Vaccine Enhances Effect of HIV Drugs

Boosting immune system improves efficacy of antiretroviral drugs.

Boosting the immune system of a patient infected with HIV may help improve the efficacy of current treatments for the disease.

A study published recently in the open access journal Retrovirology found that a vaccine with a protein needed for viral replication can boost the immune system to improve antiretroviral drug efficacy.

After initial diagnosis, HIV-infected patients are receive highly active antiretroviral therapy (HAART), which almost completely stops the virus from reproducing. With HAART the virus is still able to replicate at low levels and accumulate in viral reservoirs, however, which cannot be treated by HAART and can lead to complications and death from non-AIDS related diseases.

The viral protein called Tat is produced early in HIV infection and plays a vital role in replication and disease progression by weakening the immune system. A vaccine with a small amount of Tat protein lead to an immune response that prevents disease progression.

"We prove for the first time that antiretroviral therapy may be intensified by a vaccine,” lead researcher Barbara Ensoli said in a press release. “These results open new scenarios to investigate, namely whether this vaccine may help with virus control where patients have low adherence to antiretroviral therapy, simplify treatment, and reduce transmission of the disease."

The researchers conducted a phase 2 clinical trial where 168 HIV-infected patients were injected with the vaccine that contained either 7.5 micrograms or 30 micrograms of the Tat protein. With both treatment groups, the patients received the vaccine once a month for either 3 or 5 months.

None of the patients had anti-Tat antibodies at the start of the trial, as researchers hoped the vaccine would induce them while the patients continued with HAART treatment.

The patients were followed for 144 weeks, as the vaccine was found to induce production of anti-Tat antibodies. The results showed significant growth of CD4+ T cells that indicate the strength of the immune system, in addition to an increase in T-cells, B-cells, and other immune cells.

The greatest response was seen in patients who received the vaccine with 30 micrograms of Tat for 3 months, with the effects persisting for all 3 years.

The patients also showed a significant reduction in the HIV proviral DNA load that acts as an indicator of the latent form of the virus in reservoirs. The reduction compared favorably to a cohort of 79 patients who only received HAART in a separate observational study, which acted as reference group for biomarkers of the disease.

The results offer promising signs for future HIV treatment, but the results of future efficacy studies are needed to confirm the findings.