Hyperimmune antisera against four Japanese encephalitis (JE) virus strains, ThCMAr4492 and ThCMAr6793 from Thailand and Nakayama and JaGAr01 from Japan, were used to analyze the antigenic relationships among 12 Thai strains belonging to genotype 1, and two Japanese strains and one Chinese strain belonging to genotype 3. The antiserum for ThCMAr6793 significantly neutralized nine of the 12 Thai strains, none of which was significantly neutralized by antisera for the Nakayama and JaGAr01 strains. The antiserum for ThCMAr4492 neutralized only its homologous strain; therefore, ThCMAr4492 was antigenically different from all other strains. Two Thai strains (Subin and KE-093/83) were significantly less neutralized by all four of the antisera tested. In the deduced amino-acid sequence of the E protein, the 12 Thai strains revealed 100 to 98.2 % identity among them and 90.0 to 98.8 % identity with the published strains, respectively. Among significant amino-acid substitutions, three residues at positions E-222, E-327 and E-366 were shared by all of the Thai strains, whereas residues at E-89, E-123, E-131, E-178, E-293, E-351 and E-373 seemed to be strain-specific. The amino acids at positions E-178, E-327, E-351, E-373 and E-366 are found either in the peptides with functional T-helper cell epitopes or in the ectodomain of the E protein of other flaviviruses. These amino acids may therefore be responsible for determining the antigenic heterogeneity of these strains.

Two strains of Japanese encephalitis (JE) virus were isolated from a pool of Culex tritaeniorhynchus captured in 1992 and another pool of Cx. vishnui captured in 1993, in Chiang Mai Area, Northern Thailand. These two strains, ThCMAr44/92 and ThCMAr67/93, could not be identified either as Nakayama or JaGAr01 subtype by the hemagglutination-inhibition (HI) and the neutralization (N) tests using immune sera raised against these standard JE virus strains. Reverse transcription-polymerase chain reaction showed the presence of JE-specific conserved sequences in these strains. Sequencing of 240 nucleotides in their PrM gene region identified that these two strains belong to the genotype 1 of JE virus. Nucleotide and encoded amino acid sequences of their envelope glycoprotein gene revealed 98.8 and 99.8% identity, respectively. These two strains shared 77.8 to 87.7% homology in the nucleotide sequence and 90.0 to 98.8% homology in the amino acid sequence with other reported JE strains. Five strain-specific amino acid changes were noted in ThCMAr44/92 strain, while one in ThCMAr67/93. In addition, four common amino acid changes were found in both strains. Thus, the findings indicated that these two strains were structurally different from each other as well as different from all the reported strains which was in agreement with the serological tests by hemagglutination-inhibition and neutralization.

Here we have identified and characterized a devastating virus capable of inducing yellow mosaic on the leaves of Patchouli [Pogostemon cablin (Blanco) Benth]. The diagnostic tools used were host range, transmission studies, cytopathology, electron microscopy, serology and partial coat protein (CP) gene sequencing. Evidence from biological, serological and sequence data suggested that the causal virus belonged to genus Potyvirus, family Potyviridae. The isolate, designated as Patchouli Yellow Mosaic Virus (PaYMV), was transmitted through grafting, sap and the insect Myzus persicae (Sulz.). Flexuous rod shaped particles with a mean length of 800 nm were consistently observed in leaf-dip preparations from natural as well as alternate hosts, and in purified preparation. Cytoplasmic cylindrical inclusions, pinwheels and laminar aggregates were observed in ultra-thin sections of infected patchouli leaves. The purified capsid protein has a relative mass of 43 kDa. Polyclonal antibodies were raised in rabbits against the coat protein separated on SDS – PAGE; which were used in ELISA and western blotting. Using specific antibodies in ELISA, PaYMV was frequently detected at patchouli plantations at Lucknow and Bengaluru. Potyvirus-specific degenerate primer pair (U335 and D335) had consistently amplified partial CP gene from crude preparations of infected tissues by reverse transcription polymerase chain reaction (RT-PCR). Comparison of the PCR product sequence (290 bp) with the corresponding regions of established potyviruses showed 78–82% and 91–95% sequence similarity at the nucleotide and amino acid levels, respectively. The results clearly established that the virus under study has close homology with watermelon mosaic virus (WMV) in the coat protein region and therefore could share a common ancestor family. Further studies are required to authenticate the identity of PaYMV as a distinct virus or as an isolate of WMV.

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During an epidemiological study of human rotavirus infections in Bangladesh, three group A strains hybridized with a serotype 2 oligonucleotide probe, but they had long RNA electropherotypes. The three strains were collected from 8to 20-month-old infants with acute diarrhea and moderate malnutrition. By a modified isolation procedure, two strains (T-B and T-C) were adapted in MA104 cell cultures. They were identified to be subgroup II specific by enzyme-linked immunosorbent assay with subgroup I-and II-specific monoclonal antibodies and were identified by a fluorescent focus reduction neutralization assay with hyperimmune antisera to be serotype 2 specific. Further characterization of these unusual rotavirus strains needs to be carried out.