Differential and defective transcription of koala retrovirus indicates the complexity of host and virus evolution

Koala retrovirus (KoRV) is unique amongst endogenous (inherited) retroviruses in that its incorporation to the host genome is still active, providing an opportunity to study what drives this fundamental process in vertebrate genome evolution. Animals in the southern part of the natural range of koalas were previously thought to be either virus-free or to have only exogenous variants of KoRV with low rates of KoRV-induced disease. In contrast, animals in the northern part of their range universally have both endogenous and exogenous KoRV with very high rates of KoRV-induced disease such as lymphoma. In this study we use a combination of sequencing technologies, Illumina RNA sequencing of 'southern' (south Australian) and 'northern' (SE QLD) koalas and CRISPR enrichment and nanopore sequencing of DNA of 'southern' (South Australian and Victorian animals) to retrieve full-length loci and intregration sites of KoRV variants. We demonstrate that koalas that tested negative to the KoRV pol gene qPCR, used to detect replication-competent KoRV, are not in fact KoRV-free but harbour defective, presumably endogenous, 'RecKoRV' variants that are not fixed between animals. This indicates that these populations have historically been exposed to KoRV and raises questions as to whether these variants have arisen by chance or whether they provide a protective effect from the infectious forms of KoRV. This latter explanation would offer the intriguing prospect of being able to monitor and selectively breed for disease resistance to protect the wild koala population from KoRV-induced disease.

Interleukin-2 plus chemotherapy for patients with metastatic melanoma

We studied the activity of recombinant interleukin-2 (IL2) in combination with multiagent chemotherapy in the treatment of patients with disseminated malignant melanoma. Patients were randomized to receive the same dose of lymphokine by constant 24 h intravenous infusion (CI) or by subcutaneous bolus (SB) injection. Twenty-two patients, 18 males and four females with a median age of 44 years (range 32-73 years) were randomized to receive IL2 5 million units/m2 once daily by SB injection or by CI, 5 days/week for 2 weeks. All patients received a chemotherapy regimen consisting of lomustine (CCNU) 75 mg/m2 on day 14, bleomycin 10 units/day by CI for 5 days (days 14-19) and cisplatin 75 mg/m2 on day 19. Patients were retreated after a 3 week interval. There were four complete responses and one partial response in the CI arm and two partial responses in the SB arm. The median duration of response was 38 weeks (range 26-107 weeks). The median duration of survival was 6.7 months in non-responders and 11.1 months in responders. The overall response rate was 32%. Since responses were brief and all the responding patients progressed after a median of 38 weeks, the study was terminated before accrual goals were met.

Immunotherapy with IL2 by constant infusion and weekly doxorubicin

Twelve women and 7 men, median age 58 (range 17-74), with a diagnosis of non-small-cell lung cancer (11 patients), inflammatory breast cancer (5 patients), osteosarcoma (2 patients), and colon carcinoma (1 patient) were studied. Treatment consisted of four consecutive 6-day courses of infusional interleukin-2 (IL2); 9 patients were treated with 20 X 10(6) IU/m2/day and 10 patients received weekly dose increments of 50% until the maximally tolerated dose was reached. One day after each course was completed patients received doxorubicin, 30 mg/m2; infusional IL2 was resumed 24 h after receiving doxorubicin. Rebounds of lymphocytes with high spontaneous synthetic rates of DNA occurred one day after stopping the infusion, despite doxorubicin administration. The kinetics were not different from earlier trials using IL2 alone. Sequential lymphocyte analysis showed that helper (CD4) and suppressor (CD8) T-cell subsets increased after the first week of treatment and declined thereafter, whereas the proliferation of natural killer (NK) cells (CD16) progressed through the 4-week treatment unaffected by doxorubicin. Mean cytolytic ability induced by IL2 against NK-resistant tumors in vitro was higher in patients who had evidence of clinical tumor regression and therefore is prognostically valuable (p = .02). Three patients left the study prematurely. Five partial remissions and 2 minimal responses were seen in the remaining 16 patients, but they were short-lived. Of the responding patients, only one had failed prior doxorubicin-containing chemotherapy. Toxicities attributable to IL2 and doxorubicin were encountered, and were manageable at these doses. Our data suggest that doxorubicin did not have cytotoxic or suppressive effects on lymphokine-induced lymphocyte functions and that both treatment modalities in combination are worthy of further investigation since they exert distinct and compatible cytotoxic mechanisms and induced tumor regressions with acceptable toxicity in a group of patients with poorly responsive cancers.