Efficacy of Oral Encochleated Amphotericin B in a Mouse Model of Cryptococcal Meningoencephalitis.

Cryptococcus neoformans is an encapsulated yeast responsible for approximately a quarter of a million deaths worldwide annually despite therapy, and upwards of 11% of HIV/AIDS-related deaths, rivaling the impact of tuberculosis and malaria. However, the most effective antifungal agent, amphotericin B, requires intravenous delivery and has significant renal and hematopoietic toxicity, making it difficult to utilize, especially in resource-limited settings. The present studies describe a new nanoparticle crystal encapsulated formulation of amphotericin B known as encochleated amphotericin B (CAmB) that seeks to provide an oral formulation that is low in toxicity and cost. Using a 3-day delayed model of murine cryptococcal meningoencephalitis and a large inoculum of a highly virulent strain of serotype A C. neoformans, CAmB, in combination with flucytosine, was found to have efficacy equivalent to parental amphotericin B deoxycholate with flucytosine and superior to oral fluconazole without untoward toxicity. Transport of fluorescent CAmB particles to brain as well as significant brain levels of amphotericin drug was demonstrated in treated mice, and immunological profiles were similar to those of mice treated with conventional amphotericin B. Additional toxicity studies using a standardized rat model showed negligible toxicity after a 28-day treatment schedule. These studies thus offer the potential for an efficacious oral formulation of a known fungicidal drug against intrathecal cryptococcal disease.IMPORTANCECryptococcus neoformans is a significant global fungal pathogen that kills an estimated quarter of a million HIV-infected individuals yearly and has poor outcomes despite therapy. The most effective therapy, amphotericin B, is highly effective in killing the fungus but is available only in highly toxic, intravenous formulations that are unavailable in most of the developing world, where cryptococcal disease in most prevalent. For example, in Ethiopia, reliance on the orally available antifungal fluconazole results in high mortality, even when initiated as preemptive therapy at the time of HIV diagnosis. Thus, alternative agents could result in significant saving of lives. Toward this end, the present work describes the development of a new formulation of amphotericin B (CAmB) that encapsulates the drug as a crystal lipid nanoparticle that facilitates oral absorption and prevents toxicity. Successful oral absorption of the drug was demonstrated in a mouse model that, in combination with the antifungal flucytosine, provided efficacy equal to a parental preparation of amphotericin B plus flucytosine. These studies demonstrate the potential for CAmB in combination with flucytosine to provide an effective oral formulation of a well-known, potent fungicidal drug combination.

Syphilis in HIV-infected persons.

Since syphilis and HIV infection are associated with each other at a higher rate than expected by chance, all HIV-infected persons and persons with syphilis should be tested for syphilis and vice versa. Because the immunological dysfunction of HIV-infected patients can interfere in clearing of T. pallidum, concomitant infection with T. pallidum requires that maximal doses of appropriate antibiotics be given (Table 2). Although falling nontreponemal titers, especially in early HIV stages, is evidence of adequate treatment, some appropriately treated HIV-infected persons will maintain a high persistent titer. If reinfection is ruled out, they require only one or two retreatments. Because some HIV-infected persons will inappropriately decrease their titer level, only adequate treatment (Table 2) gives the clinician confidence that the patient is cured.

AIDS/HIV in the US military.

HIV infection (AIDS) burst upon the scene a decade ago. Because it is a sexually transmitted disease that infects blood and kills its victim, it is military relevant and will impact on all aspects of the military. The US Army Medical Research and Development Command as 'Lead Agent for Infectious Disease Research' in the Department of Defense has developed a comprehensive approach to address military concerns: surveillance of infection rates (intelligence) around the world and in the military; behavioural research to develop more effective means of education to change behaviour; and biological research to develop a quick and easy field test, and a vaccine or drug to prevent the disease from occurring despite exposure. Its success will influence the success of the Army in the future.

Relating cognitive function to military aviator performance in early HIV infection.

