Comparison of antibody response to three different schedules of pneumococcal vaccination in Human Immunodeficiency Virus (HIV) infected individuals

Abstract

Streptococcos pneumoniae is an important agent of community infection. Severe pneumococcal infection leading to pneumonia, febrile bacteremia and meningitis is a major cause of morbidity and mortality all over the world. Although all age groups may be affected, young children and elderly population have highest risk of invasive infection. In addition, persons suffering from a wide range of chronic conditions and immune deficiency, such as HIV infection, are at increased risk of pneumococcus illness. Since 1989, The Advisory Committee on Immunization Practices and Brazilian Health Ministry recommends more extensive use of the pneumococcal polysaccharide vaccine, which should be administered to all persons at increased risk, including HIV infected individuals.Polysaccharide capsule antigens do not promote protection in children aged less than 2 years and in individuals with advanced immunological impairments (HIV/AIDS). Furthermore, the polysaccharide vaccines do not induce immunological memory. Its effectiveness in preventing invasive disease among immunosuppressed persons is less clear. Studies of the effectiveness of pneumococcal vaccine in HIV-infected patients have produced conflicting results; however, it was clearly demonstrated that HIV-infected patients (particularly those in advanced stage of immunosuppression) have reduced total and functional antibody responses to pneumococcal vaccine.Like the polysaccharide vaccines, the conjugate vaccines induce protection only against the serotypes involved, however, the link of polysaccharide to a protein induce T cells immune response, able to stimulate B cells polysaccharide specific. These B cells will produce antibodies and will be into memory cells.Moreover, the main reservoir of S.pneumoniae is nasopharingeal. The incidence of invasive illness is directly related to the prevalence of carrier state, therefore, it is natural to infer that the protection given for the vaccine against pneumococcus is related to the reduction of healthful carrying people. Although conflicting results, studies suggest polysaccharide vaccine does not modify the carrier state, however, some studies evidence this reduction after application of the conjugated vaccine. Few comparative studies between polysaccharide and conjugated pneumococcal vaccines in healthful and HIV positive adults had been performed and have gotten conflicting results. The initial stimulation with vaccine conjugated, that promotes a memory response followed by a booster with polysaccharide vaccine could promote might provide higher and longer protection and reduction of the carrier state. (AU)