Evaluation of the thermal stability of live-attenuated Rubella vaccine (Takahashi strain) formulated and lyophilized in different stabilizers.

Live attenuated viral vaccines are difficult to handle and often sensitive to temperature. The viral titer may drop during the processing and storing stage, especially at high temperatures. Using live attenuated viral vaccines successfully depends on keeping the sufficient potency required for an immune response. Although freeze-drying makes the vaccine more stable, in the absence of appropriate stabilizer the process may affect the structure and viability of the viruses. Therefore, the formulation of vaccine by means of an appropriate stabilizer plays a crucial role in the stability of viral structure and potency of the vaccine. This study aimed to evaluate the effect of two new stabilizers, including a Trehalose-based stabilizer (T) and a stabilizer containing sucrose, human serum albumin and sorbitol (S) on the thermal stability of lyophilized live-attenuated Rubella virus (Takahashi strain). Two Rubella vaccines were formulated using different stabilizers and were lyophilized. The potency of produced vaccines was investigated using accelerated stability test. To determine the pattern of thermal stability of reconstituted vaccines in 24 h, incubating at three different temperatures and continuous sampling was also included in this study. The viral titer was calculated by TCID50 method. The regression analysis revealed that T vaccine found the sufficient stability compared to commercial Rubella vaccine containing a gelatin-based (G) stabilizer.

Phenotypic and genomic analysis of serotype 3 Sabin poliovirus vaccine produced in MRC-5 cell substrate.

The cell substrate has a pivotal role in live virus vaccines production. It is necessary to evaluate the effects of the cell substrate on the properties of the propagated viruses, especially in the case of viruses which are unstable genetically such as polioviruses, by monitoring the molecular and phenotypical characteristics of harvested viruses. To investigate the presence/absence of mutation(s), the near full-length genomic sequence of different harvests of the type 3 Sabin strain of poliovirus propagated in MRC-5 cells were determined. The sequences were compared with genomic sequences of different virus seeds, vaccines, and OPV-like isolates. Nearly complete genomic sequencing results, however, revealed no detectable mutations throughout the genome RNA-plaque purified (RSO)-derived monopool of type 3 OPVs manufactured in MRC-5. Thirty-six years of experience in OPV production, trend analysis, and vaccine surveillance also suggest that: (i) different monopools of serotype 3 OPV produced in MRC-5 retained their phenotypic characteristics (temperature sensitivity and neuroattenuation), (ii) MRC-5 cells support the production of acceptable virus yields, (iii) OPV replicated in the MRC-5 cell substrate is a highly efficient and safe vaccine. These results confirm previous reports that MRC-5 is a desirable cell substrate for the production of OPV.

Genetic characterization of RS-12 (S-12), an Iranian isolate of mumps virus, by sequence analysis and comparative genomics of F, SH, and HN genes.

RS-12 mumps virus strain was isolated in 1986, in monkey kidney cells, from the throat-washing of an Iranian patient and developed to RS-12 vaccine by serial passage of the pathogen in MRC-5 cells. During the present study, an early passage RS-12 containing its virulent pathogenic phenotype, was characterized genetically. Its F, SH and HN genes were isolated by RT-PCR amplification and sequenced. It is quite evident that RS-12 belongs to genotype H, closely related to European strains but distinguishable from Asian strains. The deduced amino acid sequences of HN and F proteins that comprise immunogenic epitopes, were compared to other vaccine and wild strains. The multiple sequence alignment revealed that the RS-12 has isoleucine and aspartic acid at positions 269 and 523 of its F and HN proteins, respectively, which could differentiate RS-12 from other available sequences. This isolate has trivial variations in the major antigenic sites of HN protein. The frequency and pattern of F and HN glycosylation sites seems to be similar to most other strains. It seems that the mumps regional outbreak during 1986 in Iran was caused by genotype H and this strain has been spreading in countries surrounding the Caspian sea for over 17 years. These data support the previous results that RS-12 could be an efficient vaccine, especially in the Middle East. This is the first genotype report from Iranian isolates and provides strong data on the molecular epidemiology of mumps in Iran, the Middle East, Central Asia, Russia and other countries of this region.