In earlier episodes, you heard that trillions of viruses live peacefully, even beneficially, within each of us today.
And that our ancestors battled now-extinct “fossil viruses,” which are preserved in our own genetic code.
Turns out, that’s been beneficial too.
For instance, viruses helped drive our evolution.
100 million years ago, proto-mammals were infected with a virus that encoded into their DNA the ability to produce syncytin, a protein that viruses use to fuse cells together so they can move between them.
But these early mammals evolved to use this protein in a different way: to fuse the placenta to the uterus, allowing nutrients to pass from mother to fetus and making live birth possible.
Since humans diverged from apes, our proteins have adapted frequently to viral threats, even if they’re not part of the immune response. In fact, virus interactions now make up a third of all our protein adaptations.
Finally, researchers found that ancient viral DNA in our genetic code prompts a more vigorous response to new viral threats.
In experiments, when they removed fossil virus DNA from a cell, its immunity was severely weakened. Restoring the viral DNA restored the immune response.
While a rare few viruses have been quite harmful to humans, the vast majority—over millions of years—have helped us to become what we are and then to remain healthy.
Synopsis: Viruses evolve alongside their cellular hosts, but many orchestrate step changes in evolutionary lines as they cause their host organisms to evolve, leaving behinds bits of their genetic material in our genomes as clues.
- Recently, researchers applied big data analysis to paleovirology while working to determine the impact of viruses on the evolution of mammals, especially humans.
- They found that many proteins adapt to viral threats even if they are not involved in the immune system response, and that these virus-interactive proteins have been adapted three times as much as other proteins.
- In fact, a third of all adaptations to our proteins since humans diverged from apes have been driven by viruses.
- Other scientists have shown that some of the foreign genetic material in endogenous retroviruses (ERVs) may boost our immune systems, protecting us from other viruses.
- Humans have a two-part immune system.
- Our more primitive innate immune system provides a first line of defense, launching immediate responses in the presence of any foreign invaders.
- The adaptive immune system then learns to recognize specific invaders and respond with customized antibodies, T cells and B cells.
- Researchers looked for ERVs that could turn on the early innate immune response, and they found thousands. Removing these ERVs from the cell DNA produced a severely weakened immune response, whereas adding them back restored the original response. These ancient viral elements protected the cells against new infections.
- The human genome even carries some beneficial Neanderthal ERVs that assist our immune system response.
- Humans have a two-part immune system.
- Paleovirologists also study how viruses affect other mammals, like our close relatives the primates. For example, they seek to understand why apes are immune to some deadly human viruses like AIDS, and how that knowledge might help humans.
- They found a certain retrovirus fossil in apes but not in humans, and discovered humans have a gene that enables them to make a protein to protect them from the ancient retrovirus. Apes, however, were crushed by an epidemic.
- But while this gene saved us from the ancient retrovirus, it makes us vulnerable to HIV and AIDS today.
- Scientists are now working on strategies to develop a therapy focused on that human gene.
- A most astounding finding: Millions of years ago, ERVs may have been critical to the evolution of the placenta, which enables mammalian pregnancy and birth.
- More than 100 million years ago, a primitive mammal was infected with a virus that uploaded an ERV enabling the production of a protein called syncytin.
- Viruses use syncytin to fuse cells together so they can move between them.
- But mammals found a different use for it. Syncytin fuses the placenta to the uterus, allowing nutrients to be passed from the mother to her fetus and making live birth possible.
