Penemuan Vaksin HIV Masih Jauh

LONDON -- Setelah lebih dari duapuluh tahun meneliti, para ilmuwan ternyata tidak semakin dekat untuk menemukan vaksin HIV. ''Ini tantangan besar, sebab untuk mengendalikan HIV dengan imunologi. Komunitas ilmiah harus mengalahkan alam, menghadapi alam, dengan keunggulan empat miliar tahun evolusi. Hal itu ternyata belum bisa dilakukan,'' ujar pakar biologi peraih Hadiah Nobel, Profesor David Baltimore, seperti dilansir BBC.

Baltimore yang juga Presiden Perhimpunan Amerika untuk Kemajuan Sains (AAAS) mengaku kekurangberhasilan tersebut mungkin bisa dipahami. ''Tapi, tidak bisa diterima,'' jelasnya . Saat berbicara dalam pertemuan tahunan AAAS di Boston, Baltimore, ia mengatakan bahwa HIV telah mengembangkan cara untuk melindungi diri dari sistem kekebalan manusia. ''Jadi, kita harus bertindak selangkah lebih jauh daripada alam,'' kilahnya.

Dia mengungkapkan, upaya untuk mengendalikan virus melalui antibodi atau dengan meningkatkan sistem kekebalan tubuh manusia berakhir tanpa hasil. Baltimore juga mengaku kecewa dengan kalangan ilmuwan pengembang vaksin. eye

http://republika.co.id/koran_detail.asp?id=324241&kat_id=359

Gene Therapy for Chronic Pain

By Jocelyn Rice

A new kind of gene therapy could bring relief to patients suffering from chronic pain while bypassing many of the debilitating side effects associated with traditional painkillers.

Researchers at Mount Sinai School of Medicine injected a virus carrying the gene for an endogenous opioid--a chemical naturally produced by the body that has the same effect as opiate painkillers such as morphine--directly into the spinal fluid of rats. The injections were targeted to regions of the spinal cord called the dorsal root ganglia, which act as a "pain gate" by intercepting pain signals from the body on their way to the brain. "You can stop pain transmission at the spinal level so that pain impulses never reach the brain," says project leader Andreas Beutler, an assistant professor of hematology and medical oncology at Mount Sinai.

The injection technique is equivalent to a spinal tap, a routine procedure that can be performed quickly at a patient's bedside without general anesthesia.

Because it targets the spinal cord directly, this technique limits the opiate-like substance, and hence any side effects, to a contained area. Normally, when opiate drugs are administered orally or by injection, their effects are spread throughout the body and brain, where they cause unwanted side effects such as constipation, nausea, sedation, and decreased mental acuity.

Side effects are a major hurdle in treating chronic pain, which costs the United States around $100 billion annually in treatment and lost wages. While opiate drugs can be very effective, the doses required to successfully control pain are often too high for the patient to tolerate.

"The side effects can be as bad as the pain," says Doris Cope, director of the University of Pittsburgh Medical Center's Pain Medicine Program. Achieving the benefits of opiate treatment without their accompanying side effects, Cope says, would be a "huge step forward."

Beutler hopes to do just that. "Our strategy was to harness the strength of opioids but target it to the pain gate, and thereby create pain relief without the side effects that you always get when you have systemic distribution of opioids," he says.

Several groups have previously attempted to administer gene therapy for pain through spinal injections, but they failed to achieve powerful, long-lasting pain relief. The new technique produced results that lasted as long as three months from a single injection, and unpublished follow-up studies suggest that the effect could persist for a year or more.

Beutler credits his team's success to the development of an improved virus for delivering the gene. The team uses a specially adapted version of adeno-associated virus, or AAV--a tiny virus whose genome is an unpaired strand of DNA. All the virus's own genes are removed, and the human endogenous opioid gene is inserted in their place. Beutler's team also mixed and matched components from various naturally occurring AAV strains and modified the genome into a double-stranded form. These tweaks likely allow the virus to infect nerve cells more easily and stick around longer.

Once the virus is injected into the spinal fluid and makes its way into the nerve cells of the pain gate, it uses the host cells' machinery to churn out the opioid protein--which then goes to work blocking pain signals on their way to the brain. Normally, the gene is rarely activated. But the version used for therapy has no such limitations because the gene carried by the AAV has been modified to continuously produce the opioid chemical.

Cope says that using endogenous opioids is inherently superior to injecting synthetic opiate drugs directly into the spinal fluid, an approach that requires the installation of a pump in order to deliver the drugs over a long time period. "It's kind of a holy grail," she says. "If the body's own system for pain control were activated by genetic expression, that would be superior to an artificial medication."

In Beutler's study, which was published this week in PNAS, rats were surgically modified to have a stronger than usual response to pressure on their paws, mimicking the effects of so-called neuropathic pain. The gene-therapy treatment effectively restored the rats to a normal level of pain sensitivity. The team also tested a nonopioid gene, which produced comparable pain relief through an entirely different mechanism. But while the opioid gene's effects will likely extend to humans, who respond to opiates the same way rats do, the nonopioid's effects may be rat specific.

