Raxit J. Jariwalla

Antiviral and Immunomodulatory Activities of Ascorbic Acid

It has been known since the early days of ascorbic acid research that the appearance of scurvy, which is caused by deficiency of this vitamin, is associated with decreased resistance to infection (Reid and Briggs, 1953). Over the years, it has become well recognized that ascorbate can bolster the natural defense mechanisms of the host and provide protection not only against infectious disease, but also against cancer and other chronic degenerative diseases. The functions involved in ascorbate’s enhancement of host resistance to disease include its biosynthetic (hy-droxylating), antioxidant, and immunostimulatory activities. In addition, ascorbate exerts a direct antiviral action that may confer specific protection against viral disease. The vitamin has been found to inactivate a wide spectrum of viruses as well as suppress viral replication abd expression in infected cell. In this article we review the antiviral and immunotimulatory effects of ascorbate and their relevance to control of acute and chronic viral infections. Detailed discussion of thr biosynthetic activities of ascorbate has been presented in a review by England and Seifter (1986). The antinoxidant function of ascorbate has been reviewed recently by Bendich (1988)

Mechanistic aspects of ascorbate inhibition of human immunodeficiency virus.

We have investigated the molecular basis of the inhibitory effect of ascorbate (vitamin C) on human immunodeficiency virus (HIV) expression in unstimulated chronically infected and reporter cell lines. Comparison of intracellular HIV RNA and protein patterns of ascorbate-treated cells with corresponding patterns of untreated controls, did not show significant differences in the synthesis or processing of individual viral RNA and polypeptides, indicating that the inhibitory effect of ascorbate is not directed at steps of viral transcription or translation. Enzyme assays on cell extracts showed that the activity of an HIV LTR-directed reporter protein made in ascorbate-treated cells was reduced to approximately 11% relative to that of untreated control. These results, combined with previous observations on the suppression of HIV RT activity, are consistent with a mechanism of action in which ascorbate exerts a posttranslational inhibitory effect on HIV by causing impairment of enzymatic activity.

Localization of the antigenic sites and intrinsic protein kinase domain within a 300 amino acid segment of the ribonucleotide reductase large subunit from herpes simplex virus type 2

The 140-kDa ribonucleotide reductase (RR1) protein of herpes simplex virus type 2 (HSV-2) functions as the large subunit of virus-specified RR1 and exhibits an intrinsic protein kinase (PK) activity at its unique NH2-terminal region. The N-terminal half of RR1 contains the protein and DNA functions of the morphological transforming region III (mtrIII) of HSV-2. In the present study, we have expressed a number of truncated RR1 derivatives in a mammalian expression vector containing NH2-terminal RR1 gene fragments and amber mutants generated by site-specific mutagenesis. These derivatives, synthesized in transient expression assays, were used as test antigens to localize the epitopes of a panel of HSV-2 RR1-reactive monoclonal antibodies and to fine-map the PK catalytic domain. Our data show that the epitope for HSV-2-specific monoclonal antibody 6A-6 is located in a region of RR1 protein spanning aa 72-350. The epitopes for cross-reactive antibodies to HSV RR1, i.e., 48S and 51S, are formed predominantly by a stretch of amino acid residues specified by aa 350-376 of the RR1 molecule. The 6A-6 antibody utilized in conjunction with the RR1 amber mutants has allowed us to define a 278 aa domain within the NH2-terminal half of the 140-kDa RR1 (aa 72-350) that is sufficient for PK activity.

Micro-nutrient Imbalance in HIV Infection and AIDS: Relevance to Pathogenesis and Therapy

A growing body of evidence from cross-sectional epidemiologic studies has shown that HIV-infected persons and AIDS patients exhibit abnormal blood levels of key micro-nutrients and sulphated amino acids (thiols) that are prevalent early in infection. The abnormalities appear to arise from an interplay of malnutrition, malabsorption, metabolic alteration and nutrient depletion associated with the risk factors of HIV infection. The nutrients in question include vitamins A, B-complex, C, E and carotenes (precursor of vitamin A); trace elements selenium, copper and zinc; and thiols, namely, cysteine and the tripeptide glutathione (GSH). Most of these compounds are well known in providing protective physiologic functions, serving as vital antioxidants in scavenging toxic free radicals and/or as immunomodulators in maintaining cell-mediated/humoral responses. Some B-complex nutrients (namely, B6 and B12) have been linked to maintenance of cognitive functions. Therefore, micro-nutrient imbalance may contribute t...

