text: On Sunday, Noah and Vera returned from their second trip to Santa Barbara with small samples of thymus tissue from the zoo's two lion cubs. As they drove south along the coast, Vera turned on the car's radio to hear the latest reports from Bakersfield. The migrating mice had reached the city and were entering buildings as they had in Taft. The US Army was furnishing helicopters to aid in the spraying of poison over the bands of mice, but such tactics could not be used in inhabited areas. One little girl had already died in Taft from eating poisoned grain.
  
  As he had done with the adult lion thymus sample, Gary isolated T-cells from the cub tissue and set them up in cell-culture dishes inside the biological safety cabinet. By the end of the week, the cells were thriving. Gary and Noah were ready to expose them to FHF-infected tissue. Gary opened the freezer and drew out a vial containing a piece of lymph node from a cat Vera had autopsied several months earlier. He thawed the sample and quickly pulverized it in a sterile glass tissue grinder. He then filtered the coral-colored soup and added small amounts to some of the lion-cub thymus-cell cultures.
  
  A few days later, Gary thought he saw evidence of cell degeneration. By Friday, there was no doubt; the cells were dying. He transferred a small portion of liquid from one of the infected cultures to a fresh, uninfected one. He removed his protective clothing and ran down the hall to Noah's office. Noah took one look at the glow in Gary's face and did not have to be told the news.
  
  He accompanied Gary to the lab. They put on the paper garments and entered. As he looked over the petri dishes, he didn't need a microscope to see the degeneration of T-cells. "Well," he said, "we've got to make sure it really is FHF."
  
  "What else could it be?" Gary asked.
  
  "It's probably FHF, Gary, but we can't take a chance of a screw-up. This is just too important."
  
  A week later, they had prepared a large quantity of the new FHF virus and had demonstrated that, although its chemical composition was similar to the common FHF virus, it was not identical. Where Felis catus FHF contained 68 percent protein, the lion virus had 71 percent. However, they looked alike under the electron microscope. The lion virus displayed the peculiar cartwheel appearance earlier characteristic of FHF that had been isolated from domestic cats. Noah speculated that the FHF viral genome had recombined with an endogenous lion virogene, a reversal of the process that Kraakmo had said was the origin of the FHF virus.
  
  The question remained whether the new virus, which could be grown in cell culture so easily, would act as an immunizing agent protecting cats against FHF. The odds were not good, considering the failure of FHF virus isolated from Felis catus to serve as an effective antigen.
  
  "Now just where are we going to get some cats with which to test this vaccine?" asked Noah.
  
  "There are some areas of the country where the epizootic hasn't yet been reported," Vera replied. "Northern New England, parts of Texas, Florida, in fact the southern US seems to be relatively free of FHF so far. Also, I hear that the CDC is maintaining a colony of virus-free cats in a kind of bubble room. No humans are allowed in, and all the air is filtered, food sterilized, that sort of thing."
  
  "Well then," Noah declared, "I think I'll put a call in to Kraakmo."
  
  Angelo confirmed that there was a fairly large, germ-free colony at the CDC, numbering about a hundred cats. He arranged for Noah to send a batch of the virus grown in lion cells, now called the FHF-L strain, to Atlanta for a trial immunization of twelve cats. They were transferred to separate quarters and injected with heat-inactivated virus at two-week intervals. By the second week of September, it was time to challenge them with virus, designated FHF-C, from domestic cats. The immunized cats were removed from their special quarters and placed in a colony of infected cats.
  
  Within a week, all the test cats had become infected with FHF, and, by mid-September, several of them had died. The scientists at the CDC then carried out a second trial, this time with living FHF-L virus. Like the first trial, it did not prove effective. Although the test cats did not become infected with FHF-L, the live lion virus vaccine failed to protect the cats against FHF-C. The lab technicians soon discovered why—antibodies to FHF-L cross-reacted only weakly with FHF-C.
  
  On a day in mid-September, Camarillo became superheated by Santa Ana winds rushing to the sea from the Mojave Desert. The fall semester had begun, and Noah, perusing his lecture notes, needed a break. He wandered down the hall to the lab. Alicia was preparing reagents, while Gary was hunched over his desk, writing. "Working on your thesis?" asked Noah.
  
  Gary, who had been engrossed, looked up, startled. "Yeah, what there is to work on."
  
  "It's okay, you know. Your work is sound. It's not your fault that you can't bring it to completion."
  
