Immunochromatography Tests Evaluated for Detection of Novel Norovirus

From September 2014 to March 2015, 70% of all outbreaks in Guangdong and Jiangsu provinces in China were caused by a novel GII.17 virus and a similar increase in the number of infections with this novel GII.17 virus has been reported in Japan and Thailand since December 2014.

Microbiologists at Chiang Mai University (Thailand) working with colleagues from Japan, analyzed randomly selected stool samples for which there was a large quantity available—a panel of six GII.17-positive stool samples from five patients in Japan and one in Thailand in which the virus copy numbers had been quantified by real-time reverse-transcriptase polymerase chain reaction (RT-PC R) for reference values. Two of the six GII.17 stool samples tested positive by four immunochromatography (IC) kits.

To evaluate if these IC tests are able to detect these novel GII.17 noroviruses, they tested four commercial kits available in Japan: GE test Noro Nissui (Nissui Pharmaceutical Co., Ltd.; Tokyo, Japan); ImmunoCatch-Noro (Eiken Chemical Co., Ltd.; Tokyo, Japan); Quick Navi-Noro 2 (Denka Seiken Co., Ltd.; Tokyo, Japan); Quick Chaser-Noro (Mizuho Medy Co., Ltd.; Tosu City, Japan).

The six specimens tested by real-time RT-PCR demonstrated that the two samples that were positive by IC test contained high virus titers of 1.90 × 10⁹ and 8.06 × 10⁹ virus copies/mL. In contrast, the other four specimens that were negative in the IC test had virus titers ranging from 4.91 × 10³ to 2.50 ×10⁸ virus copies/mL. The results demonstrated that at 1:10 dilution of a virus titer equal to 1.90 × 10⁸ copies/mL, two of three tests still showed the positive results, with a weak positive band, while at 1:100 dilution equal to virus titer 1.90 × 10⁷ copies/mL, all three IC tests were negative. These data demonstrated that the sensitivity of the IC kits for the detection of this novel GII.17 virus was about 10⁸ copies/mL.

The authors concluded that the tested commercial IC kits for the detection Norovirus available on the market in Japan were able to detect the novel GII.17 Norovirus, but with relatively low sensitivity. Only samples that contained more than 10⁹ copies/mL were positive in all four IC tests. They suggest a redesign of the currently available Norovirus IC tests may be required to detect the novel GII.17 noroviruses with the same sensitivity as for the more commonly circulating norovirus genotypes. Laboratories and physicians should be aware of these findings, in particular where the novel GII.17 norovirus has been shown to be circulating.

Related Links:
Chiang Mai University
Nissui Pharmaceutical 
Eiken Chemical