Amphibian antimicrobial peptides and Protozoa: Lessons from parasites

Antimicrobial peptides (AMPs) from amphibians and other eukaryotes recognize pathogenicity patterns mostly related to differences in membrane composition between the host and a variety of bacterial, fungal and protozoan pathogens. Compared to the other two groups, protozoa are fairly neglected targets in antimicrobial chemotherapy, despite their role as causative agents for scourges such as malaria, amoebiasis, Chagas' disease or leishmaniasis. Herein we review the scarce but growing body of knowledge addressing the use of amphibian AMPs on parasitic protozoa, the adaptations of the protozoan to AMP pressure and their impact on AMP efficacy and specificity, and the current and foreseeable strategies for developing AMPs into practical therapeutic alternatives against parasitic disease.     

Mother-to-child transmission of HIV in Botswana: an ethical perspective on mandatory testing

Mother-to-child transmission (MTCT) of HIV represents a particularly dramatic aspect of the HIV epidemic with an estimated 600,000 newborns infected yearly, 90% of them living in sub-Saharan Africa. Since the beginning of the HIV epidemic, an estimated 5.1 million children worldwide have been infected with HIV. MTCT is responsible for 90% of these infections. Two-thirds of the MTCT are believed to occur during pregnancy and delivery, and about one-third through breastfeeding. As the number of women of child bearing age infected with HIV rises, so does the number of infected children. It is apparent that voluntary testing in Botswana has made some valuable inroads in decreasing perinatal HIV transmission, but the statistics showing the increased rate of HIV infection among women 15-24 years of age are not very promising. After reviewing all the pertinent scientific data it is clear that mandatory HIV testing of all pregnant women in conjunction with the implementation of a full package of interventions would save thousands of lives -- mothers, newborns and others who could be infected as a result of these women not being aware of their HIV status. If the protection and preservation of human life is a priority in Botswana, then it is time to allow for mandatory HIV testing of all pregnant women, before it is too late for those who are the most vulnerable. To do less would be medically inappropriate and ethically irresponsible.     

Lipodystrophic syndromes: congenital or acquired diseases of adipose tissue

Lipodystrophic syndromes regroup a heterogeneous group of genetic or acquired diseases. Lipodystrophy, an altered development and/or repartition of body fat, is associated with alterations of lipid and glucose metabolism with insulin resistance. Genetic forms, rare, can be generalized and recessive resulting from mutations in the seipin or AGPAT2 gene. Partial lipodystrophies are dominant and observed in patients mutated in the gene encoding PPAR-gamma or lamin A/C, a gene seen also mutated in patients with syndromes of premature aging. Acquired forms are common and regroup the highly prevalent Metabolic Syndrome, hypercorticism together with lipodystrophy related to antiretroviral treatment of HIV-infected patients.     

Effect of ethanol on spectral binding, inhibition, and activity of CYP3A4 with an antiretroviral drug nelfinavir

Cytochrome P450 3A4 (CYP3A4) is the most abundant CYP enzyme in the liver and metabolizes approximately 50% of the drugs, including antiretrovirals. Although CYP3A4 induction by ethanol and impact of CYP3A4 on drug metabolism and toxicity is known, CYP3A4-ethanol physical interaction and its impact on drug binding, inhibition, or metabolism is not known. Therefore, we studied the effect of ethanol on binding and inhibition of CYP3A4 with a representative protease inhibitor, nelfinavir, followed by the effect of alcohol on nelfinavir metabolism. Our initial results showed that methanol, ethanol, isopropanol, isobutanol, and isoamyl alcohol bind in the active site of CYP3A4 and exhibit type I spectra. Among these alcohol compounds, ethanol showed the lowest K_D (5.9 ± 0.34 mM), suggesting its strong binding affinity with CYP3A4. Ethanol (20 mM) decreased the K_D of nelfinavir by >5-fold (0.041 ± 0.007 vs. 0.227 ± 0.038 μM). Similarly, 20 mM ethanol decreased the IC₅₀ of nelfinavir by >3-fold (2.6 ± 0.5 vs. 8.3 ± 3.1 μM). These results suggest that ethanol facilitates binding of nelfinavir with CYP3A4. Furthermore, we performed nelfinavir metabolism using LCMS. Although ethanol did not alter k_cat, it decreased the K_m of nelfinavir, suggesting a decrease in catalytic efficiency (k_cat/K_m). This is an important finding because alcoholism is prevalent in HIV-1-infected persons and alcohol is shown to decrease the response to antiretroviral therapy.     