Katika vipindi vya awali, ulisikia kwamba trilioni za virusi zinaishi kwa amani, hata kwa manufaa, ndani ya kila mmoja wetu leo. Na kwamba mababu zetu walipigana na virusi vilivyoangamia sasa, ambavyo vimehifadhiwa katika nambari yetu ya urithi. Inageuka kuwa, hiyo pia imekuwa yenye manufaa. Kwa mfano, virusi vilisaidia kuongoza mageuzi yetu. Miaka milioni 100 iliyopita, proto-mamalia waliambukizwa virusi ambavyo vilitia ndani DNA yao uwezo wa kutengeneza syncytin, protini ambayo virusi hutumia kuunganisha seli pamoja ili waweze kusafiri kati yao. Lakini mamalia hao wa mapema walitengeneza protini hiyo kwa njia tofauti: kuunganisha placenta na tumbo la uzazi, na hivyo kuruhusu virutubisho vipite kutoka kwa mama hadi kwa kijusi na kufanya kuzaliwa kwa mtoto kuwepo. Tangu wanadamu walitengana na nyani, protini zetu zimebadilika mara nyingi kwa vitisho vya virusi, hata kama si sehemu ya majibu ya kinga. Kwa kweli, maingiliano ya virusi sasa hufanyiza thuluthi moja ya marekebisho yetu yote ya protini. "Hata hivyo, watafiti wamegundua kwamba DNA ya virusi vya kale katika msimbo wetu wa maumbile huchochea majibu ya nguvu zaidi kwa vitisho vipya vya virusi.""" Katika majaribio, walipoondoa DNA ya virusi vya visukuku kutoka kwa chembe, kinga yake ilidhoofika sana. Kurudisha DNA ya virusi kulirudisha majibu ya kinga. Ingawa virusi vichache vya kawaida vimekuwa hatari sana kwa wanadamu, vingi - kwa mamilioni ya miaka - vimetuwezesha kuwa kile tulicho na kisha kubaki wenye afya. Virusi huendelea pamoja na majeshi yao ya seli, lakini wengi huandaa mabadiliko ya hatua katika mistari ya mageuzi wakati wao husababisha viumbe vya majeshi yao kubadilika, wakiacha nyuma yao vipande vya nyenzo zao za maumbile katika genomes zetu kama vidokezo. Hivi karibuni, watafiti walitumia uchambuzi wa data kubwa kwa paleovirology wakati wa kufanya kazi kuamua athari za virusi kwenye mageuzi ya mamalia, haswa wanadamu. "Wanachunguza pia kwamba protini nyingi hujipatanisha na vitisho vya virusi hata kama hazihusiki katika majibu ya mfumo wa kinga, na kwamba protini hizi zinazohusiana na virusi zimebadilika mara tatu kuliko protini nyingine. """ Kwa kweli, theluthi moja ya marekebisho yote ya protini zetu tangu wanadamu kutofautiana na nyani yameongozwa na virusi. Wataalamu wa sayansi wameonyesha kwamba baadhi ya chembe za urithi za kigeni katika virusi vya ndani (ERVs) zinaweza kuimarisha mfumo wetu wa kinga, kutukinga na virusi vingine. - Wanadamu wana mfumo wa kinga wenye sehemu mbili. Mfumo wetu wa kinga wa asili wa primitive hutoa mstari wa kwanza wa ulinzi, kuanzisha majibu ya mara moja katika uwepo wa wavamizi wa kigeni. Mfumo wa kinga wa adaptive hujifunza kutambua wavamizi maalum na kujibu kwa antibodies zilizobadilishwa, chembe za T na chembe za B. Watafiti walichunguza virusi vya ERV ambavyo vinaweza kuamsha majibu ya kinga ya asili, na wakapata maelfu. Kuondoa virusi hivyo kutoka kwenye chembe za urithi (DNA) kunasababisha udhaifu mkubwa wa mfumo wa kinga, lakini kuviingiza tena kunarudisha athari ya awali. Vitu hivyo vya kale vya virusi vililinda chembe dhidi ya maambukizo mapya. - Genome ya binadamu hata hubeba baadhi ya Neanderthal ERVs manufaa ambayo kusaidia majibu ya mfumo wetu wa kinga. - Wanadamu wana mfumo wa kinga wenye sehemu mbili. - Wataalamu wa virusi vya kale pia huchunguza jinsi virusi vinavyoathiri mamalia wengine, kama vile jamaa zetu wa karibu, viumbe wanaoitwa primates. Kwa mfano, wanajaribu kuelewa kwa nini nyani hawana kinga dhidi ya virusi fulani vya kuua wanadamu kama vile Ukimwi, na jinsi ujuzi huo unavyoweza kuwasaidia wanadamu. "Wanafiti wamegundua kwamba ""retrovirus"" ya binadamu ina uwezo wa kutengeneza protini inayolinda dhidi ya virusi vya zamani." Hata hivyo, nyani waliangamizwa na tauni. Lakini wakati jeni hili lilituokoa kutoka kwa retrovirus ya kale, linatufanya tuwe dhaifu kwa HIV na Ukimwi leo. - Sasa wanasayansi wanafanya kazi juu ya mbinu za kutengeneza tiba inayozingatia jeni hilo la kibinadamu. Ugunduzi wa ajabu: Milioni ya miaka iliyopita, virusi vya ERV viliweza kuwa muhimu kwa mageuzi ya placenta, ambayo huwezesha mimba na kuzaliwa kwa mamalia. Zaidi ya miaka milioni 100 iliyopita, mnyama aliyetoka kwenye jamii ya primitive aliambukizwa virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi vya virusi. Virusi hutumia syncytin kuunganisha chembe pamoja ili ziweze kusonga kati yao. - Lakini mamalia walipata matumizi tofauti kwa ajili yake. Syncytin huunganisha placenta na tumbo la uzazi, ikiruhusu virutubisho kupitishwa kutoka kwa mama hadi kwa kijusi chake na kufanya kuzaliwa kwa uhai iwezekane.