiency virus(HIV) by EIA were investigated in 831 healthy youths from 6 provinces. The results showed that the anti-HGV IgG positive rate was 2.53% (21/831). In 21 anti-HGV IgG positive sera, HGV RNA was detected in 8 sera by reverse transcription polymerase chain reaction(RT-PCR). The anti-HIV was negative in 827 sera. The data suggest that HGV infection actually exist in healthy youths.

Defective adenoviruses as novel vaccines for the Flaviviridae

BACKGROUND

Vaccines against many flaviviruses, such as Japanese encephalitis virus (JEV), yellow fever virus (YFV) and tick-borne encephalitis virus (TBEV), have been successfully used for many years. Other diseases such as dengue fever (DF) and hepatitis C are still major public health problems as no licensed vaccines are in use.

OBJECTIVES

To review studies on the use of defective recombinant adenoviruses (Rads) as experimental flavivirus vaccines and comment on their use to prevent infections with other members of the Flaviviridae such as hepatitis C virus.

STUDY DESIGN

Recombinant adenoviruses, defective in their replication strategy, contain deletions in the E1 and E3 regions of the genome to increase the amount of foreign genetic material that can be inserted. The expression of foreign genes, inserted into these regions, can be driven by the adenovirus's own promoter, or by an additional viral promoters.

CONCLUSIONS

Rads have been successfully used to raise protective immunity in experimental models of infection with several viruses. They can elicit both humoral and cell-mediated immunity and can be given parenterally or by oral administration. In addition, their hepatotropism makes them suitable for tackling diseases such as hepatitis C. Careful design of the vaccine vectors is advised to ensure their efficacy and safety, and as hepatitis C is a persistent infection, it may be advisable to design Rads containing genes encoding for non-structural proteins in preference to structural proteins.

The first Flaviviridae symposium

The first annual Flaviviridae Symposium, sponsored by ICN Pharmaceuticals Inc., was held in Lyon, France, on 9 October, 1997, to communicate current understanding on the Flaviviridae. This multidisciplinary symposium attracted over 300 international delegates and presentations covered virology, viral pathogenesis, potential therapies and strategies for vaccine development. The symposium reviewed the research area that may lead to the discovery and design of human and veterinary medicines against members of this virus family.

Optimization of vaccine production for animal health

Vaccines on the basis of mammalian cell cultures are of major importance for human and animal health. Therefore efforts are undertaken for the improved production of more effective vaccines. Of course, the main purpose of all these approaches is to save lives and improve the quality of life for human beings. However, there is also some remarkable effort in the food industry and the associated animal production, especially in the case of some Flaviviridal viruses (BVD), where > 80% of all cattle herds are found to be infected. These viruses can cause tremendous economic losses of calfs and embryos (Ames, 1990). Because of these facts, there is a continuous endeavour for improving the manufacturing of therapeutics or preventing agents such as vaccines for the treatment of cattle. The competitive economic situation and the specific market demands still require effective and high yield production methods, especially in the case of one of the most widespread viral diseases in cattle like BVD (Ames, 1990). We have succeeded in establishing an improved method for the production of BVD on the basis of a continuous fermentation mode, that consist of modifications of the corresponding process and media improvements.