1 Institute of Experimental Pathology and Therapy, USSR Academy of Medical Sciences, Sukhumi, USSR
2 All-Union Oncological Moscow, USSR
3 Institute of Sera and Vaccines, 10103 Prague, Czechoslovakia

A. Introduction

Our previous studies have shown that hamadryas baboons of the Sukhumi "high lymphoma " stock are infected with human T lymphotrophic virus (HTL V)-I-related virus to a significantly higher degree than baboons of different lymphoma-free populations. Levels of anti-HTL V -I-related antibodies in prelymphomatous baboon sera were also significantly higher than those in matched controls [1,2]. These studies posed the question ofwhether HTL V -I-like virus is etiologically related to baboon malignant lymphoma. The most informative indirect approach to the study of this possibility is the search for integrated provirus in baboon lymphoma DNA. Thus, we tested by Southern blotting Pstl, BamHI, and EcoRI digests of high molecular weight baboon lymphoma DNA, using as a probe genome-length HTLV-I cloned in SstI site ofpSP-65 vector (this molecular clone was kindly provided by Dr. R. Gallo). Ten PstI-digested lymphoma DNA samples (lymphomatous lymph nodes) were found positive (Table 1). The band pattern was similar to, but clearly different from, that characteristic f or HTL V -I (cf. Figs. 1, 2, 4). At least three fragments (1.7 kb, 1.5 kb, and 1.1 kb) were observed in all samples (Table 1; Fig. 1 ). They were thought to be internal fragments [3]. In each positive sample "individual" bands were also found that suggest monoclonal ( or oligoclonal) integration of HTL V -I provirus into different sites in baboon lymphoma DNA (Fig.1). This suggestion was proved correct by Southern analysis of BamHI and

Fig.1. Southern analysis of PstI digests of baboon lymphoma DNA. 1-10, sample numbers the same as in Table 1; K,
baboon cell line (594S- F9) producing HTLV-I-like virus; M, Molecular size markers: 23.4,9.4,6.5,4.4,2.3, and 2.0 kb

Table I. HTL V -l-related sequences in DNA of lymphomatous lymph nodes of hamadryas baboons

Fig.2. Southern analysis of BamH1 digests of baboon lymphoma DNA
Fig.3. Southern analysis of EcoR1 digests of baboon lymphoma DNA
Fig.4. Southern analysis of PstI (B) and BarnHI (a) digests of positive-control cellular and plasmid DNA. C91, human cell line (C91-PL) producing HTLV-I

EcoRI digests of the same lymphoma DNA (Table 1; Fig.2, Fig.3). One to three large fragments were observed in each sample, all with individual size. In some cases, fragments were found which were smaller than the expected HTL V -I-like provirus size. These data suggested multiple integration of HTL V -like provirus( es ) in some baboon lymphomas or the oligoclonal origin of these tumors, as well as integration of defective provirus(es) in several cases. HTLV-I-related sequences were not found in one sample of baboon normal lymph node DNA and three samples of muscle DNA isolated from lymphomatous animals.

B. Conclusions

1. HTLV-I-like provirus is integrated into DNA of baboon malignant lymphomas.
2. Baboon HTL V -I-like provirus is closely related to, but distinct from, HTL V -I.
3. In most cases the integration of HTLV-I like provirus is multiple monoclonal, or the origin of these tumors is oligoclonal.
4. Defective HTL V -I-like proviruses are integrated into DNA of some baboon malignant lymphomas.

References

1. Lapin BA, Voevodill AF, lndzhiia LV et al. (1983) Bull Exp BioI Med v. XCV, 14-16 (in Russ)

2. Voevodin AF, Lapin BA, Yakovleva LA et al. (1985) lilt J Cancer 36:579-584

3. Quo H, Wollg-Staal F, Gallo R (1984) Science 223:1195-1196