Characterisation of a G9P[8] rotavirus strain identified during a gastroenteritis outbreak in Alice Springs, Australia post Rotarix™ vaccine introduction.

A large rotavirus gastroenteritis outbreak occurred in the Alice Springs region of the Northern Territory, Australia from the 12th of March until the 11th of July 2007. The outbreak occurred five months after the introduction of the Rotarix™ vaccine. Electropherotype and sequence analysis demonstrated that a single G9P[8] strain was responsible for the outbreak and that the strain remained highly conserved during the outbreak period. The outbreak strain contained amino acid changes in regions of the VP7 and NSP4 genes, with known biological function, when compared to previously characterised G9P[8] strains from Australia and other international locations. The recent vaccine introduction was unlikely to have influenced genotype selection in this setting. Importantly, Rotarix™ vaccine was highly effective against the G9P[8] outbreak strain.

Maternal antibodies to rotavirus: could they interfere with live rotavirus vaccines in developing countries?

INTRODUCTION: Past experience with live oral vaccines including licensed rotavirus vaccines demonstrates a trend towards reduced vaccine efficacy in developing countries compared with developed countries. The reasons behind this disparity are not well understood. Transplacental transfer of maternal antibodies and breast milk ingestion may attenuate vaccine responses in infants in developing countries where rotavirus infections are endemic, and maternal antibody levels are high. We examined the prevalence and level of rotavirus antibody in maternal and cord serum, colostrum and breast milk in a developing country setting. METHODS: 100 mother-infant pairs were prospectively recruited from December 2008 to February 2009 at Dr. Sardjito Hospital, Yogyakarta, Indonesia. Maternal and cord sera were collected during delivery. Colostrum and transitional breast milk were collected between day 0-3 and day 7-10 postpartum respectively. Rotavirus-specific IgA and IgG were estimated for all specimens and virus neutralization assays were conducted on a subset of milk specimens. RESULTS: All maternal and cord serum samples were positive for rotavirus-specific IgG antibodies with a strong correlation between levels of rotavirus-specific IgG in mothers and levels transferred to infants in cord blood (r=0.86; p=0.001). 78% of colostrum and 67% of transitional breast milk specimens were positive for rotavirus-specific IgA. There was a median 4-fold decrease in rotavirus-specific IgA from colostrum to transitional breast milk. Neutralizing antibodies were present in 56% of colostrum specimens assayed (19/34) and in 41% of transitional milk specimens assayed (14/34). CONCLUSIONS: Maternal serum and breast milk antibodies to rotavirus are highly prevalent in a developing country setting. Evaluation of the impact of maternal anti-rotavirus serum and breast milk antibody upon vaccine immunogenicity would help to inform rotavirus vaccination strategies, especially in developing settings.

Circulating human group A rotavirus genotypes in Malaysia.

This study examined the temporal distribution of rotavirus genotypes in Malaysia. Rotaviruses from children with diarrhea admitted to hospitals in 1996 (n = 93) and 2007 (n = 12) in two different regions of Peninsular (West) Malaysia were analyzed for their G and P genotypes using a hemi-nested RT-PCR assay. In the 2007 samples, the dominant strain was G9P[8]. It was identified in 42% of the samples. Different strains all possessing the G1 genotype were identified in the rest of the samples. In contrast, 81% of the samples collected in 1996 were the G1P[8] strain. No strains with G9 genotype were detected in samples collected in 1996.

Molecular characterization and epidemiology of rotavirus isolates obtained from children with diarrhoea in Malaysia.

This retrospective study examined the G/P type of rotavirus in RNA samples that have previously been e-typed by RNA-PAGE in 1996. The results were then compared to 2007 samples to ascertain the extent of changes that may have occurred in this 11-years time interval. The G and P genotypes were determined by hemi-nested PCR and further analysed by phylogenetic study. In 1996, the G/P combination G1P[8], G(UT)P[8] and G1P(UT) prevalence rate were 81%, 9% and 7%, respectively. As expected, the G9 genotype which has already emerged worldwide was identified in 42% of the 2007 samples with the remaining 33% G1P[8] and 25% G1P(UT) Analysis of the RNA pattern showed that majority of the isolates were long e-type in both series, nevertheless minor differences within electropherotypes were observed. Genetic diversity in some strains of the human group A rotaviruses was analysed by phylogenetic methods. These findings will help in the decision to introduce rotavirus vaccines within the next decade.

Report of the Australian Rotavirus Surveillance Program, 2000/2001.

The National Rotavirus Reference Centre together with 15 collaborating laboratories Australia-wide conducted rotavirus surveillance from June 1999. The serotypes of rotaviruses that are responsible for the hospitalisation of children with acute diarrhoea were determined for the period June 2000 to May 2001. We examined 1108 rotavirus specimens using a combination of monoclonal antibody immunoassay, reverse transcription-PCR, and Northern hybridisation. Serotype G1 strains were the most prevalent overall (49.5%), and found in all centres. Serotype G9 rotaviruses, which were first identified in 1997, were second in importance (18.1%). Serotype G2 viruses were next (12.5%), followed by the re-emergence of serotype G4 viruses (9.7%). The findings of this study have implications for vaccine development strategies where protection against serotypes additional to G1-G4 may be required.

Annual report of the Rotavirus Surveillance Programme, 1999/2000.

The National Rotavirus Reference Centre has conducted rotavirus surveillance by means of a collaborative laboratory based initiative started in June 1999. The serotypes of rotaviruses that lead to the hospitalisation of children with acute diarrhoea were determined from June 1999 to May 2000. We examined 1126 rotavirus specimens using a combination of monoclonal antibody immunoassay, reverse transcription-polymerase chain reaction, and hybridisation. The four most common serotypes G1-G4 were represented. More than 50% of isolates tested were serotype G1, with serotype G1 being represented in most centres Australia-wide. Serotype G9 rotaviruses were identified for the first time in Australia, and were second in importance with 10% of samples tested. The significant presence of G9 viruses throughout Australia suggests the emergence of a new serotype and has implications for current rotavirus vaccine strategies that target serotypes G1-G4.