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Immune dysregulation initiated by a profound loss of CD4+ T-cells is fundamental to HIV-induced pathogenesis. Infection of domestic cats with a non-pathogenic lentivirus prevalent in the puma (puma lentivirus, PLV or FIV(pco)) prevented peripheral blood CD4+ T-cell depletion caused by subsequent virulent FIV infection. Maintenance of this critical population was not associated with a significant decrease in FIV viremia, lending support to the hypothesis that direct viral cytopathic effect is not the primary cause of immunodeficiency. Although this approach was analogous to immunization with a modified live vaccine, correlates of immunity such as a serum-neutralizing antibody or virus-specific T-cell proliferative response were not found in protected animals. Differences in cytokine transcription profile, most notably in interferon gamma, were observed between the protected and unprotected groups. These data provide support for the importance of non-adaptive enhancement of the immune response in the prevention of CD4+ T-cell loss.
Aims: To develop a selective medium for isolation of F. tularensis, F. novicida and F. philomiragia from environmental samples.
Methods and Results: A selective media, cysteine heart agar with 9% chocolatized sheep blood, containing polymyxin B, amphotericin B, cyclohexamide, cefepime and vancomycin (CHAB‐PACCV) was developed and evaluated for growth of Francisella spp. No differences were observed in recovered colony forming units (CFUs) for F. tularensis, F. novicida and F. philomiragia on CHAB‐PACCV vs nonselective CHAB. Growth of non‐Francisella species was inhibited on CHAB‐PACCV. When environmental samples were cultured on CHAB and CHAB‐PACCV, only CHAB‐PACCV allowed isolation of Francisella spp. Three new Francisella strains were isolated directly from seawater and seaweed samples by culture on CHAB‐PACCV.
Conclusions: CHAB‐PACCV can be used for direct isolation of Francisella spp from environmental samples.
Significance and Impact of the Study: Francisella spp. show a close association with environmental sources. Future utilization of CHAB‐PACCV for isolation of Francisella spp. directly from environmental samples should prove valuable for investigating outbreaks and human infections attributed to environmental exposure.
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