Occupational HIV infection. Medical workers and HIV prevention

The analysis of the possibility of suffering injuries at a work place, their causes, the knowledge of HIV infection, attitude towards the infected person is presented. The work was carried out, starting from 1990. Every 2 years the anonymous questioning of members of the medical personnel of different specialties at medical institutions of different profile and level was carried out. Five questionings on injuries suffered during work, the knowledge of HIV infection and the attitude of members of the medical profession towards HIV-positive persons. In most cases injuries are inflicted by injection needles (79%), during operations (12%), by splinters of broken medical glassware and appliances (3%) and in other cases (6%). In 91% of cases injuries caused by needles occur in the process of placing caps on the needles. In the course of 9 years changes in the level of knowledge and the attitude towards HIV-infected persons occurred. Changes in the outlook and the knowledge of AIDS were due to the positive influence of intensive education directly at work places.     

Cellular immunity for prevention and clearance of HIV infection

Despite the major strides that have been made in HIV therapy with the advent of potent anti-retroviral drugs, these medications are quite expensive and are still not readily available for the vast majority of infected individuals worldwide. Even when available, the long-term toxicities associated with anti-retroviral medications and the frequent emergence of drug-resistance mutations can complicate therapy, making the formulation of effective vaccines imperative. This chapter will review the current state of understanding regarding cell-mediated immune responses that are associated with control of HIV replication. This knowledge has generated sound hypotheses regarding the prospects for augmenting cell-mediated immunity through immune-based therapies. With regard to prophylactic vaccines, it is presently unclear which vaccine-induced immune responses will protect against infection. While much progress has been made in formulating vaccine constructs designed to elicit cell-mediated immune responses, sterilizing immunity is unlikely to be achieved with the current vaccines. However, the ability to control viremia and prevent disease progression in animal infection models looks promising. The ability to measure immune responses has also advanced markedly over the past few years and will allow investigators to more accurately measure the immunogenicity of vaccine constructs, and correlate the magnitude and breadth of these responses with protection.     

Passive immunization protects guinea pigs from lethal toxoplasma infection

Abstract The cellular and humoral interactions that contribute to protective immunity in toxoplasmosis were studied by adoptive transfer of selective cell populations or immune serum and its fractions into normal syngeneic strain 2 guinea pigs. The results of this study with the RH strain of Toxoplasma gondii confirm and extend the findings of previous studies by showing that the passive transfer of parasite-sensitized T cells or of immune serum from previously infected donors protected recipient guinea pigs against lethal toxoplasmosis. An additional key finding was that similar levels of complete protection against lethal infection occurred in guinea pigs receiving partially purified anti- Toxoplasma immunoglobulins or immune cells that had been enriched for B cells prior to transfer. Cells residing in the spleen, lymph nodes and peritoneal cavity, but not the thymus, were equally effective in conferring immunity to challenged recipients. In addition, cell titration experiments revealed that guinea pigs could survive T. gondii infection by infusing them with as little as 2 × 10⁷ sensitized T cells or B cells. Unlike protection mediated by T cells, protection against lethal disease occurring in the B cell recipients was associated with the formation of Toxoplasma antibodies. These findings illustrate the major role of both humoral and cell-mediated immunity in affording protection against toxoplasmosis based on a guinea pig model of the human disease.     

HIV disease prevention and treatment. A model for local planning.

Since first reported in 1981, about a fourth of all cases of the acquired immunodeficiency syndrome in the United States have occurred in California. In response to the human immunodeficiency virus (HIV) epidemic, California has developed a five-point strategy consisting of epidemiologic surveillance; prevention education; the provision of medical treatment and supportive services; research; and continuous planning, evaluation, and coordination of programs. Given the size and tremendous environmental and cultural diversity of California, as well as the variable local impact of HIV disease local jurisdictions need to develop HIV disease prevention and treatment plans specifically tailored to the circumstances of their communities. At a minimum, these plans should include central participatory planning, epidemiologic surveillance, HIV antibody testing and prevention education programs, provision for medical treatment and social support services, and coordination of financing mechanisms. We present a model for such plans.     

Knowledge and beliefs of international travellers about the transmission and prevention of HIV infection.