Indinavir reduces Cryptosporidium parvum infection in both in vitro and in vivo models

The use of highly active antiretroviral therapy in persons with acquired immunodeficiency syndrome has reduced the prevalence of infection with Cryptosporidium parvum and the length and severity of its clinical course. This effect has in most cases been attributed to the recovery of the host immunity; however, some works suggest that human immunodeficiency virus protease inhibitors, indinavir in particular, which is one of the human immunodeficiency virus protease inhibitors used in highly active antiretroviral therapy, may be capable of controlling Microsporidia and Cryptosporidium infections, which are refractory to other treatments. The objective of the present study was to investigate the effect of human immunodeficiency virus protease inhibitors on C. parvum infections. Since preliminary experiments using ritonavir, saquinavir, and indinavir showed a drastic reduction of C. parvum infection both in vivo (neonatal Balb/c mice) and in vitro (human ileocecal adenocarcinoma tumour cell line) models, indinavir alone was tested in successive experiments. In vitro, the treatment of the sporulated oocysts with different concentrations of indinavir reduced the percentage of human ileocecal adenocarcinoma tumour cell line infected cells in a dose-dependent manner. For established infection, the treatment with 50 microM of indinavir decreased the percentage of infected cells in a time-dependent manner. In vivo, mice treated with indinavir at the same time they were infected with the oocysts showed a 93% reduction in the number of oocysts present in the entire intestinal contents and a 91% reduction in the number of intracellular parasites in the ileum. For established infection, indinavir treatment reduced the number of oocysts in the entire intestinal content by about 50% and the number of intracellular parasites in the ileum by about 70%. These data show that indinavir directly interferes with the cycle of C. parvum, resulting in a marked reduction in oocyst shedding and in the number of intracellular parasites. Protease inhibitors could be considered as good candidates for the treatment of cyptosporidiosis in immunosuppressed persons.     

SIV-specific T lymphocyte responses in PBMC and lymphoid tissues of SIV-infected pigtailed macaques during suppressive combination antiretroviral therapy

There is currently no SIV macaque model in which the effects of combination antiretroviral therapy on tissue immune responses and latent reservoirs have been measured. This study was performed to define the impact of combination therapy on the specificity and distribution of the T lymphocyte response in multiple tissue compartments. Pigtailed macaques (Macaca nemestrina) were infected with SIV/17E-Fr and treated with combination antiretroviral therapy consisting of 9-R-(2-phosphonomethoxypropyl)adenine (PMPA) and beta-2',3'-dideoxy-3'-thia-5-fluorocytidine (FTC). The SIV-specific T lymphocyte response was measured in peripheral blood, spleen and several lymph nodes at necropsy by IFN-gamma Elispot analysis. Two animals (one treated, one untreated) had high acute peak viremia, which was associated with lower SIV-specific T lymphocyte responses in the peripheral blood and lymphoid tissues. In the treated animal, viremia was controlled to low or undetectable for the study duration, and virus-specific responses remained low. The untreated animal remained viremic throughout the study and developed clinical symptoms of AIDS. In contrast, the two animals that had lower acute peak viremia (one treated, one untreated) had more robust T lymphocyte responses, and controlled viral replication. Virus-specific responses were detected in the treated animal despite 6 months of suppressive therapy. These data suggest that in this model, in the context of acute peak viremia and weak T cell responses, combination therapy may be essential to control virus replication and disease progression. Conversely, in the setting of low initial viremia and robust T lymphocyte responses, treatment does not have a detrimental effect on the immune response.     

Advance in treatment strategy and immune reconstruction against HIV-1 infection

HIV-1 can be considered an infection of the immune system, resulting in progressive and ultimately profound immune suppression. The availability of highly active antiretroviral therapy (HAART) has resulted in dramatic changes in the disease course in persons fortunate enough to have access to these medications, but long-term therapy is limited by the development of resistance as well as toxicities of the potent medication regimens. Emerging data indicate that individuals who have non-progressive clinical course control HIV-1 immunologically. This has bolstered hope that the immune response might be effectively augmented in persons with HIV infection. Recent data indicating that immediate treatment of acute infection leads to augmentation of antiviral immune responses have provided evidence that the immune system might be enhanced in certain situations. Therefore, investigation in the reconstitution of anti-HIV immune response in patients under HAART should provide encouragement for continuing to explore methods to obtain meaningful and durable immune enhancement as an adjunct to HAART in HIV-1 infection.