Stability studies of HIV-1 Pr55gagvirus-like particles made in insect cells after storage in various formulation media

Alisson Lynch,Anna-Lise Williamson,Edward P Rybicki,Ann E Meyers

doi:10.1186/1743-422x-9-210

Abstract

BackgroundHIV-1 Pr55gag virus-like particles (VLPs) expressed by baculovirus in insect cells are considered to be a very promising HIV-1 vaccine candidate, as they have been shown to elicit broad cellular immune responses when tested in animals, particularly when used as a boost to DNA or BCG vaccines. However, it is important for the VLPs to retain their structure for them to be fully functional and effective. The medium in which the VLPs are formulated and the temperature at which they are stored are two important factors affecting their stability.FindingsWe describe the screening of 3 different readily available formulation media (sorbitol, sucrose and trehalose) for their ability to stabilise HIV-1 Pr55gag VLPs during prolonged storage. Transmission electron microscopy (TEM) was done on VLPs stored at two different concentrations of the media at three different temperatures (4°C, –20°C and −70°C) over different time periods, and the appearance of the VLPs was compared. VLPs stored in 15% trehalose at −70°C retained their original appearance the most effectively over a period of 12 months. VLPs stored in 5% trehalose, sorbitol or sucrose were not all intact even after 1 month storage at the temperatures tested. In addition, we showed that VLPs stored under these conditions were able to be frozen and re-thawed twice before showing changes in their appearance.ConclusionsAlthough the inclusion of other analytical tools are essential to validate these preliminary findings, storage in 15% trehalose at −70°C for 12 months is most effective in retaining VLP stability.

Highlights

HIV-1 Pr55gag virus-like particles (VLPs) expressed by baculovirus in insect cells are considered to be a very promising HIV-1 vaccine candidate, as they have been shown to elicit broad cellular immune responses when tested in animals, when used as a boost to DNA or BCG vaccines
Conclusions: the inclusion of other analytical tools are essential to validate these preliminary findings, storage in 15% trehalose at −70°C for 12 months is most effective in retaining VLP stability
HIV-1 Gag polyprotein (Pr55gag) forms non-infectious VLPs that are morphologically similar to HIV-1 particles when expressed in isolation in insect cells [8]

Summary

Introduction

HIV-1 Pr55gag virus-like particles (VLPs) expressed by baculovirus in insect cells are considered to be a very promising HIV-1 vaccine candidate, as they have been shown to elicit broad cellular immune responses when tested in animals, when used as a boost to DNA or BCG vaccines. HIV-1 Gag polyprotein (Pr55gag) forms non-infectious VLPs that are morphologically similar to HIV-1 particles when expressed in isolation in insect cells [8]. * Correspondence: Ann.meyers@uct.ac.za 1Department of Molecular and Cell Biology, Faculty of Science, University of Cape Town, University Ave, Rondebosch 7701, South Africa Full list of author information is available at the end of the article previously shown that these VLPs significantly boost immune responses to a matched subtype C gag DNA inoculation in mice [9], as well as in baboons [10].

Results

Conclusion