ISOLATION OF INTERTYPIC RECOMBINANTS OF EPSTEIN-BARR-VIRUS FROM T-CELL-IMMUNOCOMPROMISED INDIVIDUALS

All wild-type isolates of Epstein-Barr virus (EBV) analyzed; to date f or allelic polymorphisms of the nuclear antigen EBNA2 gene (in the Bam HI YH region of the genome) and of the EBNA3A, -3B, -3C genes (tandeml y arranged in the BamHI E region) have proved either uniformly type 1 or uniformly type 2 at all four loci. The absence of detectable intert ypic recombination in the wild probably reflects the rarity with which individual carriers, and certainly individual target cells, become co infected with both virus types. Studying a group of human immunodefici ency virus-positive T-cell-immunocompromised patients known to be at e nhanced risk of multiple EBV infections, we have isolated intertypic E BV recombinants from 2 of 40 patients analyzed. These recombinants, wh ose in vitro transforming capacity appeared at least equal to that of type 1 strains, carried a type 1 EBNA2 allele and type 2 EBNA3A, -3B, and -3C alleles. This was clearly demonstrable at the DNA level by PCR amplification using type-specific primer-probe combinations and was c onfirmed at the protein level (for EBNA2 and EBNA3C) by immunoblotting with type-specific antibodies. In one patient, the recombinant appear ed to be the predominant strain, being the virus most commonly rescued by in vitro transformation both from the blood and from the throat wa shings on two separate occasions 20 months apart. A regular type 1 vir us strain was also present in this individual, but this was not relate d to the recombinant since the two viruses carried type 1 EBNA2 genes with different patterns of variance from the B95.8 prototype sequence. In the other patient, recombinants were isolated on one occasion from the blood and on a separate occasion, 21 months later, from the throa t; these recombinants were almost certainly related, being identical a t several genomic polymorphisms and differing only in one facet of the ''EBNAprint,'' the size of the EBNA1 protein. Three different type 1 viruses were also isolated from this patient, two of which carried EBN A2 genes with the same pattern of sequence variation from B95.8 as the recombinant; however, since this is a fairly common pattern of varian ce, the relationship of these viruses to the recombinant remains an op en question. We infer that intertypic recombinants of EBV are not unco mmon in HIV-positive T-cell-immunocompromised patients, that they aris e in such individuals as a consequence of their increased frequency of mixed-type infections, and that they will prove capable of efficient transmission in the human population.