The HIV–AIDS virus, Ebola virus, genetic disorders and the common flu are some of the most common, and debilitating illnesses to gain a foothold in modern society, killing many individuals each year. However, there are some individuals that are imbued with natural immunity to these illnesses, which have long baffled scientists worldwide.

The immune system is both complex and individualised. Although researchers know that people have weakened immune systems if they suffer from chronic conditions, such as diabetes, or engage in poor habits, such as smoking, there is still little known about why some people never get sick.

“The most obvious reason … is simply that [they] are lucky,” says Stephen Morse, professor of epidemiology at Mailman School of Public Health at Columbia University.

“It’s likely due to a combination of ingredients,” says William Schaffner, professor of medicine in the division of infectious diseases at Vanderbilt University School of Medicine.

Schaffner, a widely respected epidemiologist adds that, “Some people are simply healthier than others,” and that “There are people who lead healthier lifestyles … they are less likely to become ill and it is a milder illness [when they do].”

HIV-AIDS

Some individuals are born with a mutation in the CCR5 gene, known as the CCR5 – delta 32 mutation, that renders them immune to HIV. This is due to the way HIV infects one body.

HIV infects the body via the CD4 receptor and its co-receptor CCR5, using them as a gateway for infection of the host, in this case being our body. In individuals gifted with such a mutation, HIV would be unable to infect its host as it requires the presence of the CCR5-delta 32 receptor, and without CCR5 on the surface of cells, HIV would not be able to infect and proliferate.

As a result, individuals with two copies of the CCR5-delta32 gene, inherited from both parents, are granted with virtual immunity to HIV infections. This occurs in about 1% of Caucasian people. However, this mutation is virtually absent in African and Asian populations.

Those with one copy of this mutation are granted some form of protection against infections; even if infection were to result, the resulting infection would be less severe. This more common infection is found in up to 20% of Caucasians.

However, further studies have shown that this is not a guarantee against contracting AIDS, and scientists are actively finding out how does resistance work in some individuals, identifying them and hopefully, a cure or vaccine can be developed from the findings.

In another research last August, scientists have discovered that cytotoxic T cells are able to find and eradicate the cells in which HIV would remain dormant in, potentially opening up a cure at long last for HIV–AIDS virus. The cytotoxic T cells are produced naturally in the body, but are not in abundance to counter HIV.

HIV has been tested positive in 36.7 million living individuals, and there are a total of 5,324 patients living with HIV in Singapore.

Ebola

In the Ebola outbreak in West Africa, it was discovered that a group of woman remained healthy despite exposures to Ebola, and in one remarkable case, one woman has Ebola antibodies despite no medical history of contracting Ebola.

The reasons for such immunity are yet unknown, but as Miles Carroll, Virologist and Head of Research at Public Health England’s national infection service, told The Guardian, "It may be that these people are genetically unique and have an innate response strong enough to fight Ebola before it can get a foothold (in one’s body).”

In fact, Ebola was recently found in a man’s sperm after 500 days, in what scientist suspect as a “Trojan Horse’ strategy for its own survival, and has reignited the alarm after 2014’s outbreak. It has a mortality rate of 90%, and was first identified in Africa in 1976.

Influenza virus

Vaccines that protect us from influenza are readily available and are usually recommended, but some individuals reported never developing flu despite not receiving the shots.

This revelation comes after a 2011 study of the science behind those with natural immunity to the flu, and found no symptoms of flu despite testing positive for infection. The study revealed significant and complex immune responses in those with immunity. In addition, researchers found changes in their blood up to 36 hours before their symptoms surfaced. However, the exact reason as to why and how some are immune to flu is yet unknown.

“People who are more socially connected in terms of positive relationships have fewer colds,” says Jon Temte, a University of Wisconsin health family medicine physician and chair of the Centres for Disease Control and Prevention's Advisory Committee on Immunisation Practices.

“They don’t just report fewer colds, they have fewer colds.” However, he adds that there are also others who contract viruses, but avoid experiencing illness themselves, which is known as an asymptomatic infection.

“We’re learning more and more about this group called super spreaders. These are people who are responsible for spreading [illness] but don’t get sick themselves,” says Temte. “I think the science behind that is basically in its infancy.”

Genetic diseases

Genes are passed on from parents to children, and two recessive copies of a gene, or a single dominant copy results in the traits being expressed. However, there are 13 unique individuals in the world who possess genetic mutations to some of the most crippling genetic diseases, such as cystic fibrosis, Smith-Lemli-Opitz syndrome, and familial dysautonomia but suffer from absolutely none of the symptoms.

This research comes from the analysis of data from 23andMe, the 1000 Genomes Project and Ontario Institute for Cancer Research. From the analysis of more than 580,000 healthy individual’s genome, a mere 13 participants tested positive for one of eight genetic diseases: cystic fibrosis, Smith-Lemli-Opitz syndrome, familial dysautonomia, epidermolysis bullosa simplex, Pfeiffer syndrome, autoimmune polyendocrinopathy syndrome, acampomelic campomelic dysplasia, and atelosteogenesis.

The reasons are yet unknown, but scientists hope that an understanding of why and how they are immune can provide hope for those who suffer from such debilitating diseases. MIMS

Read more:
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Discovery in high blood pressure gene mapping may provide means to a cure
Experimental Zika vaccines progress to clinical trials in humans

Sources:
http://www.medicaldaily.com/why-some-people-are-immune-hiv-ebola-and-other-diseases-397940
http://genetics.thetech.org/original_news/news13
http://www.iflscience.com/health-and-medicine/thirteen-people-identified-immune-genetic-diseases-researchers-cant-trace-them/
http://www.today.com/health/people-who-never-catch-cold-or-flu-it-luck-or-t2761
http://today.mims.com/topic/ebola-found-in-sperm-after-500-days-while-scientists-use--trojan-horse--strategy-to-target-virus?country=Malaysia&channel=GN-Health-Wellness
http://today.mims.com/topic/possible-new-mechanism-of-hiv-treatment-discovered?country=Malaysia&channel=GN-Policies-Public-Health