Transplacental drug delivery: gene and virus delivery to the trophoblast

Viruses and Virus-Like Particles in Biotechnology: Fundamentals and Applications

Although viruses are simple biological systems, they are capable of evolving highly efficient techniques for infecting cells, expressing their genomes, and generating new copies of themselves. It is possible to genetically manipulate most of the different classes of known viruses in order to produce recombinant viruses that express foreign proteins. Recombinant viruses have been used in gene therapy to deliver selected genes into higher organisms, in vaccinology and immunotherapy, and as important research tools to study the structure and function of these proteins.

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome. They have been applied not only as prophylactic and therapeutic vaccines but also as vehicles in drug and gene delivery and, more recently, as tools in nanobiotechnology.

In this chapter, basic and advanced features of viruses and VLPs are presented and their major applications are discussed. The different production platforms based on animal cell technology are explained, and their main challenges and future perspectives are explored. The implications of large-scale production of viruses and VLPs are discussed in the context of process control, monitoring, and optimization. The main upstream and downstream technical challenges are identified and discussed accordingly.

Viruses and Virus-Like Particles in Biotechnology

Although viruses are simple biological systems, they are capable of evolving highly efficient techniques for infecting cells, expressing their genomes, and generating new copies of themselves. It is possible to genetically manipulate most of the different classes of known viruses in order to produce recombinant viruses that express foreign proteins. Recombinant viruses have been used in gene therapy to deliver selected genes into higher organisms, in vaccinology and immunotherapy, and as important research tools to study the structure and function of these proteins.

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome. They have been applied not only as prophylactic and therapeutic vaccines but also as vehicles in drug and gene delivery and, more recently, as tools in nanobiotechnology.

In this article, basic and advanced features of viruses and VLPs are presented and their major applications are discussed. The different production platforms based on animal cell technology are explained, and their main challenges and future perspectives are explored. The implications of large-scale production of viruses and VLPs are discussed in the context of process control, monitorization, and optimization. The main upstream and downstream technical challenges are identified and discussed accordingly.

The effect of over-expression of sFlt-1 on blood pressure and the occurrence of other manifestations of preeclampsia in unrestrained conscious pregnant mice

OBJECTIVE

It has been shown that the level of soluble fms-like tyrosine kinase-1 (sFlt-1) is elevated in pregnant women who are destined to have preeclampsia, and a role for sFlt-1 in its pathogenesis has been suggested. Our objective was to determine the effect of the over-expression of sFlt-1 on blood pressure and the occurrence of other manifestations of preeclampsia in pregnant mice.

STUDY DESIGN

At day 8 of gestation CD-1 mice were allocated randomly to an injection of an adenovirus carrying sFlt-1 (10(9) plaque-forming units; sFlt-1 group), adenovirus carrying the murine immunoglobulin G2alpha Fc fragment (10(9) plaque-forming units; mFc group used as a control for the virus) or saline solution (100 microL; saline group). At day 10 of gestation, blood pressure catheters were inserted through the left carotid artery into the aortic arch and tunneled to a telemetric transmitter. Blood pressure was monitored continuously in the conscious unrestrained animals until day 18. Blood was collected from the pregnant mice at different gestational times, and plasma sFlt-1 was measured by enzyme-linked immunosorbent assay. Pups and placentae were weighed, and maternal platelet counts were determined at death on day 18.

RESULTS

Plasma levels of sFlt-1 increased significantly in the sFlt-1 mice and were significantly higher than the 2 control groups. The mean blood pressure in the sFlt-1 mice was significantly higher on days 17 and 18 of gestation, compared with the mFc and saline solution groups. The time-course of blood pressure rise mirrored that of the sFlt-1 levels. The average pup weight, placental weight, and maternal platelet counts were significantly lower in the sFlt-1 group, compared with the controls.

CONCLUSION

SFlt-1 induces hypertension and fetal growth restriction in pregnant mice, which supports its hypothesized role in the pathogenesis of preeclampsia. This animal model minimizes the need for manipulation or the administration of various compounds to induce the condition.

Comparison of transgene expression mediated by several Fiber-modified adenovirus vectors in trophoblast cells

The transfer of genes of interest is a useful method for studying placental biology. Recombinant adenovirus (Ad) vector is an efficient vector for transgene expression. An interaction between the fiber of Ad and the coxsackievirus and adenovirus receptor on the cell membrane is the first step in infection. We previously developed fiber-modified Ad vectors and showed that they improved transgene activity in several cell lines when compared to wild-type vector. In the present study, we examined the ability of three fiber-modified Ad vectors to transduce human choriocarcinoma cell lines (JEG-3, JAR and BeWo) and rat trophoblast cell lines (Rcho-1, TR-TBT 18d-1 and TR-TBT 18d-2). We compared the transgene efficacy of wild-type Ad-L2 vector, Ad-RGD(HI)-L2 vector containing an Arg-Gly-Asp motif, Ad-K7(C)-L2 vector containing a 7-tandem lysine motif, and Ad-RGD(HI)K7(C)-L2 vector containing both motifs in the fiber. We used the luciferase gene as a reporter gene. In the human and rodent trophoblast cell lines, Ad-RGD(HI)-L2 had the greatest infectious potential, followed by Ad-RGD(HI)K7(C)-L2, Ad-K7(C)-L2 and Ad-L2. Compared to the amount of luciferase produced by wild-type vector, Ad-RGD(HI)-L2 mediated 8.1-fold the amount of luciferase in JEG-3 cells, 13.5-fold in JAR cells, 76.8-fold in BeWo cells, 5.0-fold in Rcho-1, 19.4-fold in TR-TBT 18d-1 and 15.0-fold in TR-TBT 18d-2. These results indicate that Ad-RGD(HI) is a potential recombinant Ad vector for transgene expression in some trophoblast cell lines.

Controlling drug delivery across the placenta

A challenge in modern drug therapy is to develop strategies for safer and more selective targeting of drug delivery in pregnancy. Specifically, approaches are needed that would restrict unnecessary drug exposure to either mother or fetus. There is evidence emerging that indicates the placenta does express natural transport and metabolism processes that function to control drug and nutrient distribution between the mother and fetus. Further, in vitro techniques developed in the past 10 years now provide some of the tools necessary to elucidate transport and metabolism processes typical of the human placenta. As a consequence, pharmaceutical scientists are in a position to contribute significantly to the design and development of drugs for pregnancy.