  "Yeah," said Gary without conviction. He leaned back, yawned audibly, and stretched. "If only there was some way to make a vaccine without that damned FHF virus..."
  
  Noah noticed an envelope on the desk addressed to the Molecular Biology Institute at UCLA. He picked it up and asked, "What's this?"
  
  "Oh, I've been thinking of applying for a post-doc with Fudderman."
  
  "Good idea. Might I recommend that you use one of the institute's envelopes rather than this one? It will make a better impression. The first thing Fudderman is going to see is the envelope, right?"
  
  "Yeah, I suppose so."
  
  Noah moved about the lab in a desultory fashion, putting glassware away in the cabinet, chatting with Alicia, and twiddling with various pieces of equipment. He reached up to adjust the temperature of an incubator. Gary continued writing. Suddenly Noah shouted, "The envelope!"
  
  Gary, startled again, said "Okay. I'll use an institute one."
  
  "No, I mean the FHF envelope. We don't need the purified virus—all we need is purified envelope proteins."
  
  Gary stared at him. Obviously, the outer proteins of the virus—the envelope—were the important ones needed for immunization. But how can you get purified envelope protein without isolating it from pure virus, he wondered. Immediately, he too saw the answer. All they had to do was to isolate the envelope genes from a sample of FHF-C virus, make DNA copies, and clone them in E. coli. With the system he and Noah had already developed for the MEFA work, they could get the bacteria to make all the envelope protein they needed. It was no problem at all to grow large quantities of E. coli. The CDC had enormous vats for that purpose.
  
  "Of course!" cried Gary, "We clone the envelope genes!"
  
  The two young scientists, mentor and student, gaped at one another. Neither was ready to admit the simplicity of the idea. After a long moment, Noah wondered aloud, "How could we have been so dense?"
  
  It was too late in the day to phone Atlanta, so Noah, overly stimulated and disinclined to continue with his lecture notes, phoned Vera to tell her of the plan. He explained to Vera how they would isolate and clone FHF-C envelope genes.
  
  "Sounds promising," she said.
  
  "It just seems so obvious," Noah remarked. "I don't know why we didn't think of this before."
  
  "Will this really do the trick, Noah? We're running out of time—or cats are, anyway."
  
  "I don't know. I hope so. If the envelope antigens don't succeed, maybe one of the other labs will come up with something. The CDC people are still working on it. So are the Russians and a group with the special pathogens branch of the Pasteur Institute."
  
  Noah phoned Angelo at the CDC. After Noah described his plan, Angelo replied with a hearty, "Marveloose! I will speak with Dr. Bronkowski about having some purified virus sent to you, and I will call you back in a little while. Will you stay by the phone please?"
  
  "You've got my cell phone number. I'll have it with me." This is great, he thought, Vera was right to get me involved with FHF. To think, I resisted.
  
  Angelo did, indeed, telephone back within the hour. "I am very sorry, Noah, Dr. Bronkowski will not allow the FHF-C virus to leave the laboratory. All work with it must be done in a BSL-4 lab. Your lab is not adequate. I am sorry. If you could come to Atlanta, we could have the work done here."
  
  Noah's euphoria vanished. "Oh, for God's sake, Angelo, what's the point of restricting FHF to BSL-4 conditions? There are so few cats left."
  
  "Well, we are afraid that the virus could change again. What if it acquired the ability to infect humans? A virus related to feline leukemia is found endogenously in baboons, you know. And, don't forget the Ebola part of FHF. We want to make sure that if the virus mutates into something even more dangerous, it doesn't get out of the lab. I think the boss is being reasonable."
  
  "But I have samples of the virus in my lab already!" Noah realized he was shouting into the phone. He lowered his voice. "We have a great many samples of infected tissue."
  
  "Yes, but that is not purified virus," replied Angelo in measured tones. "As you know, the purified virus is millions of times more concentrated than that in infected tissue. We cannot take any chances."
  
  "Angelo, the techniques required to clone the genes are complicated and need all sorts of specialized equipment."
  
  "So you think our labs are primitive? We have state-of-the-art facilities here, Noah. If there is some specialized equipment you need that we don't have, you can bring it with you. You write up the detailed protocols and what materials and equipment you need, and we'll work out the details by e-mail or telephone."
  
  Noah felt sick to his stomach at the new complication. "All right, all right," he said in a low voice, "I'll get started on it."