Comparative Analysis of Ascorbate and AZT Effects on HIV Production in Persistently Infected Cell Lines

The effects of ascorbate (vitamin C) and azidothymidine (AZT) were examined on HIV expression in permanently infected and reporter cell lines. In T-lymphocytic HXB cells, constitutively producing moderate to high levels of virus, ascorbate suppressed HIV production and reduced the yield of infectious virus released into the culture supernatant. AZT, which has been reported to block de novo infection of freshly infected cells, did not inhibit constitutive virus production in HXB cells. In latently infected ACH-2 T-cells, producing low basal level of virus, exposure to phorbol ester (PMA) caused about 10-fold increase in virus production. Pre-treatment of ACH-2 cells with ascorbate followed by PMA stimulation resulted in a dose-dependent reduction in the extracellular level of HIV reverse transcriptase activity. AZT treatment did not suppress HIV activation in PMA-stimulated ACH-2 cells. In mixed cultures of uninfected HLCD4-CAT and infected HL2/3 cells, ascorbate did not affect virus-induced (taX-mediated)...

Micronutrient Synergy in the Control of HIV Infection and AIDS

Acquired immune deficiency syndrome (AIDS) has become a global health pandemic and the most common cause of death among young adults aged 20-24 years (Patton et al., 2009). According to the UN/AIDS Global Report published in November 2010 (UNAIDS 2010), about 1.8 million persons died from AIDS-related causes in the year 2009 alone. At the end of that year, the epidemic had left behind totally 16.6 million orphans, defined as those under 18 who had lost one or both parents to AIDS. Since the beginning of the epidemic, nearly 30 million people have died from AIDS-related causes. At the end of 2009, an estimated 30.8 million adults and 2.8 million children were living with HIV, the human immunodeficiency virus linked to AIDS; with women accounting for just over one-half of all adults living with HIV worldwide. During the same year, about 2.6 million persons became newly infected with HIV, including 370,000 children. Of all people living with HIV, about 68% reside in Sub-Saharan Africa (UNAIDS 2010). Despite these gruesome statistics, there is no cure in sight. Current treatment is based on the use of antiretroviral (ARV) drugs targeted against HIV at various steps in viral replication (Sleaseman and Goodenow 2003). Although ARV drugs can reduce viral load in the bloodstream, they neither cure HIV infection nor restore the immune system to combat AIDS (Roederer 1998, Pakker et al., 1998). Virus is known to persist indefinitely in reservoirs of latently-infected cells and emergence of drug-resistant strains is common. Furthermore, the effectiveness of ARVs in having any clinical benefits at all depends upon a number of factors, particularly the CD4 count and the nutritional status of patients at the point at which ARV treatment is commenced (Hong et al., 2001, Paton et al., 2006). Additionally, drugs are higly toxic and are often associated with adverse side effects to various organs of the body, including the bone marrow and liver, (Fischl et al., 1987, Richman et al., 1987, Costello et al., 1988, Abrescia et al., 2008), cellular mitochondria (Carr et al., 2001), and with lipodystrophy and dyslipidemia (Carr et al., 1998). Consequently, there is need for safe and effective, nontoxic therapy that can not only restore the immune system and keep virus multiplication/spread in check but also block AIDS progression without harming cells of the host. This review will focus on the relationship of nutrition to infection and immunity and evidence from experimental and clinical studies on the potential value of micronutrients and their combinations in controlling HIV infection and reducing symptoms associated with AIDS.

Micronutrient cooperation in the suppression of HIV production in chronically and latently infected cells.

Nutrients are known to display pharmacologic activity against viruses and to exert cooperative effects in cells. To study the influence of nutrient cooperation on HIV production in chronically infected T lymphocytes, we evaluated the individual and combined effects of nutrients on HIV-1 reverse transcriptase (RT) released into the culture supernatant. In unstimulated cells, low concentrations of single nutrients, namely ascorbic acid (AA), green tea polyphenols (GT) or lysine, did not significantly suppress HIV-1 RT production. However, when GT (25 µg/ml) and AA (32-64 µg/ml) were combined and applied to cells, extracellular RT was significantly reduced relative to the control. Combining GT (25 µg/ml) with lysine (25 µg/ml) also reduced the RT level to a greater extent (51% of control) than was observed wih lysine alone, and the addition of AA (16 µg/ml) to the combination further decreased RT to 17% of the control (p=0.06). Under the same assay conditions, the nucleoside analog azidothymidine did not significantly suppress HIV production at low to moderate concentrations (0.5-1.0 µg/ml), but did reduce the RT level to 40% of the control (p=0.02) at the highest dose tested (2 µg/ml). In unstimulated cells as well as in latently infected cells stimulated with mitogen (PMA or TNF-α), a nutrient mixture containing GT, AA and amino acids imparted significantly greater RT suppression than equivalent concentrations of key individual components. Nutrient effects on RT suppression were virus-specific and were not due to non-specific cellular toxicity. These results suggest that relatively non-toxic micronutrient combinations are more potent than single nutrients in suppressing virus production in chronically infected T cells, indicating that the constituent nutrients have a cooperative effect in HIV inhibition.