There has been controversy about whether cognitive changes occur in early human immunodeficiency virus (HIV) disease. In those studies reporting cognitive changes, these are typically subclinical, and their relationship to daily and/or occupational functioning has not been addressed. The potential effects of changes may vary as a function of occupational demands. This is germane to military performance, where occupational demands cover a wide spectrum of complexity. In particular, such effects are important to consider in the many cognitively demanding specialties associated with military aviation. This paper will explore ways in which possible HIV-related military performance decrements in aviators may be measured empirically. First, studies from Walter Reed Army Medical Center (WRAMC), which have shown cognitive changes in early HIV disease, will be described. This will be followed by a summary of presentations and discussions at a conference in November 1990, entitled 'HIV and Military Performance: Assessment Methodologies' held at WRAMC. The third section of the paper will describe a programme of research, which is developing measures to detect cognitive difficulties in civilian aviators. The application of measures from this research to research on HIV will be discussed. Finally, a research programme being developed to examine the possible impact of HIV-related cognitive changes on military aviator performance will be described.

The human immunodeficiency virus.

HIV is a complex retrovirus. Like some other viruses it infects host cells for life, but unlike other viruses it appears to do so every time. Its elaborate genetic regulation enables it to remain relatively dormant, replicating steadily but slowly. On appropriate stimulation, it is capable of explosive up-regulation, releasing high numbers of new infectious virus. It replicates in an error-prone way, constantly changing its structure to improve its infectivity while presenting the host's immune system with a constantly moving target.

The relationship between outpatient drug costs and disease progression in the human immunodeficiency virus-infected population. The Military Medical Consortium for Applied Retroviral Research.

As the focus of the management of human immunodeficiency virus (HIV) infection turns from the treatment of AIDS to the entire continuum of the disease, projection of long-term healthcare costs becomes increasingly important. Rather than a fulminant disease treated primarily inside the hospital, HIV infection will become a chronic condition requiring years of outpatient monitoring and pharmacologic intervention with attending increases in pharmacy costs. The objective of this study was to characterize outpatient drug costs by Walter Reed (WR) disease stage in order to estimate the association of disease progression and outpatient prescription drug costs. We hypothesized that there was an association between HIV disease progression, measured by the WR Staging Classification System, and outpatient prescription drug costs. Outpatient drug costs were summarized for 190 HIV-positive patients during a three-month period who presented at Walter Reed Army Medical Center for staging and follow-up. The overall median cost per day per patient for all stages was $3.21 (range $0.01-53.45) with wide variation between patients. Daily costs for patients in WR stage V were the greatest (median $9.26). There was a significant association between WR stage of disease and outpatient drug costs (Spearman rho = 0.51, t = 6.9, df = 188, p less than 0.001). The association was not completely linear because costs in WR stage VI were less than WR stages IV or V. Annual extrapolated outpatient drug costs for these 190 patients would be nearly $0.5 million.

Efficacy trial of a parenteral gonococcal pilus vaccine in men.

A randomized, placebo-controlled, double-blind efficacy trial of a purified gonococcal pilus vaccine composed of a single pilus type was tested in 3123 men and 127 women volunteers. Either 100 micrograms of vaccine or a placebo was given intradermally on day 1 and day 14. Each group was evenly matched with respect to age, sex, prior history of a sexually transmitted disease, sexual exposure during the study and attrition from the study. None of the women volunteers acquired gonorrhoea during the trial. In the male volunteers, 108 vaccine and 102 placebo recipients acquired gonorrhoea 15 days or later after the initial immunization. Vaccines developed a sustained ELISA antibody response to homologous and heterologous pili, but the latter titres were approximately 40% as high as the homologous pilus antibody rises. There were, however, no increases in inhibition of attachment antibody (IEA) titres. Local antibodies (semen) against homologous and heterologous strains were also elicited (ELISA). The vaccine was safe and did not alter the clinical expression of disease. This gonococcal pilus vaccine composed of a single pilus type failed to protect men against gonococcal urethritis.

Controversies regarding the natural history and treatment of syphilis in HIV disease.

Because of the immunologic dysfunction of HIV-infected patients, concomitant infection with T. pallidum requires that maximal doses of appropriate antibiotics be given, and the expected falls in nontreponemal antibody titer cannot be relied upon to certify a cure. Genital ulcer disease appears to increase the risk of acquiring HIV. Therefore, all HIV-infected persons and persons with syphilis should be tested for both syphilis and HIV.

