SUMMARYTwo monoclonal antibodies raised against Sindbis virus were shown to be specific for the envelope glycoprotein E1 by radioimmunoprecipitation (RIP). They had a number of contrasting biological properties. One of them was capable of neutralizing virus infectivity and inhibiting haemagglutination, while the other had no significant neutralizing or haemagglutination-inhibiting capability, but did inhibit virus-mediated haemolysis. Both monoclonal antibodies could enhance virus infectivity of Fc receptor-bearing macrophage-like cells when present at suitable dilutions.

Two plaque variants of Chikungunya (CHIK) virus were serologically compared with O'nyong nyong (ONN) virus in order to elucidate the reported one way antigenic relationships between the two viruses. Three different hypotheses are examined and evidence is shown to support one of them. Comparison of some biological properties of the viruses showed ONN to be distinct in some respects. All viruses and variants were found to replicate in Anopheles gambiae cells.

In a study conducted on the Kano Plain, Kenya, virus isolation attempts were made on ixodid ticks collected, over a 14-month period, from livestock held in family enclosures (bomas) before releasing the animals for daily foraging. 8735 Amblyomma variegatum (Fabricius) were tested, 98.6% of which were taken from cattle, yielding 36 strains of Dugbe (DUG), four strains of Nairobi sheep disease (NSD), three strains of Bhanja (BHA), one strain of Thogoto (THO) and five strains of virus which could not be characterized. 6549 Rhipicephalus spp. ticks were collected (60.3% from cattle). NSD, DUG and BHA viruses were each isolated twice from ticks taken from cattle. One BHA virus strain was recovered from ticks from a sheep. One strain recovered from ticks on cattle could not be characterized.