Differential tumor necrosis factor alpha production in simian immunodeficiency virus-infected rhesus macaques coinfected with Mycobacterium avium

Animal models to study Mycobacterium tuberculosis and HIV co-infection

Mycobacterium tuberculosis (M.tb) and human immunodeficiency virus (HIV) co-infection has become a public health issue worldwide. Up to now, there have been many unresolved issues either in the clinical diagnosis and treatment of M.tb/HIV co-infection or in the basic understanding of the mechanisms for the impairments to the immune system by interactions of these two pathogens. One important reason for these unsolved issues is the lack of appropriate animal models for the study of M.tb/HIV co-infection. This paper reviews the recent development of research on the animal models of M.tb/HIV co-infection, with a focus on the non-human primate models.

Single nucleotide polymorphisms within the promoter region of the rhesus monkey tumor necrosis factor-alpha gene

The human TNF-alpha gene is characterized by several single nucleotide polymorphisms (SNPs) in its promoter region, in part having been shown to influence TNF-alpha expression and susceptibility to various diseases. The rhesus macaque is widely used as an animal model for a variety of TNF-alpha associated pathological conditions, but little is known about genetic variation within the TNF-alpha promoter region. In order to check for such polymorphisms, primers based on rhesus sequence within 5' UTR were designed and used to amplify a approximately 1 kb product from genomic DNA of 29 animals. Sequencing and cloning revealed a total of 11 polymorphisms leading to five different haplotypes.

HIV-1 suppression during acute scrub-typhus infection

BACKGROUND

In HIV-1-infected individuals, viral load has been reported to rise transiently if an acute infection with another organism occurs. Our study was prompted by the unexpected finding that HIV-1 copy number fell during an acute infection with Orientia tsutsugamushi, the causative agent of scrub typhus.

METHODS

Serial HIV-1 viral load determinations were made in ten Thai adults with scrub typhus, who were not receiving antiretroviral therapy, and in five HIV-1-infected patients who had other infections (four malaria, one leptospirosis), during and after acute infections. Sera from HIV-1-infected patients with scrub typhus and from mice immunised with O. tsutsugamushi were examined for HIV-1-suppressive activity.

FINDINGS

Median viral load 3 days after admission was significantly lower in the scrub-typhus group than in patients with other infections (193% vs 376% of day 28 values, p=0.03). In four O. tsutsugamushi-infected patients HIV-1 RNA copy number fell by three-fold or more compared with day 28 values, and HIV-1 copy numbers were below the assay threshold in two patients with scrub typhus. Five of seven HIV-1 isolates from non-typhus patients with CD4 lymphocytes less than 200 cells/microL were syncytia-inducing variants, whereas all ten isolates from O. tsutsugamushi-infected individuals matched by CD4-cell count were non-syncytia inducing (p=0.03). Sera from an HIV-1-negative patient with scrub typhus had potent HIV-1-suppressive activity in vitro. Sera from typhus-infected mice inhibited HIV-1 syncytia formation and bound by immunofluorescence to HIV-1-infected lymphocytes.

INTERPRETATION

HIV-1-suppressive factors are produced during some scrub-typhus infection and should be investigated further in the search for novel strategies for the treatment and prevention of AIDS.