New gene-enzyme system in Anopheles atroparvus: occurrence and frequencies of four alleles at the EST6 locus

Four isoallelic molecular variants of a protein having esterase activity (Esterase 6) have been detected in adults belonging to our laboratory strain of Anopheles atroparvus. From the random combination of the four alleles coding for Esterase6 (Est6S, Est6I1, Est6I1, Est6F), 10 different phenotypes (genotypes) can be obtained. The observed gene frequencies, found by screening 134 individuals randomly sampled from the strain, have been found in agreement with the expected ones, assuming Hardy-Weinberg equilibrium. The observed amount of segregation present in a locus of a laboratory strain and the operative value that should be given to this kind of formal genetics in mosquitoes is discussed.

Antigenic variation among avian influenza A viruses

A total of 16 strains of influenza A virus isolated in 1965-66 from quail, ducks, turkeys, pheasants and chickens bred in poultry farms situated in Pavia and surrounding districts in northern Italy were investigated from the point of view of antigenic grouping by the complement-fixation test.All strains were antigenically related but not identical to each other. Most but not all strains were antigenically related to virus N and some to Duck/England/62, Turkey/Canada/63 and Turkey/Massachussets/65. There was a suggestion of an antigenic shift away from virus N but replacement of given strains by subsequent variants was not constant.The findings do not support the view that animal influenza viruses do not show antigenic variation comparable to that seen among human strains. There was no correlation between antigenic structure and host range and thus no indication that different hosts are infected preferentially by viruses of a particular antigenic character.