Characterization of antigenically unique influenza C virus strains isolated in Yamagata and Sendai Cities, Japan, during 1992–1993

Antigenic and Genetic Characterization of Influenza C Viruses Which Caused Two Outbreaks in Yamagata City, Japan, in 1996 and 1998

“…As shown in Table 1, the reactivity patterns of the 1996 and 1998 isolates were similar; all the viruses were highly reactive with MAbs J14 and Q5 but were unreactive or very weakly reactive with U4 and MS22. Comparison of this reactivity pattern with those of four reference strains (which represent each of the four virus groups shown to have circulated in Japan in the 1980s and the early 1990s [17]) revealed that all 33 isolates obtained from Yamagata City in 1996 and 1998 belonged to the YA2681 virus group.…”

“…In order to confirm the results of the antigenic analysis, which suggested that all the 1996 and 1998 isolates from Yamagata City have HE genes belonging to the YA2681-related lineage, the sequence of the HE gene (nucleotides 64 to 1989) was determined for 7 ( 33 isolates, and a phylogenetic tree was constructed by using these 7 sequences in addition to the 42 published sequences (1,3,4,13,15,16,17,20,21,25,26,27,28,33) as well as the 12 sequences of the 1993 to 1996 isolates from Sendai City determined here (see below for details). …”

“…Thus, reassortment characterized by exchange of genome segments between two different influenza C virus strains occurs not only in vitro (24) but also in nature (2,17,27,32). However, the epidemiological significance of genetic reassortment in influenza C viruses is unknown.…”

“…We compared the antigenic specificity of the HE glycoprotein as well as the HE gene sequence among 42 strains isolated between 1947 and 1993 (which included 13 strains obtained by our surveillance work) and revealed the existence of six distinct virus groups, represented by strains Taylor/47, Kanagawa/1/76 (KA176), Yamagata/26/81 (YA2681), Aichi/1/81 (AI181), Sao Paulo/378/82 (SP82), and Mississippi/80 (MS80), four of which (YA2681-, AI181-, SP82-, and MS80-related lineages) circulated in Japan in the 1980s and the early 1990s (17).…”

Isolation of an Influenza C Virus Introduced into Japan by a Traveler from Malaysia

“…The genome of influenza C virus consists of seven RNA segments, that is, PB2, PB1, P3, HE, NP, M, and NS gene segments (reviewed in reference 6). Phylogenetic analysis of the HE gene segment, which encodes a surface glycoprotein, showed that the five (10) and that two or three of these lineages cocirculated in a single community (5, 9, 13). Thus, mixed infection with influenza C virus belonging to different lineages is likely to occur in humans, resulting in the emergence of reassortant virus characterized by exchange of genome segments between two different strains (11,16).…”