Human immunization with Pgh 3-2 gonococcal pilus results in cross-reactive antibody to the cyanogen bromide fragment-2 of pilin.

In 1983, a gonococcal pilus vaccine failed to show protection in a large, placebo-controlled, double-blind field trial. The epitopic response to this vaccine was investigated in a random subgroup of 20 vaccine recipients. Using Western blot analysis of the immunizing pilus and its cyanogen bromide (CNBr) fragments, IgG antibody to pilin was detected before immunization in all individuals. Preexistent antibody to the CNBr-2 and CNBr-3 fragments of pilin was detected in 65% and 5% of individuals, respectively. Pilus immunization resulted in a vigorous response to the CNBr-2 fragment in 100% of the individuals tested; only 33% developed antibody to the CNBr-3 fragment. Absorptions of postimmunization sera with different gonococcal strains resulted in either complete or partial removal of antibody to the CNBr-2 fragment. In the context of an unsuccessful vaccine trial, these results suggest that antibody to the CNBr-2 fragment of pilin may not be protective.

Studies in volunteers to evaluate candidate Shigella vaccines: further experience with a bivalent Salmonella typhi-Shigella sonnei vaccine and protection conferred by previous Shigella sonnei disease.

A bivalent vaccine consisting of Salmonella typhi strain Ty21a containing the 120 MDa plasmid of Shigella sonnei and expressing both S. typhi and S. sonnei lipopolysaccharides (LPS) on its surface was previously shown to protect significantly against S. sonnei disease in experimental challenge studies. However, protective efficacy could not be reconfirmed in volunteers with five subsequent lots of vaccine. One vaccine lot which resembled the initial protective lots of vaccine in biochemical and serological tests, and by electron microscopy, was administered to 16 volunteers who ingested three doses of 10(9) organisms each. Antibody secreting cells (ASC) specific for S. sonnei LPS were detected in the blood of 100% of vaccines, but no protection of these vaccines was demonstrated during a S. sonnei challenge study. To assess the ability of the volunteer model to detect infection-derived immunity, six volunteers who had had clinical shigellosis due to S. sonnei two months earlier were rechallenged with wild-type S. sonnei, together with 12 controls. Prior infection provided 100% protection against febrile illness (p = 0.05) and diarrhea (p = 0.04), thereby validating the volunteer model for assessing Shigella vaccines.

Relative inefficiency of soluble recombinant CD4 for inhibition of infection by monocyte-tropic HIV in monocytes and T cells.

Macrophages are major viral reservoirs in the brain, lungs, and lymph nodes of HIV-infected patients. But not all HIV isolates infect macrophages. The molecular basis for this restrictive target cell tropism and the mechanisms by which HIV infects macrophages are not well understood: virus uptake by CD4-dependent and -independent pathways have both been proposed. Soluble rCD4 (sCD4) binds with high affinity to gp 120, the envelope glycoprotein of HIV, and at relatively low concentrations (less than 1 microgram/ml) completely inhibits infection of many HIV strains in T cells or T cell lines. HTLV-IIIB infection of the H9 T cell line was completely inhibited by prior treatment of virus with 10 micrograms/ml sCD4: no p24 Ag or HIV-induced T cell syncytia were detected in cultures of H9 cells exposed to 1 x 10(4) TCID50 HTLV-IIIB in the presence of sCD4. Under identical conditions and at a 100-fold lower viral inoculum, 10 micrograms/ml sCD4 had little or no effect on infection of monocytes by any of six different HIV isolates by three different criteria: p24 Ag release, virus-induced cytopathic effects, and the frequency of infected cells that express HIV-specific mRNA. At 10- to 100-fold higher concentrations of sCD4, however, infection was completely inhibited. Monoclonal anti-CD4 also prevented infection of these same viral isolates in monocytes. The relative inefficiency of sCD4 for inhibition of HIV infection in monocytes was a property of the virion, not the target cell: HIV isolates that infect both monocytes and T cells required similarly high levels of sCD4 (100 to 200 micrograms/ml) for inhibition of infection. These data suggest that the gp120 of progeny HIV derived from macrophages interacts with sCD4 differently than that of virions derived from T cells. For both variants of HIV, however, the predominant mechanism of virus entry for infection is CD4-dependent.