The Stockholm-based company Diamyd Medical has been developing a different approach to gene therapy for chronic pain that also bypasses the side effects of standard pain treatment. The approach uses a deactivated version of herpes simplex virus (HSV). HSV can be administered straight through the skin as it naturally finds and infects peripheral nerves and travels to the spinal cord on its own. Darren Wolfe of Diamyd says that this method is superior to spinal injection because it's safer and easier, and it can be administered repeatedly.

Because of these considerations, the HSV method may be preferable for treating localized pain. However, when chronic pain involves multiple areas of the body--as it often does with, for example, metastasized cancers--going straight to the pain gate could work more efficiently.

While both of these methods have proved effective in animal models of pain, their efficacy in human patients remains to be shown. Diamyd recently applied to the FDA to begin phase I clinical trials, and Beutler estimates that his approach could be tested on humans in as few as three years.

From here

Virus TUMV Sudah Menyebar di Indonesia

Jakarta (ANTARA News) - Penelitian Institut Pertanian Bogor (IPB) menemukan bahwa virus Turnip Mosaic (TUMV) yang menyerang tananam sawi dan oleh Departemen Pertanian dinyatakan belum ada di Indonesia, ternyata sudah menyebar di sejumlah wilayah di dalam negeri.

Pakar virus tanaman dari Departemen Proteksi Tanaman Fakultas Pertanian IPB, Sri Hendrastuti Hidayat PhD, pada Senin mengatakan, berdasarkan Kepmentan No.38 tahun 2006, TUMV digolongkan dalam organisme pengganggu tanaman karantina (OPTK) golongan A1 yang berarti belum pernah dilaporkan keberadaannya di Indonesia.

"Namun dari hasil survey yang kami lakukan, inveksi virus Turnip Mosaic terjadi di beberapa daerah pertanian sayuran di Indonesia," katanya.

Virus tersebut ditemukan pada tanaman ciaisim dan pakchoi, sejenis tanaman sawi di beberapa wilayah seperti di Lampung, Bengkulu, Pontianak, Balikpapan, Samarinda, Poso dan Donggala dengan persentase infeksi hingga 83 persen.

Sebelumnya, virus yang mengakibatkan kerusakan daun dan mengganggu pertumbuhan tanaman tersebut juga ditemukan telah menyebar di wilayah Jawa Barat, Jawa Tengah, Jawa Timur dan Bali pada sekitar 2004.

Oleh karena itu, tambahnya, Departemen Pertanian seharusnya melakukan revisi terhadap Kepmentan no 38/2006 dan tidak lagi memasukkan TuMV dalam OPTK golongan A1 namun diturunkan menjadi A2 atau dikeluarkan dari daftar OPTK karena sudah ditemukan menyebar di hampir seluruh wilayah Indonesia.

Sementara itu Wakil Sekjen Asosiasi Perbenihan Indonesia (Asbenindo), Afrizal Gindow menyatakan, kebijakan Deptan yang memasukkan virus Turnip Mosaic dalam golongan OPTK A1 berdampak pada terhentinya impor benih caisim, sejenis sawi, sejak 2006.

"Proses pemasukan benih golongan kubis-kubisan (Brasica) dari luar negeri untuk kebutuhan benih di Indonesia saat ini menemui kendala terkait status OPTK TUMV," katanya.

Selama ini untuk kebutuhan benih sawi jenis caisim di dalam negeri yang mencapai 100 ton per tahun masih mengandalkan impor karena komoditas tersebut tidak bisa diproduksi di Indonesia yang beriklim tropis.

Afrizal yang juga Direktur Penjualan dan Pemasaran PT East West Seed Indonesia itu mengatakan, terhentinya impor benih sawi tidak hanya merugikan produsen namun juga berdampak pada petani.

Jika setiap hektar pertanaman sawi caisim memerlukan benih sekitar 0,5 kilogram, lanjutnya, maka sedikitnya 200 ribu pembudidaya tanaman tersebut tidak bisa lagi mengembangkan usahanya kalau setiap petani mengusahakan 1 hektar.

"Dengan dikeluarkannya virus TUMV dari golongan OPTK A1 pemasukan benih sawi dari luar tidak lagi terkendala," katanya sembari menambahkan pasar benih sawi di Indonesia mencapai Rp30 miliar per tahun.

Menurut dia, impor benih golongan kubis-kubisan termasuk sawi caisim dari Jepang, China dan Selandia Baru yang merupakan negara produsen benih tanaman tersebut.

Namun semenjak ditemukan serangan TUMV setelah negara-negara tersebut dinyatakan tidak aman oleh Deptan maka impor hanya bisa dilakukan dari negara bagian Idaho Amerika Serikat.

Afrizal menyatakan, jika impor hanya dari AS tidak akan mampu memenuhi kebutuhan dalam negeri karena produksi di negara tersebut juga terbatas.(*)

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