OBJECTIVES: To measure the perceived risk of acquired immunodeficiency syndrome (AIDS) among international travellers, to measure their knowledge of the transmission and prevention of HIV infection abroad and to identify some of the determinants of this knowledge. DESIGN: Survey. SETTING: Travellers'' immunization clinic providing mostly primary preventive care to international travellers. PARTICIPANTS: All clients aged 18 to 50 years seen at the clinic between Oct. 2 and Dec. 21, 1989, before their departure. MAIN OUTCOME MEASURES: Sixteen statements measured knowledge of transmission and prevention of HIV infection. Standardized scales measured health beliefs. RESULTS: The response rate was 81% (331/409). Compared with other diseases AIDS was perceived to be associated with a low risk except by those travelling to countries with a high prevalence of AIDS. Most of the clients were found to have a good knowledge of HIV transmission to travellers, although some myths remained popular and some real routes of transmission, especially blood, remained underrated. In all, 70% of the subjects believed in the efficacy of condoms when used with local people, as compared with 79% when used with other tourists; this difference was greatest among travellers who perceived AIDS as being particularly severe but difficult to prevent. The determinants of the knowledge of HIV transmission and prevention were a high level of education, a mother tongue other than French, unmarried status, a high prevalence of AIDS at the destination, the duration of the trip and a high perceived risk of HIV infection. CONCLUSIONS: Counselling should teach travellers (a) not to underestimate their risk of HIV infection during their trip, (b) to decrease the risk of requiring health care in developing countries and (c) to rely on their own prudent sexual behaviour rather than on their assessment of the level of risk posed by the environment.     

Understanding drug resistance for monotherapy treatment of HIV infection

The purpose of this study was to investigate strategies in the monotherapy treatment of HIV infection in the presence of drug-resistant (mutant) strains. A mathematical system is developed to model resistance in HIV chemotherapy. It includes the key players in the immune response to HIV infection: virus and both uninfected CD4⁺ and infected CD4⁺ T-cell populations. We model the latent and progressive stages of the disease, and then introduce monotherapy treatment. The model is a system of differential equations describing the interaction of two distinct classes of HIV—drug-sensitive (wild type) and drug-resistant (mutant)—with lymphocytes in the peripheral blood. We then introduce chemotherapy effects. In the absence of treatment, the model produces the three types of qualitative clinical behavior—anuninfected steady state, andinfected steady state (latency), andprogression to AIDS. Simulation of treatment is provided for monotherapy, during theprogression to AIDS state, in the consideration of resistance effects. Treatment benefit is based on an increase or retention in CD4⁺ T-cell counts together with a low viral titer. We explore the following treatment approaches: an antiviral drug which reduces viral infectivity that is administered early—when the CD4⁺ T-cell count is ≥300/mm³, and late—when the CD4⁺ T-cell count is less than 300/mm³. We compare all results with data. When treatment is initiated during the progression to AIDS state, treatment prevents T-cell collapse, but gradually loses effectiveness due to drug resistance. We hypothesize that it is the careful balance of mutant and wild-type HIV strains which provides the greatest prolonged benefit from treatment. This is best achieved when treatment is initiated when the CD4⁺ T-cell counts are greater than 250/mm³, but less than 400/mm³ in this model (i.e. not too early, not too late). These results are supported by clinical data. The work is novel in that it is the first model to accurately simultate data before, during and after monotherapy treatment. Our model also provides insight into recent clinical results, as well as suggests plausible guidelines for clinical testing in the monotherapy of HIV infection.     

HIV prevention for indigenous people of the Amazon basin.

This study identifies theoretically-based predictors of condom use in a sample of 251 sexually active adults recruited from Sao Gabriel da Cachoeira and six indigneous communities of the Upper Rio Negro region of Amazonas Brazil. The information-motivation-behavioral skills (IMB) model of AIDS-preventive behavior was used to describe the roles of HIV/AIDS knowledge, experiences with and attitudes toward condom use, peer influences, perceived vulnerability, monogamy and behavioral skills. A predictive path analytic model revealed significant predictors of more condom use including male gender, greater sexual HIV knowledge, positive experiences and attitudes about condom use, multiple partners, and greater behavioral skills. Results suggest that attention to behavioral skills for negotiating safer sex and instruction in the correct use of condoms are important elements in reducing high risk behaviors. Increasing the specific knowledge level of indigenous people regarding the complexities of sexual transmission of HIV is crucial and should be addressed. Heightening individuals' understanding of the limited protection of serial monogamy, and the need to conduct gender-specific training for behavior change to reduce transmission of HIV should be an additional goal of Brazilian health professionals. Obstacles to the implementation of the IMB HIV prevention program in Amazonas are noted and an alternative Brazilian HIV/AIDS prevention program is discussed.