Nick Karabatsos

Antigenic Relationships between Flaviviruses as Determined by Cross-neutralization Tests with Polyclonal Antisera

The recently established virus family Flaviviridae contains at least 68 recognized members. Sixty-six of these viruses were tested by cross-neutralization in cell cultures. Flaviviruses were separated into eight complexes [tick-borne encephalitis (12 viruses), Rio Bravo (six), Japanese encephalitis (10), Tyuleniy (three), Ntaya (five), Uganda S (four), dengue (four) and Modoc (five)] containing 49 viruses; 17 other viruses were not sufficiently related to warrant inclusion in any of these complexes.

Evidence that fatal human infections with La Crosse virus may be associated with a narrow range of genotypes

La Crosse (LAC) virus belongs to the California (CAL) serogroup of the genus Bunyavirus, family Bunyaviridae. It is considered one of the most important mosquito-borne pathogens in North America, especially in the upper Mid-West, where it is associated with encephalitis during the time of year when mosquitoes are active. Infections occur most frequently in children and young adults and, while most cases are resolved after a period of intense illness, a small fraction (< 1%) are fatal. At present there have only been three isolates of LAC virus from humans all made from brain tissue postmortem. The cases yielding viruses are separated chronologically by 33 years and geographically from Minnesota/Wisconsin (1960, 1978) to Missouri (1993). The M RNA sequence of the first two isolates was previously reported. The present study extends the observations to the isolate from the 1993 case and includes several mosquito isolates as well. A comparison of the M RNAs of these viruses shows that for the human isolates both nucleotide sequence and the deduced amino-acid sequence of the encoded proteins are highly conserved, showing a maximum variation of only 0.91% and 0.69%, respectively. This high degree of conservation over time and space leads to the hypothesis that human infections with this particular genotype of LAC virus are those most likely to have a fatal outcome. It is also shown that a virus with this genotype could be found circulating in mosquitoes in an area more or less intermediate between the locations of the first and second fatal cases.

Palma Virus, a New Bunyaviridae Isolated from Ticks in Portugal

An agent pathogenic for laboratory albino Swiss mice was isolated from a pool of Haemaphysalis punctata ticks collected from cattle on a farm located in Alcácer do Sal county, southern Portugal. The isolated virus was shown to be distinct from but serologically related to virus members of the Bhanja antigenic group. This new virus in the family Bunyaviridae was named Palma for the farm where ticks have been collected for several studies.

Koolpinyah: A Virus Related to Kotonkan from Cattle in Northern Australia

Two closely related viruses were isolated from the blood of bovines near Darwin, Northern Territory, Australia. When studies of virus morphology indicated that these were rhabdoviruses, serologic studies were done. These isolates are closely related or identical and are related to, but distinct from, the rabies-related kotonkan virus. Other serologic studies showed that these are two isolates of a newly recognized virus, for which the name Koolpinyah virus is proposed.