Johns Hopkins scientists have found that a safe and inexpensive antibiotic¹（抗体） in use since the 1970s for treating acne（痤疮，粉刺） effectively targets infected immune cells in which HIV, the virus that causes AIDS, lies dormant²（静止的，休眠的） and prevents them from reactivating and replicating³（复制，折叠） . The drug, minocycline（二甲胺四环素） , likely will improve on the current treatment regimens（养生法，生活规则） of HIV-infected patients if used in combination with（与……结合） a standard drug cocktail⁴ known as HAART (Highly Active Antiretroviral Therapy高效抗逆转录病毒治疗), according to research published now online and appearing in print April 15 in The Journal of Infectious Diseases. "The powerful advantage to using minocycline is that the virus appears less able to develop drug resistance because minocycline targets cellular⁵ pathways not viral proteins," says Janice Clements, Ph.D., Mary Wallace Stanton Professor of Faculty⁷ Affairs, vice⁸ dean for faculty（能力，科，系）, and professor of molecular⁹ and comparative pathobiology（病理学） at the Johns Hopkins University School of Medicine.

"The big challenge clinicians deal with now in this country when treating HIV patients is keeping the virus locked in a dormant state," Clements adds. "While HAART is really effective in keeping down active replication, minocycline is another arm of defense¹⁰ against the virus."

Unlike the drugs used in HAART which target the virus, minocycline homes in on, and adjusts T cells, major immune system agents and targets of HIV infection. According to Clements, minocycline reduces the ability of T cells to activate¹¹ and proliferate¹²（增殖，扩散） , both steps crucial to HIV production and progression toward full blown AIDS.

If taken daily for life, HAART usually can protect people from becoming ill, but it's not a cure. The HIV virus is kept at a low level but isn't ever entirely¹³ purged¹⁴; it stays quietly hidden in some immune cells. If a person stops HAART or misses a dose, the virus can reactivate out of those immune cells and begin to spread.

The idea for using minocycline as an adjunct（修饰语，附属物） to HAART resulted when the Hopkins team learned of research by others on rheumatoid arthritis¹⁵（风湿性关节炎） patients showing the anti-inflammatory effects of minocycline on T cells. The Hopkins group connected the dots between that study with previous research of their own showing that minocycline treatment had multiple beneficial effects in monkeys infected with SIV（猿猴免疫缺损病毒） , the primate¹⁶ version of HIV. In monkeys treated with minocycline, the virus load in the cerebrospinal fluid（脑脊髓液） , the viral RNA in the brain and the severity of central nervous system disease were significantly decreased. The drug was also shown to affect T cell activation¹⁷ and proliferation.

"Since minocycline reduced T cell activation, you might think it would have impaired¹⁸ the immune systems in the macaques（猕猴，恒河猴） , which are very similar to humans, but we didn't see any deleterious effect（有毒影响） ," says Gregory Szeto, a graduate student in the Department of Cellular and Molecular Medicine working in the Retrovirus Laboratory at Hopkins.

"This drug strikes a good balance and is ideal for HIV because it targets very specific aspects of immune activation."

The success with the animal model prompted the team to study in test tubes whether minocycline treatment affected¹⁹ latency in human T cells infected with HIV. Using cells from HIV-infected humans on HAART, the team isolated²⁰ the "resting" immune cells and treated half of them with minocycline. Then they counted how many virus particles were reactivated, finding completely undetectable levels in the treated cells versus²² detectable²¹ levels in the untreated cells.

"Minocycline reduces the capability²³ of the virus to emerge from resting infected T cells," Szeto explains. "It prevents the virus from escaping in the one in a million cells in which it lays dormant in a person on HAART, and since it prevents virus activation it should maintain the level of viral latency（潜伏，潜在影响） or even lower it. That's the goal: Sustaining a latent non-infectious state."

The team used molecular markers to discover that minocycline very selectively interrupts certain specific signaling pathways critical for T cell activation. However, the antibiotic doesn't completely obliterate²⁴（消灭，冲刷） T cells or diminish their ability to respond to other infections or diseases, which is crucial for individuals with HIV.

"HIV requires T cell activation for efficient replication and reactivation of latent virus," Clement⁶ says, "so our new understanding about minocyline's effects on a T cell could help us to find even more drugs that target its signaling pathways."