Prevalence of human T cell lymphotropic virus types 1 and 2 (HTLV-1/2) in selected Tijuana subpopulations.

To assess the prevalence of human T cell lymphotropic virus type 1 and 2 (HTLV-1/2) infections among potentially high-risk populations in the city of Tijuana, Mexico, the prevalence of specific antibodies was determined and information on risk behaviors was obtained between June and October 1988. The study involved 631 presumably healthy individuals, randomly selected from a study population recruited sequentially from prisoners, prostitutes, and injecting drug users (IDUs), and randomly from homosexual and bisexual men. The presence of HTLV-1/2 antibodies was determined by enzyme immunoassay and an immunofluorescence method, and positive reactions were confirmed by a radioimmunoprecipitation assay and Western blot. The prevalence of HTLV-1/2 was 2% (2 of 105) among prostitutes, 7% (29 of 410) among prisoners, 1% (1 of 105) among homosexual/bisexual men, and 21% (22 of 106) among IDUs. To properly identify the specific HTLV type, a subsequent sample of 41 imprisoned IDUs were voluntarily and anonymously recruited in June 1990 and asked to donate 20 ml of whole blood. Twenty-two percent (9 of 41) were serologically positive for HTLV-1/2, and polymerase chain reaction analysis performed on peripheral blood mononuclear cells identified HTLV-2 as the specific virus prevalent in this group. Two individuals were positive for human immunodeficiency virus type 1 (HIV-1). One of these individuals was coinfected with HTLV-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of protective immunogenicity of microbial vaccines: effects of cyclophosphamide pretreatment in Venezuelan encephalitis, Q fever and tularaemia.

Administration of high-dose (250 mg/kg) cyclophosphamide (CY) to guinea-pigs and mice 3 days prior to immunization with inactivated vaccine derived from Venezuelan encephalitis virus (VE), Coxiella burnetii and Francisella tularensis resulted in accentuated and prolonged delayed-type hypersensitivity (DTH) and in vitro cellular immunity (CMI) to specific antigen. Humoral antibody were either absent or significantly lower in CY-pretreated animals compared to immunized non-pretreated controls. CY pretreatments precluded protection in the VE virus model, suggesting that resistance is related to antibody. In the Q fever model, the protective immunogenicity of vaccine was preserved or increased by CY pretreatment suggesting that cell-mediated immunity is the important factor. In the tularaemia bacterial system, there was a complex effect of CY pretreatment on the low-grade protection afforded by killed vaccine against virulent infection. These findings suggest that the inability of killed vaccines to induce high-grade resistance against tularaemia and Q fever may be due in part to a suppressive B cell response which is eliminated by CY. These studies have given useful information on the relative significance of components of the specific immune response and may lead to an increased understanding of the mechanisms of action of vaccines and adjuvants.

Evaluation in humans of a new, inactivated vaccine for Venezuelan equine encephalitis virus (C-84).

A new, formalin-inactivated vaccine for Venezuelan equine encephalitis (VEE) virus (C-84), prepared from an attenuated vaccine strain of virus (TC-83), was tested in humans. Only occasional, mild, local and systemic reactions were noted in 28 volunteers; no meaningful changes in clinical laboratory values occurred. The vaccine augmented preexisting titers of serum neutralizing antibody to VEE virus in seropositive recipients of TC-83 vaccine, and it induced high titers of neutralizing antibody in nonimmune subjects after one primary and two booster vaccinations. Circulating antibody persisted for at least 14 months in these persons. The neutralizing antibody produced after one dose of C-84 vaccine in immune subjects and after booster doses in nonimmune subjects had broad cross-reactivity within the VEE virus complex. The C-84 vaccine induced a VEE virus-specific lymphocyte transformation response. The vaccine was safe, and immunologic results showed it to be highly antigenic in healthy immune and nomimmune adults.