A major obstacle in human immunodeficiency virus type 1 (HIV-1) eradication is the ability of the virus to remain latent in a subpopulation of the cells it infects. Latently infected cells can escape the viral immune response and persist for long periods of time, despite the presence of successful highly active antiretroviral therapy (HAART). Given the appropriate stimulus, latently infected cells can reactivate and start producing infectious virions. The susceptibility of these cell populations to HIV-1, their life span, their proliferative capacity, and their ability to periodically produce infectious virus subsequent to alterations in cellular physiology and/or immunologic controls are critical issues which determine the contribution of these cells to viral persistence.

Medicinal plants have been widely used to treat a variety of infectious and non-infectious ailments. According to one estimate, 25% of the commonly used medicines contain compounds isolated from plants. Several plants could offer a rich reserve for drug discovery of infectious diseases, particularly in an era when the latest separation techniques are available on one hand, and the human population is challenged by a number of emerging infectious diseases on the other hand. Among several other ailments, viral infections, particularly infections associated with human immunodeficiency virus type 1 (HIV-1) and 2 (HIV-2), and newly emerging infectious viruses have challenged mankind survival. Of importance, a variety of medicinal plants have shown promise to treat a number of viral infections, and some of them possess broad-spectrum antiviral activity. In the past, exploration into the antiviral activity of various promising medicinal plants was limited due to: (a) highly infectious nature of viruses and (b) lack of appropriate separation techniques for the identification of antiviral components from plants. Development of vector-based strategies, in which non-infectious molecular clone of a virus could be used for antiviral screening purposes, and advancement in separation technologies offers promise for medicinal plants usage in modern drug discovery. This article describes potential antiviral properties of medicinal plants against a diverse group of viruses, and suggests screening the potential of plants possessing broad-spectrum antiviral effects against emerging viral infections.

Human immunodeficiency virus type 1 (HIV-1) primarily infects CD4+ T cells and cells of the monocyte-macrophage lineage, resulting in immunodeficiency in an infected patient. Along with this immune deficiency, HIV-1 has been linked to a number of neurological symptoms in the absence of opportunistic infections or other co-morbidities, suggesting that HIV-1 is able to cross the blood-brain barrier (BBB), enter the central nervous system (CNS), and cause neurocognitive impairment. HIV-1-infected monocyte-macrophages traverse the BBB and enter the CNS throughout the course of HIV-1 disease. Once in the brain, both free virus and virus-infected cells are able to infect neighboring resident microglia and astrocytes and possibly other cell types. HIV-1-infected cells in both the periphery and the CNS give rise to elevated levels of viral proteins, including gp120, Tat, and Nef, and of host inflammatory mediators such as cytokines and chemokines. It has been shown that the viral proteins may act alone or in concert with host cytokines and chemokines, affecting the integrity of the BBB. The pathological end point of these interactions may facilitate a positive feedback loop resulting in increased penetration of HIV into the CNS. It is proposed in this review that the dysregulation of the BBB during and after neuroinvasion is a critical component of the neuropathogenic process and that dysregulation of this protective barrier is caused by a combination of viral and host factors including secreted viral proteins, components of the inflammatory process, the aging process, therapeutics, and drug or alcohol abuse.