It does this by down-regulating the expression of CXCR4 on the surface of HIV target cells. M-tropic HIV-1 isolates that use only the CCR5 receptor are termed R5; those that use only CXCR4 are termed X4, and those that use both, X4R5. However, the use of co-receptors alone does not explain viral tropism, as not all R5 viruses are able to use CCR5 on macrophages for a productive infection and HIV can also infect a subtype of myeloid dendritic cells, which probably constitute a reservoir that maintains infection when CD4+ T cell numbers have declined to extremely low levels. Some people are resistant to certain strains of HIV. For example, people with the CCR5-Δ32 mutation are resistant to infection by the R5 virus, as the mutation leaves HIV unable to bind to this co-receptor, reducing its ability to infect target cells. Sexual intercourse is the major mode of HIV transmission. Both X4 and R5 HIV are present in the seminal fluid, which enables the virus to be transmitted from a male to his sexual partner. The virions can then infect numerous cellular targets and disseminate into the whole organism. However, a selection process leads to a predominant transmission of the R5 virus through this pathway. In patients infected with subtype B HIV-1, there is often a co-receptor switch in late-stage disease and T-tropic variants that can infect a variety of T cells through CXCR4.
The changes result in small opaque spots and areas of atrophy around the edges of the retina. These abnormalities usually do not affect vision but can be observed during an eye examination. Cause
Aceruloplasminemia is caused by a mutation (a five-base pair insertion in exon 7) in the CP gene, which provides instructions for making a protein called ceruloplasmin, a protein involved in iron transport and processing. Ceruloplasmin helps move iron from the organs and tissues of the body and prepares it for incorporation into a molecule called transferrin, which transports it to red blood cells to help carry oxygen. The CP gene mutation results in the production of ceruloplasmin protein that is unstable or nonfunctional by altering the open reading frame such that the amino acid ligands in the essential carboxyl terminal region are eliminated. When ceruloplasmin is unavailable, transport of iron out of the bodys tissues is impaired. The resulting iron accumulation damages cells in those tissues, leading to neurological dysfunction and other health problems.This condition is inherited in an autosomal recessive pattern, which means both copies of the gene have the mutation. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Diagnosis
Diagnosis of this disorder depends on blood tests demonstrating the absence of serum ceruloplasmin, combined with low serum copper concentration, low serum iron concentration, high serum ferritin concentration, or increased hepatic iron concentration.