Antibodies to HTLV-I have been detected in sera from 15 (2.0%) of 736 adult blood-donors in Nigeria, in 4 (20.0%) of 20 patients with chronic lymphatic leukaemia, 3 (10.0%) of 30 with non-Hodgkin's lymphoma, one of 12 with Burkitt's lymphoma and one of 7 with acute lymphoblastic leukaemia. The frequency of positivity was higher (3.6%) in the blood-donors from the guinea and wooded savanna of northern Nigeria than in those from the rain-forest and mangrove swamps of southern Nigeria (1.8% in Lagos and 0.7% in Calabar). Two of the 3 seropositive patients with lymphoma had clinical presentation and courses similar to those of Japanese and Caribbean patients with adult T-cell leukaemia/lymphoma.

Almost 4000 sera from seven African states were examined for antibodies to ATLV/HTLV-1. Between 1% and 8% of healthy people from sub-Saharan Africa have such antibodies. The highest frequency was observed in Gabon. There were considerable variations between villages. The percentage of seropositives and the mean titre increased with age. Our findings suggest that the African continent is the largest endemic area for ATLV.

Using terminal position, hydrophilicity, predicted reverse turns and type specificity as criteria, five oligopeptides were selected for synthesis from the amino acid sequence of the envelope glycopolypeptide gp70 of Friend murine leukaemia virus. These peptides corresponded to the amino acids 6‐12 (pep1), 124‐131 (pep2), 256‐262 (pep3), 283‐290 (pep4) and 434‐441 (pep5). After coupling to carriers, bovine serum albumin or keyhole limpet hemocyanin, antisera were prepared in rabbits. All of the five oligopeptides were immunogenic and pep1, pep2, pep4 and pep5 were able to elicit antibodies to the native glycopolypeptide. These sequence‐specific antisera distinguished between glycoproteins of different leukaemia viruses. At least three of the selected peptides, the type‐specific oligopeptides pep3, pep4 and pep5, were found to be natural epitopes of gp70.

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The efficiency was examined of immunization with feline leukemia virus glycoprotein complexes (gp85 rosettes) to protect cats against tumors induced by feline sarcoma virus (FeSV). The glycoprotein was isolated from feline leukemia virus (FeLV). Young cats were vaccinated with the purified viral glycoprotein and challenged with FeSV (FeLV). FeLV gp85 antibody levels were measured by enzyme-linked immunosorbent assay and tumor volumes were determined. In immunized animals tumor development was reduced. Gp85 antibody levels before challenge were correlated inversely with tumor size (r2 = 0.79). This method appears to be suitable for fast and efficient testing of future FeLV vaccines.